Athanopsis gotoi, Anker, Arthur, 2012

Anker, Arthur, 2012, Notes on the Indo-West Pacific shrimp genus Athanopsis Coutière, 1897 (Crustacea, Decapoda, Alpheidae), with the description of a new species associated with echiurans (Annelida, Thalassematidae), Zootaxa 3307, pp. 48-61 : 55-60

publication ID	https://doi.org/ 10.5281/zenodo.215146
DOI	https://doi.org/10.5281/zenodo.6178252
persistent identifier	https://treatment.plazi.org/id/039B87C5-FF95-DF00-FF00-E0F52BC53964
treatment provided by	Plazi
scientific name	Athanopsis gotoi
status	sp. nov.

Treatment

Athanopsis gotoi View in CoL sp. nov.

Figs. 5 View FIGURE 5 , 6 View FIGURE 6 , 7 View FIGURE 7 C, D

Type material. Holotype: ovigerous female (cl 5.5 mm), MNHN-IU-2011-2010-4101, Japan, Kagoshima Prefecture, Amami-Oshima Island, Edateku, 28.17'N, 129.13'E, gravel and coral sand flat exposed at extreme low tide, under rocks, with Ochetostoma erythrogrammon , leg. R. Goto, 15 May 2010. Paratype: ovigerous female (cl 5.7 mm), CBM-ZC 10620, Japan, Okinawa Prefecture, Okinawa Island, Nago, Awa, depth 6 m, under rocks, with echiuran (Ochetostomatinae), leg. Y. Yamada, 16 August 2009.

Additional material examined. 1 female (cl 4.6 mm), RMNH D49180, Indonesia, Talaud Islands, Beo Island, Snellius Expedition, sta. 29, 14-21 June 1930.

Description. Small-sized alpheid shrimp (cl 4.6–5.7 mm). Carapace glabrous, not setose, markedly domed ( Fig. 5 View FIGURE 5 C). Rostrum well developed, laterally compressed, straight, as long as broad at base, with shallowly concave lateral margins; tip rounded in lateral view, subacute in dorsal view, overreaching mid-length of second article of antennular peduncle; rostral carina absent ( Fig. 5 View FIGURE 5 A, B). Extracorneal teeth relatively small, subtriangular, distally blunt, reaching distinctly beyond anterior margin of cornea ( Fig. 5 View FIGURE 5 A, B). Pterygostomial angle slightly protruding anteriorly, rounded; cardiac notch deep ( Fig. 5 View FIGURE 5 B, C).

Pleura of first to fourth abdominal somites rounded posteroventrally; fifth pleuron with blunt posteroventral angle; sixth somite with large articulated triangular flap. Telson widest at proximal third, distally tapering; dorsal surface with two pairs of small spiniform setae, situated at some distance from lateral margin, at about 0.5 and 0.75 telson length, respectively; posterior margin slightly convex, with two pairs of slender spiniform setae at each lateral angle, mesial about three times as long as lateral ( Fig. 5 View FIGURE 5 I, J).

Eyes completely concealed in dorsal and lateral views; cornea well pigmented, occupying most of terminal portion of eyestalk ( Fig. 5 View FIGURE 5 A, B).

Antennular peduncle stout; stylocerite blunt distally, reaching to 0.7–0.8 length of second article ( Fig. 5 View FIGURE 5 A); ventromesial carina with very strong, anteriorly produced tooth ( Fig. 5 View FIGURE 5 D); second article shorter than wide; lateral flagellum biramous, fused portion composed of three articles; accessory ramus with at least four tufts of aesthetascs ( Fig. 5 View FIGURE 5 B). Antenna with stout basicerite ending in large subacute tooth distoventrally; scaphocerite exceeding end of antennular peduncle, blade ovate, broad; small distolateral tooth exceeding anterior margin of blade; carpocerite about the same length as scaphocerite ( Fig. 5 View FIGURE 5 A, B, E).

Mouthparts not dissected, typical for genus in external view. Third maxilliped with coxa bearing subacute lateral plate above mastigobranch; antepenultimate article flattened, somewhat broadened distally; penultimate article more than twice as long as wide proximally; ultimate article narrower than penultimate, tapering distally, furnished with transverse rows of thick serrulate setae, tip with at least two stout spiniform setae ( Fig. 5 View FIGURE 5 F).

Chelipeds very asymmetrical in shape and unequal in size; carried folded when not in use ( Fig. 6 View FIGURE 6 ). Major cheliped greatly enlarged, robust; basis with distodorsal spiniform seta; ischium stout, with one distodorsal spiniform seta, mesial side flattened, with one spiniform seta; merus long, slightly inflated, widening distally, ventrally excavated, ventrolateral and ventromesial margins smooth; carpus short, cup-shaped, with broad blunt lobe ventromesially; chela somewhat swollen, subcylindrical; palm depressed on ventrolateral (flexor) surface, distolateral surface smooth; ventromesial surface with about five small tubercles; fingers about 0.4 palm length, somewhat twisted, curved, not gaping, with a few scarce setae or setal tufts, without dense setal brush; cutting edges of pollex and dactylus serrated, with six-seven rounded teeth becoming smaller distally ( Fig. 6 View FIGURE 6 A–D). Minor cheliped significantly smaller than major cheliped; ischium unarmed on distodorsal margin; merus about four times as long as wide, slightly depressed ventrally; carpus vase-shaped, smooth; chela simple, slender, with fingers slightly longer than palm, cutting edges unarmed, with row of stiff setae ( Fig. 6 View FIGURE 6 D, E).

Second pereiopod comparatively small, with ischium slightly wider and much shorter than merus, both unarmed; carpus with five articles, first longer than remaining four articles combined, ratio of carpal articles (proximal to distal) about 7: 1: 1: 1: 2; chela simple, longer than most-distal carpal article, with fingers shorter than palm ( Fig. 5 View FIGURE 5 G, H). Third pereiopod relatively slender, with strongly compressed ischium, merus, carpus and propodus; ischium with two spiniform setae on ventrolateral surface and one spiniform seta on distodorsal margin; merus almost four times as long as wide, with small, subacute tooth on distolateral margin, without spiniform setae; carpus more slender than merus, about half-length of merus, with stout spiniform seta on distoventral margin; propodus with five spiniform setae along ventral margin and three spiniform setae adjacent to dactylar base; dactylus about 0.4 length of propodus, simple, conical, gradually curving distally, dorsal margin faintly notched at about 0.5 and 0.7 dactylar length, furnished with some setae ( Fig. 5 View FIGURE 5 I). Fourth pereiopod similar to third pereiopod, more slen- der; ischium with two spiniform setae on ventrolateral surface, distodorsal margin unarmed; merus about four times as long as wide, wider than merus of third pereiopod; propodus with four spiniform setae; carpus and dactylus as in third pereiopod ( Fig. 5 View FIGURE 5 J). Fifth pereiopod more slender than third or fourth pereiopods; ischium without spiniform seta on ventrolateral surface; merus with small, acute tooth on distolateral margin; carpus with two spiniform setae distoventrally; propodus with at least two small spiniform setae along ventral margin and one pair of spiniform setae adjacent to dactylus; distolateral surface with three rows of thick serrulate setae; dactylus similar to that of third pereiopod ( Fig. 5 View FIGURE 5 K).

Male second pleopod unknown; female second pleopod with appendix interna. Uropod with lateral lobe of protopod bearing large, acute lateral tooth and smaller but distinct acute mesial tooth adjacent to lateral tooth; exopod with diaeresis straight, deeply curving mesially; distolateral tooth small, subacute, adjacent distolateral spiniform seta moderately elongate; distomesial margin with row of spiniform setae ( Fig. 5 View FIGURE 5 L).

Gill-exopod formula typical for genus (see above); reduced exopod-like lobe present at basis of minor cheliped ( Fig. 6 View FIGURE 6 E).

Colour pattern. Carapace almost completely covered with white chromatophores dorsally; first to fifth abdominal somites completely covered with red chromatophores; sixth abdominal somite, telson and uropods white; major cheliped hyaline-white; antennules, antennae, minor cheliped, and second to fifth pereiopods whitish ( Fig. 7 View FIGURE 7 C, D).

Etymology. This new species is named after Ryutaro Goto (Kyoto University, Japan), whose interest in the macrofauna associated with echiurans ( Goto et al. 2011; Goto & Kato 2012) led to the collection of the holotype.

Ecology. The holotype was collected on a sand flat composed of gravel and coral sand exposed at low tide, under large rocks, in the gallery of the echiuran Ochetostoma erythrogrammon Leuckart & Rüppel, 1828 ( Thalassematidae, Ochetostomatinae ) ( Fig. 7 View FIGURE 7 C). The paratype was found under rocks in 6 m deep water, where it was associated with a generally similar-looking echiuran, possibly a species of Ochetostoma ( Fig. 7 View FIGURE 7 D). No detailed ecological notes are available for the Indonesian specimen.

Type locality. Southern Japan, Ryukyu Archipelago, Amami-Oshima Island.

Distribution. Presently known only from the Ryukyu Archipelago, Japan, and Talaud Islands, Indonesia (see map in Fig. 8 View FIGURE 8 ).

Remarks. Athanopsis gotoi sp. nov. is most closely related to A. platyrhynchus , A. brevirostris (see above), and A. saurus (see Anker 2011a). These four species are characterised by the unarmed meri of the third to fifth pereiopods, as opposed to the other three species of the genus, viz. A. dentipes , A. australis , and A. rubricinctuta , in which the meri of the third to fifth pereiopods are armed with one or more stout spiniform setae. Based on morphological grounds, A. gotoi sp. nov. can be separated from all of them by the dorsally markedly domed carapace; from A. platyrhynchus by the non-gaping, serrated finger cutting edges of the major chela (gaping and armed with a few large teeth in A. platyrhynchus , cf. Fig. 1 View FIGURE 1 D); and from both A. brevirostris and A. saurus by the absence of dense setae on the fingers of the major chela, the distally blunter and much shorter stylocerite (not reaching third article of the antennular peduncle in A. gotoi sp. nov. vs. reaching mid-length of this article in the other two species; see Fig. 2 View FIGURE 2 A; Anker 2011a), and the more tapering telson (cf. Figs. 2 View FIGURE 2 M, 5M).

The colour pattern of A. gotoi sp. nov. appears to be unique within the genus by combining the uniformly red first to fifth abdominal somites with the entirely white carapace, sixth abdominal somite and tail fan ( Fig. 7 View FIGURE 7 C, D). This colour pattern clearly differs from those of A. brevirostris ( Fig. 7 View FIGURE 7 A, B) and A. saurus ( Fig. 7 View FIGURE 7 E), in which a few broad white bands are intercalated into the mostly red abdomen, and from that of A. platyrhynchus , with red transverse bands on the carapace ( Coutière 1899; see above). The three remaining and more distantly related species, viz. A. rubricinctuta , A. australis , and A. dentipes exhibit even more different colourations ( Fig. 7 View FIGURE 7 F, G, H; colour pattern of A. dentipes similar to that of A. australis , see Miya 1980).