Alpheus pseudopugnax (Banner, 1953)

Anker, Arthur, 2013, Notes on two rare and little-known Indo-Pacific snapping shrimps, Alpheus percyi Coutière, 1908 and A. pseudopugnax (Banner, 1953) (Decapoda, Alpheidae), Zootaxa 3722 (2), pp. 267-282 : 275-281

Alpheus pseudopugnax (Banner, 1953)

( Figs. 6–10 , 11 E–G)

Crangon pseudopugnax Banner 1953: 122 , fig. 44.

Alpheus pseudopugnax — De Grave & Fransen 2011: 388.

Material examined. 1 female, holotype (cl 4.6 mm), USNM 93513, Hawaiian Islands, Maui, southeast Maalaea Bay, Kalama Park, old coral, ~ 2.7 m; 1 ovig. female (cl 6.8 mm), UF 12880, Mascarene Islands, Reunion Island ( La Réunion), Saint-Leu, Sec Jaune, -21.1533° -55.2811°, rocky slope, basalt blocks, fore reef, depth 6–15 m, rubble extraction, leg. H. Bruggemann, N. Hubert, F. Michonneau, G. Paulay, 17 Aug 2007 [fcn BREU-1359]; 1 male (cl 6.5 mm), UF 12873, Mascarene Islands, Reunion Island ( La Réunion), Saint-Leu, Sec Jaune, -21.1533° -55.2811°, rocky slope, basalt blocks, fore reef, depth 6–15 m, rubble extraction, leg. H. Bruggemann, N. Hubert, F. Michonneau, G. Paulay, 17 Aug 2007 [fcn BREU-1350]; 1 female (cl 4.6 mm), UF 15443, French Polynesia, Society Islands, Moorea, of northern coast between Pihaena and Opunohu Bay, outer reef slope, depth ~ 12 m, rubble cracking, leg. S. McKeon, J. Moore, G. Paulay, 12 Oct 2008 [fcn BMOO-2258]; 1 ovig. female (cl 6.8 mm), UF 28992, French Polynesia, Society Islands, Moorea, south end of island, -17.60085° -149.84128°, reef flat, depth 20 m, leg. D. Uyeno, 17 Nov 2010 [fcn BMOO-15118]; 1 male (cl 6.2 mm), 1 ov. female (cl 6.3 mm), UF 10622, Kiribati, Line Islands, Palmyra Atoll, north side of atoll, 5.8958° -162.0815°, outer reef slope, in dead Pocillopora head, depth ~ 11 m, leg. G. Paulay and N. Knowlton, 19 Aug 2005 [fcn BPALM-956, -957].

Description. Small-sized species of Alpheus (cl range 4.8–6.8 mm). Carapace with small post-rostral tubercle on mid-dorsal line, at about 0.25 carapace length, separating more or less descendant frontal area from horizontal or slightly domed posterior area; post-rostral tubercle continued by low, sometimes barely discernable, mid-dorsal crest flattening completely before reaching posterior margin of carapace ( Figs. 6 A, B, 8A, B). Rostrum welldeveloped, abruptly rising above deep orbito-rostral furrows, anterior portion narrow, carina-like, not overhanging orbito-rostral furrows, posterior portion flattened, broadening, overhanging orbito-rostral furrows; faint median carina running from rostral tip to post-rostral tubercle (better developed in younger individuals); rostral tip almost reaching distal margin of first article of antennular peduncle, pointing straight-foward or slightly descendant ( Figs. 6 A, B, 8A, B). Orbital hoods unarmed, rounded anteriorly ( Figs. 6 A, 8A). Pterygostomial angle broadly rounded ( Figs. 6 B, 8B). Telson moderately broad, tapering distally; dorsal spiniform setae stout, inserted at some distance from lateral margins; posterior margin broadly rounded, with two pairs of distolateral spiniform setae, mesial much longer than lateral, and row of smaller spiniform setae ( Figs. 6 J, K, 8J, K). Antennular peduncle with slender stylocerite, its acute tip overreaching distal margin of first article; second article about 1.3-1.5 times as long as wide ( Figs. 6 A, 8A). Antenna with stout basicerite armed with strong, sharp distoventral tooth; carpocerite not exceeding scaphocerite; scaphocerite with broadly concave lateral margin, strong distolateral tooth overreaching end of antennular peduncle, blade moderately broad ( Figs. 6 A-C, 8A, B). Third maxilliped with antepenultimate article not expanded; penultimate article at least 2.5 times as long as wide ( Figs. 6 D, E, 8C). Minor cheliped significantly smaller and more slender than major cheliped; merus with dorsal margin ending in stout distodorsal tooth, mesial margin armed with one or several spiniform seta and ending in small, sharp distomesial tooth; carpus cup-shaped; chela with palm subcylindrical, rounded in cross-section, smooth, distomesial and distolateral areas on each side of dactylar articulation blunt; fingers slightly shorter than palm, conical, non-gaping, dactylus without balaeniceps setae in both sexes ( Figs. 7 A, B, 9A, B). Major cheliped with short, stout merus; dorsal margin of merus slightly rugose, ending in strong, curved distodorsal tooth; mesial margin of merus rugose, with widely spaced, stout spiniform setae, ending in strong, sharp distomesial tooth; carpus very short, bowl-shaped; chela with palm ovoid, rounded in cross-section, smooth except for deep transverse groove on distodorsal surface and shallow longitudinal depression on distolateral surface, adjacent to transverse groove; fingers less than half-length of palm, dactylus with short, truncate plunger ( Figs. 7 C-G, 9C-F). Second pereiopod with first carpal article 1.0-1.3 times as long as second ( Figs. 6 F, 8D). Third and fourth pereiopods similar, slender; ischium with spiniform seta; merus ~5.0 times as long as wide, with stout, sharp distoventral tooth; carpus with sharp distoventral tooth; propodus with row of slender spiniform setae on ventral margin (some inserted in pairs), as well as one pair of distoventral and one distodorsal spiniform setae; dactylus simple, conical, slightly curving, about 0.3 length of propodus ( Figs. 6 G, 8E). Fifth pereiopod more slender than third and fourth pereiopods; ischium with small spiniform seta; propodus with row of slender spiniform setae on ventral margin, cleaning brush poorly developed. Male second pleopod with appendix masculina reaching far beyond appendix interna ( Fig. 8 G). Uropod with exopod slightly longer than endopod; protopod with lateral lobe ending in strong, sharp tooth; exopod with diaeresis sinuous, ending in strong sublateral tooth, distolateral tooth strong; distolateral spiniform seta long, slender; endopod with row of slender spiniform setae on distal margin ( Figs. 6 H, I, 8H, I). See also description and illustrations in Banner (1953).

Colour pattern. Two colour pattern types differing mainly in the dorsal colour of the fifth abdominal somite. Type A ( Fig. 10 A–C): body with semitransparent-white background and broad, wine-red transverse bands arranged as following, from anterior to posterior: first band crossing anterior margin of carapace, encompassing rostroorbital area; second band crossing carapace at about mid-length; third band crossing first and second abdominal somites, tangentially touching posterior margin of carapace; fourth band crossing posterior third of third and most of fourth abdominal somites; fifth band occupying most of sixth abdominal somite; fifth abdominal somite mostly white except for deep-red ventral portions of pleura; antennular and antennal peduncles dark red with some whitish areas, flagella pale reddish; minor chela dark red; major chela mostly white, with some red-orange on mesialproximal portion of palm; dactylus orange-brown with hyaline-white tip; second pereiopods and walking legs dark red; pleopod with whitish protopods, exopods and endopods red; tail fan dark red distally, mainly white proximally. Type B ( Fig. 10 D–F): generally similar to type A, but first and second bands of carapace with respectively posterior and anterior margins more irregular, white band between them narrower, more crescent-shape; major chela sometimes with orange rash spots on mesial face of palm; posterior white band on carapace sometimes with yellow-orange spots dorsally; fourth band of abdomen crossing posterior third of third, fourth and anterior half of fifth abdominal somites, leaving either a narrow transverse white band ( Fig. 10 D–F) or a more irregular, U-shaped band ( Fig. 10 G, H) on fifth somite. Fresh eggs dark red ( Fig. 10 H).

Distribution. Indo-West Pacific from southwestern Indian Ocean to Hawaii and French Polynesia. Indian Ocean: Reunion Island (present study). Pacific Ocean: Maui and Oahu, Hawaiian Islands (Banner, 1953); Palmyra Atoll, Line Islands; Moorea, Society Islands (present study).

Ecology. Coral reef and associated habitats, in dead coral heads, in crevices of coral rubble; depth range: 2–20 m [e.g., 2–6 m (Hawaii), 11 m (Palmyra), 12–20 m (Moorea), 6–15 m ( Reunion)].

Remarks. The specimens from Moorea, Palmyra Atoll and Reunion represent the first records of A. pseudopugnax since the original description of the species from Hawaii. The new records significantly extend the range of A. pseudopugnax from north-central Pacific Ocean (Hawaii) to south-central and western Pacific Ocean ( French Polynesia and Kiribati) and south-western Indian Ocean (Mascarene Islands). Thus, A. pseudopugnax , like its relative A. percyi , appears to be widely distributed in the Indo-West and Central Pacific. However, both species are relatively uncommon and appear to be more common around oceanic or offshore islands with healthy coral reef stands and biologically rich coral rubble.

Banner (1953) listed three morphological differences between A. pseudopugnax and A. percyi , involving the orbito-rostral region and major and minor chelipeds. In A. pseudopugnax , the rostral carina is not flattened posterior to the rostral tip, running as a flattened ridge, before broadening, becoming more abrupt and overhanging the orbito-rostral grooves between or posterior to the eyes; in addition, a faint median carina is noticeable in the flattened portion of the post-rostral plate ( Figs. 6 A, 8A). In A. percyi , the rostral carina flattens close to the tip of the rostrum, forming a narrowly triangular post-rostral plate without a trace of a median carina ( Figs. 1 A, 3A). The major chela of A. pseudopugnax has a slight longitudinal depression on the lateral face of the palm, adjacent to the deep transverse groove ( Figs. 7 F, 9E); such a depression is not discernable on the palm of A. percyi ( Figs. 2 F, 4E). The palm of the minor chela of A. pseudopugnax does not have strong, sharp distolateral and distomesial teeth characteristic of A. percyi (compare Figs. 2 A, B and 9A, B). One additional differentiating character not mentioned by Banner (1953) is the presence of balaeniceps setae on the male minor chela in A. percyi ( Fig. 2 B; see also Coutière 1921, fig. 22b) and their absence in A. pseudopugnax ( Fig. 9 B).

Interestingly, A. pseudopugnax appears to display two types of colour pattern, one with the fifth somite white dorsally (type A) and one with the fifth somite dark red dorsally (type B). Type A pattern is displayed by the smaller Moorea specimen and one of the Reunion specimens ( Fig. 10 A–C), whereas type B pattern is present in the Palmyra specimens and the second Reunion specimen ( Fig. 10 D–F). However, the larger Moorea specimen displays a colour pattern that is intermediate between type A and type B ( Fig. 10 G, H), suggesting that these patterns are not consistent and may vary individually and/or with sex or age. Both colour pattern types agree with Banner’s (1953) short description of the pattern of A. pseudopugnax : “in life, type specimen with broad, red, transverse bands”. A side-by-side morphological comparison between the specimens of type A and B revealed some differences, for instance, in the post-rostral region (which is generally quite variable), but also in the length of the second article of the antennular peduncle (cf. Figs. 6 A, 8A) and the proportions of the second pereiopod ( Figs. 6 G, 8E), which appears to be more slender in the type B specimen from Reunion than in the type A specimen from Moorea. However, a preliminary sequencing of the barcoding segment of the COI gene (C. Hurt, pers. comm.) revealed only a very insignificant difference between the smaller Moorea specimen (type A) and the Palmyra specimen (type B).

A remarkable and unusual feature of the colour pattern of A. pseudopugnax is the colour contrast between the major and minor cheliped. The major chela is conspicuously white, only with brown-red base and occasionally with orange, rash-like pattern, whilst the minor chela is dark red ( Fig. 10 A–F). Because of this disparate colouration of the chelipeds and the presence of broad red bands on the carapace and abdomen, the colour pattern of A. pseudopugnax greatly differs from that of A. percyi , which shows more resemblance to some species of the A. gracilipes species complex (see above). A strikingly dissimilar colouration of the chelipeds is rare in alpheid shrimps and decapods in general, although it is a common character of many fiddler crabs ( Uca spp.) and also occurs in some hermit crabs, e.g., Pylopaguropsis lemaitrei Asakura & Paulay, 2003 .

Figures

FIGURE 1. Alpheus percyi Coutière, 1908, male from French Frigate Shoals, Hawaiian Archipelago (UF 12372): A—frontal region, dorsal view; B—same, lateral view; C—second pereiopod, lateral view; D—third pereiopod, lateral view; E—same, distal carpus, propodus and dactylus, lateral view; F—second pleopod, appendices masculina and interna, mesial view; Guropod, dorsal view; H—same, spiniform setae on distal margin of endopod, dorsal view; I—telson, dorsal view; J—same, posterior margin, dorsal view.

FIGURE 2. Alpheus percyi Coutière, 1908, male from French Frigate Shoals, Hawaiian Archipelago (UF 12372): A—minor cheliped, lateral view; B—same, carpus and chela, mesial view; C—same, ischium, merus and carpus, mesial view; D—major cheliped, lateral view; E—major chela, mesial view; F—major chela, lateral view.

FIGURE 6. Alpheus pseudopugnax (Banner, 1953), female from Moorea, French Polynesia, UF 15443: A—frontal region, dorsal view; B—same, lateral view; C—antennal scaphocerite, dorsal view; D—third maxilliped, lateral view; E—same, lateral plate and mastigobranch, lateral view; F—second pereiopod, lateral view; G—third pereiopod, lateral view; H—uropod, dorsal view; I—same, spiniform setae on distal margin of endopod, dorsal view; J—telson, dorsal view; K—same, posterior margin, dorsal view.

FIGURE 7. Alpheus pseudopugnax (Banner, 1953), female from Moorea, French Polynesia, UF 15443: A—minor cheliped, lateral view; B—same, distal carpus and chela, mesial view; C—major cheliped, lateral view; D—same, basis, ischium, merus and carpus, mesial view; E—major chela, mesial view; F—major chela, lateral view; G—distal major chela, fingers opened, lateral view.

FIGURE 8. Alpheus pseudopugnax (Banner, 1953), male from Reunion Island (La Réunion), UF 12873: A—frontal region, dorsal view; B—same, lateral view; C—third maxilliped, lateral view; D—second pereiopod, lateral view; E—third pereiopod, lateral view; F—same, distal carpus, propodus and dactylus, lateral view; G—second pleopod, appendices masculina and interna, mesial view; H—uropod, dorsal view; I—same, spiniform setae on distal margin of endopod, dorsal view; J—telson, dorsal view; K—same, posterior margin, dorsal view.

FIGURE 9. Alpheus pseudopugnax (Banner, 1953), male from Reunion Island (La Réunion), UF 12873: A—minor cheliped, lateral view; B—same, carpus and chela, mesial view; C—major cheliped, ischium, merus and carpus, mesial view; D – major chela, mesial view; E—major chela, lateral view; F—distal major chela, fingers opened, lateral view.

FIGURE 10. Alpheus pseudopugnax (Banner, 1953): A, B—ovigerous female from Reunion Island (La Réunion), UF 12880 [type A colour pattern]; C—female from Moorea, French Polynesia, UF 15443 [type A colour pattern]; D, E—male from Palmyra Atoll, Line Islands, UF 10622 [type B colour pattern]; F—male from Reunion Island (La Réunion), UF 12873 [type B colour pattern]; G, H—ovigerous female (missing major cheliped) from Moorea, French Polynesia, UF 28992 [intermediate A- B colour pattern]. Photographers: Gustav Paulay (A, B, D, E, F); Arthur Anker (C, G, H).

FIGURE 11. Variation in the shape of the postrostral region in Alpheus percyi Coutière, 1908 (A – D) and Alpheus pseudopugnax (Banner, 1953) (E – G): A—holotype female from Amirante, MNHN 3188; B—female from Tabuaeran, Line Islands, UF 10662; C—male from Oahu, Hawaiian Archipelago, UF 15237; D—non-type male of Alpheus percyi (?) from Amirante, MNHN 3486; E—holotype female from Maui, Hawaiian Archipelago, USNM 93513; F—ovigerous female from Reunion Island (La Réunion), UF 12880; G—female from Palmyra Atoll, Line Islands, UF 10622.