Turritopsis sp.

Calder, Dale R. & Faucci, Anuschka, 2021, Shallow water hydroids (Cnidaria, Hydrozoa) from the 2002 NOWRAMP cruise to the Northwestern Hawaiian Islands, Zootaxa 5085 (1), pp. 1-73 : 9-10

Turritopsis sp.

Fig. 2b

Turritopsis nutricula .— Cooke, 1977: 82, fig. 10.— Grovhoug & Rastetter, 1980: 252.— Coles et al., 2002a: 206, 31, 343.— Carlton & Eldredge, 2009: 33.

Turritopsis cf. nutricula .— Calder, 2010: 16 , fig. 6.

Voucher material. Midway Atoll, on calcareous rubble, 23.ix.2002, one colony, 1.75 mm high, without gonophores, coll. A. Faucci, ROMIZ B5490 .

Remarks. While species of the genus Turritopsis McCrady, 1857 from Hawaii and elsewhere across the IndoPacific region have earlier been commonly assigned to T. nutricula McCrady, 1857 (e.g., Kramp 1968; Millard & Bouillon 1973, 1974; Millard 1975; Cooke 1977; Hirohito 1988; Park 1993; Bouillon 1995; Schuchert 1996; Watson 1996; Kubota 2005; Calder 2010), molecular investigations contradict that identification. Such studies reveal the existence of a species complex in T. nutricula ( Miglietta et al. 2007, 2019; Miglietta & Lessios 2009). Instead of being cosmopolitan in distribution, Miglietta et al. (2007) suggested that T. nutricula may be restricted to the western Atlantic Ocean. Little progress has yet been made in resolving the nomenclature of cryptic species within hydroids assigned to the species. As noted by Schuchert (2003), a likely valid species in the tropical Indo-west Pacific region is T. chevalense ( Thornely, 1904) , but others are of probable existence as well. For now, the sterile hydroid colony examined here is identified simply as Turritopsis sp.

Molecular phylogenetic studies also indicate that the family Oceaniidae Eschscholtz, 1829 , as presently constituted, is polyphyletic ( Prudkovsky et al. 2016; Schuchert 2016; Maggioni et al. 2017). Nevertheless, the type species of Turritopsis ( T. nutricula ) and that of Oceania Kölliker, 1853 ( O. armata Kölliker, 1853 ), the type genus of the family, cluster in close proximity to each other ( Prudkovsky et al. 2016; Schuchert 2016). Relationships of two other genera usually included in the family, Rhizogeton L. Agassiz, 1862 and Turritopsoides Calder, 1988b , appear to lie elsewhere. Species assigned to those genera, R. nudus Broch, 1910 and T. marhei Maggioni, Puce, Galli, Seveso & Montano, 2017 , occur in clades remote from O. armata ( Prudkovsky et al. 2016; Maggioni et al. 2017). Although substantial data gaps still exist in molecular assessments of the family, Turritopsis can confidently be included, with Oceania , in Oceaniidae .

Reported Distribution. Hawaiian archipelago. Oahu: Ala Wai Yacht Harbor, on stems of Pennaria ( Cooke 1977, as Turritopsis nutricula ).—Pearl Harbor, on test panels ( Grovhoug & Rastetter 1980, as T. nutricula ).— Kaneohe Bay, on test panels ( Grovhoug & Rastetter 1980, as T. nutricula ).—Kaneohe Bay from BPBM-D-457 (“Kaneohe Bay”), Coconut Island, Hawaii Institute of Marine Biology Pier, Kaneohe Yacht Club dock, MCB Fuel Dock, and SAG Harbor ( Coles et al. 2002a, as T. nutricula ).—Kaneohe Bay at Kaneohe Yacht Club dock, and Coconut Island and reef, shallow ( Calder 2010, as T. cf. nutricula ).

Elsewhere. The relationships and geographic distribution of the hydroid assigned to Turritopsis from Hawaii needs to be established by barcoding studies.

Figures

FIGURE 2. Pennariidae, Oceaniidae, Eudendriidae, and Phialellidae. a, Pennaria disticha Goldfuss, 1820, hydranth with a medusa bud and part of pedicel, Pearl & Hermes Atoll, ROMIZ B5404. Scale equals 0.2 mm. b, Turritopsis sp., hydrocaulus with two hydranths, Midway Atoll, ROMIZ B5490. Scale equals 0.2 mm. c, Eudendrium merulum Watson, 1985, hydranth and part of pedicel, Nihoa, ROMIZ B5405. Scale equals 0.1 mm. d, Eudendrium merulum Watson, 1985, hydrocaulus and proximal ends of three branches, Nihoa, ROMIZ B5405. Scale equals 0.2 mm. e, Eudendrium merulum Watson, 1985, female gonophores, Nihoa Island, ROMIZ B5405. Scale equals 0.1 mm. f. Phialellidae (undetermined), three hydrothecae, Gardner Pinnacles, ROMIZ B5406. Scales equal 0.05 mm.