Research Article |
Corresponding author: David J. Wildish ( wildishd@dfo-mpo.gc.ca ) Academic editor: Matthias Glaubrecht
© 2014 David J. Wildish.
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:
Wildish DJ (2014) New genus and two new species of driftwood hoppers (Crustacea, Amphipoda, Talitridae) from northeast Atlantic and Mediterranean coastal regions. Zoosystematics and Evolution 90(2): 133-146. https://doi.org/10.3897/zse.90.8410
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A new specialist driftwood talitrid from the Swale, U.K., is figured and described as Neotenorchestia kenwildishi gen. n., sp. n. A further new driftwood talitrid, Macarorchestia pavesiae sp. n., is figured and described from coastal regions in the Adriatic Sea. Orchestia microphtalma Amanieu & Salvat, 1963 from the Atlantic coast of France is re-designated as Macarorchestia microphtalma (Amanieu & Salvat, 1963). A key is provided for the known species of driftwood talitrids in northeastern Atlantic and Mediterranean coastal regions.
Neotenorchestia kenwildishi gen. n., sp. n., Macarorchestia pavesiae sp. n., Macarorchestia microphtalma (Amanieu & Salvat 1963) comb. n.
Driftwood specialist hoppers are a rare, difficult to find, ecological group of Talitridae which are virtually confined to rotting driftwood where they live in galleries, consuming rotting driftwood and reproducing with relatively small broods (1 to 19 ova per brood in the Macarorchestia so far described). The ova are incubated in the brood pouch formed by the oostegites on peraeon segments 2 through 5 and hatch as juvenile forms. Because talitrids have no larval stage their dispersal, particularly to distant oceanic islands, was seen as problematic. The general view was that some form of passive rafting dispersal was involved
Currently known driftwood taxa (
As a result of molecular studies of Macarorchestia remyi it was suggested that two genetically distinguishable forms: one centred in the Tyrrhenian and the other in the Adriatic Sea were present (
Slides were prepared as temporary mounts without staining and after dissecting mouthparts and limbs. Some were prepared as permanent mounts by Sara LeCroy, after staining with lignin pink and permanently mounted in CMCP-10 (Master’s Company, Inc.).
Photographs of limb parts were made with a Carl Zeiss photomicroscope and digital Canon 990 camera. Adobe Photoshop (version 7.0), Illustrator (version 11.0) and a Wacom tablet were used to draw limb parts and prepare figs, essentially as outlined in
Macarorchestia
M. martini Stock, 1989
Currently includes five species: M. martini, M. roffensis, M. remyi, M. pavesiae sp. n., M. microphtalma (Amanieu & Salvat, 1963) new comb.
As in
M. martini:
Male holotype and 8 females (allotype and paratypes) on loan from Zoological Museum of Amsterdam, Amsterdam, the Netherlands (AMPH. 108.57). Collected by J. Stock on 2 August, 1987 from Gruta das Agulhas in Porto Judeus on the island of Terceira, Azores archipelago.
Known only from the type locality on the island of Terceira.
Not mentioned by
This is the type species and smallest Macarorchestia.
M. roffensis:
Male holotype (BMNH 1968:64), one female allotype (BMNH 1968:65) and 416 paratypes of all life history stages (BMNH 1968:66). Collected by D.J.Wildish(DJW) in August 1968, 0.2 km upstream from Chatham Ness in Limehouse Reach, Medway estuary, near Rochester, Kent, U.K.
Besides the type locality one other locality in the Medway estuary was found in 1968 with a few specimens in a driftwood log by DJW. The location was ~ 0.6 km upstream from the old Rochester Bridge in Tower Reach on the eastern shore. A few specimens collected by DJW in 1999 from the Swale, in Ferry Reach ~ 0.5 Km northwest of Kingsferry Bridge on the mainland shore.
Absent.
Remarks This is the second smallest Macarorchestia. The type locality was destroyed during reclamation of Frindsbury marsh as an industrial estate.
M. remyi:
Two males, 4 females, 1 juvenile (Crust. 25468) ZMB Museum für Naturkunde, Berlin. Collected by A. Schellenberg from a seashore cave at St. Barthelemy, Corisca. A total of 47 individuals (combined sample) of all life history stages, including females with ova, collected by L. Pavesi on 20 January and 15 April 2007 at Principina a Mare, Tyrrhenian Sea, Italy. Sample location co-ordinates: 42°41'18"N, 10°59'53"E. A further sample collected at Principina a Mare by L. Pavesi on 24 April 2011 consisted of 28 individuals of all life history stages, including females with ova. One individual from Corfù Island (Ionian Sea, Greece) collected by L. Pavesi in 2007 (Destructively used in DNA analysis).
Besides the locations found by L. Pavesi for this species, published records include that of
Absent.
Remarks This is the second largest Macarorchestia. In recent times the type locality has been destroyed by cleaning beaches for the benefit of tourists (L. Pavesi, pers. comm.).
M. pavesiae:
Holotype male of 8.0 mm TBL (NHMUK 2014. 408) and allotype female of 7.5 mm (NHMUK 2014. 409) collected by L. Pavesi on 31 October, 2006 at Lesina, Adriatic Sea, Italy. 13 paratypes collected on the same date (NHMUK 2014. 410 - 419). Paratypes have also been deposited in the Natural History Museum, Verona and Museum at Rome University, Rome, Italy by L. Pavesi.
Lesina, Adriatic Sea, Italy (41°54'11"N, 15°26'50"E).
Other
17 individuals collected by L.Pavesi in April 2006 at Varano, Adriatic Sea, Italy (41°55'12"N, 15°47'29"E).
M. pavesiae sp. n. is distinguished from its close relative, M. remyi, by its smaller size, sexually dimorphic second antennal flagellum articles in adult females and absence of sexual dimorphism in pleopod rami.
Based on male paratypes: total body lengths in the range of 8.0 to 6.7 mm. Figs
Head deeper than long (1: 0.7); eyes small, round, less than half the head length. Antenna 1 flagellum 5–articulate with tip just exceeding the junction of peduncle segments 4 and 5 of antenna 2. Antenna 2 short, flagellum 12–articulate, peduncle not incrassate.
Mouthparts. Lower lip with lateral lobes, minute setae on the inner clefts. Left mandible with a 4-dentate lacinia mobilis and large molar process. Right mandible with the tip of the dentate incisor bilobed, 6–dentate lacinia mobilis. Maxilla 1 inner fig narrow with 2 terminal plumose setae, inner margin with long, fine setae; outer fig with a palp, apical robust setae curved and serrated on the inner edge. Maxilla 2 both figs equal in size, inner with a single, plumose seta, with shorter robust setae on the distal edge; outer fig with simple robust setae. Maxilliped inner figs with 3 stout teeth apically, inner, outer and palp distal edges covered with robust setae; palp large and 3–articulated.
Peraeon. Gnathopod 1 weakly subchelate with palmate lobes on propodus and carpus; dactylus as long as propodus lobe; the largest robust setae are present on the posterior edge of the merus. Gnathopod 2 subchelate with propodus and dactylus massively enlarged, dactylus drawn out in a short, blunt tip, its inner surface lacking fine setae. Ventral edge of each coxal fig rounded and with fine robust setae. Peraeopods 3 to 5 short, peraeopods 6 and 7 longer, the latter just longer than uropod 1. Peraeopods 3 and 4 lack a dactylus notch (“pinched unguis”). Peraeopods 6 and 7 not sexually dimorphic in merus and carpus. Six distinctive tufts of long, slender setae originating from the propodus of peraeopod 7 as follows: anterodistal (2 setae), distal (6 setae), anterior side of peraeopod near the first insertion of robust, bifid-tipped setae (4 setae), then on the posterior side of the peraeopod: first insertion of robust, bifid-tipped setae (2 setae), second (4 setae) and third (3 setae). The maximum length of the longest seta from the distal tuft was 144 µm (Fig.
Pleosome. Pleopod basis not reduced and with a pair of hooked coupling spines, robust setae and fine marginal setae absent. All rami are are shorter than the basis. The second pleopod rami have 3 articles each bearing a pair of long, plumose setae: exopod –7, endopod -5.
Urosome. In uropods 1 and 2 the inner and outer rami are of similar length, with 2–4 apical robust setae and 1 or 2 inter-ramal robust setae, basis with 1 or 2 dorsoventral, robust setae distally. Uropod 3 basis longer than the ramus and with 2 large, robust setae dorso-laterally. Smaller robust setae at the ramus tip but lacks inter-ramal robust setae. Telson with a mid-dorsal groove and 6–7 dorso-lateral robust setae on each lobe.
Bbased on non-breeding adult female paratype of 7.3 mm total body length.
Gnathopod 1 without palmate lobes on propodus and carpus. Gnathopod 2 basis slender and with weak robust setae. Palmate lobes present on merus, carpus and propodus, dactylus small (described as “mitten-shaped”gnathopod 2). Pairs of non-ovigerous oostegites on peraeopods 2 to 5. Adult females greater than 7.5 mm body length with no more than 11 antennal flagellum articles (versus up to 13 in males). The 6 tufts of long, simple setae on the propodus of peraeopod 7 in males compares with 2 tufts, of sparser and shorter length setae in females.
Absent.
The name honours Dr. Laura Pavesi who originally discovered and collected the new species during graduate studies at the University of Rome, Italy.
There are three known locations for this species on the shores of the Adriatic Sea and one on Corfú Island, Ionian Sea.
M. microphtalma:
Male holotype (No. 5-1963) and paratypes in the Museum National d’Histoire Naturelle, Paris. Collected in 1962 by Mr. C. Caussanel from Cap Ferret Point near Arcachon on the Atlantic coast of France. Paratypes also in L’Institut de Biologie Marine at Arcachon. Collection by DJW in the type locality on 11th September 1967 and deposited in the Natural History Museum, London (BMNH 1967 10.6.1–75).
M. microphtalma is distinguished from M. remyi and M. pavesiae sp. n., by:
- Sexually dimorphic tufts of long, slender, simple setae from the propodus of peraeopod P7, with no tuft at anterodistal position and 4 tufts on the posterior side of the propodus in males, versus a tuft at anterodistal position and 3 tufts on the posterior side of the propodus in males of M. remyi and M. pavesiae sp. n. (Fig.
- its larger size, and
- lack of sexual dimorphism in pleopod and second antennal characters. Pleopod sexual dimorphism was discovered by
Known from the
and 3 other locations further south on the French Atlantic coast (
Absent.
Remarks The largest species of Macarorchestia.
Orchestia:
Orchestia gammarellus (Pallas, 1766).
Since the erection of Orchestia Leach, 1814 the genus has been uncritically used to include many new species from around the World. In more recent times genera have been split off from Orchestia including: Platorchestia by
Taking only Orchestia species which occur within this newly defined geographic range and excluding those outside it, synonyms, and where the taxonomic or ecological status is unclear (inclusive of O. kosswigi Ruffo, 1949–which is figured and described in
An interim diagnosis is provided based on the type species, O. gammarellus from the Medway estuary, U.K., as listed in Table
Adult total body length up to 22 mm; dorsal pigment patterns present; eyes medium in size, approximately one quarter of head length; antenna 1 flagellum just reaching antenna 2 peduncle of article 4; antenna 2 sexually dimorphic, peduncle slightly incrassate in adult males and without ventral fig on peduncle article 3; upper lip without robust setae; mandible left lacinia mobilis 4 dentate; maxilliped palp 3 articulate, article 2 with well developed medial lobe; gnathopod 1 of male subchelate with palm equal to dactyl, carpus and propodus free and with rounded lobes covered with palmate setae; gnathopod 1 of female parachelate, without lobes on carpus and propodus; gnathopod 2 of male strongly subchelate, merus and carpus free, dactylus with blunted tip and is half the length of the enlarged propodus; gnathopod 2 of female, ovigerous oostegite long and wide with many, long, simple, marginal setae, basis expanded anteriorly; peraeopods 3–7 cuspidactylate; peraeopods 5–7 lack slender setae lining the anterior margin of the dactyl; peraeopod 7 sexually dimorphic, adult males with merus and carpus enlarged; distinctive tufts of long simple setae on propodus of peraeopod 7 absent in both sexes; pleon segments 1–3 lacking vertical slits; pleopod rami slightly, or not, reduced; uropods without apical, spade-like robust setae, uropod 1 not sexually dimorphic, peduncle lacking well developed dorsolateral robust setae distally, outer ramus with marginal robust setae, uropod 2 rami equal in length, uropod 3 ramus shorter than peduncle; telson apically notched with 6–8 robust setae per lobe and shorter than uropod 3.
Ecological habitats occupied by species of Orchestia which are listed in WoRMS Editoral Board (2013) available from: World Register of Marine Species, http://www.marinespecies.org, accessed in 2013-06-26, and occurring in the northeast Atlantic (including offshore islands), Mediterranean and Black Sea region.
Marine/estuarine supralittoral wrack | Marine/estuarine eulittoral wrack | Freshwater supralittoral wrack | Terrestrial rain forest leaf litter | Marine driftwood |
---|---|---|---|---|
gammarellus | mediterranea | cavimana | chevreuxi | microphtalma |
stephenseni | aestuarensis | monticola | guancha | |
montagui | stocki | |||
canariensis | ||||
gomeri |
Ecological habitats and proposed generic groupings of species listed in Table
Genus | Marine/estuarine supralittoral wrack | Marine/estuarine eulittoral wrack | Freshwater supralittoral wrack | Terrestrial rain forest leaf litter |
---|---|---|---|---|
Orchestia | gammarellus | |||
Genus A | mediterranea ?aestuarensis | |||
Genus B | stephenseni montagui ?(xylino) | |||
Cryptorchestia | cavimana | |||
Genus C | ?(monticola) | |||
Genus D | ?guancha ?(gomeri) ?(canariensis) ?(stocki) | |||
Genus E | ?(chevreuxi) |
Neotenorchestia:
Neotenorchestia kenwildishi gen. sp. n. n.
Monotypic.
As in Orchestia and specifically similar to Orchestia mediterranea A. Costa 1853 except for:
- lack of dorsal pigment patterns (versus dorsal pigment patterns in O. mediterranea as in Wildish, 1987).
- smaller size by neoteny (largest total body length estimated to be 12 to16 mm, versus up to 20 mm in O. mediterranea)
Very similar to Orchestia mediterranea A. Costa 1853 and if characterization is limited to conventional morphological methods this species can easily be misidentified as a juvenile O. mediterranea. The use of relative growth methods and regression fitting predictions as found in
Refers to the origin of the new genus by a form of neoteny and combination of the stem of this word with the genus Orchestia to which it is closely related.
Summary of morphological and molecular data available for species of Macarorchestia. *
Species | Lmnd lacinia mobilis dentition | Numbers of setae in tufts on male propodus of P7 Distal Anterodistal | Number of tufts on posterior side of male propodus of P7 | Mt DNA COI** |
M. microphtalma | 4 | 6 0 | 4 | ? |
M. roffensis | 4 | 2 0 | 0 | Yes |
M. martini | 5* | ? ? | ? | Yes |
M. remyi | 4-5 | 6 2 | 3 | Yes |
M. pavesiae sp. n. | 4 | 6 2 | 3 | Yes |
N. kenwildishi:
Holotype–immature male of 7.2 mm total body length (NHMUK 2014. 397) and slide preparation from this individual (NHMUK 2014. 397). Nine juvenile paratypes (NHMUK 2014. 398 - 406) and 2 immature females (destructively sampled for temporary slide mounts and mtDNA analysis) removed from a cast-up driftwood log resting at the base of the seawall in the Enteromorpha zone by K.J. Wildish. The driftwood log had been tethered to an old cattle fence on the shore, so it could not float away. It was sampled on 14th June 2011, 23rd July 2011 and 13th August, 2011 from the Swale, near Kingsferry Bridge, U.K.
Approximately 0.5 km west of Kingsferry Bridge, The Swale on the mainland shore in a single rotting driftwood log (~ 3 × 0.5 × 0.5 m) determined to be of Douglas fir by Dr. P. Gasson, Kew (
Unknown, the largest found was an 8.9 mm TBL immature female. Mature adults predicted by relative growth methods to be 12 to16 mm total body length (
N. kenwildishi sp. n., can readily be distinguished from other driftwood hoppers of the genus Macarorchestia by its medium size eyes (versus small) and unreduced pleopods (rami sub-equal to basis, versus rami shorter than basis).
Based on immature male holotype of 7.2 mm total body length. Figs
Head deeper than long (1: 0.5); eyes medium/large, round and greater than half the head length. Antenna 1 flagellum 4-articulate. Antenna 2 flagellum 13-articulate. Peduncle not incrassate.
Mouthparts. Upper lip with minute setae on the apical margin. Lower lip deeply cleft and with minute setae on the inner face. Maxilla 1 inner fig slim and with two terminal, plumose setae; inner margin with long fine setae; outer fig with a vestigial palp, apical robust setae curved inwards, some simple and others serrated on the inner edge. Maxilla 2 with inner fig subequal to the outer, inner with a single, plumose seta and fine marginal setae below it; both inner and outer figs with long, simple robust setae which curve inwards. Left mandible with a 4-dentate lacinia mobilis, 6-dentate incisor, strong molar process and setose accessory blades. Maxilliped with 3 strong apical teeth on the inner fig; inner, outer and palp edged with simple, robust setae; palp large and 3-articulated.
Peraeon. Gnathopod 1 weakly subchelate, palmate lobes on propodus and carpus. Gnathopod 2 weakly subchelate with dactylus shorter than the propodus lobe; palmate lobes on propodus, carpus and merus. Peraeopod 3 lacks a dactylus notch (“pinched unguis”), but this is present in an immature female. Peraopod 5 shorter than peraeopods 6 and 7, the latter not sexually dimorphic in the immature male.
Pleosome. Pleopods large and well developed, with 6–7 ramal segments in the endopod, 8 segments in the exopod; rami subequal to basis with paired coupling spines on the inner, distal margin of the basis; 6 simple setae present on the basis of pleopod 1.
Urosome. Uropod 1 rami subequal to peduncle. Peduncle with 2 rows of 2 robust setae. Terminal setae on each ramus consists of 1 large and 1 or 2 smaller robust setae. 3 interamal robust setae on inner and 2 on outer ramus.
Based on immature female of 8.9 mm total body length.
In the absence of sexually mature males and females the only unique female characters found were: absence of palmate lobes on propodus and carpus of gnathopod 1, presence of pinched unguis on peraeopod 3, and presence of small, rudimentary oostegites on coxae of peraeopods 2–5.
The name honours Kenneth J. Wildish who discovered and collected the new taxon in the Swale during the summer of 2011.
Absent.
Known only from the type locality.
1 | Medium size eyes and pleopod rami basis length | N. kenwildishi sp. n. |
– | Small eyes and pleopod rami < basis length | 2 |
2 | Maximum adult size (TBL < 8 mm), female TBL > male | 3 |
– | Maximum adult size (TBL > 8 mm), male TBL ≥ female | 4 |
3 | Third pleopod exopod length ratio > 0.16 | M. martini |
– | Third pleopod exopod length ratio < 0.16 | M. roffensis |
4 | Maximum adult size (TBL = 15 mm), male TBL > female | M. microphtalma |
Lacks sexual dimorphism in A2 and pleopods | ||
Males with no tuft at anterodistal and 4 tufts of long, simple setae on posterior edge of of P7 propodus | ||
– | Maximum adult size (TBL < 13 mm), male TBL ≤ female | 5 |
With sexual dimorphism either in pleopods or A2 flagellum articles | ||
Males with a single tuft at anterodistal and 3 tufts of long, simple setae on posterior edge of P7 propodus | ||
5 | Adult male TBL > 8 mm fit: y = 0.050x + 0.159 | M. remyi |
– | Adult male TBL > 8 mm fit: y = 0.026x + 0.024 | M. pavesiae |
– | Adult female TBL > 7.5 mm fit: y1 = 0.585x + 6.995 | M. remyi |
– | Adult female TBL > 7.5 mm fit: y1 = 0.130x + 9.248 | M. pavesiae |
(where × = TBL, y = Pl3 Ex L, and y1 = A2 FA) |
The following arguments were considered in deciding how to name the unknown taxon. Relative growth data was available to show that the unknown taxon fundamentally differed from juvenile Orchestia mediterranea (
- being slower growing with a reduced terminal moult size,
- sexualization beginning at an earlier moult stage and with fewer moult stages per life history, and
- dorsal pigment patterns being absent.
The first two of these three phenotypic characters are described as neotenous dwarfism and are the basic adaptations possessed by all driftwood specialist talitrids of the genus Macarorchestia Stock. Because the unknown taxon clearly does not belong to Macarorchestia: by possession of fully developed eyes and pleopods, by COI divergence differences (
On the other hand molecular evidence suggests that the differences between the unknown taxon and O. mediterranea are small (
Pragmatically, and in the absence of conclusive molecular data, it is considered prudent to remove the unknown taxon from Orchestia, a supralittoral wrack generalist genus and create a new driftwood specialist genus: Neotenorchestia for the unknown taxon. Finding adult males and females of the new genus is needed to complete the description and diagnosis of the new taxon.
Inclusive of the taxonomic actions taken above brings the total genera of driftwood talitrids to three: Macarorchestia
The scarce locality records for each species documented here suggest either rareness and/or that they are difficult to find on shores of the northeast Atlantic and Mediterranean seas. Further evidence for this is that 2 of the 6 driftwood taxa dealt with here are known only from the type locality and the rest from only a few locations. A problem for future discoveries of driftwood talitrids is that the habitats are fast being destroyed by human activities. Documented examples include the destruction of the type locations for two species as mentioned above.
Both Macarorchestia and Neotenorchestia gen. n. probably originated from ancestors that were larger and faster growing. The evolutionary process in these genera involves reductions in metabolic and growth rates as well as sexualization occurring at an earlier moult number (neotenous dwarfism). A recent, common ancestor gave rise to modern O. mediterranea and N. kenwildishi gen. n., sp. n., which is consistent with morphological (relative growth) and molecular genetic studies (
1. roffensis --- martini
2. remyi --- pavesiae sp. n.
evolution involves further neotenous dwarfism. Thus taxa to the left are larger and plesiomorphic, whereas those to the right are smaller and apomorphic. Neotenous dwarfism of this kind in driftwood talitrids poses a special challenge to taxonomy because many of the slope values between pairs of species are isometric. In these cases only regression constants, or plots, can be used to separate two species populations. Isometric relative growth is rare within the Amphipoda and where it does occur ratios cannot be used to express the relative growth differences and recourse to regression predictions appears to be the only way to handle the differences due to neotenous dwarfism.
Permanent slides of limb and mouth parts prepared by Sara LeCroy (Gulf Coast Research Lab, University of Southern Mississippi) of four species of Macarorchestia identified possible, taxonomically important, morphological differences between groups 1 and 2 as defined in the preceeding paragraph. Thus the left mandible lacinia mobilis in Macarorchestia appeared to be predominantly 4-dentate (Table
In considering current data of Table
- of missing data as indicated by question marks in Table
- The left mandible lacinia mobilis is 5 dentate according to
Further molecular and morphological studies are needed to resolve the subgeneric status of Macarorchestia.
Thanks to Sara E. LeCroy for preparing permanent slides of Macarorchestia and the unknown taxon, Dr. Laura Pavesi and Kenneth J. Wildish for help in sampling and Dr. Dirk Platvoet (Zoological Museum, Amsterdam) and Miranda Lowe (Natural History Museum, London) for loaning type and other Macarorchestia material. I thank Dr. H. Morino and Mr. J. Valentine for improving earlier versions.