Athanopsis brevirostris Banner & Banner, 1981

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 : 51-55

publication ID	https://doi.org/ 10.5281/zenodo.215146
DOI	https://doi.org/10.5281/zenodo.6178250
persistent identifier	https://treatment.plazi.org/id/039B87C5-FF91-DF0B-FF00-E03B2C5039AF
treatment provided by	Plazi
scientific name	Athanopsis brevirostris Banner & Banner, 1981
status

Treatment

Athanopsis brevirostris Banner & Banner, 1981 View in CoL

Figs. 2–4 View FIGURE 2 View FIGURE 3 View FIGURE 4 , 7 View FIGURE 7 A, B

Athanopsis brevirostris Banner & Banner 1981: 45 View in CoL , fig. 5.

Material examined. 1 non-ovigerous female (cl 3.5 mm), holotype, RMNH D32942, Eritrea, Dahlak Archipelago, Cundabilu Islands, among corals, poisoning station E62/1393, depth 0–3 m, leg. First Israel South Red Sea Expedition of the Tel Aviv University, 25 March 1962; 1 male (cl 3.7 mm), FLMNH UF Arthropoda 14486, Madagascar, Nosy-Bé, east of Hellville, at CNRO shore side, 13.4069’ S 48.2917 ’E, intertidal mud and sand flat, depth 0–1 m, in burrow, suction pump, leg. A. Anker, 18 May 2008; 1 ovigerous female (cl 4.0 mm), FLMNH UF Arthropoda 14487, same collection data as for previous specimen (from the same burrow, probably mated pair); 1 male (cl 5.5 mm), OUMNH.ZC. 2011-06-047, Japan, Okinawa Prefecture, Okinawa Island, Kuji, 26.30'N, 128.00'E, gravel and coral sand fat, exposed at extreme low tide, under rocks, with Ochetostoma sp., leg. R. Goto, 2 April 2010.

Description. Small-sized alpheid shrimp (cl 3.5–5.5 mm). Carapace glabrous, not setose, not particularly swollen. Rostrum well developed, laterally compressed, triangular, slightly shorter than broad at base; tip rounded in lateral view, acute in dorsal view, not reaching distal margin of first article of antennular peduncle; rostral carina rather slight, not reaching level of eye base posteriorly ( Fig. 2 View FIGURE 2 A, B). Extracorneal teeth well developed, subtriangular, subacute or blunt distally ( Fig. 2 View FIGURE 2 A, B). Pterygostomial angle bluntly projecting anteriorly ( Fig. 2 View FIGURE 2 B); cardiac notch deep.

Eyes partly exposed in dorsal and lateral views; cornea well pigmented, occupying most of terminal portion of eyestalk ( Fig. 2 View FIGURE 2 A, O).

Pleura of first to fourth abdominal somites rounded posteroventrally; fifth pleuron with rounded posteroventral angle; sixth somite with large, triangular, articulated plate. Telson widest at proximal margin, distally tapering; dorsal surface with two pairs of small spiniform setae, situated at some distance from lateral margin, at about 0.5 and 0.7 telson length, respectively; posterior margin broadly rounded, with two pairs of slender spiniform setae at each lateral angle, mesial almost three times as long as lateral ( Fig. 2 View FIGURE 2 M).

Antennular peduncle stout; stylocerite subacute distally, reaching to mid-length of third article ( Fig. 2 View FIGURE 2 A); ventromesial carina with strong, anteriorly produced tooth ( Fig. 2 View FIGURE 2 C); second article distinctly shorter than wide; lateral flagellum biramous, fused portion short, apparently with only two articles; accessory ramus well-developed, with at least four tufts of aesthetascs ( Fig. 2 View FIGURE 2 B). Antenna with stout basicerite ending in strong subacute tooth distoventrally; scaphocerite slightly exceeding end of antennular peduncle; blade broad, ovate; strong distolateral tooth exceeding anterior margin of blade; carpocerite about the same length as scaphocerite ( Fig. 2 View FIGURE 2 A, B).

Mouthparts typical for genus. Third maxilliped with exopod not reaching distal margin of antepenultimate article; coxa with subacute lateral plate above mastigobranch; antepenultimate article flattened, broadening distally; penultimate article less than twice as long as wide proximally; ultimate article narrower than penultimate, tapering distally, furnished with transverse rows of thick serrulate setae, tip with three stout spiniform setae ( Fig. 2 View FIGURE 2 D).

Chelipeds very asymmetrical in shape and unequal in size; carried folded when not in use ( Fig. 3 View FIGURE 3 ). Major cheliped enlarged, robust; ischium short, stout, with three spiniform setae on dorsal margin, mesial side flattened; merus long, slightly swollen, widening distally, ventrally excavated, ventrolateral and ventromesial margins smooth; carpus short, cup-shaped, with large, blunt process ventromesially; chela enlarged, swollen; palm deeply depressed on ventrolateral (flexor) surface, distolateral surface with one tubercle; ventromesial surface with threefour small tubercles and small field of setae; fingers about 0.4 palm length, twisted, curved, with dense setal brush on lateral (flexor) surface of pollex; cutting edges of pollex and dactylus with large rounded teeth ( Fig. 3 View FIGURE 3 A–C). Minor cheliped much smaller than major cheliped; ischium with one spiniform seta on distodorsal margin; merus about 2.5 times as long as wide, depressed ventrally, distolateral margin forming blunt angle; carpus cup-shaped, smooth; chela simple, moderately slender, with fingers slightly longer than palm, cutting edges unarmed ( Fig. 3 View FIGURE 3 D, E).

Second pereiopod comparatively small, with ischium slightly wider and much shorter than merus, both unarmed; carpus with five articles, first subequal in length to sum of remaining four articles, ratio of carpal articles (proximal to distal) about 5: 1: 1: 1: 2; chela simple, longer than most-distal carpal article, with fingers subequal to palm ( Fig. 2 View FIGURE 2 E). Third pereiopod moderately stout, with strongly compressed ischium, merus, carpus and propodus; ischium with two spiniform setae on ventrolateral surface and one spiniform seta on distodorsal margin; merus about 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 pair of stout spiniform setae on distoventral margin; propodus with about five spiniform setae along ventral margin and three spiniform setae adjacent to dactylar base; dactylus slightly less than half-length of propodus, simple, conical, gradually curving distally, dorsal margin slightly notched at about 0.7 dactylar length, furnished with some setae ( Fig. 2 View FIGURE 2 F, G). Fourth pereiopod generally similar to third pereiopod, smaller and more slender ( Fig. 2 View FIGURE 2 H). Fifth pereiopod much more slender than third or fourth pereiopods; ischium without spiniform seta on ventrolateral surface; merus with small, sharp tooth on distolateral margin; carpus with three spiniform setae distoventrally; propodus with several small spiniform setae along ventral margin and one pair of stouter spiniform setae adjacent to dactylus; distolateral surface with two rows of thick serrulate setae; dactylus similar to that of third pereiopod ( Fig. 2 View FIGURE 2 H, I).

Male second pleopod with appendix masculina not exceeding appendix interna, apex with two stiff setae ( Fig. 1 View FIGURE 1 Q). Uropod with lateral lobe of protopod bearing very large, acute lateral tooth and minute subacute mesial tooth; exopod with diaeresis straight, deeply curving mesially; distolateral tooth small, subacute, adjacent distolateral spiniform seta strong, elongate; distal margin with several stout setae ( Fig. 2 View FIGURE 2 K, L).

Gill-exopod formula typical for genus (see above); first pereiopods without rudimentary exopod.

Colour pattern. Carapace with large white patch dorsally, not extending to frontal margin; carapace flanks red or reddish anteriorly, mostly colourless posteriorly; abdomen with broad red bands on first to fifth somite, second and third additionally with white bands, sixth somite and tail fan white; antennular and antennular peduncles reddish; chelipeds hyaline-white; walking legs colourless, semitransparent ( Fig. 7 View FIGURE 7 A, B).

Ecology. The holotype was found at a poisoning station “among corals”, in 0–3 m ( Banner & Banner 1981). The Nosy-Bé specimens were collected with a suction pump from a burrow (without host), at a depth of about 0.5 m at low tide, on a shallow mud-sand flat a few meters off the mangrove-fringed shore. The Okinawa specimen was collected with its echiuran host, Ochetostoma sp., on a mixed gravel and coral sand flat completely exposed only at extreme spring low tides.

Type locality. Eritrea, Dahlak Archipelago, Cundabilu Islands.

Distribution. Presently known from the southern Red Sea (Dahlak Archipelago), northwestern Madagascar (Nosy-Bé) and Ryukyu Archipelago (Okinawa) (see map in Fig. 8 View FIGURE 8 ).

Remarks. The holotype of A. brevirostris (RMNH D32942) is a non-ovigerous, possibly immature female, at cl 3.5 mm (tl 9.0 mm), which is missing both the major and minor cheliped. Banner & Banner (1981) separated A. brevirostris from the closely related A. platyrhynchus by the rostrum being markedly broader than long, reaching to the middle of the first article of the antennular peduncle (vs. longer than broad, reaching to the second article of the antennular peduncle in A. platyrhynchus ), and the second article of the antennular peduncle being almost twice as wide as long (vs. slightly longer than wide in A. platyrhynchus ). Based on these two features, as well as the length of the stylocerite, the proportions of the second pereiopod, the shape and armature of the fifth pereiopod, and the general shape of the third maxilliped and telson ( Banner & Banner 1981, fig. 5), the specimens from Nosy-Bé, Madagascar, appear to be A. brevirostris .

Anker & Ahyong (2007) pointed out to inaccuracies in Banner & Banner’s (1982) description and figures of A. autralis . Similarly, there are errors in the original description of A. brevirostris , as revealed by the re-examination of the holotype. For instance, Banner & Banner’s (1981) figures of the third and fourth pereiopods of A. brevirostris show the meri as blunt distally and the ischium of the third pereiopod as unarmed. In the description itself, the distal angle of the merus is not mentioned, but the ischium of the third pereiopod is described as unarmed. However, in the holotype, the meri of both the third and the fourth pereiopods are subacute distally and their ischia are armed with two stout spiniform setae, as illustrated for the specimen from Nosy-Bé ( Fig. 2 View FIGURE 2 F, H, I).

The specimen from Okinawa ( Fig. 4 View FIGURE 4 ) differs from specimens from the Red Sea and Madagascar in the longer rostrum, with the tip reaching the distal margin of the first article of the antennular peduncle; the second article of the antennular peduncle only slightly wider than long; the ventrolateral margin of the major cheliped merus with a relatively large, rounded notch (which may be a healed past injury); and the appendix masculina with at least four apical stiff setae (vs. only two in the male from Nosy-Bé, which, however is distinctly smaller). The ischium of the fifth pereiopod of the female from Okinawa is armed with a stout spiniform seta, as is the case of the male from Nosy-Bé. The colour pattern of the Japanese specimen is generally very similar to that of the Madagascar specimens ( Goto & Kato 2012, fig. 1h), supporting its assignment to A. brevirostris .

Athanopsis brevirostris appears to be most closely related to A. platyrhynchus (see above) and A. saurus (see Anker 2011a). Based on morphological grounds, A. brevirostris can be separated from A. platyrhynchus by the much longer stylocerite, from A. saurus by the shorter brush on the major chela (extending from the fingers to the palm in A. saurus ), and from both of them by the shorter rostrum and second article of the antennular peduncle. In the colour pattern, A. brevirostris ( Fig. 7 View FIGURE 7 A, B) is similar to A. saurus ( Fig. 7 View FIGURE 7 E), which has more white colour on the second and third abdominal somites and much less red colour on the carapace.