Turritopsis sp. McCrady 1857

Turritopsis sp.

(Fig. 2A)

? Turritopsis nutricula: Ramil & Vervoort, 1992: 17–18; Peña Cantero & García Carrascosa, 2002: 26, fig. 3e (not Turritopsis nutricula McCrady, 1857).

? Turritopsis cf nutricula: Vervoort, 2006: 212–213, fig. 6 no.3.

Material examined. MAURIT-0911, stn MUDR01, 16º08´24”N, 16º57´12”W, 488 m, 5-XII-2009: one colony, without gonophores.

MAURIT-0911, stn MUDR05, 18º08´43”N, 16º35´42”W, 421 m, 8-XII-2009: one colony, without gonophores.

MAURIT-0911, stn MUDR07, 18º35´40”N, 16º43´12”W, 460 m, 12-XII-2009: one colony, without gonophores.

MAURIT-1011, stn MUDR20: 16º08´11”N, 16º56´08”W, 405 m, 7-XII-2010: one colony, without gonophores.

MSM 16 /3, stn GeoB 14796–1, ROV, 20°14.840’– 20°14.575’N, 17°40.193’– 17°40.071’W, 487–642 m, 3-XI- 2010: two colonies attached to Halecium beanii, without gonophores.

Biology. This species has been found growing on algae and invertebrates, such as bryozoans, hydrozoans and polychaete tubes (Peña Cantero & García Carrascosa 2002; Vervoort 2006, both as Turritopsis nutricula McCrady, 1857). Gonophores has been observed in March by Vervoort (2006).

In our material Turritopsis sp. has always been associated with cold-water coral mounds, nevertheless some colonies were also found growing on the hydroid H. beanii. Gonophores were not found.

Distribution. Turritopsis sp. was collected in several localities stretching from Banc d’Arguin in the north to the Senegalese border in the south, between 405 and 642 m depth. The material reported as Turritopsis nutricula McCrady, 1857 (Ramil & Vervoort 1992; Peña Cantero & García Carrascosa 2002) and Turritopsis cf nutricula (Vervoort 2006) was collected from Alboran Sea, Atlantic coast of Morocco and South of Madeira from 0 to 580 m depth.

Remarks. The material studied by us included only small monosiphonic colonies with greatly damaged or without hydranths. The colony structure matched that of Turritopsis nutricula described by Ramil and Vervoort (1992) from the Strait of Gibraltar region: lateral branches running parallel for some distance before curving away from the main axis and a strong perisarc composed of two sheaths, the smooth external sheath and the internal wrinkled sheath (fig. 2A). The nematocysts are microbasic euryteles (7–7.5 × 4–5 μm) and desmonemes (3.5–5 x 3–3.5 μm). Turritopsis nutricula was traditionally considered as an almost cosmopolitan or circumglobal species (Ramil & Vervoort 1992; Schuchert 1996; Vervoort 2006). Nevertheless, Schuchert (2004) indicated that T. nutricula is an American species only known in the West Atlantic. He also interpreted Turritopsis polycirrha (Keferstein, 1862) from the Northeast Atlantic, Turritopsis dohrnii (Weismann, 1883) from the Mediterranean and Turritopsis rubra (Farquhar, 1895) from New Zealand as valid species, which were confirmed using molecular studies (Miglietta et al. 2007).

The records of T. nutricula off Cape Spartel on the Atlantic side of the Strait of Gibraltar, the Strait proper and the southern part of the Alboran Sea (Ramil & Vervoort 1992) were included by Schuchert (2004) and Miglietta et al. (2007) within T. dohrnii. However, molecular studies identified a putative second species of Turritopsis in the Mediterranean that was quite different from T. dohrnii and T. nutricula (Miglietta et al. 2007). Because of the proximity of the collecting station (Almería, southern Spain) to the Strait of Gibraltar, the authors hypothesized that it may represent T. polycirrha, the only known Turritopsis species from the Northeast Atlantic. The same argument can be applied to the records of Ramil & Vervoort (1992).

The nematocysts in our colonies were slightly smaller and the microbasic euryteles clearly wider than those reported by Martell et al. (2016) for T. dohrnii; this, together different geographical and bathymetrical distributions confirm that they are different species, with T. dohrnii restricted to the Mediterranean Sea (Schuchert 2004; Martell et al. 2016). The polyp phase of T. polycirrha is not well known (Schuchert 2004, 2012) and the nematocysts, described only in the medusa (Russell 1953; Schuchert 2004), are bigger than those found in the colonies of Turritopsis sp. In addition, differences in bathymetric and geographical distributions— T. polycirrha seems to be a shallow-water boreal species only known in the North Sea, England and Normandy (Vervoort & Faasse 2009; Schuchert 2012), but never reported from the Lusitanian Province—argue that the Northwest African Turritopsis could represent a different species.