Petrolisthes aegyptiacus Werding & Hiller, 2007

Hiller, Alexandra & Werding, Bernd, 2016, A new species of the genus Petrolisthes Stimpson (Crustacea, Decapoda, Porcellanidae) from the Central Pacific, with remarks and new records for P. aegyptiacus Werding & Hiller, ZooKeys 617, pp. 19-29 : 22-24

Taxon classification Animalia Decapoda Porcellanidae

Petrolisthes aegyptiacus Werding & Hiller, 2007 Fig. 4

Petrolisthes aegyptiacus Werding & Hiller, 2007: 5, fig. 4 (type locality: Egypt, Red Sea).

Material.

UF12962, 1 ovigerous female, Mascaréne Islands, La Réunion Island, Saint-Leu, Sec Jaune, rocky slope, basalt blocks, fore reef, under rocks, 10-19 m; UF13075, 1 male, La Réunion Island, Boucan Canot, Paine au Sucre, 10-15 m; UF33079, 1 male, 1 ovigerous female, Red Sea, Saudi Arabia, Thuwal, Al-Fahal reef, 1-37 m; UF36734, 1 specimen (identified from photograph), Red Sea, Saudi Arabia, offshore of Farasan Banks, Shib Radib, fore reef wall and barrier reef flat, 7-9 m; UF15472, 1 male, French Polynesia, Society Islands, Moorea Island, mid N coast, off Sheraton Hotel, outer reef slope, from within rubble; UF15474, 1 female (ovigerous), same data as UF15472.

Description.

Coloration. Fresh specimens from the Indian Ocean and the Central Pacific are white or beige on the anterior part of carapace and chelipeds (Fig. 4). The chelipeds may be entirely white, but usually show vivid red spots towards the fingertips. A row of small, purple spots may border the outer edge of carpus and manus. The front of the carapace may be fringed with some irregular, purple-brown spots, while a larger purple spot delimits the infra-ocular edge. The metabranchial regions bear a large, semi-lunar red blotch that extends towards the basal parts of the walking legs. The walking legs show a ring-like pattern. The surface of legs can be dark-purple or red with white marks, one of them on the distal margin of the merus, one at half distance of the propodus, and another near the articulation with the dactylus.

The red marks of the posterior part of the carapace extend to the lateral part of the segments of the abdomen that are visible from dorsal view. The median part of the first two or three segments of the abdomen is beige, interrupted by irregular red spots. The remaining posterior segments of the abdomen are entirely purplish. The whitish and reddish color, typical of Petrolisthes aegyptiacus , suggests a camouflaging strategy, as the color of the substrate inhabited by the species is usually spotted with red Foraminifera ( Homotrema Hickson, 1911).

Distribution. Previously only known from the Red Sea and the Mascaréne Islands in the southwestern Indian Ocean, and the Society and Line Islands in the Central Pacific Ocean (for the occurrence in the Pacific, see discussion below).