Family TRAPEZIIDAE Miers, 1886

<em>Trapezia cymodoce</em> [P. Davie 2002: 493]

Trapezia cymodoce [P. Davie 2002: 493]

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Family TRAPEZIIDAE Miers, 1886

Compiler and date details

May 2012 - Peter Davie, Queensland Museum, Brisbane

Trapeziinae Miers, E.J. 1886. Report on the Brachyura collected by H.M.S. Challenger during the Years 1873–76. Report on the Scientific Results of the Voyage of H.M.S. Challenger 1873–1876, Zoology 17(49): i-xlix 1-362 pls 1-29 [163].
Trapezides Milne Edwards, A. 1862. Monographie des Crustacés fossiles de la famille des Canceriens. Annales des Sciences Naturelles, Paris Zool. 4 18: 31-85 pls 1-10 [40] [French vernacular].
Trapeziden Nauck, E. 1880. Das Kaugerüst der Brachyuren. Zeitschrift für Wissenschaftliche Zoologie 34: 1-69 pl. 1 [64] [German vernacular].
Calocarcinini Števčić, Z. 2005. The reclassification of Brachyuran Crabs (Crustacea: Decapoda: Brachyura). Natura Croatica 14(1): 1–159.
Sphaenomeridini Števčić, Z. 2005. The reclassification of Brachyuran Crabs (Crustacea: Decapoda: Brachyura). Natura Croatica 14(1): 1–159.
Philippicarcinini Števčić, Z. 2005. The reclassification of Brachyuran Crabs (Crustacea: Decapoda: Brachyura). Natura Croatica 14(1): 1–159.

Introduction

Trapeziid crabs are obligate associates (symbionts) of cnidarians. The best known are species of Trapezia that live in branching corals of the family Pocilloporidae (Pocillopora, Seriatopora and Stylophora species). Quadrella species are recorded more rarely; they live on alcyonaceans, antipatharians, and ahermatypic scleractinian corals. Trapeziidae are mostly restricted to the Indo-west Pacific region, although a few species also reach the tropical eastern Pacific.

The taxonomy of many of the common trapeziids has been in a state of confusion for many years because morphological differences between species are relatively minor. Identification is best based on colour differences that are often lost in spirit-preserved material. Important modern works are those of Patton (1966), McNeill (1968), Serène (1984), Galil & Lewinsohn (1985), Galil (1988), and Castro (1997, 1999). Ecological studies of Australian trapeziids include those of Patton (1974, 1994), Lassig (1977), Austin et al. (1980) and Abele (1984).

Serène (1984) considered the Trapeziidae to comprise two subfamilies: Trapeziinae and Domeciinae. The latter, represented in Australia by the genus Domecia, is here considered a family in its own right. Most recently Tetralia and Tetraloides that live on Acropora coral species, were recognised as belonging to a separate morphologically convergent lineage, and both genera were separated off into a separate family, the Tetraliidae Castro, Ng & Ahyong, 2004, under the Superfamily Trapezioidea.

Diagnosis

Carapace more or less flattened, subquadrilateral, pentagonal or transversely oval; dorsal surface smooth or finely granular, regions not marked or sometimes indicated feebly; setae absent. Front almost straight; four lobes or teeth or bilobed; sometimes finely denticulate. Basal antennal joint slender. Antennules folding transversely. Eyes moderately large, exposed, not well protected by orbits. Crests of endostome defining efferent channels well developed. Third maxilliped with merus shorter than ischium, but not much broader than long. Second maxilliped with endopod composed of four distinct segments (merus, carpus, propodus, dactylus). Chelipeds long or very long, meri projecting beyond carapace when folded; slightly to moderately unequal, surface of palm smooth or finely granular. Walking legs with a dactylo-propodal articulation formed by a rounded prolongation of propodal lateral margin sliding against and beneath a projecting button situated proximally on lateral margin of dactylus. Male abdomen 5-segmented, segments 3–5 fused but sutures sometimes visible. Male genital openings coxal; female openings sternal.