Buergeres, Ng & Manning, 2003

Ahyong, Shane T. & Ng, Peter K. L., 2020, New species of pinnotherid crabs from Southeast Asia and Papua New Guinea (Crustacea: Decapoda: Brachyura), Zootaxa 4816 (3), pp. 333-349 : 341

Buergeres sp.

( Fig. 5 )

Material examined. ZRC 2018.0784 , 1 male (cl 5.3 mm, cw 5.6 mm), Manga Point , Bohol, Visayas, Philippines, 09°42.1’N, 123°51.3’E, 0–1 m, mangrove and mixed intertidal habitat, from Holothuria impatiens , PANGLAO 2004 stn M24, 17 June 2004 .

Description. MALE: Carapace rounded, high, vaulted, slightly wider than long, widest near midlength. Front produced, anterior margin concave in dorsal view. Anterolateral margins poorly defined. Dorsum smooth, glabrous, regions scarcely indicated centrally; dorsal midline convex in profile. Epistome with narrow triangular interantennular septum; median buccal margin with obtuse, triangular median point. Antennular sinus of slightly larger than orbit; antennules folded slightly obliquely. Antennal articles 1 and 2 fused to epistome. Eyes visible in dorsal view, filling orbit, cornea pigmented.

Maxilliped 3 ischiomerus length twice width; inner proximal margin convex; inner margin with blunt, obtuse angle slightly distal to midlength, margin on either side weakly concave; outer margin strongly convex. Carpus half propodus length. Propodus spatulate, gently tapering in distal half, apex rounded, dorsally and distally setose, length exceeding twice dactylus length. Dactylus sub-clavate, widest distal to midlength, apex rounded, distally setose, inserted at propodal midlength, apex not reaching end of propodus. Exopod inner margin straight, outer margin convex; flagellum with 2 articles, distally setose.

Chelipeds symmetrical from left to right. Dactylus and pollex relatively straight, crossing distally, without gape. Dactylus dorsal margin convex, smooth, glabrous; occlusal margin with blunt triangular tooth proximal to midlength, otherwise straight, sparsely setose. Pollex occlusal margin with 2 blunt triangular teeth proximally, remaining margin weakly crenulate, straight, sparsely setose, minutely denticulate; with fringe of setae on inner ventral margin extending onto lower inner palm surface. Propodus palm outer surface smooth, glabrous; dorsal margin 1.3× height, 1.1× length of dactylus; ventral margin sinuous. Carpus unarmed, inner margin setose.

Pereopods 2–5 (walking legs 1–4) symmetrical from left to right, unarmed; relative lengths in decreasing order: P3 = P4> P2> P5. P3 merus length 0.5× pcl. P2–4 similar; merus extensor margin broadly convex, extensor and flexor margins sparsely setose; carpus glabrous; dactylus and propodus flexor margins setose; dactyli subequal, stout, falcate, evenly arcuate, distally spiniform, length 0.4× propodus length; basis anterior surface smooth, not granulate. P5 merus tapering distally, distinctly shorter than P2–4 merus, extensor and flexor margins margins straight; propodus margins parallel, flexor margin setose; dactylus slender, weakly curved, almost straight, flexor margin setose but unarmed, 0.8× propodus length, 1.3× P2–4 dactylus length.

Thoracic sternum anterior margin concave medially; sternites 1–3 indistinguishably fused; sterno-pleonal cavity reaching level of sternite 3/4 suture.

Pleon slender, margins evenly converging distally; comprising 6 free somites and telson, widest at somites 1–3; telson as wide as long, apex rounded.

Gonopod 1 elongate, slender, gently arcuate, dorsoventrally compressed, about ¾ length of pleon, tapering to convex apex with short, obliquely directed spiniform tip; margins strongly setose. Gonopod 2 endopod simple, about ¼ length of gonopod 1; exopod short, slender, about half length of endopod. Pleopods 3–5 absent.

Host. Holothuria impatiens (Forskål, 1775) (Holothuriidae) .

Remarks. Prior to the present study, knowledge of male Buergeres has been derived from a single specimen of B. deccanensis reported by Chopra (1931) (although without figures or description of the gonopods). We report here a male of an unidentified species of Buergeres from the Philippines ( Fig. 5 ). It corresponds well to Buergeres in maxilliped 3 morphology and in the subequal P2–4 dactyli that are all shorter and more strongly curved than the straight, elongate P5 dactylus. Based on what is known of B. deccanensis , the P5 dactylus is essentially straight in both sexes, but proportionally shorter in males; the present male reflects such a condition. The Philippine male differs from male B. deccanensis in carapace shape (rounded versus subquadrate), and given the locality, might be referable to either B. holothuriae or B. ortmanni , both of which occur in the Philippines ( Bürger 1895; Ng & Man- ning 2003). The specific identity of the male cannot be confirmed at present because it was not associated with a known female, but we believe that it is probably B. ortmanni : the outer surface of the cheliped palm is glabrous as in female B. ortmanni ( Fig. 5D ; Ng & Manning 2003: fig. 4C), rather than tomentose as in female B. holothuriae ( Ng & Manning 2003: fig. 5D). Despite the unconfirmed identification, the present male is figured here to document its morphology, especially that of the gonopods. As in known males of Holotheres (see Ng & Manning 2003: fig. 1I, 2H), the G1 of the present male is broadly curved, with a short, slender, obliquely directed apex (albeit proportionally shorter than in Holotheres ) ( Fig. 5L ). As in many other pinnotherids, the G2 of the male Buergeres has a short but distinct exopod ( Fig. 5M, N ; Ahyong et al. 2012; Ng & Ho 2016a; Ng 2018b; Ahyong 2019).

Figures

FIGURE 5. Buergeres sp., male, cl 5.3 mm, cw 5.6 mm, Manga Point, Bohol, Visayas, Philippines, ZRC 2018.0784:A, dorsal habitus; B, anterior cephalothorax; C, right maxilliped 3; D, right chela; E–H, right P2–5; I, anterior thoracic sternum; J, pleon; K–L, left G1, sternal and pleonal views, respectively; M–N, left G2, sternal and pleonal views, respectively. Scales:A = 2.0 mm; B, D–H, J = 1.0 mm; C, K–N = 0.5 mm.