Turritopsis cf. nutricula McCrady, 1857

Calder, Dale R., 2010, Some anthoathecate hydroids and limnopolyps (Cnidaria, Hydrozoa) from the Hawaiian archipelago 2590, Zootaxa 2590 (1), pp. 1-91 : 16-17

Turritopsis cf. nutricula McCrady, 1857

Fig. 6

Oceania (Turritopsis) nutricula McCrady, 1857: 56 , pl. 4, figs. 1–10, 12–15, 28a; pl. 5, figs. 11, 16–18, 28b.

Turritopsis nutricula .– Cooke, 1977: 82, fig. 10.– Grovhoug & Rastetter, 1980: 252.

Material examined. Oahu : Kaneohe Bay, shallow water, x.1972, six colony fragments, now in poor condition, up to 1.6 cm high, with medusa buds (and medusae in second vial), coll. W.J. Cooke, BPBM D456 .– Oahu : Kaneohe Bay , Kaneohe Yacht Club, dock (Stn. 20); 5.xi.1999, one colony, 1.9 cm high, with medusa buds, coll. R. DeFelice and S. Coles, ROMIZ B3298 .– Oahu : Kaneohe Bay, Coconut Island reef, 8.xi.1999, two fragmentary colonies, 0.8 and 0.6 cm high, with medusa buds, coll. R. DeFelice and S. Coles, ROMIZ B3300 .– Oahu : Kaneohe Bay, Coconut Island, 24.vii.2009, on sponges, two colonies, to 1.9 cm high, with medusa buds, coll. D.R. Calder, ROMIZ B3820 .

Description. Hydroid colonies erect, up to 1.9 cm high, arising from a creeping hydrorhiza. Hydrocaulus and main branches polysiphonic over most of length in larger colonies, smaller colonies less strongly so, becoming monosiphonic at distal extremities, irregularly branched; branches adnate basally, curving gradually to abruptly outwards and becoming free distally. Perisarc moderately thin, terminating at hydranth base below tentacles, never annulated, clear to yellowish, outer layer mostly smooth, inner layer with wrinkles and creases; pedicels of nearly equal diameter throughout. Hydranths clavate to nearly spindle-shaped, up to 1.4 mm long, 0.2 mm wide; tentacles filiform, 14–24 in number, scattered over distal three-quarters or more of hydranth, distal ones longer and thicker than those basally; hypostome conical to proboscis-like.

Gonophores free medusae. Medusa buds globular, enveloped in filmy perisarc, attached by short pedicels to stem and branches, most frequent on ultimate branchlets below hydranths, often with as many as 7–8 buds in close proximity and at various stages of development surrounding a branchlet, manubrium short; radial canals four; tentacles retracted into subumbrellar cavity.

Remarks. The identity of this hydrozoan in Hawaiian waters, generally assigned in the past to Turritopsis nutricula McCrady, 1857 , cannot be established with certainty on the basis of its hydroid trophosome alone. Knowledge about morphology and reproductive strategies of its virtually unstudied medusa stage is necessary, but such information is presently lacking. The prevailing identification is provisionally retained here until the taxonomy of the species is better resolved.

Miglietta et al. (2007) referred Cooke’s (1977) report of Turritopsis nutricula from Ala Wai Yacht Harbor, Oahu, to the offshore Hawaiian species T. minor Nutting, 1905 solely on zoogeographic grounds. However, comparisons of shallow inshore and deeper water offshore populations of the genus Turritopsis McCrady, 1857 from the region are needed before it can be determined whether or not they are conspecific. This hydrozoan also shares some characters with the widespread T. dohrnii ( Weismann, 1883) , T. polycirrha ( Keferstein, 1862) from Europe, and T. rubra ( Farquhar, 1895) from Tasmania and New Zealand, as well as T. nutricula from the east coast of the Americas. Differences among these species were summarized in Schuchert (2004), who discovered that European populations previously thought conspecific with the oviparous T. nutricula were referable instead to either T. dohrnii or especially to the larviparous T. polycirrha . Indeed, Miglietta et al. (2007) suggested on the basis of molecular studies that T. nutricula was restricted to the western Atlantic Ocean. More evidence is needed to support that claim, but their results establish that other species have frequently been misidentified as T. nutricula , especially in the Mediterranean Sea and in Japanese waters.

Meanwhile, Carlton & Eldredge (2009) believed T. nutricula had been introduced to Hawaii, possibly from the North Atlantic and likely by shipping. Extensive naval and merchant ship activities have been carried out for decades between Honolulu and ports on the Atlantic and Gulf coasts of the United States, where T. nutricula is common ( Calder 1971; Calder & Cairns 2009). Moreover, American oysters ( Crassostrea virginica ), a known substrate of T. nutricula ( Calder 1971: 31) , were introduced to Hawaii several times during the late 19 th and early 20 th centuries ( Carlton & Eldredge 2009). Yet hydroids from Hawaii appear to be unlike T. nutricula from the type locality of Charleston Harbor on the Atlantic coast of the United States in having colonies of moderate size (often 1–2 cm or more in height) that are branched and polysiphonic rather than small (less than 1 cm), sparingly branched or unbranched, and monosiphonic. Turritopsis dohrnii is also known to be invasive, having recently been reported from worldwide loactions ( Miglietta & Lessios 2009). As for the shallow-water species of Turritopsis from Hawaii, research on the medusa stage and its modes of reproduction, molecular investigations, or both are needed to establish its identity.

Material above catalogued as BPBM D456 contained two vials, one with hydroids and a second labelled “ T. nutricula medusae.” Medusae are no longer present in this vial.

Reported distribution. Hawaii. Oahu: Ala Wai Yacht Harbor, on stems of Pennaria ( Cooke 1977) .

Worldwide. Western Atlantic; reports from elsewhere including Hawaii need verification ( Miglietta et al. 2007; Miglietta & Lessios 2009).