Academic literature on the topic 'Hydrozoans'

Medusozoan jellyfish (Classes Scyphozoa and Hydrozoa) have gained a degree of worldwide notoriety in the last fifteen years, particularly as anthropogenic influences such as climate change and overfishing push some ecosystems toward their advantage (Lynam et al. 2005, Purcell and Arai 2001, Purcell et al. 2007, Purcell 2012, Flynn et al. 2012, Dawson et al. 2014). Accordingly, both the lay and scientific media have paid a good deal of attention to jellyfish bloom phenomena and their impacts on human activities, but the bulk of this attention has been devoted to larger, visually obvious species of Class Scyphozoa. Only recently have their smaller cousins, the hydrozoans, come to be recognized as potentially problematic. This thesis examines population ecology of hydrozoan medusae (hydromedusae) and their implications for salmon aquaculture in Scotland. My review of available literature has found hydrozoans to be a recognized - though under- studied - problem for Scottish salmon (Chapter 1, Prospective monitoring of hydromedusa populations at salmon aquaculture facilities). Typically, hydrozoan populations at salmon farms have been discussed in the scientific literature only in the context of extremely dense visible blooms or in the wake of major mortality incidents. This retrospective, rather than prospective, approach has left a dearth of knowledge pertaining to hydromedusan interactions with farmed fish, with both fish welfare and industry economics vulnerable to future blooms. This thesis sought to build a basis for the goals of prediction, avoidance, and mitigation of harmful hydrozoan jellyfish blooms. First and foremost, this required the development of a prospective time-series dataset of hydromedusan occurrences at salmon farms (Chapter 2, Bacterial genera biodiversity in three medusozoan species in Shetland). To this end, four farms were recruited as participants across a three-year survey. Weekly plankton tow-based sampling at these sites identified which hydrozoan species could be expected to produce blooms, the seasonality of such blooms, and the pathological sequelae that could be expected in salmon after exposure to such blooms. Following one particularly dramatic bloom, a spike in gill pathologies in salmon was observed, followed by a spike in overall mortality and the eventual loss of up to £2.5 million value as the fish were humanely culled. This survey also demonstrated that hydromedusan blooms are usually spatially and temporally patchy, limiting the opportunities for geographically-encompassing predictive power. Instead, individual aquaculture facilities may require site-specific risk assessment and planning frameworks to monitor and cope with blooms. Potential methods for continued basic monitoring and a mitigation strategy based on minimizing contact between fish and high-density blooms are suggested. A second mitigation goal examined the theory that medusae may act as vectors for microbial pathogens, particularly Tenacibaculum maritimum (Ferguson et al. 2010, Delannoy et al. 2011; Chapter 3). Sampling methods designed to target T. maritimum were employed with the aim of determining its distribution and role as a symbiont in various life stages of medusozoan species. While T. maritimum itself was not observed, a number of other fish pathogens were found in close association with several species. This included Aeromonas salmonicida, known to cause furunculosis in aquaculture of both salmon and trout (Nomura et al. 1992). Further work is required to piece together the nature of these associations. Finally, Chapter 2 identified a particular hydrozoan genus, Obelia, as a likely significant contributor to blooms at salmon aquaculture sites. One of its species, O. geniculata, has a widely distributed and well-recognized benthic colonial life stage (called the hydroid stage) in Scottish nearshore sublittoral environments. In attempting to sample these hydroids from previously well-colonized sites in Shetland in late 2012, it became apparent that a severe local reduction in the benthic population was taking place. This allowed for the opportunity to study phylogeographic population structure - i.e. the boundaries of its gene pool(s) in Scottish waters and its potential for dispersal during one seasonal reproductive period - using a molecular study of the mitochondrial cytochrome oxidase subunit I (mtCOI) gene (Chapter 4, Phylogeographic analysis of Obelia geniculata populations in the north of Scotland). In sampling immediately after the observed dieback, O. geniculata was found to follow a south-to-north pattern of genetic grouping, as well as a confirmed dieback. However, this pattern disappeared in samples collected after the population had recovered, probably due to the immigration of genetically novel individuals. This finding, in conjunction with the spatial-temporal patchiness found in the medusa bloom stage, suggests the importance of the larval stage as the primary stage for dispersal in the plankton. This study was also able to compare present population genetic data with a set of O. geniculata mtCOI data collected between 1998 and 2002. The combined data potentially show a high degree of mixing across a number of North Atlantic regions, including Icelandic and North American sites. Further investigation will be required to discern whether this pattern is temporally based (i.e. artefact of 15 years' elapsed time in opportunities for population mixing), or whether ecological, anthropogenic, or combined mechanisms are facilitating rapid transport of propagules to yield a well-mixed population. Further work in refining prediction and mitigation is still needed, as are effective veterinary interventions in the event of blooms. Continued study into the ecological patterns of colonization and dispersal may help to minimize exposure to blooms, by helping to assess site-based risks. This research forms the basis for such studies into hydrozoan interactions with salmon farms in Scotland, and how the industry might seek to minimize their impacts.

Un contrôle précis de la maturation ovocytaire et de la ponte sont essentiels au succès de la reproduction sexuée au sein le règne animal. Ces processus sont coordonnés précisément par des signaux endocriniens et/ou environnementaux, selon les espèces, mais beaucoup reste à apprendre sur leurs régulations. Chez les cnidaires, de nombreuses méduses du groupe des hydrozoaires sont connues pour produire des gamètes en réponse à la transition nuit/jour. Pour caractériser les machineries cellulaires et moléculaires liant la réception de la lumière à l'initiation de la maturation ovocytaire, j'ai étudié la méduse hydrozoaire Clytia hemisphaerica. Mon travail de thèse s’est découpé en trois parties, chacune impliquant l'identification d'un composant moléculaire clé de ce processus.Mon étude initiale faisait partie d'une collaboration avec N. Takeda (Asamushi) et R. Deguchi (Sendai), chercheurs qui avaient, avant le début de ma thèse, identifié chez Clytia les Hormones d'Incitation de Maturation ovocytaire endogènes (MIH) comme étant des tétrapeptides de type WPRPamide, produit par clivage de deux précurseurs à neuropeptides. J'ai montré par hybridation in situ et immunofluorescence que les deux gènes précurseurs du MIH sont exprimés par un type de cellules neurosécrétrices localisées au niveau de l’ectoderme de la gonade, et que les peptides MIH sont sécrétés par ces mêmes cellules suite à une stimulation lumineuse. Cette étude a posé les bases permettant l'identification des régulateurs agissant en amont et en aval du MIH, et plus spécifiquement ceux impliqués dans la photoréception de l’ectoderme de la gonade et la réception du MIH par les ovocytes.Pour identifier le récepteur du MIH de Clytia (CheMIHR) dans les ovocytes, j'ai compilé à partir de données transcriptomiques issues de tissus de gonades, une liste de 16 protéines candidates de la famille des Récepteurs Couplés aux Protéines G (GPCR). J'ai cloné les 16 cDNAs et, utilisant une méthode de « deorphelinisation » de GPCR basée sur de la culture cellulaire (collaboration avec P. Bauknecht et G. Jékély; MPI, Tübingen), j’ai pu identifier un GPCR activée par des peptides MIH synthétiques. Sa fonction in vivo comme récepteur essentiel du MIH a été confirmée par la méthode d'édition génétique CRISPR/CAS9. La délétion ainsi produite, entraînant un déplacement du cadre de lecture au sein du gène CheMIHR, a détérioré la croissance des colonies de polypes et le comportement de ponte des méduses matures. Confirmant la fonction de CheMIHR, la maturation ovocytaire chez des mutants CheMIHR ne pouvait pas être déclenchée par la lumière ou par addition de MIH synthétiques, mais pouvait être rétablie en utilisant des analogues au cAMP, molécule connue pour agir en aval de la réception du MIH dans les ovocytes d’hydrozoaires. Des analyses phylogénétiques ont montré que Clytia MIHR est affilié à un sous-ensemble de familles de neuropeptides de bilaterians impliqués dans divers processus physiologiques, notamment la régulation de la reproduction. Des hybridations in situ sur les méduses Clytia, ont en outre montré l'expression des précurseurs de CheMIH et de CheMIHR dans des cellules neurales hors de la gonade, suggérant un rôle plus large du couple CheMIH-MIHR que la seule initiation de la maturation ovocytaire.Pour mieux comprendre la photoréception des gonades chez Clyita, j'ai montré que la ponte est sélectivement incitée par la lumière bleu-cyan, et mis en évidence, grâce à l’analyse de données de transcriptome de gonade, qu’un photopigment de la famille des Opsin (Opsin9) est hautement exprimé dans l'ectoderme. De façon saisissante, les hybridations in situ ont montré que le gène Opsin9 est exprimé dans les mêmes cellules sécrétant le MIH. L'introduction d'une mutation de changement de cadre de lecture dans le gène Opsin9 via la technologie CRISPR/Cas9 a empêché la maturation ovocytaire et la ponte des méduses mutantes en réponse à la lumière<br>Tight control of oocyte maturation and of gamete release is essential for successful sexual reproduction in the animal kingdom. These processes are precisely coordinated by endocrine and/or environmental cues, depending on the species, but much remains to be learned about their regulation. Within the Cnidaria, many hydrozoan jellyfish are known to spawn mature gametes following dark/light transitions. To characterise the cellular and molecular machinery linking light reception and oocyte maturation initiation, I have studied the hydrozoan jellyfish Clytia hemisphaerica. My thesis work had three parts, each involving the identification of a key molecular component of this process.My initial study was part of a collaboration with N. Takeda (Asamushi) and R. Deguchi (Sendai), who identified the endogenous oocyte Maturation-Inducing Hormones (MIH) in Clytia as WPRPamide-related tetrapeptides, generated by cleavage of two neuropeptide precursors. I showed by in situ hybridization and immunofluorescence that Clytia MIH is produced by neurosecretory cells of the gonad ectoderm that co-express the two precursor genes, and that it is secreted upon light stimulation. This study paved the way for identification of regulators acting upstream and downstream of MIH release in the gonads, specifically the ones involved in photoreception in the gonad ectoderm, and in MIH reception by the oocytes. To identify the Clytia MIH receptor (CheMIHR) in the oocytes, I compiled a shortlist of 16 candidate G protein-coupled receptors (GPCRs) from gonad transcriptome data. I cloned all 16 cDNAs and, using a cell culture-based "GPCR deorphanization" assay (collaboration with P. Bauknecht and G. Jékély; MPI, Tübingen), identified one GPCR that was activated by synthetic MIH peptides. Its in vivo function as the essential MIH receptor was confirmed by CRISPR/Cas9 gene editing. Introduction of a frame-shift mutation in the CheMIHR gene impaired growth of Clytia polyp colonies and also the spawning behaviour of mature medusae. Confirming the function of CheMIHR, oocyte maturation in CheMIHR mutants could not be triggered by light or by synthetic MIH, but could be restored using cell-permeable analogues of cAMP, known to act downstream of MIH reception in hydrozoan oocytes. Phylogenetic analyses showed that Clytia MIHR is related to a subset of bilaterian neuropeptide hormone receptor families involved in diverse physiological processes, including regulation of reproduction. Accordingly, in situ hybridization showed the expression of Clytia MIH precursors and MIHR in non-gonadal neural cells, suggesting a wider role of Clytia MIH-MIHR besides oocyte maturation initiation.To address gonad photoreception, I showed that Clytia spawning is selectively induced by blue-cyan light, and then identified using gonad transcriptome data an opsin photopigment (Opsin9) highly expressed in the ectoderm. Strikingly, in situ hybridization showed that Opsin9 is expressed in the MIH-secreting cells. Introduction of a frame-shift mutation into the Opsin9 gene via CRISPR/Cas9 prevented oocyte maturation and spawning of mutant jellyfish in response to light. Anti-MIH immunofluorescence and rescue experiments with synthetic MIH showed that the essential function of Opsin9 is upstream of MIH release. Spawning in Clytia thus appears to be regulated by a dual function photosensory-neurosecretory cell type, perhaps retained from a distant metazoan ancestor

Un contrôle précis de la maturation ovocytaire et de la ponte sont essentiels au succès de la reproduction sexuée au sein le règne animal. Ces processus sont coordonnés précisément par des signaux endocriniens et/ou environnementaux, selon les espèces, mais beaucoup reste à apprendre sur leurs régulations. Chez les cnidaires, de nombreuses méduses du groupe des hydrozoaires sont connues pour produire des gamètes en réponse à la transition nuit/jour. Pour caractériser les machineries cellulaires et moléculaires liant la réception de la lumière à l'initiation de la maturation ovocytaire, j'ai étudié la méduse hydrozoaire Clytia hemisphaerica. Mon travail de thèse s’est découpé en trois parties, chacune impliquant l'identification d'un composant moléculaire clé de ce processus.Mon étude initiale faisait partie d'une collaboration avec N. Takeda (Asamushi) et R. Deguchi (Sendai), chercheurs qui avaient, avant le début de ma thèse, identifié chez Clytia les Hormones d'Incitation de Maturation ovocytaire endogènes (MIH) comme étant des tétrapeptides de type WPRPamide, produit par clivage de deux précurseurs à neuropeptides. J'ai montré par hybridation in situ et immunofluorescence que les deux gènes précurseurs du MIH sont exprimés par un type de cellules neurosécrétrices localisées au niveau de l’ectoderme de la gonade, et que les peptides MIH sont sécrétés par ces mêmes cellules suite à une stimulation lumineuse. Cette étude a posé les bases permettant l'identification des régulateurs agissant en amont et en aval du MIH, et plus spécifiquement ceux impliqués dans la photoréception de l’ectoderme de la gonade et la réception du MIH par les ovocytes.Pour identifier le récepteur du MIH de Clytia (CheMIHR) dans les ovocytes, j'ai compilé à partir de données transcriptomiques issues de tissus de gonades, une liste de 16 protéines candidates de la famille des Récepteurs Couplés aux Protéines G (GPCR). J'ai cloné les 16 cDNAs et, utilisant une méthode de « deorphelinisation » de GPCR basée sur de la culture cellulaire (collaboration avec P. Bauknecht et G. Jékély; MPI, Tübingen), j’ai pu identifier un GPCR activée par des peptides MIH synthétiques. Sa fonction in vivo comme récepteur essentiel du MIH a été confirmée par la méthode d'édition génétique CRISPR/CAS9. La délétion ainsi produite, entraînant un déplacement du cadre de lecture au sein du gène CheMIHR, a détérioré la croissance des colonies de polypes et le comportement de ponte des méduses matures. Confirmant la fonction de CheMIHR, la maturation ovocytaire chez des mutants CheMIHR ne pouvait pas être déclenchée par la lumière ou par addition de MIH synthétiques, mais pouvait être rétablie en utilisant des analogues au cAMP, molécule connue pour agir en aval de la réception du MIH dans les ovocytes d’hydrozoaires. Des analyses phylogénétiques ont montré que Clytia MIHR est affilié à un sous-ensemble de familles de neuropeptides de bilaterians impliqués dans divers processus physiologiques, notamment la régulation de la reproduction. Des hybridations in situ sur les méduses Clytia, ont en outre montré l'expression des précurseurs de CheMIH et de CheMIHR dans des cellules neurales hors de la gonade, suggérant un rôle plus large du couple CheMIH-MIHR que la seule initiation de la maturation ovocytaire.Pour mieux comprendre la photoréception des gonades chez Clyita, j'ai montré que la ponte est sélectivement incitée par la lumière bleu-cyan, et mis en évidence, grâce à l’analyse de données de transcriptome de gonade, qu’un photopigment de la famille des Opsin (Opsin9) est hautement exprimé dans l'ectoderme. De façon saisissante, les hybridations in situ ont montré que le gène Opsin9 est exprimé dans les mêmes cellules sécrétant le MIH. L'introduction d'une mutation de changement de cadre de lecture dans le gène Opsin9 via la technologie CRISPR/Cas9 a empêché la maturation ovocytaire et la ponte des méduses mutantes en réponse à la lumière<br>Tight control of oocyte maturation and of gamete release is essential for successful sexual reproduction in the animal kingdom. These processes are precisely coordinated by endocrine and/or environmental cues, depending on the species, but much remains to be learned about their regulation. Within the Cnidaria, many hydrozoan jellyfish are known to spawn mature gametes following dark/light transitions. To characterise the cellular and molecular machinery linking light reception and oocyte maturation initiation, I have studied the hydrozoan jellyfish Clytia hemisphaerica. My thesis work had three parts, each involving the identification of a key molecular component of this process.My initial study was part of a collaboration with N. Takeda (Asamushi) and R. Deguchi (Sendai), who identified the endogenous oocyte Maturation-Inducing Hormones (MIH) in Clytia as WPRPamide-related tetrapeptides, generated by cleavage of two neuropeptide precursors. I showed by in situ hybridization and immunofluorescence that Clytia MIH is produced by neurosecretory cells of the gonad ectoderm that co-express the two precursor genes, and that it is secreted upon light stimulation. This study paved the way for identification of regulators acting upstream and downstream of MIH release in the gonads, specifically the ones involved in photoreception in the gonad ectoderm, and in MIH reception by the oocytes. To identify the Clytia MIH receptor (CheMIHR) in the oocytes, I compiled a shortlist of 16 candidate G protein-coupled receptors (GPCRs) from gonad transcriptome data. I cloned all 16 cDNAs and, using a cell culture-based "GPCR deorphanization" assay (collaboration with P. Bauknecht and G. Jékély; MPI, Tübingen), identified one GPCR that was activated by synthetic MIH peptides. Its in vivo function as the essential MIH receptor was confirmed by CRISPR/Cas9 gene editing. Introduction of a frame-shift mutation in the CheMIHR gene impaired growth of Clytia polyp colonies and also the spawning behaviour of mature medusae. Confirming the function of CheMIHR, oocyte maturation in CheMIHR mutants could not be triggered by light or by synthetic MIH, but could be restored using cell-permeable analogues of cAMP, known to act downstream of MIH reception in hydrozoan oocytes. Phylogenetic analyses showed that Clytia MIHR is related to a subset of bilaterian neuropeptide hormone receptor families involved in diverse physiological processes, including regulation of reproduction. Accordingly, in situ hybridization showed the expression of Clytia MIH precursors and MIHR in non-gonadal neural cells, suggesting a wider role of Clytia MIH-MIHR besides oocyte maturation initiation.To address gonad photoreception, I showed that Clytia spawning is selectively induced by blue-cyan light, and then identified using gonad transcriptome data an opsin photopigment (Opsin9) highly expressed in the ectoderm. Strikingly, in situ hybridization showed that Opsin9 is expressed in the MIH-secreting cells. Introduction of a frame-shift mutation into the Opsin9 gene via CRISPR/Cas9 prevented oocyte maturation and spawning of mutant jellyfish in response to light. Anti-MIH immunofluorescence and rescue experiments with synthetic MIH showed that the essential function of Opsin9 is upstream of MIH release. Spawning in Clytia thus appears to be regulated by a dual function photosensory-neurosecretory cell type, perhaps retained from a distant metazoan ancestor

O Brasil possui uma extensão de costa marítima de mais de 9.200 km. Contudo, os componentes vivos presentes em suas águas costeiras e neríticas são parcamente conhecidos em termos taxonômicos, biogeográficos e ecológicos. Embora constitua um dos principais grupos de predadores pelágicos, seja abundante e de dimensões relativamente grandes, o plâncton gelatinoso é normalmente subestimado nos estudos de plâncton. A classe Hydrozoa é um dos grupos de invertebrados gelatinosos mais bem representados e comuns no plâncton. Dentre os trabalhos sobre hidromedusas, somente alguns abrangeram áreas extensas da plataforma continental brasileira, embora coleções oriundas de campanhas oceanográficas, como as realizadas pelo Instituto Oceanográfico da Universidade de São Paulo (IO-USP), estejam disponíveis para estudo. O objetivo do presente é inventariar as espécies de hidromedusas oriundas de duas campanhas oceanográficas realizadas pelo IO-USP na plataforma continental entre Cabo de Santa Marta Grande (SC) e Cabo Frio (RJ) (Plataforma Continental Sudeste - PCSE), nos anos de 1991 e 2001: Sardinha 1 e PADCT 2. A composição da fauna foi analisada quanto à diversidade de espécies e distribuição geográfica. Os dados foram interpretados procurando-se inferir correlações na distribuição das espécies com as massas de água características da região (Água Costeira AC; :Água Tropical AT; Água Central do Atlântico Sul ACAS). Dados brutos de distribuição também foram utilizados em uma Análise de Parcimônia de Endemicidade (PAE), no intuito de averiguar possíveis áreas de endemismo das espécies. Nas 155 amostras analisadas foram encontradas 51.808 espécimes de hidromedusas, identificados em 20 morfotipos: 10 Anthoathecata, 5 Leptothecata, 3 Trachymedusae e 2 Narcomedusae. Tanto a diversidade quanto a abundância das espécies foram menores nas amostras referentes à campanha PADCT 2 (figuras 2.2 a 2.5) quando comparadas com as da campanha Sardinha 1. Todas as espécies já haviam sido registradas para a costa brasileira, no entanto, algumas tiveram suas distribuições geográficas ampliadas. Liriope tetraphylla e Aglaura hemistoma foram as espécies mais freqüentes e abundantes nas amostras das campanhas Sardinha 1 e PADCT 2, respectivamente. As distribuições geográficas de algumas espécies mostram-se associadas, como Aglaura hemistoma e Corymorpha gracilis; Solmundella bitentaculata e a co-ocorrência do par Aglaura hemistoma-Liriope tetraphylla; e Turritopsis nutricula e Proboscidactyla ornata, estas últimas co-ocorrem sobretudo quando abundantes. O relativo baixo número de espécies de hidromedusas encontrado no presente trabalho pode ser conseqüência do método de amostragem utilizado, o qual não visava o plâncton gelatinoso. No entanto, entre os 20 táxons identificados encontram-se as espécies mais freqüentes registradas para a PCSE, como Aglaura hemistoma, Liriope tetraphylla, Rhopalonema velatum, Solmundella bitentaculata e Turritopsis nutricula. Algumas espécies apresentam relação com a presença predominante de ACAS seguida por AC: Turritopsis nutricula, Niobia dendrotentaculata, Proboscidactyla ornata, Solmundella bitentaculata e Corymorpha gracilis. Enquanto que a maioria dos exemplares de Liriope tetraphylla e Eucheilota duodecimalis,esteve associada à presença de AC. Aglaura hemistoma e Rhopalonema velatum estiveram relacionadas à ACAS ou AT+ACAS, respectivamente. A Análise de Parcimônia de Endemismo (PAE) destaca duas áreas, a primeira majoritariamente compreendida entre as isóbatas de 50 e 200 m, apresenta predomínio de ACAS em suas estações de coleta, com a presença Bougainvillia carolinensis e Dipurena sp. e o predomínio de abundância de Corymorpha gracilis, Ectopleura dumortieri, Niobia dendrotentaculata, Proboscidactyla ornata. A segunda apresenta grande abundância de Rhopalonema velatum e localiza-se principalmente a leste da isóbata de 200 m, praticamente acompanhando a distribuição das estações com AT como massa de água principal e ACAS como secundária.<br>Brazil has an extensive marine coast of over 9.200 km. However, the taxonomical, biogeographical and ecological knowledge of the organisms present in coastal and neritic waters is scanty. Although the gelatinous plankton constitutes one of the main groups of pelagic predators, is abundant and relatively large, in size, it is usually underestimated in number and importance by the traditional sampling methods. Hydrozoa are one of the most numerous and common groups in this planktonic community. Among the works on hydromedusae, only some included extensive areas of the Brazilian continental shelf, although sampling of oceanographic expeditions, as the ones accomplished by the Instituto Oceanográfico of the Universidade de São Paulo (IO-USP), are available for study. The goal of this study is to survey the hydromedusae species collected by two oceanographic expeditions by the Brazilian vessel carried out by IO-USP along the continental shelf between Cabo Frio (RJ) and Cabo de Santa Marta Grande (SC) (South Brazil Bight - SBB), in 1991 and 2001: Sardinha 1 and PADCT 2. The diversity and geographic distribution of the hydromedusae fauna were analyzed. Data were interpreted trying to infer correlations in the distribution of the species with the characteristic water masses present in the area (Coastal Water - CW; Tropical Water - TW; South Atlantic Central Water - SACW). The distribution data were also used in a Parsimony Analysis of Endemicity (PAE), to verify possible endemic areas of the species. From the 155 samples a total of 51,808 hydromedusae specimens were found, belonging to 20 species/morphotypes: 10 Anthoathecata; 5 Leptothecata; 3 Trachymedusae; 2 Narcomedusae. The diversity and abundance of the species were lower in the samples of PADCT 2 when compared to Sardinha 1. All of the species had already been recorded for the Brazilian coast; however, some had their geographical distributions enlarged. Liriope tetraphylla and Aglaura hemistoma were the most frequent and abundant species in the samples of the Sardinha 1 and PADCT 2, respectively. There are indications that the geographical distributions of some species are associated, as Aglaura hemistoma and Corymorpha gracilis; Solmundella bitentaculata and the pair Aglaura hemistoma-Liriope tetraphylla; Turritopsis nutricula and Proboscidactyla ornata, the last association usually occurring when both species are abundant. The relative low number of hydromedusae species found in SBB can be consequence of the sampling method, which did not aim at the gelatinous plankton. However, among the 20 identified species/morphotypes are the most frequent species already recorded for SBB, as Aglaura hemistoma, Liriope tetraphylla, Rhopalonema velatum, Solmundella bitentaculata and Turritopsis nutricula.. Some species distributions are associated to specific water masses like Turritopsis nutricula, Niobia dendrotentaculata, Proboscidactyla ornata, Solmundella bitentaculata and Corymorpha gracilis in a mixture of SACW and CW. Most individuals of Liriope tetraphylla and Eucheilota duodecimalis were related to the exclusive presence of CW, while the majority of Aglaura hemistoma and Rhopalonema velatum individuals were associated with SACW or TW+SACW, respectively. Two areas were identified in a Parsimony Analysis of Endemicity (PAE), the first located between 50 and 200 m deep and predominance of SACW, with the presence of Bougainvillia carolinensis, Dipurena sp. and the predominance in abundance of Corymorpha gracilis, Ectopleura dumortieri, Niobia dendrotentaculata, and Proboscidactyla ornata. The second area was characterized by high abundance of Rhopalonema velatum, being located east of the 200 m bathymetric line, along the occurrence of TW (main water mass) and SACW (secondary water mass).

As hidras são os principais representantes de água doce do filo Cnidaria, e quando são expostas a substâncias tóxicas podem manifestar mudanças graduais na estrutura corporal, cuja expressão permite determinar as doses de efeitos letais e sub-letais de uma substância tóxica. No presente estudo, a espécie nativa Hydra viridissima foi cultivada em condições laboratoriais, determinando-se o crescimento populacional e individual da espécie, o tempo de duplicação da população e o tempo de geração da mesma. Além disso, esta espécie foi submetida a testes de toxicidade aguda com as substâncias dicromato de potássio e sulfeto de sódio. Testes de toxicidade também foram realizados com amostras ambientais de água e/ou sedimento de reservatórios do estado de São Paulo, visando a utilização desta espécie como organismo-teste para estudos ecotoxicológicos. A taxa de crescimento individual (k) foi de 0,43; o comprimento máximo da coluna das hidras foi de 2,53 mm e o tempo de geração foi, em média, de 6,6 '+ OU -' 1,5 dias. Para as condições de cultivo a taxa intrínseca de crescimento populacional de H. viridissima foi de 0,0468 (r) e o tempo de duplicação da população de 14,8 '+ OU -' 2,63 dias. A faixa de sensibilidade de H. viridissima ao dicromato de potássio situa-se entre 2,8 mg/L e 4,3 mg/L, com valor médio de 3,55 mg/L, sendo que esta espécie é mais sensível a esta substância do que algumas espécies que já são amplamente utilizadas em testes de toxicidade, incluindo a espécie Hydra attenuata. Nos testes de toxicidade realizados com o sulfeto de sódio estabeleceu-se que a faixa de sensibilidade para esta espécie situa-se entre 17,76 mg/L e 26,08 mg/L, com uma 'CL IND.50'-96h de 21,92 mg/L, e observou-se uma diminuição ou perda de toxicidade desta substância durante o período de realização dos testes. As amostras de água e de sedimento dos reservatórios do Lobo (Broa), de Barra Bonita e de Promissão não causaram toxicidade às hidras, enquanto que o sedimento do reservatório de Rasgão foi tóxico. Concluiu-se que a espécie H. viridissima é de fácil cultivo em laboratório, tem bom desempenho em cultivo nas condições testadas e sofre progressivas modificações morfológicas sob condições de toxicidade, sendo, portanto, um potencial organismo-teste para estudos ecotoxicológicos<br>Hydras are the main freshwater representatives of phylum Cnidaria, and when exposed to toxic substances they can display gradual changes in the body structure, whose expression allows determining the lethal and sub-lethal doses of a toxic substance. In the present study, the native species Hydra viridissima was cultured in the laboratory in order to determine its population and individual growth, the time of duplication of the population and its generation time. This species was also submitted to acute toxicity tests with the reference substances potassium dichromate and sodium sulfide, and also to toxicity tests with samples of water and/or sediment of reservoirs of the state of São Paulo, aiming to use this species as organism-test for ecotoxicological studies. The main results were an individual growth rate (k) of 0.43; the maximum length of the hydra column was 2.53 mm and the generation time averaged 6.6 '+ OU -' 1.5 days. This species presented an intrinsic rate of population growth (r) of 0.0468 for the adjusted curve and a time of duplication of the population of 14.8 '+ OU -' 2.63 days. H. viridissima has a sensitivity range for potassium dichromate varying between 2.8 mg/L and 4.3 mg/L, with a mean value of 3.55 mg/L. This species is more sensible to this substance than other species widely used in toxicity tests, including Hydra attenuata. The sensitivity range of H. viridissima to sodium sulfide varies between 17.76 mg/L and 26.08 mg/L, with a 'LC IND.50'-96h of 21.92 mg/L. A reduction or loss of toxicity to this substance was observed during the test accomplishment. The water and sediment samples of Lobo, Barra Bonita and Promissão reservoirs were not toxic, nevertheless the sediment of Rasgão reservoir was toxic to the hydras. It was concluded that H. viridissima is easy to culture in the laboratory, has a good performance in the culture conditions tested and suffers gradual morphological changes under toxic conditions, being, therefore, a potential test-organism for ecotoxicological studies

La famiglia Stylasteridae è una della due famiglie di idroidi a presentare uno scheletro calcareo chiamato coenosteum. Gli Stylasteridae sono idroidi polimorfici e presentano due tipi di polipi che escono lungo il coenosteum attraverso dei pori. La distribuzione dai pori lungo la colonia e la loro forma sono caratteristiche strettamente legate al genere. I polipi di una colonia sono connessi attraverso una fitta rete di canali cenosarcali che permea l’intero scheletro. Durante il dottorato, la morfologia dello scheletro degli Stylasteridae è stata studiata per la prima volta attraverso l’utilizzo della microtomografia computerizzata a raggi X (Xray μCT). E’ stato dimostrato come questa tecnica non distruttiva risulti molto utile nello studio della morfologia scheletrica ed inoltre è stato osservato come l’approccio integrato tra questa tecnica e il tradizionale tecnica SEM permetta uno studio più approfondito e dettagliato della tassonomia di questa famiglia. Infatti, i risultati ottenuti attraverso la combinazione di queste due tecniche permettono l’identificazione di caratteri morfologici che altrimenti potrebbero venire male interpretati o addirittura potrebbero passare inosservati. Lo studio dei primi stadi di crescita di alcune specie di Stylasteridae ha mostrato come in quest’ultime il primo step sia la formazione di un ciclosistema primario, anche nel caso in cui da adulte esse presentino una differente distribuzione di pori. Questi dati hanno portato a due ipotesi: 1. ciclosistema come distribuzione tipica dei pori dall’antenato di questa famiglia; 2. ciclosistema come miglior tipo di distribuzione per la protezione del primo gastrozoide da parte dei dattilozoidi. Il presente studio riporta, inoltre, la dettagliata descrizione della modalità di crescita di due specie di Distichopora, dalla formazione del ciclosistema primario fino alla formazione della colonia adulta che presenta una distribuzione di pori in file. Sono stati condotti degli studi anche dal punto di vista della riproduzione. Uno studio preliminare ha consentito di capire in dettaglio la morfologia e lo sviluppo dei gonofori di quattro specie di Stylasteridae indonesiani. Inoltre, attraverso uno studio ultrastrutturale, sono stati descritti alcuni step della spermatogenesi, fino al differenziamento degli spermatozoi, in una specie di Distichopora. Lo studio effettuato in merito alla fauna associata ha messo in luce la simbiosi di alcune specie di Stylasteridae con i cirripedi lepadomorfi. Inoltre, è stato dimostrato come gli Stylasteridae, nonostante il loro scheletro calcareo, non siano facilmente attaccabili da parte delle spugne perforatrici.<br>Stylasteridae is one of the two hydroid families having hard, calcareous skeleton. The stylasterids are polymorphic hydroids having two different kinds of polyps lodged in pores. The distribution of the pores over the coenosteum and their shapes are features strictly related to the genera. All the polyps of a colony are connected by a network of coenosarcal canals that densely perforate the coenosteum. The morphology of the stylasterid skeleton was finely investigated for the first time using the X-ray computed microtomography technique (μCT). The utility of this technique for the non-destructive study of coral morphology was showed, demonstrating the benefit of the integrated analysis of pictures produced by X-ray μCT and the traditional SEM techniques in coral taxonomy. Indeed the combined results allow the identification of morphological characters that otherwise could be misidentified or even could pass unnoticed. The observation of post-larval specimens belonging to several species that when adult show pores arranged in rows, in cyclostystems or without coordination revealed that they invariably produce a primary cyclosystem. These data lead to the hypothesis that the cyclosystem represents the pore organisation of the family ancestor or that this organisation provides greater protection to the young gastrozooid by the dactylozooids. The present study reports also the first detailed description of the growth stages of two Distichopora species showing the formation of a primary cyclosystem and the description of the growth process from primary cyclosystem to adult pore organisation. From the reproductive point of view a preliminary survey was carried out about the morphology of the reproductive structures and the development of the gonophores of four Indonesian species. In addition for the first time a detailed description, at ultrastructural level, of some steps of the spermatogenesis up to spermatozoa differentiation in a Distichopora species was provided. The study of the associated fauna showed the first evidence of stylasterids associated to goose barnacles. Moreover the survey concerning the association between sponges and stylasterid corals reveled no specific association and generally the recorded sponges bore only the dead portion of the colonies not enveloped by living epithelium and lacking the coenosteal stolon network.

O aprofundamento de estudos faunísticos e taxonômicos é essencial para a inferência de áreas de distribuição geográfica e, conseqüentemente, de áreas de endemismo. Estes estudos são incipientes para o ambiente marinho, incluindo o sudoeste do Atlântico, particularmente em relação aos cnidários. Os principais objetivos deste estudo foram (1) levantar a fauna de hidróides bentônicos da região entre Cabo Frio (Brasil) e Terra do Fogo (Argentina) e (2) inferir a distribuição geográfica das espécies levantadas, buscando uma eventual caracterização de áreas de endemismo. No total, 181 morfoespécies de hidróides foram registradas, sendo que destas, 10 são registros novos para a região (Aglaophenia trifida, Antennella secundaria, Cryptolarella abyssicola, Filellum contortum, Lafoea coalescens, Lovenella gracilis, Macrorhynchia grandis, ?Nemertesia ciliata, Sertullarella leiocarpa e Zygophylax sibogae) e 9 são espécies endêmicas (Corymorpha januarii, Ectopleura obypa, Eudendrium caraiuru, Hydractinia uniformis, Lytocarpia canepa, Parascyphus repens, Plumularia insignis, Ralpharia sanctisebastiani, Symplectoscyphus magellanicus) para a área. A riqueza de espécies teve uma pequena diminuição com o aumento da latitude e diminuiu drasticamente em águas mais profundas (abaixo das isóbatas de 100 e 1000m). A análise de PCA demonstrou que os substratos Algae, Hydrozoa, Mollusca, Porifera e Rocha apresentaram os maiores números de ocorrência de morfoespécies de hidróides. A análise de cluster resultou na delimitação de três grupos de fauna: (1) brasileiro costeiro, (2) uruguaio-argentino e (3) oceânico contínuo por toda a área amostrada. Em relação às áreas de endemismo, as análises com o NDM-VNDM resultaram em duas principais áreas endêmicas costeiras para o litoral do Brasil (entre 22-24°S 43-46°W e entre 26-29°S 48-49°W), sendo que a metodologia PAE resultou em quatro áreas endêmicas para a região de estudo: (1) áreas costeiras contínuas para o Brasil ou Argentina; (2) áreas costeiras e contínuas entre o Brasil e Argentina; (3) áreas oceânicas contínuas entre Cabo Frio e Terra do Fogo; (4) áreas restritas à região do rio da Prata. Nossos resultados revelaram que a correspondência entre as faunas de profundidade brasileira e de regiões mais rasas do litoral argentino pode estar relacionada com o regime de frentes oceânicas atuantes no sudoeste do Atlântico. Além disso, análises incluindo exclusivamente espécies de hidróides que produzem medusa em seus ciclos de vida resultaram em áreas de endemismo mais restritas à costa em relação às espécies que formam somente gonóforos fixos. Estes resultados contradizem o paradigma clássico que associa a presença de medusa com a alta capacidade dispersiva das espécies.<br>Increasing on faunistic and taxonomic knowledge is essential for reliable inferences on the geographical distribution and, consequently, on areas of endemism. This knowledge is incipient for the marine realm, including southwestern Atlantic, and particularly poor for cnidarians. The main goal of this study was (1) to survey the fauna of benthic hydroids from the region between Cabo Frio (Brasil) and Terra do Fogo (Argentina), and (2) to infer the geographic distribution of the surveyed species, aiming to propose areas of endemism. A total of 181 morphospecies of hydroids was recorded, 10 species are new records (Aglaophenia trifida, Antennella secundaria, Cryptolarella abyssicola, Filellum contortum, Lafoea coalescens, Lovenella gracilis, Macrorhynchia grandis, ?Nemertesia ciliata, Sertullarella leiocarpa e Zygophylax sibogae) and 9 are endemic species (Corymorpha januarii, Ectopleura obypa, Eudendrium caraiuru, Hydractinia uniformis, Lytocarpia canepa, Parascyphus repens, Plumularia insignis, Ralpharia sanctisebastiani, Symplectoscyphus magellanicus) for the area. Species richness slightly decreases along higher latitudes and along deeper waters (below 100 and 1000m isobaths). A PCA analyses has demonstrated that the substrata, Algae, Hydrozoa, Mollusca, Porifera and Rock showed a higher number of morphospecies of hydroids. Cluster analysis resulted in three faunistic groups: (1) Brazilian-coastal, (2) Uruguayan-Argentinean and (3) and oceanic group continuous along the entire surveyed area. Concerning areas of endemism, NDM-VNDM analyses resulted in two main coastal areas of endemism on the Brazilian coast (between 22-24°S 43-46°W and between 26-29°S 48- 49°W), and PAE resulted in four areas of endemism for the studied area: (1) coastal area in Brazil or Argentina; (2) a coastal and continuous area along Brazil and Argentina; (3) an oceanic and continuous area; (4) a Rio de La Plata area. Our results have shown that faunal affinities between Brazilian deep fauna and Argentinean shallow water fauna might be related to the marine fronts present in the southwestern Atlantic. Moreover, analyses exclusively including hydroid species with medusa in the life cycle resulted in more limited areas of endemism closer to the coast than those analyses exclusively including hydroids species with fixed gonophores. These results contradict the classical paradigm associating the presence of medusa and higher dispersive capabilities of the species.

A epibiose é um fenômeno que inclui epizoísmo (organismos que utilizam animais como substrato) e epifitismo (organismos que utilizam vegetais como substrato). Especificamente para Hydrozoa, há diversos tipos de associação destes com outros animais (e.g., moluscos, crustáceos, poríferos e ascídias), em uma relação conhecida como epizoótica ou epizóica. De maneira geral, as larvas plânulas de hidróides ou outras formas de dispersão, como frústulas e pólipos desprendidos, podem fixar-se e crescer em quase qualquer animal macroscópico do bentos marinho, incluindo outros hidróides, simplesmente usando-os como um substrato conveniente. Há duas formas de expressão do epizoísmo em Hydrozoa: (1) quando os mesmos são substratos de outros animais e (2) quando eles exploram um animal como substrato. A segunda acepção proposta, em que hidróides colonizam outros animais usando-os como substrato, foi o foco deste estudo. A primeira acepção só será incluída neste estudo quando houver hidróides que utilizam outros hidróides como substrato. O estudo foi dividido em duas partes, cada uma com objetivos próprios, embora complementares no conhecimento sobre os hidróides epizóicos. A primeira parte, o estudo faunístico, objetiva primeiramente o levantamento das espécies de hidróides epizóicos e da fauna utilizada como substrato por meio do estudo de coleções de museus e materiais coletados em pontos do litoral de Santa Catarina e São Paulo, e de registros citados na literatura. A segunda parte, o estudo de dinâmica da comunidade de hidróides epizóicos, objetiva investigar as associações com substratos animais quanto à sazonalidade de ocorrência, reprodução e ocupação por hidróides epizóicos, por meio de experimento em campo com placas de recrutamento no canal de São Sebastião. No estudo faunístico foram encontradas 117 espécies epizóicas que utilizaram como substratos representantes de duas classes de Porifera (Hexactinellida e Demospongiae), 211 espécies que utilizaram como substratos representantes de duas classes de Cnidaria (Anthozoa e Hydrozoa), 143 espécies que utilizaram representantes de duas classes de Mollusca (Bivalvia e Gastropoda), 57 espécies que utilizaram como substratos representantes de duas ordens de Polychaeta (Aciculata e Canalipalpata), 72 espécies que utilizaram representantes de duas classes de Crustacea (Maxillopoda e Malacostraca), 103 espécies que utilizaram representantes das classes Gymnolaemata e Stenolaemata de Bryozoa e 51 espécies que foram encontradas sobre representantes de três ordens de Ascidiacea (Aplousobranchia, Phlebobranchia e Stolidobranchia). Os aspectos biológicos das associações foram discutidos nos capítulos referentes a cada tipo de substrato animal. Já no estudo de dinâmica das comunidades bentônicas, foram caracterizados hidróides epizóicos de 25 espécies, e estes utilizaram substratos dos filos Porifera, Cnidaria, Mollusca, Arthropoda (Crustacea), Annelida (Polychaeta), Bryozoa e Chordata (Ascidiacea). Os agrupamentos de substratos encontrados na análise de correspondência parecem estar relacionados a características morfológicas dos substratos. Já os fatores biológicos e temporais influenciaram a sucessão ecológica das placas experimentais. No capítulo de considerações finais, os dados sobre epizoísmo dos capítulos de faunística e dinâmica, além de dados referentes a substratos menos freqüentes (não apresentados nesta dissertação), foram reunidos para uma análise de aspectos mais globais do epizoísmo de hidrozoários. Assim, possíveis padrões das famílias de hidróides epizóicos puderam ser definidos (em agrupamentos de especialistas, generalistas ou exclusivos de alguns substratos animais) e discutidos<br>2.1 The associations between animal groups and species of sponges are relatively well known and described in the literature. Of all the cnidarian groups, the most diverse associations with sponges are found among the hydrozoans. In this study, 117 species of epizoic hydroids were found on two classes of sponge substrates (Hexactinellida and Demospongiae). The biological aspects of the interactions between hydrozoans and sponges were discussed in this chapter. 3.1 Many studies describe the association between cnidarians and other organisms, even other cnidarians. In this study, 211 species of epizoic hydroids were found on two classes of cnidarian substrates (Anthozoa and Hydrozoa). The biological aspects of the interactions between hydrozoans and other cnidarians were discussed in this chapter. 4.1 The Phyllum Mollusca is one of the main groups that hydrozoans have ecological associations. On soft-bottom environments, the shells are an alternative for the organisms that need hard susbtrates to settle and grow. In this study, 143 species of epizoic hydroids were found on two classes of mollusc substrates (Bivalvia and Gastropoda). The biological aspects of the interactions between hydrozoans and molluscs were discussed in this chapter. 5.1 The polychaetes are abundant in different habitats and can be associated with many animals, even hydroids. In this study, 57 species of epizoic hydroids were found on two orders of polychaetes substrates (Aciculata and Canalipalpata). The biological aspects of the interactions between hydroids and polychaetes were discussed in this chapter. 6.1 The crustacean can be used as substrates, being their bodies and appendages overgrown by hydroid polyps. Another form of association found in the literature is indirect: the polyps grow over the gastropod shells occupied by hermit crabs. In this study 72 species of epizoic hydroids were found using two classes of Crustacea (Maxillopoda and Malacostraca) as substrates. The biological aspects of the interactions between hydroids and crustaceans were discussed in this chapter. 7.1 The bryozoan colonies grow on many substrates like rocks, algae, shells, crustaceans, ascidians, hydroids, and are important fouling members that grow on artificial substrates. However, they can also serve as substrate for other animals, even hydroids. In this study, 103 species of epizoic hydroids were found on two classes of bryozoan substrates (Gymnolaemata and Stenolaemata). The biological aspects of the interactions between hydroids and bryozoans were discussed in this chapter. 8.1 The most common commensal organisms of ascidians cited in the literature are copepods, molluscs, polychaetes, nemertines and there are records of endosymbiotic hydroids. The associations between ascidians and hydroids were listed in this study, and 51 species of epizoic hydroids were found on three orders of ascidian substrates (Aplousobranchia, Phlebobranchia e Stolidobranchia). The biological aspects of the interactions between hydroids and ascidians were discussed in this chapter. 9.1 Studies on the colonization of artificial substrates are quite common in the literature. In this study, we used ceramic panels in São Sebastião, SP, in order to observe the hydroid epizoic community and their animal substrates. Twenty-five species of epizoic hydroids were found on substrates of Porifera, Cnidaria, Mollusca, Arthropoda (Crustácea), Annelida (Polychaeta), Bryozoa and Chordata (Ascidiacea). The groups of substrates defined by the correspondence analysis seem to be related to the morphological features of the substrates, and the biological and temporal factors seem to influence the ecological succession of the experimental panels.