Texte remanié de: Dissertation--Philologie--Sibiu--Universitatéa Lucian Blaga, 2007. / Bibliogr. p. 275-305.

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Large individuals of the sea anemone <i>Actinia fragacea</i> were collected at approximately monthly intervals over a two year period. Their gonads were examined by light and electron microscopy, in order to follow the gametogenic process. The sexes are separate, and both show an annual cycle of activity. Oocytes arise in the gonad epithelia, but soon migrate into the mesogloea. During vitellogenesis, the oocytes accumulate compound yolk granuleso fibrillar and cortical granules, lipid droplets and glycogen. The surface of large oocytes bears tufts of large microvilli or cytospines. The oocytes reach some 150 pm in size. A group of specialized gonad epithelial cells projects through the mesogloea and contacts the oocyte surface, forming the trophonema, which is involved with nutrient transfer. The gonad epithelium can take up nutrients from the external medium, and the trophonema is particularly active in the uptake and incorporation of some small molecules. Not all fully grown oocytes are always spawned; some break down in an orderly fashion and are resorbed. Oogenesis was also examined, in less detallo in four other species of anemone. Spermatogenesis takes place in spherical testicular cysts, which are also associated with trophonemata. Spawning occurred in the laboratory on three occasions. Spawned eggs do not possess a vitelline coat, and do not undergo a cortical reaction. Gastrulae may take up numerous supernumary sperm.

Seagrass bed is a highly productivity ecosystem, it also provides habitats for animals and plays an important role in stabilizing the substrate. The sea anemone Phymanthus strandesi is very abundant in the seagrass bed of Thalassia hemprichii on Hsiao-Liuchiu Island. Structural Equation Modeling (SEM) was used to investigate the relationship between P. strandesi and some environmental factors, which affect the distribution of this species at Tuozaiping tidal flat (N 22¢X20"55' E 120¢X21"49'), Hsiao-Liuchiu Island. Light and temperature were also manipulated in the laboratory to test their effect on the hiding response of P. strandesi. The results of SEM show that the abundance of T. hemprichii showed very weak positive relation with P.strandesi. On the other hand, soil depth on the seagrass bed might be the main factor that affects the distribution of P. strandesi. In high a temperature situation (i.e. over 38¢XC), all the sea anemones in the experimental container hided into the sand. However, only some sea anemones hid when exposed to strong light (i.e. 5030 lum/ft²) after one and half hours.

A fundamental question of evolutionary ecology is, what determines body size? In general, the body size of vertebrates is thought to be relatively inflexible, a product of their genes, food, environment, and stress. However, vertebrate growth can be plastic in response to population interactions such as predator-prey and competition. While these relationships can elicit plasticity of vertebrate growth, mutualistic relationships have yet to be investigated. An iconic example of mutualism involving a vertebrate is the relationship between anemone and anemonefish. In this interaction anemonefish size is often positively correlated with anemone size. Here, I test the hypothesis that anemonefish growth is a plastic response to variation in anemone size. Juvenile clownfish (Amphiprion percula) of relatively uniform size were paired with sea anemones (Entacmaea quadricolor) of variable size and monitored over three months. The average anemone size over the course of the month was then used to predict the fish growth each month. Mixed model analyses verified that anemone area is significantly associated with both change in fish standard length and change in fish body depth. Fish in larger anemones grew more than did fish in small anemones. Remarkably, individuals in large anemones achieved this despite receiving the same amount of food as individuals in small anemones. This clownfish growth plasticity in response to anemone size might be adaptive if anemone area is a good indicator of resource availability in the wild, because it would enable the fish to maximize their reproduction without compromising survival. This study extends the understanding of how plasticity of vertebrate species can be influenced by a wide variety of population interactions.

Life histories unfold within the ecological context of an organism's environment, and thus are intimately linked to organismal fitness. The evolution of alternate life history strategies, either within or between taxa, can profoundly affect ontogeny, ecology, and population dynamics. Many cnidarians (sea anemones, corals, jellyfish, etc.) exhibit complex life histories involving sexual reproduction and multiple modes of asexual reproduction. Sea anemones of the family Edwardsiidae exemplify this complexity, and are therefore an attractive system for studying the developmental and ecological ramifications of life history evolution. I used intra- and interspecific comparisons of two Edwardsiid anemones, Edwardsiella lineata, and Nematostella vectensis to investigate alternative life histories using a multifaceted approach that included field-based ecological surveys, functional genetics, transcriptomics, and phylogenetics. Both anemones are capable of sexual and asexual reproduction. N. vectensis produces a rapidly maturing direct developing larva. By contrast, E. lineata has evolved a new larval stage that parasitizes the ctenophore, Mnemiopsis leidyi. Through fieldwork surveys and laboratory culture, I documented several life history traits, such as a previously un-characterized, pre-parasitic larval stage, and the developmental dynamics of early-stage parasitic infections, that augmented gaps in our knowledge of E. lineata's life history. To better understand how and when E. lineata evolved its novel, parasitic life history, I worked with collaborators in the Finnerty lab to sequence, assemble and annotate the transcriptome. Through a multigene molecular clock approach, enabled by the E. lineata transcriptome assembly, I estimated the divergence date for these two anemones between 215-364 million years ago, thereby establishing an upper bound for the innovation of E. lineata's derived, parasitic life history. Testing a hypothesis that Wnt signaling, which patterns the oral-aboral (OA) axis during embryogenesis, also patterns the OA axis during regeneration, I demonstrated that canonical Wnt signaling is sufficient for oral tissue fate across alternate life histories (embryogenesis and regeneration) of N. vectensis. Taken together, these dissertation research activities constitute an integrative approach to investigating the evolution of life histories, and are a step towards establishing E. lineata and N. vectensis as models for studying the evolutionary developmental mechanisms of parasitism and regeneration.

Made available in DSpace on 2014-06-11T19:23:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-11-24Bitstream added on 2014-06-13T19:49:43Z : No. of bitstreams: 1 pigossi_ft_me_araiq.pdf: 1126356 bytes, checksum: 760162fd7a380d3e6dcbce0c956356a5 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A Stichodactyla helianthus é uma anêmona relativamente abundante nos mares de Cuba apresentando grande potencialidade como fonte de peptídeos biologicamente ativos. Dentre estes peptídeos, estão duas citolisinas: as esticolisinas I (St I) e II (St II). Essas duas toxinas possuem como principal característica a capacidade de formação de poros em eritrócitos, ou seja, alta atividade hemolítica (AH), no entanto a St II é mais hemolítica que a St I. Tendo em vista que as principais alterações que diferenciam estas citolisinas (St I e St II) estão na região amino-terminal (primeiros 30 resíduos), este trabalho teve como um dos objetivos sintetizar e comparar fragmentos amino-terminais destes polipeptídeos, visando entender a diferença de atividade hemolítica. Os resultados obtidos mostraram que os peptídeos St I 12-31 e St II 11-30 possuem a mesma atividade hemolítica. Esse dado mostra que a alteração de Glu por Gly e de Gln por Glu não afeta a atividade hemolítica dos mesmos. Já os peptídeos St I 1-31 e St II 1-30, respectivamente, mostraram diferenças em suas atividades hemolíticas, estas diferenças de atividade podem estar relacionadas à região dos resíduos de 1 a 10 da seqüência peptídica. Outro resultado interessante foi que o peptídeo St I 2-31 (sem o resíduo de serina N-terminal) apresentou AH intermediária entre os St I 1-31 e St II 1-30, mostrando que a adição da serina à St I é responsável por parte da perda da atividade desta citolisina. Outro objetivo deste trabalho foi avaliar a importância da polaridade da extremidade amino-terminal da esticolisina II. Para isto, fragmentos peptídicos contendo a região amino-terminal da St II, marcado com Trp na posição 2, foi sintetizado alterando-se a carga desta extremidade (acetilado, acrescido de Ser, Asp ou Lys) / Stichodactyla helianthus is a relatively abundant sea anemone found in the seas of Cuba, presenting a largely potent source of biologically active peptides. Among these peptides, are two citolysins: the sticholysins I (St I) and II (St II). These two toxins possess as main characteristic the capacity of forming pores in erythrocytes, in other words, high hemolytic activity (HA), however, the St II is more hemolytic than the St I. As far as we know that the main alterations that differentiate the proteins St I and St II are in the region amino-terminal (first 30 residues), this study has as one of the objectives the synthesizing and comparing of amino-terminal fragments of those polypeptides aiming to understand the difference of hemolytic activities. The results obtained had shown that the peptides St I 12-31 and St II 11-30 possess the same hemolytic activity. This data sample shows that the alteration of Glu for Gly and Gln for Glu does not affect the hemolytic degree of the same ones. Even then the peptides St I 1-31 and St II 1-30, respectively, had sample differences in its hemolytic activity, indicating that the different activities can be related within the region of 1 the 10 of the sequence. Another interesting result was that the peptides St I 2-31 (without the serine residue N-terminal) presented intermediary AH between St I 1-31 and St II 1-30, showing that the addition of the serine to St I is responsible for part of the losing activity in this citolysin. Another objective of this study is to evaluate the importance of polarity of the extremity amino-terminal of sticholysin II. To do this, the peptides containing the region amino-terminal of St II, marked with Trp in position 2, was synthesized changing the load of this extremity (acetylated, increased of Ser, Asp or Lys)

Anemonefish are one of the main groups that have been used over the last decade to empirically measure larval dispersal and connectivity in coral reef populations. A few species of anemones are integral to the life history of these fish, as well as other obligate symbionts, yet the biology and population structure of these anemones remains poorly understood. The aim of this study was to measure the genetic structure of these anemones within and between two reefs in order to assess their reproductive mode and dispersal potential. To do this, we sampled almost exhaustively two anemones species (Stichodactyla gigantea and Heteractis magnifica) at two small islands in Kimbe Bay (Papua New Guinea) separated by approximately 25 km. Both the host anemones and the anemonefish are heavily targeted for the aquarium trade, in addition to the populations being affected by bleaching pressures (Hill and Scott 2012; Hobbs et al. 2013; Saenz- Agudelo et al. 2011; Thomas et al. 2014), therefore understanding their biology is crucial for better management strategies. Panels of microsatellite markers were developed for each species using next generation sequencing tools. Clonality analyses confirm six pairs of identical genotypes for S. gigantea (n=350) and zero for H. magnifica (n=128), indicating presence/absence of asexual reproduction in this region. S. gigantea showed low structure between islands (FST= 0.003, p-value= 0.000), however, even if the majority of the individuals were unrelated (r~0), 81 families that shared 50% of their genetic material formed from two to four members were found. Out of these families, 45% were found with individuals only within Tuare Island, 11% only in Kimbe Island, and 44% were sharing individuals among islands. In comparison, H. magnifica showed no structure (FST= 0.002, p-value= 0.278), mean relatedness indicated the majority of individuals were unrelated, and 31 families were identified. Families again consisted from two to four members and were found within Kimbe Island 90% of the time, and shared between islands the remaining 10%. Results show the first genetic evidence of their reproductive characteristics, high levels of connectivity among islands and significant levels of genetic relatedness among individuals within islands.

Broad-scale population genetics can reveal population structure across an organism’s entire range, which can enable us to determine the most efficient population-wide management strategy depending on levels of connectivity. Genetic variation and differences in genetic diversity on small-scales have been reported in anemones, but nothing is known about their broad-scale population structure, including that of “host” anemone species, which are increasingly being targeted in the aquarium trade. In this study, microsatellite markers were used as a tool to determine the population structure of a sessile, host anemone species, Heteractis magnifica, across the Indo-Pacific region. In addition, two rDNA markers were used to identify Symbiodinium from the samples, and phylogenetic analyses were used to measure diversity and geographic distribution of Symbiodinium across the region. Significant population structure was identified in H. magnifica across the Indo-Pacific, with at least three genetic breaks, possibly the result of factors such as geographic distance, geographic isolation and environmental variation. Symbiodinium associations were also affected by environmental variation and supported the geographic isolation of some regions. These results suggests that management of H. magnifica must be implemented on a local scale, due to the lack of connectivity between clusters. This study also provides further evidence for the combined effects of geographic distance and environmental distance in explaining genetic variance.