Pasya heterodonta ( Jarvis, 1922 ) Calder & Faucci, 2021

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 : 31-32

Pasya heterodonta ( Jarvis, 1922) , comb. nov.

Fig. 9d–g

Pasythea heterodonta Jarvis, 1922: 344 , pl. 24 figs 11A–B, 12.

Type locality. Republic of Mauritius: Cargados (=Cargados Carajas Shoals), 24 fm (44 m) ( Jarvis 1922) .

Voucher material. Pearl & Hermes Atoll , on calcareous rubble, 28.ix.2002, three colonies, to 9 mm high, without gonothecae, coll. A. Faucci, ROMIZ B5436 .— Midway Atoll , on Halimeda sp. , 20.ix.2002, one colony, 8 mm high, without gonothecae, coll. A. Faucci, ROMIZ B5437 .— Pearl & Hermes Atoll, 19.ix.2002, three colony fragments, 8.5 mm high, without gonothecae, coll. A. Faucci, ROMIZ B5438 .— Pearl & Hermes Atoll , on calcareous rubble, 19.ix.2002, one colony, 8 mm high, without gonothecae, coll. A. Faucci, ROMIZ B5485 .— Kure Atoll , on calcareous rubble, 25.ix.2002, five colonies or colony fragments, to 9 mm high, with gonothecae, ROMIZ B5491 .

Remarks. Pasya heterodonta ( Jarvis, 1922) resembles the much better-known P. quadridentata (Ellis & Solan-der, 1786) in having stacked hydrothecal pairs on the stems ( Fig. 9e, f ). It differs, however, in having stacked pairs only at the extreme distal ends the cauli. Indeed, such groups are sometimes entirely lacking in present material, likely occurring in younger and earlier developmental stages of a given caulus. While gonothecae of the two species are fundamentally alike, suggestive of a close relationship, those of P. heterodonta appear to have fewer and less pronounced ridges. Grouping of hydrothecal pairs may occasionally occur as well in P. obliqua ( Lamouroux, 1816) , but hydrothecae of that species are more swollen and internodes are much shorter and stouter.

In reporting P. heterodonta from Moorea, French Polynesia, Vervoort & Vasseur (1977, as Dynamena heterodonta ) provided a description and illustrations of type material of the species. Unlike in P. quadridentata , hydrothecae were said to have a longer free portion that curved away from the internode, the operculum was more acute, and intrathecal cusps were well-developed. Similar differences in hydrothecal morphology had convinced Billard (1925) earlier to recognize P. heterodonta as distinct from P. quadridentata . Gibbons & Ryland (1989) acknowledged the distinct appearance of two equivalent morphotypes from Fiji, but nevertheless questioned the validity P. heterodonta . They suggested that perceived differences might not exceed the range of morphological variability within P. quadridentata . Given its distinct morphology, including the relative paucity of contiguous hydrothecal groups and their limitation to the distal end of the stems, P. heterodonta is taken here to be a species of the tropical Indo-Pacific, distinct from P. quadridentata (type locality: “...coast of Africa, not far from the island of Ascension ”). Pasya heterodonta has also been recognized recently as valid by Galea (2016, as Dynamena heterodonta ) in material from Indonesia.

Cauli of P. heterodonta lacking stacked pairs of hydrothecae closely resemble those of both Thuiaria maldivensis Borradaile, 1905 and Sertularia borneensis Billard, 1925 . Given their similarity, Schuchert (2003) suspected that the latter two might be conspecific. While gonothecae of T. maldivensis are still undescribed, Gibbons & Ryland (1989) and Schuchert (2003) provided descriptions and illustrations of gonothecae of S. borneensis based on specimens from Verde Island, the Philippines, and the Kei Islands, Indonesia, respectively. They differ from those of P. heterodonta in being strongly ridged. Moreover, Gibbons and Ryland noted the existence of two lateral horns that arose from a distal gonothecal collar, as in species assigned to Tridentata Stechow, 1920 (type species S. perpusilla Stechow, 1919b ).

As for Pasya Stechow, 1922 , the genus has recently been resurrected as valid ( Calder 2013) given the genetic distance of its type species, Sertularia quadridentata ( Ellis & Solander, 1786) , from that of Sertularia pumila Linnaeus, 1758 , type species of a currently polyphyletic genus Dynamena Lamouroux, 1816 . The extent of their separation is apparent in phylograms such as those of Moura et al. (2011) and Song (2019). Pasya was proposed by Stechow (1922) as a replacement name for use in Hydrozoa of Pasythea Lamouroux, 1812 (type species: Cellaria tulipifera Ellis & Solander, 1786 ), now restricted to Bryozoa. Tuliparia de Blainville, 1830 has the same type species ( Stechow 1922) and is a junior objective synonym of Pasythea .

Development of the intrathecal cusps varied considerably within colonies of P. heterodonta examined here ( Fig. 9d–f ). Disparities in their development were noted earlier by Billard (1925) and are apparent in illustrations of the species by Galea (2016: fig. 1L, N). Only slight variations in cusp development were noted by Vervoort & Vasseur (1977).

Reported Distribution. Hawaiian archipelago. First record.

Elsewhere. French Polynesia: Tuamotu Archipelago, Gambier Island ( Billard 1905, as Sertularia gracilis ).— Indonesia: Makassar Strait, 2°25ʹS, 117°43ʹE; E of Sumbawa, 34–36 m, Billard 1925, as Dynamena heterodonta ).— New Caledonia: Ile des Pins ( Redier 1966, as D. heterodonta ; Gravier Bonnet 2007, as D. heterodonta ).— South Africa ( Millard 1975, as Dynamena quadridentata , in part, Fig. 87H).—Moorea ( Vervoort & Vasseur 1977, as D. heterodonta ).— Fiji ( Gibbons & Ryland 1989, as D. quadridentata , type B).— Indonesia: Arafura Sea ( Galea 2016).

Figures

FIGURE 9. Sertulariidae. a, Disertasia crisioides (Lamouroux, 1824), part of hydrocladium with three hydrothecal pairs, Gardner Pinnacles, ROMIZ B5427. Scale equals 0.2 mm. b, Disertasia crisioides (Lamouroux, 1824), gonotheca, Gardner Pinnacles, ROMIZ B5427. Scale equals 0.2 mm. c, Disertasia disticha (Bosc, 1802), part of hydrocaulus with three hydrothecal pairs, Pearl & Hermes Atoll, ROMIZ B5428. Scale equals 0.2 mm. d, Pasya heterodonta (Jarvis, 1922), proximal end of hydrocaulus, with three hydrothecal pairs, Pearl & HermesAtoll, ROMIZ B5436. Scale equals 0.2 mm. e, Pasya heterodonta (Jarvis, 1922), distal end of hydrocaulus, with three hydrothecal pairs, two pairs being stacked, Kure Atoll, ROMIZ B5491. Scale equals 0.2 mm. f, Pasya heterodonta (Jarvis, 1922), distal end of hydrocaulus, with three stacked hydrothecal pairs, Pearl & Hermes Atoll, ROMIZ B5485. Scale equals 0.2 mm. g, Pasya heterodonta Jarvis, 1922), gonotheca, Kure Atoll, ROMIZ B5491. Scale equals 0.1 mm. h, Salacia tetracythara Lamouroux, 1816, part of hydrocladium with three hydrothecal pairs, Lisianski Island, ROMIZ B5429. Scale equals 0.2 mm. i, Salacia tetracythara Lamouroux, 1816, gonotheca from same colony, Lisianski Island, ROMIZ B5429. Scale equals 0.2 mm.