Aliaporcellana spongicola, Hiller, Alexandra & Werding, Bernd, 2018

Hiller, Alexandra & Werding, Bernd, 2018, On a new commensal species of Aliaporcellana from the western Pacific (Crustacea, Decapoda, Porcellanidae), ZooKeys 780, pp. 1-9 : 1-5

Aliaporcellana spongicola sp. n. Figures 1, 2, 3, 4, 5

Material.

Holotype: female (ovigerous), NMCR 4966, ex UF 43328, Philippines, Oriental Mindoro Province, Mindoro, Puerto Galera, off Pt W of Bayanar Beach, 13.5118°N 120.9088°E, 10-13 m, sand slope, coll. G. Paulay, 02.04.2015, 6.8 × 7.0 mm. Paratypes: 2 females (ovigerous), UF 43328, same collection data as holotype, 7.4 × 7.6 mm, 5.2 × 5.2 mm;1 female (ovigerous), UF 42943, Philippines, Oriental Mindoro Province, Mindoro, Puerto Galera, Batangas Channel, 13.5199°N 120.9604°E, 11 m, lagoon sand slope with sponge, coll. G. Paulay, 12.04.2015, 6.2 × 6.8mm; 2 males, 1 female (ovigerous), RMNH.CRUS.D.57287, Indonesia, SW Sulawesi, Spermonde Archipelago, Bitung, sta. 17, 20 m, from large grey folious sponge, cleaning station, coll. C.H.J.M. Fransen, 30.10.1994, 4.8 × 4.4 mm, 3.3 × 3.0 mm, 5.2 × 4.8 mm.

Description.

Carapace rounded (Figures 1, 2), considerably variable in form and in length-width ratio; larger females with carapace broader than long (ratio <1), smaller individuals with carapace relatively longer than broad (ratio> 1); dorsal surface convex, glossy, with faint, transverse striae on branchial and intestinal regions; cervical grooves gently depressed. Front (Figures 1, 2) broad, slightly produced beyond eyes, weakly trilobate, somewhat deflexed; frontal lobe visible in dorsal view, grooved, overreaching lateral ones. Distal margin of entire front lined with row of rounded, upwardly directed small spines (Figure 3a), the largest on supraocular edges. Outer orbital angles (Figure 2) forming acute, bifid tooth followed by hepatic spine of similar size. Epibranchial margin rounded, produced outwards, marked with epibranchial spine; cervical groove faintly marked. Mesial branchial margins crested, with row of 5 or 6 strong, anteriorly, upwardly directed spines of increasing size posteriorly. Sidewalls entire.

Eyes moderately large (Figures 1, 2, 3a), retracted, ocular peduncles short. First movable segment of antennal peduncle (Figures 2, 3b) with strong, anteriorly curved distal spine, second with smaller, anterodistal, acute protuberance, third one globular. Basal segment of antennular peduncle (Figure 3c) with anterior surface transversely rugose, surrounded with open ring of strong, conical spines. Third maxilliped (Figure 3d) slightly rugose, ischium sub-quadrate with inner lobe, inner margin of merus semi-circular; exopodite long, pyriform, reaching 2/3 of length of merus.

Third thoracic sternite (Figure 3e) broadly elliptic, with triangular, forwardly produced, lateral projections. Telson with 7 plates.

Chelae moderately different in size and form (Figures 2, 4a-c); merus short, dorsal surface faintly rugose, inner margin with strongly projecting, sub-rectangular projection, fringed distally with cockscomb-shaped row of teeth, other large spines on proximal and distal edge of outer margin, one on distal margin; ventral side with two large spines on distal margin. Carpus 1.5 times as long as wide, dorsal surface evenly convex, similarly structured as carapace, with some faint transversal plications; inner margin with 3-5 low or sharply hooked teeth, decreasing in size distally, distal edge rounded. Outer margin with a row of six or seven acute, upwardly directed spines, the last one forming distal edge. Palm slender, surface rounded, similarly structured as carpus, with faint, transverse striae. Smaller chela with outer margin bearing row of approximately ten sharp spines on proximal half, with scattered, long, simple setae; fingers reaching up to half length of chela, dactylus moderately twisted, opening vertically, cutting edges denticulate, without teeth, both fingers with narrow fringe of fine, plumose setae in proximal 2/3 of length. Larger chela somewhat stouter, outer margin with row of spines less developed or disappearing in large specimens, with scattered, long, simple setae, fingers relatively shorter as in smaller chela; dactylus moderately twisted, opening vertically, cutting edges in pollex and dactylus with broad, shallow tooth, gape naked.

Walking legs (Figures 2, 3f, g) stout, merus with some transversal striae, with scattered, long, simple setae, increasing in number towards dactylus; carpus in first and second leg ending dorsodistally in two minute spines, propodus ventrally with 1 movable spine in addition to terminal triplet; dactylus terminating in bifurcate, curved claw.

Coloration. The background color of carapace and extremities is bright orange (hexadecimal color #e86700), overlain with a reticulate bright blue (hexadecimal color #000de8) pattern (Figures 1, 5). A broad, black band crosses the carapace transversely at the level of the hepatic region; it is fringed on both sides by a small, blue line and a broad, orange band. A similar band extends along the outer border of the chelipeds from the carpus to the tip of the pollex. In a number of individuals the blue color prevails over the orange, and the entire crab appears blue.

Ecology.

Aliaporcellana currently consists of six species. Of all species, A. spongicola sp. n. is by far the most strikingly colorful, and has, therefore, become popular among underwater photographers and marine aquarists. Aliaporcellana spongicola sp. n. dwells on large barrel sponges of the genus Xestospongia Laubenfels [family Petrosiidae ; e.g., X. testudinaria (Lamarck 1815)] and on other types of sponges, like the "large, grey foliose sponge", on which the crabs from Sulawesi included in this study, were found. The porcellanid lies in the sponge’s folds, where it is most protected from predators (Figure 5).

Distribution.

The type specimens come from the central Philippines and northern Sulawesi, Indonesia.

Etymology.

The name spongicola (from the Latin word spongia, meaning sponge, and the Latin suffix cola, meaning dwelling) refers to the sponge-dwelling habit of the new species.

Remarks.

Aliaporcellana spongicola sp. n. is considerably variable in the shape of carapace and the degree of spination on body and extremities. As in other porcellanid species, the spines are more defined in smaller specimens. The new species is distinguished from A. pygmaea and A. kikuchii by the lack of acute spines on the dactylus of the smaller cheliped ( Osawa 2007; Dong et al. 2011), and by its smoother surface of carapace and chelipeds ( Lewinsohn 1969; Nakasone and Miyake 1969; Werding and Hiller 2007; Osawa and Chan 2010). Aliaporcellana spongicola sp. n. can be distinguished from A. suluensis , A. telestophila and A. taiwanensis by its regularly denticulated front (Figures 2, 3a), which is smooth in the other species, and by the basis of the antennular peduncle, which is crowned with a ring of spines (Figure 3c) and is at most granulate or faintly serrate in the compared species (see Lewinsohn 1969; Werding and Hiller 2007; Dong et al. 2011 for A. suluensis ; Ng and Goh 1969 for A. telestophila ; Dong et al. 2011 for A. taiwanensis ).