Petrolisthes paulayi, Hiller, Alexandra & Werding, Bernd, 2016

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 : 20-22

Taxon classification Animalia Decapoda Porcellanidae

Petrolisthes paulayi sp. n. Figs 1, 2, 3

Material.

Holotype: UF43955, male, Line Islands, Palmyra Atoll, N side of Atoll, outer reef slope, from dead Pocillopora cf. verrucosa head, 10.6 m.

Paratypes: UF43956, 1 male, same collection data as holotype; UF10692, 1 male (with bopyrid), 1 ovigerous female, Kiribati, Line Islands, Tabuaeran Atoll, SSW side of Atoll, outer reef slope, under rock, 10-23 m; UF10693, 2 females (1 ovigerous), Kiribati, Line Islands, Tabuaeran Atoll, outer reef slope, from Halimeda sample, 10-23 m; UF10711, 1 female, Line Islands, Tabuaeran Atoll, W side, S of Main Reef Pass, outer reef slope, from dead Pocillopora cf. verrucosa head, 10-15 m; UF15894, 1 male, (photographed specimen, Fig. 3), French Polynesia, Society Islands, Moorea, Haapiti, just NW of Matauvau Pass, outer reef slope, 15-23 m.

Other material.

UF10588, 12 specimens, Line Islands, Palmyra Atoll, Line, N side of Atoll, outer reef slope, dead Pocillopora cf. verrucosa head, 10.6 m; UF41926, 1 male, Kiribati, Line Islands, Starbuck, Starbuck Island, dead Pocillopora , 12 m; UF41916, 1 female, Kiribati, Line Islands, Starbuck, Starbuck Island, 12 m; UF40590, 2 males, 1 ovigerous female, Kiribati, Line Islands, Starbuck, Starbuck Island, 7 m; UF41980, 4 males, 4 females (3 ovigerous), Kiribati, Line Islands, Vostok, Vostok Island, dead Pocillopora , 10 m.

Measurements.

Male holotype: carapace length 4.5 mm; carapace width 4.2 mm.

Largest male paratype: carapace length 4.8 mm; carapace width 4.5 mm.

Largest female paratype: carapace length 4.5 mm; carapace width 4.3 mm.

Description.

Carapace (Figs 1, 3) slightly longer than broad. Front (Fig. 2a) trilobate, markedly produced beyond eyes, median lobe broadest, rounded, overreaching the slender, forwardly produced lateral lobes; frontal borders finely serrated. Orbits deeply rounded, inner margin armed with a small supraorbital spine, followed mostly by a second tubercle-like elevation that is sometimes armed with a spine; infraorbital angles forming an acute edge. Lateral margins (Fig. 2b) with a prominent epibranchial spine on epibranchial edge, and followed by a second smaller spine; two strong spines on mesobranchial margin. Carapace with few transverse, piliferous striations on protogastric ridge and on gastric region; epibranchial region rugose.

Third thoracic sternite (Fig. 2c) anteriorly trilobate, median lobe broad, lateral lobes slender, exceeding median lobe.

Telson (Fig. 2d) with seven plates.

First movable segment of antenna with an anterodistal slender projection bearing a narrow tooth. Basal segments of antennular peduncle bearing acute, irregular spines on anterior margin.

Chelipeds (Figs 1, 3) subequal, robust, dorsal surface somewhat convex, covered with interrupted scale-like ridges, granulated on ventral side. Merus with a large, serrate-edged tooth on anterior margin; carpus about 2.5 times as long as broad, with 4 rounded, serrated teeth on anterior margin, the proximal ones spine-tipped in some specimens; anterodistal edge with an additional blunt tooth; posterior margin with scale-like granules forming a row of 5 to 6 curved, upright spines, distally increasing in size. Manus moderately broad, posterior margin serrated but without spines, fringed with an irregular set of stiff and feathered setae; gape of fingers without distinct setation.

Walking legs (WL; Figs 1, 3) relatively robust, irregularly covered with scattered, simple and feathered setae of different size; merus of WL1 without spur-like spine on ventral, mid-distal margin; merus of WL1 and 2 with continuous transverse ridges; merus of WL3 without such ridges; merus of all WL with row of spines on anterior margin, distributed as follows: WL1 and 3: 5, WL2: 4-5. Merus of WL1 and WL2 with posterodistal spine; Dorsodistal edge of carpus in WL1 produced into a sharp spine. Propodus of all WL with 1 or 2 movable spines in addition to the terminal spine-triplet on posterior margin. Dactylus of all WL with 4 movable spines on posterior margin.

Coloration (Fig. 3). The carapace has a yellow-orange background with a white, reticulate pattern in the posterior half. The white markings on the gastric region fuse into an irregular, transversal stripe towards the epibranchial edges. The inverted figure of a butterfly is depicted by a broad, white, curved band connecting the hepatic margins on both sides, two semicircular white spots mesial to the orbits, and another backwardly curved white band behind the front. The reticulate pattern continues to the anterior part of the abdomen and the proximal parts of the walking legs, covering half to most of the merus. This pattern is then replaced by a dark purple band that increases in size, and is followed by a narrower white band bordering the articulation with the purple-colored carpus. Dactylus is also purple. White bands on both ends of the propodus give the walking legs a uniform, ring-like aspect. The chelipeds exhibit a similar ground color that becomes darker distally, with white marks forming irregular rows of round spots on carpus and manus.

Ecology.

The specimens examined were collected in depths between 7 and 23 m, on the outer reef slope, from Halimeda and dead Pocillopora . Further collections will probably confirm that Petrolisthes paulayi sp. n. inhabits other exposed coral environments of the tropical western Pacific.

Distribution.

The new species is known only from the Line and Society Islands in the Central Pacific.

Etymology.

The new species is named after Gustav Paulay for supporting this and other studies on Porcellanidae , and for entrusting us with the porcellanid collection of the Florida Museum of Natural History.

Remarks.

Petrolisthes paulayi sp. n. can be be easily distinguished from other Petrolisthes species of the Indo-West Pacific by its unique color pattern, and by the combination of the following characters on the carapace: two mesobranchial spines, two epibranchial spines and a conspicuous trilobate front. The later character is known only in Petrolisthes elegans Haig, 1981, which lacks mesobranchial spines, and only bears one epibranchial spine.