Pachygrapsus loveridgei Chace 1966

Pachygrapsus loveridgei Chace, 1966 (Figures 6a–e, 14i, 15i) Pachygrapsus loveridgei Chace, 1966: 640, fig. 9–10 [type locality: St. Helena I.]. — Manning & Chace, 1990: 66 (Ascension I.). Pachygrapsus transversus — Miers, 1881: 432 (Ascension I.) [Not Pachygrapsus transversus (Gibbes, 1850)]. Type material Male holotype 10.3 x 13.1 mm (USNM 112457) and 6 paratypes (USNM 112467). Material Examined Central Atlantic. St. Helena I.: Rupert's Bay, on buoy cable, coll. A. Loveridge, 18 March 1960, 1 M 10.3 x 13.1 mm (Holotype USNM 112457); 11 February 1963, 3 M 5.5 x 6.8–7.7 x 9.5 mm, 1 F 6.2 x 7.9 mm, 2 ov. F. 5.0 x 6.7, 7.2 x 8.6 mm (Paratype USNM 112467); 1 M 8.1 x 10.0 mm (MNHN B17836). Diagnosis Carapace dorsal surface markedly convex; with glabrous striae on protogastric, hepatic, branchial region; mesogastric, cardiac, intestinal region smooth or with only few short striae (Fig. 6a). Lateral margins convergent posteriorly, with only one tooth behind exorbital angle. Anterior margin of front sinuous, 0.5 times exorbital width (Fig. 6b). Infraorbital margin minutely denticulate, with shallow outer notch (Fig. 14i). Outer face of chelae regularly convex, smooth except for conspicuous longitudinal line near lower margin, running nearly entire length of palm to tip of fixed finger (Fig. 6c). Cutting edges of fingers narrowly gaping, with several triangular teeth. Tip of fingers corneous, spoon­like, glabrous. Ambulatory legs with several scattered long bristles. P2 propodi with plumose setae on anterodorsal surface, forming light brush of setae. Lower margin of P5 with 1–3 submedian tubercles; distoventral angle with 2–3 spines (Fig. 6d). Abdominal tergites smooth; sixth somite of male broadly subrectangular, not triangular with telson (Fig. 6e). Distal process of G1 stout, sickle­like tip (Fig. 15i). Colour: Live coloration unknown. Chace (1966: 643) indicated the colour of freshly preserved specimens as "the carapace is mottled grayish brown with all transverse striae dark brown; chelipeds dark reddish brown dorsally, fading to light tan on outer surface of palm and to nearly white near tip of fingers; ambulatory legs mottled with brown, gray, and tan, proximal and distal ends of propodus and proximal end of dactyl nearly white, giving banded appearance to legs." Measurements. Medium size; carapace of specimens examined ranging from 5.0 x 6.7–10.3 x 13.1 mm. Chace (1966) and Manning & Chace (1990) indicated that cl varies between 1.9–12.4 mm, with 3.2 mm for the smallest ovigerous females. Distribution Central Atlantic: Ascension and St. Helena islands. Habitat Intertidal, but also on buoys, associated with barnacles, from near the surface to 7 meters. Remarks Pachygrapsus loveridgei is morphologically close to P. transversus (Gibbes, 1850). Both species have only one tooth on the lateral margins of the carapace behind exorbital angle, a conspicuous line on the outer face of the chelae near the lower margin, a brush of setae on the P2 propodi, and a male abdomen that is not apically triangular. P. loveridgei is smaller in size, the carapace is more convex, and the chitinous terminal portion of the G1 is broadly sickle shaped, rather than obliquely T­shaped as in P. transversus (Fig. 15i, l). Chace (1966: 644) indicated that 85 of the 211 specimens examined from St. Helena I. were found living near the surface on a buoy. This sporadic semi­pelagic way of life, along with its small size and markedly convex carapace, suggest affinities with species of Planes Bowdich, especially Planes marinus Rathbun, 1911, a species at one time included Pachygrapsus (see Chace, 1951).
Published as part of Poupin, Joseph, Davie, Peter J. F. & Cexus, Jean-Christophe, 2005, A revision of the genus Pachygrapsus Randall, 1840 (Crustacea: Decapoda: Brachyura, Grapsidae), with special reference to the Southwest Pacific species, pp. 1-66 in Zootaxa 1015 (1) on pages 23-25, DOI: 10.11646/zootaxa.1015.1.1, http://zenodo.org/record/5049232
{"references":["Chace, F. A. (1966) Decapod crustaceans from St. Helena Island, South Atlantic. Proceedings of the United States National Museum, 118, 623 - 660.","Manning, R. B. & Chace, F. A. (1990) Decapod and Stomatopod Crustacea from Ascension Island, South Atlantic Ocean. Smithsonian Contributions to Zoology, 503, i - v, 1 - 91.","Miers, E. J. (1881) Crustacea. In: Report on a collection made by Mr. T. Conry in Ascencion Island. Annals and Magazine of Natural History, ser. 5, 8, 432 - 434.","Gibbes, L. R. (1850) On the carcinological Collections of the Cabinets of Natural History in the United States. Proceedings of the Third Meeting of American Association for Advancement of Science, 3, 165 - 201.","Rathbun, M. J. (1911) Marine Brachyura. In: The Percy Sladen Trust expedition to the Indian Ocean in 1905 under the leadership of Mr. J. Stanley Gardiner. Vol. III, n ° XI. Transaction of the Linnaean Society London, ser. 2, Zoology, 14 (2), 191 - 261, pl. 15 - 20.","Chace, F. A. (1951) The oceanic crabs of the genera Planes and Pachygrapsus. Proceedings of the United States National Museum, 101, 65 - 103."]}