An integrative study of some species of Gonaxia Vervoort, 1993 from off New Caledonia, with the establishment of Gonaxiidae as a new family of thecate hydroids (Cnidaria: Hydrozoa)

On some species of Zygophylax Quelch, 1885 (Cnidaria: Hydrozoa: Zygophylacidae) from off New Caledonia

Eleven species of hydroids belonging to the genus Zygophylax Quelch, 1885 are present in the material collected by the KANACONO, KANADEEP and KANADEEP 2 expeditions of the French Tropical Dee-Sea Benthos Program. Of these, ten represent known taxa and are fertile specimens, while the last one is unidentifiable in the absence of its gonosome. Seven species are new records for the study area. Zygophylax dispersa Peña Cantero, 2020 is assigned to the synonymy of Z. pseudafricana Vervoort & Watson, 2003, while Z. laertesi Peña Cantero, 2020 is comprehensively redescribed based on numerous and morphologically-varied specimens. Uncertainties exist as to the synonymy between Z. antipathes (Lamarck, 1816) and Z. rufa (Bale, 1884), but the oldest available binomen was nevertheless used. The presence of nematothecae is confirmed in Z. polycarpa Vervoort & Watson, 2003, a species with unusual gonothecae for the genus, now redescribed based on additional, abundant material. Zygophylax pseudosibogae Gu et al., 2022 is also redescribed, supplementing the original account. Finally, phylogenetic analyses, based on the 16S rRNA gene, allowed the genetic characterization of a total of twenty nominal species of Zygophylax, including sequences for eight taxa not considered so far. The number of Zygophylax species known from the New Caledonian area is raised from eight to sixteen.

Shallow water hydroids (Cnidaria, Hydrozoa) from the 2002 NOWRAMP cruise to the Northwestern Hawaiian Islands

Forty-two species of hydroids, excluding stylasterids, are reported in the present collection from the Northwestern Hawaiian Islands. Of these, four are anthoathecates and 38 are leptothecates. Among the latter, Sertularella affinicostata and Monotheca gibbosa are described as new species. The binomen Halopteris longibrachia is proposed as a new replacement name for Plumularia polymorpha var. sibogae Billard, 1913, an invalid junior primary homonym of P. sibogae Billard, 1911. Based largely on evidence from earlier molecular phylogenies, the genus Disertasia Neppi, 1917 is resurrected to accommodate species including Dynamena crisioides Lamouroux, 1824, Sertularia disticha Bosc, 1802, and Sia. moluccana Pictet, 1893. Sertularella robusta Coughtrey, 1876 is an invalid junior primary homonym of Sla. gayi var. robusta Allman, 1874a, and has been replaced here by the binomen Sla. quasiplana Trebilcock, 1928, originally described as Sla. robusta var. quasiplana Trebilcock, 1928. Clytia hummelincki (Leloup, 1935) is referred to the synonymy of its senior subjective synonym, C. brevithecata (Thornely, 1900). Following Reversal of Precedence provisions in the International Code of Zoological Nomenclature to preserve prevailing usage of binomena, the familiar names Sia. disticha Bosc, 1802 (also known as Dynamena disticha) and Lytocarpia phyteuma (Stechow, 1919b) are designated nomena protecta and assigned precedence over their virtually unknown senior synonyms Hydra quinternana Bosc, 1797 and Aglaophenia clavicula Whitelegge, 1899, respectively, names now reduced to the status of nomena oblita. Twenty species are reported for the first time from Hawaii [Eudendrium merulum Watson, 1985, Phialellidae (undetermined), Hebella sp., Hebellopsis scandens (Bale, 1888), H. sibogae Billard, 1942, Clytia brevithecata, C. linearis (Thornely, 1900), C. cf. noliformis (McCrady, 1859), Halecium sp., Sla. affinicostata, Sla. angulosa Bale, 1894, Pasya heterodonta (Jarvis, 1922), Tridentata orthogonalis (Gibbons & Ryland, 1989), Pycnotheca producta (Bale, 1881), Monotheca gibbosa, H. longibrachia, A. postdentata Billard, 1913, A. suensonii Jäderholm, 1896, A. whiteleggei Bale, 1888, and L. flexuosa (Lamouroux, 1816)]. Sertularia orthogonalis, reported for only the third time worldwide, is assigned to the genus Tridentata Stechow, 1920. Hydroids of the NOWRAMP 2002 collection consisted largely of presumptive widespread species, with over 75% of them having been reported elsewhere in the tropical Indo-west Pacific region.  

Second records and redescriptions of two rare thecate hydroids (Cnidaria: Hydrozoa) from the southwestern Pacific

Two thecate hydroids, Carpocladus fertilis Vervoort & Watson, 2003 (family Aglaopheniidae Marktanner-Turneretscher, 1890) and Gonaxia constricta (Totton, 1930) (family Gonaxiidae Maggioni, in Galea & Maggioni, 2021), are recorded for the first time from off New Caledonia, thus outside their original area of distribution in New Zealand waters. Specimens of both sexes of C. fertilis occur in the present collection, allowing the first description of its so far unknown female gonothecae. The trophosome of G. constricta, the only known to date, is thoroughly redescribed, pending the discovery of its gonothecae.