Philarius gerlachei ( Nobili, 1905 )

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 : 2-6

Philarius gerlachei ( Nobili, 1905)

( Figs. 1–3 )

Harpilius gerlachei Nobili, 1905: 160 ; Nobili, 1906: 45, pl. 4, fig. 10.

Philarius gerlachei— Holthuis, 1952: 152, fig. 69; Bruce, 1982: 169, 170; Bruce, 1994: 116; Li 2000: 251.

Type material. Periclimenes gerlachei Nobili : 2 ovigerous females and 4 mature males (MNHN-Na 1899), Persian Gulf, sta, LIII, “parmi les polypiers” = among corals, expedition of J. Bonnier and C. Pérez.

Description. Medium-sized pontoniine shrimp with depressed body. Carapace smooth; antennal tooth strong, sharp. Rostrum long, compressed, slightly descendant or horizontal, with tip not reaching distal margin of scaphocerite blade; dorsal lamina with four large teeth, most-posterior tooth situated anterior to orbit; most-distal portion of rostrum toothless; ventral lamina with single tooth situated slightly anterior to mid-length of rostrum; proximolateral rostral lamina without supraocular lobe. Orbit with inferior orbital angle bluntly produced. Pterygostomial angle bluntly produced anteriorly.

Abdominal somites smooth; pleura of first to fifth abdominal somites (= Abd1–5) rounded. Telson narrow, about 2.6 times as long as proximal width, narrowing distally, with two pairs of dorsal submarginal spines inserted at about 0.6 and 0.8 of telson length, respectively; distal margin armed with three pairs of spines, including one pair of short lateral spines, one pair of longer intermediate spines and one pair of median spines shorter than intermediate spines.

Eyes large, with subovate cornea; eyestalk cylindrical, about as long as wide, with well-marked accessory pigment spot.

Antennule with basal segment about as long as wide, distolateral angle with acute tooth; ventromesial tooth small, acute; proximal fused portion of lateral (= upper) antennular flagellum with at least 25 segments, accessory ramus with three segments. Antenna with basicerite bearing sharp distoventral tooth; scaphocerite about 2.5 times as long as maximal width; blade narrow, strongly convex distally; distolateral tooth strong, acute, reaching slightly beyond distal margin of blade.

Mouthparts not dissected in syntypes, appearing typical for genus in external view (see Fig. 6 illustrating mouthparts of closely related P. polynesicus n. sp.). Third maxilliped (= Mxp3) robust, with well-developed exopod; lateral plate of coxa ear-shaped, curved distally; arthrobranch absent.

First pereiopod (= P1) relatively slender, moderately setose; coxa with curved distoventral lobe; basis as long as wide; ischium about three times as long as wide, distal margin bluntly projecting over ischio-meral articulation; carpus slender, slightly longer than merus, twice as long as wide, flaring distally, with several stout simple setae at carpo-propodal articulation; palm approximately as long as wide, subcylindrical; fingers, simple, tapering distally, about half as long as palm, 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.

Second pereiopod (= P2) subsymmetrical in shape, subequal in size, robust; surface of distal segments covered with numerous simple setae; carpus cup-shaped, flaring distally, with two triangular blunt teeth ventrally, distodorsal margin rounded; palm subcylindrical, about three times as long as wide, smooth; fingers robust, about three times as long as wide, more than half-length of palm, with acute, curved tips; cutting edges bearing a few small subtriangular teeth proximally; rounded depression present on ventroproximal portion of dactylus.

Third to fifth pereiopods (= P3–5) similar in general shape, robust; P3 with ischium, merus and carpus unarmed, covered only with small simple setae; propodus about 3.5 times as long as wide, with straight lateral margins, with three tufts of long simple setae along distoventral margin and one row of simple setae on distal margin; dactylus simple, stout, strongly curved, distally acute.

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

Colour pattern. The colour of the type specimens was described as “vert bouteille” = bottle-green ( Nobili 1906). To our knowledge, there are no published photographs of P. gerlachei from the Indian Ocean. Bruce (1982) provided a black-and-white drawing showing the colour pattern of P. gerlachei from the Great Barrier Reef, which, however, is characterised by the presence of large dark dorsolateral spots on the first three abdominal somites.

Ecology. Appears to be associated with a variety of species of the genus Acropora , e.g., A. digitifera (Dana) ( Bruce & Coombes 1995) .

Type locality. Persian Gulf.

Distribution. Widely distributed in the Indo-West Pacific, ranging from the Red Sea and East Africa to French Polynesia and Japan (e.g., Bruce 1982; Chace & Bruce 1993; for full list of records see Li 2000); however, at least some of the previous records may refer to one of the below-described new species.

Remarks. Bruce (1982) gave the rostral formula for P. gerlachei as 3–5 / 1. Interestingly, in four examined syntype specimens, the rostral formula is 4 / 1, which so appears to be the typical rostral formula for P. gerlachei s. str. (sensu Nobili 1905). The proportions of the carpus and the palm / fingers ratio of P2 also appear to be variable in P. gerlachei . Nobili (1906) noted in the text (p. 47) that in some of his specimens, the carpus was proportionally shorter than shown in his figure ( Nobili 1906, fig. 10a; see also Fig. 1 A, B). Some differences also exist in the armature of the finger cutting edges in P2; for instance, specimens from southern China have only two proximal teeth on the dactylus (Li 2007, fig. 153e).

Philarius gerlachei is closely related to the four species described below, but can be separated from each of them by a combination of subtle morphological characters summarised in Table 1 [see also Remarks under each species below].

Figures

FIGURE 1. Philarius gerlachei (Nobili, 1905), syntypes from Persian Gulf (MNHN-Na 1899): A, male, dorsal view; B, ovigerous female, dorsal view; C, same as B, lateral view. Scale bars = 2 mm.

FIGURE 2. Philarius gerlachei (Nobili, 1905), female, syntype from Persian Gulf (MNHN-Na 1899): A, carapace and frontal appendages, lateral view; B, frontal region, dorsal view; C, D, eyestalk, dorsal view; E, antennal scaphocerite and basicerite, dorsal view; F, telson, dorsal view.

FIGURE 3. Philarius gerlachei (Nobili, 1905), syntypes from Persian Gulf (MNHN-Na 1899): A – D, carapace, lateral view; E, male second cheliped, dorsal view; F, female second cheliped, dorsal view.

FIGURE 6. Philarius polynesicus n. sp., paratype, ovigerous female from Moorea, French Polynesia (FLMNH UF Arthropoda 16159): A, mandible; B, maxillula; C, maxilla; D, first maxilliped; E, second maxilliped; F, third maxilliped, all in lateral view.