Philarius albimaculatus, Marin, Ivan & Anker, Arthur, 2011

Marin, Ivan & Anker, Arthur, 2011, A partial revision of the Philarius gerlachei (Nobili, 1905) species complex (Crustacea, Decapoda, Palaemonidae), with description of four new species, Zootaxa 2781, pp. 1-28 : 22-26

Philarius albimaculatus sp. nov.

( Figs. 16–18 , 19 E, F)

Type material. Holotype: male, pcl. 1.9 mm ( FLMNH UF Arthropoda 14472), Madagascar, Nosy-Bé. W side of Sakatia, 13.2989º S 48.1472º E, gentle reef slope with rocks, algae and corals, in Acropora sp., depth: 3–8 m, coll. G. Bakary, H. Bruggemann, F. Michonneau, G. Paulay, T. Werner, processed by A. Anker, 18.V.2008 (fcn NBE 1817).

Description. Small-sized pontoniine shrimp with depressed body. Carapace smooth; antennal tooth sharp. Rostrum long, compressed, slightly descendant, with tip overreaching distal margin of scaphocerite blade; dorsal lamina with five large teeth and one small subapical tooth, in addition to one tooth in post-orbital position; ventral lamina with one tooth situated at about 0.7 rostrum length; proximolateral rostral lamina without supraocular lobe. Pterygostomial angle bluntly produced anteriorly.

Pleura of Abd1–5 rounded. Telson about twice as long as proximal width, narrowing distally, with two pairs of dorsal submarginal spines inserted at about 0.5 and 0.75 of telson length, respectively; posterior margin with three pairs of spines, including one pair of short lateral spines, one pair of long intermediate spines and one pair of simple medial spines about 0.8 of length of intermediate spines.

Eyes as described for P. gerlachei .

Antennule with basal segment about 1.3 times as long as wide; distolateral angle with acute tooth; ventromesial tooth small, acute; proximal fused portion of lateral antennular flagellum with five segments, accessory ramus apparently with only one segment. Antenna with basicerite bearing sharp distoventral tooth; scaphocerite broad, about twice as long as maximal width, overreaching end of antennular peduncle; blade broadly rounded distally; distolateral tooth strong, acute, reaching beyond distal margin of blade.

Mouthparts typical for genus. Mxp3 as described for P. gerlachei .

P1 smooth, moderately setose; coxa with well-developed curved distoventral lobe; basis as long as wide; ischium about three times as long as wide, with distally projecting blunt lobe; merus slender, about four times as long as wide; carpus slender, slightly longer than merus, about four times as long as wide, flaring distally, with several stout simple setae at carpo-propodal articulation; palm about as long as wide, subcylindrical; fingers stout, about half as long as palm, simple, tapering distally, about 2.5 times as long as wide, with straight cutting edges; fixed finger with one tuft of stiff plumose setae at mid-length of lateral margin.

P2 subsymmetrical in shape, slightly unequal in size, slender, covered with simple setae distally; ischium about twice as long as wide; merus about three times as long as wide, with straight margins; carpus flaring distally, slightly swollen mesially, with two blunt projections distoventrally and rounded dorsal margin; palm subcylindrical, about 3.5 times as long as wide; distodorsal surface of palm somewhat elevated forming a blunt crest near propodo-dactylar articulation; fingers slender, equal to palm in length, about five times longer than wide; cutting edges armed with minute triangular teeth along entire length; finger tips acute, simple, curved.

P3–5 similar in general shape, robust; P3 with ischium, merus and carpus unarmed, covered with simple setae; propodus about five times as long as wide, with straight, smooth margins, with seven tufts of long simple setae along ventral margin and one tuft of simple setae on distal margin; dactylus simple, strong, curved, distally acute.

Uropods slightly exceeding telson; distolateral tooth and spine subequal in length, moderately strong.

Colour pattern. Body semitransparent; carapace with large white patches dorsally (some of them possibly on internal organs); abdomen mostly transparent, with conspicuous, broad white band on sixth somite, near telson; P3–5 transparent with large white bands near articulations; P2 similar to P3–5, in addition with large white patch on proximal portion of palm; distal portion of palm and fingers also white ( Fig. 19 E, F).

Etymology. Referring to the species-diagnostic white spots ( albimaculatus = white-spotted or white-speckled in Latin); used as adjective.

Ecology. The single holotype specimen was found in Acropora sp., at a depth of 3– 8 m.

Distribution. Presently known only from the type locality in Nosy-Bé, northwestern Madagascar.

Remarks. Philarius albimaculatus n. sp. is related to the other four species of the P. gerlachei complex, differing from them by the greater number of teeth on the dorsal lamina of the carapace (7 teeth vs. 4–5 teeth in the other species); the very short proximal portion of the lateral antennular flagellum (5 segments vs. 8–25 segments in the other species); the presence of a blunt crest on the distolateral surface of the P2 palm; and the larger number of setal tufts on the ventral margin of the P3 propodus (7 setal tufts vs. 4–5 tufts in the other species). In life, P. albimaculatus n. sp. can be easily recognised by its characteristic colour pattern, in particular by the white spots and patches on the body and appendages ( Fig. 19 E, F) [see also Table 1].

Figures

FIGURE 16. Philarius albimaculatus n. sp., holotype, male from Nosy-Bé, Madagascar (FLMNH UF Arthropoda 14472), dorsal and lateral views. Scale bar = 2 mm.

FIGURE 17. Philarius albimaculatus n. sp., holotype, male from Nosy-Bé, Madagascar (FLMNH UF Arthropoda 14472): A, frontal region, dorsal view; B, same, lateral view; C, antennule, dorsal view; D, antenna, dorsal view; E, telson and uropods, dorsal view; F, first pereiopod, lateral view; G, same, chela, mesial view; H, distolateral margin of uropodal exopod, dorsal view.

FIGURE 18. Philarius albimaculatus n. sp., holotype, male from Nosy-Bé, Madagascar (FLMNH UF Arthropoda 14472): A, right second pereiopod, dorsal view; B, left second pereiopod, dorsal view; C, chela of right second pereiopod, lateral view; D, E, same, distal propodus and fingers, mesial view; F, third pereiopod, lateral view; G, same, carpus, propodus and dactylus, ventrolateral view.

FIGURE 19. Colour patterns of three species of Philarius: A, B, Philarius rufus n. sp., holotype, ovigerous female from Heron Island, Australia (QM W 29052); C, D, Philarius minor n. sp., holotype, ovigerous female (C) and paratype male (D) from Heron Island, Australia (QM W 29050, W 29051); E, F, Philarius albimaculatus n. sp., holotype, male from Nosy-Bé, Madagascar (FLMNH UF Arthropoda 14472). Photographs: A-D by F, Michonneau; E, F by A. Anker.