Benthic hydroids (Cnidaria,Hydrozoa) from the Balleny Islands (Antarctica)

Twenty-two species of benthic hydroids, belonging to ten families and 14 genera, were found in a hydroid collection obtained in the Balleny Islands during the BioRoss expedition with the NIWA research vessel Tangaroa in 2004. Twenty of those species constitute new records for the Balleny Islands, raising the total number of known species in the area to 25. Most are members of the subclass Leptothecata, although the subclass Anthoathecata is also relatively well represented. Kirchenpaueriidae and Sertulariidae constitute families with the greatest numbers of species in the collection, with five species (20%) each. Oswaldella with five species (20%) and Staurotheca with four (16%), were the most diverse genera. Twelve species (63%) are endemic to Antarctic waters, most of them with a circum-Antarctic distribution, and 17 (89%) are restricted to Antarctic or Antarctic/sub-Antarctic waters. Although the Balleny Islands hydroid fauna seems to be a typical Antarctic assemblage, it has some striking peculiarities, namely the absence or low representation of some typical and widespread Antarctic genera (Antarctoscyphus and Schizotricha/Symplectoscyphus, respectively).     

Benthic hydroids (Cnidaria, Hydrozoa) from off Bouvet Island (Antarctic Ocean)

Twenty-seven species of benthic hydroids have been found in a small collection from off Bouvet Island (Antarctic Ocean). The material was obtained during the XXI/2 German Antarctic expedition with R.V. Polarstern 2003–2004. Of the 27 species collected, 21 were unknown from those waters. Consequently, the number of known species of benthic hydroids from the area has risen to 32, representing a high diversity location for this group in the Southern Ocean considering the sampling effort made. All species, including those previously known from Bouvet waters, are considered with respect to geographical distribution.The present work is an addition to the special issue “Macrobenthic studies at Bouvet island”, presenting work carried out from on board RV Polarstern in 2003/2004 and published in Polar Biology 29 (2006)     

Benthic hydroids (Cnidaria: Hydrozoa) from Peter I Island (Southern Ocean, Antarctica)

Twenty-three species of benthic hydroids, belonging to eight families and 13 genera, were found in a hydroid collection from Peter I Island, collected during both the Bentart 2003 and Bentart 2006 Spanish expeditions with BIO Hespérides in 2003 and 2006. Fourteen out of the 23 species constitute new records for Peter I Island, raising the total number of known species in the area to 30, as also do seven out of the 13 genera. The majority of the species are members of the subclass Leptothecata; the subclass Anthoathecata being scarcely represented. Sertulariidae is the family with the greatest number of species in the collection, with eight species (35%), followed by Lafoeidae with five (22%). Symplectoscyphus with four species (17%) and both Antarctoscyphus and Halecium with three (13%), including H. frigidum sp. nov., were the most diverse genera. Twenty species (ca. 77%) are endemic to Antarctic waters, either with a circum-Antarctic (11 species, ca. 42%) or West Antarctic (9 species, ca. 35%) distribution. Twenty-four (ca. 92%) are restricted to Antarctic or Antarctic/sub-Antarctic waters; only two species have a wider distribution. Peter I Island hydroid fauna is composed of typical representatives of the Antarctic benthic hydroid fauna, though it is characterized by the low representation of some of the most diverse and widespread Antarctic genera (Schizotricha and Staurotheca).     

Benthic hydroids (Cnidaria: Hydrozoa) from the Spanish Antarctic expedition Bentart 95

A total of 61 species of hydroids, belonging to 13 families and 23 genera, were found during the Spanish Antarctic expedition Bentart 95 with the RV Hespérides. Ten of the species were identified only to generic level. The dominance of the subclass Leptothecatae, with 57 species, was remarkable. The remaining four species belong to the subclass Anthoathecatae. By far the most diverse family was the Sertulariidae, with 25 species (41%), followed by Haleciidae with nine species (15%) and Kirchenpaueriidae with six (10%). The family Plumulariidae, represented by one species of Nemertesia, is recorded for the first time from Antarctic waters. Eudendrium scotti, Perarella clavata and Symplectoscyphus hero are each recorded for the second time. Symplectoscyphus with 11 species was the dominant genus. Almost 60% of the species diversity is concentrated in just a little more than the 20% of genera. Nearly 70% of the species are endemic to Antarctic waters and 90% of them are restricted to Antarctic or Antarctic/sub-Antarctic waters.     

Benthic hydroids (Cnidaria: Hydrozoa) from the Bransfield Strait area (Antarctica) collected by Brazilian expeditions,with the description of a new species

A total of 36 species of benthic hydroids, belonging to nine families and 16 genera, were found in the hydroid collection gathered during the Brazilian Antarctic expeditions PROANTAR III and IV. Seven of the species were identified only to generic level. There is a clear dominance of the subclass Leptothecatae with 33 species. By far the most diversified family was the Sertulariidae, with 16 species (44%). Symplectoscyphus with eight species, including Symplectoscyphus magnificus sp. nov., is the most diversified genus. Almost 70% of the species diversity is restricted to just six genera (38%). Sixty-eight percent of the species is Antarctic endemics and 86% is restricted to Antarctic or Antarctic/sub-Antarctic waters. Eudendrium antarcticum and Amphisbetia operculata are recorded for the first time from Antarctic waters.     

Evolution and taxonomy in capitate hydroids and medusae (Cnidaria: Hydrozoa)

A cladistic analysis of Capitata groups the families in four suborders based on medusa characters (such as manubrium morphology, position of gonads, and position and number of marginal tentacles) and hydroid characters (such as presence or absence of an oral tentacle whorl, and the different development of the tentacles of the oral and aboral whorls). On the family and generic levels, the revision results in changes which unite the separate hydroid and medusa taxonomic systems, defining genera which are not based on characters solely relating to the reduction of medusae to fixed gonophores. In those families where the reduction of the medusa can be analysed, it is shown that the reduction occurred after all synapomorphies defining the genera had evolved and usually affected individual species within a genus rather than the original species from which the other species in the genus evolved. This supports the view that medusa reduction is not in itself a valid generic character. A discussion of the theories of 'inconsistent' or 'mosaic' evolution concludes that no difference in evolutionary rate or degree of specialization can be demonstrated among taxa with free medusae and taxa with gonophores.     

DNA barcoding reveals cryptic diversity in marine hydroids (Cnidaria, Hydrozoa) from coastal and deep-sea environments

Fifty-six sequences of the mitochondrial 16S RNA gene were generated for hydroids, belonging to six nominal families — Eudendriidae, Lafoeidae, Haleciidae, Sertulariidae, Plumulariidae and Aglaopheniidae — collected from bathyal environments of the Gulf of Cadiz (22 haplotypes), Greenland (1 haplotype), Azores (1 haplotype), the shallow waters of the UK (17 haplotypes) and Portugal (2 haplotypes). When combined and analysed with 68 additional sequences published in GenBank, corresponding to 63 nominal species of these families (nine species in common between the GenBank sequences and those presented by the authors), cryptic species were detected (e.g. two species of Nemertesia and other of Lafoea ), as well as apparent cases of conspecificity (e.g. Nemertesia antennina and N. perrieri and Aglaophenia octodonta , A. pluma and A. tubiformis ). Other taxonomic inconsistencies were found in the data including cases where species from different genera clustered together (e.g. Sertularia cupressina , Thuiaria thuja , Abietinaria abietina and Ab. filicula ). The mitochondrial 16S rRNA proved to be a useful DNA 'barcode' gene for hydroids, not only allowing discrimination of species, but also in some cases of populations, genera and families, and their intra- or interphylogenetic associations. Although still under-represented in public data bases, the 16S rRNA gene is starting to be used frequently in the study of hydroids. These data provide powerful complementary evidence for advancing our understanding of hydrozoan systematics.     

First record of sympagic hydroids (Hydrozoa,Cnidaria) in Arctic coastal fast ice

We report on the first record of interstitial cnidarians in sea ice. Ice core samples were collected during eight field periods between February 2003 and June 2006 in the coastal fast ice off Barrow, Alaska (71°N, 156°W) at four locations. A total of 194 solitary, small (0.2–1.1 mm) elongated specimens of a previously unknown interstitial hydroid taxon were found. By cnidome composition and the occurrence of a highly retractable pedal disc formed by epidermal tissue only, the specimens are tentatively assigned to representatives of the family Protohydridae, subclass Anthomedusae. The hydroids were found almost exclusively in the bottom 10 cm-layer (at the ice–water interface) of 118 ice cores, with abundances ranging from 0 to 27 individuals per core section (0–4,244 ind m⁻²) and a grand mean of 269 ind m⁻² in bottom 10 cm-layer sections. Abundances were lower in December and late May than in months in between with considerable site variability. A factor analysis using 12 variables showed that hydroid abundance correlated highest with abundances of copepod nauplii and polychaete juveniles suggesting a trophic relationship.     

Unusual trophic strategies of Hydractinia angusta (Cnidaria, Hydrozoa) from Terra Nova Bay, Antarctica

Hydractinia angusta Hartlaub, 1904 has been recorded at Terra Nova Bay (Ross Sea, Antarctica) as epizoic on shells of the Antarctic scallop Adamussium colbecki. The species can exploit different trophic resources: first, polyps are able to detach and ingest tube feet and pedicellariae from the sea urchins Sterechinus neumayeri, grazing on the scallop shell, and second, they also eat masses of benthic diatoms settled among the hydrorhiza of the colony. The particular relationship observed between the hydroid and one of the most common Antarctic sea urchins may prevent or reduce the damage to A. colbecki shells, otherwise caused by the grazing of sea urchins on the algal film of the upper valve of the scallops. H. angusta is the first known species of hydroid that exploits prey several times its own size and the second that does not ingest entire prey but portions of them. The use of benthic diatoms as a food resource has previously been documented for the sub-Antarctic marine hydroid Silicularia rosea. Accepted: 20 December 1999     

The distribution of hydroids (Cnidaria, Hydrozoa) from micro- to macro-scale: Spatial patterns on habitat-forming algae

Scaling up from local, short-term experiments to larger-area and longer-term ones is crucial to address the role of scale in ecology. Few studies, however, examined large-scale spatial variability in the distribution and abundance of marine organisms, with rare attempts to directly compare spatial variation at local (centimetres-metres) vs. regional (1000's of kilometres) scale. Here, we used a hierarchical design to describe the spatial distribution of the hydroids epiphitic of the brown alga Cystoseira amentacea, a habitat-forming species that provides a continuous, extensive settling substrate at regional scale along the rocky coasts in the Mediterranean Sea. This continuity provides the potential to deal with scale-related variability, increasing area of investigation without adding differences deriving from habitat heterogeneity or changes in topographic complexity. Hydroids were selected for their abundance and for their life cycle features (rapid growth, small body size, early sexual or asexual reproduction and short life span), allowing rapid responses to changes in environmental conditions. The aim of this study was to analyse whether the structure of hydroid assemblages living on C. amentacea had a consistent pattern of variation among three portions of the algal thallus (i.e., basal, middle, and distal) across a spectrum of scales and whether having or not a pelagic stage could exert a significant influence on the distribution patterns of the species. A total of 32 species were identified. Multivariate analyses showed that hydroid colonization of Cystoseira occurs differently along each thallus, with patterns of variation in the structure of assemblages differing at an even smaller spatial scale than that of single plants. However, such differences varied from patch to patch. Among the 14 species identified as “important” to define the hydroid assemblage inhabiting Cystoseira, only one (Clytia hemisphaerica) has free medusae, the other species reproducing by fixed gonophores or by short-lived medusoids. Univariate analysis showed significant differences among portions of thalli in terms of spatial variability at the various scales investigated, thus suggesting that patterns of multivariate variation along the three portions of thalli might vary across scale. Overall, our results suggest that patterns of distribution of hydroids along C. amentacea thalli significantly vary across spatial scales but that the observed differences can be hardly interpreted on the basis of life-cycle patterns.     

On two new species of Oswaldella Stechow, 1919 (Cnidaria, Hydrozoa) from Bransfield Strait (Antarctica)

Two species of the genus Oswaldella Stechow, 1919 new to science (Oswaldella crassa sp. nov. and O.␣curiosa sp. nov.) were studied. Both species are described and figured; their systematic position amongst the remaining species of the genus is discussed. The material originates from the Bransfield Strait area (Antarctica) and was collected during the United States Antarctic Research Program with R.V. Eltanin. A comparative table listing the main features of the known species of Oswaldella is presented. Finally, a general survey of geographical and bathymetrical distribution of the known species of Oswaldella is given. Received: 8 October 1997 / Accepted: 2 February 1998     

Macrofaunal communities on the continental shelf and slope of the southeastern Weddell Sea,Antarctica

Summary During the third leg of the European Polarstern Study (EPOS leg 3) in the austral summer season 1989, benthic macrofaunal communities were sampled from the Elephant Island area (61° southern latitude) and from Kapp Norvegia (71° southern latitude) to Halley Bay (75°30 southern latitude) using a commercial bottom trawl and an Agassiz trawl. Thirty-six trawl samples from a depth range of about 200–2,000 m were considered, with most of the samples being from the shelf and upper slope. Multivariate analysis techniques (clustering and TWIN-SPAN) discriminated between an eastern and a southern community in which parallel subgroups can be distinguished at increasing distance from the ice shelf.Data presented here were collected during the European Polarstern Study (EPOS) sponsored by the European Science Foundation     

Two new species of Staurotheca Allman, 1888 (Cnidaria, Hydrozoa, Sertulariidae) from the Scotia Sea (Antarctica)

Two new species of the genus Staurotheca Allman, 1888 have been studied (Staurotheca cornuta sp. nov. and Staurotheca multifurcata sp. nov). The material, from the Scotia Ridge area (Antarctica), was collected in 1986/1987 by the Spanish Antarctic expedition “Antártida 8611”. Each species is described and figured, and its systematic position among allied species is noted. Data concerning autecology and geographical distribution for each species are given. A comparative table listing the main features of the known species of the genus is included. Finally, a general survey of the geographical and bathymetrical distribution of the known species of the genus is presented. Accepted: 1 September 1998     

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. & 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.     

Epiphytic hydroids (Cnidaria,Hydrozoa) contribute to a higher abundance of caprellid amphipods (Crustacea,Peracarida) on macroalgae

The behaviour of returning Salmo salar (Linnaeus, 1758) approaching, and attempting to pass low-head weirs remains relatively unknown. A radio telemetry array was created at a low-head weir to enable the behaviour of S. salar (n = 120) to be observed as they approached and attempted to pass the barrier. The majority of fish successfully passed the barrier on their first or second attempt, some individuals required 11 attempts prior to successful passage occurring. Mean delay at the barrier per fish was 47.8 h (±SD 132.0 h), range 15 min to 31 days. Passage success on a fish’s initial attempt was significantly predicted by the amount of searching a fish undertook, fork length, and fat content. Fish were more likely to have a successful first passage attempt if it was smaller with a low fat content and exerted a greater effort in searching for a passage channel. Small-scale barriers cause delays and increased energy expenditure in migrating fish. Barriers may be creating an anthropogenic selection pressure for traits which enable passage success. The impact of a delay at a barrier and increased energy expenditure on reproduction and gonad development remains unknown but is likely to be negatively impacted by instream anthropogenic structures.     

Cholinergic mechanism in Liriope tetraphylla (Cnidaria, Hydrozoa)

Crude whole body homogenates of Liriope tetraphylla exhibit a cholinesterase particularly active on acetylthiocholine but not on butyrylthiocholine. The acetylthiocholine hydrolysis is completely blocked by neostigmine. The Michaelis-Menten constant for acetylthiocholine is 0.14 mM. The pharmacological analysis of the responses to the choline esters nicotine and atropine suggests the involvement in Liriope tetraphylla of a cholinergic mechanism in the pointing reflex. Butyrylcholine, nicotine and atropine (but not muscarinic agonists) caused the contraction of the subumbrellar radial muscles. The effects of atropine were dose-dependent and were depressed in competition with muscarinic agonists. MgCl2 interfered with the action of atropine. The results were explained by suggesting the existence, at least at the neuromuscular junction, of excitatory (nicotinic) and inhibitory (muscarinic) pre-synaptic receptors modulating the release of the (unknown) transmitter acting post-synaptically.     

Six new species of marine Tubificidae (Oligochaeta) from the continental shelf off Peru

Six species of marine tubifieids are described from the continental shelf off Peru. Two of them are members of the gutless genus Olavius Erséus, 1984 (subfamily Phallodrilinae). Olavius bullatus sp.n. possesses 2 pairs of large penial setae in voluminous copulatory sacs, tiny atria, and spermathecal pores in line with dorsal setae. Olavius crassitunicatus sp.n. is characterized by small atria with thin muscular layer, spermathecae with short ducts, opening dorso-laterally, and lack of penial setae. Four species arc members of the subfamily Limnodriloidinae. Limnodriloides busilicus sp.n. belongs to the appendiculatus-group (sensu Erséus). It is discriminated by somatic setae with subdental ligaments, and its voluminous elongate prostatic pads. Limnodriloides clavellatus sp.n. is distinguished from its congeners by a peculiar bulge in the cavity of each atrial ampulla, and spermatozeugmata imbedded in the walls of the spermathecae. Tectidrilus intermixtus sp.n. is similar to T. bori (Righi & Kanner, 1979); it is distinguished from the latter by having trisetal bundles in segment V or V-VI and by lacking copulatory glands. Marcusaedrilus peruanus sp.n. is characterized by nongranulated atrial ducts and bipartite spermathecae.     

Species diversity and distribution within the deep-sea nematode genus Acantholaimus on the continental shelf and slope in Antarctica

Species diversity and distribution—in relation with biogeography, bathymetry and environmental characteristics—within the genus Acantholaimus were investigated on the shelf and slope (182–2,009 m) in the Weddell Sea (Kapp Norvegia and Vestkapp) and near the Antarctic Peninsula (Drake Passage and Bransfield Strait). The occurrence of the otherwise typical deep-sea genus Acantholaimus in high densities and diversity on the continental shelf is a unique feature of the Southern Ocean. Fifty-five Acantholaimus species (morpho-types) were distinguished in our study area, of which 39 were found on the shelf. The Acantholaimus communities were characterised by a high number of congeneric species and the presence of many rare species, similar to typical deep-sea communities. Fourteen species had a distribution extending from the shelf to the lower slope. High local and regional diversity was obvious and a considerable level of endemism was suggested. A negative impact of chlorophyll a concentrations, reflecting the availability of phytoplankton, was found on the Acantholaimus densities and species diversity.