Moreiradromia antillensis ( Stimpson, 1858 )

TAVARES, MARCOS & MENDONÇA, JOEL BRAGA DE JR., 2022, Brachyuran crabs (Crustacea, Decapoda) from the remote oceanic Archipelago Trindade and Martin Vaz, South Atlantic Ocean, Zootaxa 5146 (1), pp. 1-129 : 17-18

Moreiradromia antillensis ( Stimpson, 1858)

( Figs. 7A–C , 8A–F )

Dromidia antillensis Stimpson, 1858: 225 .

Evius ruber Moreira, 1912: 322 , figs. 1, 2 [Type locality: Brazil] [see Guinot & Tavares, 2003: 84].

Trindade specimens. 1 female ( MZUSP 41181 ), off Espírito Santo, Trindade Island, Ponta do Monumento , 20º30’10.3’’S, 29º20’36.1’’W, J.B. Mendonça coll., 3.vii. 2015, 23 m . 1 male ( MZUSP 33350 ), ibidem, Enseada dos Portugueses, Farol , 20º29’52.3’’S, 29º19’15.6’’W, J.B. Mendonça coll., 8.iv.2014, 13.2 m . 1 juvenile female ( MZUSP 40359 ), ibidem, Ponta da Calheta , 20º30’18.7’’S, 29º18’31.6’’W, J.B. Mendonça coll., 30.iv.2014, 15.6 m .

Size of largest male: cl 6.9 mm, cw 6.5 mm; largest female: cl 5.9 mm, cw 6.0 mm.

Comparative material examined. Moreiradromia antillensis : United States: 1 male, 2 females ( USNM 101383), Gulf coast of Florida, west of Anclote Keys, R/V “Silver Bay ”, stn 54, 28°09’00.0”S, 83°49’48.0”W, 37 m. Brazil : Bahia: 1 male ( MZUSP 41232 ), Minerva Bank, 17º03.108’S, 37º37.216’W, J. Coltro coll., 12.viii.2012, 69 m. Espírito Santo : 1 male ( MZUSP 41183 ), Vitória – Trindade Seamount Chain, R /V “Marion Dufresne”, TAAF MD55/ Brésil Expedition, Vitória Bank, stn 10 CP23, 20º43.1’S, 37º50.1’W, 13.v.1987, 52 m. 1 female ( MZUSP 41221 ), ibidem, Columbia Bank , stn 30 DC50, 20º44.2’S, 31º49.9’W, 19.v.1987, calcareous sand and stones, 95–120 m. 1 juvenile (MZUSP 41228), REVIZEE Expedition, off the coast of Linhares, PS/V “Astro Garoupa”, stn 28C, 19º48.47’S, 37º56.33’W, 31.x.1997, 54 m. 1 male (MZUSP 41230) , ibidem, off the coast of São Mateus, H/V “Antares”, stn D32, 18º52’S, 39º35’W, 28.ii.1996, 52 m. 1 male, 2 females ( MZUSP 41227 ), ibidem, off the coast of Guarapari , stn 35C, 20º52.00’S, 40º10.00’W, 3.xi.1997, 55 m. Rio de Janeiro : 1 male ( MZUSP 41222 ), ibidem, off the coast of São João da Barra, stn 6 DC15, 21º37.1’S, 40º18.1’W, 11.v.1987, 37 m. 1 female ( MZUSP 11919 ), Bacia de Campos , no further details. 3 males, 1 female ( MZUSP 41224 ), REVIZEE Expedition, off the coast of Cabo Frio, H /V “Antares”, stn D3, 22º52.97’S, 41º9.24’W, M. Tavares coll., 23.ii.1996, 80 m. 1 ovigerous female ( MZUSP 41231 ), REVIZEE Expedition, off the coast of Cabo Frio, H/V “Antares”, stn D1, 22º48.92’S, 41º9.33’W, M. Tavares coll., 23.ii.1996, 69 m. 1 male ( MZUSP 41229 ), ibidem, off the coast of Maca , stn D7, 22º19’S, 40º50’W, M. Tavares coll., 24.ii.1996, 60 m. 1 female ( MZUSP 41223 ), Niterói , Itaipú Lagoon, channel, J.B. Mendonça coll., 2.v.2001, around 1.5 m. 1 male, 2 females ( MZUSP 17914 ), 6 males, 12 females (4 ovigerous, 2 juveniles), ( MZUSP 41225 ), Baía da Ilha Grande , i.2007 .

Distribution. Bermuda, North Carolina, Bahamas, Gulf of Mexico, Honduras, Antilles, Cuba, Colombia, Venezuela, Suriname, Guianas, and Brazil (Amapá to Rio Grande do Sul, including Fernando de Noronha) ( Alves et al. 2012b, and references therein). Central Atlantic: Ascension and Saint Helena ( Manning & Chace, 1990). This is the first record of M. antillensis from the Minerva Bank (off the coast of Bahia), Vitória–Trindade Seamount Chain (Vitória and Columbia banks), and Trindade Island.

Ecological notes. Although not rare, little is known about the biology of Moreiradromia antillensis . This species inhabits hard bottoms, broken shells beds, loose rubbles, calcareous sand and stones, between 1 and 330 m. The larval development goes through six zoeal stages and a megalopa in laboratory conditions ( Rice & Provenzano 1966). Bright red megalopae were seen forming a swarm during the pelagic phase (Arraial do Cabo, Rio de Janeiro. M. Tavares pers. obs.). Juveniles and adults hold sponges and, more rarely, ascidians and anthozoans on the dorsal surface of the carapace ( Rathbun 1937; Lavaleye & Hartog 1995; Padua et al. 2019). The very pilose body and carapace convexity help the crab to hold sponges and other materials firmly against the dorsal body surface ( Fig. 7A–C ).

Remarks. Juvenile males and females of Dromia erythropus and M. antillensis are commonly collected together during field studies and are frequently confused with each other due to superficial morphological similarities. Juveniles of both sexes of M. antillensis can be recognized on the basis of the distal end of the merus of P5, which extends to (or close to) the branchial spine of the carapace (vs P5 merus falling much shorter that spine in juveniles of D. erythropus ), and in having the carapace usually longer than wide with the posterior margins subparallel (vs carapace wider than long with margins converging posteriorly in D. erythropus ).

Juvenile females of M. antillensis (cw 5.4 mm) are readily recognized in that the thoracic sternal suture 7/8 extends well beyond the gonopore on the coxa of P3 ( Fig. 8A, B ). The suture 7/8 continues to extend forward with growth ( Fig. 8C, D ), so that in mature females the spermathecal openings at the distal end of the suture 7/8 are positioned at the level of P1 ( Fig. 8E, F ) ( Tavares & Franco 2004; Guinot et al. 2013). Contrary, in juvenile females of D. erythropus the thoracic sternal suture 7/8 extends forwards to the level of the gonopore on the coxa of P3 (even in a female at cw 20 mm, e.g. MZUSP 33351); in large ovigerous females (e.g. cw 73 mm, MZUSP 16990) the sternal suture 7/8 extends a little beyond the gonopore on the coxa of P3, but well before the coxa of P2.

Males of M. antillensis , both juveniles (e.g. cl 7 mm, cw 6.2 mm, MZUSP 41224) and adults (e.g. cl 32 mm, cw 30 mm, MZUSP 17914) have paired, uniramous vestigial pleopods on somites 3–5, showing as tiny, membranous buds. The uropods, showing dorsally as small plates in males do not play a role in the pleonal holding system (see also Guinot & Tavares 2003: 83, fig. 14B). The pleon is held folded ventrally by a tubercle on the base of the P2 coxa that overhangs the pleonal somite 6.

Figures

FIGURE 7. A–C, Moreiradromia antillensis (Stimpson, 1858), scanning electron micrographs. A–C, Female, cw 8.8 mm (MZUSP 5905). Note in (A) very pilose carapace and appendages, which help the crab to hold sponges and other materials firmly against the dorsal body surface. B, Detail of the antennule and antenna. C, Detail of the first article of antenna much wider than long, beaked medially. Scales: A, 1 mm. B, 0.5 mm. C, 0.1 mm.

FIGURE 8. A–F, Moreiradromia antillensis (Stimpson, 1858), scanning electron micrographs of the thoracic sternum. A, B, immature female, cw 5.4 mm (MZUSP 11919). C, D, immature female, cw 8.4 mm (MZUSP 6058). E, F, mature female, cw 8.8 mm (MZUSP 5905). B, D, F, Details of A, C, E, respectively. Note in (A–F) thoracic suture 7/8 extending well beyong the gonopore on the coxa of the third pereopod (CxP3) and continuing to extend forward with growth. The gonopores (A–C) and the spemarthecal openings at the distal end of the thoracic suture 7/8 (B, D, black arrows) are closed in the immature female (A–D) and open in the mature female (E, F, black arrow). In (F) the black arrow also shows the sperm plaque around the spermathecal aperture. Scales: A, C, E, 1 mm. B, D, F, 0.3 mm.