Ranilia constricta

Ranilia constricta (A. Milne-Edwards, 1880)

Raninops constricta A. Milne-Edwards, 1880: 35 [

Type locality: near Sombrero Island, 86 m].

Ranilia guinotae Melo & Campos Junior, 1994: 69 [

Type locality: Santos, São Paulo, from the stomach of the sand perch Diplectrum formosum (Linnaeus)].

Trindade and Martin Vaz specimens. 1 female (MZUSP 41564), R/V “Marion Dufresne”, TAAF MD55/Brésil Expedition, Trindade Island, stn 35 DC59, 20°30’S, 29°18’W, 22.v.1987, sand, 60 m. 8 juvenile females (MZUSP 41477), R/V “Marion Dufresne”, TAAF MD55/Brésil Expedition, Martin Vaz Archipelago, stn 32 DC52, 20° 29’S, 28°51’W, 20.v.1987, sand, 64– 80 m.

Size of largest female: cl 10.8 mm, cw 16 mm.

Comparative material examined. Ranilia constricta: United States: 1 female (USNM 169699), R/V “Triton”, Gulf of Mexico, Florida, Monroe County, off Sombrero Light, 6.vi.1950, 91–110 m. Martinique: 1 female (MZUSP 17319), IGMAR 3 Expedition, stn 419, 14°41.73’N, 60°50.05’W, IFREMER coll. 14.ix.1994, dredge [J. Poupin don.]. Brazil: Espírito Santo: 1male, 1 female juvenile (MZUSP 41566), R/V “Marion Dufresne”, TAAF MD55/ Brésil Expedition, off the coast of Linhares, stn 52 CB90, 19°33’S, 39°34’W, 29.v.1987, mud and dead shells, 34 m. 3 juvenile females (MZUSP 41478), ibidem, Vitória–Trindade Seamount Chain, Columbia Bank, stn 27 DC47, 20°41’S, 32°12.85’W, 19.v.1987, 94–105 m. 10 females (8 juveniles) (MZUSP 41563), ibidem, off the coast of Guarapari, stn 30 DC50, 20°44’S, 39°49’W, 19.v.1987, calcareous sand and stones, 95 m. Rio de Janeiro: 1 male, 2 females (1 juvenile) (MZUSP 41565), ibidem, off the coast of Arraial do Cabo, stn 60 CB101, 22°58’S, 42°06’W, 1.vi.1987, mud, 50 m. 1 male, 1 female juveniles (MZUSP 41567), stn 60 CB100, 22°59’S, 42°06’W, 1.vi.1987, mud, 33–45 m. Ranilia guinotae: Brazil: holotype male badly damaged (MZUSP 10932), 1 male paratype badly damaged (MZUSP 11106) [junior synonym of R. constricta], Santos, São Paulo, from the stomach of the sand perch Diplectrum formosum (Linnaeus) [no further details informed].

Distribution. Amphi-Atlantic. Western Atlantic: North Carolina, Gulf of Mexico, Antilles, Venezuela, and Brazil (Amapá to Rio Grande do Sul) (Manning & Holthuis 1981; Melo 1996; Felder et al. 2009). Ranilia constricta is also known from the Pliocene of Curaçao (Luque et al. 2017) and the late Pleistocene of Calabria, Italy (Vazzana 2008; Garassino et al. 2014). This is the first record of R. constricta from Trindade and Martin Vaz and the Vitória–Trindade Seamount Chain (Columbia Bank). Central Atlantic: Ascension Island and perhaps Saint Helena (Manning & Chace 1990; De Grave et al. 2017). Eastern Atlantic: west African coast from Cape Verde Islands to Gabon (Manning & Holthuis 1981; González 2018).

Ecological notes. This species has been recorded from the inner shelf from 20 m to the upper slope down to 481 m in soft bottoms including sand, calcareous sand and rubble, and mud with dead shells. It is preyed by the sand perch Diplectrum formosum. Swarming of a raninid megalopa, possibly referable to Ranilia, were seen at St. Lucia and Barbados (Chace & Barnish 1976; Kidd & Rice 1986). Megalopae attributable to Ranilia have been found in the stomachs of albacores in the Gulf of Guinea (Monod 1965).

Remarks. The male holotype and paratype of Ranilia guinotae, both obtained from the stomach of the sand perch Diplectrum formosum, were partially digested. According to Melo & Campos Junior (1994), the supraorbital margin is devoid of teeth in R. guinotae (vs toothed supraorbital margin in R. constricta). However, the toothless supraorbital margin in R. guinotae is clearly an artifact due to the partial digestion of the exoskeleton. Still according to Melo & Campos Junior, R. guinotae further differs from R. constricta in that its rostral margin is sulcate. Actually, this characteristic is shared by both species and in the absence of other characters to support their distinction the two species are herein considered each other’s synonyms.