Tridentata loculosa ( Busk, 1852 )

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 : 33

Tridentata loculosa ( Busk, 1852)

Fig. 10a, b

Sertularia loculosa Busk, 1852: 393 .

Sertularia ligulata .— Cooke, 1977: 97, fig. 24.— Coles et al., 2002a: 318.

Tridentata ligulata .— Coles et al., 2002b: 177.

Tridentata loculosa .— Carlton & Eldredge, 2009: 39.— Calder, 2020: 221, fig. 6f.

Type locality. Australia: Bass Strait , 45 fm (82 m) ( Busk 1852, as Sertularia loculosa ) .

Voucher material. Midway Atoll, 23.ix.2002, five colony fragments, to 1.3 cm high, with gonothecae, coll. A. Faucci, ROMIZ B5434 .—Gardner Pinnacles, on calcareous rubble, 14.ix.2002, one colony, 4 mm high, without gonothecae, coll. A. Faucci, ROMIZ B5435 .

Remarks. DNA sequences are as yet unavailable for Tridentata loculosa ( Busk, 1852) , and its genetic affinities remain uncertain. Following previous work ( Calder 2013, 2020), it has been assigned temporarily here to Tridentata Stechow, 1920 given the general resemblance of its trophosome and gonosome to species of that genus (including its type species, Sertularia perpusilla Stechow, 1919b ). Its indistinct marginal cusps, markedly dissimilar upper and lower opercular valves, and presence of a ligula (an intrathecal modification of the mantle, resembling a nematophore), set it apart from them. In particular, the taxonomic significance of the ligula is uncertain. Given its unusual characters, Hirohito (1974) suggested that a new genus might be warranted for the species, but later ( Hirohito 1995) retained it in Sertularia Linnaeus, 1758 following Vervoort & Vasseur (1977). With respect to its generic name, this species bears little morphological resemblance to Sertularia argentea Linnaeus, 1758 , type species of Sertularia . Thus, it can certainly be excluded from that genus ( Calder 2013, 2020), where it has usually been assigned.

Taxonomic reviews of T. loculosa were provided by Migotto (1996, as Sertularia loculosa ) and Calder (2013). Of note, Sertularia ligulata Thornely, 1904 was shown by Billard (1927) to be conspecific with S. loculosa . Although widely distributed and possibly circumglobal in tropical and subtropical waters, this species has not been recorded to date in the eastern Pacific Ocean. Colonies examined here from Midway Atoll (ROMIZ B5434), collected during September 2002, bore gonothecae.

Reported Distribution. Hawaiian archipelago. Oahu: Kaneohe Bay, 2 m, on Porites lobata ( Cooke 1977, as Sertularia ligulata ); Kaneohe Bay, Waiahole Reef ( Coles et al. 2002a, as S. ligulata ; Calder 2020); Waikiki, Aquarium Outside Reef, 3 m ( Coles et al. 2002b, as Tridentata ligulata ); Waikiki, Atlantis wreck, 20–30 m ( Coles et al. 2002b, as T. ligulata ).

Elsewhere. Warm waters of the Indian Ocean ( Millard 1975, as S. ligulata ), western and central Pacific ( Hirohito 1995, as S. ligulata ; Schuchert 2003, as S. ligulata ; Calder 2020), and western and eastern Atlantic ( Vervoort 1959, as S. ligulata ; Calder 2013).

Figures

FIGURE 10. Sertulariidae and Symplectoscyphidae. a, Tridentata loculosa (Bale, 1852), part of hydrocaulus with two hydrothecal pairs, Midway Atoll, ROMIZ B5434. Scale equals 0.2 mm. b, Tridentata loculosa (Bale, 1852), gonotheca, Midway Atoll, ROMIZ B5434. Scale equals 0.2 mm. c, Tridentata orthogonalis (Gibbons & Ryland, 1989), part of hydrocaulus with two hydrothecal pairs, Laysan Island, ROMIZ B5440. Scale equals 0.2 mm. d, Tridentata rugosissima (Thornely, 1904), part of hydrocaulus with one hydrothecal pair, Laysan Island, ROMIZ B5489. Scale equals 0.1 mm. e, Tridentata turbinata (Lamouroux, 1816), part of hydrocaulus with two hydrothecal pairs, Pearl & Hermes Atoll, ROMIZ B5444. Scale equals 0.1 mm. f, Tridentata turbinata (Lamouroux, 1816), gonotheca, Pearl & Hermes Atoll, ROMIZ B5444. Scale equals 0.2 mm. g, Bicaularia tongensis (Stechow, 1919b), part of hydrocaulus with two hydrothecae, Midway Atoll, ROMIZ B5445. Scale equals 0.1 mm.