Ctenocheloides attenboroughi Anker, 2010, n. gen.
Creators: name: Arthur Anker
Publisher: name: Zenodo
Year: 2010
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Callianassidae
Ctenocheloides
Ctenocheloides attenboroughi

description: Ctenocheloides attenboroughi n. gen., n. sp.
(Figures 1–8)
Type material
Holotype. Female (CL 4.15 mm), FLMNH UF Arthropoda 13902, Madagascar, Nosy-Bé, large bay east of Hellville, at CNRO station, 13.4069 S, 48.2917 E, low intertidal and subtidal, bottom: mud, silt, some rocks, extracted from a large piece of coral rubble cemented with mud and organic debris, collected at about 1.5 m, coll. A. Anker, 22 May 2008.
Description
Small-sized, relatively slender callianassoid. Carapace about the same length as first two abdominal somites combined. Frontal region (Figure 1 A) somewhat convex, without rostral spine, carina or any other median ridge; anterolateral projections moderate, obtuse; postfrontal area with low rounded prominence (Figure 1 D). Carapace with gastric region slightly elevated compared with cardiac region, latter with low rounded prominence (cardiac prominence); cervical groove well delimited, deep (Figure 1 E); linea thalassinica distinct, running very close to depressed lateral margin of dorsal oval (Figure 1 D, E); carapace flanks with distinct U-shaped groove close and extending to anterolateral margin, additional longitudinal-oblique groove arising from posterolateral margin (Figure 1 D); anterolateral margin below anterolateral projection deeply notched; branchiostegial margin somewhat elevated from carapace, fringed with long setae from deep anterolateral notch to above posterior ending of linea thalassinica (Figure 1 D).
Abdomen (Figure 2) moderately long; first abdominal somite longest, with some grooves laterally (Figure 2 A; see also Figure 1 G); tergite with anterior margin straight, not notched; second somite about 0.65 as long as first, without setal row on pleuron; posterior margin straight; third to fifth pleura similar in length, shorter than second somite, tergite of third and fourth somite with rows of moderately long plumose setae along posterior margin, more dense laterally; tergite of fifth somite with more irregular row of long plumose setae closer to anterior margin sixth somite subrectangular in dorsal view, with posterolateral constriction, without organised setal rows.
Eyestalks (Figure 1 A, B) almost reaching distal margin of first segment of antennular peduncle; lateral margin with shallow concavity posterior to cornea; anterior margin bluntly rounded; corneas distinctly convex laterally.
Antennular peduncle (Figure 1 A, B) extending to about mid-length of fourth segment of antennal peduncle; first segment concave dorsally, at least twice as long as second segment, latter half length of third segment; flagella longer than peduncle; dorsal flagellum thicker and slightly shorter than ventral flagellum, with 13 segments, distal four bearing anteriorly directed aesthetascs on ventral margin, distal three gradually narrower, terminal article very slender; ventral flagellum with long setae along ventral margin, usually grouped in pairs at distoventral end of each segment. Antennal peduncle (Figure 1 A, B) longer than antennular peduncle by half the length of its fourth segment; first segment with blunt lobe laterally; second segment with deep lateral furrow, distoventral lobe subacute; third segment elongate, longer than fourth and longer than combined lengths of first two segments; scaphocerite small, subacute distally (Figure 1 C); flagellum subequal in length to dorsal antennular flagellum. Epistome robust, without setae.
Mandible (Figure 3 A, B) with three-segmented palp, third segment rounded distally, fringed with setae; incisor process bearing essentially two teeth on cutting margin: one large subtriangular tooth centrally and one smaller tooth at ventral angle; molar process very short, partly fused with incisor, with two blunt processes. Maxillule (Figure 3 C) with two-segmented endopod, first segment longer than second segment; second segment curved distally, forming small hook; basal endite with row of robust spine-like setae along distal margin; coxal endite not particularly enlarged, rounded distally, with densely setose distal margin. Maxilla (Figure 3 D) with endopod narrower distally, with long plumose setae on ventral margin; basal and coxal endites deeply subdivided, their distal margins setose; scaphognathite rather narrow, without elongate seta on posterior lobe. First maxilliped (Figure 3 E) with moderately developed, rod-shaped endopod; basal endite densely setose distally; coxal endite distally with row of elongate setae, latter curved mesially; exopod broad, curved distomesially, longer than basal endite; epipod well developed, bilobed, ear-shaped. Second maxilliped (Figure 3 F) with elongate, slightly curved merus; ventral (flexor) margin densely furnished with elongate, flexible, plumose setae; carpus short, subtriangular; propodus subrectangular, about twice as long as wide, and half length of merus, with some long plumose setae on dorsal margin; dactylus short, subrectangular, slightly longer than wide, somewhat narrowed distally, approximately 0.4 times length of propodus, tip densely covered with serrate setae; exopod absent; epipod rudimentary; podobranch absent.
Third maxilliped (Figure 3 G–J) pediform, not operculate; endopod fringed with long setae on ventral margin; ischio-merus not particularly broadened; ischium approximately 2.5 times as long as wide in lateral view, ventral side strongly arcuate; ventromesial margin with crista dentata consisting of five irregular, subtriangular, blunt to subacute teeth; merus about 2.5 times as long as wide in lateral view, about the same length as ischium, ventrolateral margin with small subacute tooth at about 0.75 length of merus, ventromesial margin with large projecting tooth at about 0.75 length of merus, opposed to lateral tooth in ventral view (Figure 3 I); carpus vaseshaped, widening distally, slightly shorter than merus, unarmed, slightly concave ventroproximally; propodus subrectangular, slightly more than twice as long as wide in lateral view, about the same length as carpus; dactylus, elongate-oval, about three times as long as wide, 0.7 times as long as propodus, conspicuously narrower than propodus, increasingly more setose distally; exopod absent; arthrobranch small (Figure 3 J).
First pereiopods (chelipeds) somewhat unequal in size and asymmetrical in shape. Major cheliped (Figure 4) with ischium approximately four times as long as wide at base, somewhat widening distally, ventral margin armed with four small blunt teeth proximally and two much larger, projecting, distally pointed teeth more distally (Figure 4 A, B); merus oval-shaped, ventromesial margin with projecting, subacute tooth subdistally, ventral surface distally excavated; carpus short and wide, cupshaped; major chela suboval, longer than wide, not markedly compressed, ovoid in cross-section; palm smooth except for slight constriction on distodorsal margin; fingers elongate, about 1.2 times as long as palm, slender, tips strongly crossing when fingers closed; cutting edge of fingers with 26 (dactylus) and 28 (pollex) more or less strong teeth (Figure 4 C, D), proximal teeth minute; three teeth situated in distal half of pollex significantly longer and stronger than other teeth on pollex, most-distal of them strongest; similarly, four teeth situated on dactylus longer and stronger than other dactylar teeth, most-distal of them strongest; fairly large gap present subdistally on cutting edge of dactylus (Figure 4 D). Minor cheliped (Figure 5) smaller and shorter than major cheliped by about 70%; ischium and merus generally similar to those of major cheliped; carpus somewhat longer compared with that of major cheliped; minor chela generally similar to major chela except for smaller size and shorter fingers, about the same length as chela; cutting edges similarly pectinate, but with weaker and somewhat fewer, 25 (dactylus) and 24 (pollex) teeth; four teeth on pollex and five teeth on dactylus stronger than others (Figure 5 C).
Second pereiopod (Figure 6 A) stout; ischium short, without specific features; merus robust, subrectangular, approximately three times as long as wide at base, with ventral margin fringed with long flexible setae; carpus vase-shaped, widening distally, carrying long flexible setae distally on ventral margin; chela (Figure 6 B) with very short, subrectangular palm, wider than long, fingers much longer than palm, straight, forming small gap proximally when closed; pollex with minute teeth on proximal half. Third pereiopod (Figure 6 C) robust; ischium short; merus somewhat ovate, about 3.5 times as long as wide; carpus 0.6 length of merus, widening distally, distoventral margin furnished with tufts of long stiff setae; propodus subrectangular, about three times as long as wide, slightly longer than carpus; distodorsal margin with tufts of long slender setae; ventral margin furnished with long stiff setae, more slender, longer and more flexible setae, and stout spiniform seta at distal end, opposed to dactylus (Figure 6 D); dactylus stout, less than 0.5 length of propodus, slightly curved ventrally, subacute distally. Fourth pereiopod (Figure 6 E) somewhat more slender than third, with longer, stouter ischium; merus about 3.7 times as long as wide; carpus 0.7 length of merus, slightly widening distally, without long stiff setae; propodus subrectangular, at least three times as long as wide, subequal in length to carpus; distodorsal margin with tufts of long slender setae; ventral margin furnished with long stiff setae and stout spiniform seta at distal end, opposed to dactylus; dactylus moderately stout, about half the length of propodus, less curved than dactylus of third pereiopod, subacute distally. Fifth pereiopod (Figure 6 F) with all articles much more slender than those of third and fourth; ischium subrectangular; merus more than four times as long as wide; carpus about 0.7 length of merus, widening distally (better visible in Figure 6 G), without long stiff setae; propodus subrectangular, slender, 3.5 times as long as wide in lateral or mesial view (Figure 6 H), almost five times as long as wide in ventral view (Figure 6 F), distinctly longer than carpus; ventral margin furnished with long stiff setae on distal half and small, somewhat curved spiniform seta at distal end, below dactylus; dactylus relatively slender, about 0.4 length of propodus, concave proximally and curved mesially, tip subacute.
First pleopod of female (Figure 7 A) with short setae on protopod and along lateral margin of ramus; apex of ramus with three long plumose setae. Second pleopod of female (Figure 7 B) with both exopod and endopod fringed with plumose setae; endopod with rod-shaped appendix interna. Third (Figure 7 C) to fifth pleopods of female with exopods and uropods elongate-oval, densely fringed with plumose setae; endopods with stubby, rod-shaped projecting appendices internae (Figure 7 D). Male pleopods unknown. Uropod (Figure 7 E) with exopod and endopod ovate, both with low median elevation and fringed with very dense plumose setae; exopod distinctly expanded proximolaterally, with row of strong spiniform setae inserted on margin above fringing setal rows, extending from proximolateral margin to distomesial margin, distomesial spiniform setae longer compared with proximolateral ones; lateral incision not distinct.
Telson (Figure 7 F) about 1.2 times as long as wide at anterior margin, broadly triangular, lateral margin shallowly constricted at about 0.35 length from anterolateral angle; posterior margin rounded, without spine-like setae; long plumose setae present posterior to about mid-length of lateral margin, including around posterior margin; dorsal surface without distinct ridges, transversely depressed posteriorly to anterior margin; tufts of long setae or isolated setae present on dorsal surface, especially at posterior margin. Gill/exopod formula as summarised in Table 1.
Notes: Mxp1–3, first to third maxillipeds; P1–5, first to fifth pereiopods; Plb, pleurobranch; Arb, arthrobranch; Pod, podobranch; Ep, epipod; Ex, exopod; r, rudimentary; +, present; –, absent.
Size
Holotype, adult female and the only specimen presently known, at CL 4.15 mm, TL 19.80 mm.
Colour
Pale to dark brown (when covered with mud and organic debris), whitish when cleaned; cheliped chelae orange distally; ovaries bright yellow-orange (Figure 8).
Etymology
It is a great honour for the author to name this unique species after Sir David Attenborough, a famous British naturalist and presenter of numerous nature documentaries, including the spectacular “The Blue Planet – Seas of Life” (BBC 2001).
Ecology
The type locality is a relatively large bay fringed by mangroves and some tidal mudflats. In the shallows (less than 3 m deep), the bottom is fine silt or mud, with some rocks or pieces coral rubble, occasionally also sunken wood. The specimen was extracted from a deep crevice in a large piece of rubble cemented by clayish, somewhat sticky mud, collected at about 1.5 m; it was partly covered with mud particles and debris of possibly both organic and inorganic origin (Figure 8). Ctenocheloides attenboroughi n. gen., n. sp. is the shallowest ctenochelid ghost shrimp presently known.
Distribution
Presently known only form the type locality in Nosy-Bé, north-western Madagascar.
description: Published as part of Arthur Anker, 2010, Ctenocheloides attenboroughi n. gen., n. sp. (Crustacea: Decapoda: Axiidea: Ctenochelidae), a new ghost shrimp with pectinate claw fingers from Madagascar, pp. 1789-1805 in Journal of Natural History 44 (29) on pages 1792-1802, DOI: 10.1080/00222931003633219, http://zenodo.org/record/269871