Megalobrachium soriatum ( Say, 1818 )

Ferreira, Luciane Augusto De Azevedo & Anker, Arthur, 2021, An annotated and illustrated checklist of the porcelain crabs of Panama (Decapoda: Anomura), Zootaxa 5045 (1), pp. 1-154 : 36

Megalobrachium soriatum ( Say, 1818)

( Fig. 15 )

Porcellana soriata Say 1818: 456 . Porcellanopsis soriata . — Chace 1942: 100. Megalobrachium soriatum . — Haig 1960: 229; Gore & Abele 1976: 17, fig. 3 (upper 2 figures); Werding 1977: 185, fig. 7; Williams 1984: 240, fig. 175; Rodríguez et al. 2005: 551; Vargas & Cortés 2006: 462; Rodríguez et al. 2006: 154; Poupin &

Lemaitre 2014: 9, fig. 2C; Ferreira & Melo 2016: 177, fig. 1C; Poupin 2018: 147; Hiller & Lessios 2019: 414, fig. 1k;

Mendonça et al. 2019: 308, fig. 3A; Mantelatto et al. 2021: 567. (?) Megalobrachium walteri Rodrigues da Costa 1964: 565 .

Material examined. Panama [Caribbean]: 1 male, cl 3.5, cw 3.5 ( FLMNH UF 57123 ), Bocas del Toro , Isla Bastimentos , 9°20’37.9”N, 82°12’24.3”W, depth less than 2 m, in dead coral, leg. P.P.G. Pachelle, 29.03.2019 (fcn PP 19-116). Extra-limital material . USA [Florida]: 1 male, cl cw indet. ( FLMNH UF 19581 ), Florida Bay north of Florida Keys , R / V Bellows sta. 7, 81°53.162’W, 24°47.342’N, otter trawl over spongy bottom, 16 m, leg. A. Anker et al., 07.06.2009 (fcn KEYS-142) .

Previous records from Panama. Gore & Abele (1976); Rodríguez et al. (2005).

Distribution. West Atlantic: USA (Texas to Florida and North Carolina), Mexico, Costa Rica, Panama (Bocas del Toro, Punta Galeta, Bahía de Caledonia), Colombia, Puerto Rico, E Lesser Antilles, Venezuela and Brazil from Maranhão to São Paulo ( Gore & Abele 1976; Rodríguez et al. 2005, 2006; Poupin & Lemaitre 2014; Ferreira & Melo 2016; Mendonça et al. 2019; Mantelatto et al. 2021; however, see below).

Ecology. Intertidal and subtidal, known depth range: 0–111 m; under rocks, within corals, sponges and calcareous algae, sometimes associated with the bryozoan Schizoporella unicornis (Johnston) ( Gore & Abele 1976; Alves et al. 2013; Ferreira & Melo 2016).

Remarks. Megalobrachium soriatum is closely related to the eastern Pacific M. tuberculipes ( Lockington, 1878) ( Gore & Abele 1976; see also Hiller & Lessios 2019). Gore & Abele (1976) distinguished the two species based on a smoother carapace in M. soriatum ; the frontal and post-frontal lobes poorly developed (sometimes not distinguishable) in M. soriatum ; and the protogastric region more coalesced, with the lobes being more shallow and more rounded in M. soriatum . According to Werding (1977), the colouration of M. soriatum varies from white to beige, with the mid-line of the carapace usually presenting a broad longitudinal pink band, as in our specimen from Bocas del Toro ( Fig. 15 ; see also Hiller & Lessios 2019). The deep molecular divergence between the populations from the Caribbean Sea + Brazil and Florida indicates that M. soriatum is composed of at least two cryptic or pseudocryptic species (Hiller & Lessios 2019). Therefore, the taxonomic status of M. walteri from Brazil ( Rodrigues da Costa 1964), which is currently considered as a junior synonym of M. soriatum , will need a reassessment.

Figures

FIGURE 15. Megalobrachium soriatum (Say, 1818): A, male (cl 3.5 mm, cw 3.5 mm) from Bocas del Toro, Panama (FLMNH UF 57123), dorsal view; B, extra-limital specimen, male (cl cw indet.) from Florida Bay, USA (FLMNH UF 19581), dorsal view, P3 missing on left side [photographs by AA].