Synalpheus pentaspinosus, Ashrafi & Sari & Naderloo, 2020

Ashrafi, Hossein, Sari, Alireza & Naderloo, Reza, 2020, A new sponge-dwelling species of Synalpheus Spence Bate, 1888 (Decapoda Caridea: Alpheidae) from the Persian Gulf, Zootaxa 4861 (3), pp. 338-348 : 339-347

publication ID	https://doi.org/ 10.11646/zootaxa.4861.3.2
publication LSID	lsid:zoobank.org:pub:2C2BE3D2-6286-4F36-90A6-920B60367D2B
DOI	https://doi.org/10.5281/zenodo.4416495
persistent identifier	https://treatment.plazi.org/id/03E0F739-A661-CA27-2694-FE43FA6AECC4
treatment provided by	Plazi
scientific name	Synalpheus pentaspinosus
status	sp. nov.

Treatment

Synalpheus pentaspinosus View in CoL n. sp.

( Figs. 1 4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 )

Type material. Holotype: male (CL 7.1 mm), MNHN-IU-2014-1221, Iran, Persian Gulf , western Larak Island, Keshti-Sukhteh, 26°52’7.38”N, 56°19’31.97”E, sandy with rubbles and many corals, shallow subtidal, 11 May 2019, coll. H. Ashrafi, S. Pazoki & R. Abdollahi GoogleMaps . – Allotype: 1 female (CL 7.9 mm), MNHN-IU-2014-1222, same collection data as for holotype, (photo voucher 4135) GoogleMaps . – Paratypes: 1 male (CL 6.7 mm), 1 female (8.4 mm), MNHN-IU-2014-1223, same collection data as for holotype, 10 May 2019, (photo vouchers: female 3932, male 3933) GoogleMaps ; 1 ovigerous female (CL 7.2 mm), MNHN-IU-2014-1224, Iran, Persian Gulf , Abu-Musa Island, Qadir Park, 25°89’58”N, 55°04’23”E, sandy/rocky with live corals, 19 Jul. 2019, coll. H. Ashrafi, (photo voucher 5028); 1 male (Cl 6.9 mm), ZUTC 6495 , Iran, Persian Gulf, Abu-Musa Island, Qadir Park, 25°89’58”N, 55°04’23”E, sandy/rocky with live corals, 08 May 2016, coll. H. Ashrafi ; 1 male (CL 7.1 mm), 1 female (6.8 mm), ZUTC 6653 , Iran, Persian Gulf , northeast of Larak Island, 26°53’03”N, 56°24’03”E, sandy/rubble with corals, low intertidal, 02 Feb. 2018, coll. H. Ashrafi GoogleMaps (preserved together with small part of host sponge).

Comparative material. S. quinquedens . 1 male (CL 5.52 mm), 1 female (CL 6.24 mm), MNHN-IU-2019- 3150, south Madagascar, Atimo-Vatae Expedition , Sta. TB-11, 25°09.2’S, 46°45.4’E, 5–6 m, 12 May 2010 GoogleMaps ; 1 male (CL 7.38 mm), 1 female (CL 8.08 mm), MNHN-IU-2014-1225, Iran, Persian Gulf , Farur Island, 26°17’43.63”N, 54°29’5.21”E, shallow subtidal, 29 Dec. 2017, coll. H. Ashrafi (photo vouchers: male 4393, female 4407) GoogleMaps ; 3 malefemale pairs (CL of males 6.5, 6.9, and 7 mm, CL of females 9.4, 9.6, and 9.7 mm), MNHN-IU-2014-1226, Iran, Persian Gulf , Siri Island, 25°53’53.17” N, 54° 31’ 22.24” E, subtidal, 08 Feb. 2017, coll. H. Ashrafi & A. Sari (photo voucher 1595) GoogleMaps ; 2 males and 4 females (CL indet.), ZUTC 6908 , same collection data as for previous specimens GoogleMaps ; 1 female, OUMNH. ZC 2020.01 .022, Kuwait, eastern Failaka Island , rocky substrate, 24 Dec. 2014, coll. M. Al-Kandari et al. (examined by S. De Grave).

Description. Medium-sized species of Synalpheus . Carapace ( Figs. 1 View FIGURE 1 A–C) sparsely setose, with deep cardiac notch; lower margin with some short setae; rostrum subacute, slightly tapering distally, about 2.5 times as long as wide, reaching almost to middle of first antennular article, slightly up-turned in lateral view, with two setae at tip; orbital teeth subtriangular, subacute, about two times as wide as rostrum at base, slightly falling short of rostrum, nearly as long as wide, with two or three setae at tip; frontal margin between rostrum and orbital teeth deeply concave, curved on orbital tooth side, straight on rostrum side; pterygostomial angle bluntly protruding.

Each eye ( Fig. 1B View FIGURE 1 ) with well-developed cornea and small blunt projection anteriorly.

Pleon showing sexual dimorphism on first to fourth pleonites, with subacute projections, as described below, in males, rounded antero- and postero-ventrally in females. Male pleon ( Fig. 1C View FIGURE 1 ) with first pleuron bearing small subacute projection antero-ventrally and ventrally pointing, hook-shaped projection postero-ventrally; second pleuron slightly angled antero-ventrally, with subacute triangular projection postero-ventrally; third pleuron bearing small blunt projection antero-ventrally, slightly projecting postero-ventrally; fourth pleuron rounded antero-ventrally, angular postero-ventrally; fifth pleuron rounded antero- and postero-ventrally. Sixth pleonite in both sexes ( Fig. 1C, D View FIGURE 1 ) armed with five strong sharp teeth on posterior margin, most-lateral teeth flanking telson stronger than remaining teeth.

Telson ( Fig. 1D View FIGURE 1 ) subrectangular, tapering distally, with shallow mid-dorsal depression starting from 0.3 length of telson and almost reaching posterior end of telson, broadening posteriorly; dorsal surface with two pairs of spiniform setae on 0.3 and 0.7 length of telson, respectively; posterolateral angles slightly projecting; posterior margin broad, rounded, with two pairs of spiniform setae, one pair near each posterolateral angle, mesial spiniform setae about twice as long as lateral ones. Uropod with protopod armed with two sharp teeth, lateral longer than mesial; exopod bearing stout disto-lateral tooth; diaeresis sinuous, lateral margin with stout acute tooth, almost as long as disto-lateral tooth of exopod; disto-lateral spiniform seta adjacent to diaresis stout, overreaching both teeth, but not reaching beyond posterior margin of exopod; endopod narrowly ovate, with several clusters of setae on dorsal surface.

Antennule ( Fig. 1A, B View FIGURE 1 ) relatively slender; first article longest, about twice as long as wide, with several short setae on distodorsal and mesial margins; stylocerite subacute, extending well beyond distal margin of first article, but not reaching mid-length of second article; second article nearly 0.8 times as long as first, about 1.5 times as long as wide, bearing short setae disto-dorsally, with scattered setae mesially; third article slightly shorter than second; lateral flagellum biramous; fused portion consisting of seven or eight units; aesthetascs extending from fifth fused unit to end of shorter ramus.

Antenna ( Fig. 1A, B View FIGURE 1 ) with very robust basicerite, armed with stout subacute disto-dorsal tooth and stouter, longer disto-ventral tooth, latter reaching to tip of antennular stylocerite; lateral tooth of scaphocerite very strong, exceeding antennular peduncle, blade narrow, reaching to about 0.7 length of disto-lateral tooth, with short marginal setae. Carpocerite slender, extending well beyond scaphocerite and antennular peduncle.

Mouthparts not dissected. Third maxillipeds ( Fig. 1E View FIGURE 1 ) pediform; coxa and basis fused; lateral plate with small, laterally pointing, acute projection, mesial surface with short setae; antepenultimate article trigonal in cross section, about four times as long as wide, concave proximo-mesially, margins furnished with long setae; penultimate article short, about one fourth as long as antepenultimate article; ultimate article slender, nearly as long as antepenultimate article; tip with crown of eight or so slender spiniform setae; exopod slender, approximately reaching to end of antepenultimate article.

First pereiopods very unequal in size and asymmetrical in shape. Major cheliped ( Fig. 2 View FIGURE 2 A–C) robust, with ischium short, about 1.5 times as wide as long; merus robust, somewhat swollen, about twice as long as high, with small subacute projection disto-dorsally, shallowly concave ventrally; carpus short, cup-shaped; palm tumid, subcylindrical, smooth, with prominent rounded lobe and three small bumps disto-dorsally; dactylus 1.3 times as long as pollex and 0.4 times as long as palm, curved distally. Minor cheliped ( Fig. 2 View FIGURE 2 D–F) with basis short, slightly longer than wide, with few long setae on ventral margin; ischium oblique distally, bearing some long setae ventrally; merus approximately six times as long as ischium, tapering distally, about 3 times as long as its widest part, furnished with long setae along ventral margin and short setae on dorsal margin, shallowly concave ventrally, terminating in small obtuse projection disto-dorsally; carpus vase-shaped, about 0.4 as long as merus; chela nearly as long as merus; palm ovoid, subcylindrical, about 1.2 times as long as fingers; fingers subequal in length; pollex with one short row of setae mesially and one laterally, with simple, non-bidentate tip; dactylus with medium-sized depression on cutting edge, with simple, non-bidentate tip; two prominent rows of setae present, one mesially and one dorsally.

Second pereiopod ( Fig. 3A View FIGURE 3 ) relatively slender; coxa with small tooth distodorsally; basis short; ischium slen- der, about 3.5 times as long as widest part; merus slender, about 1.2 times longer than ischium, five times as long as broad, with long setae ventrally; carpus slightly longer than merus, with five units (subarticles) approximate ratio 5: 1: 1: 1: 2; chela about half of merus length.

Third pereiopod ( Fig. 3B View FIGURE 3 ) more robust than other walking legs; coxa with small distodorsal lobe; ischium slightly longer than basis, about 1.3 as long as its widest part; merus robust, broadened, slightly spindle-shaped, three times as long as widest part, about 2.2 as long as carpus; carpus about 2.3 times as long as wide, with one spiniform seta distoventrally; propodus about 1.8 times longer than carpus, bearing seven or eight spiniform setae along ventral margin, not including one distal pair, adjacent to dactylus; dactylus biunguiculate, with dorsal unguis slightly longer than ventral unguis, latter slightly broader at base than dorsal unguis.

Fourth pereiopod ( Fig. 3C View FIGURE 3 ) generally similar to third pereiopod, less robust; coxa with one disto-dorsal lobe; merus about 2.3 times as long as ischium; carpus with one spiniform seta disto-ventrally; propodus with seven spiniform setae on ventral margin and one pair distally, adjacent to dactylus.

Fifth pereiopod ( Fig. 3 View FIGURE 3 D–E) more slender than other walking legs; coxa without disto-dorsal lobe; ischium about twice as long as widest part, approximately as long as basis; merus about four times as long as broad, nearly 2.3 times as long as ischium; carpus slender, about 0.7 as long as merus, without disto-ventral spiniform seta; propodus slightly longer than carpus, with three spiniform setae ventrally and one pair distally, adjacent to dactylus, and with five transverse rows of serrulate setae on distal half of ventro-mesial margin forming cleaning brush; dactylus similar to that of third pereiopod.

Etymology. The new species name refers to the presence of five sharp spine-like teeth on the sixth pleonite, one of its main diagnostic features; used as an adjective.

Ecology. All specimens were found inside sponge canals in the low intertidal and shallow subtidal areas. The host sponges were either partly overgrowing on hard corals or were growing within a mixture of cobble, rocks, coral and coral rubble. The same sponges were also found in the intertidal and shallow subtidal areas without corals. However, these sponges were occupied by another, presumably undescribed species of Synalpheus from the S. tumidomanus species complex (H. Ashrafi, pers. obs.).

Remarks. The new species belongs to a small morphologically distinctive group of Synalpheus , in which the posterior margin of the sixth pleonite is armed with strong teeth. Whether this group is monophyletic remains to be shown. Based on the shape of the rostrum and orbital teeth, this group can be further subdivided into three smaller subgroups. The first subgroup includes S. bispinosus De Man, 1910 , S. quadrispinosus De Man, 1910 , S. quinquedens Tattersall, 1921 and S. pentaspinosus n. sp., all with the rostrum and orbital teeth being subequal in length and with the orbital teeth distinctly wider than the rostrum. The second subgroup is comprised of S. triacanthus De Man, 1910 , S. trispinosus De Man, 1910 and S. cretoculatus Banner & Banner, 1979 , in which the rostrum is significantly longer and much more slender than the orbital teeth (cf. De Man 1911; Banner & Banner 1979). The third subgroup includes only S. septemspinosus De Man, 1910 , which is characterised by small orbital teeth and rostrum, the latter also being longer relative to orbital teeth (cf. De Man 1911).

Apart from the difference in the number of teeth on the posterior margin of sixth pleonite (two in S. bispinosus , four in S. quadrispinosus and five in S. quinquedens and S. pentaspinosus n. sp.), the members of the first subgroup are very similar to each other (cf. De Man 1911; Tattersall 1921). Nevertheless, S. pentaspinosus n. sp. can be separated from S. bispinosus , in addition to the difference in the armature on the sixth pleonite, by disto-dorsal projection of the major cheliped palm which is less robust than S. bispinosus . Furthermore, according to De Man (1911), in S. bispinosus , the “outer margin of the dactylus [of the minor chela is] fringed with rather long, stiff setae from the articulation to the tip”. In contrast, in S. pentaspinosus n. sp., this margin bears two rows of setae. Similarly, the minor chela dactylus of S. quadrispinosus seems to bear only one distinct row of setae, not two, as in the new species. In S. quadrispinosus , the color of the major chela is pink in its distal half ( Anker & De Grave 2016: fig. 49), whilst it is brownish orange and brownish green in females and males of S. pentaspinosus n. sp., respectively ( Fig. 4A, B View FIGURE 4 ).

In having the same number of teeth (five) on the sixth pleonite, S. pentaspinosus n. sp. appears to be closest to S. quinquedens ( Fig. 5 View FIGURE 5 ). However, the two species can be discriminated by some morphological characters, as well as by the color of the ovaries / eggs. In the new species, the minor chela dactylus is furnished with two rows of setae, one mesial row and one dorsal row, this configuration being different from that of S. quinquedens , with only one prominent mesial row of setae ( Fig 6C, D View FIGURE 6 ). In S. pentaspinosus n. sp., the minor chela dactylus bears a small, but rather obvious concavity on the cutting edge, which is not distinct in S. quinquedens . It is important to note here that Tattersall’s (1921) figures of S. quinquedens appear to be somewhat diagrammatic and may therefore be inaccurate. For instance, according to Tattersall (1921: pl. 28, fig. 1), the orbital teeth of the type of S. quinquidens are very broad and in fact appear to be broader than in the new species. However, our examination of the material of S. quinquedens from Iran and Madagascar showed that this character cannot be used in discrimination of S. pentaspinosus n. sp. from S. quinquedens , as smaller specimens of the latter species bear relatively narrower orbital teeth ( Fig. 6A View FIGURE 6 ). In life, S. pentaspinosus n. sp. and S. quinquedens can be distinguished by the color of ovaries, eggs and possibly also by corneal pigments. Females of S. pentaspinosus n. sp. show yellow to yellow-orange ovaries and orange-red eggs ( Fig. 4B, C View FIGURE 4 ), whilst females of S. quinquedens have greenish ovaries and eggs ( Fig. 5B View FIGURE 5 ). The corneas of S. pentaspinosus n. sp. vary from pinkish to reddish ( Fig. 4 View FIGURE 4 ), being darker brownish in S. quinquedens ( Fig. 5 View FIGURE 5 ).