Alpheus lutosus spec. nov.
Figs 1-5. Alpheus lutosus spec. nov., male paratype (OUMNH.ZC.2007-17-002). 1, frontal region, lateral; 2, same, dorsal; 3, major (right) cheliped, lateral; 4, same, mesial; 5, same, dactylus showing plunger, lateral.
Material examined.— Holotype, ♂ (RMNH D 53106), Kuwait, Shatt-Al-Arab delta, Bubiyan Island, Ras Al-Barshah and area bordering Khor Al-Subbiya, approx. 29°36’N 48°188’E, muddy intertidal, in burrows with gobies, leg. D. Jones et al., 01.x.2004, CL 8.6 mm. Paratypes: ♀ (RMNH D 53107), CL 8.4 mm; ♂ (CL 6.4 mm), 3 ♀♀ (CL 7.1-8.5 mm) (OUMNH.ZC.2007-17-001); ♂ (OUMNH.ZC.2007-17-002), dissected and illustrated, CL 10.0 mm; all same data as holotype. Non-type material examined: 1 ♂ (CL 9.0 mm), 3 ♀♀ (CL 6.0-8.7 mm) (FLMNH UF Arthropoda 3872), Kuwait, Kuwait Bay, Al Jahrah, mudflat, coll. Vaughan, ZZZ-89003, 01.ii.1978.
Description.— Medium-sized species of Alpheus edwardsii group. Rostrum conical, acute distally, not flattened dorsally; rostral carina feebly developed, flattening posteriorly (fig. 2), reaching 0.23-0.38 CL; orbital hoods moderately swollen, rounded, unarmed; adrostral furrows shallow. Antennular peduncle with second segment more than twice as long as wide; stylocerite not reaching distal margin of first segment (fig. 2); mesioventral carina with low, shark fin shaped tooth (fig. 16). Antenna with basicerite bearing small, subacute (sometimes blunt) distoventral tooth (fig. 1); scaphocerite relatively long, with slightly concave lateral margin and narrow blade, latter not overreaching strong distolateral tooth (fig. 2); carpocerite reaching beyond scaphocerite and end of antennular peduncle (fig. 1).
Mouthparts typical for Alpheus in external observation. Third maxilliped slender, pediform; antepenultimate segment flattened ventrolaterally; proportions of antepenultimate, penultimate and ultimate segments as illustrated (fig. 15); lateral plate on coxa protruding, blunt distally; arthrobranch well developed.
Major cheliped similar in both sexes, although larger and with slightly different proportions in males; ischium very short, merus short, stout, blunt distodorsally, without distinct distomesial tooth; carpus broadly cup-shaped; chela with palm roughly twice as long as fingers, distodorsal margin with broad notch extending on lateral surface as broad, posteriorly extending longitudinal depression (fig. 3), and on mesial surface as posteriorly extending longitudinal groove (fig. 4), dorsal shoulder not overhanging, rounded, sloping smoothly into notch (fig. 4); ventral margin with deep, broad notch, adjacent areas depressed on both mesial and lateral surface (figs 3-4), ventral shoulder not protruding anteriorly, rounded; distal margin of palm with sharp tooth mesially, without such tooth laterally (figs 3-4); dactylus only slightly overreaching pollex (fig. 3), with well developed plunger, latter furnished with stamen-shaped sensillae (fig. 5).
Male minor cheliped with short ischium, stout merus and cup-shaped carpus, proportions as illustrated (figs 6, 8); chela with palm approximately 1.2-1.3 times longer than fingers; distodorsal margin with distinct depression extending on lateral surface as shallow, posteriorly extending longitudinal groove (figs 6, 9), and on mesial surface as short, not posteriorly extending transverse groove (fig. 7); ventral margin with distinct notch visible in both lateral and mesial views (figs 6-7, 9); distal margin of palm with small acute tooth both laterally and mesially (figs 7, 9); dactylus markedly expanded, with lateral and mesial ridges furnished with balaeniceps setae (figs 6-7, 9); pollex with row of setae proximally on mesial side, without organised setae laterally (figs 6-7). Female minor cheliped with ischium, merus and carpus similar to those in male; chela with fingers non-balaeniceps, moderately slender, about as long as palm; palm with shallow depression dorsolaterally, ventral margin without sinus.
Second pereiopod slender; merus slightly shorter than ischium; carpus five-segmented, ratio of segments approximately 4/2.5/1/1/1.5; chela as long as second carpal segment (fig. 10). Third pereiopod relatively slender; ischium with small ventrolateral spine (fig. 11); merus about 4.5 times as long as wide; carpus slightly less than half length of merus, without spines; propodus significantly longer than carpus but much shorter than merus, ventral margin with 3-4 spines, dorsolateral margin with row of elongate setae (fig. 12); dactylus about half propodus length, subspatulate (fig. 12). Fourth pereiopod generally similar to third. Fifth pereiopod small, slender; ischium unarmed (fig. 13); carpus 0.75 length of merus; propodus with dense setal brush (fig. 13), without spines.
First pleopod with relatively small endopod (especially in males). Second pleopod with appendices masculina and interna in males (fig. 14). Uropod with lateral lobe of protopod ending in acute point; exopod and endopod broad, rounded; diaeresis of exopod almost straight, lateral portion with small, broadly subtriangular lobe adjacent to slender distolateral spine (fig. 17). Telson broad, almost rectangular (only slightly tapering posteriorly), dorsal spines well developed, situated centrally, i.e. at some distance from lateral margins (fig. 18), first pair more or less at telson mid-length or slightly in front, second pair at 0.75 telson length (right posterior spine missing in illustrated specimen, cf. fig. 18); posterior margin broadly rounded, each posterolateral angle with two spines: one minuscule lateral spine and one stronger and longer mesial spine, latter still significantly smaller than dorsal spines of telson (fig. 18).
Size.— Medium-size species of Alpheus: CL of males ranging from 6.0 mm to 10.0 mm, CL of females ranging from 7.0 to 8.7 mm; TL of largest specimens approaching 40 mm.
Colour.— Carapace and abdomen pale olive-greenish, semitransparent; major and minor chelae pale yellow-greenish, much darker distally (fingers of major chela dark olive-green); walking legs semitransparent straw-yellowish; uropods with patch of intense blue chromatophores across posterior half (based on colour photograph provided by J. Gardiner).
Etymology.— The specific name lutosus (Latin adjective for “muddy” or “in mud”) refers to the preference of this species for muddy habitats.
Ecology.— Alpheus lutosus spec. nov. is relatively common in the intertidal and estuarine mudflats of the Shatt-Al-Arab delta, in burrows made under stones or in muddy banks, sometimes associated with the goby Acentrogobius dayi Koumans, 1944 (identified by R. Winterbottom, ROM). Most likely, Acentrogobius dayi does not establish body contact with the snapping shrimp and belongs to the category of so-called “facultative” shrimp gobies (see Karplus, 1992). Two other species of Alpheus have been observed syntopically at the type locality: A. cf. lobidens De Haan, 1849 and A. cf. rapax Fabricius, 1798 (D. T. Jones, pers. comm.).
Distribution.— Presently known only from Kuwait: Bubiyan Island, southwest of Shatt-Al-Arab delta, and Al Jahrah in Kuwait Bay (west of Kuwait City); most likely also occurring in the Iraqi and Iranian side of the Shatt-Al-Arab delta.
Remarks.— Alpheus lutosus spec. nov. is assumed to be closely related to A. hoplocheles from China and Japan (Coutière, 1897; Miya, 1995; Liu & He, 2007). These two species differ from all other species of the A. edwardsii group by the presence of a sharp distal tooth on the mesial side of the otherwise typical edwardsii-type major chela. They also have many other features in common, such as the subspatulate dactyli on the third to fifth pereiopods; the well developed, posteriorly non-flattened rostrum, the ischium of the third and fourth pereiopods bearing a small spine; as well as the well developed balaeniceps condition of the male minor chela. However, A. hoplocheles may be distinguished from A. lutosus spec. nov. by the presence of a strong, protruding and sharp distal tooth also on the lateral side of the palm of the major chela (Miya, 1995; see also Liu & He, 2007); in A. lutosus spec. nov., this tooth is not protruding and rounded (cf. fig. 3). Furthermore, in A. hoplocheles, the major chela has a more protruding ventral shoulder, with a more pronounced, narrower groove on the lateral side of the palm; similarly, the dorsal shoulder is sharper and more overhanging (compare Miya, 1995 and figs. 3-4). Another important distinguishing feature is the ventral armature of the propodus of the third and fourth pereiopods: in A. hoplocheles, the propodus is armed with nine spines (including the distoventral spine) vs. only three or four spines in A. lutosus spec. nov. In addition, in A. hoplocheles, the rostrum appears to be slightly longer, just falling short of the first segment of the antennular peduncle; the stylocerite is also longer; the lateral margin of the scaphocerite is somewhat more concave; the rostral carina is better marked, extending to about 0.7 CL (vs. 0.23-0.38 CL in A. lutosus spec. nov.); the proportion palm/fingers of the major claw is approximately 1.3/1 (vs. 1.7/1 in A. lutosus spec. nov.); the proportion palm/fingers of the female minor chela (based on female lectotype) is close to 1/1.3 (vs. close to 1/1 in A. lutosus spec. nov.); the ratio of carpal segments in the second pereiopod is approximately 3/2.5/1/1/1.4 (vs. 4/2.5/1/1/1.5 in A. lutosus spec. nov.); and the proportion propodus/dactylus of the third pereiopod is approximately 2.4/1 (vs. ~2/1 in A. lutosus spec. nov.). Finally, the two species appear to be geographically widely separated, A. hoplocheles occurring from central Japan to southern China, whilst A. lutosus spec. nov. is presently known only from the western Persian Gulf.