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).     

Cleansing mechanisms of caprellid amphipods (Crustacea) from North America

There are three cleaning mechanisms utilized by intact caprellids separable by the body region being cleansed: antennae, mouthparts, and the remainder of the body. Antennal cleansing is a function of the first gnathopods and maxill'ipeds, mouthpart cleaning utilizes all of the mouthparts, and body cleansing relies solely on the first gnathopods. Behaviorally, filter feeders groom and feed approximately as much as predators, but filter feeders cleanse their entire body whereas predators primarily cleanse only both pair of antenna. The possibility that filter feeding was evolutionarily derived from cleaning activities is proposed.     

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)     

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.     

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).     

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.     

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.     

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.     

Hyperiid amphipods (Crustacea: Peracarida) in relation to a cold-core ring in the Gulf of Mexico

The species composition, distribution, and abundance of the hyperiid amphipods collected in March 1993 across a Gulf of Mexico cold-core ring (CCR) were analyzed. Day and night samples were collected by oblique tows (100 m to surface) with a plankton net. Hyperiids were represented by 56 species, 21 of which have not been recorded previously in gulf waters. The local oceanic community differs from that reported from adjacent neritic and neritic-oceanic areas of the Northwestern Tropical Atlantic. Overall, hyperiids were more abundant within (59% of total catch in org./1000 m³) than outside the CCR (41%). All inside CCR stations were sampled at night. Night outside vs. night inside CCR hyperiid faunas showed important differences in terms of species richness, composition and density. Cluster analysis indicated that day sta. 5 on the edge but outside the CCR was more similar to those stations inside the CCR (nighttime samples) than to the other daytime samples. Moreover, all the stations outside the CCR were clustered together independently of their day or night origin. It is suggested that the differences found were more related to differential conditions related to the CCR than to diel vertical migration. The analysis of three congeneric pairs with inverse CCR-related abundance and with known or inferred migratory patterns strengthened the idea that these pairs are probably separated by thermal preferences; also, their vertical migratory patterns seem to be abnormal inside the CCR. A relatively higher concentration of immature stages inside the CCR supports the idea that the enriched CCR waters constitute areas of increased production. Furthermore, this higher productivity enhances the chances of hyperiids to find their hosts, the gelatinous zooplankters, which are also more abundant inside the CCR.     

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.     

On Antarctoscyphus (Cnidaria, Hydrozoa), a new genus of antarctic hydroids and the description of two new species

A new genus of the hydroid family Sertulariidae is established. Several species formerly assigned to the genus Symplectoscyphus Marktanner-Turneretscher, 1890 are included. A review of those species is given, including their main features along with some remarks. Two species new to science are added; the material of those species was collected in the Scotia Sea by the Spanish Antarctic Expedition “Antártida 8611”. Present autecological data are discussed.     

Invasive species contribute to biotic resistance: negative effect of caprellid amphipods on an invasive tunicate

As the number of introductions of non-indigenous species (NIS) continues to rise, ecologists are faced with new and unique opportunities to observe interactions between species that do not naturally co-exist. These interactions can have important implications on the invasion process, potentially determining whether NIS become widespread and abundant, survive in small numbers, or fail to establish and disappear. Although many studies have naturally focused on the interactions between NIS and native species to examine their effects and the biological resistance of the recipient community to invasion, few have examined the effects that NIS have on each other. In some cases, interactions can facilitate the invasion process of one or both species (i.e., “invasional meltdowns”), but competition or predation can lead to negative interactions as well. The introduction of the vase tunicate, Ciona intestinalis, in Prince Edward Island (Canada) has harmed mussel aquaculture via heavy biofouling of equipment and mussels. Through both a broad-scale survey and small-scale field experiments, we show that Ciona recruitment is drastically reduced by caprellid amphipods, including the NIS Caprella mutica. This study provides an exciting example of how established invasive species can negatively impact the recruitment of a secondary invader, highlighting the potential for non-additive effects of multiple invasions.     

The distribution of hyperiid amphipods (Crustacea:Peracarida) in relation to warm-core eddy J in the Tasman Sea

Hyperiid amphipods were sampled in and around warm-core eddyJ in the Tasman Sea off eastern Australia in August, Septemberand October 1979. Samples were taken at night to a depth of400 m with a midwater trawl (RMT-8). In all, 22 798 hyperiidsrepresenting 38 species and 10 families were collected. Sevenspecies, individually found in numbers >4% of the total amphipodpopulation, together contributed 87.1% to the total. Of these,Scina crassicornis, Phronima sedensataria, P.atlantica, Phrosinasemilunata, Primno johnsoni and Brachyscelus crusculum wereusually found in highest numbers outside the eddy. Streetsiachallengeri was the only abundant species with significantlyhigher numbers inside the eddy. Outside the eddy, samples werecharacterized by large numbers of few species, whereas abundanceswere more evenly distributed between species inside the eddy.The size distributions of two abundant species (B.crusculumand S.challengeri) were not significantly different betweenthe inside and outside of eddy J. Hyperiid faunal patterns wereassociated with depth and temperature (August), position withrespect to the eddy (September, October) and the presence ofgelatinous zooplankton (September, October).     

Associations between gelatinous zooplankton and hyperiid amphipods (Crustacea: Peracarida) in the Gulf of California

Hydrobiologia - Hyperiid amphipods are pelagic crustaceans that live associated with gelatinous zooplankton including medusae, ctenophores, siphonophores, and salps. Standard plankton sampling...     

Associations between gelatinous zooplankton and hyperiid amphipods (Crustacea: Peracarida) in the Gulf of California

Hyperiid amphipods are pelagic crustaceans that live associated with gelatinous zooplankton including medusae, ctenophores, siphonophores, and salps. Standard plankton sampling disrupts natural associations, so the most reliable way to determine an association is through direct observation of the organisms in their environment. The planktonic fauna of the Gulf of California dwelling between 10 and 3000 m was surveyed using SCUBA diving and a remotely operated submersible (ROV) during March 2003. Here we report our observations on a total of 14 symbiotic associations found between the hyperiid amphipods and various taxa of gelatinous zooplankton. We found parental care behavior in a group of amphipods (Oxycephalidae) in which this phenomenon has not been previously reported. For two hyperiid species, Euthamneus rostratus and Vibilia australis, we present the first information on their symbiotic relations. Additional hosts were discovered for other well-known and widely distributed hyperiid species (i.e. Brachyscelus crusculum, Hyperoche medusarum). Photographic evidence of some of these interactions is included in this contribution. This is the first survey of these relationships in the Gulf of California, and many aspects of the ecology and biology of these symbioses remain to be studied.     

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.     

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.     

Extraordinary abundance of hydrocorals (Cnidaria,Hydrozoa, Stylasteridae) in shallow water of the Patagonian fjord region

During two scuba-diving expeditions in 2005 and 2006, stylasterids were documented and sampled from fjords and channels in the Central Patagonian Zone, Chile. At 15 of a total of 33 sampling sites we found colonies of Errina antarctica. We discuss the observed distribution patterns and the variability of colony shapes. In some regions we found E. antarctica to occur in extraordinary high densities on primary and secondary hard substratum below 10 m. In the archipelago Madre de Dios we discovered large colonies of E. antarctica covering areas of more than 10,000 m² with coverage exceeding 80%. The dense accumulations of E. antarctica have reef-like structure and form complex habitats. At one site we observed extensive mechanical damage to the corals that may result from coral extraction by divers and/or from boat anchors. Slow growth, fragility, scarceness and the lack of knowledge on their ecology make these spectacular and unique biocenoses very susceptible for damages and require protection and further studies.