Alpheus shukran, Anker, 2024

Anker, Arthur, 2024, Preliminary revision of Alpheus djeddensis Coutière, 1897 species complex, with description of three new species of goby-associated snapping shrimps and taxonomic notes on A. macellarius Chace, 1988 and A. djiboutensis De Man, 1909 (Decapoda: Alpheidae), Zootaxa 5472 (1), pp. 1-63 : 20-25

publication ID	https://doi.org/ 10.11646/zootaxa.5472.1.1
publication LSID	lsid:zoobank.org:pub:7FA16A7A-7AE7-4081-941B-F797F92F513A
persistent identifier	https://treatment.plazi.org/id/03F52776-FFC9-857F-17C5-FF7FFDC4FA8E
treatment provided by	Plazi
scientific name	Alpheus shukran
status	sp. nov.

Treatment

Alpheus shukran sp. nov.

Figs. 11–14 View FIGURE 11 View FIGURE 12 View FIGURE 13 View FIGURE 14

(?) Alpheus djiboutensis . — Karplus et al. 1972a: 95, figs. 1–6, 10–13; Karplus et al. 1972b: 275; Karplus et al. 1974: 259 (part., A. djiboutensis 1); Karplus et al. 1981: 6, fig. 2G; Karplus 1987: 514, fig. 2G [not A. djiboutensis De Man, 1909 ].

Type material. Holotype: female (cl 18.5 mm), FLMNH UF 71923 , Oman, Masirah Island , west coast (channel side), 20°27’44.0”N / 58°46’39.8”E, muddy sandflat with seagrass, depth 0.5 m, suction pump, in burrow, leg. A. Anker, 08.11.2022 (BOMAN-13057) GoogleMaps . Paratypes: 1 male (cl 7.9 mm), FLMNH UF 71918 , same locality as for holotype, 08.11.2022 (BOMAN-13048) GoogleMaps ; 1 female (cl 6.2 mm), FLMNH UF 71922 , Oman, Masirah Island , west coast (channel side), Ghab, 20°15’19.3”N / 58°37’26.9”E, muddy sandflat, depth less than 0.5 m, suction pump, in burrow, leg. A. Anker, 12.02.2022 (BOMAN-13480) GoogleMaps ; 1 male (cl 11.0 mm), FLMNH UF 68873 , Oman, east of Muscat, Bandar Khayran , 23°30’32.5”N / 58°43’53.5”E, sand- and mudflat near mangroves at night, depth 0.5 m, suction pump, in burrow with goby, leg. A. Anker, 04.02.2022 (BOMAN-11330); 1 ovig. female (cl 13.2 mm), FLMNH UF 68870 , same collection data as for previous specimen (BOMAN-10000) GoogleMaps .

Other material examined. 1 female (12.7 mm), RSRC, Red Sea , Saudi Arabia, Thuwal, KAUST, near Island Recreation Center, 22°18’52.6”N / 39°05’24.5”E, sandflat with sparse rubble, depth 0.5 m, suction pump, in burrow, leg. A. Anker, 10.12.22 (AA-22-397) GoogleMaps .

Diagnosis. Morphology largely as in A. djeddensis . Carapace strongly pitted, except for mid-dorsal portion, covered with short setae. Rostrum well developed, not reaching mid-length of first article of antennular peduncle; rostral carina distinct, blunt, raising above orbital hoods, extending well beyond base of orbital hoods, not reaching mid-length of carapace; orbital hoods unarmed, rounded; adrostral furrows shallow ( Figs. 11A, B View FIGURE 11 , 12A View FIGURE 12 , 13C, G View FIGURE 13 ). Rostro-orbital region moderately protruding beyond anterolateral margin of carapace ( Figs. 12A View FIGURE 12 , 13C, G View FIGURE 13 ). Telson broad, at most 1.5 times as long as wide at base, gently tapering; dorsal surface faintly pitted, with slight mid-dorsal groove and two pairs of stout spiniform setae, latter inserted at considerable distance from lateral margins; posterior margin broadly rounded, with row of slender spiniform setae between two pairs of more robust spiniform setae at each distolateral angle, mesial longer than lateral ( Fig. 12B View FIGURE 12 ). Antennule with stylocerite swollen laterally, its tip falling short of distal margin of first article article of peduncle, ventromesial carina with subtriangular tooth; second article about 2.7 times as long as wide ( Figs. 12A View FIGURE 12 , 13C, G View FIGURE 13 ). Antenna with distoventral margin of basicerite armed with sharp or subacute tooth; scaphocerite with lateral margin gently concave; distolateral tooth barely overreaching distal margin of blade ( Figs. 12A View FIGURE 12 , 13C, G View FIGURE 13 ). Third maxilliped with penultimate article cup-shaped, widening distally, not protruding ventrally, with tuft of moderately elongate setae on distoventral margin. Major cheliped of brevirostris type; merus stout, without tooth on distomesial margin, ventromesial margin with some spiniform setae; chela not elongate; palm about twice as long as wide, with deep transverse groove on dorsal margin, mesial surface faintly granulated; fingers about 0.6 length of palm; plunger of dactylus feebly bulging ( Figs. 12C, D View FIGURE 12 , 13F View FIGURE 13 , 14D View FIGURE 14 ). Minor cheliped distinctly shorter and weaker than major cheliped; merus without tooth on distomesial margin, ventromesial margin with some spiniform setae; chela not elongate; palm about twice as long as wide, without grooves, mesial surface faintly granulated; fingers about 1.1–1.2 times as long as palm, somewhat gaping, not sexually dimorphic, with rows of balaeniceps setae on each side of dactylus and pollex in both sexes ( Figs. 11 View FIGURE 11 , 12E, F View FIGURE 12 , 14E View FIGURE 14 ). Second pereiopod with ratio of carpal subarticles equal to 4.9 / 2.5 / 1.0 / 1.0 / 1.7 ( Fig. 12G View FIGURE 12 ). Third pereiopod moderately slender; ischium armed with stout spiniform seta; merus about 4.7 times as long as maximal width, unarmed; propodus with six or so spiniform setae along ventral margin and one pair of spiniform setae on distoventral angle; dactylus about 0.45 length of propodus, gradually curving distally, spatulate ( Fig. 11B View FIGURE 11 ). Fifth pereiopod ischium armed with spiniform seta. Appendix masculina with stiff setae on apical part and along margin opposed to endopodal ramus ( Fig. 14H View FIGURE 14 ). Uropodal exopod with diaeresis almost straight, except for broad lateral lobe; endopod with row of spiniform setae on distal margin (visible in Fig. 12B View FIGURE 12 ). Colour pattern diagnostic, as described below.

Colour pattern. Background colour pale yellow or pale greenish.Carapace with several transverse (dorsally) and more oblique (laterally), highly irregular, greenish brown or reddish brown bands composed of red chromatophores on blue or bluish brown background; most bands with small pale areas within; anterolateral bands on each side of orbital hoods darker greenish brown or bluish brown; post-rostral area typically with small white patch or streak between eyes. Pleon with transverse green-brown banding consisting of one complete posterior band running across each pleonite and one incomplete anterior band occupying only anterodorsal section of each pleonite, each band with small pale patches or spots within; band on fifth somite incompletely closing; saddle on first pleonite usually conspicuous, whitish yellow, sometimes with reddish patches. Telson with green brown or blue brown transverse band and patches on pale yellow background. Antennular peduncles pale yellow with large brown bluish areas, especially on second article; stylocerite deep blue along lateral margin only; antennal carpocerite olive brown; scaphocerite largely blue marbled with some brown and yellow, and with red orange area proximally; antennular and antennal flagella pale greenish or green yellow. Chelipeds with pale blue background and large, irregular patches of blue or bluish brown, occupying parts of merus, most of carpus and large areas on mesial face of palm of chela; patches on chela large and typically interconnecting; pollex and dactylus greenish blue proximally, calcified distal portion pale reddish pink; lateral face of chelae with similar but less vivid patches as on mesial face. Second to fifth pereiopods bluish with red chromatophores and bright pink or yellowish articulations. Uropods blue with large pale yellow areas and smaller brown patches. Eggs in ovigerous female pale ultramarine greenish ( Figs. 11–14 View FIGURE 11 View FIGURE 12 View FIGURE 13 View FIGURE 14 ).

Etymology. The name of the new species is the well-known Arabic word shukran , for thanks, expressing the author’s gratitude to colleagues and friends at the King Abdullah University of Science and Technology (KAUST), where this study was finalised; used as a noun in apposition.

Common names. Arabian goby shrimp; Thankful goby shrimp (as for “thankful to have been finally named”).

Type locality. Masirah, Oman.

Distribution. Western Indian Ocean: Oman (Masirah Island and Bandar Khayran area east of Muscat) and Red Sea (central coast of Saudi Arabia, possibly also in Israel and Egypt, see below).

Ecology. Similar to A. djeddensis ; most abundant on shallow sandflats with fine sand and mud bottoms, from the intertidal to at least 5 m in depth; apparently associated with Cryptocentrus cryptocentrus (Valenciennes) ( Fig. 38B View FIGURE 38 ) and possibly C. lutheri ( Karplus et al. 1972a; see also Fig. 14G View FIGURE 14 ); however, both associations require confirmation.

Remarks. No single reliable morphological character separates A. shukran sp. nov. from A. djeddensis , although the presence of two genetically distinct species in the northwestern Indian Ocean is beyond any doubt (see below). In life, these two species are distinguishable by two features of the colour pattern. The first is the colour of the antennular and antennal flagella, which are deep blue in A. djeddensis vs. pale greenish or yellowish in A. shukran sp. nov., and the second is the stylocerite being almost entirely blue in A. djeddensis (except a small patch above the statocyst) vs. having only a blue lateral margin in A. shukran sp. nov. (cf. Figs. 6A View FIGURE 6 , 7 View FIGURE 7 , 8A View FIGURE 8 , 9A, B View FIGURE 9 , 11 View FIGURE 11 , 12A View FIGURE 12 , 13C, G View FIGURE 13 ). Thus, A. djeddensis and A. shukran sp. nov. can be considered as truly cryptic and geminate, or sibling species sensu Knowlton & Mills (1992).

The presence of both cryptic species, i.e., A. djeddensis and A. shukran sp. nov., in the Red Sea obviously complicates the issue of the identity of A. djeddensis sensu Coutière (1897) . Coutière’s type material collected in the 19 th century somewhere near Jeddah is likely too old to be sequenced. The present author’s decision on A. djeddensis and A. shukran sp. nov. was based largely on the relative rarity of the latter species in the shallow waters of Thuwal, which is situated only about 60 km north of Jeddah. However, modern sequencing techniques of old type specimens (see, for example, Bracken-Grissom et al. 2014 and Bracken-Grissom & Felder 2014) should be attempted in the future to confirm or to refute the author’s present species assignments. If Coutière’s lectotype of A. djeddensis (RMNH.CRUS.D.1781) is found to be identical with any of the Red Sea specimens of A. shukran sp. nov., the latter species would need to be synonymised with A. djeddensis , whereas the species herein identified as A. djeddensis would require a new name. It is also noteworthy that the holotype of A. shukran sp. nov. from Oman (FLMNH UF 71923) is genetically distinct from the sequenced Red Sea specimen (RSRC), with the COI sequence divergence between them being 2.8% ( Table 2). The genetic distance between the Red Sea specimens herein identified as A. djeddensis (FLMNH UF 71917, RSRC) and the holotype of A. shukran sp. nov. from Masirah Island (FLMNH UF 71923) is 9.3–9.6% ( Table 2).

Since A. djeddensis and A. shukran sp. nov. have generally very similar colour patterns, except for the colour of the antennular and antennal flagella, and a much subtler difference in the colour of the stylocerite, and may occur syntopically, it is likely that at least some of the records of A. djiboutensis in Karplus et al. (1972al, 1972b, 1974, 1981) may in fact refer to A. shukran sp. nov. A colour slide of a specimen identified as “ A. djiboutensis ” from Eilat, Israel, provided by Dr. I. Karplus ( Fig. 14F View FIGURE 14 ) appears to show A. shukran sp. nov. (with very pale antennal flagella and stylocerite presenting a dark brown-blue lateral band). However, the shrimp in this photograph was possibly kept for some time in an aquarium (see also Fig. 14G View FIGURE 14 ) and may have lost some of its colour. This and some other indirect (photographic) evidence suggests that A. shukran sp. nov. is distributed throughout the Red Sea, including the Gulf of Aqaba (Eilat) and southern Sinai Peninsula (Sharm El-Sheikh).

The holotype of A. shukran sp. nov. ( Figs. 11 View FIGURE 11 , 12 View FIGURE 12 ) is by far the largest specimen in the type series. It is fully grown female with a well-developed balaeniceps condition on the minor chela fingers ( Fig. 12E, F View FIGURE 12 ). In the smaller paratypes, the minor chelae are more slender and the balaeniceps crests are either feebly developed (FLMNH UF 68873) or lacking, possibly due to an early regeneration of the cheliped (FLMNH UF 68870). Therefore, these specimens can be easily confused with A. macellarius , in which the minor cheliped has similar proportions and is lacking balaeniceps setae (see below).