Thyasira tortuosa ( Jeffreys, 1881 )

Rodrigues, Clara F., Oliver, Graham & Cunha, Marina R., 2008, Thyasiroidea (Mollusca: Bivalvia) from the mud volcanoes of the Gulf of Cadiz (NE Atlantic), Zootaxa 1752, pp. 41-56 : 50

Thyasira tortuosa ( Jeffreys, 1881)

(Fig. 27)

Material examined. One live-collected specimen, TTR 16 cruise, station AT 622 Gr, Porto mud volcano, Gulf of Cadiz, 35 º 33.773 N, 09º 30.416 W, 3902 m, 3 June 2006 ( DBUA 00830.01).

Remarks. The only specimen examined is provisionally identified as Thyasira tortuosa and has the characteristically compressed and anteriorly expanded outline noted by Payne and Allen ( 1991). The shell from Gulf of Cadiz ( 5.5 mm) is much larger than any of the shells described by these authors ( 3.2 mm) and comes from a greater depth: 3902m whilst the maximum given by Payne & Allen ( 1991) was 2359 m. Dufour ( 2005) did not examine this species but the Gulf of Cadiz specimen has a Type 2 gill with both demibranchs. The gills are rather thick and have the same appearance as the ones that exhibit strong bacterial symbiosis such as T. flexu osa and T. gouldi .