Corymorpha tropica, a new species of anthoathecate hydrozoan (Cnidaria: Hydrozoa) from Southeast Asia.

A new species of corymorphid, Corymorpha tropica sp. nov., of common occurrence in Southeast Asia, is described. The account is based on both its hydroid and newly-released medusa. The caulus of the former is conspicuously divided into two distinct parts: a proximal, perisarc-covered, papillate, light brown to orange-colored portion, and a distal, naked, non-papillate, flesh to brick red-colored portion. The hydranth is equally variously-colored, and has either a distinctly-demarcated or a more diffuse red, circular band around its base. A whorl of long blastostyles, situated slightly above the aboral whorl of tentacles, give rise to isolated clusters of gonophores borne on short, lateral pedicels. The dispersive stage is a free-living medusa that is released without gonads from the parent hydroid. At this stage, its umbrella is bell-shaped, with a moderately developed, rounded, apical projection and scattered nematocysts on the exumbrella, and has three atentaculate, conical bulbs, as well as a main tentacle provided with a distal, large, globular nematocyst cluster and up to two intermediate knobs on its adaxial side, the position of the latter clusters being diagnostic.

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.

Towards a better understanding of the genus Sciurella Allman, 1883 (Cnidaria: Hydrozoa: Plumulariidae): evidence from an integrative study.

The genus Sciurella Allman, 1883 is reassessed based on fertile specimens from Indonesia and Australia, using both morphological and genetic approaches. The genus is resurrected and kept distinct from Nemertesia Lamouroux, 1812 on the account of its long, tubular hydrothecae, and the gonothecae (of which only the female ones are known) provided with nematothecae. Stellate gonothecae correspond to S. indivisa Allman, 1883, while urn-shaped gonothecae are subjectively attributable to S. cylindrica (Kirchenpauer, 1876), comb. nov., a nominal species originally described based on sterile material. The taxonomy of the latter species is discussed in light of the available literature data, and Antennularia cylindrica Bale, 1884 is confidently assigned to its synonymy. Plumularia dolichotheca Allman, 1883 is provisionally transferred to Sciurella, as S. dolichotheca comb. nov., pending the discovery of fertile specimens and reliable evidence from molecular studies. The newly-generated genetic data for S. indivisa and S. cylindrica clearly confirm the distinction between Sciurella and Nemertesia, the two genera occupying divergent positions within the Plumulariidae phylogenetic hypotheses.

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).

Ten species belonging to the genus Gonaxia Vervoort, 1993 occur in recent collections gathered by KANACONO (2016), KANADEEP (2017) and KANADEEP 2 (2019) expeditions of the French Tropical Deep-Sea Benthos Program in deep waters of the New Caledonian region. They were studied using the classical, morphological approach, supplemented by the first genetic characterization of the genus undertaken so far. Two species are previously undescribed, namely G. incisa Galea, sp. nov. and G. solenoscyphoides Galea, sp. nov. Additional notes on the remaining species are provided, notably the discovery of the female gonothecae of G. crassicaulis Vervoort, 1993 and G. perplexa Vervoort, 1993. Lofty colonies, with distinctive cladia-bearing branches spirally-arranged around the stem, assignable to the recently-described G. plumularioides Galea, 2016 actually represent fully-developed colonies of G. errans Vervoort, 1993, as demonstrated using molecular markers, the latter nominal species having priority. Its unusual, club-shaped, longitudinally-ridged gonothecae, fully free from the stem, are described for the first time. Supplementary notes on the hydrotheca of G. crassicaulis Vervoort, 1993 are provided, together with the description of a distinctive gutter of perisarc channeling the coenosarc of the colony along the lumen of both the stem and cladia. A multi-locus phylogenetic hypothesis of the Macrocolonia supports the establishment of the family Gonaxiidae Maggioni, fam. nov., to accommodate the species dealt with herein.

An integrative study of Callicarpa gracilis Fewkes, 1881 and Aglaophenia trifida L. Agassiz, 1862, with notes on some hydroids (Cnidaria: Hydrozoa) from French Guiana.

Among the thecate hydroids brought back by the Proteus-Guyane 2017 expedition of the Muséum national d'histoire naturelle of Paris, France, from French Guiana, two interesting species are reported upon. The plumulariid Callicarpa gracilis Fewkes, 1881, known so far from the type specimen only, is comprehensively redescribed 140 years after its original description. It adopts two different morphotypes with respect to both its tropho- and gonosome, forming either simple or ramified colonies, with either structurally-complex or rudimentary phylactocarps, respectively. Taxonomic notes on the genera Callicarpa Fewkes, 1881 and Hippurella Allman, 1877 are provided in light of their intricate history of origin and fate, together with the provisional resurrection of Antomma Stechow, 1919, as an allied genus of the former. The aglaopheniid Aglaophenia trifida L. Agassiz, 1862, whose gonosome was only partly documented to date, is redescribed thoroughly based on specimens bearing male and female corbulae. Scanning electron microscopy and molecular data were also used to document both species. A checklist of the thecate hydroids from French Guiana gathered during Proteus-Guyane 2017 and Guyane 2014 expeditions is provided as an appendix, together with brief notes on some species. Not dealing with the present study, but taking advantage of it, a new name, Antennella billardi Galea, nom. nov., is proposed as a replacement name for Plumularia balei Billard, 1911, which is a permanently invalid junior primary homonym of P. balei Bartlett, 1907.

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.

On the hydroid genus Sibogella Billard, 1911 (Cnidaria: Hydrozoa: Plumulariidae), with descriptions of two new species.

The so far monotypic genus Sibogella Billard, 1911 is revised based on literature data. Its type species, S. erecta Billard, 1911, is thoroughly redescribed and illustrated, and accounts on two new congeners, S. flabellata sp. nov. from shallow waters of Indonesia and S. spissa sp. nov. from deep waters of New Caledonia, are provided. Single- (16S rRNA) and multi-locus (concatenated 16S, 18S, and 28S rRNA) phylogenetic assessments of the Plumulariidae, including newly-sequenced Sibogella material, supplement the alpha-taxonomical study.

Podocoryna martinicana, a new species of athecate hydroid (Cnidaria: Hydrozoa: Hydractiniidae) from the Caribbean.

A new species of hydroid, Podocoryna martinicana sp. nov., is described from the Lesser Antilles. It lives symbiotically with Iridopagurus caribbensis (A. Milne-Edwards & Bouvier, 1893) (Decapoda: Paguridae) inhabiting various gastropod shells. Its colonies are highly organized and develop exclusively around the aperture of the host shell. A few large, columnar gastrozooids provided with numerous tentacles arise from a perisarc-covered stolonal mat on the inner lip of the shell, and appear to form a gate when the hermit is withdrawn, while numerous, small, highly prolific gonozooids dress a line on the edge of the outer lip. Slender, very contractile tentaculozooids occur variably among the colonies. The dispersive stage, a free-swimming medusa with four well-developed marginal tentacles and no ocelli, is solely described based on young, sexually immature specimens. The species is further characterized by the peculiar bright white tinge of the core of both hydroid and medusa tentacles. Rich illustrations, data on the nematocyst complement, as well as comparisons with related congeners are provided.