Salmoneus rashedi, Ashrafi & Ďuriš & Naderloo, 2020

Ashrafi, Hossein, Ďuriš, Zdeněk & Naderloo, Reza, 2020, A new species and a new record of alpheid shrimps of the genus Salmoneus Holthuis, 1955 (Crustacea: Decapoda: Alpheidae) from Iran, Zootaxa 4838 (4), pp. 503-514 : 504-510

Salmoneus rashedi n. sp.

( Figs 1 4 )

Type material. Holotype: non-ovigerous spm (CL 5.1 mm), MNHN-IU-2016-1512, Khamasi , Hengam Island, Persian Gulf, 26° 38’ 3.24” N, 55° 51’ 1.68” E, rocky and sandy bottom with boulders, shallow subtidal and low intertidal zones, 5 Jan. 2019, coll. H. Ashrafi (fcn IRN.19-103) . – Paratypes: 2 non-ovigerous spms, ZUTC 6636 , Keshti Sukhteh , Larak Island , Persian Gulf, 26° 53’ 2.65” N, 56° 24’ 2.98” E, sandy with boulders and live and dead corals, 2 Feb. 2018, coll. H. Ashrafi. – 1 non-ovigerous spm, ZUTC 6637 , Ramchah, Qeshm Island, Persian Gulf, 26° 53’ 42.81” N, 56° 09’ 41.09” E, rocky with boulders, 30 Jan. 2018, coll. H. Ashrafi. – 1 ovigerous spm (CL 5.9 mm, MNHN-IU-2016-1513, Keshti Sukhteh, Larak Island, Persian Gulf, 26° 53’ 2.65” N, 56° 24’ 2.98” E, sand with boulders and corals, 09 May 2019, coll. H. Ashrafi & S. Pazoki (fcn IRN.19-105). – 1 non-ovigerous spm (CL 5.4 mm), MNHN-IU-2016-1514, Qadir Park, Abu-Musa Island, Persian Gulf, 25° 89’ 58” N, 55° 04’ 23” E, sandy and rocky bottom with corals, 19 Jul. 2019, coll. H. Ashrafi (fcn IRN.19-114). – 1 non-ovigerous spm (CL 4.0 mm), ZUTC 6635 , Qadir Park, Abu-Musa Island, Persian Gulf, 25° 89’ 58” N, 55° 04’ 23” E, in coral, with Alpheus alcyone , 17 Jul. 2019, coll. H. Ashrafi (fcn IRN.19-115) .

Other material. 2 non-ovigerous spms (CL 4.3, 4.5 mm), UO.IRN.16-104. Tis , Chabahar Bay , Gulf of Oman, 25° 21’ 0.16” N, 60° 35’ 49.63” E, rocky bed with boulders, 29 Dec. 2016, coll. H. Ashrafi. – 2 ovigerous spms (CL 6.9, 7.2 mm), MNHN-IU-2016-1515, Tis village, Chabahar Bay, Gulf of Oman, 25° 21’ 0.16” N, 60° 35’ 49.63” E, sandy/rocky bottom with boulders, 23 Apr. 2019, coll. H. Ashrafi (fcn IRN.19-109) .

Description. Medium-sized Salmoneus species. Carapace ( Figs. 1 A–C) scarcely, mainly dorsally setose, with small postrostral tubercle and deep cardiac notches; rostrum acute, long, reaching nearly to middle of third antennular segment, about 1.5 times as long as wide, bearing distinct median dorsal crest on distal 4/5 of length, ventral margin with small tooth subdistally (sometimes inconspicuous or fully reduced, absent); extracorneal teeth smooth, acute, reaching to about middle of first antennular segment, clearly longer than wide, almost fully covering eyes dorsally; branchiostegal suture obsolete, inconspicuous; pterygostomial angle rounded.

Pleon ( Fig. 1E ) with first to third pleonal somites with pleura rounded antero- and posteroventrally; fourth and fifth pleura bearing small acute projection posteroventrally; sixth pleonal segment with preanal plate bearing round median projection posteriorly, pleura with subacute projections laterally, posteroventral angle separated by incomplete suture.

Telson ( Fig. 1D ) subrectangular, tapering distally, posterior margin with two pairs of spiniform setae laterally and medium-sized rectangular median notch harbouring pair of plumose submedian setae.

Antennula ( Fig. 1B, C ) with peduncular segments stout; first segment nearly twice as long as second segment, with setae on dorsodistal margin, stylocerite acute, slightly extending beyond second antennular segment; second peduncular segment nearly broader than long, bearing setae dorsally on distal margin; third segment slightly longer than broad, longer than second one. Lateral flagellum biramous, fused part composed of 2 segments, shorter free ramus with about 10 segments and 7–8 groups of aesthetascs.

Antenna ( Fig. 1B, C ) with lateral tooth of scaphocerite subequal to antennular peduncle, squame subequal to lateral tooth. Basicerite with inferior tooth subacute, bearing small rounded projection near tip superiorly; superior part with small rounded projection. Carpocerite stout, reaching to about 0.7 of scaphocerite length and to end of second segment of antennular peduncle.

Mouth parts not dissected. Third maxillipeds ( Fig. 2A ) with coxa and basis fused, coxa bearing broadly rounded lateral plate and strap-like epipod, exopod not reaching to end of antepenultimate segment; antepenultimate segment slender, subequal to combined length of two distal segments; penultimate segment nearly three times as long as broad, length about 0.35 of antepenultimate segment; ultimate segment length equal to 0.65 of antepenultimate segment, heavily setose on sides of ventral margin, with several long terminal setae; multilamellate arthrobranch present on praecoxa.

Pereiopods all with coxa bearing setobranchs and, except fifth leg, also strap-like epipod. First pereiopods strongly asymmetrical in size and shape. Major cheliped ( Fig. 2 B–F) robust, carried flexed under body when not in use; ischium unarmed; merus slender, about six times as long as distal width, flattened or slightly concave in ventral face; palm with deep groove proximo-ventrally on outer face ( Fig. 2 B ), slightly convex ventrally, ventromedial margin bearing 2–4 feebly conspicuous tubercles ( Fig. 2D ), dorsal side with shallow longitudinal depression; fingers slightly shorter than palm, with 13–14 small subequal teeth along cutting edges except most distal part, apices acute and strongly hooked.

Minor cheliped ( Fig. 3A ) simple, moderately stout, small; ischium bearing single ventrolateral spinule; merus slightly longer than both ischium or carpus; chela length about 0.8 of carpal length, fingers subequal to palm length, simple, slender, tapering distally.

Second pereiopod ( Fig. 3B ) slender, ischium with single proximo-ventral spinule on outer side, merus subequal to ischium length, carpus composed of 5 segments, proximal one reaching 0.7 of merus length and longer than remaining distal carpal segments combined, carpal segments length ratios 7: 1.5: 1: 1: 2; chela small, subequal to combined length of two distal carpal segments, and to about 0.5 of first (proximal) carpal segment, fingers subequal to palm length, slender, tapering distally.

Third pereiopod ( Fig. 3C ) with ischium about 4 times longer that deep distally, bearing 2–3 spinules ventrolaterally; merus about 1.5 times as long as ischium and uniformly deep as distal ischium; carpus more slender and about 0.75 of merus length, with single thin spinule distoventrally; propodus as slender as carpus and nearly as long as merus, bearing three to four short single ventral spinules, with pair of distoventral spines from which longer one reaching almost half of dactylus length; dactylus simple, about 0.45 of propodus length, slender, slightly curved, tapering distally, bearing one to two setae dorso-distally.

Fourth pereiopod ( Fig. 3D ) similar to third one; ischium about 4 times longer that deep distally, bearing 2–3 spinules ventrolaterally.

Fifth pereiopod ( Fig. 3E ) similar to preceding two legs but more slender; ischium 3 times longer than deep, unarmed; merus almost twice as long as ischium, carpus subequal to merus length; propodus about 1.5 times longer than carpus, with 11 densely spaced transverse rows of cleaning setae on distal half of ventral margin and several small single and more widely spaced spinules proximally, distoventral spine long, about half of dactylus length.

Uropod ( Fig. 1D ) with protopodite produced into lateral tooth; exopod with lateral margin nearly straight, diaeresis well developed, sinuous, distolateral tooth well developed, medially with movable spinule more than twice as long as lateral tooth; endopod ovoid, simple.

Variations. Most paratypes are morphologically consistent with the holotype, with only minor differences observed. The two largest specimens (MNHN-IU-2016-1515) have their carapace distinctly more swollen dorsally than the holotype and remaining paratypes, the ventral tooth of their rostrum is absent, and the major chela is not provided with conspicuous ventromedial tubercles on the palm. The specimen MNHN-IU-2016-1514 has only two (instead of three) ischial spinules on the third and fourth pereiopods.

Etymology. This species is named after Rashed Abdollahi, a wonderful and supportive friend of the first author (HA) and excellent photographer who patiently took hundreds of photos of caridean shrimps including the new species.

Remarks. Based on the relatively long slender rostrum with a small subdistal tooth on the ventral margin, the carapace with a small postrostral tubercle, the major chela with small teeth along almost the entire cutting edges, the ischium of the second pereiopods with a well-developed spinule, and slender dactyli of the third to fifth pereiopods, the new species is most similar to species of the S. gracilipes species group, as defined by Anker & Marin (2006). This group now comprises, besides 5 Atlantic congeners (Anker 2010), also 6 Indo-West Pacific species, i.e. S. alpheophilus Anker & Marin, 2006 ; S. colinorum De Grave, 2004 ; S. gracilipes Miya, 1972 ; S. pusillus Anker & Marin, 2006 ; S. seticheles Anker, 2003a ; and S. singaporensis Anker, 2003b .

The central and eastern Pacific S. colinorum can easily be distinguished from S. rashedi n. sp., by the long dorsal rostral carina reaching behind the eye, the rostrum reaching to about the end of the second antennular segment, the lack of the notch on the posterior margin of the telson and the lack of ischial spinules on both the minor first pereiopod and the second pereiopods ( De Grave 2004), while in S. rashedi n. sp. the rostral carina does not reach the eye, the rostrum reaches to about the middle of the third segment of the antennular peduncle, there is a mediumsized notch on the posterior margin of the telson, and a single ischial spinule is present on each the minor first pereiopod and the second pereiopods. Salmoneus colinorum also differs by its coloration with distinct transverse red bands on the body as described by De Grave (2004), and photographed by Anker (2019: Fig. 6).

Salmoneus seticheles , named by Anker (2003a) due to the presence of long setae on the lower and upper margins of the larger first cheliped, is easily distinguishable from S. rashedi n. sp., but also by the polymorphic first chelipeds, subequal or unequal, whilst those are strongly unequal in size in the new species, and the shorter rostrum and the eye cornea mostly exposed in the dorsal view ( Anker 2003a).

The weak rostral carina and the postrostral tubercle are the most reliable characteristics distinguishing S. rashedi n. sp. from S. gracilipes which, based on original description ( Miya 1972) lacks that tubercle, and the dorsal rostral carina being very distinct. On the other hand, Miya (1972: Fig. 3B ) figured a ribbed structure on the lower surface of the major chela palm, somewhat similar to the new species. A distoventral rostral tooth was lacking, or perhaps unnoticed, in the type of S. gracilipes , but a small distoventral rostral tooth was subsequently reported by Miya (1984: 86, Fig. 4A ) in an ovigerous specimen from Majuro Atoll. However, the specific affiliation of the latter specimens was queried by De Grave (2004) and Anker & Marin (2006) who suggested it to be S. colinorum (discussed above). It also might be conspecific with the present new species based on the shape and length of the rostrum and extracorneal teeth, and the general shape of the major cheliped and fingers dentition. As this specimen is currently unavailable for study ( De Grave 2004: 47), its specific status is difficult to resolve. Recently, some specimens of S. gracilipes have been reported from Kuwait by Anker et al. (2020); those possess a ventral tooth on the rostrum, a postrostral tubercle on the carapace, 14–15 teeth on the occlusal margins of the major chela, and feebly developed both ventromedial tubercles (figured but not mentioned) as well as dorsal depression on the palm of the major chela, which altogether show them as similar with the present species. Those specimens, however, have the major chela more slender than in the new species, and the ventral rostral tooth is distinctly stronger and subterminal in position (vs small and placed more posteriorly, to the distal third of the rostrum, in the present new species); the dorsal carina was figured overreaching posteriorly the rostrum (vs shorter), the major cheliped bears a single ischial spinule in the Kuwait specimens (vs. lacking in the new species as well as in the Japan specimen), and the third pereiopod bears 2 ischial spinules (vs. 3 in the new species). As suggested by Anker et al. (2020), all material previously reported as S. gracilipes represents a species complex which needs unravelling.

Salmoneus singaporensis with a small rostrum bearing a long rostral carina lacks of a postrostral tubercle on the carapace ( Anker 2003b), eyes largely exposed in dorsal view, and strong proximal teeth on fingers of the major chela, can easily be distinguished from S. rashedi n. sp.

Besides the above species of the S. gracilipes group, a distoventral rostral tooth is also present in S. tafaongae Banner & Banner, 1966 , and S. rostratus Barnard, 1962 . Although the specimens which Banner & Banner (1966) used for the description of S. tafaongae lacked the major cheliped, the characteristics like the absence of a postrostral tubercle and upturned extracorneal teeth can be used to distinguish it from the present new species. Salmoneus rostratus belongs to a very different species group (sensu Anker & Marin 2006), thus easily distinguishable from the new species, e.g., by a size and position of the ventral rostral tooth, and a few large teeth proximally on the major chela fingers, as figured by Barnard (1962: Fig. 1 ) or Anker & Marin (2006: Fig. 14).

The postrostral dorsal tubercle is also seen in two species of the S. gracilipes group, S. alpheophilus and S. pusillus , and it seems that these three species, despite being distinctive, are morphologically close to each other. They however differ from the present new species in the following characters: (1) the rostrum reaches or slightly falling to reach the end of the second antennular segment in S. alpheophilus and S. pusillus , respectively (vs reaches to the middle of the third antennular segment in S. rashedi n. sp.); (2) no rostral carina is seen in S. pusillus whilst it is obsolete in S. rashedi n. sp. and S. alpheophilus ; (3) the eyes are concealed both laterally and dorsally in the new species, but those are mostly exposed and partly visible in the both views in S. alpheophilus and S. pusillus , respectively; (4) only S. rashedi n. sp. bears two to four low tubercles on ventromedial margin of the large cheliped palm while two other species bear the smooth palm; (5) the second pereiopod ischium is armed with a lateral spinule in the new species and S. alpheophilus comparing to an unarmed ischium in S. pusillus ; (6) there is a median notch on posterior margin of telson in S. rashedi n. sp. and S. alpheophilus in comparison to a simple posterior telson margin in S. pusillus ; (7) the colour pattern semi-transparent white and gonads or eggs bright yellow in both S. alpheophilus and S. pusillus (vs semi-transparent yellow or reddish orange with red bands, and gonads or eggs yellow or reddish, in S. rashedi n. sp.).

Coloration. The body of the species is semi-transparent yellow, or reddish orange with red bands crossing the posterior margin of carapace and the first five abdominal segments. The red bands are mostly observable in the field while these bands usually become faint in captivity ( Fig. 4 ).

Ecology. The species lives underneath rocks, boulders or dead corals on sandy substrate. In the intertidal zone, mostly one or rarely two specimens were found under a single boulder or rock, whilst in the shallow subtidal zone groups of three to five specimens under each boulder or dead coral (in the latter case, only one specimen, MNHN- IU-2016-1514; Fig. 4B ) were found.

Distribution. Known only from the Persian Gulf and the Gulf of Oman.

Figures

FIGURE 1. Salmoneus rashedi n. sp., non-ovigerous specimen, holotype MNHN-IU-2016-1512. (A) carapace, lateral view; (B) anterior region of carapace and antennae, dorsal view; (C) same, lateral view; (D) telson and uropods; (E) posterior pleonal somites, lateral view. Scale bars 1 mm.

FIGURE 2. Salmoneus rashedi n. sp., non-ovigerous specimen, holotype MNHN-IU-2016-1512. (A) third maxilliped; (B) major first pereiopod, lateral view; (C) same, medial view; (D) same, chela, dorsomedial view; (E) same, dorsal view; (F) same, medial view. Scale bars 1 mm.

FIGURE 3. Salmoneus rashedi n. sp., non-ovigerous specimen, holotype MNHN-IU-2016-1512. (A) minor first pereiopod; (B) second pereiopod; (C) third pereiopod; (D) fourth pereiopod; (E) fifth pereiopod. Scale bars 1 mm.

FIGURE 4. Salmoneus rashedi n. sp. (A) ovigerous specimen, paratype MNHN-IU-2016-1513; (B) non-ovigerous specimen, paratype MNHN-IU-2016-1514; (C) ovigerous specimen MNHN-IU-2016-1515. Photos by R. Abdollahi (A, B), F. Yusefi (C).