Opecarcinus hypostegus ( Shaw & Hopkins, 1977 )

In, First Published, 2022, Brachyuran crabs (Crustacea, Decapoda) from the remote oceanic Archipelago Trindade and Martin Vaz, South Atlantic Ocean, Zootaxa 5146, pp. 1-129 : 81

Opecarcinus hypostegus ( Shaw & Hopkins, 1977)

( Fig. 44A, D )

Pseudocryptochirus hypostegus Shaw & Hopkins, 1977: 179 .

Trindade and Martin Vaz specimens. None.

Vitória–Trindade Seamount Chain material. Brazil: Espírito Santo: 1 male ( MZUSP 40810 ), REVIZEE Expedition , Vitória–Trindade Seamount Chain , Bank Jaseur, PS /V “Astro Garoupa”, stn 23C, 20°29’00’’S, 36°06’00”W, 8.xi.1997, 60 m. 1 male ( MZUSP 40811 ), Vitória – Trindade Seamount Chain, R /V “Marion Dufresne”, TAAF MD55/ Brésil Expedition, Dogaressa Bank, stn 25 DC43, 20°51’S, 33°45’W, 17.v.1987, 63 m.

Comparative material examined. Opecarcinus hypostegus : United States: Florida : 1 ovigerous female ( USNM 231681 ), west Laboratory Dock, 2437’N, 8257’W, 14.viii.1930, 6.1 m .

Distribution. Western Atlantic: Mexico, Gulf of Mexico, Florida, Jamaica, Puerto Rico, and Brazil (Rio Grande do Norte, Pernambuco, and Alagoas) ( Kropp & Manning 1987; Johnsson et al. 2006). Opecarcinus hypostegus is here recorded from much farther south in the Vitória–Trindade Seamount Chain (Jaseur and Dogaressa banks, from 60 m and 63 m, respectively). Central Atlantic: Ascension Island ( Kropp & Manning 1987).

Ecological notes. Opecarcinus hypostegus is an obligate symbiont of scleractinean corals and is known to live in association with several agariciids, such as Agaricia spp. and Helioseris cucullata (Ellis & Solander) , but can also be found on siderastreids ( Siderastrea spp. ) ( Kropp & Manning 1987; Johnsson et al. 2006; Moorsel & Meij 2018; García-Hernández et al. 2020). Kropp and Manning (1987) tentatively assigned to O. hypostegus the specimens found on agariciid corals from northeastern Brazil, previously identified as Troglocarcinus corallicola by Coelho (1966).

Remarks. Opecarcinus can be readily distinguished from Kroppcarcinus and Troglocarcinus (character states for Kroppcarcinus and Troglocarcinus between brackets) by having the surface of the thoracic sternite of P1 tuberculate anteriorly in the females ( Fig. 44A ) (vs anterior margin of the P1 sternite tuberculate in Kroppcarcinus ; P1 sternite non tuberculate in Troglocarcinus ) ( Fig. 44B, C ) and by several differences in the first male gonopods as figured ( Fig. 44D–F ).

In O. hypostegus , the coxae of P2–P5 are provided with a well-developed anterior lobe in the female, somewhat less developed in the P2 coxa.

Figures

FIGURE 44. A, D, Opecarcinus hypostegus (Shaw & Hopkins, 1977), after Kropp & Manning (1987: 11, fig. 5c; 12, fig. 6f, respectively). B, E, Kroppcarcinus siderastreicola Badaró, Neves, Castro & Johnsson, 2012, after Badaro et al. (2012: 522, fig. 3A; 523, fig. 4C, respectively). C, F, G, Troglocarcinus corallicola Verrill, 1908. C, F, after Kropp & Manning (1987: 16, fig. 7d; 17, fig. 8d, respectively). G, Female, cl 4.1 mm, cw 3 mm (USNM 1207444) paratype of T. hirsutus Badaró et al., 2012 (junior synonym of T. corallicola). A–C, Female cheliped sternite. D–F, First male gonopod. G, Semi-diagrammatic outline of the posterior region of the body, dorsal view. Note in (B) anterior margin of the sternite tuberculate (arrow) and in (G) the coxa of the fifth pereopod provided with a well-developed anterior lobe (arrow).