Turritopsis minor ( Nutting, 1905 )

Calder, Dale R., 2010, Some anthoathecate hydroids and limnopolyps (Cnidaria, Hydrozoa) from the Hawaiian archipelago 2590, Zootaxa 2590 (1), pp. 1-91 : 15-16

Turritopsis minor ( Nutting, 1905)

Fig. 5

Corydendrium minor Nutting, 1905: 941 , pl. 2, fig. 1, pl. 7, figs. 8, 9.

Turritopsis minor .— Calder, 2004: 20.

Type locality. Hawaii: “north coast of Maui, 95 fathoms” (174 m) ( Nutting 1905) .

Material examined. Maui: Albatross Stn. 4098, off north coast, 95 fm (174 m), fragments of a colony, to 1.4 cm high, with hydranths and medusa buds, USNM 22184 [LECTOTYPE; labelled “TYPE”].–Maui: Albatross Stn. 4077, off northeast coast, 99 fm (181 m), several colony fragments, to 1.4 cm high, with shriveled hydranths and gonophores (sample appears to have been dry at some time), USNM 22164 [PARALECTO- TYPE; labelled “TYPE;” sample also contains a species of Lafoea ].–Oahu: off Haleiwa, 60 fm (110 m), R/ V Valiant Maid (no other collection data), on anthozoan axis, three colony fragments, to 3.1 cm high, with gonophores, BPBM (without collection number) .– Oahu: off Haleiwa, 60 fm (110 m), R/ V Valiant Maid (no other collection data), on anthozoan axis, small fragment of sample above, ROMIZ B3832 .

Other type material. Maui: CAS syntype 018683 (PARALECTOTYPE; Fautin & Weitbrecht 1985) .

Description. Hydroid colonies erect, bushy, reaching 3.1 cm high, arising from a dense hydrorhizal mat. Hydrocaulus strongly polysiphonic with slender individual tubes (<0.2 mm in diameter), irregularly and frequently branched, mostly in one plane; main branches resembling hydrocaulus, polysiphonic to strongly polysiphonic basally, gradually becoming thinner and monosiphonic distally, bearing more or less alternate branchlets; ultimate branchlets monosiphonic, slender, of varied length, adnate to stem for some distance basally, then abruptly curving outwards and becoming free distally, often constricted or wrinkled near insertion with stem, supporting a hydranth distally. Perisarc moderately thick, terminating on pedicels below hydranths; colour brownish-yellow in older parts, becoming almost clear distally. Hydranths elongate, clavate to fusiform, about 0.4 mm long, with about 12–16 filiform tentacles scattered over much of hydranth body, with distal ones longer than those at proximal end; hypostome elongate.

Gonophores free medusae. Medusa buds ovoid, attached to ultimate branchlets by short pedicels, one or more per branchlet, enclosed in a thin perisarcal capsule. According to Nutting (1905), manubrium apparently short; mouth quadrate; radial canals four, unbranched; marginal tentacles distinct, numerous but number and arrangement undetermined.

Remarks. Nutting (1905) referred this species to Corydendrium Van Beneden, 1844a , but noted that it produces medusae instead of fixed gonophores. It was assigned to the genus Turritopsis McCrady, 1857 by Calder (2004). Although Miglietta et al. (2007) treated it as valid, they remarked that it was insufficiently characterized because its life cycle was incompletely known. Additional knowledge of the medusa stage, and its reproductive biology, is needed to clarify relationships of the species with other species of the genus. Hydroid populations of a species from shallow waters in Hawaii (see Turritopsis nutricula McCrady, 1857 below) seem to differ in colony form from those of the deeper T. minor ( Nutting, 1905) in being less robust, less branched, and less strongly polysiphonic.

No holotype was designated for Turritopsis minor by Nutting (1905). Syntype material from the northeast and north coasts of Maui (USNM 22164, USNM 22184, respectively) exists in the National Museum of Natural History, Washington, DC. Additional syntype material, not examined here, exists at the California Academy of Sciences (CAS syntype 018683, Maui, one colony, IZ164; Fautin & Weitbrecht 1985). A fragmentary colony bearing intact hydranths and medusa buds (USNM 22184) has been chosen here as the lectotype to objectively define the species. Hydroid fragments in USNM 22164, designated as paralectotype material, are shrivelled, and the sample may have been dry sometime in the past. CAS syntype 018683 also comprises paralectotype material.

Reported distribution. Hawaii. Albatross Stn. 3859, “between … Molokai and Maui, 138 fathoms” (252 m); Albatross Stn. 4077, “northeast coast of Maui, 99 fathoms” (181 m); Albatross Stn. 4098, “north coast of Maui, 95 fathoms” (174 m) ( Nutting 1905).

Worldwide. Known only from Hawaii.