Synalpheus brevidactylus, Anker, Arthur & Tóth, Eva, 2008

Anker, Arthur & Tóth, Eva, 2008, A preliminary revision of the Synalpheus paraneptunus Coutière, 1909 species complex (Crustacea: Decapoda: Alpheidae), Zootaxa 1915, pp. 1-28 : 14-16

Synalpheus brevidactylus n. sp.

( Figs. 8 , 9 , 14 C, D)

Not Synalpheus brevidactylus – Cubit & Williams 1983: 24 [lap. cal. for S. brevicarpus (Herrick, 1891) ]

Type material. Panama, Caribbean coast. Holotype, breeding female, USNM 1116683, Isla Grande, between village and west point, in cryptic sponge among coral rubble, depth 1– 3 m. coll. E. Tóth, 16 Nov 2006 [06- 740a]. Paratypes: 1 breeding female, USNM 1116684, Isla Grande, between village and west point, in cryptic sponge among coral rubble, depth 1–3 m, coll. E. Tóth, 8 Feb 2007 [07-024a, photo voucher, specimen dissected]; 1 male, USNM 1116685, same collection data as for previous paratype [07-024b, photo voucher]; 1 breeding female, 1 male, UP, La Guaira (facing Isla Grande), in coral rocks, in cryptic sponge, depth 1–2 m, coll. A. Anker and A. Baeza, 4 Aug 2007 [07-217, photo voucher].

Additional material. Panama, Caribbean coast. 1 breeding female, USNM 1116686, Bocas del Toro, Isla Colón, Boca del Drago, coral rocks, probably in cryptic sponge, depth 0.5–1 m, coll. A. Anker, 20 Oct 2005 [05-062b, specimen dissected].

Diagnosis. Rostrum distinctly lower than orbital hoods, rather broad at base, more or less slender, distinctly longer than orbital teeth, with subacute tip; orbital teeth triangular, broad at base, subacute; both rostrum and orbital teeth slightly up-turned distally; notches between orbital teeth and rostrum moderately deep, more U- than V-shaped. Antennular peduncles with second segment slightly longer than wide; stylocerite length variable from slightly to distinctly overreaching distal margin of first segment. Antenna with basicerite bearing blunt, feebly projecting distodorsal tooth; scaphocerite with very narrow blade, latter reaching midlength of scaphocerite and tip of distolateral tooth of basicerite. Third maxilliped with crown of six or seven spine-like setae on tip of ultimate segment. Major chela with palm almost three times as long as fingers; palmar distodorsal tooth swollen, with descendant, acute point. Second pereiopod carpus with five segments (exceptionally four), first carpal segment about four times length of second. Third pereiopod with propodus bearing six spine-like setae (not including distal pair), sometimes five or seven; dactylus moderately stout. Uropodal exopod with three or four fixed teeth (including lateral tooth of diaeresis) and slender movable spine-like seta. Telson with longitudinal median depression and two pairs of stout spine-like setae inserted anterior and posterior to mid-length, respectively; posterior margin broad, about half-length of anterior width (see Fig. 8 ); telson abnormalities apparently common ( Fig. 8 J). For detailed description of general features of S. paraneptunus species complex see Dardeau (1984) and Ríos & Duffy (2007).

Etymology. The name of this new species is derived from the combination of the Latin brevi - (short) and the Latinized-Greek dactylus (finger), referring to the comparatively short fingers of the major chela.

Colour pattern. Pale brownish, semitransparent, with red chromatophores on frontal region, antennules and third maxilliped; major chela pale beige, distal margin of palm and fingers olive-green tinge (except for pale area surrounded by darker margin on dactylus), tips amber-yellow; ovaries or fresh brood olive-green ( Fig. 14 C, D).

Size. Largest male, CL 3.8 mm; largest breeding female, CL 4.5 mm (holotype).

Distribution. Panama: Isla Grande and Bocas del Toro.

Life history. Apparently pair-living in cryptic sponges, Neopetrosia subtriangularis and possibly Calyx podatypa , growing among coral rubble on mixed seagrass / coral rubble bottoms, at depths ranging from 1 to 3 m.

Remarks. Synalpheus brevidactylus n. sp. appears to be close to S. paraneptunus as redefined above (i.e., based on the holotype), S. duffyi n. sp. and S. riosi , n. sp. Synalpheus brevidactylus n. sp. can be separtated from all these species, and also from the species described below, by the comparatively shorter fingers of the major chela (with palm / finger ratio being around 3 vs. 2–2.5 in the other species) ( Fig. 8 C, E); more specifically from S. paraneptunus by the distinctly longer stylocerite, slenderer rostrum, and a narrower blade ( Fig. 8 A, 9A); from S. duffyi n. sp., by the longer first segment in the carpus of the second pereiopod ( Fig. 8 G), a narrower blade of the scaphocerite ( Fig. 8 A), and larger size (breeding females: CL 4.15 mm in S. brevidactylus n. sp. vs. 3.1 mm in S. duffyi n. sp.); from S. riosi n. sp. by the shape of the distodorsal tooth on the palm of the major chela (which has a longer point in S. brevidactylus n. sp. and rather short point in S. riosi n. sp.), and longer spine-like setae on the propodus of the third pereiopod ( Fig. 8 H). At the type locality ( Isla Grande), S. brevidactylus n. sp. was collected twice, in both cases as a mated male-female pair, suggesting that this species may actually live in pairs, unlike the eusocial S. duffyi n. sp. and S. riosi n. sp.

The breeding female from Boca del Drago ( Bocas del Toro) differs from the two type specimens from Isla Grande by the slightly slenderer rostrum ( Figs. 8 A, 9A), the stylocerite reaching far beyond the distal margin of the first antennular segment ( Figs. 8 A, 9A), and the propodus of the third pereiopod bearing more spinelike setae – 10 instead of the usual 6–7 ( Fig. 9 C). All other features, including the shape and proportions of the major and minor chela, the ratio of the first and second carpal segments in the second pereiopod ( Fig. 9 B), and the armature on the uropodal exopod ( Fig. 9 D) are similar. Therefore, it is assigned to S. brevidactylus n. sp. with some hesitation.

Figures

FIGURE 8. Synalpheus brevidactylus n. sp., paratype, breeding female from Isla Grande, Panama (USNM 1116684) [A – J]; paratype, male (USNM 1116685) [K, L]: A, frontal region, dorsal view; B, third maxilliped, tip of ultimate segment, lateral view; C, major cheliped, chela, lateral view; D, same, carpus, merus and ischium, lateral view; E, same, chela, mesial view; F, major cheliped, chela and carpus, lateral view; G, second pereiopod, lateral view; H, third pereiopod, lateral view; I, left uropod, distolateral fixed teeth and spine-like seta, dorsal view; J, aberrant telson, dorsal view; K, right uropod, distolateral fixed teeth and spine-like seta, dorsal view; L, telson, dorsal view. Scale bar: 0.5 mm (A, B, F – L), 1 mm (C – E).

FIGURE 9. Synalpheus brevidactylus n. sp., breeding female from Boca del Drago, Bocas del Toro, Panama (USNM 1116686): A, frontal region, dorsal view; B, second pereiopod, lateral view; C, third pereiopod, lateral view; D, right uropod, distolateral fixed teeth and spine-like seta, dorsal view. Scale bar: 0.5 mm (A – D).

FIGURE 14. Life habitus and colour patterns. Synalpheus duffyi n. sp., Isla Grande, Panama [A, B]: A, larger queen and two smaller non-breeding colony members from the same colony, dorsal view; B, queen with embryos, lateral view. Synalpheus brevidactylus n. sp., Isla Grande, Panama [C, D]: C, breeding female and male (mated pair), dorsal view; D, breeding female, lateral view. Synalpheus bocas n. sp., Bocas del Toro, Panama [E – H]: E, male, dorsal view; F, breeding female; G, H, another breeding female, lateral and dorsal views on different backgrounds. Synalpheus belizensis n. sp., Carrie Bow Cay, Belize [I]: I, breeding female, dorsal view. Scale bars: ~ 2 mm.