Bermudacaris britayevi, Anker & Poddoubtchenko & Marin, 2006

Anker, Arthur, Poddoubtchenko, Denis & Marin, Ivan N., 2006, On the presence of the alpheid shrimp genus Bermudacaris Anker and Iliffe, 2000 (Crustacea: Decapoda: Caridea) in the Pacific Ocean, with description of a new species from Vietnam, Journal of Natural History 40 (27 - 28), pp. 1675-1686 : 1677-1684

Bermudacaris britayevi n. sp.

( Figures 1–4 )

Material

Holotype: female (specimen without appendix masculina), CL 3.3 mm, TL 11.7 mm, NHM 2006.1217, Vietnam, Nha Trang Bay , Tre Island, Dam Bay, intertidal, close to mangrove, with suction bait pump (‘‘yabby pump’’) from burrow of possibly callianassid host, coll. I. N. Marin, 4 June 2004.

Description

Body elongate ( Figure 1a ), not particularly compressed laterally, glabrous. Frontal margin with shallow emargination bearing broadly rounded median rostral projection ( Figure 1b ); orbital hoods and orbital teeth absent: eyes fully exposed in dorsal and lateral view ( Figure 1b, c ); pterygostomial angle rounded ( Figure 1c ); branchiostegial margin furnished with setae ( Figure 1a ); cardiac notch deep ( Figure 1a ). Eyestalks juxtaposed, without anteromesial tubercle; cornea modestly pigmented ( Figure 1b ). Ocellar beak not conspicuous. Epistomial sclerite with projecting subacute tooth ( Figure 1d ).

Antennular peduncle with second segment about 1.8 times longer than broad, longer than visible portion of first segment; stylocerite overreaching distal margin of first segment, tip acute ( Figure 1b, c ); ventromesial carina with acute tooth distally ( Figure 1e ); dorsomesial carina with curved spinules proximally ( Figure 1b, e ); lateral flagellum not distinctly biramous, with about five aesthetasc-bearing segments ( Figure 1c ). Antenna with basicerite bearing robust, acute ventrolateral tooth ( Figure 1c ); scaphocerite subrectangular, anterior margin of blade convex, extending slightly beyond distolateral tooth ( Figure 1b ); carpocerite reaching far beyond distal margin of scaphocerite ( Figure 1b, c ).

Mouthparts typical for genus. Mandible ( Figure 2a ) with two-segmented palp, proximal segment ventrodistally slightly expanded and protruding, furnished with setae, distal segment fringed with elongate setae; incisor process distally with five strong subtriangular teeth ( Figure 2b ); molar process distally with minute teeth and rows of short setae. Maxillule ( Figure 2c ) with bilobed palp, dorsal lobe without setae, ventral lobe with one thick seta ( Figure 2c ); ventral endite with about five stiff elongated spine-like setae mesiodistally ( Figure 2d ). Maxilla ( Figure 2e ) with narrow scaphognathite; endopod small, not segmented, without setae; dorsal endite with deep horizontal cleft ( Figure 2e ). First maxilliped ( Figure 2f ) with moderately developed caridean lobe; endopod two-segmented, with one thick seta distally ( Figure 2g ); exopod distally truncate; epipod irregularly ovate. Second maxilliped of typical form ( Figure 2h ); epipod rounded, bearing podobranch mesially, latter with five well-developed leaflets ( Figure 2h ). Third maxilliped ( Figure 2i ) pediform, slender; lateral plate of coxa with subacute posterior process ( Figure 2i, j ); antepenultimate segment somewhat flattened on ventral surface; penultimate segment about twice as long as wide, with dense row of moderately elongate setae mesially; ultimate segment slightly shorter than antepenultimate segment, tapering distally, with pairs of spines on dorsal surface starting anterior to mid-length and continuing to segment tip ( Figure 2i, k ); arthrobranch well developed ( Figure 2i ).

First pereiopods (chelipeds) ( Figure 3 ) subequal in size, symmetrical in shape [only left cheliped present in holotype, right cheliped of size approximately equal to that of left cheliped (I. Marin, personal observation) lost during collection], robust, enlarged compared to other pereiopods, carried extended with dactylus in ventrolateral position; coxa and basis unarmed; ischium with curved spines on distal and mesial margins ( Figure 3a, e, f ); merus stout, about 3.5 times as long as distal width, with row of spinules mesially ( Figure 3e ); carpus cup-shaped, with row of short stiff setae mesioventrally ( Figure 3c, e ); chela with palm smooth, subrectangular, compressed laterally ( Figure 3b– d ); fingers subequal in length, not gaping when closed, finger tips crossing; dactylus in ventrolateral position ( Figure 3a, b ), cutting edge unarmed; pollex armed with small irregular teeth on proximal two-thirds of cutting edge ( Figure 3d ); linea impressa, adhesive discs and snapping mechanism absent.

Second pereiopod slender, elongate ( Figure 4a ); ischium slightly longer than merus; carpus with five segments, segment length ratio approximately equal to 1.5:2:1:1:1.3 ( Figure 4a ); chela simple, as long as first carpal segment, fingers slighty shorter than palm. Third and fourth pereiopods similar; third pereiopod ( Figure 4b ) with unarmed ischium; merus more than three times as long as ischium and about twice as long as carpus, unarmed, convex on ventral and dorsal margins ( Figure 4b ); carpus not inflated, ventrodistally with one stiff elongate seta ( Figure 4b ); propodus about as long as carpus, ventral margin with five slender spines; dactylus elongate, conical, slightly curved, about half length of propodus ( Figure 4b ). Fifth pereiopod ( Figure 4c ) more slender than third and fourth pereiopods; ischium short, unarmed; merus about three times as long as ischium and 1.5 times as long as carpus, unarmed; carpus unarmed; propodus longer than carpus, ventral margin with three slender spines and distal pair of spines proximal to dactylus ( Figure 4d ), ventrolateral surface with rows of elongate setae ( Figure 4c ); dactylus about half as long as propodus, very similar to that of third pereiopod.

First to fifth abdominal somites I–V with posterolateral angles of pleura rounded to slightly angular ( Figure 1a ); sixth somite without articulated plate at posteroventral angle, posterior projection subrectangular; preanal plate posteriorly rounded. Second pleopod with appendix interna only. Uropods distinctly exceeding telson ( Figure 1a ); lateral lobe of protopod sympodite distally with acute tooth ( Figure 1f ); endopod and exopod subequal in length; (exopod) with diaeresis distinctly curved at about two-thirds of its length thus forming two subtriangular teeth ( Figure 1f ); lateral spine rather small, adjacent tooth small, subacute ( Figure 1f ). Telson ( Figure 1g ) distinctly tapering distally, almost subtriangular, proximal width about four times width of posterior margin; dorsal surface with two pairs of spines, one pair at mid-length and another pair at about three-quarters length of telson ( Figure 1g ); posterior margin straight, with two pairs of slender posterolateral spines, lateral much shorter than mesial (broken on left side, cf. Figure 1g ), median portion between spines with four elongate setae; anal tubercles absent. Gill/exopod formula as given for genus.

Size

The carapace length of the unique specimen is 3.3 mm; the total length is about 11.7 mm.

Colour

Semi-transparent white.

Etymology

We are pleased to name this species after Dr Temir Alanovich Britayev, Head of the Laboratory of Ecology and Morphology of Marine Invertebrates, A. N. Severtzov Institute of Ecology and Evolution of the Russian Academy of Science in Moscow; with his continuing support numerous interesting alpheid shrimps, including the present new species, were collected in Nha Trang Bay from 2003 to 2005.

Habitat

The single specimen was collected from a burrow presumably of a callianassid host on shallow tidal sand-mud flat with fringing mangroves. The host identity remains unknown. Another question that remains unanswered is whether B. britayevi n. sp. is an obligate or (more likely) only occasional burrow commensal. Other commensal animals collected at Dam Bay sand-mud flats were the alpheid shrimp, Leptalpheus cf. pacificus Banner and Banner, 1974 (Anker et al., in preparation), and the laomediid mud shrimp, Naushonia sp. (undescribed species; Dworschak et al., in preparation), both associated with burrows of the callianassid ghost-shrimp, Glypturus cf. armatus (A. Milne-Edwards, 1870); two further alpheid shrimps, Salmoneus rostratus Barnard, 1962 and S. alpheophilus Anker and Marin, 2006 , both associated with burrows of a larger alpheid, Alpheus cf. rapacida de Man, 1909 ( Anker and Marin, 2006); as well as large, unidentified amphinomid polychaetes.

Distribution

Presently known only from the type locality, Nha Trang Bay , Vietnam .

Remarks

Bermudacaris britayevi n. sp. differs in many features from the type species, B. harti , e.g. in the presence of a shallow emargination on the frontal margin of the carapace; the much more robust antennular peduncle, third maxilliped, chelipeds, and third to fifth pereiopods; the more adjacent and pigmented eyestalks; the posteriorly elongated lateral plate on the coxa of the third maxilliped; the more conspicuous podobranch on the second maxilliped; and the absence of a ventral spine on the ischium of the third to fifth pereiopods (cf. Anker and Iliffe 2000). On the other hand, B. britayevi n. sp. appears to be closely related to B. australiensis , from which it may be separated by the shape of the frontal margin of the carapace; the juxtaposed eyestalks (versus somewhat divergent in B. australiensis ); the more developed podobranch on the second maxilliped; the distinctly longer stylocerite (overreaching distal margin of antennular segment in B. britayevi n. sp. versus not reaching this margin in B. australiensis ); the cutting edges of the cheliped fingers armed with small irregular teeth (versus unarmed in B. australiensis ); the dorsal lobe of the maxillular palp lacking seta; the incisor process of the mandible bearing stronger teeth; and the better developed diaeresis on the uropodal exopod (cf. Anker and Komai 2004).

As discussed by Anker and Komai (2004), the undescribed species from Toliara, Madagascar, misidentified by Ledoyer (1970) as ‘‘ Automate dolichognatha (de Man, 1888) ’’, possibly belongs to Bermudacaris or at least to a closely related genus. Unfortunately, the whereabouts of Ledoyer’s material remain unknown ( Anker and Komai 2004). Bermudacaris britayevi n. sp. differs from the Toliara species by the broadly rounded rostral projection (versus small triangular rostrum in Ledoyer’s specimen) and the shape of the cheliped chela, especially the armature of the fingers (with small irregular teeth in B. britayevi n. sp. versus with stout molar-shaped tooth on the pollex in Ledoyer’s specimen). Remarkably, the frontal regions of B. britayevi n. sp. and of Ledoyer’s unnamed species appear to be closer to the configuration found in some species of Automate de Man, 1888 , than to B. harti and B. australiensis .

Table I summarizes the most important features distinguishing the three presently known species of Bermudacaris , as well as the undescribed species illustrated by Ledoyer (1970). According to Table I, B. harti appears to be more distantly related to B. britayevi n. sp. and B. australiensis . The latter two species have indeed very similar chelipeds, third pereiopod, as well as second and third maxillipeds. Therefore, it is possible that the two Atlantic forms associated with anchialine stygobitic habitats, B. harti and Bermudacaris sp. from Mallorca (cf. Gràcia et al. 2003), may be also generically different from the Indo-West Pacific forms, B. britayevi n. sp., B. australiensis , and Ledoyer’s species, all being associated with intertidal and subtidal marine habitats. However, we defer from further speculations on generic assignments, awaiting the description of the stygobitic species from Mallorca (cf. Gràcia et al., 2003; D. Jaume, personal communication) and the recollection and description of the enigmatic species illustrated by Ledoyer (1970).

Figures

Figure 1. Bermudacaris britayevi n. sp., holotype (NHM 2006.1217). (a) General body without cephalic and thoracic appendages, lateral view; (b) frontal region, dorsal view; (c) same, lateral view; (d) epistomial sclerite near ventral base of antennule; (e) antennule, first two segments of peduncle, lateral view; (f) uropod, dorsal view; (g) telson, dorsal view. Scale bars: 1 mm.

Figure 2. Bermudacaris britayevi n. sp., holotype (NHM 2006.1217). (a) Mandible, mesial view; (b) same, incisor process; (c) maxillule, lateral view; (d) same, ventral endite, mesial view; (e) maxilla, lateral view; (f) first maxilliped, lateral view; (g) same, posteromesial view of endopod and proximal portion of exopod; (h) second maxilliped, lateral view; (i) third maxilliped, lateral view; (j) same, detail of coxa; (k) same, ultimate segment, dorsomesial view. Scale bar: 1 mm.

Figure 3. Bermudacaris britayevi n. sp., holotype (NHM 2006.1217). (a) Left cheliped, dorsomesial view; (b) same, ventrolateral view; (c) same, chela and carpus, mesial view; (d) same, chela enlarged, lateral view; (e) same, ischium, merus, and carpus, mesial view; (f) same, ischium, ventral view. Scale bars: 1 mm.

Figure 4. Bermudacaris britayevi n. sp., holotype (NHM 2006.1217). (a) Second pereiopod, lateral view; (b) third pereiopod, dorsal view; (c) fifth pereiopod, lateral view; (d) same, propodus and dactylus, mesial view. Scale bar: 1 mm.