Camatopsis Alcock & Anderson 1899
Creators: name: Ng, Peter K. L.
name: Castro, Peter
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Chasmocarcinidae
Camatopsis

description: Genus Camatopsis Alcock & Anderson, 1899
Camatopsis Alcock & Anderson, 1899: 13.—Alcock 1899: 75; 1900: 318 [in key], 328.— Tesch 1918: 202 [in key], 234.— Balss 1957: 1658.— Serène 1964a: 268.— Sakai 1976: 542 [in key], 552.— Hsueh & Huang 2002: 113 [in key].—Ng et al. 2008: 76 [in list].— De Grave et al. 2009: 32 [in list].—Castro et al. 2010: 41.— Komai et al. 2012: 144.
Type species. Camatopsis rubida Alcock & Anderson, 1899 (gender feminine). Other species included:
Camatopsis africana n. sp.
Camatopsis leptomerus n. sp.
Camatopsis minor n. sp.
Camatopsis thula n. sp.
Camatopsis valida n. sp.
Diagnosis. Carapace subtrapezoidal, high; front bilobed, with shallow or deep median cleft; anterolateral margins arcuate, minutely granular, without distinct lobes or teeth. Epistome slightly depressed; semicircular median lobe with deep median fissure, semicircular lateral margins without visible fissures. Eye peduncle filling orbit, short, slightly mobile; cornea reduced, with reduced pigmentation. Third maxillipeds almost entirely fill buccal cavern when closed; merus subcircular, anteroexternal angle produced to different degrees; ischium subquadrate or slightly elongated, about same length as merus. Chelipeds subequal in length, slightly dissimilar in females, heteromorphic in males; cutting margins blade-like, lined with short setae, at least distal part of pollex with sharp spines that overlap dactylus when closed, most proximal teeth on cutting margins of major chela of males enlarged. Inner margin of cheliped carpus smooth or with tooth (C. africana males). Ventral surface of cheliped merus without teeth or conspicuous tubercles. Meri of ambulatory legs with microscopic granules, unarmed; long setae along margins of propodi, dactyli. P5 dactylus upcurved. Fused thoracic sternites 1, 2 triangular, short; fused thoracic sternites 3, 4 relatively broad. Male pleon lateral margins of somite 6 convex, of fused somites 3–5 nearly straight; telson proportionally short. Sterno-pleonal cavity of male deep, press-button for pleonal holding as small, short tubercle just posterior to thoracic sternal suture 4/5 at edge of sterno-pleonal cavity. Male thoracic sternite 8 short, quadrate; “supplementary plate” short, longer at rounded outer margin; structures tightly appressed with most of penis concealed. G1 stout, distal segment slightly curved, distal segment curved inwards or upwards, with short to long spinules. G2 short, about 3/4 G1 length, straight, slender, with long basal segment, conspicuously short distal segment. Female pleon with lateral margins of somites strongly convex; telson proportionally short. Sterno-pleonal cavity of female moderately deep, vulvae close together or widely separated.
Remarks. Long regarded as monotypic, “ Camatopsis rubida,” which Alcock & Anderson (1899) described in Rhizopinae, has been reported from many locations in the Indo-West Pacific region. Comparisons of a large series of specimens from the range shows that there are consistent differences in the proportions of the ambulatory legs, form of the male pleon and G1 structures, and six species can in fact be recognised.
The genus is closest to Microtopsis in the form of the carapace and chelipeds. Komai et al. (2012) listed a suite of characters that separate Camatopsis from Microtopsis. The third maxilliped merus of Microtopsis is subovate without any anteroexternal expansion (Fig. 80 A) (merus more quadrate with the anteroexternal angle auriculiform in various degrees in Camatopsis, e.g., Fig. 30 A); the cutting margins of the fingers of the minor chelae have comblike setae and no sharp teeth (Fig. 48 B) (with one or two sharp teeth in Camatopsis, e.g., Fig. 39 B); male thoracic sternites 7 and 8 are proportionately broader (Fig. 62 A) than in Camatopsis (Fig. 58 A); the male pleon is proportionally shorter (Fig. 80 B) than in Camatopsis (e.g., 51A); the G1 is short, stout, distinctly twisted medially, with the distal part broad and shortened (Figs. 81 A‒E) (slender and elongated, with the distal part tapering in Camatopsis; e.g., Fig. 67 A, B); and the G2 is as long as the G1 (Fig. e.g., 81F) (G2 shorter, about 3/4 G1 length in Camatopsis, e.g. Fig. 67 C).
Prior to this revision, adults of Camatopsis species were believed to be large, with carapace widths of approximately 8 mm or more; with Microtopsis maturing at carapace widths of only 3 mm (see Komai et al. 2012). The discovery of C. minor n. sp. and C. valida n. sp. as well as a good series of specimens of C. leptomerus changes our perspective on these differences. The structure of the male pleon and G1 remains diagnostic, and easily distinguishes Microtopsis from Camatopsis. The structures of the third maxilliped and chela, on the other hand, appear to be size-dependent. Specimens of C. leptomerus up to 7.0 mm in carapace width (e.g., CP2383, ZRC 2015.139) are typical, with the anteroexternal angle of the third maxilliped merus with auriculiform anteroexternal angle and the minor chela possessing the two vertical teeth on the cutting margin of the propodus. Smaller specimens, especially those below 6.0 mm in carapace width have the third maxilliped merus varying from subovate to round but without an auriculiform anteroexternal angle (Fig. 68 E‒H), and the cutting margin of the minor chela propodus is entire, without any vertical teeth. Surprisingly, the G1 structure even in the very small males of C. leptomerus (e.g., two males 3.1 × 3.4 mm, 4.7 × 5.9 mm; ZRC 2015.120) is distinct, resembling that of the adult (Fig. 68 A‒D). Although the G1s of these small males is relatively more slender, the distal part is twisted with the tip distinctly turned upwards (when detached and with the ventral surface facing the observer) (Figs. 68 A‒D). Although the distal part of the G1 is gently twisted when the G1 is still attached on the pleon and when it is viewed at an angle, the distal third appears to be curving outwards, as depicted by Tesch (1918: pl. 16 fig. 3i). Camatopsis minor n. sp. is also a small-size species like Microtopsis, maturing at carapace widths of about 4 mm. The merus of the third maxilliped has a subauriculiform anteroexternal angle but less well developed than adults of other Camatopsis species. Although the larger male chela is slightly inflated, the cutting margin of the propodus of the smaller chela is entire, without the two vertical teeth. Its G1 structure resembles those of its congeners (Fig. 69 C‒E), and is not strongly twisted with the distal parts adorned with long setae (see discussion for C. minor). The structure of the male pleon and position of the vulvae of C. minor are like those of its congeners.
Distribution. Indo-West Pacific region: Indian to western Pacific oceans.
description: Published as part of Ng, Peter K. L. & Castro, Peter, 2016, Revision of the family Chasmocarcinidae Serène, 1964 (Crustacea, Brachyura, Goneplacoidea), pp. 1-182 in Zootaxa 4209 (1) on pages 31-32, DOI: 10.11646/zootaxa.4209.1.1, http://zenodo.org/record/272646