Orthopyxis sargassicola

Orthopyxis sargassicola (Nutting, 1915)

Fig. 15c, d

Clytia sargassicola Nutting, 1915: 57, pl. 12, figs. 8, 9.

Type locality. Bahamas: “...southern edge of the Gulf Stream” (Nutting 1915).

Voucher material. Seminole Shores, just north of St. Lucie Inlet, 19.ii.1991, on stranded Sargassum, one colony, up to 3 mm high, with gonophores, coll. D.R. Calder, ROMIZ B1123.

Remarks. Although first reported on Sargassum from the Gulf Stream in the western North Atlantic, most records of Orthopyxis sargassicola (Nutting, 1915) to date have been from Brazil, where it appears to be common. There, Oliveira et al. (submitted) included records of it from algae, barnacles, and mussels. A shallow water species, it has been recorded from the intertidal zone to a depth of about 20 m (Migotto 1996).

Orthopyxis sargassicola resembles O. tincta Hincks, 1861a from Australia in having laterally compressed, strongly ribbed, and partially recumbent gonothecae, together with thickened and distinctly cuspate hydrothecae. However, its gonothecae are much less tapered distally and they have only about a half-dozen ribs instead of a dozen or more. Gonophores of O. sargassicola are liberated as reddish-coloured eumedusoids, lacking both tentacles and manubrium (Migotto 1996).

Reported distribution. Atlantic coast of Florida. First record.

Western Atlantic: Gulf Stream east of Cape Hatteras (Fraser 1943, as Eucopella sargassicola) southwards to Brazil (Oliveira et al. submitted), including Bermuda (Calder 1991a) and the Caribbean Sea (Leloup 1935, as Campanularia sargassicola). Leloup also recorded it from pelagic Sargassum in the central North Atlantic (29°N, 44°W) over the western side of the Mid-Atlantic Ridge.