Chaenostoma java Naderloo 2013, n. sp.
Creators: name: Naderloo, Reza
Publisher: name: Zenodo
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Macrophthalmidae
Chaenostoma
Chaenostoma java

description: Chaenostoma java n. sp.
(Figures 1A–F, 2A–D)
Material examined
Holotype. 1♂ (CL 9. 60 mm, CB 12.09 mm) (MHNG), Rosoeki, Java, July 1897, leg. Zehntner.
Paratypes. 1♂ (CL 8.97 mm, CB 11.24 mm), 4♀ ovig. (CL 7.94– 5.07 mm, CB 10.07– 6.89 mm) (MHNG), locality same as holotype.
Description
Carapace sub-rectangular (Figure 1A), about 1.2–1.3 times as broad as long, maximum width on posterior part of posterolateral margin; posterior surface with small granules scarcely on lateral regions, invisible with naked eyes; long setae on lateral regions, continuous to lateral margin. Regions weekly defined; furrows of gastric region distinct on posterior portion; cardiac region slightly elevated, intestinal region depressed. Frontal region (Figure 1A) downflexed, small granules over it; front wide, about 1/4 as wide as carapace width in anterior part, very slightly constricted medially; anterior edge slightly concave medially, with long setae, lateral margins of front nearly round; frontal furrow faint, shallow.
Eyestalks (Figure 1A) relatively stout, short, reaching to end of exorbital angle. Upper orbital margin regularly granulate, granules very small, round-tipped, slightly directed outwards, slightly larger laterally. Lower margin tuberculate, tubercles nearly triangular, directed inwards, getting larger in inner part.
Lateral margin (Figure 1A) with three teeth (including exorbital angle); first one (exorbital angle) wide triangle to relatively subquadrate, directed forward, making a wide concavity with upper orbital margin; posterior margin moderately arched, granulate; second longer than first one, lower than it, outer margin nearly straight, granulate; third very small, usually distinguishable, indicated by large granules; posterolateral margin relatively straight, diverging posteriorly, with small round granules, wide-based, long setae along it.
Third maxillipeds with large gap between. Ischium long, about 1.8 times as long as wide, slightly shorter than two times as long as merus, inner margin distally convex, with long setae along it, outer margin nearly straight, with short setae; circular pattern of long setae on proximal portion of outer surface, long setae irregularly along distal margin, short setae scarcely on outer surface. Merus quadrate, inner margin with long setae; outer margin nearly straight, arched proximally, long setae along distal part, outer surface widely depressed near inner margin, narrow depression near along outer margin.
Posteromedian margin of epistome straight, median part of anterior buccal cavity smooth, without any ridge.
Chelipeds (Figure 1C, D) nearly equal. Ischium denticulate on anterior margin, with long setae. Merus (Figure 1B) upper surface smooth, slightly elevated near inner margin, without chitinous plectrum; outer surface with transverse ridges of very small granules, sparsely covered with short setae; inner surface smooth, densely covered with long setae on distal two third: upper inner margin with small denticles, getting slightly larger distally, densely covered with long setae, setae continuous to anterior surface; inner lower margin with large triangular tubercles, larger distally, covered with scarce setae; outer margin denticulate, long setae scarcely along it. Carpus finely granulate on outer surface; margins with small denticles, some large denticles medially on inner margin, long setae along outer, inner, lower distal margins. Palm (Figure 1C) relatively swollen, about 1.2 times as long as high; outer surface (Figure 1C) smooth, with microscopic granules, slightly larger proximally, longitudinal granular ridge on lower portion, running from near tip of immovable finger backward, subparallel to lower margin; lower margin nearly straight, minutely granular, not deflexed near immovable finger; upper margin slightly arched, finely granular; inner surface (Figure 1D) with small granules on proximal portion, mostly covered with long setae, setal patch continuous along inner surface of fingers. Movable finger curved downward, curved inward distally, cutting edge with subproximal differentiated tooth, large, small denticles distal to large one. Immovable finger short, smooth proximally, without large differentiated tooth, teeth along proximal two-thirds, getting larger distally; large round gap between fingers, tip of fingers spooned, with long setae.
Female chelipeds (Figure 2A) small; palm nearly flat, inferior ridge prominent, parallel to lower margin, gently curving medially, granular, granules small distally; short longitudinal row of granules on middle portion, depressed above this ridge; upper margin granular, with small granules; inner surface of palm smooth, row of long setae near upper margin. Fingers relatively stout, movable finger distinctly longer than palm, long setae along inner surface, longitudinal ridge along outer surface, cutting edges of fingers smooth, chitinous ridge comb-shaped proximally.
Walking legs medium-sized, second, third legs largest, nearly in same length, fourth leg smallest, long setae scarcely along anterior margin of segments, except dactylus. Merus posterior surface smooth; anterior, posterior margins serrate, merus of second and third legs with subdistal tooth on anterior margin, merus of third leg about three times as long as wide. Carpus serrate on anterior and posterior margins; carpus of third leg slightly shorter than propodus. Propodus finely serrate on anterior and posterior margins, slightly longer than dactylus, that of last leg about as long as dactylus. Dactylus with scarce short setae on proximal portion, with six longitudinal smooth ridges; dense setal patch on anterior, posterior margins of daclytus and propodus of first leg; setal patch just on proximal parts of dactylus and propodus of second and third legs; fourth leg without setal patch.
Male abdomen long; segments 3, 4 nearly in same length, segment 5 distinctly longer than segments 3, 4, nearly as long as segment 6; segment 6 (Figure 2B) with lateral margins arched, very slightly swollen proximally, converging distally; telson slightly shorter than segment 6, margins arched, apically rounded.
G1 gently curved medially (Figure 1E); apical chitinous process short, directed laterally at nearly 60 ◦ (Figure 1F, G), lateral surface of apical process distinctly depressed, concave on apical surface; long setae around apical process, long feather-shaped setae along ventral margin, short feather-shaped setae along mesial margin.
Female abdomen round, segment 6 (Figure 2E) distinctly longer than telson, with arched lateral margins, telson distinctly wider than half as time as segment 6, slightly more than four times as wide as long.
Female gonopore (Figure 2C) small, with outer margin nearly straight, nearly parallel to median line of sternum; operculum small (Figure 2D), directed forwards laterally; margins of opening slightly elevated.
Habitat
The specimens were collected from the rocky intertidal, under small boulders.
Distribution
Presently only known from its type locality, Java (Indonesia) in the eastern Indian Ocean.
Etymology
The species is named after the type locality, Java in Indonesia.
Remarks
Chaenostoma java n. sp. is mainly characterized by a blunt exorbital angle, nondeflexed male cheliped, a dense setal patch covering the inner surface of the palm and fingers of the male chelipeds, a G1 with a short rounded apical process, and a female gonopore with a small operculum directed forwards. The non-deflexed male chelipeds and the morphology of the male G1 distinguish the new species from C. boscii (Audouin, 1826) and the widely distributed species C. sinuspersici (Naderloo and Türkay, 2011). Male chelipeds of the last two species are more or less deflexed downwards near the base of the immovable finger. The G1 of M. sinuspersici has the apical process of G1 distinctly mesiolaterally inclined, strongly emarginated, but the apical process of G1 of M. boscii is plate-shaped, directed obliquely in respect to stem (see Naderloo & Türkay 2011, figure 3). The relatively smooth dorsal surface of the carapace of C. java n. sp. is rather similar to that of C. lisae (Poupin and Bouchard, 2010) and C. punctulatus (Miers, 1884). The latter has been described as having a completely smooth dorsal carapace surface (see Miers 1884; Barnes 1967, p. 229), whereas C. java n. sp. and C. lisae have few scattered granules on the frontal and the lateral regions of the carapace. It should be noted that Miers (1884, pl. XXV, figure A) described C. punctulatus based on a single female from Port Jackson, New South Wales, Australia. Miers mentioned a large differentiated tooth on the cutting edge of the immovable finger and a smaller one on the cutting edge of the movable finger, which are clearly seen in his drawings (Miers 1884, pl. XXV, figure A). Barnes (1967, p. 229, figure 10d) examined a large number of specimens from eastern and southern Australia and mentioned that only the movable finger has the differentiated tooth.
Two characters examined here, the male G1 and female gonopore, are proposed to be important diagnostic characters among the species of the group (Naderloo & Türkay 2011). Chaenostoma java n. sp. is rather similar to C. lisae in these two characters and these two species are not easily distinguishable from each other. Chaenostoma java n. sp. differs from C. lisae by having a setal patch on the inner surface of the male cheliped palm extending to the fingers (see Figure 1D), whereas in C. lisae the setal patch is present only on the inner surface of the palm and the fingers are glabrous. Furthermore, in the new species a proximal large gap is recognized between the male cheliped fingers with a distinctly differentiated tooth on the cutting edge of the movable finger, whereas in C. lisae there is no gap between the fingers and the tooth of the movable finger is low and not very differentiated as in other species of the group (see Figure 3C, D; Poupin & Bouchard 2010, figure 2F, G).
description: Published as part of Naderloo, Reza, 2013, The sentinel crabs of the genus Chaenostoma (Stimpson, 1858) (Crustacea: Brachyura: Macrophthalmidae), with description of a new species and new records, pp. 2835-2848 in Journal of Natural History 47 (45 - 46) on pages 2837-2842, DOI: 10.1080/00222933.2013.807948, http://zenodo.org/record/5198062