Amphisbetia minima ( Thompson, 1879 )

Gil, Marta & Ramil, Fran, 2021, Hydroids (Cnidaria, Hydrozoa) from the Vema and Valdivia seamounts (SE Atlantic), European Journal of Taxonomy 758, pp. 49-96 : 67-68

Amphisbetia minima ( Thompson, 1879)

Fig. 4B ; Table 7

Sertularia minima Thompson, 1879: 104–105 , pl. 17 fig. 3.

Amphisbetia minima – Millard 1975: 250, fig. 82h–k. — Galea & Schories 2012: 36 , fig. 3n–o.

Material examined

SOUTH ATLANTIC OCEAN • 2 colonies, growing on algae (1 with gonothecae); Vema Seamount , stn BT5; 31°37′16″–31°36′58″ S, 8°22′37″–8°23′06″ E; 71–94 m depth; 31 Jan. 2015; SEAFO-2015 leg.; SEAFO-2015-40617 , SEAFO-2015-40768 , LZM-UV slide R. 584 .

Remarks

The presence of “pores” or “holes” surrounded by a low perisarcal collar below various hydrothecae and usually located at the proximal internodes of the colonies was described by Ralph (1961), Millard (1975) and Vervoort & Watson (2003), but we have not observed any “pores” in our colonies. Nevertheless, these pores seem to be a variable feature in this species, as Vervoort & Watson (2003), after reviewing a large amount of material from New Zealand, stated that in some cases there is a pair of holes in the basalmost internode, but other colonies have a single pore or none at all. This structure has been interpreted as nematothecae ( Ralph 1961), comparable to the mamelon of Plumularidae (Millard 1975) , or glandular pores ( Vervoort & Watson 2003), but their true significance remains unknown.

Distribution

Amphisbetia minima is considered as a circumglobal species, without records from Arctic and Antarctic waters (Millard 1975; Vervoort & Watson 2003). In the South Atlantic, it was reported from Vema Seamount ( Millard 1966), the west coast of South Africa (Millard 1975) and the Tristan da Cunha group of islands ( Galea 2010, 2015). Its bathymetric distribution extends from the littoral zone to 664 m depth ( Vervoort & Watson 2003).

Figures

Fig. 4. A. Clytia gigantea (Hincks, 1866), portion of colony with three hydrothecae. B. Amphisbetia minima (Thompson, 1879), portion of hydrocladia with hydrothecae and basal gonotheca.C. Sertularella areyi Nutting, 1904, part of hydrocladia with hydrothecae. D. Sertularella polyzonias (Linnaeus, 1758), part of hydrocladia with hydrotheca and one gonotheca. E. Sertularella patagonica (d’ Orbigny, 1846), part of hydrocladia with hydrothecae.