[Crustacea • 2016] Serenotheres janus • A New Species of Pea Crab of the Genus Serenotheres Ahyong & Ng, 2005 (Brachyura, Pinnotheridae) from the Date Mussel Leiosolenus Carpenter, 1857 (Mollusca, Bivalvia, Mytilidae, Lithophaginae) from the Solomon Islands

Serenotheres janus 

Ng & Meyer, 2016  
DOI:  10.3897/zookeys.623.10272 

Abstract

The pea crab genus Serenotheres Ahyong & Ng, 2005 (Pinnotheridae) is currently only represented by one species, S. besutensis (Serène, 1967). A new species is now assigned to this genus, described from a date mussel Leiosolenus obesus Carpenter, 1857 (Mollusca: Bivalvia: Mytilidae: Lithophaginae) collected in the Solomon Islands. Serenotheres janus sp. n. differs from S. besutensis in possessing a conspicuously broader carapace, with the lateral margins of the dorsal lamellum distinctly produced and the posterolateral part deeply concave, the dorsal lamellum being highest at the median cleft, the rostrum is relatively more prominent, the surfaces of the anterolateral margin and hepatic region are less prominently pitted and eroded, the ischiomerus of the third maxilliped is relatively more rectangular, and the P2 merus is proportionately longer.

Keywords: Pinnotheridae, taxonomy, symbiotic crab, new species, symbiotic crab, Serenotheres janus, Solomon Islands

Figure 1. Colour in life. Serenotheres janus sp. n., holotype ♀ (8.9 × 7.9 mm) (USNM).
 A in situ in host date mussel, Leiosolenus obesus B dorsal view C ventral view.

  Photographs courtesy of Zachariah Kobrinsky and David Liittschwager.
 DOI:  10.3897/zookeys.623.10272 

Systematics

Family Pinnotheridae De Haan, 1833

Genus Serenotheres Ahyong & Ng, 2005

Serenotheres janus sp. n.

http://zoobank.org/FD849337-EB57-46F6-965D-8CECBADECD5F

 Type material: Holotype ♀ (8.9 × 7.9 mm) (USNM 1421642), in Leiosolenus obesus (Philippi, 1847) (Mollusca: Bivalvia: Mytilidae: Lithophaginae), from Njari Island, New Georgia, Solomon Islands, station SOLOM_026; 8.01374°S, 156.75649°E, coll. C. Meyer, 9 October, 2014.

Diagnosis: Carapace distinctly pentagonal; lateral margins of dorsal carapace lamellum distinctly produced with posterolateral part deeply concave, highest at median cleft with 2 halves sloping gently outwards in direct frontal view; rostrum distinct with surface above antennular fossa prominently concave; surfaces of anterolateral margin and hepatic region less prominently pitted, eroded; MXP3 ischiomerus relatively more rectangular; P2 merus relatively long.

Etymology: The species is named after Janus, the ancient two-faced Roman god, alluding to the unusual two parts of the carapace when viewed dorsally. The name is used as a noun in apposition.

 Peter K. L. Ng and Christoph Meyer. 2016. A New Species of Pea Crab of the Genus Serenotheres Ahyong & Ng, 2005 (Crustacea, Brachyura, Pinnotheridae) from the Date Mussel Leiosolenus Carpenter, 1857 (Mollusca, Bivalvia, Mytilidae, Lithophaginae) from the Solomon Islands.
ZooKeys. 623: 31-41. DOI:  10.3897/zookeys.623.10272