Athanas claereboudti, Anker, 2023

Anker, Arthur, 2023, Alpheid shrimps of the genera Athanas Leach, 1814, Athanopsis Coutière, 1897 and Pseudathanas Bruce, 1983 of the coasts of the Arabian Peninsula (Malacostraca: Decapoda: Caridea), Zootaxa 5383 (2), pp. 179-215 : 182-186

publication ID	https://doi.org/ 10.11646/zootaxa.5383.2.5
publication LSID	lsid:zoobank.org:pub:7E434B40-6346-4E6D-BC55-38EBAE24BD52
DOI	https://doi.org/10.5281/zenodo.10350881
persistent identifier	https://treatment.plazi.org/id/386ABE42-FFB3-FFA7-FF06-AFB32CE0FC9C
treatment provided by	Plazi
scientific name	Athanas claereboudti
status	sp. nov.

Treatment

Athanas claereboudti sp. nov.

( Figs. 1–3 View FIGURE 1 View FIGURE 2 View FIGURE 3 )

Material examined. Holotype: 1 male (cl 5.0 mm), FLMNH UF 71417 , Oman, Masirah Island , west coast (channel side), 20°27’44.0”N / 58°46’39.8”E, muddy sandflat with seagrass, depth 0.5 m, suction pump, leg. A. Anker, 08.11.2022 [fcn BOMAN-13043] GoogleMaps . Paratypes: 1 male (cl 4.9 mm, missing minor cheliped), FLMNH UF 71414 , same collection data as for holotype [fcn BOMAN-13042] GoogleMaps ; 1 male (cl 4.1 mm, missing major cheliped), FLMNH UF 63930 , Oman, east of Muscat, Bandar Khayran , 23°30’32.5”N / 58°43’53.5”E, mangrove and adjacent mudflat, at night, depth at low tide 0–1 m, suction pump, in burrow, leg. A. Anker, 04.02.2022 [fcn BOMAN-11363] GoogleMaps .

Description. Carapace ( Fig. 1a–c View FIGURE 1 ) covered with short erect setae, especially dorsally, without post-rostral tubercle. Rostrum ( Fig. 1b, c View FIGURE 1 ) short, reaching to mid-length of first article of antennular peduncle, subtriangular, with subacute tip; rostral carina absent. Extra-corneal teeth ( Fig. 1b, c View FIGURE 1 ) reduced to small bumps; infra-corneal teeth absent. Pterygostomial angle ( Fig. 1c View FIGURE 1 ) rounded, not produced anteriorly. Cardiac notch ( Fig. 1a View FIGURE 1 ) deep.

Pleon ( Fig. 1d View FIGURE 1 ) mostly glabrous; first to fourth pleura rounded distoventrally; fifth pleonite angular distoventrally; sixth pleonite with subtriangular articulated plate. Telson ( Fig. 1e View FIGURE 1 ) strongly tapering distally, about 1.8 times as long as proximal width; dorsal surface with two pairs of stout spiniform setae situated at some distance from lateral margins, approximately at 0.35 (anterior) and 0.65 (posterior) of telson length; posterior margin slightly concave, with two pairs of spiniform setae, mesial twice as long as lateral.

Eyes ( Fig. 1b, c View FIGURE 1 ) partly exposed dorsally and laterally, with well pigmented but slightly reduced corneas; anteromesial margin of eyestalks rounded, unarmed.

Antennule ( Fig. 1b, c, f View FIGURE 1 ) moderately stout; stylocerite with acute tip, reaching or slightly overreaching mid-length of second article of peduncle; ventromesial carina with large, anteriorly directed, blunt tooth; second article about 1.3 times as long as wide; lateral flagellum with fused portion composed of five units, accessory ramus well developed, subdivided into four poorly individualised units, each carrying group of three or four aesthetascs.

Antenna ( Fig. 1b, c, g View FIGURE 1 ) with basicerite very stout, its distolateral margin armed with blunt tooth; scaphocerite broad, reaching to end of antennular peduncle; lateral margin straight to faintly convex; blade broadly convex anteriorly, by far overreaching small distolateral tooth; carpocerite very stout, significantly overreaching both antennular peduncle and scaphocerite; flagellum conspicuously thickened.

Mouthparts not dissected, typical for genus in external observation. Third maxilliped ( Fig. 1h View FIGURE 1 ) slender; coxa with somewhat produced, distally subacute lateral plate above mastigobranch; antepenultimate article somewhat curved, tapering distally, about six times as long as maximal width; penultimate article slender, about five times as long as wide; ultimate article slender, twice as long as penultimate article, tapering only apically, with unarmed tip; exopod well developed, about same length as antepenultimate article.

First pereiopods (= chelipeds) about 20% unequal in size, asymmetrical in shape, carried folded ventrally when not in use ( Figs. 2 View FIGURE 2 , 3 View FIGURE 3 ). Minor cheliped ( Fig. 2a–d View FIGURE 2 ) robust; basis with rudimentary exopod; ischium stout, somewhat flattened ventrally, widening distally, with one spiniform seta on ventromesial margin and row of four unevenly spaced spiniform setae on dorsal margin; merus greatly swollen, with strongly convex dorsal and ventral margins, about 2.5 times as long as greatest width, excavated ventrally, dorsal margin with small tubercles in distal half, distodorsal surface with conspicuously protruding, slightly curved, blunt process, ventrolateral margin furnished with small teeth, distal-most largest; carpus pear-shaped, narrow proximally, widening distally, ventromesial margin with small lobe, rest of surface and margins smooth; chela slightly longer than merus; palm swollen, depressed ventrolaterally, about twice as long as high (wide) in mesial view of chela, ventral margin with row of small tubercles; fingers about 0.8 times as long as palm, strongly curved, noticeably deviating from axis of palm, slender, with unarmed, blade-like cutting edges. Major cheliped ( Fig. 2e–h View FIGURE 2 ) robust; basis with rudimentary exopod; ischium stout, somewhat flattened ventrally, widening distally, with row of seven equidistant spiniform setae on dorsal margin, ventrolateral margin rugose, ending distally in subacute tooth; merus less swollen than in minor cheliped, with strongly convex dorsal margin and almost straight ventral margin, about 2.8 times as long as greatest width, excavated ventrally, dorsal margin smooth, distodorsal surface with conspicuously protruding, slightly curved, blunt process similar to that of minor cheliped, ventrolateral margin evenly serrated, i.e., with small rounded teeth; carpus cup-shaped, very short, widening and with blunt lobes distally, smooth; chela distinctly longer than merus; palm swollen, depressed ventrolaterally, about 2.2 times as long as high (wide) in mesial view of chela, ventral margin with row of small tubercles; fingers about half-length of palm, somewhat curved, noticeably deviating from axis of palm, stout, gaping distally; pollex with four stout teeth on cutting edge, with large gap between two distal-most teeth; dactylus with strongly bent tip, cutting edge with two subtriangular teeth, one smaller proximal tooth and one much larger tooth at about 0.4 dactylar length, distal half of dactylus unarmed, concave.

Second pereiopod ( Fig. 1i View FIGURE 1 ) slender; ischium at most four times as long as maximal width; merus about 1.3 times as long as ischium; carpus with five subarticles, proximal slightly longer than sum of four others; chela longer than distal-most carpal subarticle, simple, with fingers much longer than palm. Third to fifth pereiopods relatively slender, similar in length. Third pereiopod ( Fig. 1j View FIGURE 1 ) with ischium armed with two spiniform setae on ventrolateral surface; merus about 1.8 times as long as ischium, 5.2 times as long as maximal width, feebly convex dorsally; carpus noticeably more slender than merus, about 0.6 length of merus, with one stiff seta on distoventral margin; propodus about 1.2 times as long as carpus, with two widely spaced, stiff setae on ventral margin and one pair of spiniform setae distally, flanking base of dactylus; dactylus simple, slender, strongly curved in distal half, almost sickle-shaped, about 0.6 length of propodus. Fourth pereiopod ( Fig. 1k View FIGURE 1 ) generally similar to third pereiopod; ischium armed with two spiniform setae on ventrolateral surface; merus noticeably slenderer than in third pereiopod, 5.8 times as long as maximal width; carpus about 0.6 times as long as merus; propodus with one stiff seta on ventral margin and one pair of spiniform setae distally, flanking base of dactylus; dactylus similar to that of third pereiopod. Fifth pereiopod ( Fig. 1l View FIGURE 1 ) slenderest of walking legs; ischium with one spiniform seta on ventrolateral surface; merus about twice as long as ischium; carpus almost 0.7 length of merus; propodus distinctly longer than merus, with six rows of microserrulate setae on distolateral surface; dactylus slightly less curved than in third or fourth pereiopods.

Uropod ( Fig. 1n View FIGURE 1 ) with lateral lobe of protopod subacute distally; exopod with small, blunt, distolateral tooth and small adjacent spiniform seta; diaeresis straight for most part; endopod ovoid, slightly shorter and narrower than exopod.

Gill-exopod formula as given for genus; basis of third maxilliped with rudimentary exopod; mastigobranchs present on coxae of third maxilliped and first to third pereiopods; setobranchs present on coxae of first to fourth pereiopods.

Colour in life. Background hyaline whitish with slight yellowish tinge; carapace and pleon largely covered by irregular blotches of red chromatophores; mid-dorsal line of carapace, pleon and entire telson without red chromatophores, instead with patches of buff white chromatophores; carapace flanks and ventral surface of anterior pleonites mostly colourless; antennular and antennal peduncles patchily covered with red chromatophores, flagella whitish; chelipeds hyaline white with occasional red blotch on merus; remaining pereiopods and pleopods whitish; uropods with blotches of red chromatophores ( Fig. 3 View FIGURE 3 ).

Etymology. The species is named after Dr. Michel Claereboudt (formerly at Sultan Qaboos University, Muscat, Oman) for his invaluable help in the organisation of the Oman BioBlitz expedition series.

Type locality. Masirah Island , Oman .

Distribution. Currently known only from two localities in Oman: Masirah Island and Bandar Khayran east of Muscat.

Ecology. All three specimens were collected from burrows of unknown hosts on very shallow (less than 1 m) subtidal mudflats or muddy sandflats, close to mangroves (Bandar Khayran) or seagrass beds (Masirah). The larger syntopic infauna, which is still being sorted and studied, includes large burrowing snapping shrimps ( Alpheus spp. , including A. aff. djeddensis Coutière, 1897 ), callianassid ghost-shrimps, upogebiid mud-shrimps and stomatopods.

Remarks. Athanas claereboudti sp. nov. possesses a unique and conspicuous character not found in any other member of the genus Athanas . The merus of both the major and the minor cheliped of A. claereboudti sp. nov. presents a very prominent, blunt, somewhat curved process in its distodorsal part ( Fig. 2a, b, e, g View FIGURE 2 ). The overall combination of morphological characters of the new species, especially those of the frontal region and chelipeds, suggests that it may be most closely related to A. iranicus Anker, Naderloo & Marin, 2010 , A. daviei Anker, 2011 , and A. manticolus Ďuriš & Anker 2014 , all of them also being infaunal, symbiotic species (Anker et al. 2010; Anker 2011b; Ďuriš & Anker 2014). However, A. claereboudti sp. nov. can be easily separated from each of the three aforementioned species by at least three morphological characters, in addition to the bulging distodorsal process on the cheliped meri. For instance, A. claereboudti sp. nov. differs from A. iranicus by the absence of setal brushes on the carpus and chela (which are characteristic of A. iranicus , see also below); the posterior margin of the telson slightly concave (vs. broadly rounded in A. iranicus ); and the antennal scaphocerite reaching or very slightly overreaching the end of the antennular peduncle (vs. reaching far beyond it in A. iranicus ) (cf. Figs. 2e–h View FIGURE 2 ; Anker et al. 2010: figs. 2B, E, 3A, B, E). Similarly, the new species differs from A. daviei by the noticeably shorter rostrum; the longer stylocerite; the much more swollen cheliped meri; and the slenderer second pereiopod (cf. Figs. 1 View FIGURE 1 , 2a, b View FIGURE 2 ; Anker 2011: figs. 3A, 4A, B, D–F). Finally, A. claereboudti sp. nov. can be easily separated from A. manticolus by the dorsally non-dentate rostrum; the absence of postrostral tubercle; and the more unequal and asymmetrical chelipeds, each with a much more swollen merus (cf. Figs. 2 View FIGURE 2 , 3 View FIGURE 3 ; Ďuriš & Anker 2014: figs. 2A, C, 4). In addition, A. claereboudti sp. nov. can be distinguished from A. iranicus , A. daviei and A. manticolus by its diagnostic colour pattern (cf. Figs. 3 View FIGURE 3 , 5 View FIGURE 5 , Anker 2011: fig. 8E, F; Ďuriš & Anker 2014: fig. 6A, B). All other known species of Athanas , including all infaunal species, present more significant morphological differences with A. claereboudti sp. nov. and (where known) also differ from the new species by their colour patterns (e.g., Hayashi 2002; Anker & Komai 2010; Anker 2011b; Marin 2017; Anker & Ďuriš 2022).