Salmoneus durisi, Anker & Ashrafi, 2019

Anker, Arthur & Ashrafi, Hossein, 2019, Salmoneus durisi sp. nov., an infaunal alpheid shrimp probably associated with callianassid ghost shrimps in the tropical Indo-West Pacific (Malacostraca: Decapoda: Caridea), Zootaxa 4651 (1), pp. 64-74 : 64-74

Salmoneus durisi sp. nov.

Figs. 1–5

Type material. Holotype: ovigerous specimen (cl 5.0 mm, dissected), OUMNH. ZC. 2015-08-030, Oman, near Muscat, Darsait , 23°38’04.7”N 58°32’52.0”E, near-shore sand flat with rocks, depth at low tide: 0.5–1 m, deep under large rocks on fine sand-silt, leg. A. Anker, 24.08.2010 [fcn OM-002].

Additional material. 1 non-ovigerous specimen (cl 5.2 mm), MNHN-IU-2014-20782, Iran, Persian Gulf, Qeshm Island, Ramchah, 26°53’42.81”N 56°09’41.09”E, sandy and partly rocky intertidal, sand with smaller and larger boulders, in burrow of Neocallichirus calmani ( Nobili, 1904) , leg. H. Ashrafi, 30.01.2018; 1 non-ovigerous specimen (cl 4.3 mm, minor cheliped missing), MNHN-IU-2014-20783, Philippines, Panglao 2004 International Expedition, sta. M11, Panglao Island, Sungcolan Bay, 9º38.3’N, 123º49.6’E, rock-sand intertidal, fringing mangrove, suction pump, leg. P.C. Dworschak 15.06.2004 [fcn PD 50].

Tentatively identified material: Salmoneus cf. durisi sp. nov. 1 ovigerous specimen (cl 4.7 mm), MZB Cru 4977, Indonesia, west of Flores, Kanawa Island, shallow intertidal and subtidal sand flat with adjacent sea grass and abundant coral rubble, leg. A. Anker, 27– 28.09.2014 [fcn K24]; 1 ovigerous specimen (cl 2.5 mm, missing minor cheliped), OUMNH ZC 2015-08-032, Solomon Islands, New Georgia, Munda, Kunda Kunda Hite, shallow sandrubble flat with coral “bommies” near reef, deep under coral rubble, leg. A. Anker, 15.09.2016 [fcn SOL-154].

Description. Small-sized (maximal cl 5.2 mm) alpheid shrimp with stout, non-compressed body. Carapace glabrous, not conspicuously setose. Rostrum moderately developed, subtriangular, about as long as wide at base, acute distally, reaching or slightly overreaching distal margin of first article of antennular peduncle, lateral margins almost straight; rostral or mid-dorsal carina, as well as subdistal tooth on ventral margin absent ( Fig. 1a, b, j ). Orbital teeth moderately developed, sharp distally, pointing somewhat mesially in dorsal view, anteriorly in lateral view ( Fig. 1a, b, j ). Pterygostomial region broadly rounded; anterolateral suture present ( Fig. 1b ); cardiac notch well developed. Each epistomial sclerite with strong acute process.

Pleon with first to fourth pleura broadly rounded to slightly angular; fifth pleuron with posteroventral margin forming subacute angle; sixth pleonite with short suture at posteroventral angle, but without well-marked articulated flap, posterior margin blunt, not acutely produced ( Fig. 1c ); preanal plate rounded. Telson moderately slender, subrectangular, distinctly tapering distally, about 2.7 times as long as maximal (proximal) width; dorsal surface with two pairs of stout cuspidate setae both inserted at some distance from lateral margin, first pair at about telson midlength, second pair at about 0.7 of telson length; posterior margin with deep U-shaped notch flanked by two long plumose setae, remaining margin with two pairs of stout spiniform setae, mesial slightly stouter and about 1.2–1.3 times as long as lateral ( Fig. 1d, e ).

Eyes completely or almost completely concealed in dorsal view, except for distal-most portion, partly exposed in lateral view; corneal area somewhat reduced, restricted to dorsolateral surface of eyestalk; anteromesial margin of eyestalk rounded, without tubercle ( Fig. 1a, b, j ).

Antennular peduncle stout; stylocerite elongate, moderately slender, with sharp tip overreaching mid-length of second article but not reaching its distal margin; ventromesial carina with small anteriorly directed tooth; second article slightly longer than wide; lateral antennular flagellum with very short fused portion, consisting of three subdivisions, and well-developed secondary ramus, latter with four groups of aesthetascs; mesial antennular flagellum much stouter than lateral ( Fig. 1a, b, f ). Antenna with stout basicerite bearing stout sharp distoventral tooth; scaphocerite ovoid in general shape, not overreaching end of antennular peduncle, with straight lateral margin and broad blade, latter convex anteriorly, slightly overreaching small sharp distolateral tooth; carpocerite very short, cylindrical, not reaching mid-length of scaphocerite ( Fig. 1a, b, g ).

Third maxilliped slender, pediform; coxa with rounded lateral plate; antepenultimate article slightly flattened ventrolaterally; penultimate article less than four times as long as wide; ultimate article tapering distally, with numerous rows of short serrulate setae and longer simple setae, tip with blunt corneous point and one robust spiniform seta subdistally; arthrobranch well developed ( Fig. 2a, b ).

Chelipeds subequal in size, asymmetrical in shape, carried flexed when not in use ( Figs. 3a, e , 4b ). Major cheliped moderately slender; ischium unarmed, flattened ventrolaterally, with blunt process distomesially; merus about 4.5 times as long as maximal width, somewhat wider near mid-length, smooth, distodorsal and distomesial margins blunt, ventrolateral surface distinctly depressed; carpus constricted proximally, cup-shaped, with several lobes distally; chela subcylindrical, more or less rounded in cross-section ( Fig. 3a, b ); palm shorter than fingers, smooth, except for broad proximolateral bump, ventral margin with row of long fine setae continuing onto pollex, dorsal margin with some long fine setae subdistally; fingers not gaping when closed, subequal in length, crossing distally, not noticeably twisted, with evenly serrated cutting edges; cutting edge of both dactylus and pollex with about 20 subtriangular teeth, distal-most teeth in form of shallow bumps; dactylus with row of long fine setae along dorsal margin ( Fig. 3c, d ). Minor cheliped as long and as robust as major cheliped, with slightly stouter chela; ischium unarmed, slightly flattened ventrolaterally; merus about five times as long as maximal width, somewhat wider near mid-length, smooth, distodorsal and distomesial margins blunt, ventrolateral surface depressed; carpus somewhat bent, cup-shaped, with two rounded lobes distally ( Fig. 3e ); chela slightly compressed, more or less oval in cross-section; palm about 1.5 times longer than dactylus, smooth, ventral margin with row of long fine setae continuing onto pollex, dorsal margin also with row of long fine setae; fingers somewhat gaping when closed, unequal in length, dactylus much longer than pollex, strongly crossing distally, slightly twisted; dactylus with distal portion strongly curved, bent backwards, its cutting edge armed with one proximal low tooth-like process and two distinct teeth, first tooth stronger, rounded, second (distal-most) tooth much smaller, situated at about mid-length of dactylus, distal portion unarmed, hiatus-like, dorsal margin with row of long fine setae; pollex less strongly curved compared to dactylus, its cutting edge armed with two large teeth intercalating with dactylar teeth ( Fig. 3f, g ).

Second pereiopod slender; ischium unarmed on ventrolateral surface; merus about 1.4 times as long as ischium; carpus with five subdivisions, first slightly longer than sum of remaining four, with ratio approximately equal to 4.0/1.0/0.7/0.7/1.2; chela much longer than distal-most carpal subdivision, simple ( Fig. 2c ). Third pereiopod moderately robust; ischium with two cuspidate setae on ventrolateral surface; merus about five times as long as wide, unarmed; carpus almost 0.6 times length of merus, noticeably more slender, with small spiniform seta distoventrally; propodus not noticeably longer than carpus, with three widely spaced spiniform setae on ventral margin, in addition to two spiniform setae near dactylar base, one of them much longer; dactylus about half-length of propodus, moderately slender, conical, simple, smoothly curving distally ( Fig. 2d, e ). Fourth pereiopod more slender than third pereiopod; ischium with one very small cuspidate seta on ventrolateral surface; merus almost five times as long as wide; carpus half-length of merus, more slender, with small spiniform seta distoventrally; propodus distinctly longer than carpus, with three spiniform setae on ventral surface, in addition to one pair of spiniform setae distoventrally, adjacent to dactylus; dactylus about half-length of propodus, similar to that of third pereiopod ( Fig. 2f ). Fifth pereiopod more slender than fourth pereiopod; ischium unarmed; merus more than six times as long as wide, unarmed; carpus noticeably more slender than merus, about 0.8 times length of merus, unarmed distoventrally; propodus long, slender, 1.2 times as long as carpus, with few rows of serrulate setae forming moderate cleaning brush on distal ventrolateral surface, ventromesial margin with one stout and several weaker spiniform setae, distal margin with one pair of longer spiniform setae; dactylus about 0.4 times length of propodus, very slightly curved, otherwise similar to that of third and fourth pereiopods ( Fig. 2g, h ).

Second pleopod with appendix masculina much shorter than appendix interna, furnished with five stiff setae on apex and subapical area ( Fig. 1h ). Uropod with lateral lobe of protopod ending in blunt tooth; exopod broadly ovoid, with sharp distolateral tooth and well-developed distolateral spiniform seta; diaeresis sinuous, with strong subtriangular tooth mesial to spiniform seta; endopod as long as exopod, ovoid, without specific features ( Fig. 1i ).

Colouration. Semitranslucent creamy-whitish, chelipeds hyaline-white, yolk-yellow ovaries visible due to translucence of carapace integument ( Figs. 4 , 5 ).

Type locality. Darsait (also spelled as Darsayt), near Muscat, Oman .

Distribution. Indo-West Pacific: Oman (near Muscat), Iran ( Qeshm Island in the Persian Gulf), Philippines (Panglao), possibly also in central Indonesia ( Flores) and Solomon Islands (New Georgia). However, see remarks on the material from the Solomon Islands and Indonesia tentatively identified as S. cf. durisi sp. nov. below.

Ecology. Intertidal and shallow subtidal (less than 2 m) sand flats or sandy-rocky flats, typically associat- ed with burrows. The Iranian specimen was collected together with the callianassid ghost shrimp, Neocallichirus calmani ( Nobili, 1904) ; for all the other specimens, the hosts remain unknown, but suspected to be large burrowing callianassids.

Etymology. The new species is named after the authors’ colleague, Dr. Zdeněk Ďuriš (University of Ostrava, Czech Republic), a well-known expert of caridean shrimps.

Remarks. Salmoneus durisi sp. nov. belongs to a small group of species characterised by both chelipeds enlarged, equal or subequal in size, however, more or less asymmetrical in shape. These species are: S. sketi Fransen, 1991 , S. erasimorum Dworschak, Anker & Abed-Navandi, 2000 , S. caboverdensis Dworschak, Anker & Abed-Navandi, 2000 (all three from the eastern Atlantic), S. degravei Anker, 2010 (from the western Atlantic), S. seticheles Anker, 2003 , S. brucei Komai, 2009 , and S. yoyo Anker, Firdaus & Pratama, 2014 (all three from the Indo-West Pacific) ( Fransen 1991; Dworschak et al. 2000; Anker 2003, 2010; Komai 2009; Anker et al. 2014). In some other species of Salmoneus , the minor cheliped is comparatively larger than in the majority of species of the genus, but is still noticeably smaller, shorter and/or less robust than the major cheliped ( Anker 2010, 2011). A comprehensive phylogeny of Salmoneus is needed to answer the open questions whether all these species form a monophyletic group and whether the relatively large minor cheliped represents a derived state (= i.e. relative enlargement of the minor cheliped, once or multiple times) or an ancestral condition (= both chelipeds ancestrally large, followed by miniaturisation in some clades) within this lineage. Noteworthy, in the holotype of S. durisi sp. nov., the minor chela is noticeably more robust than the major chela ( Figs. 3c, f , 4 , 5 ).

The presence of rows of long fine setae on the ventral and dorsal margins of the major and minor chelipeds ( Fig. 3 ) in S. durisi sp. nov. immediately separates the new species from S. sketi , S. erasimorum , S. caboverdensis , S. degravei and S. yoyo , in which these setae are absent (cf. Fransen 1991; Dworschak et al. 2000; Anker 2010; Anker et al. 2014). On the other hand, their presence, as well as the general shape and armature of the minor chela, place S. durisi sp. nov. closer to S. seticheles and S. brucei (cf. Anker 2003; Komai, 2009).

Salmoneus durisi sp. nov. can be distinguished from S. seticheles by (i) the noticeably more robust third to fifth pereiopods, with the dactylus moderately elongate and slender (vs. generally much more slender and with a very slender, elongate, sickle-shaped dactylus in S. seticheles ); (ii) the eyes largely concealed in dorsal view (vs. partly exposed dorsally in S. seticheles ); (iii) the basally much wider rostrum, being almost as long as wide (vs. 1.5 times longer than wide in S. seticheles ); (iv) the distoventral margin of the rostrum unarmed (vs. with a small subdistal tooth in S. seticheles ); (v) the absence of a rostral carina (vs. its presence, albeit in a moderate form, in S. seticheles ); and (vi) the less slender telson, being less than 2.5 times as long as its proximal width (vs. almost three times in S. seticheles ) (cf. Anker 2003: fig. 2A, D, M, 3E, G). The identity of the species from the Red Sea represented by a single cheliped and tentatively identified as S. aff. seticheles by Ďuriš & Horká (2016), as well as the interesting cheliped polymorphism in S. seticheles ( Anker 2003) will be discussed elsewhere (Anker, in prep.).

Salmoneus durisi sp. nov. is readily distinguishable from S. brucei , for instance, by (i) the presence of orbital

(extra-corneal) teeth (vs. their absence in S. brucei ); (ii) the cutting edges of the major chela with more numerous teeth, around 17 (vs. only 7–9 in S. brucei ); (iii) the posterior margin of the telson with a fairly deep median notch (vs. straight in S. brucei ); (iv) the uropodal exopod with a moderately developed distolateral spiniform seta (vs. with a very long, robust spiniform seta in S. brucei ) (cf. Komai 2009: figs. 2B, D, H, 3C, D).

Despite the absence of the marginal setal rows on the chelipeds of S. erasimorum , S. caboverdensis and S. degravei , these three species show various degrees of morphological similarity to S. durisi sp. nov., especially in the general configuration of the major and minor chelipeds ( Dworschak et al. 2000; Anker 2010). For instance, in S. caboverdensis , the fingers of the minor chela are strikingly dissimilar, with the dactylus strongly curved ventrally and reaching far beyond the pollex (cf. Dworschak et al. 2000: fig. 31); this configuration of the minor chela is remarkably similar to that of the new species. In S. degravei , the fingers of the minor chela are rather similar in length, but the dactylus is extremely curved and slightly bent backwards (cf. Anker 2010: fig. 9c), resembling the condition of S. durisi sp. nov. However, S. durisi sp. nov. can be easily separated from both S. caboverdensis and S. erasimorum , in addition to the setal fringe on the chelipeds, also by the absence of a rostral carina and cuspidate setae on the cheliped ischia (vs. their presence in these two species), and from S. degravei by the well-developed orbital teeth (vs. reduced in S. degravei ), the rounded lateral plate on the coxa of the third maxilliped (vs. produced posteriorly in S. degravei ) and the presence of a notch on the posterior margin of the telson (vs. its absence in S. degravei ) (cf. Dworschak et al. 2000; Anker 2010). On the other hand, S. sketi (a cave-dwelling species) and S. yoyo each display a series of unique characters and are not closely related to S. durisi sp. nov. (cf. Fransen 1991; Anker et al. 2014). This is also the case of several species of Salmoneus with only partly enlarged minor cheliped, such as S. camaroncito Anker, 2010 , S. paulayi Anker, 2011 , S. komaii Anker, 2011 , and S. poupini Anker, 2011 , all morphologically very different from the herein described new species (cf. Anker 2010, 2011).

The two species of Salmoneus presently known based on incomplete specimens lacking major chelipeds, viz. S. hilarulus ( De Man, 1910) and S. tafaongae Banner & Banner, 1966 , are clearly different from S. durisi sp. nov. The former species differs from S. durisi sp. nov. in the general proportions of the third pereiopod, especially the unusually stout dactylus, and the shallower rostro-orbital notches (cf. De Man 1911: fig. 10, 10g). The latter species can be distinguished from S. durisi sp. nov. by the much longer slender rostrum, reaching to the end of the third article of the antennular peduncle (vs. barely overreaching the distal margin of the first article in the new species), the up-turned orbital teeth (vs. not up-turned in the new species), as well as the more elongate second article of the antennular peduncle, being 1.3 times as long as wide (vs. not much longer than wide in the new species) (cf. Banner & Banner 1966). Although a full redescription of S. tafaongae based on new material will be published elsewhere, it can be already stated here that the chelipeds of this species are very different from those of S. durisi sp. nov. (A. Anker, pers. obs.).

The specimens from the Solomon Islands and Indonesia are here tentatively identified as S. cf. durisi sp. nov. The specimen from the Solomon Islands is a young although already ovigerous individual missing its minor cheliped. Since the minor chela bears several important diagnostic features of the species, the identification of this specimen as S. durisi sp. nov. would be uncertain. The ovigerous specimen from Sumba ( Fig. 6 ) presents a series of differences with the holotype, the most notable being the proportionally larger corneal area of the eyestalks, the presence of short erect setae on most of the body surface (carapace, pleon, telson), and the minor chela dactylus although strongly curved downwards not recurrent posteriorly, as in the holotype (all these features being visible in Fig. 6 ). As most other characters match S. durisi sp. nov., the specimen is herein tentatively assigned to S. cf. durisi sp. nov., awaiting a thorough genetic analysis of this material. However, at least two of the above-mentioned differences (larger cornea and straighter minor chela dactylus) are taxonomically important and could indicate the presence of yet another undescribed species, closely related to S. durisi sp. nov., in central Indonesia.

Figures

FIGURE 1. Salmoneus durisi sp. nov.: holotype, ovigerous specimen (cl 5.0 mm) from Darsait, Oman, OUMNH.ZC. 2015- 08-030 [a–i]; non-ovigerous specimen (cl 4.3 mm) from Panglao, Philippines, MNHN-IU-2014-20783 [j]; a—frontal region, dorsal view; b—same, lateral view; c—posterior pleonites, lateral view; d—telson, dorsal view; e—same, posterior margin, dorsal view; f—tooth on ventromesial carina of first article of antennular peduncle, lateral view; g—antennal scaphocerite, dorsal view; h—second pleopod, appendix interna and appendix masculina, lateral view; i—uropod, dorsal view; j—rostro-orbital area of carapace and right eyestalk, lateral view.

FIGURE 2. Salmoneus durisi sp. nov.: holotype, ovigerous specimen (cl 5.0 mm) from Darsait, Oman, OUMNH.ZC. 2015-08- 030; a—third maxilliped, lateral view; b—same, tip of ultimate article, lateral view; c—second pereiopod, lateral view; d—third pereiopod, lateral view; e—same, distal portion of carpus, propodus and dactylus, mesial view; f—fourth pereiopod, lateral view; g—fifth pereiopod, lateral view; h—same, distal portion of carpus, propodus and dactylus, mesial view.

FIGURE 3. Salmoneus durisi sp. nov.: holotype, ovigerous specimen (cl 5.0 mm) from Darsait, Oman, OUMNH.ZC. 2015- 08-030; a—major cheliped, mesial view; b—same, lateral view; c—same, carpus and chela, ventromesial view; d—same, chela fingers opened, ventrolateral view; e—minor cheliped, lateral view; f—same, carpus and chela, ventromesial view; g—same, chela, ventrolateral view.

FIGURE 4. Salmoneus durisi sp. nov.: holotype, ovigerous specimen (cl 5.0 mm) from Darsait, Oman, OUMNH.ZC. 2015- 08-030; a—living individual, dorsal view, left side of carapace slightly damaged; b—same, lateral view (both photographs by the first author).

FIGURE 5. Salmoneus durisi sp. nov.: holotype, ovigerous specimen (cl 5.0 mm) from Darsait, Oman, OUMNH.ZC. 2015-08- 030, living individual, frontal view, left side of carapace slightly damaged (photograph by the first author).

FIGURE 6. Salmoneus cf. durisi sp. nov.: ovigerous specimen (cl 4.7 mm) from Kanawa Island west of Flores, Indonesia, MZB Cru 4977; a—living individual, dorsal view; b—same, lateral view (both photographs by the first author).