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Global Diversity of the Stylasteridae (Cnidaria: Hydrozoa: Athecatae)  [PDF]
Stephen D. Cairns
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0021670
Abstract: The history and rate of discovery of the 247 valid Recent stylasterid species are discussed and graphed, with emphasis on five historical pulses of species descriptions. A table listing all genera, their species numbers, and their bathymetric ranges are presented. The number of species in 19 oceanographic regions is mapped, the southwestern temperate Pacific (region including New Zealand) having the most species; species are cosmopolitan from the Arctic Circle to the Antarctic at depths from 0 to 2789 m. The current phylogenetic classification of the genera is briefly discussed. An illustrated glossary of 53 morphological characters is presented. Biological and ecological information pertaining to reproduction, development, commensals, and distribution is discussed. Aspects of stylasterid mineralogy and taxa of commercial value are discussed, concluding with suggestions for future work.
The Global Diversity of Sea Pens (Cnidaria: Octocorallia: Pennatulacea)  [PDF]
Gary C. Williams
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0022747
Abstract: Recent advances in deep-sea exploration technology coupled with an increase in worldwide biotic surveys, biological research, and underwater photography in shallow water marine regions such as coral reefs, has allowed for a relatively rapid expansion of our knowledge in the global diversity of many groups of marine organisms. This paper is part of the PLoS ONE review collection of WoRMS (the Worldwide Register of Marine Species), on the global diversity of marine species, and treats the pennatulacean octocorals, a group of cnidarians commonly referred to as sea pens or sea feathers. This also includes sea pansies, some sea whips, and various vermiform taxa. Pennatulaceans are a morphologically diverse group with an estimated 200 or more valid species, displaying worldwide geographic and bathymetric distributions from polar seas to the equatorial tropics and from intertidal flats to over 6100 m in depth. The paper treats new discoveries and taxa new to science, and provides greater resolution in geographic and bathymetric distributions data than was previously known, as well as descriptions of life appearances in life and in situ observations at diverse depth.
Taxonomic redescription of the Portuguese man-of-war, Physalia physalis (Cnidaria, Hydrozoa, Siphonophorae, Cystonectae) from Brazil
Bardi, Juliana;Marques, Antonio C.;
Iheringia. Série Zoologia , 2007, DOI: 10.1590/S0073-47212007000400011
Abstract: although physalia physalis (linnaeus, 1758) is widely known from the brazilian waters, specimens from this coast were never properly described. we describe brazilian specimens of p. physalis including information on morphology, cnidome, sem, and histological studies. taxonomical issues concerning the development of the colonies and eventual synonymy with physalia utriculus (la martinière, 1787) are also added.
DYNAMICS OF SOMATIC CELLLINEAGE COMPETITION IN CHIMERAS OF Hydractinia symbiolongicarpus (CNIDARIA: HYDROZOA)
SCHWARZ,RYAN S; CADAVID,LUIS F;
Acta Biológica Colombiana , 2007,
Abstract: sessile colonial invertebrates often fuse with conspecifics to form chimeras. chimerism represents an unequivocal instance of withinindividual selection where genetically different celllineages compete for representation in the somatic and gametic pools. we analyzed temporal and spatial variations in somatic celllineage composition of laboratoryestablished chimeras of the hydroid hydractinia symbiolongicarpus (cnidaria: hydrozoa). using three clones with different allotypic specificities (i.e., two rejecting one another but fusing with a third one), we established two classes of twoway chimeras, a single threeway chimera class, and an incompatible interaction as control. chimeras were sampled at five time intervals for a year. celllineages in samples were identified by polyp fusibility assays against tester colonies of known fusibility. the cell lineages composing the chimeras showed a differential competitive ability, with one of them representing close to 80% by the end of the study. rare celllineages stabilized at low frequencies but preserved their ability to gain somatic representation and to colonize distant parts of the chimera. this behavior characterizes cell parasites. as a consequence of the reproductive plasticity of most colonial invertebrates, celllineage variability may be transmitted to the offspring both sexually and asexually. successful somatic competitors are expected to be preferentially transmitted asexually, whereas cell parasites would be preferentially transmitted sexually
Karyotyping and single-gene detection using fluorescence in situ hybridization on chromosomes of Hydra magnipapillata (Cnidaria: Hydrozoa)  [cached]
B Anokhin,G Hemmrich-Stanisak,T Bosch
Comparative Cytogenetics , 2010, DOI: 10.3897/compcytogen.v4i2.41
Abstract: The fresh water polyp Hydra L., 1758 (Cnidaria, Hydrozoa) plays a key role as a model organism in modern evolutionary and developmental biology. A complete genome sequence has been published recently for Hydra magnipapillata Ito, 1947 and molecular data are rapidly accumulating in the literature, but little information is available on its chromosomes. In this study, an efficient fluorescence in situ hybridization (FISH) method is described for H. magnipapillata which not only allows identification of the chromosomes but also visualization of the location of individual genetic loci. Together with cDNA and genomic sequencing this may provide the foundation for increasingly precise genetic and physical mapping in this basal metazoan model organism.
Dynamics of Somatic Cell-Lineage Competition in Chimeras of Hydractinia symbiolongicarpus (Cnidaria: Hydrozoa) Dinámica de competencia entre líneas celulares somáticas en quimeras de Hydractinia symbiolongicarpus (Cnidaria: Hydrozoa)
Schwarz Ryan S.,Cadavid Luis F.
Acta Biológica Colombiana , 2007,
Abstract: Sessile colonial invertebrates often fuse with conspecifics to form chimeras. Chimerism represents an unequivocal instance of withinindividual selection where genetically different celllineages compete for representation in the somatic and gametic pools. We analyzed temporal and spatial variations in somatic celllineage composition of laboratoryestablished chimeras of the hydroid Hydractinia symbiolongicarpus (Cnidaria: Hydrozoa). Using three clones with different allotypic specificities (i.e., two rejecting one another but fusing with a third one), we established two classes of twoway chimeras, a single threeway chimera class, and an incompatible interaction as control. Chimeras were sampled at five time intervals for a year. Celllineages in samples were identified by polyp fusibility assays against tester colonies of known fusibility. The cell lineages composing the chimeras showed a differential competitive ability, with one of them representing close to 80% by the end of the study. Rare celllineages stabilized at low frequencies but preserved their ability to gain somatic representation and to colonize distant parts of the chimera. This behavior characterizes cell parasites. As a consequence of the reproductive plasticity of most colonial invertebrates, celllineage variability may be transmitted to the offspring both sexually and asexually. Successful somatic competitors are expected to be preferentially transmitted asexually, whereas cell parasites would be preferentially transmitted sexually. Los invertebrados coloniales y sésiles con frecuencia se fusionan con conespecíficos para formar quimeras. Estas quimeras son un ejemplo de selección natural actuando al interior del individuo en donde células genéticamente distintas compiten por acceso tanto a la línea somática como a la germinal. En este estudio se analizaron las variaciones temporal y espacial de linajes celulares somáticos en quimeras establecidas en el laboratorio del hidroide colonial Hydractinia symbiolongicarpus (Cnidaria: Hydrozoa). Usando tres clones con distintas especificidades alotípicas (dos de ellas se rechazaban pero ambas se fusionaban a una tercera), se establecieron dos clases de biquimeras, una triquimera y una interacción incompatible como control. Muestras de tejido de quimeras se obtuvieron en cinco intervalos de tiempo durante 50 semanas. La identidad celular de cada muestra se determinó por ensayos de fusibilidad de pólipos con colonias estándar de fusibilidad conocida. Los distintos linajes celulares de cada quimera mostraron una habilidad competitiva diferencial, co
Development and population growth of Hydra viridissima Pallas, 1766 (Cnidaria, Hydrozoa) in the laboratory
Massaro, FC.;Rocha, O.;
Brazilian Journal of Biology , 2008, DOI: 10.1590/S1519-69842008000200020
Abstract: hydras, the most representative freshwater cnidaria, are of common occurrence in bodies of water in every continent except antarctica. this study was planned with the aim of maintaining a population of hydra viridissima in laboratory culture to enable the determination of the individual and population growth-rates of this species, as well as its population doubling time and generation time, with a view to employing these common animals as test-organisms in ecotoxicological assays. the organisms were maintained in reconstituted water at 20 ± 2 °c, illuminated at 800 lux with a photoperiod of 12 hours light: 12 hours dark, and were fed on neonates of the cladoceran ceriodaphnia silvestrii (3 or 4 neonates per hydra, 3 times a week). the individual growth-rate (k) of the species was 0.43, the maximum length of the column 2.53 mm and the generation time 6.6 ± 1.5 days on average. the hydra population showed an intrinsic growth-rate (r) of 0.0468, according to the fitted curve, and a doubling time of 14.8 ± 2.63 days. hydra viridissima is easy to grow in the laboratory and performs well in the conditions used in this study. it is thus a promising candidate test-organism for ecotoxicological studies.
Biodiversity of Prokaryotic Communities Associated with the Ectoderm of Ectopleura crocea (Cnidaria, Hydrozoa)  [PDF]
Cristina Gioia Di Camillo, Gian Marco Luna, Marzia Bo, Giuseppe Giordano, Cinzia Corinaldesi, Giorgio Bavestrello
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0039926
Abstract: 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.
Hydroids (Cnidaria, Hydrozoa) of Coral Reefs: Preliminary Results on Community Structure, Species Distribution and Reproductive Biology in Juan de Nova Island (Southwest Indian Ocean)
N Gravier-Bonnet, C A-F Bourmaud
Western Indian Ocean Journal of Marine Science , 2006,
Abstract: The first field investigation of the marine life at Juan de Nova gave an opportunity to study hydroid diversity in April-May 2004. Species richness was high, with 95 species belonging to 26 families and 44 genera. Thecates dominated (72%), with three families particularly diverse: Haleciidae, Sertulariidae and Aglaopheniidae. There were four different sub-communities with a few species in common: two intertidal and two subtidal. One was located on reef flats subject to strong hydrodynamic conditions, and included rheophilic and photophilic species such as Millepora exaesa, Nemalecium sp., Dynamena crisoides, Thyroscyphus fruticosus, Thyroscyphus sp. and Aglaophenia cupressina. The second was found where the reef flat experienced calmer conditions, and comprised mainly Plumularioidea and Haleciidae species with small sized colonies (1-3cm) and large populations, densely covering the hard substrata of coral patches. The third sub-community colonized the reef platform (5-20m), with hydroids widespread and diverse. The fourth was on the outer slope, deeper (30m), and was characterized by the presence of four Solanderia species, several Aglaophenids and Thyroscyphus aequalis. Most of the species were brooders (84%). Present data are discussed regarding environmental parameters, and compared with data from the les Glorieuses, other islands of the Mozambique Channel.
Species Diversity of Shallow Water Zoanthids (Cnidaria: Anthozoa: Hexacorallia) in Florida  [PDF]
James Davis Reimer,Colin Foord,Yuka Irei
Journal of Marine Biology , 2012, DOI: 10.1155/2012/856079
Abstract: Shallow water zooxanthellate zoanthids are a common component of the coral reef ecosystems of the Caribbean. Despite this, their species diversity remains poorly understood. In this study, collected Palythoa, Zoanthus, Isaurus, and Terrazoanthus specimens from the waters of Florida were phylogenetically examined to obtain a better understanding of zoanthid species diversity in the Caribbean. Surprisingly, the results from analyses utilizing three DNA markers (mitochondrial 16S ribosomal DNA, cytochrome oxidase subunit I, and the internal transcribed spacer of ribosomal DNA) showed the presence of at least eleven species, of which up to four appear undescribed. Additionally, the presence of the genus Terrazoanthus in the Caribbean was confirmed for the first time. Attempts to match phylogenetic species or clades with original literature were hampered by vague and short original descriptions, and it is clear that for Atlantic Palythoa and Zoanthus species an in-depth and multidisciplinary investigation is needed to reconcile recent phylogenetic results such as in this study with traditional taxonomy. Furthermore, most shallow water zoanthid species from Florida were observed to have close, sister-species relationships with previously investigated species in the Pacific Ocean. These results indicate that many brachycnemic zoanthid species likely had a Caribbean-Pacific distribution until the formation of the Isthmus of Panama. However, due to inadvertent redescriptions, overall species diversity in these two common genera is likely much lower than literature indicates. 1. Introduction The coral reef ecosystems of Florida are the only large area of shallow water coral reefs in the continental United States, and as such have been the subject of studies investigating their ecology [1], biodiversity, and recent history [2]. Despite this, the region has undergone rapid degradation in terms of live coral coverage due to coral bleaching [3] and disease [4], among other stressors, with corresponding large losses of live coral cover [5, 6]. One of the most common groups of organisms on the reefs of Florida and the Greater Caribbean is the zoanthids. In fact, some zoanthids (Anthozoa: Hexacorallia) are so common that a portion of the shallow intertidal zone has been called the “Zoanthus zone” [7]. Like many reef-building hard corals, most shallow tropical and subtropical zoanthids are in symbiosis with Symbiodinium (=zooxanthellae) species, endosymbiotic, photosynthetic dinoflagellates. Despite being an obvious and ubiquitous part of the Caribbean coral reef
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