Amarinus pristes, Rahayu & Ng, 2004

Rahayu, Dwi Listyo & Ng, Peter K. L., 2004, The Hymenosomatidae (Crustacea, Decapoda, Brachyura) of Timika (Irian Jaya, Indonesia), Zoosystema 26 (1), pp. 87-94 : 91-93

Amarinus pristes n. sp.

( Fig. 2 )

HOLOTYPE. — Indonesia. Kamora , intertidal, mud substrate in mangrove area, 21.IX.2001, coll. I. Ermayanti, 4.2 × 4.3 mm ( MZB).

PARATYPES. — Indonesia. Otakwa, estuary, 5.II.1999, coll. A. Haris, 1 5.5 × 5.7 mm ( ZRC 2002.596).

Kamora, intertidal, mud substrate in mangrove area, 21.IX.2001, coll. I. Ermayanti, 2 3.0 × 2.9 mm, 4 × 4.1 mm ( RCO); 17.X.2001, 1 4.4 × 4.4 mm ( ZRC 2002.598); 5.X.2001 ,1 4.1 ×4.0mm ( MNHN). Ajkwa, intertidal, mud substrate in mangrove area, 16.X.2001, coll. I. Ermayanti, 1 5.1 × 5.0 mm, 1 3.7 × 3.5 mm ( ZRC 2002.597); 3.X.2001, 1 3.4 × 3.5 mm ( MZB); 22.X.2001, 1 4.5 × 4.3 mm, 1 4.5 × 4.3 mm ( MNHN).

ETYMOLOGY. — The name refers to the lateral margin of the carapace (from the Greek prion for saw). The name is used as a noun in apposition.

DESCRIPTION

Male holotype

Carapace ( Fig. 2A ) flat, circular, as long as broad or very slightly longer or shorter than broad, surrounded by complete and distinct rim, not interrupted at base of rostrum. Dorsal surface smooth, cervical, thoracic and gastrocardiac grooves distinct; cervical and thoracic grooves approaching but not reaching antero- and posterolateral margins respectively. Lateral margins crenulated, with strong, distinct teeth on anterior margin and between coxae of third and fourth pereiopods. Rostrum unilobed, broad, surface concave, not continuous with dorsal surface of carapace. Eyestalk prominent, clearly visible dorsally.

Third maxillipeds ( Fig. 2B ) almost fill mouth field when closed. Ischium of third maxilliped shorter than merus along outer lateral edge; short setae on inner lateral margin of ischium; longer setae on inner lateral margin of merus; inner lateral margins of ischium and merus meeting when closed. Palp not longer than merus, exopod much longer than merus.

Chelipeds ( Fig. 2C ) equal, slightly shorter than ambulatory legs; cutting edges of fingers serrated with denticles, tip of fingers sharp, gaping proximally when closed, strong median tooth on dactylus. Dactylus slightly shorter than palm, pollex gently curved inwards. Upper and lower margin of dactylus, propodus, carpus and merus scarcely setose.

Ambulatory legs (pereiopods 2-5) stout, crosssection circular, dorsal and ventral edges sparsely setose. Dactylus slightly shorter than propodus, slightly curved with tip sharply hooked, recurved subterminal tooth, ventral edge more densely lined with long and short setae. Propodus slightly longer than carpus; merus about 1.75 times length of carpus.

Abdomen ( Fig. 2E ) five-segmented, with pleotelson free, triangular, segment 1 shortest, widest; segment 3 longest; segments 4 and 5 similar length, tapering to pleotelson; pleotelson bluntly triangular, approximately same length as segment 3, with lateral intercalated plates basally; press-button system as described by Guinot & Bouchard (1998). Male G1 ( Fig. 2F ) stout, tip curved, truncate.

Female

In larger female specimens, crenulations on lateral carapace margin stronger ( Fig. 2G ); in smaller females, crenulations as in male. Chelipeds more slender than those of males, cutting edges of fingers not serrated, without tooth on dactylus. Abdomen ( Fig. 2H ) five-segmented (excluding pleotelson), submedial groove running almost entire length, defining convex central region; all intersegmental sutures distinct, covering entire sternum for larger specimens (e.g., 5.5 × 5.7 mm, ZRC 2002.596), not covering entire sternum for smaller specimens, longer than broad, pleotelson broadly triangular.

REMARKS

The genus Amarinus (type species Elamena lacustris Chilton, 1882 ) is a small genus of wholly to mostly freshwater species with a Gondwanic distribution. Only one species has previously been reported from Indonesia, viz. A. crenulatus Ng & Chuang, 1996 , from Sulawesi. With regards to the uneven to serrated lateral carapace margin, A. pristes n. sp. is most similar to A. wolterecki (Balss, 1934) ( Philippines) and A. crenulatus . It can be distinguished from A. wolterecki by the form of male G1 that is curved and truncate at tip while it is straight and tapering at tip in A. wolterecki . The male abdomen of A. wolterecki is also proportionally more slender than in A. pristes n. sp. (see Ng & Chuang 1996). From A. crenulatus , A. pristes n. sp. can easily be separated by its relatively shorter ambulatory pereiopods, notably the merus and dactylus (cf. Ng & Chuang 1996). The male abdomen of A. pristes n. sp. agrees with what has been described in detail for the genus by Guinot & Richer de Forges (1997: 467, fig. 4B-D).

At present A. pristes n. sp. is only known from the type locality in Kamora, Irian Jaya, Indonesia.

Figures

FIG. 2. — Amarinus pristes n. sp.; A-F, holotype 4.2 × 4.3 mm (MZB); G, H, paratype 5.5 × 5.7 mm (ZRC 2002.596); A, G, carapace; B, left third maxilliped; C, right cheliped; D, left third pereiopod; E, abdomen; F, right G1; G, abdomen. Scale bars: 1.0 mm.