Comprehensive Description

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Body stout, laterally not compressed. Carapace glabrous; frontal margin with well-developed rostrum and orbital teeth; rostrum slightly flattened dorsally, tapering distally, with acute tip, much longer than wide; lateral margins without setae; tip reaching half-length of first article of antennular peduncle; rostral carina not distinct; orbital teeth in marginal position, relatively small, acute distally, shorter than rostrum (note: right orbital hood atypical, i.e. without tooth in male); margin between orbital teeth and rostrum broadly V-shaped; orbital hoods moderately swollen, enclosing eyes from all sides (Fig. 1A, B); rostro-orbital process present. Pterygostomial angle rounded, not protruding anteriorly (Fig. 1B); cardiac notch deep. Abdominal somites with posteroventral margins broadly rounded, fifth slightly more angular; sixth somite without articulated flap, bluntly projecting posteriorly.  Eyes with well-developed corneas; anteromesial margin bluntly protruding. Ocellar beak projecting, acute, visible in lateral view. Epistomial sclerites not acutely projecting.  Antennule with moderately slender peduncle; stylocerite not reaching distal margin of first article, with acute tip; ventromesial carina with large, subtriangular tooth as illustrated (Fig. 1C); second article much longer than dorsally visible portion of first article, about 2.5 times as long as wide (Fig. 1A); lateral flagellum with groups of aesthetascs starting from 12th article. Antenna with basicerite terminating in sharp distoventral tooth; carpocerite slightly exceeding both scaphocerite and antennular peduncle; scaphocerite with shallowly concave lateral margin and large, stout distolateral tooth, latter reaching far beyond distal margin of blade (Fig. 1A).  Mouthparts (not dissected) not specific in external view. Third maxilliped rather slender; coxa with lateral plate somewhat truncate distally; exopod long, overreaching distal margin of antepenultimate article; antepenultimate article somewhat flattened, ventral margin densely setose; penultimate article no more than three times as long as greatest width, distally slightly widening, very setose; ultimate article slender, tapering distally, with rows of serrulate setae and long, simple setae, tip unarmed (Fig. 1D).  Male minor cheliped with short, stout ischium; merus broad, subtriangular in cross-section; ventrolateral margin smooth; ventromesial margin straight, ending in small, acute distomesial tooth, and with four minute spiniform setae roughly equidistantly spaced along 0.6–0.7 of merus margin, and with tips falling just short of margin (therefore invisible in lateral view); distodorsal angle blunt; carpus rounded, cup-shaped; chela strongly compressed, with palm sculptured distally; lateral surface with low crest starting at about mid-length of palm and ending in a sharp distolateral tooth; ventral margin with blunt, non-protruding shoulder and adjacent deep notch, latter continuing transversely forming a shallow depression on mesial surface; dorsal margin with subcylindrical elevation ending distally in small adhesive disk; distomesial surface with crest ending in stout sharp tooth; fingers as long as palm; pollex shallowly excavated on cutting edge; dactylus somewhat flattened and twisted laterally, slightly convex dorsally, proximally with small adhesive disk (Fig. 2A–C). Female minor cheliped unknown (missing in the paratype).  Male major cheliped with short, stout ischium, ventromesial surface with small spiniform seta; merus stout, short, broad, subtriangular in cross-section; ventrolateral margin smooth; ventromesial margin straight, ending in stout, sharp distomesial tooth, and with small, widely spaced spiniform setae; dorsal margin ending bluntly distally; carpus very short, cup-shaped; chela somewhat compressed; palm strongly sculptured; lateral surface with low crest starting at about 0.6 length of palm and ending in sharp distolateral tooth; ventral margin with rounded, smooth, non-projecting shoulder adjacent to deep notch, latter continuing transversely to shallow groove on mesial surface; dorsal margin with subcylindrical elevation ending in large adhesive disk distally; distomesial surface with transversally deeply notched crest ending in sharp tooth; pollex shorter than dactylus, somewhat twisted and shallowly depressed laterally, cutting edge bluntly projecting laterally; dactylus flattened, twisted laterally, convex dorsally, bulbous distally, plunger reduced to broad, low tooth (Fig. 2D–F). Female major cheliped generally similar in shape and proportions to male major cheliped.  Second pereiopod elongate, slender; ischium slightly longer than merus; carpus with five articles with ratio approximately equal to 4 : 2 : 1 : 1.5 : 2; chela simple, fingers with scarce tufts of setae (Fig. 1E). Third and fourth pereiopods generally similar, moderately slender; third pereiopod with ischium armed with spiniform seta on ventrolateral surface; merus about five times as long as wide, without distoventral tooth; carpus more slender and about half as long as merus; propodus longer than carpus, with eight or so robust spiniform setae along ventral margin and one pair of longer spiniform setae adjacent to dactylus; dactylus about 0.4 length of propodus, simple, conical, faintly curved, with acute tip (Fig. 1F). Fifth pereiopod much more slender than third and fourth pereiopods; merus only slightly longer than carpus; ischium with spiniform seta; propodus with some spiniform setae along ventral margin and well-developed setal brush distolaterally (Fig. 1G).  Pleopods with protopods furnished with spiniform setae on lateral margin, some inserted in pairs (Fig. 1H, J, K), first pleopod with small endopod furnished with setae, male second pleopod with appendix masculina subequal in length to appendix interna, not reaching distal margin of endopod, furnished with numerous stiff setae (Fig. 1I); female second pleopod with appendix interna only. Uropod with lateral lobe of protopod ending in large, acute tooth; diaeresis sinuous, with blunt tooth adjacent to one (occasionally two) stout distolateral spiniform seta(e); endopod with row of small spiniform setae along distolateral margin (Fig. 1L).  Telson subrectangular, tapering towards posterior margin, about twice as long as wide at base; lateral margins slightly convex; dorsal surface with two pairs of strong spiniform setae inserted at some distance from lateral margin, first pair anterior to telson mid-length, second pair at about 0.7 telson length; posterior margin about 0.6 length of anterior margin, broadly convex, with two pairs of posterolateral spiniform setae, mesial about twice as long as lateral (Fig. 1M); anal tubercles well developed.  Gill–exopod formula typical for Alpheus: five pleurobranchs (above P1–5), one arthrobranch (Mxp3), two lobe-shaped epipods (Mxp1–2), five mastigobranchs (Mxp3, P1–4), five setobranchs (P1–5); three exopods (Mxp1–3).


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© Arthur Anker, Sammy De Grave

Source: ZooKeys

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