Philarius minor, 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 : 17-20

Philarius minor n. sp.

( Figs. 13–15 , 19 C, D)

Type material. Holotype: ovigerous female, pcl 2.6 mm (QM W29050), Australia, Great Barrier Reef off S Queensland, Heron Island, sta. 125, 23.47262 S, 151.95988 E, outer reef, depth 14–16 m, in Acropora sp., coll. F. Michonneau, S. McKeon, N. Bruce and others, 28.XI.2009 (fcn AUST 6627). Paratypes: 1 male, pcl. 2.2 mm (QM W29051), same collection data as for the holotype (fcn AUST 6626); 1 non-ovigerous female, pcl 2.9 mm ( FLMNH UF Arthropoda 24982), Australia, off S Queensland, Great Barrier Reef, Heron Island, Broomfield Reef, sta. 25, 23.26012 S, 151.91692 E, shallow reef, depth: 3–6 m, in Acropora sp., coll. S. McKeon, F. Michonneau, G. Cranich and others, 15.XI.2009 (fcn AUST 5136); 1 male, pcl 2.6 mm ( FLMNH UF Arthropoda 24983), same collection data as for the previous specimen (fcn AUST 5137).

Description. Small-sized pontoniine shrimp with depressed body. Carapace smooth; antennal tooth sharp. Rostrum long, compressed, more or less straight, with slightly ascendant tip overreaching distal margin of scaphocerite blade; dorsal lamina with four large dorsal teeth all situated anterior to orbit; most-distal portion of rostrum toothless; ventral lamina with one tooth situated slightly anterior to half-length of rostrum; proximolateral rostral lamina well developed, with blunt supraocular lobe adjacent to rostral base. 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 0.5 and 0.7 of telson length, respectively; posterior margin with three pairs of spines, including one pair of short stout lateral spines, one pair of long slender intermediate spines and one pair of simple medial spines subequal in length to intermediate spines.

Eyes as described for P. gerlachei .

Antennule with basal segment about as long as wide; distolateral angle with acute tooth; ventromesial tooth small, acute; proximal fused portion of lateral antennular flagellum with eight segments, accessory ramus with two segments. Antenna with basicerite bearing sharp distoventral tooth; scaphocerite rather broad, about twice as long as maximal width, overreaching intermediate segment of antennular peduncle; blade strongly convex distally; distolateral tooth strong, acute, reaching well beyond distal margin of blade.

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

P1 smooth, moderately setose; coxa with curved distoventral lobe; basis as long as wide; ischium about 2.5 times as long as wide, with projecting blunt lobe distally; merus slender, about four times as long as wide; carpus slender, slightly longer than merus, about 4.5 times as long as wide, flaring distally, with several stout simple setae at carpo-propodal articulation; palm about 1.5 times as long as wide, subcylindrical; fingers stout, 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 symmetrical in shape, slightly unequal in size, fairly robust, somewhat larger in males than in females; coxa with curved distoventral lobe; ischium about twice as long as wide; merus about three times as long as wide, with straight margins; carpus vase-shaped, flaring distally, swollen mesially; distal margin with two blunt ventral projections, dorsal margin rounded; palm subcylindrical, about four times as long as wide, smooth; fingers slender, about 0.7-0.8 palm length, about four times as long as wide; cutting edges armed with small subtriangular teeth along entire length; finger tips acute, simple, curved.

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

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

Colour pattern. Body semitransparent, pale greenish, with minute, barely noticeable reddish chromatophores on carapace and abdomen; P1 and P3–5 semitransparent, with white patch distally; P2 semitransparent with greenish and blue-purplish tinge, palm with some orange and green iridescence; antennular and antennal flagella purplish blue; corneas pale golden-brownish ( Fig. 19 C, D).

Etymology. Referring to the relatively small size of this new species ( minor = smaller, inferior in Latin), which appears indeed to be one of the smallest species in the genus Philarius ; used as noun in opposition.

Ecology. All specimens were extracted from colonies of Acropora sp., at a depth range of 3– 16 m.

Distribution. Presently known only from the type locality in Heron Island, Great Barrier Reef off S Queensland, Australia.

Remarks. Philarius minor n. sp. is morphologically very similar to P. gerlachei , P. polynesicus n. sp., P. r u f u s n. sp. and P. albimaculatus n. sp., differing from all of them by the presence of blunt supraocular lobes on each side of the rostral base ( Fig. 14 B, C). It differs specifically from P. polynesicus n. sp. by the more slender rostrum, overreaching the distolateral tooth of the scaphocerite (vs. not reaching it in P. p o l y n e s i c u s n. sp.); the shorter antennal scaphocerite; and the more slender P2 chela in both males and females; from P. r uf us n. sp. by the dorsoventrally flattened body (vs. more laterally compressed in P. r u f u s n. sp.); and from P. albimaculatus n. sp. by the absence of a blunt crest on the distodorsal margin of the P2 palm. Philarius minor n. sp. also appears to have fewer segments (8) in the fused portion of the lateral antennular flagellum than P. gerlachei (~25), P. p o l y n e s i c u s n. sp. (~15) and P. r u f u s n. sp. (11), but more than P. albimaculatus n. sp. (5). In life, P. m i n o r n. sp may be separated from P. polynesicus n. sp., P. r u f u s n. sp., and P. albimaculatus n. sp. by the colour pattern, especially the conspicuously purplish-blue coloured antennular and antennal flagella (vs. whitish or pale orange in other species, cf. Figs. 9 , 19 ). In addition, P. m i n o r n. sp. appears to be one of the smallest species within the P. gerlachei complex, with all available specimens ranging 2.8–3.2 mm cl (although the only available specimen of P. albimaculatus n. sp. is even smaller at cl 2.4 mm, see below) [see also Table 1].

Figures

FIGURE 9. Philarius polynesicus n. sp., paratype, ovigerous female from Moorea, French Polynesia (FLMNH UF Arthropoda 16159) [A – C]; holotype, male from Moorea (FLMNH UF Arthropoda 16148) [D, E]; colony of Acropora valida (Dana), host of P. polynesicus n. sp. in Moorea [F]. Photographs: A-E by A. Anker; F by G. Paulay.

FIGURE 13. Philarius minor n. sp., paratype, female from Heron Island, Australia (FLMNH UF Arthropoda 24982), lateral view. Scale bar = 2 mm.

FIGURE 14. Philarius minor n. sp., paratypes, ovigerous female from Heron Island, Australia (FLMNH UF Arthropoda 24982) [A-C, E-H]; male from Heron Island, Australia (QM W 29051) [D]: A, B, D, anterior carapace, lateral view; C, frontal region, dorsal view; E, antennule, lateral view; F, scaphocerite, dorsal view; G, telson, dorsal view; H, sixth abdominal somite, telson and uropods, ventral view.

FIGURE 15. Philarius minor n. sp., paratypes, ovigerous female from Heron Island, Australia (FLMNH UF Arthropoda 24982) [A-F, I, J]; male from Heron Island, Australia (QM W 29051) [G, H]: A, first pereiopod, lateral view; B, same, chela, mesial view; C, D, same, distal margin of ischium, lateral (C) and mesial (D) view; E, third pereiopod, lateral view; F, same, distal propodus and dactylus; G – I, second pereiopod, dorsal view; J, same, carpus.

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.