Athanas iranicus, Anker, Arthur, Naderloo, Reza & Marin, Ivan, 2010

Anker, Arthur, Naderloo, Reza & Marin, Ivan, 2010, On a new species of the shrimp genus Athanas Leach, 1814 (Crustacea, Decapoda, Alpheidae) from Iran *, Zootaxa 2372, pp. 53-60 : 54-59

publication ID	https://doi.org/ 10.5281/zenodo.193710
DOI	https://doi.org/10.5281/zenodo.6207427
persistent identifier	https://treatment.plazi.org/id/665C87E2-A02F-FFF4-FF5A-721CFC55F926
treatment provided by	Plazi
scientific name	Athanas iranicus
status	sp. nov.

Treatment

Athanas iranicus View in CoL sp. nov.

( Figs. 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 4 )

Type material. Holotype: male, cl 3.4 mm, SMF 34602, Iran, Hormozgan, Qeshm Island north of Strait of Hormuz, northern coast, 2 km east of desalination center, 26º56’N, 55º47’E, intertidal, muddy sand with shell fragments, leg. R. Naderloo and M. Türkay, 15.I.2008.

Description. Small-sized shrimp with moderately slender, subcylindrical body ( Fig. 1 View FIGURE 1 ). Carapace smooth, sparsely covered with simple setae. Rostrum short, not overreaching mid-length of first segment of antennular peduncle ( Fig. 2 View FIGURE 2 B), subtriangular, broad at base, distally acute, with distinct lateral ridges. Extra-corneal teeth very short, triangular, distally subacute, about 1/5 rostrum length ( Fig. 2 View FIGURE 2 B); infra-corneal and supra-corneal teeth absent. Pterygostomial angle rounded, slightly protruding anteriorly, without acute tooth ( Figs. 2 View FIGURE 2 A–B). Cardiac notch well developed ( Fig. 1 View FIGURE 1 ).

First to fourth abdominal somites with ventrally rounded pleura, pleuron of fifth somite with blunt posteroventral angle ( Fig. 1 View FIGURE 1 ); sixth somite with large, subtriangular, articulated plate and bluntly produced posterolateral angle. Uropod with lateral lobe of protopod bearing two small teeth, margin in-between fringed with row of setae ( Fig. 2 View FIGURE 2 D); exopod with fairly stout distolateral spine; diaeresis straight, without specific features. Telson subrectangular, tapering distally ( Fig. 2 View FIGURE 2 E); dorsal surface with two pairs of stout, long spines, situated at about 1/3 and 2/3 of telson length, respectively; posterior margin rounded, each posterolateral angle with pair of spines, mesial slender, about 2.5 times as long as lateral ( Fig. 2 View FIGURE 2 E).

Eyes partly concealed, only most-anterior portion visible in dorsal and lateral views ( Figs. 2 View FIGURE 2 A–B); eyes with well-developed and pigmented corneas and short tubercle on distodorsal margin ( Fig. 2 View FIGURE 2 C).

Antennular peduncle relatively stout; first (basal) segment more than 1.5 times longer than wide, with strong tooth on mesioventral margin ( Fig. 2 View FIGURE 2 G), stylocerite long, acute distally, reaching past mid-length of second segment of antennular peduncle ( Figs. 2 View FIGURE 2 B, F); latter about as long as first segment, longer than distal segment, about 1.5 times as long as wide in dorsal view; lateral antennal flagellum bifurcating at fourth segment, secondary ramus with three free segments carrying dense clusters of aesthetascs ( Fig. 2 View FIGURE 2 A). Antenna ( Figs. 2 View FIGURE 2 B, H) with basicerite fairly stout, bearing strong, sharp ventrolateral tooth ( Figs. 2 View FIGURE 2 A, H); scaphocerite subrectangular, not reaching distal margin of carpocerite, reaching slightly beyond distal margin of antennular peduncle; distolateral tooth strong, acute; distal margin of scaphocerite blade not reaching past distolateral tooth, convex ( Figs. 2 View FIGURE 2 B, H).

Mouthparts not dissected, typical for genus in external observation. Third maxilliped ( Fig. 2 View FIGURE 2 I) slender, pediform; antepenultimate segment about seven times as long as wide, with slender subdistal spiniform seta on distoventral margin; penultimate segment about 2.5 times as long as wide; ultimate segment about six times as long as wide, tip furnished with two long stiff spiniform setae; coxa with ear-shaped, distally subacute lateral plate; arthrobranch absent.

First pereiopods (= chelipeds) greatly enlarged, subequal in size, but slightly asymmetrical in shape and finger armature (Fig. 3), in life carried folded with ventral portion of palm fitting in ventrally deeply excavated merus. Major cheliped with stout coxa and short basis, both unarmed; basis with rudimentary exopod; ischium with three lateral and five dorsal spines in rows (Fig. 3B); merus significantly broadened distally, ventral surface excavated, proximally with four mesial and three dorsal spines (Fig. 3B); carpus relatively short, vase-shaped, distally widening, with dense row of long simple setae along distodorsal margin appearing in line and “connecting” to row of setae on proximodorsal portion of palm (Figs. 3A–B); palm smooth, distinctly flattened, with moderately convex dorsal and strongly convex ventral margins (Fig. 3C); dorsal margin furnished with dense rows of long simple setae, reaching to 3/4 of palm length (Figs. 3A–B); fingers subcylindrical, curved laterally, cutting edges with triangular teeth of different size, as illustrated (Fig. 3D); dactylus furnished with row of long simple setae on lateral margin, forming dense, posterolaterally or lateroventrally directed setal brush (Fig. 3A).

Minor cheliped slightly smaller but generally very similar to major cheliped, except for armature on chela fingers (Figs. 3A, E); coxa and basis unarmed, basis with rudimentary exopod (visible in Fig. 3E); ischium with three small mesial spines, four small dorsal spines proximally, and one larger dorsal spine distally (Fig. 3E); merus significantly broadened distally, ventrally excavated, with four mesial and three dorsal spines proximally; carpus relatively short, vase-shaped, widening distally, with dense rows of long simple setae along distodorsal margin; palm smooth, conspicuously flattened, with slightly convex dorsal and more strongly convex ventral margins; dorsal margin with rows of dense long simple setae reaching from proximal margin to about 3/5 of palm length; fingers slender, subcylindrical, curved, with minuscule irregular teeth along cutting edges, including one or two larger teeth proximally (Fig. 3F); dactylus without dense setal rows. Second pereiopod ( Fig. 4 View FIGURE 4 A) relatively short; ischium and merus unarmed; carpus five-segmented, with ratio approximately equal to (proximal to distal) 5: 1: 1: 1: 2; chela simple, slender, about 1.5 times as long as fifth carpal segment, fingers as long as palm.

Third pereiopod ( Fig. 4 View FIGURE 4 B) moderately slender; ischium with one small ventrolateral spine and one slender distodorsal spinule; merus unarmed, about five times as long as wide, with distoventral angle bluntly produced; carpus about three times as long as maximal width, with one distoventral spinule; propodus about 5.5 times as long as wide, with three minute ventral spines and one pair of distoventral spinules; dactylus relatively slender, simple, curved distally, about 0.4 times propodus length. Fourth pereiopod overall similar to third pereiopod, but more slender ( Fig. 4 View FIGURE 4 C). Fifth pereiopod generally similar to fourth except for propodus ( Fig. 4 View FIGURE 4 D); ischium armed with one ventrolateral spine and one distodorsal spinule; carpus slender, about four times as long as wide, unarmed; propodus slender, with two minute spines in proximal third of length and several rows of short setae distally (propodal cleaning brush); dactylus simple, slender, slightly curved.

Gill/exopod formula typical for genus: 5 pleurobranchs (P1–5); 0 arthrobranchs; 0 podobranchs; 5 mastigobranchs (Mxp3, P1–3); 5 setobranchs (P1–4); 3 normal exopods (Mxp1–3) + 1 rudimentary exopod (P1).

Size. cl 3.4 mm (total length around 9 mm).

Colour. Unknown.

Habitat. Intertidal sandflat with muddy sand and shell debris, and rocks in some area. Syntopic crustaceans include Alpheus cf. lobidens De Haan ; Nanosesarma sp. (undescribed species, Naderloo & Türkay, in prep.), and Upogebia carinicauda (Stimpson) .

Etymology. Named after the country of the type locality, Iran.

Distribution. Presently known only from the type locality — Qeshm Island, the Iranian side of the Strait of Hormuz (separating the Persian Gulf from the Gulf of Oman).

Relationships. Athanas iranicus n. sp. may be placed in the increasingly heterogeneous and probably non-monophyletic Athanas dimorphus species group. This group is characterised mainly by the general shape of the first chelipeds and their ability to be carried flexed, with the chela fitting in the deeply depressed merus ( Anker & Jeng 2007). Within the A. dimorphus group, the new species shows some similarities to A. squillophilus Hayashi, 2002 from Japan. Both A. iranicus n. sp. and A. squillophilus have dense rows of long setae on the palms of the chelipeds. However, in A. squillophilus , these setal rows are at a different location and extend to the fingers, but not onto the carpus as in A. iranicus n. sp. (cf. Fig. 3 and Hayashi 2002: figs. 3A–C). In addition, in A. squillophilus , the eyestalks are almost completely exposed dorsally; the rostrum is much longer; the antennal peduncles are stouter, with shorter stylocerites; the extra-corneal teeth are distinctly narrower and sharper; and the pterygostomial angle protrudes in the form of a sharp tooth ( Hayashi 2002). Another species with a dense setal brush on the major cheliped is A. dentirostris Anker, Jeng & Chan, 2001 from Vietnam, which differs from A. iranicus n. sp. by the much longer, minutely dentate rostrum; the cheliped meri being less swollen and having dentate margins distomesially; and by the setal brushes being restricted mostly to the fingers and to the major cheliped only ( Anker et al. 2001: figs. 3a–c). These numerous and rather important morphological differences suggest that A. iranicus n. sp. is not closely related to A. squillophilus or A. dentirostris . Both A. squillophilus and A. dentirostris appear to live “commensally” in burrows of stomatopods and upogebiids, respectively ( Anker et al. 2001; Hayashi 2002), and the presence of dense setal brushes in these species may be linked to their commensal life style. These brushes could be used to collect food or “sweep” (clean) the burrow or both, although this remains to be demonstrated. It also remains unknown whether A. iranicus n. sp., which has similar brushes, is a free-living species or lives commensally in tunnels of some larger burrowing hosts.

Males of several other species from the A. dimorphus species group, including A. rhothionastes and A. parvus (the two species reported from the Persian Gulf), as well as A. dimorphus , A. marshallensis Chace, 1955 , and A. djiboutensis Coutière, 1897 , have overall similar chelipeds. However, all these species differ from the new species by many other characters, such as the much longer rostrum and well-developed, acute extra-corneal teeth ( A. dimorphus , A. marshallensis , A. rhothionastes , A. parvus , A. djiboutensis ); the presence of supra-corneal teeth ( A. djiboutensis ); and the biunguiculate dactyli on the third to fifth pereiopods ( A. parvus ). Most importantly, all these species are characterised by the absence of dense setal brushes on any part of the chelipeds. In summary, A. iranicus n. sp. appears to be unique among all presently known species of Athanas by having dense setal brushes extending dorsally from mid-length of the carpus to about threequarters palm length, the frontal margin bearing a very short triangular rostrum and small extra-corneal teeth, and the eyestalks being almost completely concealed in dorsal view.