Domecia acanthophora (Desbonne in Desbonne & Schramm, 1867)

(Fig. 30A, B)

Neleus acanthophorus Desbonne in Desbonne & Schramm, 1867: 35 [Type locality: Guadeloupe].

Trindade specimens. 1 ovigerous female (MZUSP 41293), Trindade Island, Parcel das Tartarugas, 20°31’1.4”S, 29°18’00.6”W, J.B. Mendonça coll., 19.vi.2016, tide pool, 0.5–1 m. 1 juvenile male (MZUSP 41407), 1 juvenile female (MZUSP 41302), ibidem, Enseada das Orelhas, 20°29’40.2”S, 29°20’32.9”W, J.B. Mendonça coll., 1.vii.2016, 9.2 m. 1 ovigerous female (MZUSP 39836), ibidem, 1.viii.2015, 8.9 m. 1 juvenile female (MZUSP 41412), ibidem, 13.vii.2015, 16.1 m. 1 female (MZUSP 41063), ibidem, Enseada da Praia do Príncipe, Ilha Sul, 20°31’34.3”S, 29°19’27.9”W, J.B. Mendonça coll., 21.x.2014, 17.8 m. 1 female (MZUSP 41409), ibidem, Ponta da Calheta, 20°31’18.7”S, 29°18’31.6”W, J.B. Mendonça coll., 30.iv.2014, 15.6 m. 1 female (MZUSP 41416), ibidem, Praia da Calheta, 20°30’29.5”S, 29°18’37.0”W, J.B. Mendonça coll., 2.viii.2015, 9.5 m. 1 juvenile (MZUSP 41414), ibidem, Ponta Norte, Crista do Galo, 20°29’14.8”S, 29°20’13.9”W, J.B. Mendonça coll., 21.v.2014, 15 m. 1 male (MZUSP 41417), ibidem, Praia do Lixo, 20°31’29.8”S, 29°19’43.9”W, J.B. Mendonça coll., 15.vii.2013, 17 m.

Size of largest male: cl 3.2 mm, cw 4 mm; largest female: cl 4.5 mm, cw 6 mm.

Comparative material examined. Domecia acanthophora: Brazil: 1 male, 1 female (MZUSP 5463), Paraíba, Tambaú, recife Quebra-Quilha, P. Young coll., 4.i.1983. 1 male (MZUSP 5456), ibidem, Tambaú, recife do Picãozinho, P. Young coll., 20.viii.1982. São Paulo: 1 female (MZUSP 16705), Ilha Vitória, 23°44’04”S, 45°01’35”W, Saco do Pai, D.F.R. Alves et al. coll., x.2004.

Distribution. Western Atlantic: North Carolina, Bermuda, Florida, Gulf of Mexico, Antilles, Caribbean coast of Colombia, Venezuela, and Brazil (Ceará, Paraíba, Pernambuco, Alagoas, and São Paulo). Also known from the Brazilian oceanic Islands (São Pedro and São Paulo Archipelago, Rocas Atoll and Fernando de Noronha) (Rathbun 1930; Holthuis 1980; Rodriguez 1980; Lemaitre 1981; Melo 1996; Álvarez-León 2004; Coelho Filho 2006). This is the first record of D. acanthophora from the Trindade Island. Central Atlantic: Ascension Island (Manning & Chace 1990; De Grave et al. 2017).

Ecological notes. Domecia acanthophora commonly associates with corals (Desbonne in Desbonne & Schramm 1867: 36; Rathbun 1930) but also is found in sponges and non-living substrates such as dead corals, coral rubble, and cobble beaches, between 1 and 146 m (Abele 1976; Keith 1985; Felder et al. 2009; Santos et al. 2012). It has been found associated with several coral species including Meandrina sp. and Porites furcata Lamarck (Rathbun 1930, as D. hispida); Acropora palmata (Lamarck), A. cervicornis (Lamarck), and A. prolifera (Lamarck) (Lemaitre 1981; Álvarez-León 2004); Millepora alcicornis Linnaeus (Garcia et al. 2008); Millepora complanata Lamarck (Hoeksema & García-Hernández 2020); Pocillopora (see Alonso-Dominguez et al. 2022), and occasionally with Oculina arbuscula Agassiz (William et al. 1968). In Puerto Morelos (Mexico), D. acanthophora was far more abundant associated with well-preserved corals than when inhabiting degraded corals (González-Gómez et al. 2018). In Trindade, D. acanthophora was found in tide pools, reefs, caves, and corals. The female MZUSP 41407 was associated with the sponge Agelas sp. The crab produces growth anomalies (crevices, pits and folds) when in association with scleratinean corals (Patton 1967; Hoeksema & García-Hernández 2020). In A. palmata the pits were 2 cm long with thickened, smooth margins, but usually consisted of folds in the coral’s branches when associated with and Millepora complanata (see Hoeksema & García-Hernández 2020). Ovigerous females are commonly found inside these crevices, pits and folds (Lemaitre 1981; Grajal & Laughlin 1984; Álvarez-León 2004), which are supposed to be used not only as “resting places” (Patton 1967) but also as shelters for reproduction and brood care (Grajal & Laughlin 1984). Ovigerous females are known to occur from December to September in various parts of the species geographical range (Williams 1984; Alves et al. 2016). The spiny chelipeds folded against the body close the entrance of the pit (Álvarez-León 2004). Usually, there is only one crab per shelter, very occasionally two crabs (Patton 1967). Domecia acanthophora and clinid fishes occupy vacant pits and crevices formed by previous crabs (Patton & Robertson 1980; Álvarez-León 2004). The food source for D. acanthophora is not known. Small mineral grains and sponge spicules were common in several crab stomachs examined by Patton (1967). He suggested, based on the morphology of the mouthparts and from stomach contents, that D. acanthophora is a suspension feeder and also feed on coral mucus (Patton 1967). Castro (2015) cautioned, however, that the mouthparts of D. acanthophora are not typical of suspension feeders and the ambulatory legs lack the feeding setae adapted for mucus feeding of most other trapezioids. Domecia acanthophora can affect the interaction of the coral Montastraea cavernosa (Linnaeus) with the macroalga Halimeda opuntia by preventing the coral from damaging the alga in laboratory conditions (Nugues et al. 2004). It may also inhibit the development of coral sweeper tentacles in laboratory conditions (Chornesky 1983). Domecia acanthophora is parasitized by the isopod Cancricepon choprae (Nierstrasz & Brender Brandis) (Markham 1979) and is preyed by the fishes Holocentrus rufus (Walbaum), H. vexillarius Poey, and Epinephelus adscensionis (Osbeck) (Williams 1984).

Remarks. Guinot (1964) established D. acanthophora forma africana, a nomenclatural procedure not recognized after 1960 by the ICZN (1999: Article 15.2). Manning & Holthuis (1981: 122) recognized this taxon and assigned subspecific status to it, D. acanthophora africana, whose authorship they clearly attributed to Guinot, viz. D. africana Guinot in Manning & Holthuis, 1981. Ng et al. (2008) assigned full specific status to it without justification.

Guinot (1964) revised Domecia, providing several illustrations of D. acanthophora s.l. based on materials from both sides of the Atlantic, and concluded ...qu’aucune différence spécifique, parmi les caractères qui nous avons indiqués, ne sépare la forme américaine... de la forme africaine.... However, she indicated that ... les petites différences (pilosités, spinulation) séparant nos exemplaires ouest-africains des spécimens est-américains sont sans doutes liées à des conditions écologiques différentes. (see also Forest & Guinot 1966). She further indicated that the West African specimens at hand were distinctly smaller than the eastern Atlantic specimens, for instance. Manning & Holthuis (1990) suggested that the material from Ascension may belong to the “West African form” based on the small size of their specimens. Actually, we know of no morphological evidence to confidently distinguish D. acanthophora from D. africana (Fig. 30A–C). The Trindade specimens are here assigned to D. acanthophora based on the close similarities with the comparative material from the western Atlantic coast.