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.

Tima nigroannulata (Cnidaria: Hydrozoa: Eirenidae), a New Species of Hydrozoan from Japan.

Tima nigroannulata sp. nov. is described from medusae collected in shallow waters of four prefectures on the Pacific coast of Japan (Miyagi, Fukushima, Kanagawa, and Miyazaki), as well as from cultures maintained at two aquaria (Enoshima Aquarium, Kanagawa Prefecture; Tsuruoka City Kamo Aquarium, Yamagata Prefecture). Adult medusae differ from those of other known species of the genus Tima Eschscholtz, 1829 in the following combination of characters: (1) umbrella usually hemispherical or higher, (2) marginal tentacles up to 50 or more in number; and (3) black pigment granules form a ring around the umbrella rim, and sometimes extend onto the tentacles and radial canals. Their hydroids, from aquarium cultures, have stolonal colonies with pedicels of varied length, vestigial hydrothecae, slender and vase- to club-shaped hydranths, and a whorl of about 20 filiform tentacles with an intertentacular web basally. Medusa buds develop singly within gonothecae that arise from the hydrothecal pedicels. The cnidomes of both hydroid and medusa stages comprise heteronemes, provisionally identified as microbasic mastigophores. Medusae of T. nigroannulata are confirmed as a unique, cohesive lineage by comparing mtDNA COI sequence fragments with those from two congeners, resulting in three well-supported reciprocally monophyletic clades, one representing each species. Records of the western Atlantic medusa Tima formosa L. Agassiz, 1862 from Japan overlap those of T. nigroannulata, and are believed to have been based on the new species described herein.

Additions to knowledge of the biodiversity of benthic hydroids (Cnidaria: Hydrozoa) in the Balleny Islands (Antarctica).

The Balleny Islands, an isolated archipelago located 240 km off the coast of Victoria Land (East Antarctica), are separated from the Antarctic continental shelf by waters more than 2000 m deep. The benthic hydroid fauna of these islands is little known, with only 25 species reported so far. The present study contributes to a better knowledge of the benthic hydrozoans inhabiting this archipelago by studying a small collection held at the National Institute of Water and Atmospheric Research Invertebrate Collection at Wellington, New Zealand. Sixteen species of benthic hydroids were found in the collection, belonging to nine families and 12 genera of Leptothecata. Kirchenpaueriidae and Oswaldella, with three species each, are the most speciose family and genus. Ten species represent new records for the region. The total number of benthic hydroid species known from the islands is raised to 34.

Observation on the morphological and gonadal aspects of Cladonema radiatum (Class: Hydrozoa) from Tuticorin Bay, Southeast coast of India.

Studies on the hydrozoan fauna (Phylum: Cnidaria; Class: Hydrozoa) of the Indian waters during the 20th century were few in number (Nagale and Apte, 2013a, b). They originated in the early 1900s (Annandale, 1907; Ritchie, 1910, Thornely, 1916, Gravely, 1927), focussing on the taxonomy of hydroids in the 1960s along the southern coast, including Lakshadweep and Andaman Islands (Mammen, 1963, 1965a, b) and in the 1980s along the northern coast (Venugopalan Wagh, 1986). Species of the hydrozoan family Cladonematidae (Anthoathecata; Capitata) include benthic, creeping and swimming hydroids comprising four genera viz., Cladonema, Eleutheria, Staurocladia and the nomen dubium Dendronema (Schuchert, 2021). Cladonema differs from other genera of Cladonematidae by the branched tentacles either with an adhesive structure or cnidocytes and having nematocysts in oral knobs (Ghory et al., 2020 Farias et al., 2020). The taxonomy of Cladonema is uncertain and species in the genus have undergone several rounds of grouping and splitting. Gershwin Zeidler (2008) gave a detailed account of 13 putative species of Cladonema. However, Schuchert (2021) considered six species to be valid viz., C. radiatum, C. californicum, C. myersi, C. novaezelandiae, C. pacificum and C. timmsii. Studies on the genus Cladonema from Indian waters are patchy, with a brief report of its occurrence among other hydroids (Sastry and Chandramohan, 1989; Santhakumari and Nair, 1999; Arun et al., 2018). Among these records from India, C. myersi was collected from an experimental aquarium with seawater from an unknown location (Prasad, 1961). The present study documents the occurrence and describes the morphology and gonadal features of Cladonema radiatum from Tuticorin Bay, Gulf of Mannar, Southeast coast of India.

Stylasterids (Hydrozoa: Stylasteridae) from Mar del Plata submarine canyon and adjacent area (southwestern Atlantic), with a key to the species off Argentina.

The Argentine continental margin is a poorly explored area as regards its benthic biodiversity. Few works have been made near the Brazil-Malvinas confluence (around 38° S) regarding corals, especially in deep waters (over 1000 m). Hitherto 17 species of stylasterids are known from southwestern Atlantic (SWA) off Argentina. Fourteen species of stylasterids collected from the Mar del Plata submarine canyon and adjacent area in years 2012 and 2013 at depths between 800 and 2200 m are discussed, including the descriptions of 13 of them. The geographic distribution of six species and bathymetric range of occurrence of two species are broadened in this work. Stations where most specimens were collected are located in areas where sedimentation is known to be scarce. Species in common between the study area and the Antarctic region, south of Chile, South Africa, New Zealand and New Caledonia suggest the Circumpolar Antarctic Current and the Malvinas Current are the means for dispersion. A key of identification of all stylasterid species off Argentina is included.

Report on hydrozoans (Cnidaria), excluding Stylasteridae, from the Emperor Seamounts, western North Pacific Ocean.

Fourteen species of hydroids, collected during August 2019 by ROV SuBastian of the Schmidt Ocean Institute, are reported from the Emperor Seamount chain in the western North Pacific Ocean. Two others, Candelabrum sp. and Eudendrium sp., were observed only on videos taken by the ROV. From collections and video observations, eight species of hydroids were found at Jingu Seamount, three at Yomei, Nintoku, and Annei seamounts, and one at Koko Seamount and Hess Rise. At Suiko and Godaigo seamounts, hydroids were seen in videos but they could not be identified. Latebrahydra schulzei, an endobiotic associate of the hexactinellid sponge Walteria flemmingii Schulze, 1886 from Annei Seamount and Hess Rise, is described as a new genus and species tentatively attributed to Hydractiniidae L. Agassiz, 1862. Another new species, Hydractinia galeai, is described from Jingu Seamount. Among its distinctive characters is a zooid termed a sellectozooid, likely serving in both food capture and defence. Hydroids examined from Yomei, Nintoku, and Jingu seamounts are elements of a cold-water fauna occurring in the North Pacific Boreal Bathyal province, while those of Annei and Koko seamounts, and Hess Rise, are part of the biota of the Central North Pacific Bathyal province. Hydroids identified as Bouillonia sp., from Nintoku Seamount, represent the first record of this predominantly deep water tubulariid genus in the North Pacific Ocean. Bonneviella superba Nutting, 1915, from Jingu Seamount, is reported for the first time outside the Aleutian Islands. Bonneviella cf. gracilis Fraser, 1939, known elsewhere only from Dease Strait in the western Canadian Arctic, was also collected on Jingu. In addition to hydroids, medusae of Ptychogastria polaris Allman, 1878 were observed on videos from Nintoku, Jingu, Annei, and Koko seamounts at depths between 2423-1422 m. An unidentified siphonophore was observed near bottom at 2282 m on Nintoku Seamount.

The evolution and development of coloniality in hydrozoans.

Hydrozoan colonies display a variety of shapes and sizes including encrusting, upright, and pelagic forms. Phylogenetic patterns reveal a complex evolutionary history of these distinct colony forms, as well as colony loss. Within a species, phenotypic variation in colonies as a response to changing environmental cues and resources has been documented. The patterns of branching of colony specific tissue, called stolons in encrusting colonies and stalks in upright colonies, are likely under the control of signaling mechanisms whose changing expression in evolution and development are responsible for the diversity of hydrozoan colony forms. Although mechanisms of polyp development have been well studied, little research has focused on colony development and patterning. In the few studies that investigated mechanisms governing colony patterning, the Wnt signaling pathway has been implicated. The diversity of colony form, evolutionary patterns, and mechanisms of colony variation in Hydrozoa are reviewed here.

Arctic coastal benthos long-term responses to perturbations under climate warming.

Climate warming influences structure and function of Arctic benthic ecosystems. Assessing the response of these systems to perturbations requires long-term studies addressing key ecological processes related to recolonization and succession of species. Based on unique time-series (1980-2017), this study addresses successional patterns of hard-bottom benthos in two fjords in NW Svalbard after a pulse perturbation in 1980 and during a period of rapid climate warming. Analysis of seafloor photographs revealed different return rates of taxa, and variability in species densities, through time. It took 13 and 24 years for the community compositions of cleared and control transects to converge in the two fjords. Nearly two decades after the study initiation, an increase in filamentous and foliose macroalgae was observed with a subsequent reorganization in the invertebrate community. Trait analyses showed a decrease in body size and longevity of taxa in response to the pulse perturbation and a shift towards small/medium size and intermediate longevity following the macroalgae takeover. The observed slow recovery rates and abrupt shifts in community structure document the vulnerability of Arctic coastal ecosystems to perturbations and continued effects of climate warming. This article is part of the theme issue 'The changing Arctic Ocean: consequences for biological communities, biogeochemical processes and ecosystem functioning'.

Cryptic species and host specificity in the bryozoan-associated hydrozoan Zanclea divergens (Hydrozoa, Zancleidae).

Zanclea divergens is a tropical hydrozoan living in symbiotic association with bryozoans and currently reported from Papua New Guinea, Indonesia, and Maldives. Here, we used an integrative approach to assess the morpho-molecular diversity of the species across the Indo-Pacific. Phylogenetic and species delimitation analyses based on seven mitochondrial and nuclear loci revealed four well-supported molecular lineages corresponding to cryptic species, and representing a Pacific clade, an Indian clade, and two Red Sea clades. Since the general polyp morphology was almost identical in all samples, the nematocyst capsules were measured and analysed to search for possible fine-scale differences, and their statistical treatment revealed a significant difference in terms of length and width among the clades investigated. All Zanclea divergens specimens were specifically associated with cheilostome bryozoans belonging to the genus Celleporaria. The Pacific and Indian clades were associated with Celleporaria sp. and C. vermiformis, respectively, whereas both Red Sea lineages were associated with C. pigmentaria. Nevertheless, the sequencing of host bryozoans revealed that one of the Red Sea hydrozoan clades is associated with two morphologically undistinguishable, but genetically divergent, bryozoan species. Overall, our results show that Z. divergens is a species complex composed of morphologically cryptic lineages showing partially disjunct distributions and host specificity. The presence of two sympatric lineages living on the same host species reveal complex dynamics of diversification, and future research aimed at understanding their diversification process will likely improve our knowledge on the mechanisms of speciation among currently sympatric cryptic species.

Diversity and life-cycle analysis of Pacific Ocean zooplankton by videomicroscopy and DNA barcoding: Hydrozoa.

Most, but not all cnidarian species in the class Hydrozoa have a life cycle in which a colonial, asexually reproducing hydroid phase alternates with a free-swimming, sexually reproducing medusa phase. They are not well known, in part because many of them are microscopic, at least in the medusa phase. Matching the two phases has previously required rearing of the organism from one phase to another, which has not often been possible. Here we show that DNA barcoding makes it possible to easily link life-cycle phases without the need for laboratory rearing. Hydrozoan medusae were collected by zooplankton tows in Newport Bay and the Pacific Ocean near Newport Beach, California, and hydroid colonies were collected from solid substrates in the same areas. Specimens were documented by videomicroscopy, preserved in ethanol, and sent to the Canadian Centre for DNA Barcoding at the University of Guelph, Ontario, Canada for sequencing of the COI DNA barcode. In the order Anthoathecata (athecate hydroids), DNA barcoding allowed for the discrimination between the medusae of eight putative species of Bougainvillia, and the hydroid stages were documented for two of these. The medusae of three putative species of Amphinema were identified, and the hydroid stages were identified for two of them. DNA barcodes were obtained from medusae of one species of Cladonema, one adult of the by-the wind Sailor, Velella velella, five putative species of Corymorpha with the matching hydroid phase for one; and Coryne eximia, Turritopsis dohrnii and Turritopsis nutricula with the corresponding hydroid phases. The actinula larvae and hydroid for the pink-hearted hydroid Ectopleura crocea were identified and linked by DNA barcoding. In the order Leptothecata (thecate hydroids) medusae were identified for Clytia elsaeoswaldae, Clytia gracilis and Clytia sp. 701 AC and matched with the hydroid phases for the latter two species. Medusae were matched with the hydroid phases for two species of Obelia (including O. dichotoma) and Eucheilota bakeri. Obelia geniculata was collected as a single hydroid. DNA barcodes were obtained for hydroids of Orthopyxis everta and three other species of Orthopyxis. One member of the family Solmarisidae, representing the order Narcomedusae, and one member (Liriope tetraphylla) of the order Trachymedusae were recognized as medusae. The results show the utility of DNA barcoding for matching life-cycle stages as well as for documenting the diversity of this class of organisms.

Improved phylogenetic resolution within Siphonophora (Cnidaria) with implications for trait evolution.

Siphonophores are a diverse group of hydrozoans (Cnidaria) that are found at most depths of the ocean - from the surface, like the familiar Portuguese man of war, to the deep sea. They play important roles in ocean ecosystems, and are among the most abundant gelatinous predators. A previous phylogenetic study based on two ribosomal RNA genes provided insight into the internal relationships between major siphonophore groups. There was, however, little support for many deep relationships within the clade Codonophora. Here, we present a new siphonophore phylogeny based on new transcriptome data from 29 siphonophore species analyzed in combination with 14 publicly available genomic and transcriptomic datasets. We use this new phylogeny to reconstruct several traits that are central to siphonophore biology, including sexual system (monoecy vs. dioecy), gain and loss of zooid types, life history traits, and habitat. The phylogenetic relationships in this study are largely consistent with the previous phylogeny, but we find strong support for new clades within Codonophora that were previously unresolved. These results have important implications for trait evolution within Siphonophora, including favoring the hypothesis that monoecy arose at least twice.

Molecular Phylogeny Demonstrates the Need for Taxonomic Reconsideration of Species Diversity of the Hydrocoral Genus Millepora (Cnidaria: Hydrozoa) in the Pacific.

Millepora (Cnidaria: Hydrozoa: Milleporidae) spp. are distributed throughout shallow subtropical and tropical marine environments in the Indo-Pacific and Caribbean-Atlantic, and have traditionally been identified using pore characteristics and colony form. Until now, representatives of Millepora spp. on the island of Okinawa-jima, Japan, have been divided into five species; three branching species (Millepora intricata, M. tenera, M. dichotoma), one species with plate-like morphology (M. platyphylla), and one encrusting species (M. exaesa). There have been only a few reports from the Indo-Pacific that have studied the genetic diversity within Millepora spp., although phylogenetic analyses in the Caribbean-Atlantic have proven useful in delimiting closely-related species, while demonstrating that morphologically-based identification systems may have problems. In the present study, we sought to clarify taxonomic confusion of Millepora spp. in the Pacific by using sequence data of the ribosomal internal transcribed spacer (ITS-rDNA) of specimens from Okinawa, Japan and other localities (Johnston Atoll, Great Barrier Reef). Four separate clades were recovered from the ITS-rDNA analyses. Although we examined specimens of all three branching Millepora spp. previously reported from Okinawa-jima Island, in our phylogenetic analyses they were concentrated within a single clade, with only three specimens in other clades. Encrusting Millepora specimens were found within all clades, although it should be noted all species initially start as encrusting forms, and plate-like specimens were found within three clades. Our data also point to the existence of a previously unknown lineage within Millepora characterized by its ability to overgrow live scleractinian corals.

Aglaophenia octodonta (Cnidaria, Hydrozoa) and the Associated Microbial Community: a Cooperative Alliance?

Recently, genetic approaches have revealed a surprising bacterial world as well as a growing knowledge of the enormous distribution of animal-bacterial interactions. In the present study, the diversity of the microorganisms associated to the hydroid Aglaophenia octodonta was studied with epifluorescence, optical, and scanning electron microscopy. Small subunit ribosomal RNA gene sequencing with "universal" and taxon-specific primers allowed the assignment of the microalgae to Symbiodinium and the peritrich ciliates to Pseudovorticella, while the luminous vibrios were identified as Vibrio jasicida of the Harvey clade. To understand the possible relationships among Vibrio jasicida, Symbiodinium, A. octodonta, and Pseudovorticella, specific treatments were conducted in microcosm experiments, with the antibiotic ampicillin and other substances that interfere with bacterial and hydroid metabolism. Treatment of A. octodonta with ampicillin resulted in a decrease of bacterial luminescence followed by Pseudovorticella detachment and Symbiodinium expulsion and suggesting that these microorganisms form a "consortium" with beneficial metabolic interdependence. This hypothesis was reinforced by the evidence that low concentrations of hydrogen peroxide, which stimulate the bacterial oxidative metabolism and luminescence by releasing oxygen, were able to counteract the detrimental effect of ampicillin on the stability of the studied A. octodonta association. A model is proposed in which microalgae that release oxygen during photosynthesis are useful to luminous bacteria for their metabolism and for establishing/maintaining symbiosis leading to a close alliance and mutual benefit of the system A. octodonta-Vibrio jasicida-Pseudovorticella sp.-Symbiodinium sp.

Modern alongside traditional taxonomy-Integrative systematics of the genera Gymnangium Hincks, 1874 and Taxella Allman, 1874 (Hydrozoa, Aglaopheniidae).

We studied the diversity within the former genus Gymnangium in the South West Indian Ocean by using an integrative approach of both traditional (morphology-based) and modern molecular taxonomy. Nine species were recorded in the material collected. A total of 97 16S mitochondrial DNA sequences and 54 Calmodulin nuclear sequences from eight Gymnangium/Taxella species were analyzed. We found both morphological and molecular differences in the studied Gymnangium species that make it necessary to split the genus. It is proposed to revalidate the genus Taxella which is currently regarded as a synonym of Gymnangium. Two species of the genus Taxella (T. eximia and T. gracilicaulis), until now regarded as distinct species based on morphological characteristics, cluster together in one phylogenetic clade. Possible explanations are discussed. Two species from Madagascar new to science are herein described and rare species from the Indian Ocean islands are re-described.

High Abundance of the Epibenthic Trachymedusa Ptychogastria polaris Allman, 1878 (Hydrozoa, Trachylina) in Subpolar Fjords along the West Antarctic Peninsula.

Medusae can be conspicuous and abundant members of seafloor communities in deep-sea benthic boundary layers. The epibenthic trachymedusa, Ptychogastria polaris Allman, 1878 (Hydrozoa: Trachylina: Ptychogastriidae) occurs in the cold, high latitude systems of both the northern and southern hemispheres, with a circumpolar distribution in Arctic and sub-Arctic areas, and disjunct reports of a few individuals from Antarctica. In January-February 2010, during benthic megafaunal photosurveys in three subpolar fjords along the West Antarctic Peninsula (Andvord, Flandres and Barilari Bays), P. polaris was recorded in Antarctic Peninsula waters. The trachymedusa, identified from megacore-collected specimens, was a common component of the epifauna in the sediment floored basins at 436-725 m depths in Andvord and Flandres Bays, reaching densities up to 13 m-2, with mean densities in individual basins ranging from 0.06 to 4.19 m-2. These densities are 2 to 400-fold higher than previously reported for P. polaris in either the Arctic or Antarctic. This trachymedusa had an aggregated distribution, occurring frequently in Andvord Bay, but was often solitary in Flandres Bay, with a distribution not significantly different from random. Epibenthic individuals were similar in size, typically measuring 15-25 mm in bell diameter. A morphologically similar trachymedusa, presumably the same species, was also observed in the water column near the bottom in all three fjords. This benthopelagic form attained abundances of up to 7 m-2 of seafloor; however, most P. polaris (~ 80%), were observed on soft sediments. Our findings indicate that fjords provide a prime habitat for the development of dense populations of P. polaris, potentially resulting from high and varied food inputs to the fjord floors. Because P. polaris resides in the water column and at the seafloor, large P. polaris populations may contribute significantly to pelagic-benthic coupling in the WAP fjord ecosystems.

Unanimous Model for Describing the Fast Bioluminescence Kinetics of Ca2+ -regulated Photoproteins of Different Organisms.

Upon binding their metal ion cofactors, Ca2+ -regulated photoproteins display a rapid increase of light signal, which reaches its peak within milliseconds. In the present study, we investigate bioluminescence kinetics of the entire photoprotein family. All five recombinant hydromedusan Ca2+ -regulated photoproteins-aequorin from Aequorea victoria, clytin from Clytia gregaria, mitrocomin from Mitrocoma cellularia and obelins from Obelia longissima and Obelia geniculata-demonstrate the same bioluminescent kinetics pattern. Based on these findings, for the first time we propose a unanimous kinetic model describing the bioluminescence mechanism of Ca2+ -regulated photoproteins.

Phylogenetic relationships of Proboscoida Broch, 1910 (Cnidaria, Hydrozoa): Are traditional morphological diagnostic characters relevant for the delimitation of lineages at the species, genus, and family levels?

Overlapping variation of morphological characters can lead to misinterpretation in taxonomic diagnoses and the delimitation of different lineages. This is the case for hydrozoans that have traditionally been united in the family Campanulariidae, a group known for its wide morphological variation and complicated taxonomic history. In a recently proposed phylogenetic classification of leptothecate hydrozoans, this family was restricted to a more narrow sense while a larger clade containing most species traditionally classified in Campanulariidae, along with members of Bonneviellidae, was established as the suborder Proboscoida. We used molecular data to infer the phylogenetic relationships among campanulariids and assess the traditional classification of the family, as well as the new classification scheme for the group. The congruity and relevance of diagnostic characters were also evaluated. While mostly consistent with the new phylogenetic classification of Proboscoida, our increased taxon sampling resulted in some conflicts at the family level, specially regarding the monophyly of Clytiidae and Obeliidae. Considering the traditional classification, only Obeliidae is close to its original scope (as subfamily Obeliinae). At the genus level, Campanularia and Clytia are not monophyletic. Species with Obelia-like medusae do not form a monophyletic group, nor do species with fixed gonophores, indicating that these characters do not readily diagnose different genera. Finally, the species Orthopyxis integra, Clytia gracilis, and Obelia dichotoma are not monophyletic, suggesting that most of their current diagnostic characters are not informative for their delimitation. Several diagnostic characters in this group need to be reassessed, with emphasis on their variation, in order to have a consistent taxonomic and phylogenetic framework for the classification of campanulariid hydrozoans.

A description of two new species of the genus Erenna (Siphonophora: Physonectae: Erennidae), with notes on recently collected specimens of other Erenna species.

Two new Erenna species, E. insidiator sp. nov. and E. sirena sp. nov., are described from specimens collected in the vicinity of Monterey Bay, California, and also, for E. sirena at the southern end of the Gulf of California, Mexico. Further information on the three extant Erenna species is given, based on specimens collected in the same areas. These have enabled, for instance, the identification of three types of tentilla on the tentacles of E. cornuta Pugh, 2001, rather than the two noted on the single previously known specimen. The genus is remarkable for the presence of bioluminescent lures on the tentilla of all five species. In E. sirena sp. nov. the tentilla are also covered by a red-fluorescent layer, which was briefly described by Haddock et al. (2005), and further details are given herein. Another extraordinary feature of the colonies E. sirena sp. nov. is that the main part of the tentacle, with its tentilla, can be extended away from the siphosomal stem on a long peduncle. This phenomenon also appears to occur in E. laciniata Pugh, 2001, and has not been observed before for other physonect species.

The polyps of Oceania armata identified by DNA barcoding (Cnidaria, Hydrozoa).

The polyps of the widely distributed medusa Oceania armata have never been found in nature and only the primary polyp is known from breeding experiments. The fully developed colony is so far unknown. This report shows that DNA sequence data of the medusa stage of O. armata permits to identify several hydroid colonies from different geographic origins as the most likely polyp stage of this medusa. These hydroids had previously been misidentified as Turritopsis species, a closely related genus which also produces medusae resembling Oceania armata. It is concluded that most Turritopsis hydroids are not reliably identifiable to species level using morphological traits only. However, DNA barcodes, particularly 16S sequences, are an excellent tool to identify the species, although we still lack information on a few nominal species and the identities of some sequence-delimited clades need to be corroborated by the addition of topotype samples.

Status of the names of some hydroid species (Cnidaria, Hydrozoa), described from the Atlantic coast of Patagonia.

Thirty new species of benthic leptothecate hydroids were described and named from Patagonia in a 1991 PhD dissertation by Mohamed El Beshbeeshy. Although constituting nomina nuda under provisions of the International Code of Zoological Nomenclature (ICZN), the names of some species were used in several scientific publications between 1991 and 2011. In 2011, the dissertation of El Beshbeeshy was published in accordance with Article 8 of the ICZN. Several species-group names appearing in that work nevertheless fail to fully comply with certain articles of the code. The goal of this contribution is to review the nomenclatural availability of the names of those 30 new taxa, and to clearly establish the current status of El Beshbeeshy's material. Two of them were made available in 1999 as part of studies other than those of El Beshbeeshy, and correct authorship and date is here noted. Twenty-one of the nomina nuda were made available in a work published by El Beshbeeshy in 2011, although some constitute junior synonyms. Six of the new species-group names appearing in both the 1991 and 2011 works, established following a literature review of Patagonian species, were proposed without re-description, or designation of name-bearing types, or locations of such types. Most of them do not meet criteria of availability and remain nomina nuda. The status of each is discussed to avoid additional nomenclatural errors and continued taxonomic confusion.