Hydroid Species Research Articles

Shallow-water benthic hydroids from Tethys Bay (Terra Nova Bay, Ross Sea, Antarctica)

The shallow-water hydrozoan Antarctic fauna is still poorly studied, and available knowledge mostly refers to samples gathered by traditional ship-operated gears. By scuba diving in the coastal areas off the Italian Antarctic station “Mario Zucchelli” (Ross Sea, Terra Nova Bay), in the austral summer 2002–2003, a total of 20 hydrozoan species were found, belonging to 10 families and 13 genera. As hypothesized, Anthoathecata (11 species), usually under-represented in collections from indirect sampling gears, are common as also are Leptothecata (9 species). Hydractiniidae and Hydractinia are the dominant family and genus, followed by Haleciidae and Halecium. A new species to science, Halecium exaggeratum sp. nov. is also described. Most species are either endemic to Antarctic waters or restricted to Antarctic/sub-Antarctic areas; only two species have a wider distribution. Material reared in aquaria at the Italian Antarctic Base Mario Zucchelli facilitated knowledge of the life cycle and reproductive biology of several species. In particular, Opercularella belgicae was found to liberate a medusa stage referable to Phialella, and the species is assigned here to that genus, as Phialella belgicae. Also, extraordinary is the complete absence or scant representation of the most typical Antarctic benthic hydroid genera (Antarctoscyphus, Oswaldella, Schizotricha, Staurotheca, and Symplectoscyphus), likely related to the shallow limits of sampling (down to 48 m).

Hydrozoan species richness in the Mediterranean Sea: past and present

AbstractThe Mediterranean hydrozoan fauna (Siphonophora excluded) comprises 400 species; most (68%) occur in the Atlantic Ocean, 20% are endemic to the Mediterranean, 8% are of Indo‐Pacific origin, and 4% are non‐classifiable. There are 69 nonindigenous (NIS) species in the basin: 44% of these are casual (recorded just one or very few times), 28% established (widely recorded in the basin), 6% invasive (established NIS that are able rapidly or largely to disseminate away from the area of initial introduction, having a noticeable impact on the recipient community), and 22% questionable (of doubtful taxonomic status). Entry through the Suez Canal and range expansion through the Gibraltar Strait, often enhanced by ship traffic, appear to be the main processes for recent species introductions, but uncertainties remain for many NIS. Species additions immediately result in larger local or regional species pools, but the newcomers might impact on populations of native species, altering extinction probabilities. A more reliable evaluation of the species pool can be accomplished by adding new species when they enter the taxonomic record (i.e. the records of any taxon in all types of literature), and by removing species that have not been found for a ‘reasonable’ time (e.g. several decades). Of the 400 non‐siphonophoran hydrozoan species known to occur in the Mediterranean Sea, positive records in the last 10 years are available for 156 species (39%), whereas records of the remaining 244 species are older than a decade: 67 species have not been recorded for 41 years, 13 for 31–40 years, 79 for 21–30 years, and 85 for 11–20 years.

Depth‐ and substrate‐related patterns of species richness and distribution of hydroids (Cnidaria, Hydrozoa) in Arctic coastal waters (Svalbard)

AbstractHydroid diversity and species composition were studied in Arctic coastal waters around the Norwegian Svalbard Archipelago. The aim of the present study was to examine the influence of physical factors (depth and substrate type) on the distribution and diversity of the benthic hydrozoan fauna that has been poorly studied in the high‐latitude polar region. The study is based on a total of 557 samples collected between 1996 and 2007. Over 1200 colonies and 70 taxa of Hydrozoa were collected by SCUBA divers, dredges and van Veen grabs. The distribution patterns with respect to major environmental factors were studied based on presence/absence data. Four substrate types were most commonly colonized by hydroid colonies: algae, bryozoans, rocks and hydrozoans. The highest species richness was noted on algae and rocks. Shallow water communities of the study area were characterized by a high hydroid species richness. A number of species decrease along the depth gradient. Some species have shown some preferences towards selected substrates or one of the two depth zones, but most hydroid species were generalists in terms of both the depth and substrate preferences. No species could be classified as substrate‐specific (i.e. occurring only on one substrate type). The substrate heterogeneity was shown to be an important driver of hydroid species richness in Arctic coastal waters.

Retinoic acid influences antero‐posterior positioning of peptidergic neurons in the planula larva of the hydrozoan Clava multicornis

AbstractRetinoic acid (RA) is a derivative of vitamin A known to be involved in the regulation of many developmental and physiological processes in chordates. Recently, evidence showing its presence and function in invertebrate deuterostomes and protostomes indicated the early evolutionary origin and conservation of the RA developmental machinery, with a key role also in neural differentiation. Moreover, it is known that retinoids can influence pattern specification in polyps of the hydroid Hydractinia echinata. The planula larvae of the hydrozoan Clava multicornis are characterized by a complex nervous system formed by a frontal neural plexus composed by two distinct peptidergic cell populations with antero‐posterior organization: a first, anterior‐most GLWamide immunoreactive (GLW‐IR) population and an RFamide immunoreactive (RF‐IR) cell belt just posterior to the first population. In contrast to most swimming planulae, C. multicornis larvae display a smooth gliding movement on the substrate, characterized by alternate bending of the anterior pole. We tested the effects of RA and of a RA antagonist on C. multicornis development by analyzing the nervous system organization and the photoresponsive behavior of larvae exposed to RA during their embryogenesis. After the exposure, the nervous system became completely disorganized, leading to the displacement of RFamide‐IR cells. Moreover, RA‐treated larvae did not exhibit the typical phototropic behavior of control specimens. Our results suggest that RA can alter the normal development of nervous elements in this hydroid species, supporting the hypothesis that the morphogenetic activity of RA predates the origin of chordates.

Shallow‐water benthic hydroids from the Maltese Islands (Central Mediterranean)

AbstractForty species of benthic hydroids, belonging to 15 families and 21 genera, were found in a collection, obtained by SCUBA diving, from the Maltese Islands. Paradoxically for the well studied Mediterranean region, the hydroid fauna of these islands is virtually unexplored. Of 40 species, 33 were identified to species level, with 28 of them reported for the first time for the study area. Hydractinia monocarpa is recorded for the first time in the Mediterranean Sea, and a presumed new species of the genus Clytia has been found. The most speciose families are Campanulariidae with 10 species (25%), Aglaopheniidae with six species (15%) and Sertulariidae with five species (12%). Aglaophenia and Clytia are the most diverse genera, both with six species (15%). A problem with respect to subspecies of Sertularella ellisi is resolved based on nematocyst observations. In terms of geographic distribution, eight species (24%) are endemic to the Mediterranean Sea, this number increases to 16 species (48%) when including those restricted to Mediterranean and nearby Atlantic waters, whereas the remaining species have wider distributions.

Which Halitholus species (Cnidaria: Hydrozoa) inhabits the Arctic and high boreal Atlantic waters?

AbstractThe binomen Perigonimus yoldiaearcticae Birula was established (as Perigonimus yoldiae‐arcticae) for a hydroid species found predominantly on shells of the mollusk Yoldia arctica (now Portlandia arctica) in the White and Kara Seas. Its original description was incomplete, no medusa stage was described, no specific type locality was specified, and we know of the existence of no type specimens. Birula's nominal species cannot be distinguished from several other pandeids occurring at high latitudes of the northern hemisphere, and we regard P. yoldiaearcticae as a nomen dubium. By contrast, Halitholis cirratus Hartlaub, 1913 was founded on medusae obtained at Spitzbergen and in the Barents and Baltic Seas, and its presumed hydroid discovered in the Baltic (the latter a region with no other known species of pandeid medusae). We examined material referable to H. cirratus from the Kara Sea, including both medusae and hydroids (on Portlandia arctica), and conclude that this is the species inhabiting the Arctic Ocean and the high boreal Atlantic.

First record of the hydroid Eudendrium carneum (Cnidaria: Hydrozoa: Hydroidolina) in Indian waters

Work on hydroids from India is scanty, and the distribution of hydroids in India is therefore largely unknown. Thornely (1916) recorded 17 species of hydroids from Gujarat State. Mammen (1963, 1965a, b) contributed taxonomic information on almost 126 species of hydroids from southern India. Venugopalan & Wagh (1986) carried out work on benthic hydroids with ten records from the Maharashtra coast. Among hydroids, the widespread genus Eudendrium in particular is infrequently reported from India. Mammen (1963) reported Eudendrium capillare Alder, 1856 from southern India, the only known record of this genus from India. Eudendrium carneum Clarke, 1882 is a new species record in Indian waters from Poshitra, Gujarat. The present record thus assumes significance.

Эстафетный способ перемещения гидроплазмы в колониях гидроидных полипов

In this study, we continued the investigation of the distribution system of colonial hydroids in the course of its development, starting with its emergence during the planula metamorphosis and ending with the formed colony. The hydroplasmic stream system of two species of colonial hydroids--Perigonimus abyssi G.O. Sars, 1874, and Stauridia producta Wright, 1858--was studied. W found that the main principle by which hydroplasma moves in these colonies, which form no shoots, is the relay-race from one hydranth to another through a stolon fragment connecting them or directly from one hydranth to the next one, etc. W show that the efficiency of the conducting (distribution) system does not depend on the level of complexity of the colonial structure. The results of this study confirm the absence of general colonial processes of integration and self-regulation in hydroid polyps.

New records of Hydroides (Polychaeta: Serpulidae) from Guam, Mariana Islands

Three species of the serpulid genus Hydroides are described and illustrated herein. Hydroides bannerorum and H. albiceps are newly recorded to Guam in the Mariana Islands. Hydroides perezi is also described and illustrated from specimens collected in Pago Bay. We provide notes on the opercular ontogenetic variation of H. albiceps to help clarify possible confusions with opercula of similar taxa.

First report of the marine hydroids Eudendrium glomeratum, E. merulum and Garveia grisea (Cnidaria: Hydrozoa) from the Moroccan Atlantic coast

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.

Molecular Evidence Shows Low Species Diversity of Coral-Associated Hydroids in Acropora Corals

A novel symbiosis between scleractinians and hydroids (Zanclea spp.) was recently discovered using taxonomic approaches for hydroid species identification. In this study, we address the question whether this is a species-specific symbiosis or a cosmopolitan association between Zanclea and its coral hosts. Three molecular markers, including mitochondrial 16S and nuclear 28S ribosomal genes, and internal transcribed spacer (ITS), were utilized to examine the existence of Zanclea species from 14 Acropora species and 4 other Acroporidae genera including 142 coral samples collected from reefs in Kenting and the Penghu Islands, Taiwan, Togian Island, Indonesia, and Osprey Reef and Orpheus Island on the Great Barrier Reef, Australia. Molecular phylogenetic analyses of the 16S and 28S genes showed that Acropora-associated Zanclea was monophyletic, but the genus Zanclea was not. Analysis of the ITS, and 16S and 28S genes showed either identical or extremely low genetic diversity (with mean pairwise distances of 0.009 and 0.006 base substitutions per site for the 16S and 28S genes, respectively) among Zanclea spp. collected from diverse Acropora hosts in different geographic locations, suggesting that a cosmopolitan and probably genus-specific association occurs between Zanclea hydroids and their coral hosts.

Deep-water Hydrozoa (Cnidaria: Medusozoa) in the Sea of Japan, collected during the 51st Cruise of R/V Akademik M.A. Lavrentyev, with description Opercularella angelikae, sp. nov.

A report is given about Hydrozoa collected at depths between 455 and 3666m in the Sea of Japan during the Russian-German expedition on R/V Akademik M.A. Lavrentyev. Ten species were found, with four of them being typical bathyal–abyssal and abyssal zones. A new species, Opercularella angelikae, is described, and it was the dominant hydroid in samples from 970 to 3660m. Four eurybathic species characteristics of the Sea of Japan were sampled between 455 and 582m. Abyssal (pseudoabyssal after Andriashev, 1979) hydroid fauna in the Sea of Japan is reported. The hypothesis that an exclusively deep-water fauna is lacking in abyssal regions of the Sea of Japan is disputed. The author's personal opinion considered concerning the borders of 1000m between shallow and deep hydrozoan species in the Sea of Japan.

Biodiversity of Prokaryotic Communities Associated with the Ectoderm of Ectopleura crocea (Cnidaria, Hydrozoa)

The surface of many marine organisms is colonized by complex communities of microbes, yet our understanding of the diversity and role of host-associated microbes is still limited. We investigated the association between Ectopleura crocea (a colonial hydroid distributed worldwide in temperate waters) and prokaryotic assemblages colonizing the hydranth surface. We used, for the first time on a marine hydroid, a combination of electron and epifluorescence microscopy and 16S rDNA tag pyrosequencing to investigate the associated prokaryotic diversity. Dense assemblages of prokaryotes were associated with the hydrant surface. Two microbial morphotypes were observed: one horseshoe-shaped and one fusiform, worm-like. These prokaryotes were observed on the hydrozoan epidermis, but not in the portions covered by the perisarcal exoskeleton, and their abundance was higher in March while decreased in late spring. Molecular analyses showed that assemblages were dominated by Bacteria rather than Archaea. Bacterial assemblages were highly diversified, with up to 113 genera and 570 Operational Taxonomic Units (OTUs), many of which were rare and contributed to <0.4%. The two most abundant OTUs, likely corresponding to the two morphotypes present on the epidermis, were distantly related to Comamonadaceae (genus Delftia) and to Flavobacteriaceae (genus Polaribacter). Epibiontic bacteria were found on E. crocea from different geographic areas but not in other hydroid species in the same areas, suggesting that the host-microbe association is species-specific. This is the first detailed report of bacteria living on the hydrozoan epidermis, and indeed the first study reporting bacteria associated with the epithelium of E. crocea. Our results provide a starting point for future studies aiming at clarifying the role of this peculiar hydrozoan-bacterial association.

Multi-domain GFP-like proteins from two species of marine hydrozoans

Proteins homologous to Green Fluorescent Protein (GFP) are widely used as genetically encoded fluorescent labels. Many developments of this technology were spurred by discoveries of novel types of GFP-like proteins (FPs) in nature. Here we report two proteins displaying primary structures never before encountered in natural FPs: they consist of multiple GFP-like domains repeated within the same polypeptide chain. A two-domain green FP (abeGFP) and a four-domain orange-fluorescent FP (Ember) were isolated from the siphonophore Abylopsis eschscholtzii and an unidentified juvenile jellyfish (order Anthoathecata), respectively. Only the most evolutionary ancient domain of Ember is able to synthesize an orange-emitting chromophore (emission at 571 nm), while the other three are purely green (emission at 520 nm) and putatively serve to maintain the stability and solubility of the multidomain protein. When expressed individually, two of the green Ember domains form dimers and the third one exists as a monomer. The low propensity for oligomerization of these domains would simplify their adoption as in vivo labels. Our results reveal a previously unrecognized direction in which natural FPs have diversified, suggesting new avenues to look for FPs with novel and potentially useful features.

Some hydroids (Hydrozoa: Hydroidolina) from Dampier, Western Australia: annotated list with description of two new species

Abstract Jeanette E. Watson, 2012. Some hydroids (Hydrozoa: Hydroidolina) from Dampier, Western Australia: annotated list with description of two new species. Memoirs of Museum Victoria 69: 355–363. Eleven species of hydroids including two new (Halecium corpulatum and Plumularia fragilia) from a depth of 50 m, 50 km north of Dampier, Western Australia are reported. The tropical hydroid fauna of Western Australia is poorly known; species recorded here show strong affinity with the Indonesian and Indo–Pacific region.

Evolution of Nemertesia hydroids (Cnidaria: Hydrozoa, Plumulariidae) from the shallow and deep waters of the NE Atlantic and western Mediterranean

Moura, C. J., Cunha, M. R., Porteiro, F. M., Yesson, C. &amp; Rogers, A. D. (2011) Evolution of Nemertesia hydroids (Cnidaria: Hydrozoa, Plumulariidae) from the shallow and deep waters of the NE Atlantic and Western Mediterranean. —Zoologica Scripta, 41, 79–96.Hydroid species from the genus Nemertesia develop some of the largest and most complex hydrozoan colonies. These colonies are abundant and ecologically important in both shallow and deep waters worldwide. Here, we analyse the systematics of most Nemertesia species from the NE Atlantic and Mediterranean using morphology and phylogenetic inferences of 16S rRNA haplotype data. Phylogeographical analysis revealed multiple movements of taxa to and from the Mediterranean after the Messinian salinity crisis through shallow and deep waters. The nominal species Nemertesia belini and Nemertesia antennina revealed multiple genetic lineages representing cryptic species diversity. Molecular phylogenetic evidence was supported by consistent phenotypic differences between lineages, and three and seven putative species were resolved within the N. belini and N. antennina complexes, respectively. Three putative species of the N. antennina complex found at different seamounts of Azores grouped in a clade clustered amongst the other four cryptic species present at neighbouring bathyal localities of the Gulf of Cadiz. These cryptic species, mostly from the deep sea, form a clade distantly related to the typical N. antennina from European coastal waters. Depth or environmental correlates of depth seem to influence the reproductive strategies of Nemertesia colonies and ultimately speciation. In particular, speciation of these hydroids must have been influenced by hydrography, habitat heterogeneity, isolation by distance and larval dispersal capacity. The deep sea is shown as an important environment in the generation and accumulation of lineages that may occasionally invade coastal waters in the NE Atlantic. Glacial cycles of cooling, along with changes in sea level, and eradication of some coastal faunas likely facilitated speciation and evolutionary transitions from deep to shallow waters.

Ascidians in the succession of marine fouling communities

Approximately 200 grey PVC settlement plates were hung along at sites along the Dutch coast at a depth of 1 meter. The cover of each species that could be identified on the plates was recorded every three months from March 2009 to March 2010 to study the role of native versus non-native ascidians in the succession of marine fouling communities. Three native ascidian species, Ciona intestinalis, Ascidiella aspersa and Botryllus schlosseri, and five species of cryptogenic and/or non-native origin, Molgula socialis, Styela clava, Diplosoma listerianum, Botrylloides violaceus and Didemnum vexillum, were recorded. After the Cnidaria, Ascidiacea were found to be the group that explained most of the differences found in species communities on settlement plates at different stages in the succession. Regardless of the fact that non-native ascidian species were very abundant at times, their role in the succession of the studied marine fouling communities appears to be limited. After the polyp stage of the moon jelly Aurelia aurita and hydroid species of the genus Obelia, the two native ascidian species Ciona intestinalis and Ascidiella aspersa explained most of the differences that were found between the successive stages in the fouling communities. In general, the three native ascidian species appeared to determine the succession of the fouling communities more than the five cryptogenic and/or nonnative ascidian species. Whether this is linked to species being either native or non-native is questionable however. The various ascidian species differed strongly in the period of settlement, the ability to settle on prior settlers and the ability to survive the winter. The non-native ascidians settled mostly in June to December, while the native ones settled from March to December. Although the native ascidians M. socialis and B. schlosseri were found to be restricted in their settlement by the presence of prior settlers, the non-native species B. violaceus and D. vexillum were not. Native and non-native ascidian species survived the winter equally well. Native C. intestinalis and A. aspersa and non-native B. botrylloides and D. vexillum were most successful in surviving winter water temperatures of just below 0°C. Thus the results of this study, based on one year of data, suggest that the roles of ascidian species in the succession of fouling communities vary, and that being native or non-native is not necessarily linked to the degree to which species influence the development of marine fouling communities. Their individual seasonality, abilities to overgrow prior settlers and survival of winter temperatures appear to be more important.

Global and local patterns in the use of macrophytes as substrata by hydroids (Hydrozoa: Anthoathecata and Leptothecata)

Hydroids are one of the most important animal groups colonizing marine macrophytes. This study presents the diversity of hydroid species in plant substrate samples taken from three points of the São Sebastião Channel, southeastern Brazil. The selectivity level of each hydroid species was inferred from the number of its occurrences on each species of macrophyte. Red and brown algae, especially species belonging to the genera Galaxaura and Sargassum, respectively, presented the highest diversity index of epiphytic hydroids. The epiphytic hydroid fauna of São Sebastião Channel is mostly comprised of opportunistic species, presenting low substrate selectivity. A broader cluster analysis of the epiphytic hydroid fauna reported in several studies around the world suggests that hydroids are primarily related to their geographical distribution and may be secondarily related to the lineages of macrophytes.

Primer registro del género Lytocarpia Kirchenpauer, 1872 (Cnidaria: Hydrozoa: Leptothecata), para Cuba

Se registran por vez primera vez para el archipiélago cubano el género Lytocarpia y la especie L. distans. Este es el más somero de los hallazgos de esta especie de hidrozoo.

A new species of Zanclea (Cnidaria: Hydrozoa) associated with scleractinian corals from Okinawa, Japan

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 &amp; 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.