The collection of Nematomorpha in the Zoological Museum Hamburg, including description of a new species, Chordodes jelkae sp. n

The collection of horsehair worms in the Zoological Museum of the Centrum für Naturkunde (CeNak) of the University of Hamburg has been revised. All specimens have been investigated by Scanning Electron Microscopy (SEM). A total of 173 specimens from 135 catalogue entries is present in the collection, these represent 39 species from 10 genera (Gordius, Chordodes, Paragordius, Parachordodes, Gordionus, Acutogordius, Beatogordius, Paragordionus, Pseudochordodes, Nectonema). Previous revisions of the Nematomorpha material have been done in 1893 by Römer and in 1935 by Heinze. A number of species could not be determined to species level, either because characters were not preserved well enough or because observed characters did not fit available species descriptions. This does account in particular for the genus Gordius, where diagnostic characters are few and great uncertainties exist concerning the status of certain species. Therefore, within this genus, many records were only determined as Gordius sp., including some specimens that had previously been determined to species level. One new species is described from the material of the collection. This species is named Chordodes jelkae sp. n. and it is characterized by the presence of an apical tuft of bristles on simple areoles in combination with the absence of thorn areoles. The holotype of Chordodes pilosus Möbius, 1855 was reinvestigated, and its species identity cannot be determined unambiguously. Therefore the name Chordodes pilosus is considered a nomen dubium. Key Words


Introduction
The Zoological Museum Hamburg has a collection of 173 specimens from 135 catalogue entries of horsehair worms (Nematomorpha) representing 39 species from 10 genera.A total of about 455 species has been described from all over the world.Important for collection and determination are adult worms in their free-living phase (see Hanelt et al. 2005 and Schmidt-Rhaesa 2013 for recent summaries on the life cycle and other topics), because these are encountered most often and because the cuticle has structures that are relevant for determination.The parasitic juveniles are almost impossible to determine, because they show a different cuticle that does not contain differential structures (see, e.g., Schmidt-Rhaesa 2005).
The only published review of the collection of the Zoological Museum Hamburg is from Römer (1895).He investigated material that was included in the registry catalogue as numbers V2206 to V2234 (without giving these accession numbers in the publication).These are 29 catalogue numbers from 11 species of Gordius and Chordodes, the only genera available by that time.According to recent systematics, Römer's 10 species belong to four genera: Gordius, Gordionus, Parachordodes and Chordodes.The material of three numbers (V2206, 2210, 2219) was lost (noticed by a revision in 1954).Six numbers (V2209-V2212, 2232, V2234) turned out to be mermithid nematodes, among these are two species that were newly described (as nematomorphs) by Römer (1895): Chordodes liguligerus Römer, 1895 (see Heinze 1935a) and C. hamatus.The latter species was later renamed Gordiomermis hamatus (Heinze 1934).
In 1935, Kurt Heinze from Berlin worked on the Hamburg collection and determined a number of specimens, a few of these results were published in Heinze (1935a).The collecting localities of several Hamburg specimens occurred in Heinze's summaries of German Nematomorpha from 1937 and1941.Since then, nobody has reviewed the material or deposited new type material until from 2008 on the author deposited several types in the collection.
It is the aim of this summary on the one hand to present an overview of the Nematomorpha material in the Hamburg collection and on the other hand to determine all material according to current standards.This includes investigation by Scanning Electron Microscopy (SEM).The SEM reinvestigation led to several new determinations, in particular a number of determinations at the species level could not be confirmed and hence are treated here as "sp.".

Material and methods
Specimens are conserved in ethanol with a desired concentration of 70%.For the reinvestigation, entire pieces from the midbody region and in some cases the posterior end (about 1-2 mm from the terminal tip) were prepared for Scanning Electron Microscopy (SEM).Pieces were dehydrated in an increasing ethanol series, critically point dried and coated with gold in a sputter coater.Observation took place using a LEO SEM 1524 at 10 kV.Digital images were taken.

Results and discussion
In the Zoological Museum Hamburg, entries are recorded in a catalogue book, printed as a record card and recorded digitally in a Filemaker file.Entries in the catalogue are hand-written and could not always be read reliably.It was attempted to verify the collection localities, but this was not possible in all cases.Writing of names is given here as good as possible.Citations from the catalogue are given in quotation marks.The main focus is on the older records, which are reinvestigated.Younger records, which are well documented in the literature, are presented only briefly, with reference to the respective publications.

Genus Acutogordius Heinze, 1952
Males in species of Acutogordius have a postcloacal crescent, like in Gordius, but the tail lobes are pointed and the entire posterior end tapers towards the pointed tip of the tail lobes (Fig. 7D, G, J).Nine species have been described.The distribution of fine bristles in the male anterior end appears to be important for species delimitation, but such fine bristles were not always reported in older descriptions.See Schmidt-Rhaesa and Geraci (2006) for a summary.not be determined with certainty if these are really cuticular structures (Fig. 7I).Otherwise the cuticle is smooth (Fig. 7H).As bristles are absent on the posterior end, the specimen is closest to the description of A. acuminatus De Miralles & De Villalobos, 1998(see above and De Miralles and De Villalobos 1998, Schmidt-Rhaesa and Geraci 2006).

Genus Beatogordius Heinze, 1934
Characteristic for this genus, which currently includes 21 species (Schmidt-Rhaesa 2013), is that areoles are arranged in longitudinal rows.Two specimens of the collection belong to Beatogordius, among them the holotype of the most recently described species in this genus.
Remarks from the catalogue.collected by R. Paeseler on October 5, 1914.Received by the museum on January 15, 1920.Originally determined as "Gordiide".
Occurs in publications.unknown Remarks.The cuticle is not very well preserved and strongly covered with dirt.Paired elongate areoles arranged in longitudinal rows can be well observed (Fig. 9A), but interareolar structures were not seen.This is characteristic for the genus Beatogordius and resembles patterns found especially in B. latastei (De Villalobos et al. 2003).The posterior end has short, probably broken, spines around the cloacal opening (Fig. 9B) and postcloacal spines, which extend from posterior of the cloacal opening onto about half of the ventral side of the tail lobes (Fig. 9C).In the anterior region they are stout and gradually become more slender in the posterior region (Fig. 9D).Precloacal bristles were not observed (Fig. 9C), but it cannot be excluded that they were artificially eroded or covered by dirt.Males of all South American species have clear precloacal rows of bristles (De Villalobos et al. 2003).
Location.Chile, Limache (writing is not explicit), in river.
Remarks from the catalogue.collected by D.C. Bock (date not given).Received by the museum on July 9, 1923.Originally determined as "Gordiide" Occurs in publications.unknown Remarks.The cuticle of this specimen shows longitudinal rows of paired, elongate areoles, which is characteristic for the genus Beatogordius (Fig. 8I, J).There is closest resemblance to B. latastei (Camerano, 1895) (compare De Villalobos et al. 2003), but for a proper determination the cuticular structures in the interareolar region should be checked, which are not seen clearly due to some covering of dirt between areoles in specimen V9575.

Chordodes
Remarks.This specimen is the holotype for the species Chordodes pilosus, described by Möbius in 1855.The genus Chordodes had been introduced briefly before (Creplin 1847), and the main reason to distinguish this genus from Gordius was the abundant presence of marked areoles.Römer (1895, 1896) reinvestigated the specimen, but without going much further than Möbius' original description.The descriptions were not detailed enough to allow a distinction from the several new species that were described towards the end of the 19 th century, and Camerano (1897) listed C. pilosus under species inquirendae.Later, Heinze (1935a) reinvestigated the specimen again and added some information on the cuticle.The current reinvestigation by SEM shows that crowned areoles, the diagnostic character of the genus Chordodes, are present on the cuticle (Fig. 12C-G).Crowned areoles are arranged in clusters, surrounded by circumcluster areoles (Fig. 12F).Simple and tubercle areoles are present.All areoles are very bad in shape and appear worn or eroded, especially the filaments of the crowned areoles (Fig. 12E-G).Nevertheless it can be seen that crowned areoles Descsription.The two females measure 90 (I) and 85 (II) mm in length and 0.9/1.0mm in diameter, respectively.The anterior end tapers towards the tip.The body colour is a dark brown general occurrence, with brown basic colour and darker patches (the "leopard pattern").The anterior tip is white and blends into the brown body colour.Specimen (I) is well preserved, characters of specimen (II) are less well visible (Fig. 15F).The following description is therefore based on specimen (I), which is designated as the holotype.The cuticle shows the characteristic types of areoles known from other species of Chordodes.The simple areoles are roundish, often longer than broad (Fig. 15C, E).Their longer axis is perpendicular to the longitudinal axis of the animal.Simple areoles are closely together (Fig. 15C, E).On the apical side they have a tuft of short (about 3µm) bristles (Fig. 15C-E), in some cases these fine bristles are dissolved and do not form a clear tuft.Among the simple areoles are occasional tubercle areoles, the tubercle is in some cases pointed (Fig. 15E).Thorn areoles were not observed.Crowned areole clusters are composed of two central crowned areoles with moderately long apical filaments (< 20 µm), which are surrounded by 10-12 circumcluster areoles (Fig. 15C).The apical filaments of the crowned areoles originate laterally around a more or less flat apical surface of the areole, this surface is divided by several grooves into several compartments (Fig. 15C).The apical filaments may divide basally, but more distal divisions were not observed.The circumcluster areoles have a tuft of bristles on top (Fig. 15C).This tuft varies in its form, it either resembles the tuft of simple areoles as all bristles originate in the center of the apical surface or, in some circumcluster areoles, the apical surface is flat and the bristles extend laterally, comparable (though shorter) than in crowned areoles (Fig. 15C).Along one longitudinal line, probably the ventral midline, crowned areoles have very long apical filaments (approximately 170 µm) (Fig. 15B), in contrast to crowned areoles in the remaining parts of the body, which have shorter apical filaments (Fig. 15A).
Remarks.Species of Chordodes are quite similar in their cuticular structure.Species are distinguished by the presence or absence of particular types of areoles or when cuticular structures exhibit a particular substructure.Characteristic for this new species is the form of the simple areoles.In most species of Chordodes the simple areoles have either no bristles or scattered fine bristles on their apical surface.SEM investigations reveal that small bristles may be more abundant than known on the basis of traditional light microscopical investigation and they may even form small tuft-like structures as present, e.g. in C. parabipilus Kintsurashvili, Schmidt-Rhaesa & Gorgadze, 2011(Kintsurashvili et al. 2011), C. moutoni Camerano, 1895(Schmidt-Rhaesa and Yadav 2013) and C. combiareolatus Schmidt-Rhaesa, Limatemjen & Yadav, 2015(Schmidt-Rhaesa et al. 2015).Compared to these species, the tuft of bristles is larger in C. jelkae sp.n.A distinct tuft of bristles is present in C. villalobi, a species from Malaysia (Schmidt-Rhaesa and Brune 2008), but this is more pronounced than in C. jelkae sp.n. .In combination to the shape of the tuft of bristles on the simple areoles, an important difference between all mentioned species and C. jelkae sp.n. is that thorn areoles are absent in C. jelkae sp.n., but present in all other species.Additinally, simple areoles are closer together in C. jelkae sp.n. than in C. villalobi.Characters in specimen 10960 (II) are not as well visible and its assignment to C. jelkae sp.n. is likely, but not certain.

Genus Gordionus Müller, 1926
The genus Gordionus is characterized by the following character combination: one type of areoles present on the cuticle, male posterior end with bristles anterolateral of the cloacal opening and spines posterior of the cloacal opening and directly around it.Currently, 56 species are included in this genus (Schmidt-Rhaesa 2013), but it is currently not well understood, whether these species are real, because the amount of character variation is not clear.There is a broad range of minute cuticular differences between Gordionus specimens and it was suspected that such a range reflects intraspecific variability.This was for example made probable for the species G. violaceus and G. wolterstorffii, which, although having quite dissimilar cuticular patterns, are connected by a range intermediate cuticular patterns (Schmidt-Rhaesa 2001).Unpublished molecular results (COI-gene) support that there are two species, one (G.violaceus) with one typical cuticular pattern and another (G.wolterstorffii) with a variable cuticular pattern.This would mean that some species descriptions (see, e.g., Heinze 1941) fall into the range of cuticular variation of G. wolterstorffii.This does, for example, account to G. scaber, of which some specimens in the collection have been determined.Because the mentioned molecular results have not been published yet, I decide here to retain the determination as G. scaber, when specimens correspond to the character description as given by Müller (1926) and Heinze (1937Heinze ( , 1941)).
Remarks from the catalogue.Collected by "Fischer" (no collection date or date when received by the museum given).Carabus smaragdinus is given as host.Determined by Römer in 1895 and Heinze in 1935 as male of Gordius aquaticus.
Remarks.Presently, the vial contains four specimens: three females, of which one was investigated here by SEM and one specimen in an extra vial, this specimen is lacking the posterior end.According to the catalogue the number of specimens should be 2 and the determination says "Gordius aquaticus ♂".Römer (1895) mentions 2 males and 4 females from this locality and this host, therefore it remains unknown, how many specimens were included in this vial originally.The potential host is the beetle Carabus smaragdinus.It is not mentioned, whether all specimens originate from the one host and the host is not included in the vial.Additionally, the beetle was probably not determined correctly, as C. smaragdinus is not an African species (according to Wikipedia).The cuticle contains polygonal areoles (Fig. 9E) that are clearly separated from each other and therefore it is most likely that this specimen belongs to the genus Gordionus.Material examined.V2217 (according to catalogue 3 males, only 1 male found in vial).Fig. 9F-H Heinze 1941).Von Siebold (1848) did not really describe this species, but writes about a horsehair worm emerging from Molops elatus: "it possesses a slight longitudinal furrow at the posterior end, therefore I will call it … Gordius subbifurcus".According to the catalogue, the worm(s) of number V2217 are the type material of Gordius subbifurcus, but I regard this as not likely.First, neither in the vial, nor in the catalogue, it is marked as type material.Second, according to the catalogue, Von Siebold collected the material himself from an undetermined carabid beetle.In Von Siebold's 1848 publication he mentions G. subbifurcus twice, first from Molops elatus sent by Prof. Fuchs and second from Calathus cisteloides from the helminthological collection in Freiburg.Both these reports do not correspond to the data given in the Hamburg catalogue.
Finally, the determination as Parachordodes tolosanus could not be supported here.The genus Parachordodes has two types of areoles, one of which are the so-called superareoles (see, e.g., Schmidt-Rhaesa 2013).The SEM investigation showed only one type of areoles (Fig. 9F), therefore this specimen likely belongs to the genus Gordionus.The posterior end shows a row of precloacal bristles that is continuous anterior of the cloacal opening and not divided into two lateral rows.This single character has been taken to name a new genus, Semigordionus (Heinze 1952), with one species from Austria.Zanca and Schmidt-Rhaesa (2006) found it more appropriate to regard Semigordionus as a member of the genus Gordionus, but did not formalize this step, because further investigations of the posterior end of S. circumannulatus should be awaited.Occurs in publications (as P. tolosanus).Heinze (1937, page 285), Heinze (1941, page 24).

Material
Remarks.Only one type of areoles is present (Fig. 9I), no superareoles could be found.Therefore the specimen is determined as Gordionus sp.As the catalogue indicates only one specimen, it is unknown whether this second specimen does belong to the vial originally.If it does, it is unknown whether both specimens emerged from the beetle.
Location.Macedonia, stream to river Vardar, close to Veles (as "Bach zum Vardoe, N. v. Veles") Remarks from the catalogue.collected by F. Ahlborn in 1916 (date not given).Received by the museum on November 22, 1923.Originally determined as "Gordius".
Occurs in publications.unknown Remarks.The cuticle of both specimens has roundish areoles surrounded by a broad and flat interareolar space, in which interareolar bristles are present (Fig. 9J, K).This somewhat resembles G. violaceus, but in that species the interareolar furrows are not so broad.Specimens V9615 cannot be assigned to a species of Gordionus with certainty.
Remarks from the catalogue.collected by Niggemeyer (no date given).Received by the museum on May 16, 1936.Determined by Thiel in 1936 as Gordius aquaticus.
Occurs in publications.unknown Remarks.The posterior end of this specimen is unfortunately lost during preparation for SEM, but notes taken before the loss indicate that a postcloacal crescent is absent.The cuticle has one type of areoles (Fig. 10A), it is possible that this specimen belongs to G. violaceus, but preservation is not good enough for a certain determination.
Remarks from the catalogue.Collected by Takuya Sato on September 12, 2008.Received by the museum in 2011.
Occurs in publications.Sato et al. (2012) Remarks.Specimen is a voucher for a phylogenetic analysis in Sato et al. (2012).
Remarks from the catalogue.Collected by Takuya Sato on September 29, 2008.Received by the museum in 2011.
Occurs in publications.Sato et al. (2012) Remarks.Specimen is a voucher for a phylogenetic analysis in Sato et al. (2012).
Remarks from the catalogue.Collected by Takuya Sato on September 14, 2009.Received by the museum in 2011.
Occurs in publications.Sato et al. (2012) Remarks.Specimen is a voucher for a phylogenetic analysis in Sato et al. (2012).
Remarks from the catalogue.Collected by Takuya Sato on September 14, 2009.Received by the museum in 2011.
Occurs in publications.Sato et al. (2012) Remarks.Specimen is a voucher for a phylogenetic analysis in Sato et al. (2012).
Remarks from the catalogue.Collected by Schlotthauber (no collection date or date when received by the museum given).Determined by Römer in 1893 as Gordius violaceus, corrected by Heinze in 1935 to Parachordodes tolosanus.
Remarks.SEM reinvestigation showed that the female does not have superareoles as required for the original determination as P. tolosanus.Because it has only one type of areoles (Fig. 10B), it is designed as Gordionus sp.The specimen was formerly included in a lot of five worms under the number V2220.Occurs in publications.Römer (1895, page 794), briefly in Heinze (1937, page 302), Heinze (1941, page 45).
Remarks.SEM reinvestigation shows partly fused areoles (Fig. 10C), consistent with patterns found in the character range of G. wolterstorffii (see Schmidt-Rhaesa 2001).Gordionus meissneri, to which the specimen was originally assigned, has isolated areoles that are not fused to short rows as in V13362 (see, e.g., Heinze 1941).The specimen was formerly included in a lot with another male worms (determined as G. violaceus) under the number V2225.
Remarks from the catalogue.Collected by Valeria Viktoria Gusich in 2008.
Remarks.Holotype for this species.See Schmidt-Rhaesa and Gusich ( 2010) for all information about this specimen.
Remarks from the catalogue.Collected by J. Fresneda, I. Ribera and A. Cieslak on August 2, 2006.Received by the museum on July 3, 2008.
Remarks.Holotype of this species.See Schmidt-Rhaesa and Cieslak ( 2008) for all information about this specimen.
Remarks from the catalogue.Collected by Takuya Sato in 2007.Received by the museum on May 20, 2008.
Remarks.see Schmidt-Rhaesa and Sato (2009) for all information about this specimen.
Remarks from the catalogue.Collected by Takuya Sato on September 13, 2008.Received by the museum in 2011.
Occurs in publications.Sato et al. (2012) Remarks.Specimen is a voucher for a phylogenetic analysis in Sato et al. (2012).
Remarks from the catalogue.Collected by Takuya Sato on September 12, 2008.Received by the museum in 2011.
Occurs in publications.Sato et al. (2012) Remarks.Specimen is a voucher for a phylogenetic analysis in Sato et al. (2012).
Remarks from the catalogue.Collected by Takuya Sato on September 29, 2008.Received by the museum in 2011.
Occurs in publications.Sato et al. (2012) Remarks.Specimen is a voucher for a phylogenetic analysis in Sato et al. (2012).
Remarks from the catalogue.Collected by Takuya Sato on October 13, 2010.Received by the museum in 2011.
Occurs in publications.Sato et al. (2012) Remarks.Specimen is a voucher for a phylogenetic analysis in Sato et al. (2012).
Remarks from the catalogue.Collected by Takuya Sato on October 13, 2010.Received by the museum in 2011.
Occurs in publications.Sato et al. (2012) Remarks.Specimen is a voucher for a phylogenetic analysis in Sato et al. (2012).
Remarks from the catalogue.Collected by Takuya Sato on October 13, 2010.Received by the museum in 2011.
Occurs in publications.Sato et al. (2012) Remarks.Specimen is a voucher for a phylogenetic analysis in Sato et al. (2012).Occurs in publications.Schmidt-Rhaesa and Sato (2009).
Remarks from the catalogue.Collected by Thalenhorst (no collection date or date when received by the museum given).Determined by Römer in 1893 as Gordius violaceus and by Heinze in 1935 as Gordionus scaber (s.str.).
Remarks.Although not optimally preserved, it is evident that the areoles are isolated or partly fused in short rows (Fig. 10D), which corresponds to the description of Gordionus scaber scaber (see, e.g., Heinze 1941).
Remarks from the catalogue.Collected by F. Richter (date not given).Received by the museum on June 29, 1929.Determined by Heinze in 1935 as Gordionus scaber.
Remarks.The cuticle shows roundish areoles with an individual character, but which are partly fused with neighbouring areoles in longitudinal direction (not figured).This is consistent with the pattern described for Gordionus scaber (e.g., Heinze 1941).The posterior end has, as far as can be observed, unbranched precloacal bristles (Fig. 10F, H), but these are covered with some dirt and a potential fine branching, as is described by, e.g., Heinze (1941) for G. scaber, could not be excluded with certainty.Therefore, Heinze's determination as G. scaber is confirmed here with the additional remark that this may fall into the range of characters for a polymorphic species G. wolterstorffii.Occurs in publications.Schmidt-Rhaesa and Cieslak (2008).

Gordionus turkensis
Remarks.Holotype of this species.See Schmidt-Rhaesa and Cieslak ( 2008) for all information about this specimen.
Remarks.SEM reinvestigation shows one type of areoles surrounded by interareolar bristles (Fig. 10I), therefore the determination as G. violaceus is supported.
Material examined.V11455 (2 females).Fig. 10K, L Occurs in publications.unknown.Heinze (1937Heinze ( , 1941) ) mentions Rügen as location for G. violaceus, but with addition "Stubbnitz", which is not given in the catalogue.Therefore this may be a different specimen.
Remarks from the catalogue.Collected by Schlotthauber (no collection date or date when received by the museum given).Determined by Römer in 1893 as Gordius tolosanus, corrected to Gordionus scaber scaber by Heinze in 1935.
Remarks.Collector and collection dates are similar to V2220 determined as Parachordodes tolosanus.The cuticle shows irregular rows of fused areoles (Fig. 11A).According to Heinze (1941) Gordius scaber scaber has isolated areoles or areoles are fused to short rows, but the individual character of areoles remains visible.Such description does not correspond to the pattern observed in specimen V2218 by SEM.The long fused rows of areoles correspond to the description given for Gordionus scaber lineatus (e.g., in Heinze 1941), but also correspond to the description of G. wolterstorffii (Camerano, 1888) (see, e.g., Schmidt-Rhaesa 2001).
Material examined.V2222 (in the catalogue 5 males and 2 females are indicated, presently only 1 male is present).Fig. 11B, D.
Remarks from the catalogue.Collected by Dömling (no date given).Received by the museum on September 23, 1893.Determined by Römer in 1893 as Gordius violaceus and by Heinze in 1935 as Gordionus scaber.
Remarks from the catalogue.Collected by Wiebelitz (no date given).Received by the museum on June 14, 1899.Determined by Heinze in 1935 as Gordionus scaber.
Occurs in publications.unknown Remarks.The cuticle shows irregular rows of fused areoles (Fig. 11C).As described above (V2218), this is characteristic for G. wolterstorffii rather than for G. scaber.

Genus Gordius Linné, 1758
Species of the genus Gordius are not easy to determine due to their scarceness of diagnostic characters, especially in female worms.Additionally, the range of intraspecific variation for several characters is not known (Schmidt-Rhaesa 2010).Finally, fine structural characters such as the presence and distribution of fine bristles have been observed only with SEM, but are not reported in older species descriptions (see Schmidt-Rhaesa 2010).
Characteristic for the genus is the presence of a semicircular or parabolic cuticular fold posterior of the ventral cloacal opening, which is called the postcloacal crescent.Posterior of this structure, the body is divided into paired lateral tail lobes.In Gordius, the tail lobes are rounded, in contrast to the genus Acutogordius, which has pointed tail lobes and is the only other genus with a postcloacal crescent (see below).In females, there is no difference to females of other genera, therefore females are more difficult to assign.The body cuticle in Gordius specimens can be either smooth or ornamented with roundish or polygonal structures called areoles.Areoles are present in other genera, too, especially in Gordionus.A smooth cuticle is only present in Gordius, but it has been described from several species (15 European species according to Schmidt-Rhaesa 2010).Therefore, a smooth cuticle indicates that the specimen belongs to Gordius, but it is not indicative for a certain species.Most species can only be determined with the help of certain structures, mostly bristles, on the male posterior end.In worn or dirty specimens such characters may not be visible, therefore determination requires some caution.This is the reason that in this reinvestigation a number of determinations to species level are changed to Gordius sp.
Remarks.In Gordius muelleri Heinze, 1933 (writing in catalogue mülleri) there is some distance between the postcloacal crescent and the beginning of the bifurcation of the tail lobes (see Heinze 1933Heinze , 1937Heinze , 1941)).As in the present specimen the postcloacal crescent is directly at the point of bifurcation (Fig. 1A), the determination as G. muelleri cannot be confirmed.
Remarks.The cuticle is, in the investigated part, covered with material of unknown nature (Fig. 1C).The polygonal areoles, characteristic for G. albopunctatus (see, e.g.Schmidt-Rhaesa and Kristensen 2006) could not be observed and, therefore, the specimens are regarded here as Gordius sp.Remarks.Female worm with smooth cuticle (Fig. 1D), which occurs only in some species of Gordius.As Gordius aquaticus is restricted to the Palaearctic, hence this is probably another species of Gordius, such as G. robustus, but this cannot be determined with a female specimen.
Material examined.V2223 (in the catalogue 1 male and 1 female are mentioned, currently two fragments are present, from which at least one is from the male).Fig. 1F, G.
Remarks from the catalogue.Collector unknown, no date given.Date when received by the museum not given.Determined by Römer in 1893 as Gordius violaceus and by Heinze in 1935 as Gordius mülleri.
Remarks.The SEM reinvestigation shows a slight pattern of areoles on the cuticle (Fig. 1F).The cloacal opening, which should be oval in G. muelleri (see, e.g., Heinze 1941) is covered and not visible (Fig. 1G).The tail lobes of specimen V2223 are about twice as long as they are broad and not as short as they should be in G. muelleri (see, e.g., Heinze 1941).Therefore, the determination as G. muelleri is regarded as questionable.Remarks.Gordius aeneus is regarded an invalid species name (Schmidt-Rhaesa 2013).SEM investigation of specimen V2227 shows a smooth cuticular surface (Fig. 1H), therefore an assignment to the genus Gordius is certain, but a concrete species cannot be determined.
Remarks from the catalogue.Collector unknown.No collection date or date when received by the museum given.Determined by Römer in 1893 as Gordius fulgur, determination confirmed by Heinze in 1935.Occurs in publications.Römer (1895, page 795), briefly in Römer (1896, page 267).
Remarks.SEM investigation of specimen V2228 shows a smooth cuticular surface (Fig. 2A), therefore an assignment to the genus Gordius is certain, but a concrete species cannot be determined.Therefore, the original determination as G. fulgur was changed to Gordius sp.
Remarks from the catalogue.Collected by Stuhlmann.No collection date or date when received by the museum given.Determined first as Gordius aquaticus, but "aquaticus" was later crossed out.No name of reviser is given.Worm found in an undetermined cricket.
Occurs in publications.unknown Remarks.The worm is still inside the cricket, some loops of it are visible through an injury in the anterior part of the abdomen.Body ends were not removed, and a sex determination is therefore not possible.A piece of worm was removed from the outermost loop.The cuticle is smooth (Fig. 2B), therefore it is likely that this is a Gordius specimen.
Remarks from the catalogue.Collected by H. Sauter (no date given), received by the museum on April 22, 1908.Originally determined as "Chordodes".
Occurs in publications.unknown Remarks.SEM investigation reveals a smooth cuticle (Fig. 2C), therefore the specimen belongs to the genus Gordius.
Remarks from the catalogue.Collected by Dr. Alb.Graser (no date given), received by the museum on July 12, 1909.Host: a cricket.
Occurs in publications.unknown.
Remarks.The cuticle is smooth, but contains small keel-like structures perpendicular to the longitudinal body axis (Fig. 2D).These structures are unknown from species of Gordius.
Remarks from the catalogue.Collected by "W.Fischer" (date not given).Received by the museum on October 1, 1896, determined as "Gordiide".
Occurs in publications.unknown Remarks.The cuticle contains shallow areoles with polygonal or irregular outline (Fig. 2E).The postcloacal crescent borders the point of bifurcation of the two tail lobes, it is short and semicircular and extends slightly onto the tail lobes (Fig. 2F).Most of these characters fit to the description of G. undulatus as given by Heinze (1937), with the exception that in this species, there is a distance between the postcloacal crescent and the point of bifurcation of the tail lobes.With the exception of G. digitatus, which has strongly interdigitating areoles (see Schmidt-Rhaesa 2010), G. undulatus is the only species with areoles of an irregular shape.Therefore a definitive determination can currently not be given.
Remarks from the catalogue.Collected by Lenz on July 27, 1897.Received by the museum on August 11, 1897.Originally determined as "Gordiide".

Occurs in publications. unknown
Remarks.The specimen has a smooth cuticle (Fig. 2G), but because the posterior end is missing, no further determination can be given.
Remarks from the catalogue.Collected by Timm (no date given), received by the museum on August 21, 1897.Determined as "Gordius".
Occurs in publications.unknown Remarks.Both specimens differ in their cuticular structure, which may indicate that they belong to different species.The female has a smooth cuticle (not figured), while the cuticle of the male has elongate areoles that are partly confluent with neighbouring ones and that are arranged perpendicular to the longitudinal body axis (Fig. 2H, I).This cuticular structure does match best, though not exactly, the description for G. tirolensis Heinze, 1937, a species described from Austria (Susalitsch, Kärnten) and also from South Tyrol (Brixen) (Heinze 1937(Heinze , 1941)).The posterior end contains a large postcloacal crescent that has a short distance to the cloacal opening and extends well onto the comparably long tail lobes (length to width slightly > 2:1) (Fig. 2J).The postcloacal crescent is angled.Around the cloacal opening, bordered posteriorly by the postcloacal crescent, there is a depressed area that is bordered by a fringed rim (Fig. 2K).The exact nature of this structure could not be detected, but it does not seem to be a row of bristles as is present in some (non-European) species such as G. paranensis (see below and Schmidt-Rhaesa et al. 2000) or G. attoni (see, e.g., Schmidt-Rhaesa et al. 2003).The description of the posterior end does not fit G. tirolensis (Heinze 1937(Heinze , 1941) ) and therefore V4611 is treated here as Gordius sp.
Remarks from the catalogue.Collected by Ansorge (no date given), received by the museum on November 19, 1897.Determined by Heinze in 1935 as G. aquaticus.
Remarks.The SEM reinvestigation shows a smooth cuticle (Fig. 3A) and some short bristles on the inner side of the tail lobes (Fig. 3B, C).As it is not clear whether such bristles are present in G. aquaticus (compare Schmidt-Rhaesa 2010), the specimen is referred to here as Gordius sp.

Occurs in publications. unknown
Remarks.The cuticle is smooth, but has some fungus-like covering (Fig. 3D), the determination is not possible with certainty.
Remarks from the catalogue.Collected by A. Westphalen (no date given).Received by the museum on April 26, 1900.Determined by Heinze in 1935 as Gordius mülleri.
Occurs in publications.Heinze (1937, page 320), Heinze (1941, page 59) Remarks.The cuticle does not contain areoles (Fig. 3E).The posterior end is in bad shape, the postcloacal crescent is directly at the point of bifurcation of the tail lobes (Fig. 3F).As explained for specimen V2207, this argues against a determination as G. muelleri.
Remarks from the catalogue.Collected by Ilse Schultze (date not given).Received by the museum on September 15, 1900.Determined by Heinze in 1935/36 as "Gordius ?aquaticus".
Remarks.The cuticle of this specimen is smooth (Fig. 3G), therefore no further determination can be given.
Remarks from the catalogue.Collected by "Lehrer" (teacher ?)Wagner (date unknown).Received by the museum on July 2, 1901.Determined by Heinze in 1935 as
Remarks.The body cuticle is heavily covered with some artificial crust (Fig. 3H), therefore it could not be determined with certainty, whether areoles are present or not.The posterior end is clearer, but does not correspond to the descriptions given for G. muelleri (e.g. in Heinze 1941), because the postcloacal crescent is directly on the point of bifurcation of the tail lobes in V5773 (Fig. 3I) and not, as in G. muelleri, in some distance from it.Occurs in publications.Heinze (1941, page 71) (not in Heinze 1937) Remarks.The cuticle is smooth with some irregularly placed shallow elevations (Fig. 3J).Star-like structures on the cuticle as described for G. stellatus are likely artificial (Heinze 1937) and it is not clear whether this species is valid or not (e.g.Schmidt-Rhaesa 1997).This reinvestigation cannot assign the specimen to any species of Gordius with certainty.

Material examined. V6341 (1 female).
Material examined.V6488 (1 male).Fig. 3K-M Occurs in publications.Heinze (1937, page 316), Heinze (1941, page 58) Remarks.The cuticle has very indistinct elevations that might represent areoles (Fig. 3K).The entire cuticle has a fine striation (Fig. 3L).The posterior end has some fine bristles on the inner side of the tail lobes.The postcloacal crescent is narrow and semicircular, it extends onto the tail lobes (Fig. 3M).The current characters do not fit to a certain species of Gordius, but are regarded not significant enough to consider this a new species, therefore the specimen is determined as Gordius sp. .Heinze's determination as G. setiger might be based on the presence of areoles, however, the elevtions are so slight that it is not sure whether these can really be called areoles.

Material examined. V6826
(2 males and one specimen of unknown sex, posterior end is missing).Fig. 4A, B.
Remarks from the catalogue.Collected by "Cons.G. Siemssen" (no date given).Received by the museum on April 4, 1906.
Occurs in publications.unknown Remarks.The specimen has a smooth cuticle (Fig. 4A).The posterior end has a broad postcloacal crescent directly at the point of bifurcation of the two tail lobes (Fig. 4B).Scattered bristles were observed on the posterior end of one male on the entire tail lobes extending to lateral of the cloacal opening.Due to some covering with dirt, such bristles could not be observed in the other male.Details such as bristles are not very well known from Asian species of Gordius and the specimen is kept here as Gordius sp.
Occurs in publications.unknown Remarks.The specimen has a smooth body cuticle (Fig. 4C), therefore no further determination is possible.
Remarks from the catalogue.collected by "Consul G. Siemssen" (no date given), received by the museum on September 4, 1912.Determined as "Gordiide".

Occurs in publications. unknown
Remarks.The body cuticle is smooth (Fig. 4D).The posterior end has the postcloacal crescent (Fig. 4E), which is characteristic for the genus Gordius.Parts of the posterior end are shrunken or covered with dirt, therefore no further structures could be observed and no further determination could be made.
Remarks from the catalogue.collected by A.H. Krause (no date given), received by the museum on March 14, 1913.Determined as "Gordius".
Occurs in publications.unknown Remarks.The cuticle is not in good shape, but it appears to be smooth (Fig. 4G), except for the posterior end, where some decent structuring into shallow areoles is present.The posterior end has a semicircular postcloacal crescent extending onto the tail lobes (Fig. 4F), some bristles are present in the posterior part of the inner side of the tail lobes.This description does not really fit present descriptions, but differences are not very large, therefore the specimen is kept here as Gordius sp. .
Remarks from the catalogue.collected by K. Schmalfuss (no date given).Received by the museum on December 23, 1920.Originally determined as "Gordiide".Although the catalogue indicates only one specimen, two females were found in the vial, named here (I) and (II).
Occurs in publications.unknown Remarks.Both specimens have a smooth cuticle covered by some dirt (Fig. 4H).Therefore they belong to the genus Gordius, but a further determination is not possible.
Location.Chile, Victoria in province Malleco (swimming in river).
Remarks from the catalogue.collected by C. Bock in February 1920.Received by the museum on August 12, 1921.
Occurs in publications.unknown Remarks.The cuticle is smooth (Fig. 4I), therefore this specimen must belong to the genus Gordius, but a further determination is not possible, because the posterior end is missing.
Remarks from the catalogue.Collected by N. Peters (date only given), received by the museum on June 7, 1927.Determined by Heinze in 1935 as Gordius muelleri (as mülleri).
Occurs in publications.unknown.

Remarks.
Unfortunately the posterior end of this specimen was lost during preparation for SEM, but it was a male posterior end with a postcloacal crescent.The cuticle is smooth (Fig. 4J).
Location.Brazil, Itatiaia, state of Rio de Janeiro, 700m, in a puddle.
Remarks from the catalogue.Collected by F. Ohaus (date unknown), donated to the museum by Titschak, received by the museum on March 15, 1928.Occurs in publications.unknown Remarks.This specimen clearly belongs to the genus Gordius due to the presence of a postcloacal crescent (Fig. 4L), but the cuticle is in bad shape (Fig. 4K) and a further determination cannot be given.
Location.probably Croatia, Rijeka.Writing in catalogue: "Umgeg.v. Fiume", Fiume is the Italian and Hungarian name for Rijeka (source: Wikipedia).This is supported by the added word "Jugoslavien" (Yugoslavia) in different handwriting.
Remarks from the catalogue.no collector indicated, given to the museum by de Gries.Received by the museum on September 24, 1928.Additional remark: from Lacerta muralis (common wall lizard).

Occurs in publications. unknown
Remarks.This is a Gordius specimen with smooth cuticle (Fig. 4M), but with roundish areoles in the posterior end.Some bristles were found on the edge of the tail lobes (Fig. 4O), but a further determination cannot be given.Lizards are not known and extremely unlikely as hosts.As no further specification of where the worm was found in relation to the lizard is given, it cannot be excluded that the worm has been eaten by the lizard and was found in the mouth.
Remarks.Unfortunately the posterior end of this specimen was lost during preparation for SEM, but it was a male posterior end with a postcloacal crescent.There are flat areoles (Fig. 5A), which are present in several species, therefore the determination cannot go beyong Gordius sp.
Remarks from the catalogue.Collected by Paul Missfeldt (no date given).Received by the museum on December 5, 1930.Originally determined as "Gordius".

Occurs in publications. unknown
Remarks.The body cuticle is smooth (Fig. 5B).The postcloacal crescent is semicircular (Fig. 5C).Few bristles are present along the lateral sides, extending onto the tail lobes.The fine structure of species of Gordius from South America is not well known and therefore this specimen cannot be determined further than to Gordius sp.
Location.Hungary.No further specification is given here, but number V11942 is also listed in the catalogue as a gordiid, with the same collector and location "Ungarn, Warmbad Villach, Thermenabfluss".This means the worm was found in the drainage of a spa.Today, Villach is a village in Austria, until 1918 Austria and Hungary were united, which could explain the catalogue entry.It is assumed that the same locality is valid also for V11943.A vial V11942 is present in the collection, but it contains no specimen.
Remarks from the catalogue.Collected by Gebhard (no date given) and received by the museum on September 28, 1933.Original determination as "Gordiiden".
Occurs in publications.unknown Remarks.The specimen has a postcloacal crescent bordering the point of bifurcation of the tail lobes (Fig. 5E) and the cuticle is smooth (Fig. 5D).Some bristles appear to be present in the posterior end on the sides of the tail lobes.
Remarks.Holotype of this species.Römer (1895) regards this specimen as a new species due to its extreme length and, in comparison to G. fulgur, another species of extreme length, by differences in diameter and colour.Nowadays it is generally assumed that size (length and width) as well as colouration patterns are quite variable, therefore these are no good characters to justify a new species description.One further difference is that G. longissimus is lacking an iridescence of the cuticle that G. fulgur has.The morphological reason for such iridescence is unknown.The cuticular surface is smooth (Fig. 5I).This is regarded to be a quite weak description for a species, but no changes of the systematical status are proposed here.The length was measured here as 126 cm, which is close to the 132 cm given by Römer.Gordiids are somewhat flexible when preserved and a correct length measurement is almost impossible.The host, a butterfly, is unusual for gordiids (see Schmidt-Rhaesa 2013).
Location.Germany, river Elbe close to Lauenburg.
Remarks from the catalogue.Collected by "Wilh.Meyer" on June 1, 1902.Received by the museum on July 1, 1902.Determined by Heinze in 1935 as Gordius mülleri.
Occurs in publications.Heinze (1937, page 320), Heinze (1941, page 59) Remarks.Areoles on the cuticle are roughly polygonal in shape and attach closely to each other (Fig. 6E).Few areoles appear a bit stretched, i.e. are broader than long.The narrow, semicircular postcloacal crescent is directly at the point of bifurcation of the tail lobes (Fig. 6F,  G).The cloacal opening is covered by dirt, but appears to be slightly oval (Fig. 6G).Heinze's determination as G. muelleri cannot be supported here.Gordius muelleri has areoles with broad interareolar spaces, a broad postcloacal crescent in distinct distance from the point of bifurcation of the tail lobes and an oval cloacal opening (e.g.Heinze 1941).Shape and position of the postcloacal crescent, in addition to the mostly polygonal areoles correspond with G. setiger, although the slightly oval cloacal opening and some "stretched" areoles are not completely corresponding characters.
Remarks from the catalogue.collected by "Gast" with unknown date.Received by the museum on June 15, 1920.Determined by Heinze in 1935 as Gordius setiger.
Occurs in publications.Heinze (1937, page 316), Heinze (1941, page 58) Remarks.The two species G. setiger and G. albopunctatus are very similar and differ only in few details.According to Heinze (1941), G. albopunctatus has polygonal areoles that are slightly stretched and their longer axis is perpendicular to the longitudinal body axis.Gordius setiger also has polygonal areoles, but they are irregularly polygonal without being stretched.Gordius albopunctatus has a parabolic postcloacal crescent, while this is semicircular in G. setiger.The specimen V9000 has clearly visible areoles that are slightly stretched as in G. albopunctatus (Fig. 6H).The postcloacal crescent, however, is semicircular as in G. setiger (Fig. 6I, J).The position of the cloacal opening in V9000 is directly anterior of the postcloacal crescent (Fig. 6I, J), while in both species, G. albopunctatus and G. setiger, there is some distance between these two structures.In summary, V9000 is intermediate between G. setiger and G. albopunctatus, which could hint to some yet unknown intraspecific variation.
Remarks from the catalogue.collected by H. Meves (date not given).Received by the museum on May 29, 1925.Originally determined as "Gordiiden".On the vial label, but not in the catalogue is written: determined as Gordius setiger by R. Arndt in 1968.
Occurs in publications.unknown Remarks.The two males of this lot show characters as described above for G. setiger and G. albopunctatus (see above under V9000).Male I has polygonal areoles (Fig. 6K), part of which appears to be stretched as in G. albopunctatus.The postcloacal crescent is semicircular as in G. setiger (Fig. 6L, M).Male II has polygonal, unstretched areoles as in G. setiger (Fig. 6N) and a narrow, but parabolic postcloacal crescent as in G. albopunctatus (Fig. 6O, P).Therefore, these two males support the discussion under V9000 that there are intermediate stages between the two species G. setiger and G. albopunctatus.
Remarks from the catalogue.Collected by an unknown person on June 9, 1980.
Remarks.Holotype of this species.See Schmidt-Rhaesa and Prous (2010) for all information about this specimen.
Remarks from the catalogue.Collected by T. Timm on July 7, 1971.
Remarks.Paratype of this species.See Schmidt-Rhaesa and Prous (2010) for all information about this specimen.
Remarks from the catalogue.Collected by H. Timm on August 16, 1993.
(1 male and 1 female) were reinvestigated by SEM.The cuticle of the male contains superareoles (Fig. 11K) and corresponds to the description of P. tolosanus (see, e.g., Heinze 1941).The female does not have superareoles, but only one type of areoles, it is therefore designed as Gordionus sp.under the new catalogue number V13361.
Material examined.V2236 (I) (1 male) One specimen is indicated in the catalogue, but 2 specimens are present.The second specimen is determined as Gordionus sp.; Fig. 11N, O.
Location.Göttingen, Germany Remarks from the catalogue.Collected by Schlotthauber (no collection date or date when received by the museum given).Determined by Schlotthauber in 1854 as Gordius aquaticus, corrected by Heinze in 1935 to Parachordodes tolosanus.Host: Harpalus ruficornis crossed out and replaced by Ophonus cephalotes.
A second specimen was found in the vial, which shows a different cuticular pattern and which is here determined as Gordionus sp.(V2236 II).As the catalogue indicates only one specimen, it is unknown whether this second specimen does belong to the vial originally.If it does, it is unknown whether both specimens emerged from the beetle.

Location. Göttingen, Germany
Remarks from the catalogue.Collected by Schlotthauber (no collection date or date when received by the museum given).Determined by Schlotthauber in 1854 as Gordius aquaticus, corrected by Heinze in 1935 to Parachordodes speciosus.Host: Harpalus distinguendus.
Remarks.SEM reinvestigation shows superareoles on the cuticle (Fig. 11P) that correspond to those described from P. tolosanus rather than those for P. speciosus (see Heinze 1941).

Genus Paragordionus Heinze, 1935
The genus Paragordionus resembles Gordionus in many respects, but the cuticle contains two types of areoles.The larger areoles are clustered together, such clusters can be composed of two or of several areoles.The large areoles are called megareoles (see Schmidt-Rhaesa 2002a, 2013, Schmidt-Rhaesa and Wagner 2013).Only five species have been described, and species limits require further investigations (Schmidt-Rhaesa and Wagner 2013).
Remarks from the catalogue.Collected by "Heinr.Baur" (not well readable) (no date given).Received by the museum on August 1, 1911.Determined by Heinze in 1935 as Paragordionus dispar.Although the catalogue says that only one specimen belongs to this lot, two specimens are present.These are marked with (I) and (II).
Remarks.The two specimens (I) and (II) both belong to the genus Paragordionus, because they possess clusters of megareoles (see Schmidt-Rhaesa 2002a).In specimen (II) the clusters of megareoles are smaller and include maximally three megareoles (Fig. 11I, J), while in specimen (I) clusters are larger and include clusters of up to seven megareoles (Fig. 11F, H).These differences correspond to the published descriptions of two different species, P. dispar and P. vejdovskyi (see, e.g., Heinze 1941).However, according to results of Schmidt-Rhaesa and Wagner (2013) the size and composition of the clusters are quite variable and species limits in this genus should be reinvestigated.As specimen (II) corresponds to the determination given by Heinze, it is assumed that this is the specimen he investigated and reported in the literature.Where the second specimen (I) comes from, whether it was originally present, but overlooked or whether it was added later is unknown and cannot be reconstructed.Occurs in publications.Schmidt-Rhaesa and Cieslak (2008).

Paragordionus ibericus
Remarks.Holotype of this species.See Schmidt-Rhaesa and Cieslak ( 2008) for all information about this specimen.

Material examined. V13261 (1 male)
Same data as V13260 (but no type material), see there.
Remarks.See V7449 (II) under Paragordionus dispar for all remarks and explanations.

Genus Paragordius Camerano, 1897
Specimens belonging to this genus are easy to recognize, because females have three lobes around the central and terminal cloacal opening and males have very long paired tail lobes (length: width 2:1 or longer).This genus includes the only species among Nematomorpha, where parthenogenetic reproduction was shown (P.obamai; Hanelt et al. 2012), the type material is in the collection (see below).
Remarks from the catalogue.Collected by Dr. P. (?) Hacker (no date given).Received by the museum on October 2, 1908.Determined as "Gordiide".Only 1 male is registered in the catalogue, while 2 males were found in the vial.
Occurs in publications.unknown Remarks.The long tail lobes of the male posterior end are characteristic for the genus Paragordius (Fig. 8C, D), but no further characters could be identified to determine the exact species.
Remarks from the catalogue.Collected by R. Paessler on December 16, 1915, received by the museum on January 15, 1920.Originally determined as "Gordiide".
Occurs in publications.unknown Remarks.The posterior end has three lobes, two broader and a slender one, which is typical for females of the genus Paragordius (Fig. 8F).The cuticle contains regular depressions and also longitudinal fissures (Fig. 8E).This character does not correspond to previous descriptions of species of Paragordius, but because part of the characters might be artificial, more specimens should be investigated before calling this a new species.
Remarks from the catalogue.Collected by R. Paessler in January 1917, received by the museum on January 15, 1920.Originally determined as "Gordiide".
Occurs in publications.unknown Remarks.The posterior end has three lobes, two broader and a slender one, which is typical for females of the genus Paragordius (Fig. 8H).The cuticle appears to be smooth, but has many small cracks (Fig. 8G), which is probably artificial.
Remarks from the catalogue.Received from Ben Hanelt.
Remarks.V13265 is the holotype for this species, V13266 and V13267 are paratypes.See Hanelt et al. (2012) for all information about this specimen.Paragordius obamai is the only known nematomorph reproducing by parthenogenesis.

Genus Pseudochordodes Carvalho, 1942
Pseudochordodes is a genus with distribution from the southwestern Nearctic to the Neotropis.Eight species have been described.The males have an unbranched posterior end (= without tail lobes) and the cuticle of both sexes has two types of areoles (see Schmidt-Rhaesa 2013 for summary).
Location.Guatemala Remarks from the catalogue.From bequest of "O.Hoffmann der Jul.Groth".Received by the museum on February 14, 1908.Originally determined as "Chordodes".
Occurs in publications.unknown Remarks.SEM reinvestigation reveals larger and smaller areoles (Fig. 12A, B) in an arrangement that corresponds to the description of Pseudochordodes meridionalis (see, e.g., Carvalho and Feio 1950, De Miralles and De Villalobos 1996, De Villalobos et al. 2005, 2008 [in part as Neochordodes meridionalis]).The cuticle contains areoles with an apical tubercle (Fig. 12B), such areoles appear also to be present in the specimen figured by De Villalobos et al. (2005, her  Remarks.The cuticle of this specimen shows areoles with no clear border and no interareolar structures (Fig. 16A).The surface of the areoles contains grooves, which are oriented parallel to the longitudinal body axis (Fig. 16A).There are regions between the areoles, where grooves are more numerous and create somewhat like a dense cluster of cuticular cords.There is some resemblance to Pseudochordodes gordioides, which is present in the Southwestern USA, but here a second type of areoles is more pronounced and has a different surface structure (see, e.g.Schmidt-Rhaesa et al. 2003).Therefore it is not clear to which genus or species this specimen belongs.
Remarks.The specimen is indeed in bad condition.No areoles were observed on the cuticle (Fig. 16B), therefore, the assignment to Chordodes is certainly wrong.As Römer (1895) described different kinds of "papillae" (= areoles) it appears likely that the current specimen is not the specimen investigated by Römer.SEM investigation reveals numerous tube-like structures (Fig. 16B, C), similar structures have been described by Schmidt-Rhaesa et al. (2001) and were assumed not to be cuticular structures.Heinze (1935a) has interpreted these structures as fungal hyphae that break through the cuticle.
Remarks.The posterior end is damaged, the sex cannot be determined.The cuticle is heavily covered with some covering, probably fungus (Fig. 16D, E).In some parts areoles are visible, these are irregularly shaped.The presence of areoles is in agreement with an assignment to the genera Gordius or Gordionus, but a further determination cannot be given.
Material examined.V6622 (sex not determined).Fig. 16F, G Occurs in publications.unknown Remarks.The cuticle is smooth and has some folds (Fig. 16F, G), but no proper determination is possible.Lepidoptera are not or only exceptionally host to nematomorphs (see Schmidt-Rhaesa 2013), therefore this specimen might not be a horsehair worm.
sp. Material examined.V2230 (1 female).Fig. 12C-G.Location.Venezuela, Ciudad Bolivar.Remarks from the catalogue.Collected by D. Siegert (no collection date or date when received by the museum given).Determined by Möbius in 1855 as Chordodes pilosus, confirmed by Römer in 1893 and Heinze in 1935.Host: Blabera gigantea.
Fig. 1D.Location.Chile Remarks from the catalogue.No detailed collecting locality in Chile mentioned, collector unknown.No collection date given and no date when received by the museum.Determined by Römer in 1893 as G. aquaticus, confirmed by Heinze in 1935.Occurs in publications.Römer (1895, page 792), briefly in Römer (1896, page 260).

Figure 1 .
Figure 1.Specimens of Gordius sp., ventral view of posterior ends and cuticle in midbody sections.The specimen number is indicated in the lower left of each image.A, B, G. Posterior ends with postcloacal crescent (pcc) and cloacal opening (co).The cuticular surface (C-F, H) is in some cases covered with encrusting material (C) or dirt (F, H).Diagonal lines are created by muscular fibers underlying the cuticle.

Figure 2 .
Figure 2. Specimens of Gordius sp., ventral view of posterior ends and cuticle in midbody sections.The specimen number is indicated in the lower left of each image.A-E, G-I.Cuticular surface.This is either smooth (A-C, G), has keel-like structures (D) or areoles (E, H, I).F, J, K. Posterior ends with postcloacal crescent (pcc) and cloacal opening (co).The posterior end of specimen V4611 has a fringed rim around the cloacal opening (J, K).

Figure 3 .
Figure 3. Specimens of Gordius sp., ventral view of posterior ends and cuticle in midbody sections.The specimen number is indicated in the lower left of each image.A, D, E, G, H, J-L.Cuticular surface, see text for explanation.B, F, I, M. Posterior ends with postcloacal crescent and cloacal opening (co).C. Magnification of short bristles on the tail lobes of V4981.

Figure 4 .
Figure 4. Specimens of Gordius sp., ventral view of posterior ends and cuticle in midbody sections.The specimen number is indicated in the lower left of each image.A, C, D, G, H-K, M. Cuticular surface, see text for explanation.B, E, F, L, N. Posterior ends with postcloacal crescent and cloacal opening (co).O. Areoles on the tail lobes of V10599.

Figure 5 .
Figure 5. A-F.Specimens of Gordius sp., ventral view of posterior ends and cuticle in midbody sections.G, H. Gordius aquaticus (V12685), cuticle (G) and posterior end (H).I. Cuticular surface of G. longissimus (V2229).J, K. Cuticle (J) and posterior end (K) of G. paranensis (V5035).Note row of bristles on the posterior end (arrows in K).L. Posterior end of G. paranensis (V11709), arrows as in K. M-O.Cuticle (M, N) and posterior end (O) of G. plicatissimus.The specimen number is indicated in the lower left of each image.

Figure 8 .
Figure 8. A-H.Paragordius sp., details of cuticle (A, B, E, G) and shape of the posterior ends of males (C, D; V3039) and females (F; V8948 and H; V8962).Arrow in F and H indicates the dorsal lobe.I-K.Beatogordius sp., longitudinal row of areoles (I), magnification of areoles (J) and posterior end (K).

Figure 12 .
Figure 12.A, B. Pseudochordodes meridionalis, V2930.Cuticular structure in low (A) and higher (B) magnification, encircled in B is a tubercle areole.C-O.Chordodes sp., specimen V2230 (C-G) was formerly designated as holotype of C. pilosus.C. Overview onto the ventral side.Note elevated clusters on both sides of the ventral midline (vml).D. Overview onto the lateral side.Note scattered elevated clusters (arrow indicates one of these clusters).E. Higher magnification shows that the clusters are composed of elevated areoles.F. Clusters of crowned areoles (crar) and circumcluster areoles (ccar) are strongly eroded.Image shows a cluster from next to the ventral midline which includes crowned areoles with long apical filaments.G. Strongly eroded cluster from the lateral body side.H-O.Specimen V5320; H-K female specimen, L-O male specimen.H, I. Arrangement of crowned areole clusters with long filaments next to the ventral midline (vml).J. Two central crowned areoles within a cluster.K. Crowned areoles (crar) surrounded by circumcluster areoles (ccar).L-O.Cuticle and areoles in the male, see female for abbreviations.P-S.Chordodes brasiliensis, different specimens of number V7351.Cuticle shows scattered elevated crowned areoles among simple areoles (sar).Specimen V7351d has part of the cuticle covered by rests of the larval cuticle (lc).

Remarks from the catalogue. Collected
by Schlotthauber (no collection date or date when received by the museum given).Determined by Schlotthauber in 1854 as Gordius aquaticus, corrected by Heinze in 1935 to Parachordodes tolosanus.Host: Harpalus ruficornis crossed out and replaced by Ophonus cephalotes. .
. Location.Germany, Hamburg, river Bille.Remarks from the catalogue.Collected by Steinblinck (no date given).Received by the museum on January 25, 1895.Determined by Römer in 1893 as Gordius violaceus, corrected to Gordionus meissneri by Heinze in 1935.
. Location.Germany, Rügen.Remarks from the catalogue.Collected by A. Thienemann (date unknown).Received by the museum on November 12, 1930.Originally determined by A. Thienemann as Parachordodes tolosanus.Corrected by Heinze in 1935 to Gordionus violaceus.
. Location.Germany, Hannover, River Örtze.Remarks from the catalogue.Collected by Th.Lindemann (no date given).Received by the museum on July 28, 1904.Determined by Michaelsen in 1904 as Gordius aquaticus and by Heinze in 1935 as Gordius setiger.

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Location.Germany, Ahrensburg.Remarks from the catalogue.Collected by Post (no date given).Received by the museum on September 8, 1900.Determined by Heinze in 1935 as "Gordius ?undulatus".

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Location.Germany, Hamburg.Remarks from the catalogue.Collected by Rump (no date given).Received by the museum on November 10, 1904.Host: Vanessa io (European peacock, currently Aglais io or Inarchis io, Lepidoptera).