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).