Tridentata rugosissima ( Thornely, 1904 )

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 : 35-36

Tridentata rugosissima ( Thornely, 1904)

Fig. 10d

Sertularia rugosissima Thornely, 1904: 118 , pl. 2 fig. 4.

Sertularia subtilis .— Cooke, 1977: 97, fig. 25.— Carlton & Eldredge, 2009: 39.

Tridentata humpferi .— Coles et al., 2002a: 318; 2002b: 177, 234 [incorrect subsequent spelling].

Tridentata hupferi .— Carlton & Eldredge, 2009: 39.

Tridentata rugosissima .— Calder, 2020: 222, fig. 6g.

Type locality. Sri Lanka: “ Gulf of Manaar” (= Gulf of Mannar ), on algae ( Thornely 1904, as Sertularia rugosissima ) .

Material examined. Laysan Island , on Halimeda sp. , 17 ix.2002, one colony, 4.5 mm high, without gonothecae, coll. A. Faucci, ROMIZ B5489 .

Remarks. An account of Tridentata rugosissima ( Thornely, 1904) from Hawaiian waters has been provided earlier ( Calder 2020). The species has been reported there several times from locations around the island of Oahu ( Cooke 1977, as Sertularia subtilis ; Coles et al. 2002a, as Tridentata humpferi ; Coles et al. 2002b, as T. humpferi ; Calder 2020).

Hydroids of T. rugosissima are morphologically distinctive in having hydrothecal walls ringed by about 12 or more transverse ridges. Also present are distinct abcauline and less distinct adcauline intrathecal cusps. Subjective synonyms of the species, based on studies by Migotto (1996), include Sertularia hupferi Broch, 1914 from Ghana, S. subtilis Fraser, 1937b from Puerto Rico, and Geminella subtilis Vannucci Mendes, 1946 from Brazil.

While reported from the Indo-Pacific, central Pacific, and both eastern and western Atlantic, genetic comparisons of widely separated populations of hydroids assigned to T. rugosissima are warranted. Also needed is confirmation of the generic identity of the species, based to date only on morphology ( Stechow 1923c; Calder & Choong 2018; Calder 2020). Assigning it to Sertularia Linnaeus, 1758 , as in most works to date (including WoRMS), is clearly incorrect because T. rugosissima is morphologically remote from Sertularia argentea Linnaeus, 1758 , type species of that genus. It has been referred here to Tridentata Stechow, 1920 based on characters of both the trophosome and the gonothecae, which generally conform with those of the type species of the genus, Sertularia perpusilla Stechow, 1919b . Vannucci Mendes (1946, as Geminella subtilis ) appears to have been first in describing the gonotheca of T. rugosissima .

Reported Distribution. Hawaiian archipelago. Oahu: Kahe Point reef, 2 m, on coral rubble ( Cooke 1977, as Sertularia subtilis ); Kaneohe Bay, Pristine Reef ( Coles et al. 2002a, as Tridentata humpferi ; Calder 2020); Waikiki, Canoes ( Coles et al. 2002b, as T. humpferi ); Waikiki, Kapua Channel, 5 m ( Coles et al. 2002b, as T. humpferi ); Waikiki, Kaiser’s Channel ( Coles et al. 2002b, as T. humpferi ); Hawaii Kai, Channel Marker 1, Maunalua Bay, 4 m ( Coles et al. 2002b, as T. humpferi ).

Elsewhere. Indian Ocean ( Thornely 1904, 1916, as Sertularia rugosissima ; Millard & Bouillon 1973, as S. hupferi ); western Pacific ( Jäderholm 1919, as S. rugosissima ; Cooke 1975, as S. subtilis ; Yamada & Kubota 1987, as S. rugosissima ; Gibbons & Ryland 1989, as S. hupferi ); western Atlantic ( Fraser 1937b, as S. subtilis ; Migotto 1996, as S. rugosissima ; Calder & Kirkendale 2005, as Tridentata . subtilis ; Galea 2008, as S. rugosissima ; Oliveira et al. 2016, as S. rugosissima ; Miglietta et al. 2018, as S. rugosissima ); eastern Atlantic (Broch 1914, as S. hupferi ).

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.