Jellyfishes have ecological and societal value, but our understanding of taxonomic identity of many jellyfish species remains limited. Here, an approach integrating morphological and molecular (16S ribosomal RNA and cytochrome oxidase I) data enables taxonomic assessment of the blubber jellyfish found in the Philippines. In this study, we aimed to resolve doubt on the taxonomy of Acromitoides purpurus, a valid binomen at the time of our research. Our morphological findings confirm that this jellyfish belongs to the genus Catostylus, and is distinct from known species of the genus inhabiting the Western Pacific, such as Catostylus ouwensi, Catostylus townsendi, and Catostylus mosaicus. Detailed morphological and molecular analyses of the type specimens from the Philippines with the other Catostylus species revive the binomen Catostylus purpurus and invalidate A. purpurus. Genetic analysis also distinguishes this Philippine jellyfish from C. townsendi and C. mosaicus. Through this study, we arranged several Catostylidae taxa into species inquirendae (Catostylus tripterus, Catostylus turgescens, and Acromitoides stiphropterus) and one genus inquirenda (Acromitoides) and provided an identification key for species of Catostylus. This comprehensive study confirms the blubber jellyfish as C. purpurus, enriching our understanding of jellyfish biodiversity. The integration of morphological and genetic analyses proves vital in resolving taxonomic ambiguities within the Catostylidae family and in the accurate identification of scyphozoan jellyfishes.

Byronids are problematic fossils of possible cnidarian affinity, only rarely reported from the Devonian, but never previously studied in the Barrandian area, Czech Republic. Two new species Prestephanoscyphus branzovensis sp. nov. and Prestephanoscyphus robustus sp. nov. are erected from the Lochkovian and the Eifelian, respectively. Four poorly known species referred to Byronia are described in open nomenclature from the Emsian and Eifelian. The new genus Parabyronia gen. nov. with the type species Parabyronia elegans sp. nov. is closely related to other sphenothallids but is distinguished by transverse ridges on its theca and short spines at the apertural end of the theca. Definite identification of phosphatic rings as the attachment structure of byronids was proved by new material of the Lochkovian age. A dwarf conularia Pidiconularia gen. nov. with the type species Pidiconularia tubulata sp. nov. is remarkable by its minute size and very fine ornament; its conulariid affinity is proved by subrectangular cross-section and four internal carinae. Microstructure of theca of Prestephanoscyphus is characterised by alternation of compact laminae of aligned columnar microcrystallites and chambered laminae with isometric microcrystallites of apatite. Accretionary growth of byronid theca and structure of the holdfast with basal opening for the adhesive pedal disc support their cnidarian affinity although they likely display the bilateral instead of tetramerous symmetry. The protective function of bilaterally symmetrical whorls of internal apophyses in Prestephanoscyphus is suggested and their role in strengthening of thecal wall or supporting function of gastric septa are disputed. The byronids are regarded as epibionts rather than attached to the rocks. They are representatives of benthic groups with phosphatic shells that declined with decreasing availability of phosphorus in seas and oceans.

Myxozoans are widespread and common endoparasites of fish with complex life cycles, infecting vertebrate and invertebrate hosts. There are two classes: Myxosporea and Malacosporea. To date about 2500 myxosporean species have been described. By comparison, there are only five described malacosporean species. Malacosporean development in the invertebrate hosts (freshwater bryozoans) has been relatively well studied but is poorly known in fish hosts. Our aim was to investigate the presence and development of malacosporeans infecting a diversity of fish from Brazil, Europe and the USA. We examined kidney from 256 fish belonging variously to the Salmonidae, Cyprinidae, Nemacheilidae, Esocidae, Percidae, Polyodontidae, Serrasalmidae, Cichlidae and Pimelodidae. Malacosporean infections were detected and identified by polymerase chain reaction and small subunit ribosomal DNA sequencing, and the presence of sporogonic stages was evaluated by ultrastructural examination. We found five malacosporean infections in populations of seven European fish species (brown trout, rainbow trout, white fish, dace, roach, gudgeon and stone loach). Ultrastructural analyses revealed sporogonic stages in kidney tubules of three fish species (brown trout, roach and stone loach), providing evidence that fish belonging to at least three families are true hosts. These results expand the range of fish hosts exploited by malacosporeans to complete their life cycle.

We describe and illustrate a new genus and species of sea anemone from the intertidal in the Gulf of California (Mexico). Tenactis gen. nov. is characterized by mesenteries decamerously arranged, a single pair of directives attached to a single and strong siphonoglyph, small conchula, endodermal marginal sphincter muscle, pedal disc with basilar muscles, cinclides in pedal disc and proximal column, column with verrucae and pseudoacrorhagi, and a cnidom with p-mastigophores A2 and p-mastigophores B1 and B2a. Tenactis riosmenai gen. et sp. nov. is characterized by having a column not divisible into regions with longitudinal rows of verrucae distally and pseudoacrorhagi forming spherical structures at the tip, only 10 pairs of perfect mesenteries, diffuse endodermal marginal sphincter muscle and p-mastigophores A2 and p-mastigophores B1 and B2a in the filaments. Because of the decamerous arrangement of the mesenteries Tenactis gen. nov. most closely resembles some members of Actiniidae, Haloclavidae, Minyadidae, Oractiidae and Limnactinidae (Actinioidea), Halcampidae (Metridioidea) and Halcuriidae (Actinernoidea). However, the combination of having a decamerous arrangement of mesenteries, single siphonoglyph, conchula and cinclides indicate this new genus belongs to Haloclavidae. Additionally, the presence of a diffuse endodermal marginal sphincter muscle, basilar muscles, a single pair of directives, column with longitudinal rows of verrucae distally and pseudoacrorhagi, p-mastigophores A2, and p-mastigophores B1 and B2a in the filaments distinguish Tenactis riosmenai gen. et sp. nov. within Haloclavidae. This is the first record of the family Haloclavidae for the Gulf of California.

Based on material collected during oceanographic campaigns in the western Atlantic from 1958 to 2011, two species of primnoid octocorals belonging to the genus Callogorgia were identified: Callogorgia americana and Callogorgia arawak sp. nov. These species are described and illustrated herein and their geographic and bathymetric are given. This is the first record of the genus in the south-western Atlantic. Additionally, the elevation of C. americana americana and C. a. delta to species level is proposed, keeping Callogorgia gilberti, C. delta and C. americana as separate species.

The presence of five shallow-water scleractinian species at Ascension Island is confirmed, i.e. Favia gravida, Madracis sp., Siderastrea radians, Polycyathus atlanticus and Rhizosmilia gerdae. The three former are zooxanthellate, the two latter azooxanthellate. A sixth species, Cladocora debilis (azooxanthellate), dredged from moderately deep water is also expected to occur in shallow water. Madracis sp. and P. atlanticus are new records for the island. A previous record of Astrangia solitaria at Ascension is now referred to as P. atlanticus. Favia gravida, S. radians and C. debilis are amphi-Atlantic. Rhizosmilia gerdae is currently known only from Ascension Island and the Western Atlantic. None of the species are endemic to Ascension Island. No member of the family Dendrophylliidae has as yet been found at Ascension, whereas that family is represented at its nearest neighbour, St Helena Island.

During recent years, regular round structures have been collected from the top of Bed 12 of the Vossenveld Formation (Lower Muschelkalk, lower Middle Triassic, Anisian) in the Winterswijk area, eastern Netherlands. These are here illustrated and described as probable remains of jellyfish.

We redescribe and illustrate Halcurias pilatus McMurrich, 1893 and H. mcmurrichi Uchida, 2004 (Endocoelantheae, Halcuriidae) from newly collected specimens from Southern Chile and deep-water reefs off Florida, respectively. Halcurias pilatus was previously considered to have a disjunct distribution until Uchida (2004) described a new species for the material from the Bahamas. However, the description of H. mcmurrichi does not meet modern taxonomic standards. We provide new anatomical and cnidae data for H. pilatus and H. mcmurrichi. Both species differ in the distribution and cnidom of nematocyst batteries in the column, development of microcnemes mesenteries, cnidae and geographical distribution. We find that H. pilatus can have a weak mesogleal marginal sphincter and amend accordingly the diagnoses of the genus Halcurias, family Halcuriidae, and suborder Endocoelantheae. These new records represent the first time both species have been collected since their original descriptions.

Three marine hydroid species, Garveia grisea, Eudendrium glomeratum and Eudendrium merulum, widely spread and abundant in the Mediterranean Sea and with scarce records elsewhere, are reported for the first time from the Moroccan Atlantic coast. As part of a project studying the distribution of the hydroid assemblages from 0 to 30 m depth in the Strait of Gibraltar and the nearby area, the new records reported in the present contribution widen the known biogeographical distribution of these three species.

The new species of Zanclea sango sp. nov. is described from Okinawajima Island, Ryukyu Archipelago, south-western Japan. The new hydrozoan species is associated with at least three scleractinian corals (Pavona divaricata, P. venosa and Psammocora contigua). Zanclea sango sp. nov. is a polymorphic hydroid and the hydrorhiza grows between the coral skeleton and calicoblastic ectoderm. The hydrocaulus and hydrorhiza are surrounded by perisarc. Newly released medusae are almost spherical, with four perradial exumbrellar nematocyst pouches including stenoteles, and two long marginal tentacles with cnidophores containing macrobasic euryteles. Zanclea sango sp. nov. is allied to Zanclea gilii Boero et al., 2000 and Zanclea margaritae Pantos & Bythell, 2010, but it is distinguished by its cnidome, the presence of a perisarc around hydrorhiza, and lower host-specificity. According to a hypothetical Zanclea phylogeny, the ancestral species of Zanclea had an opportunistic association with some benthic organisms, such as algae or bivalves, and its hydrorhiza was covered by a perisarc. Later, some species established specific associations with benthic animals, after which the hydrorhiza lost the perisarc and became directly covered with host tissue. Among Zanclea inhabiting corals, the present species, with multiple coral host species and a perisarc around the hydrorhiza, seems to retain more ancestral character states than Z. gilii and Z. margaritae, which have specific coral host species and no perisarc around the hydrorhiza.

A survey of the distribution, percentage coverage, and diversity of octocoral fauna on the south-west coast of India yielded fourteen species from six families: Clavulariidae, Nephtheidae, Melithaeidae, Plexauridae, Gorgoniidae and Ellisellidae. This study produced ten new zoogeographical records of octocoral species to India, two species which were first records to the shallow water fauna (11–12 m depth), and one found to be a potential new record to the Indian coast. Octocoral coverage was <1% at all sites and diversity ranged from 6–13 species among the five study sites.

New findings of the scleractinian coral Dendrophyllia laboreli in various localities off the European coast in the Gulf of Cadiz and the Strait of Gibraltar, as well as the Atlantic coast of Morocco, are reported. These new findings redefine the current northernmost known limit of distribution of this species, previously known in African localities from Ghana to the Canary Islands. Some ecological and biogeographical remarks are also included.

Three species of hard corals including Echinopora gemmaceaLeptoria irregularis (Faviidae) and Montipora incrassata (Acroporidae) were recorded for the first time from north-east of Larak Island in the Strait of Hurmoz, Persian Gulf in late 2008. The review of previous studies revealed that these species were new reports from Larak Island situated in the northern Persian Gulf. Of these species only Echinopora gemmacea has previously been reported from the Oman Sea. No evidence of Leptoria irregularis and Montipora incrassata has been reported from the southern Persian Gulf and Oman Sea.

The occurrence of the scyphozoan Cassiopea andromeda is reported from the Maltese Islands, where a sizable aggregation was found in Marsamxett Harbour. This is the first record of this circumtropical species from the central Mediterranean Sea, hitherto known from the Levantine and Aegean basins. It is suggested that the most likely vector responsible for transporting this species to the Maltese Islands is shipping.

Three new species belonging to the family Resomiidae (Siphonophora: Physonectae) are described from material mainly collected by ROVs in the vicinity of Monterey Bay, California, USA, with some additional submersible-collected specimens from The Bahamas. Although these species, Resomia ornicephala, R. persica, and R. dunni, show some differences from those previously described, particularly in the shape of the nectophores, they have all been placed in the genus Resomia. They retain the basic characteristic of having two forms of tentilla on the same tentacle, the more proximal form, with a spirally coiled cnidoband, becoming reconfigured into the more distal form, usually with a zigzagged cnidoband, although in one of the new species the zigzagging of the cnidoband is less well-defined.

Cytomorphological characters of Polypodium hydriforme—a unique cnidarian, adapted to intracellular parasitism inside oocytes of Acipenseriform fish—are reviewed and analysed. Polypodium's unique characters, those shared with the Myxozoa, and the characters shared with bilateral triploblastic animals are listed. The set of unique features has allowed us to allocate Polypodium to a separate cnidarian class Polypodiozoa Raikova, 1988. The combination of characters displayed by P. hydriforme suggests that this animal is not an aberrant cnidarian, as it was formerly believed, but a relic of a major cnidarian group (class Polypodiozoa) that has undergone reduction due to adaptation to parasitism.

Modern in situ survey technologies such as crewed submersibles, remotely-operated vehicles (ROVs), towed camera arrays, and visual/video plankton recorders (VPRs) were used to characterize the dominant anthomedusan species off the eastern seaboard of Japan. Notes on the taxonomy, distribution, behaviour and interspecies interactions are presented for the four observed species: Euphysa japonica, E. flammea, Calycopsis nematophora and Pandea rubra. A new generic definition for the genus Calycopsis is proposed. The possibility of run-on, cascading detrimental effects of oceanic acidification on midwater ecosystems was identified from observations made during the present study.

A new interstitial hydroid, Sympagohydra tuuli, has been collected from the three-dimensional brine channel system of the coastal fast ice off Barrow, Alaska (71°N 156ºW) in 2003 to 2006. This is the first cnidarian species described from the sea ice interstitial habitat. A morphological and systematic account of the new species is provided here. The hydroid stage is represented by solitary naked polyps, which become almost spherical under contraction. Body length can vary from 200 µm to >1 mm according to the degree of relaxation. The aboral side is extensible into a tubular foot-like projection made by epidermal tissue only, a typical feature of representatives of Protohydridae, order Capitata. However, in contrast to the other two known Protohydridae species, S. tuuli is characterized by three to four solid filiform tentacles, armed with microbasic mastigophore and desmoneme cnidocysts, and located at the base of a short hypostome bearing stenoteles. A small number of mastigophores are also scattered along the body column. Due to its unique combination of features, this taxon is designated here as a new species, and the new genus Sympagohydra is established as a new member of the class Hydroidomedusa, subclass Anthomedusae, order Capitata, family Protohydridae, to accommodate S. tuuli.

Hydroidolina is a group of hydrozoans that includes Anthoathecata, Leptothecata and Siphonophorae. Previous phylogenetic analyses show strong support for Hydroidolina monophyly, but the relationships between and within its subgroups remain uncertain. In an effort to further clarify hydroidolinan relationships, we performed phylogenetic analyses on 97 hydroidolinan taxa, using DNA sequences from partial mitochondrial 16S rDNA, nearly complete nuclear 18S rDNA and nearly complete nuclear 28S rDNA. Our findings are consistent with previous analyses that support monophyly of Siphonophorae and Leptothecata and do not support monophyly of Anthoathecata nor its component subgroups, Filifera and Capitata. Instead, within Anthoathecata, we find support for four separate filiferan clades and two separate capitate clades (Aplanulata and Capitata sensu stricto). Our data however, lack any substantive support for discerning relationships between these eight distinct hydroidolinan clades.