Description of a new genus of Cryptochiridae (Decapoda: Brachyura) associated with <i>Siderastrea</i> (Anthozoa: Scleractinia), with notes on feeding habits

Abstract

SUMMARY: Members of the Cryptochiridae are small gall-crabs that live as obligate symbionts of scleractinian corals. Only two species have so far been recorded in the western Atlantic Ocean. Herein a new Cryptochiridae genus and species is described, and new information is added on the life history of cryptochirids. The new genus is characterized by having the carapace with the lowest deflection angle among the genera, and also shows the following features: thoracic sternite 4 with setules and constriction smaller than half of the width of the basis, anterior margin curved with apical row of granules; third maxilliped with subcircular exopod reaching medially the lateral margin of the ischium; pereiopod 2 with prominent distomesial and anterolateral expansion on the merus, propodus almost twice larger than dactylus; thoracic sternite 7 with complete medial suture, female pleopod 3 uniramous with longitudinal opening. Male first pleopod straight with subdistal curvature of approximately 90°. Individuals belonging to the new genus are found in galls in massive corals although this structure is cited as being characteristic of ramified corals. The long plumose setae of the maxilliped 3 suggest a filter-feeding function, but the toothless chelae suggest that they are used to gather mucus.Keywords: gall crab, associated fauna, coral reef, symbiosis, Cnidaria.RESUMEN: Descripción De un nuevo género De cryptochiriDae (DecapoDa: Brachyura) asociaDo com siDerastrea (anthozoa: scleractinia), con notas soBre los háBitos alimentarios. -Los miembros de la familia Cryptochiridae son pequeños cangrejos agallas que viven como simbiontes obligados en corales escleractiniarios. Sólo dos especies han sido registradas del Océano Atlántico occidental. Se describe un nuevo género y especie de Cryptochiridae asociados con corales de la familia Siderastreidae y se añade información sobre el ciclo de vida de los cryptochíridos. El nuevo género se caracteriza por tener el ángulo de desviación menor entre los géneros, que también muestra las siguientes características: esternón torácico 4 menor que la mitad del ancho del basis y el margen anterior curvo con una hilera de gránulos; tercero maxilípedo con exopodito subcircular, alcanzando el margen medial lateral del isquion; pereiópodo 2 con una prominente expansión distomesial e anterolateral en el mero, propodio casi dos veces más grande que el dáctilo; esternón torácico 7 con una sutura medial completa, pleópodo 3 unirrámeo, con abertura longitudinal. Pleópodo 1 del macho recto con curvature subdistal de alrededos 90°. Los individuos del nuevo género viven en agallas en corales masivos a pesar de que esta estructura es citada como características de corales ramificados. Las largas setas plumosas del maxilipedo 3 sugieren una función filtradora, pero las quelas sin dientes sugieren su uso para colectar moco.

The scleractinian Agaricia undata as a new host for the coral-gall crab Opecarcinus hypostegus at Bonaire, southern Caribbean

“…in the Caribbean, along with the agariciid Helioseris cucullata (Table 1), share the same cryptochirid species, O. hypostegus. In Brazil, O. hypostegus has been reported from Agaricia fragilis and A. agaricites (Johnsson et al 2006;Badaró et al 2012;Santana et al 2016). Older records of O. hypostegus from non-agariciid hosts (e.g.…”

“…Older records of O. hypostegus from non-agariciid hosts (e.g. Scott 1985;Nogueira 2003) are doubtful and probably concern misidentified crabs of recently discovered species (Badaró et al 2012;Canário et al 2015;Hoeksema et al 2017c).…”

“…Photographs of a male and a female collected from the Brazilian endemic scleractinian Siderastrea stellata Verrill, 1868 (Johnsson et al 2006: Fig. 3), probably concern Kroppcarcinus siderastreicola Badaró et al, 2012, a common species in Brazil (Badaró et al 2012;Nogueira et al 2014), which also occurs in the Caribbean (van der Meij et al 2014b). Therefore, in order to obtain a reliable identification for the crab associated with Agaricia undata in Bonaire, DNA barcoding was applied.…”