Corresponding author: Kai Horst George ( firstname.lastname@example.org )
Academic editor: Michael Ohl
© 2017 Kai Horst George.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation: George KH (2017) Phylogeny of the taxon Paralaophontodes Lang (Copepoda, Harpacticoida, Laophontodinae), including species descriptions, chorological remarks, and a key to species. Zoosystematics and Evolution 93(2): 211-241. https://doi.org/10.3897/zse.93.11314
A detailed phylogenetic analysis of the taxon Paralaophontodes Lang (Copepoda, Harpacticoida, Laophontodinae Lang) based on morphological characters is presented. The monophylum Paralaophontodes is supported by 16 unambiguous autapomorphies such as the presence of characteristic dorsal processes on cephalothorax and body somites, a 5-segmented male antennule, the loss of the syncoxal seta on the maxilliped, and the endopodal strengthening of the first swimming leg. The corresponding extensive phylogenetic evaluation includes the description of Paralaophontodes anjae sp. n. from a beach on Chiloé Island (Chile), the re-description of Laophontodes armatus Lang, and the re-establishment of Paralaophontodes robustus (Bŏzić), the displacement of Laophontodes armatus, L. hedgpethi Lang and L. psammophilus Soyer to Paralaophontodes, a discussion on relationships within that taxon, remarks on its geographical distribution, and a key to the species.
Crustacea, Meiofauna, Ancorabolidae, systematics, taxonomy, geographical distribution
When describing Laophontodes hedgpethi Lang, 1965,
Paralaophontodes anjae sp. n.: one single female was collected by the author on 27.03.1994 in Puente Quilo (Gulf of Quetalmahue), Chiloé Island, Chile. The material was sampled at low tide at station #Q4 directly at the waterline (Fig.
Map showing the locus typicus (black star) of Paralaophontodes anjae sp. n. in Puente Quilo, Gulf of Quetalmahue, Chiloé Island, Chile.
Paralaophontodes echinatus (Willey, 1930): two females and one male were collected by Mr Johannes Dürbaum (Jülich, Germany) from an intertidal mangrove-mudflat at Bering Point village, south-east of Andros Island, Bahamas, in July 1993 (cf.
Paralaophontodes exopoditus Mielke, 1981: one female collected by Dr Gritta Veit-Köhler (Wilhelmshaven, Germany) at the coastline of Dahab (28°29.0’N, 34°30.0’E, Gulf of Akaba, Egypt) in summer 1995. The specimen was kindly put to the author’s disposal and is kept in the collection of Senckenberg Forschungsinstitut und Naturmuseum Frankfurt, Germany, coll. no.
Laophontodes armatus Lang, 1936: The type material (coll. no. Type
Species identification and drawings were made with the use of a camera lucida on a Leica DMR compound microscope equipped with differential interference contrast. General terminology follows
Abbreviations used in the text: A1 = antennule, A2 = antenna, aes = aesthetasc, benp = baseoendopod, cphth = cephalothorax, DP I–DP IX = dorsal processes I–IX, enp = endopod, enp-1–enp-3 = endopodal segments 1–3, exp = exopod, exp-1–exp-3 = exopodal segments 1–3, FR = furcal rami, GF = genital field, P1–P6 = swimming legs 1–6, R = rostrum, T = telson.
Subphylum Crustacea Brünnich, 1772
Superclass Multicrustacea Regier et al., 2010
Class Hexanauplia Oakley et al., 2013
Subclass Copepoda Milne-Edwards, 1840
Order Harpacticoida Sars, 1903
Family “Ancorabolidae” Sars, 1909
Subfamily Laophontodinae Lang, 1944
P. echinatus (Willey, 1930). Additional species: P. anjae sp. n., P. armatus (Lang, 1936) comb. n., P. elegans Baldari and Cottarelli, 1986, P. exopoditus Mielke, 1981, P. hedgpethi (Lang, 1965) comb. n., P. psammophilus (Soyer, 1974) comb. n., P. robustus (Bŏzić, 1964).
Laophontodinae. Body slender and cylindrical. Cphth with triangular extensions medio- and postero-laterally (not clearly pronounced in P. elegans). Cphth with dorso-median ridge extended into 2 posteriorly directed blunt, conical elevations and covered by tuft of hair-like setules in anterior half. P2–P5-bearing thoracic somites dorsally with sclerotized processes bearing sensilla at their tips. First to penultimate abdominal somites with pair of dorsal processes that are transversely connected, appearing H- or even A-shaped. Telson narrowest body somite, rectangular, with anal operculum dorsally. Furcal rami approximately 3–5 times longer than broad, with 7 setae; setae I and II close together, V longest seta. A1 4-segmented in female; 5-segmented and chirocer in male, with fourth segment strongly swollen and bearing a strong spine. A2 lacking exp, or if present small and knob-like, with 1 small, bare apical seta. Md palp unilobate, exp represented by 1 seta, enp represented by 3 setae. Mx with 2 elongate and slender endites bearing 2–3 apical setae. Mxp without syncoxal seta. P1 exp 2- to 3-segmented; P1 enp-2 distinctly elongate, reaching at least half the length of enp-1, equipped with strong claw accompanied by 1 minute seta, an additional long geniculate seta may be present. P2–P4 with laterally elongate bases. Exopods 3-segmented (fused to 1 long segment in P2 and P3 in P. robustus); P2 lacking endopod, P3 with or without small knob-like endopod carrying 1 small bare seta, P4 with or without 2-segmented endopod. P5 with outer seta arising from long setophore; benp completely reduced; in female represented by 2 setae, in male represented by 1 seta; with 1–3 long tube pores. Exp fused with baseoendopodal part, long and slender, laterally with 2 setae; subapically with 1 inner and 1 outer seta; apically with 1 long seta; tube pores present or absent. Female P6 small, located in front of gonopore, consisting of small segment separated from or fused with somite, with 0–2 small setae. The taxon is justified as a monophylum due to 16 unambiguous autapomorphies (see Discussion).
Puente Quilo, Canal de Quetalmahue, Chiloé Island, Chile, 41°51.671’S, 73°58.926’W, 0m (Fig.
Female holotype, distributed over 10 slides, coll. no. 37103/1–10.
The specific epitheton “anjae” is given in fondly dedication to the author’s sister Mrs Anja George (Osorno, Chile); gender: feminine.
Paralaophontodes anjae sp. n., female. (A) habitus, dorsal view; (A’) dorsal process IX; (B) P5; (C) genital field. Scale bars: (A) 100µm; (A’, B, C) 50µm.
Paralaophontodes anjae sp. n., female. (A) A1 and rostrum, arrow showing insertion of aes and accompanying setae of counterpart; (B) telson and FR, ventral view, Roman numerals indicating furcal setae. Scale bar: 50µm.
Setal formula: 1/1; 2/8; 3/7+ aes; 4/10+ aes.
Paralaophontodes anjae sp. n., female. (A) A2; (B) md; (B’) mandibular palp of counterpart; (C) mxl; (D) mx, proximal endite separated (arrow); (E) mxp. Scale bars: (A, E) 50µm; (B, B’–D) 20µm.
Paralaophontodes anjae sp. n., female. (A) P1, claw broken; (A’) P1 enp-2 of counterpart; (B) P2 showing rudimental intercoxal sclerite; (C) P3; (D) P4. Scale bar: 50µm.
Paralaophontodes anjae sp. n., setation of P2–P4. Roman numerals indicate outer spines.
Laophontodes typicus T. Scott, 1894. Additional species: According to
The re-description is based on one female (habitus) and the fragments of the type series, in order to destroy as few complete individuals as possible, and because of the compact detritus coverage on most complete specimens. Types
In addition, the female and the male of the Magellan material were included to complete the re-description (additional female habitus, male habitus, mouthparts, sexual dimorphic parts of male).
Paralaophontodes armatus (Lang, 1936) comb. n., female from the type series. (A) habitus, dorsal view, dorsal processes labelled DP I–DP IX; (B) urosome of second female; (C) dorsal processes DP V–DP IX, detail, of third female. Arrow points to cuticular overlap of sensillum-bearing tip. Scale bars: (A, B) 100µm; (C) 50µm.
Paralaophontodes armatus (Lang, 1936) comb. n., (A) female from the Magellan material (Punta Arenas), habitus dorsal; (B, B’) dorsal Processes DP VIII and DP IX of A.; (C) male from the Magellan Material (Punta Yartou), habitus dorsal. Scale bars: (A, C) 100µm; (B, B’) 50µm.
Paralaophontodes armatus (Lang, 1936) comb. n., female from the type series. (A) A1; (B) A2; (C) mxp; (D) FR, dorsal view; (E) genital field. Scale bar: 50µm.
Md, mxl, and mx described from male.
Paralaophontodes armatus (Lang, 1936) comb. n., (A, B) female from the type series; (A) P1; (B) P5; (C) male from the Magellan material (Punta Yartou), P5. Scale bar: 50µm.
Laophontodes armatus Lang, 1936, setation of P2–P4. Roman numerals indicate outer spines.
Paralaophontodes armatus (Lang, 1936) comb. n., (A–C) female from the type series; (A) P2, triangular arrow indicates insertion of the ancestral endopod; (B) P3; (C) P4 endopod; (D, E) male from the Magellan material (Punta Yartou); (D) P3 endopod; (D’) P3 apophysis of counterpart; (E) P4 endopod. Scale bar: 50µm.
The male differs from the female in the following features: body size, shape of A1, shape of P3 and P4 endopods, ornamentation of P5, complete loss of P6.
Paralaophontodes armatus (Lang, 1936) comb. n., male from the Magellan material (Punta Yartou); (A) A1, setation of segments 3–5 shown separately; (B) md; (C) mxl; (D) mx. Scale bars: (A) 50µm; (B–D) 20µm.
Laophontodes armatus causes remarkable confusion. Comparison of
A further discrepancy concerns the descriptions of both
Paralaophontodes armatus (Lang, 1936) comb. n., (A–C) P2 (bases) of different females of the type series; (D) P2 of male from the Magellan material (Punta Yartou); (E) P2 of female from the Magellan material (Punta Arenas); triangular arrows pointing to insertion of the ancestral endopod; (F) intercoxal sclerite of A; (G) intercoxal sclerite of C. Scale bar: 50µm.
The remaining swimming legs, P3 and P4, of the Falkland females do present endopods. Both the single male and the female specimens from the new Chilean material also lack a P2 endopod (Fig.
Paralaophontodes was assigned to Laophontodinae by
When erecting Paralaophontodes,
Based on the summary given above, it is concluded that a monophylum Paralaophontodes is, according to
A. P1 exp 2-segmented [P1 exp 3-segmented];
B. P2 lacking endopod [P2 with at least 1-segmented endopd];
C. P4 lacking endopod [P4 with at least 1-segmented endopod].
All known Paralaophontodes species share these apomorphies, whilst they are missing from the Laophontodes species treated here (
To evaluate phylogenetic relationships, synapomorphies, i.e. unique derived characters of the treated taxa must be recognized (
All species treated in the present contribution (Fig.
Habitus views of the representatives of Paralaophontodes reviewed for the present contribution. (A) P. echinatus (Willey, 1930); (B) P. armatus (Lang, 1936) comb. n.; (C) P. robustus (Bŏzić, 1964); (D) P. psammophilus (Soyer, 1975) comb. n.; (E) P. hedgpethi (Lang, 1965) comb. n.; (F) P. elegans Baldari and Cottarelli, 1986; (G) P. anjae sp. n.; (H) P. exopoditus Mielke, 1981. (A, C–F, H) modified after different authors; (B, G) originals; no scales.
Character 1 – Rostral tip distinct, knob-like: Compared with other Laophontodinae, those species considered here exhibit a protruded rostrum as do Lobopleura and Probosciphontodes, and also several Ancorabolinae (e.g. Ancorabolina, Ancorabolus, Dorsiceratus, Echinopsyllus, Pseudechinopsyllus). Moreover, many other harpacticoid taxa show a (more or less) strongly protruded rostrum (c.f.
Character list used for the phylogenetic analysis of the monophylum Paralaophontodes. Apomorphies are marked with 1, plesiomorphies with 0, question mark means no data available. Abbreviations: Outgr. = remaining Laophontodinae, P. ro. = Paralaophontodes robustus, P. ec. = P. echinatus, P. el. = P. elegans, P. ex. = P. exopoditus, P. an. = P. anjae sp. n., P. ar. = P. armatus comb. n., P. ps. = P. psammophilus comb. n., P. he. = P. hedgpethi comb. n.
|No||Character/species [plesiomorphic states in square brackets]||Outgr.||P. ro.||P. ec.||P. el.||P. ex.||P. an.||P. ar.||P. ps.||P. he.|
|1||Rostral tip distinct [no distinct rostral tip]||0||1||1||1||1||1||1||1||1|
|2||Cphth with dorso-median ridge extend into 2 backwardly directed blunt conical processes [neither dorsal ridge nor processes developed]||0||1||1||1||1||1||1||1||1|
|3||Cphth dorso-median ridge with hairy tuft [no hairy tuft present]||0||?||1||1||1||1||1||1||1|
|4||P2-bearing thoracic somite with dorsal pair of processes [no processes]||0||1||1||1||1||1||1||1||1|
|5||P3-bearing thoracic somite with dorsal pair of processes [no processes]||0||1||1||1||1||1||1||1||1|
|6||P4-bearing thoracic somite with dorsal pair of processes [no processes]||0||1||1||1||1||1||1||1||1|
|7||P5-bearing thoracic somite with dorsal pair of processes [no processes]||0||1||1||1||1||1||1||1||1|
|8||P6-bearing thoracic somite with dorsal pair of processes [no processes]||0||1||1||1||1||1||1||1||1|
|9||1st abdominal somite dorsally with pair of A- or H-like processes [no processes]||0||1||1||1||1||1||1||1||1|
|10||2nd abdominal somite dorsally with pair of A- or H-like processes [no processes]||0||1||1||1||1||1||1||1||1|
|11||3rd abdominal somite dorsally with pair of A- or H-like processes [no processes]||0||1||1||1||1||1||1||1||1|
|12||Male A1 5-segmented [at least 6-segmented]||0||?||1||?||1||?||1||?||1|
|13||Male antennular swollen segment with strongly developed, tooth-like spine [no such spine present]||0||?||1||?||1||?||1||?||1|
|14||Mxp without syncoxal seta [syncoxa retaining 1 apical seta]||0||1||1||1||1||1||1||1||1|
|15||P1 enp strongly strengthened, transformed into mighty appendage [P1 slender, gracile]||0||1||1||1||1||1||1||1||1|
|16||P1 enp-2 distinctly elongated, reaching at least half the length of enp-1 [P1 enp small]||0||1||1||1||1||1||1||1||1|
|17||P2 exp-2 without inner seta [inner seta present]||0||1||1||1||1||1||1||1||0|
|18||P3 exp-2 without inner seta [inner seta present]||0||1||1||1||1||1||1||1||0|
|19||P4 exp-2 without inner seta [inner seta present]||0||1||1||1||1||1||1||1||0|
|20||P2 exp-3 without inner seta [inner seta present]||0||1||1||1||1||1||1||1||0|
|21||Abdominal dorsal processes with long and flexible setules [no such setules present]||0||0||0||0||0||0||0||0||1|
|22||P2 enp completely lost [enp 2-segmented]||0||1||1||1||1||1||1||0||0|
|23||P3 exp-3 without inner seta [inner seta present]||0||1||1||1||1||1||1||0||0|
|24||P4 exp-3 without inner seta [inner seta present]||0||1||1||1||1||1||1||0||0|
|25||P1 basis laterally extended = base for exp [no lateral extension of P1 basis]||0||0||0||0||0||0||0||1||0|
|26||P1 enp-2 geniculated apical seta lost [apical geniculated seta present]||0||1||1||1||1||1||0||0||0|
|27||P1 exp 2-segmented [P1 exp 3-segmented]||0||1||1||1||1||1||0||0||0|
|28||P2 exp-3 inner apical seta minute [seta long, flexible]||0||1||1||1||1||1||0||0||0|
|29||P3 exp-3 inner apical seta minute [seta long, flexible]||0||1||1||1||1||1||0||0||0|
|30||P4 exp-3 inner apical seta minute [seta long, flexible]||0||1||1||1||1||1||0||0||0|
|31||P3 enp female at most 1-segmented [enp 2-segmented]||0||1||1||1||1||1||0||0||0|
|32||P3 female enp with 1 seta only [with 2 setae]||0||1||1||1||1||1||0||0||0|
|33||P4 enp completely lost [enp 2-segmented]||0||1||1||1||1||1||0||0||0|
|34||P5 with fishbone-like setae [seta of regular bipinnate shape]||0||0||0||0||0||0||1||0||0|
|35||P1 exp-2 with 4 setae [with 5 setae]||0||1||1||1||0||0||0||0||0|
|36||A2 abexopodal seta lost [abexopodal seta present]||0||1||1||1||0||0||0||0||1|
|37||A2 without exp [with 1-segmented exp]||0||1||1||1||0||1||1||0||1|
|38||P2-bearing thoracic somite dorsal processes H-like [without transverse connection]||0||0||0||1||1||0||0||0||0|
|39||P3-bearing thoracic somite dorsal processes H-like [without transverse connection]||0||0||0||1||1||0||0||0||0|
|40||P4-bearing thoracic somite dorsal processes H-like [without transverse connection]||0||0||0||1||1||0||0||0||0|
|41||P5-bearing thoracic somite dorsal processes H-like [without transverse connection]||0||0||0||1||1||0||0||0||0|
|42||P6-bearing thoracic somite dorsal processes H-like [without transverse connection]||0||0||0||1||1||0||0||0||0|
|43||P3 female enp represented by single seta [exp 1-segmented]||0||0||0||0||1||0||0||0||0|
|44||P2 exps 1-3 fused [exps 1-3 separated]||0||1||0||0||0||0||0||0||0|
|45||P3 exps 1-3 fused [exps 1-3 separated]||0||1||0||0||0||0||0||0||0|
|46||Rostrum constricted [rostrum broad at ist base, tapering anteriorly]||0||0||0||1||0||0||0||0||0|
|47||P5 benp setae minute [setae reaching at least half of exopodal length]||0||0||0||1||0||0||0||0||0|
|48||Mxl coxa with 1 seta [coxa with 2 setae]||0||?||0||1||0||0||0||?||0|
|49||P3 enp female completely lost [enp at least 1-segmented]||0||1||0||0||0||1||0||0||0|
|50||Mx enp with 1 seta [enp with 2 setae]||0||?||1||1||0||0||0||?||1|
Character 2 – Cphth with dorso-median ridge extended into 2 posteriorly directed blunt conical elevations: The formation of dorsal sclerotized structures on cphth and body somites has been considered to be one of the characteristic features of the (paraphyletic, cf.
Character 3 – Cephalic dorso-median ridge covered with tuft of hair-like setules in anterior half: A tuft of hair-like setules covers the anterior part of the cephalic ridge.
Characters 4–8 – P2–P6-bearing thoracic somites with dorsal pair of processes: The presence of dorsal (and often also dorso-lateral and/or lateral) cuticular processes is considered characteristic for Ancorabolinae. In Laophontodinae, however, only Paralaophontodes has dorsal sensilla-bearing processes at the thoracic somites (Fig.
Habitus views of (A, B) Laophontodes whitsoni T. Scott, 1912; (C) Lobopleura ambiducti Conroy-Dalton, 2004; (D) Probosciphontodes stellata Fiers, 1988. (A, B) from
Characters 9–11 – First to penultimate abdominal somites with pair of A- or H-shaped processes dorsally: Similar to the circumstances regarding the thoracic somites, Paralaophontodes and Laophontodes armatus, L. hedgpethi and L. psammophilus are exceptions within Laophontodinae in carrying very characteristic processes on the three abdominal somites, but not the telson. The processes are paired, strongly sclerotized, and close together at the dorsal posterior margin of each abdominal somite. These processes are (not always) connected by a transverse cuticular ridge (Fig.
Character 12 – Male antennule 5-segmented: Whereas in Ancorabolinae the subchirocer male antennule retains eight segments (Fig.
Schematic illustration of the different male antennules, showing from (A–D) the successive reduction of segments (*). Explanation in the text.
Character 13 – Male antennular swollen segment with strongly developed, tooth-like spine: All known males of Paralaophontodes present a characteristic strong and tooth-like spine situated proximally at the anterior margin of the swollen antennular segment 4 (cf. Fig.
Character 14 – Mxp without syncoxal seta: Character 14 poses a certain degree of incertitude. Firstly, in older descriptions of Laophontodinae (mainly Laophontodes species), the maxilliped has been illustrated and described rather roughly, and therefore potentially not observing existing rows of spinules, the typical minute seta that accompanies the maxillipedal claw, and the syncoxal apical seta. Such an assumption seems to be justified when considering the differences between the original descriptions of e.g. Laophontodes bicornis A. Scott, 1896 or L. whitsoni T. Scott, 1902 with recent re-descriptions: In their original descriptions both species lack all of the above mentioned features, but all were observed on re-examination (
Within the supposed sister-group of Laophontodinae, Ancorabolinae, the loss of the syncoxal seta has occurred in the whole Ancorabolus-lineage, as well as in some genera of the Ceratonotus-group (Echinopsyllus and Pseudechinopsyllus). This points towards a convergent loss of the syncoxal seta in both supposed monophyla. In Ancorabolina and in most Laophontodinae (Calypsophontodes, Laophontodes, Lobopleura, Probosciphontodes) the syncoxal seta is present (but keep in mind the comparison “old vs. recent descriptions”). Apart from the species treated here, the Laophontodinae Algensiella, Patagoniaella and Tapholaophontodes also lack the syncoxal seta on mxp, but it seems unlikely that they are closely related to Paralaophontodes and Laophontodes armatus, L. hedgpethi and L. psammophilus since they each lack the other apomorphies listed above. It is therefore hypothesized that in both Ancorabolinae and Laophontodinae the loss of the syncoxal seta of the mxp occurred independently (at least) twice. Considering the other apomorphies shared by the species treated here, however, it appears probable and plausible that this reduction took place in a common ancestor of Paralaophontodes and must therefore be considered as an autapomorphy for that genus.
Character 15 – P1 enp considerably strengthened, transformed into powerful appendage: Laophontodinae and part of Ancorabolinae share a “laophontoidean-like” P1 that is characterized by a 2- to 3-segmented exp of rather small size and slender shape and a 2-segmented, elongated, prehensile enp (cf.
Character 16 – P1 Enp-2 distinctly elongate, reaching at least half the length of enp-1: As assumed by
Compared to apomorphy A discussed above (see section, ‘The taxon Paralaophontodes reconsidered’: P1 exp 2-segmented), characters 15 and 16 are of greater phylogenetic relevance, as they are not simple reductions of a segment (which occurs quite often within Harpacticoida, i.e. an incongruent character). Characters 15 and 16 are instead diagnostic transformations of particular parts of a swimming leg, and are therefore congruent, detectable exclusively in the Paralaophontodes and the Laophontodes “armatus-group” species.
Additional remarks: As described for Paralaophontodes anjae sp. n., the intercoxal sclerites P2–P4 are strongly reduced. They are of a triangular, thorn-like shape and do not connect the legs. Apart from P. anjae sp. n., this condition mentioned by
The description of Paralaophontodes robustus provided by
Uncertainty persists with respect to the reports of P. robustus in the Mediterranean.
The specimen described by
P. robustus does present fused P2 and P3 exopods as autapomorphic specific character. This would mean that both
Unfortunately, the original material is not available, and therefore additional material from both La Réunion and the French locations is needed for further comparison to determine the correct status of these records.
Paralaophontodes anjae sp. n. shares all the mentioned generic autapomorphies 1–16 of Paralaophontodes. It differs from already known species, primarily by the derived condition of the complete loss of a female P3 endopod. That endopodal loss separates P. anjae sp. n. from all other Paralaophontodes and Laophontodes “armatus-group” species, L. armatus, L. hedgpethi and L. psammophilus, with one exception: P. robustus also lacks a P3 enp in female (see previous section). Nevertheless, P. anjae sp. n. and P. robustus differ regarding the following features: (i) cephalic lateral extensions strongly triangular in P. robustus, but only moderately triangular in P. anjae sp. n.; (ii) pedigerous somites bearing P2–P5 dorsally with tiny socles in P. robustus, while bearing strong sclerotized processes in P. anjae sp. n.; (iii) P1 exp-2 with 4 bare geniculate setae in P. robustus but with 5 bare geniculate setae in P. anjae sp. n.; (iv) P2 and P3 exopodal segments fused in P. robustus, but separated in P. anjae sp. n. Therefore, the erection of a new species to assign the Chilean specimen is well-justified.
Based on the comprehensive phylogenetic discussion given above, it is established that the species Laophontodes armatus, L. hedgpethi and L. psammophilus share apomorphic characters 1–16 (characters 12 and 13 unknown for L. psammophilus) with the currently accepted Paralaophontodes species and are therefore considered to be their close relatives.
The above presented discussion confirms that the taxon Laophontodes is actually quite a heterogeneous collection of species (
Concerning the differences that led to the “armatus-group” previously being retained in Laophontodes (i.e. the 3-segmented P1 exp, the retention of an apical seta in P1 enp-2, and the presence of endopods in P2 and P4), these are rejected here according to the detailed character discussion presented above. With the transfer of the “armatus-group” into Paralaophontodes, these characters are assumed to have evolved within Paralaophontodes, a condition that is commonplace in Harpacticoida.
While the monophylum Paralaophontodes is in the author’s opinion well-founded, unambiguously supported by autapomorphies 1–16 (see above), the relationships within Paralaophontodes are difficult to discern. Thirty-four additional morphological characters (17–50, Tab.
Cladogram summarising the results of the phylogenetic analysis presented in the text. Enumeration of apomorphies according to the text.
A supposed basal position within the genus may correspond to P. hedgpethi comb. n. It is the only species to show the assumed plesiomorphic state in characters 17–19 (the retention of an inner seta in the second exopodal segment of P2–P4) and in character 20 (the retention of an inner seta also in P2 exp-3). It can be justified as a distinct species due to character 21 (the exclusive possession of long and flexible setules on the abdominal dorsal processes:
P. hedgpethi comb. n. is followed by P. psammophilus comb. n., as both species retain a P2 endopod (character 22) as well as an inner seta on P3 and P4 exp-3 (characters 23, 24). In contrast, all remaining Paralaophontodes species share the derived condition that is the complete loss of a P2 endopod, and the loss of inner setae on P3 and P4 exp-3. Nonetheless, P. psammophilus comb. n. can be characterized by an autapomorphy, namely the transverse extension of the P1 basis (character 25) to which the P1 exopod is connected. Such transverse extension is virtually absent within Laophontodinae (exception: Laophontodes gracilipes Lang, 1936) but expressed in Ancorabolina and showing its strongest development in Ancorabolinae.
Next in the systematic hierarchy might be P. armatus comb. n. which, together with P. hedgpethi comb. n. and P. psammophilus comb. n., holds the ancestral states of a series of characters: possession of a geniculated seta on P1 enp-2 (Character 26), P1 exopod still 3-segmented (character 27), P2–P4 exp-3 inner apical seta long and flexible (characters 28–30), P3 female endopod 2-segmented (character 31) and carrying 2 setae (character 32), and P4 still bearing an endopod (character 33). Otherwise, Paralaophontodes armatus comb. n. may be characterized by the presence of 1 (female) or 2 (male) fishbone-like setae at the P5 (character 34). The corresponding setae in the remaining Paralaophontodes species and in the Laophontodinae in general are usually bipinnate. In P. armatus comb. n. these setae show strongly developed pinnae which are fused to the seta, giving a fishbone-like appearance. These fishbone-like setae are considered as an autapomorphy of P. armatus comb. n.
The remaining clade [P. anjae sp. n.—P. echinatus—P. elegans—P. exopoditus—P. robustus] is characterized by the derived states of characters 26–33 (see Table
With respect to characters 36 and 37, it has to be conceded that both characters are somewhat weak. The loss of the abexopodal seta in A2 (36) is also described for the presumed most primitive P. hedgpethi comb. n., and loss of the A2 exopod (37) is also recorded in P. anjae sp. n., P. armatus comb. n. and P. hedgpethi comb. n. (cf. Table
The resulting partly unsatisfactory systematic resolution within Paralaophontodes may be an effect from limitations in information available on morphological characters, and therefore genetic comparison should be considered in future studies (but see below). Nevertheless, this lack of resolution undoubtedly also results from insufficient and incomplete species descriptions that can and should be resolved in the future. As an example Table
|1||All free body somites with strongly developed dorsal cuticular processes||2|
|–||Strongly developed cuticular processes restricted to abdominal somites only||3|
|2||P1 exp 3-segmented; at least P4 with endopod||4|
|–||P1 exp 2-segmented; P2 and P4 without endopods||5|
|3||P1 exp 3-segmented; P1 enp-2 with claw, 1 tiny seta and 1 additional long seta; P2 and P3 with 3-segmented exps; P2 and P4 with enps||P. hedgpethi Lang, 1965|
|–||P1 exp 2-segmented; P1 enp-2 with claw and 1 small seta only; P2 and P3 exopodal segments not separate, 1-segmented; P2–P4 lacking enps||P. robustus (Bŏzić, 1964)|
|4||Cephalic lateral extensions moderately triangular; A2 with 1-segmented small exp bearing 1 bare seta; P2 with enp||P. psammophilus (Soyer, 1974)|
|–||Cephalic lateral extensions strongly triangular; A2 without exp; P2 without enp||P. armatus (Lang, 1936)|
|5||Rostrum narrowed; cephalic lateral extensions only weakly developed; P5 baseoendopodal setae small, not reaching insertion of first outer exopodal seta||P. elegans Baldari and Cottarelli, 1986|
|–||Rostrum triangular; cephalic lateral extensions strongly triangular; P5 baseoendopodal setae long, surpassing insertion of second outer exopodal seta||6|
|6||P1 exp-2 with 5 geniculate setae; female P6 fused to body somite, represented by 1 small bipinnate seta||7|
|–||P1 exp-2 with 4 geniculate setae; female P6 distinct, small segment carrying 2 bare setae; P3 endopod a small, knob-like segment with 1 small bare seta; A2 without exp||P. echinatus (Willey, 1930)|
|7||A2 with minute knob-like exp carrying 1 small seta; female P3 enp represented by small bare seta||P. exopoditus Mielke, 1981|
|–||A2 without exp; female P3 enp completely los||P. anjae sp. n.|
Map showing the world-wide distribution of Paralaophontodes Lang, 1965; including the distribution patterns of the respective species.
Additional Paralaophontodes material kindly given to the author provides further chorological information for some of the Paralaophontodes species (Fig.
Summarizing the above compiled records, the taxon Paralaophontodes shows an almost world-wide distribution, so far remaining absent only from the Central Atlantic, the High Antarctic and the Arctic. However, with the Falklands’ records of P. armatus in mind, it might be assumed that Paralaophontodes may be also distributed northwards into the Atlantic Ocean as well as southwards into high Antarctic regions. The latter may be supported by the record of P. psammophilus from Kerguelen (
It is noteworthy that all findings of Paralaophontodes are restricted to the littoral, with the deepest record at 15 m (P. armatus, Punta Yartou, Magellan Straits, Chile). Even in the vastness of the oceans, records of Paralaophontodes have only been documented from the shores of oceanic islands, while extensive sampling in the deep sea (e.g.
One might expect that Paralaophontodes would be present on Atlantic islands, as it is in the Indian and Pacific Ocean. However, despite extensive qualitative sampling in Madeira and Porto Santo Island (
Whereas statements on wide meiofaunal distribution ranges usually remain unquestioned at the genus level (e.g.
Additional molecular studies might sharpen the so far observed distribution patterns, and admittedly it is imaginable that the named Paralaophontodes species may constitute complexes of more than one species. One should keep in mind, however, that although genetic studies are without doubt important and provide valuable contributions in chorological and biogeographic research, their results should not be overzealously followed to the neglect or even rejection of morphological approaches.
I am exceptionally indebted to my wife, Mrs Ilva George (Germany) for her essential and extensive help in meiofauna sampling, sample treatment and sorting during our stay in Valdivia (Chile) from 1993–1995. Thanks are given to Mr Johannes Dürbaum (Germany), Dr Gritta Veit-Köhler (Germany), Prof Dr Horst Kurt Schminke (Germany) and Dr Matthias Gorny (Chile) for ceding material of several Paralaophontodes specimens. Mrs Karin Sindemark-Kronestedt (Sweden) kindly provided the type material of Laophontodes armatus Lang, 1936. Special thanks go to Dr Natalie Barnes (United Kingdom) for reviewing the English text of the manuscript and providing helpful comments. I am indebted to two anonymous reviewers for their very helpful and constructive comments and recommendations; two further anonymous reviewers provided helpful and constructive comments on a former version of the manuscript. The author’s stay in Chile (1993–1995) was financially supported by the German Academic Exchange Service DAAD (code no. 565/504/500/4); his stay in Punta Arenas (Chile) in the frame of the research cruise ANTARKTIS XIII/4–5 of German RV “Polarstern” in 1996 as well as his stay in Golfito (Costa Rica) in 2008 was financially supported by the Deutsche Forschungsgemeinschaft DFG (SCHM 352/18-1 and GE 1086/7-1, respectively).