Athanopsis dawa, 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 : 198-203

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.10392024
persistent identifier	https://treatment.plazi.org/id/386ABE42-FFA3-FFB7-FF06-A8172F57F878
treatment provided by	Plazi
scientific name	Athanopsis dawa
status	sp. nov.

Treatment

Athanopsis dawa sp. nov.

( Figs. 10 View FIGURE 10 , 11 View FIGURE 11 , 12a, b View FIGURE 12 )

Material examined. Holotype: ovig. female (cl 4.4 mm), FLMNH UF 71424 , Oman, Masirah Island , channel side, Dafiyat, 20°35’15.1”N / 58°49’36.9”E, intertidal and shallow subtidal sandflat with patches of coral rubble, rocks and seagrass, depth at low tide 0.1–0.5 m, suction pump, in echiuran burrow, leg. A. Anker, 07.11.2022 [fcn BOMAN-13017] GoogleMaps . Paratype: ovig. female (cl 4.7 mm), FLMNH UF 71423 , same collection data as for holotype [fcn BOMAN-13028] GoogleMaps .

Description. Carapace ( Fig.10a–d View FIGURE 10 ) glabrous, somewhat domed, with conspicuous, anteriorly directed postrostral tubercle. Rostrum ( Fig. 10b, c, d View FIGURE 10 ) moderately long, overreaching distal margin of first article of antennular peduncle, subtriangular, as long as broad at base, with acute tip; rostral carina distinct, continued by postrostral carina and fading just anterior to postrostral tubercle. Extra-corneal teeth ( Fig. 10b–d View FIGURE 10 ) triangular, subacute distally. Pterygostomial angle ( Fig. 10a, c View FIGURE 10 ) bluntly or subacutely produced anteriorly. Cardiac notch ( Fig. 10a View FIGURE 10 ) deep.

Pleon ( Fig. 10e View FIGURE 10 ) glabrous; first to fifth pleura rounded distoventrally; sixth pleonite with subtriangular articulated plate. Telson ( Fig. 10f View FIGURE 10 ) moderately broad, gently tapering distally, about 2.1 times as long as proximal width; dorsal surface with two pairs of small spiniform setae situated at some distance from lateral margins, approximately at 0.50–0.55 (anterior) and 0.70–0.75 (posterior) of telson length; posterior margin slightly rounded, with two pairs of spiniform setae, mesial almost three times as long as lateral.

Eyes ( Fig. 10a, b, d View FIGURE 10 ) largely exposed dorsally and laterally, with well pigmented but slightly reduced corneas; anteromesial margin of eyestalks rounded, unarmed.

Antennule ( Fig. 10b, c, g View FIGURE 10 ) stout; stylocerite with blunt tip, reaching mid-length of third article of peduncle; ventromesial carina with large, anteriorly directed, sharp tooth; second article about 0.8 times as long as wide; lateral flagellum with fused portion composed of four units, accessory ramus well developed, subdivided into at least six poorly individualised units, each carrying group of two or three aesthetascs.

Antenna ( Fig. 10b, c View FIGURE 10 ) with basicerite stout, its distolateral margin armed with large, sharp tooth; scaphocerite broad, short, reaching slightly beyond end of antennular peduncle; lateral margin straight; anterior margin of blade rounded, greatly exceeded by stout distolateral tooth; carpocerite very stout, slightly overreaching both antennular peduncle and scaphocerite; flagellum thickened.

Mouthparts not dissected, typical for genus in external observation. Third maxilliped ( Fig. 10h, i View FIGURE 10 ) relatively stout; coxa with somewhat produced, distally acute lateral plate above mastigobranch; antepenultimate article noticeably broadened, with strongly convex dorsal margin, about 3.2 times as long as maximal width; penultimate article subrectangular, about 1.7 times as long as wide; ultimate article much slenderer and almost three times as long as penultimate article, tapering distally, with tip armed with one long and two short spiniform setae; exopod well developed, not reaching penultimate article.

First pereiopods (= chelipeds) about equal in size, symmetrical in shape, carried folded ventrally when not in use ( Figs. 11a–e View FIGURE 11 , 12a View FIGURE 12 ); basis with rudimentary exopod; ischium stout, widening distally, with three spiniform setae on dorsal margin, ventral surface unarmed; merus not particularly swollen, about four times as long as wide, with deeply excavated ventral surface, slightly convex dorsal margin and somewhat concave ventrolateral margin, all surfaces smooth; carpus very short, cup-shaped, smooth; chela slightly longer than merus; palm feebly swollen, depressed ventrolaterally, about three times as long as high (wide) in mesial view of chela, smooth; fingers 0.7 times as long as palm, strongly curved laterally, noticeably deviating from axis of palm, slender, fitting tightly when closed except for small gape proximally; cutting edge of pollex with with broad hiatus proximally followed by low triangular tooth at about proximal third of pollex, this tooth being continued by straight edge to fingertip; cutting edge of dactylus with three subtriangular, blunt teeth opposed to hiatus on pollex, remaining edge smooth.

Second pereiopod ( Fig. 11f View FIGURE 11 ) relatively short and rather stout; ischium about 2.6 times as long as distal width, distally widening, somewhat depressed on ventromesial surface; merus about 1.6 times as long as ischium, stout, 3.5 times as long as wide; carpus with five subarticles, proximal as long as sum of four others; chela longer than distal-most carpal subarticle, simple, with fingers equal to palm. Third to fifth pereiopods relatively stout, similar in length. Third pereiopod ( Fig. 11g –i View FIGURE 11 ) with ischium armed with two spiniform setae on ventrolateral surface and one spiniform seta on distodorsal margin; merus about 1.6 times as long as ischium, 3.5 times as long as maximal width, not particularly swollen, ventrolateral margin distally with small subacute tooth; carpus noticeably more slender than merus, about half-length of merus, with two spiniform setae on distoventral margin; propodus about 1.8 times as long as carpus, slenderer than carpus, with seven spiniform setae on ventral or ventromesial margin, and one pair of spiniform setae distally, flanking base of dactylus; dactylus simple, slender, strongly curved, about 0.4 length of propodus. Fourth pereiopod ( Fig. 11j, k View FIGURE 11 ) generally similar to third pereiopod, slenderer; ischium armed with two spiniform setae on ventrolateral surface and one spiniform seta on distodorsal margin; merus 3.3 times as long as maximal width, ventrolateral margin distally with small subacute tooth; carpus about half-length of merus, with two spiniform setae on distoventral margin; propodus with seven spiniform setae on ventral or ventromesial margin, and one pair of spiniform setae distally, flanking base of dactylus; dactylus similar to that of third pereiopod. Fifth pereiopod ( Fig. 11l–n View FIGURE 11 ) shortest and slenderest of walking legs; ischium unarmed; merus about twice as long as ischium, about 3.2 times as long as wide, ventrolateral margin distally with small subacute tooth; carpus 0.6 length of merus, with two spiniform setae on distoventral margin; propodus with six spiniform setae on ventral or ventromesial margin, one pair of spiniform setae distally, flanking base of dactylus, and three rows of microserrulate setae on distolateral surface; dactylus similar to that of third or fourth pereiopods.

Uropod ( Fig. 10j View FIGURE 10 ) with lateral lobe of protopod enlarged, produced distally, with larger, triangular lateral tooth and smaller, blunt mesial tooth; exopod with stout distolateral tooth and long adjacent spiniform seta, latter almost reaching level of distal margin; diaeresis straight for most part, with low lateral lobe; endopod ovoid, as long as exopod.

Gill-exopod formula as given for genus.

Colour in life. Background translucent whitish, with pale yellow tinge in females; carapace with bright red patch on rostro-orbital area, one narrow red band fringing each anterolateral margin, one much broader, more irregular transverse band extending from each branchial margin to cardiac region, not joining dorsally, and one very broad, white, transverse band covering almost entire area adjacent to posterior margin from dorsal mid-line to just above posterior-most portion of branchiostegial margin; pleon with four bright red, moderately narrow, transverse bands, more precisely on first, second, fourth and fifth pleonites, third pleonite with conspicuous, white, transverse band, sixth pleonite with broader, ring-like, white band; remaining appendages hyaline whitish; eggs / ovaries yolky yellow ( Fig. 12a, b View FIGURE 12 ).

Etymology. The new species name refers to dhow (Arabic داو, latinised: dāwa ), a generic name for traditional sailing vessels commonly seen in the western Indian Ocean from the Red Sea to the Arabian-Persian Gulf and Zanzibar; used as a noun in apposition.

Type locality. Masirah Island , Oman .

Distribution. Currently known only from Masirah Island in Oman.

Ecology. Both type specimens were extracted from presumably echiuran burrows on a shallow sandflat with patches of seagrass and coral rubble ( Fig. 12c View FIGURE 12 ), at a depth less than 0.5 m at low tide.

Remarks. Athanopsis dawa sp. nov. can be easily distinguished from all other species of Athanopsis by two features, both being novel for this genus. The rather conspicuous postrostral tubercle on the carapace is a unique and highly diagnostic feature of the new species, as are the almost equal and subsymmetrical chelipeds ( Figs. 11a, b View FIGURE 11 , 12a View FIGURE 12 ). All other species of Athanopsis lack such a tubercle and have very unequal and asymmetrical chelipeds. It must be noted that both type specimens of A. dawa sp. nov. are females and that the male condition of the chelipeds is currently unknown. Nevertheless, in other species of Athanopsis , the relative development of the right and left cheliped is similar between males and females (e.g., Anker 2012: fig. 6; Marin et al. 2014: fig. 6).

The lack of armature (in the form of spiniform setae) on the merus of the third and fourth pereiopods places A. dawa sp. nov. closest to A. brevirostris , A. saurus (see above), A. platyrhynchus Coutière, 1897 , A. tarahomii Marin, Sheibani & Sari, 2014 and A. gotoi Anker, 2012 . However, all of them present several significant differences, in addition to lacking the post-rostral tubercle on the carapace and having very unequal and asymmetrical chelipeds. Athanopsis dawa sp. nov. can be separated from A. brevirostris by the relatively longer second article of the antennular peduncle, which is as long as wide (vs. much wider than long in A. brevirostris ); from A. saurus by the lateral margins of the rostrum shallowly concave throughout their length (vs. distinctly convex proximally in A. saurus ); from both A. brevirostris and A. saurus by the absence of dense setal cover on parts of the major chela (vs. with fields of setae on the fingers and distal portion of the palm in A. brevirostris and A. saurus ); from A. platyrhynchus , A. tarahomii and A. gotoi by the much longer stylocerite, by far exceeding the distal margin of the second article of the antennular peduncle (vs. reaching only to the mid-length of the second article in A. platyrhynchus and A. tarahomii , or falling short of this article’s distal margin in A. gotoi ); from A. tarahomii by the noticeably slenderer third and fourth pereiopods (which are very stout in A. tarahomii ), the third maxilliped with a proportionally longer and more rectangular-shaped penultimate article (vs. with a very short, almost rounded, dorsally convex penultimate article in A. tarahomii ), and the rostrum pointing forwards (vs. descending in A. tarahomii ); and from A. gotoi by the dorsally partly exposed eyes (which are dorsally concealed by the orbital hoods in A. gotoi ) and the absence of tubercles on the ventral surface of the chelae (which are present in the major chela of A. gotoi ) (cf. Coutière 1899; Banner & Banner 1981; Anker 2011, 2012; Marin et al. 2014). The colour patterns are known for A. brevirostris ( Anker 2012; see also Fig. 8 View FIGURE 8 ), A. saurus (Anker 2011, 2012; see also Fig. 9 View FIGURE 9 ), A. tarahomii ( Fig. 14 View FIGURE 14 ; not Marin et al. 2014: fig. 7, see below), and A. gotoi ( Anker 2012) and are different from that of A. dawa sp. nov. ( Fig. 12a, b View FIGURE 12 ). The colour pattern of A. platyrhynchus remains known only from Coutière’s (1897, 1899) brief description (see Anker 2012 for translation). Generally, the taxonomic identity of A. platyrhynchus , the type species of the genus known with certainty only from Djibouti, remains problematic, as pointed out by Anker (2012).

The remaining species of Athanopsis , i.e., A. dentipes Miya, 1980 , A. australis Banner & Banner 1982 and A. rubricinctuta Berggren, 1991 (see below), are characterised by the presence of spiniform setae on the meri of the third, fourth and fifth pereiopods and present several other morphological differences with the new species (cf. Miya 1980; Banner & Banner 1982; Berggren 1991; Anker & Ahyong 2007). In addition, the colour patterns of A. dentipes and A. australis (cf. Miya 1980; Anker 2012) are very different from that of A. dawa sp. nov. ( Fig. 12a, b View FIGURE 12 ). On the other hand, the colour patterns of A. dawa sp. nov. ( Fig. 12a, b View FIGURE 12 ) and A. rubricinctuta ( Fig 13 View FIGURE 13 ; see also Anker 2012: fig. 7F, G) are very similar, to the extent that the two species may be easily confused in the field. However, at a closer inspection, A. dawa sp. nov. can be distinguished from A. rubricinctuta by the white transverse band on the carapace descending from the dorsal area almost to the branchiostegial margin (vs. being limited to the dorsal area in A. rubricinctuta ) and the presence of an additional white transverse band on the third pleonite (which is missing in A. rubricinctuta ).