No description available.

Adula (Botula) falcata Gould (Soot-Ryen, 1955) lives commonly as a byssally attached rock borer in soft mudstone reefs at Bolinas and Moss Beach, California (Figure 1). Keen (1963) reports that Adula falcata has been collected from the intertidal to a depth of ten fathoms. Its distribution is from Coos Bay, Oregon, to Cape San Lucas, Lower California (Hertlein and Strong, 1946), and collection data indicate a range as far south as Peru (Soot-Ryen, 1955). While is possesses the protective advantage of living cryptically, Adula falcata is subjected to an environmental stress not faced by epifaunal mytillids; namely, it must function within a burrow into which sediment material is being continuously deposited from both particle laden water passing over its burrow entrance and the mudstone byproducts of its own mechanical boring. The following is a comparative study on the ciliary mechanisms of feeding, digestion, and sediment removal in Adula falcata. Sediment removal could hardly be considered separately from feeding and digestion, as it is during these latter two processes that sediment is resolved from potential food material and extruded from the burrow. Aside from publications of a purely taxonomic nature, the sole direct references to Adula falcata have been in Lloyd’s (1897) observations on lamellibranch rock boring and Yonge’s (1955) comprehensive work on the adaptation and evolution of the boring habit in the Family Mytilidae. It was, in fact, Yonge’s observations on the role of Figure 1. A lateral view of the burrow of Adula falcata. The mudstone burrow has been cracked open to expose the left side of the enclosed bivalve. This byssally attached mussel had withdrawn from the head of the excavation and had extended its siphonal process for feeding. Other noteworthy features include the furry incrustation on the posterodorsal triangle of the valve and a partially eroded umbone.

El cultivo de mejillón en la Argentina es un recurso de alta potencialidad productiva y económica. Una de las principales limitantes para la expansión de esta actividad se encuentra en la provisión de juveniles para la cría y engorde, comúnmente denominados “semilla”. En el golfo San Jorge, Chubut, existe una serie de iniciativas productivas que enfrentan el interrogante de si es posible la captación natural de juveniles de mejillón en colectores artificiales. Hasta el momento, la semilla utilizada en los emprendimientos que se ubicaron en esta área geográfica proviene de criadero o de la recolección de la región del intermareal rocoso de los alrededores de los sitios en producción, como así también de otros sitios ubicados en la costa argentina. En esta investigación se trabajó en dos sitios de estudio cercanos entre sí, pero de características de exposición y morfología costera diferentes. Ambos sitios se hallan en las cercanías de la ciudad de Comodoro Rivadavia. El objetivo general fue conocer si existía el fenómeno de captación en la región central costera del golfo San Jorge. Para ello se instaló en el mar una serie de colectores de remplazo bimestral que dieron como resultado la existencia de un pulso de captación principal a fines del verano-comienzo del otoño. También se estudió el ciclo sexual del mejillón, inferido a partir de las variaciones de su peso seco, obteniendo dos posibles periodos de desove, el primero a fines de primavera-principios de verano y el segundo de ellos, a comienzos del otoño. Otro objetivo específico de esta tesis fue el monitoreo de variables ambientales durante el periodo de estudio y, a partir de los datos obtenidos, desarrollar un modelo estadístico predictivo para la captación, que contemplara las variables que resultaran más relevantes. Dicho modelo presentó como variables predictoras la temperatura como factor de mayor influencia, la concentración de materia orgánica en el agua de mar y la variación del peso seco de los mejillones con un corrimiento de un mes. Asimismo se evaluó también el posible efecto de la morfología costera sobre el fenómeno de asentamiento postlarvario. Para ello se seleccionaron dos sitios a distinta distancia de geoformas costeras; el sitio Belvedere fue seleccionado por su menor exposición y por su cercanía a una prolongación del continente hacia el mar, y el sitio Km 3, por su mayor exposición y por su lejanía a geoformas costeras. Los resultados indicaron que en Belvedere se encontraron mayores captaciones que en Km 3, indicando que la geomorfología costera tendría un efecto sobre la captación. Se efectuó un análisis de las corrientes marinas locales en ambos sitios, observándose diferencias en el comportamiento de las direcciones de las corrientes. Por otro lado se analizó el efecto de la profundidad sobre la densidad de individuos captados, colocando colectores a tres profundidades diferentes; no se detectaron variaciones significativas en la densidad de individuos captados por efecto de la profundidad, pero sí en el tamaño de los mismos, que presentaron tallas mayores a profundidades menores. Se identificaron las postlarvas captadas mediante diferentes técnicas que resultaron satisfactorias, encontrándose un criterio clasificatorio distintivo para las postlarvas de mejillón. Por último, se realizó una determinación de la epibiosis hallada en los colectores durante el estudio, con la finalidad de reconocer especies competidoras y facilitadoras del asentamiento de postlarvas.

Rates of uptake of organic and inorganic suspended particulate material by suspension feeding bivalve molluscs have been studied since the nineteenth century (see Viallanes, 1892) . Studies have investigated molluscan feeding mechanisms, filtration capabilities, food assimilation and metabolism. The bulk of this work has been directed towards the mussel Mytilus edulis Linnaeus and the oyster Crassostrea virginica Gmelin (see reviews by Galtsoff, 1964; Ali, 1970; Jorgensen, 1975; 1976; and Winter, 1978). More recently the growth of mussels, oysters, clams and scallops has been quantitatively studied in controlled systems to assess the biological potential of these molluscs in an aquaculture setting (Hartman et al., 1973; Tenore & Dunstan, 1973; Tenore et al., 1973; Kirby-Smith & Barber, 1975; Walne & Spencer, 1974; Epifanio & Ewart, 1977; Winter, 1978). Direct and indirect methods for estimating filtration rates of molluscs (Ali, 1970) have yielded such a wide range of results that the validity of comparisons between different studies is sometimes questionable . Variables such as the mollusc species and size, as well as the nature and concentration of the test suspension contribute to differences in observed filtration rates. The present study simultaneously examined three mytilid speeies of comparable size (85-125 mm shell length) . Each mussel species was tested under the same conditions for its ability to filter and assimilate the unicellular algae Dunaliella primolecta Butcher at suspensions of 5, 12, 25 and 50 x 106cells/1. Filtration rates and food assimilation were determined in test chambers incorporating a new flow-through design which eliminated the possibility of recirculation of the algae test suspension. In previous studies recirculation of the test suspension has occasionally resulted in the under-estimation of filtration rates. Growth comparisons were made among individuals of each species held under the same set of environmental conditions. Two of the mussel species examined in this study, Mytilus edulis L. and Perna canaliculus Gmelin, are presently under cultivation as a human food source. The third species, Mytilus catifornianus Conrad, may be viewed as a potential candidate for aquaculture due to its size, abundance and value as a source of protein. The California mussel, M. catifornianus, is found along the west coast of North America from the Aleutian Islands to Baja California (Soot-Ryen, 1955). The bay mussel, M. edutis , is widespread in the northern and southern hemispheres (Stubbings, 1954). The green-lipped mussel, P. canaliculus, is found throughout New Zealand waters where it colonizes both exposed rocky coasts and quiet bays (Morton & Miller, 1968; Paine, 1971).

Orientador: Antonia Cecília Zacagnini Amaral / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-26T06:06:23Z (GMT). No. of bitstreams: 1 Daolio_RachelFurioso_M.pdf: 2566347 bytes, checksum: 646f1db51330af90d55b405f39cb815b (MD5) Previous issue date: 2014 / Resumo: Os polidorídeos são poliquetas da família Spionidae cuja característica principal é a presença de cerdas em forma de ganchos no 5° setígero. Algumas espécies habitam fundos não consolidados, enquanto que outras, como Polydora neocaeca, habitam substratos consolidados, podendo ou não perfurar estruturas calcárias como corais e conchas de moluscos. A forma de perfuração é pouco compreendida, existindo hipóteses de que seja mecânica, química ou a combinação desses processos. A infestação raramente causa a morte direta dos hospedeiros, porém os torna suscetíveis a outros parasitas e doenças. Por essa razão, os polidorídeos são considerados pestes pela indústria de moluscos. Polydora neocaeca parasita o mexilhão Mytella charruana que pode ser encontrado formando bancos na região entremarés de praias abrigadas. Dois bancos de M. charruana localizados nas praias do Camaroeiro e da Cidade na enseada de Caraguatatuba (Litoral Norte do Estado de São Paulo) foram estudados de março de 2006 a março de 2007. Na porção central de cada banco, foram traçados transectos perpendiculares à linha d¿água, sendo sorteado mensalmente um de cada banco para amostragem. Em cada transecto, substratos de três níveis foram coletados com o auxílio de um delimitador de 0,04 m² para a triagem dos mitilídeos e dos polidorídeos. O presente trabalho teve como objetivo (1) caracterizar as duas áreas de estudo quanto a variáveis ambientais (perfil praial, salinidade da água intersticial, temperaturas do ar e do sedimento e granulometria, teor de calcário e conteúdo de matéria orgânica do sedimento) e estrutura (densidade de M. charruana); (2) analisar a morfometria dos dois grupos de P. neocaeca (do Camaroeiro e da Cidade); e (3) avaliar a biologia populacional destes, incluindo sua dinâmica, estrutura etária, recrutamento, crescimento e mortalidade. O perfil da praia do Camaroeiro permitiu classificá-la como de dissipativa a intermediária e, o da Cidade, como intermediária do tipo terraço de baixamar. A densidade de M. charruana, o conteúdo médio de calcário e a fração do sedimento de silte + argila foram maiores no banco da Cidade. As demais variáveis foram semelhantes entre os dois bancos. O único modelo de crescimento alométrico que apresentou um bom suporte ás medidas morfométricas dos dois grupos de P. neocaeca foi o modelo de dois segmentos. Esses polidorídeos apresentaram alometria negativa, ou seja, ao longo do seu desenvolvimento o aumento no número total de setígeros é proporcionalmente menor do que o aumento no comprimento total. A largura do setígero 5 foi selecionada como a medida parcial mais adequada para a estimativa do tamanho total dos indivíduos. Apesar da diferença estrutural entre os bancos, P. neocaeca apresentou padrão temporal de recrutamento e parâmetros de crescimento semelhantes entre os dois grupos. Isso sugere que há fluxo gênico (via dispersão) entre eles, tratando-se de uma única população. Porém, a abundância, o tamanho médio da largura do setígero 5 e a longevidade desses polidorídeos foram maiores na Cidade, enquanto que sua mortalidade foi maior no Camaroeiro. Essas diferenças estão mais relacionadas á densidade de mitilídeos hospedeiros (maior no banco da Cidade) do que ás demais variáveis analisadas / Abstract: Polydorids are polychaetes from the Spionidae family whose main characteristic is the presence of modified hooks on the 5th setiger. Some species inhabit soft substrata, while others, such as Polydora neocaeca, inhabit hard substrata, boring or not self-excavated burrows on calcareous structures such as corals and mollusk shells. The boring mechanism is poorly understood and might be mechanical, chemical or the combination of these processes. The infestation rarely causes the direct death of hosts, but makes them susceptible to other parasites and diseases. Thus polydorids are considered as pests by the fishery industry. Polydora neocaeca parasites the Mytella charruana mussel, which can be found forming beds on the intertidal region of sheltered beaches. Two M. charruana beds located at the Camaroeiro and the Cidade beaches from Caraguatatuba Bay (North Coast of São Paulo State) were studied from March 2006 to March 2007. On the central portion of each mussel bed, transects were delimited perpendicular to the waterline, with one from each mussel bed being monthly sampled. On each transect, three levels of substrata were collected with a 0.04 m² corer in order to sample the mytilid and the polydorid individuals. This study aimed to (1) characterize the two sites regarding their environmental variables (beach slope, interstitial water salinity, air and sediment temperatures, and sediment granulometry, calcareous content and organic matter) and structure (M. charruana density); (2) analyze the morphometrics of the two groups of P. neocaeca (Camaroeiro and Cidade); and (3) assess the population biology of these groups, including their dynamics, size structure, recruitment, growth and mortality. The Camaroeiro beach slope enabled its classification as a dissipative to intermediate beach, and the Cidade one, as a low-tide terrace intermediate beach. The M. charruana density, the mean calcareous content, and the silt + clay sediment fraction were higher at the Cidade mussel bed. The other variables were similar between the two beds. The only allometric growth model that showed good support as to the morphometric measures of both P. neocaeca groups was the two segments model. These polydorids showed negative alometry, which indicates that, along their development, the total number of setigers increase is proportionately smaller than the total length increase. The width of the setiger 5 was selected as the most appropriate partial measure for estimating the individuals total size. Despite the structural difference between the mussel beds, P. neocaeca presented similar recruitment temporal pattern and growth parameters between the two groups. This suggests that there is a gene flow (by dispersal) between them, which constitute a single population. However, the abundance, the mean width of the setiger 5 and the longevity of these polydorids were higher at Cidade, whereas their mortality was higher at Camaroeiro. These differences are more related to the host density (higher at the Cidade mussel bed) than to the other analyzed variables / Mestrado / Ecologia / Mestra em Ecologia

In marine environments, the open system (OS) theory, whereby populations are assumed to be well connected through large-scale dispersal, is currently being challenged by studies demonstrating limited dispersal. Using a novel metapopulation framework featuring nonequilibrium within-site disturbance cycles and limited dispersal, I investigate the large-scale response of marine mussel populations to changes in oceanographic productivity. By altering the fecundity parameter, I am able to shift from open to dynamically-coupled systems (DCS), thereby generating predictions that can be used to test the connectivity of marine populations. Within-site disturbance cycles scale-up and drive regional dynamics in both OS and DCS. Fast disturbance cycles induce synchronized oscillations that promote regional extinction risk in response to changes in oceanographic productivity for DCS but not OS. Slow disturbance cycles maintain spatial variability and temporal stability in both OS and DCS. These predictions can be used to test the applicability of OS theories to natural coastal ecosystems.

Thesis (M. Sc. (Zoology & Entomology))--Rhodes University, 2005.

Thesis (Ph. D. (Zoology and Entomology))--Rhodes University, 2005.

The discovery of deep-sea chemosynthesis-based ecosystems including hydrothermal vents and cold seeps has greatly expanded our view of life on Earth. Nevertheless, for many benthic organisms in these ecosystems, little is known about where they come from, how scattered populations are connected by larval dispersal, and how they adapt to the local environments. Mussels of Bathymodiolus platifrons (Bivalvia: Mytilidae) are one of the dominant and foundation species in deep-sea chemosynthesis-based ecosystems. They are known to have a wide geographic distribution, and are also one of the few deep-sea species capable of living in both hydrothermal vents [in Okinawa Trough (OT)] and methane seeps [in the South China Sea (SCS) and Sagami Bay (SB)]. Previous population genetics studies of B. platifrons mostly relied on one to several genes, which suffered from the lack of sensitivity required to resolve their fine-scale genetic structure, and were unable to reveal their adaptation to the local environments. With the repaid development of molecular techniques, it is now possible to address their demographic mechanisms and local adaptation from a genome-wide perspective. Therefore, in the first part of my thesis, I aimed to generate genome-wide single nucleotide polymorphisms (SNPs) for B. platifrons via a combination of genome survey sequencing and the type IIB endonuclease restriction-site associated DNA (2b-RAD) approach, assess the potential use of SNPs in detecting fine-scale population genetic structure and signatures of diversifying selection, as well as their cross-species application in other bathymodioline mussels. Genome survey sequencing was conducted for one individual of B. platifrons. De novo assembly resulted in 781 720 sequences with a scaffold N50 of 2.9 kb. Using these sequences as a reference, 9307 genome-wide SNPs were identified from 28 B. platifrons individuals collected from a methane seep in the SCS and a hydrothermal vent in the middle OT (M-OT), with nine outlier SNPs showed significant evidence of diversifying selection. The small FST value (0.0126) estimated based on the neutral SNPs indicated high genetic connectivity between the two populations. However, the permutation test detected significant differences (P < 0.00001), indicating the two populations having clearly detectable genetic differentiation. The Bayesian clustering analyses and principle component analyses (PCA) performed based on either the neutral or outlier SNPs also showed that the two populations were genetically differentiated. This initial study successfully demonstrated the applicability of combining genome sequencing and 2b-RAD in population genomics studies of B. platifrons. Besides, using the survey genome of B. platifrons as a reference, a total of 10 199, 6429, and 3811 single nucleotide variants (SNVs) were detected from three bathymodioline mussels Bathymodiolus japonicus, Bathymodiolus aduloides, and Idas sp. These results highlighted the potential of cross-species and cross-genus applications of the B. platifrons genome for SNV/SNP identification among different bathymodioline lineages, which can be further used in various evolutionary and genetic studies. To have a deeper understanding of how individuals of B. platifrons are connected among and adapt to their habitats, in the second part of my thesis, I used both mitochondrial genes and genome-wide SNPs to conduct a more comprehensive population genetics/genomics study of B. platifrons. Three mitochondrial genes (i.e. atp6, cox1, and nad4) and 6398 SNPs generated by 2b-RAD were obtained from 110 B. platifrons individuals from six representative locations along their known distribution range in the Northwestern Pacific. The small FST values based on both types of genetic markers all revealed high genetic connectivity of B. platifrons, which may have been driven by the strong ocean currents (i.e. Kuroshio Current, North Pacific Intermediate Water). However, when using SNP datasets rather than mitochondrial genes, individuals in the SCS were identified as a distinct genetic group, indicating the Luzon Strait may serve as a dispersal barrier that limits their larval exchange between the SCS and the open area in the Northwestern Pacific. Moreover, a genetic subdivision of B. platifrons in the southern OT (S-OT) from those in M-OT and SB was observed when using 125 outlier SNPs for data analyses. The outlier-associated proteins were found to be involved in various biological processes, such as DNA and protein metabolism, transcription and translation, and response to stimulus, indicating local adaptation of B. platifrons even they are confronted with extensive gene flow in the OT-SB region. Furthermore, by using SNP datasets, populations in S-OT were revealed to be the source of gene flow to those in the SCS, M-OT, and SB. Overall, these results offered novel perspectives on the potential forces that may have led to the genetic differentiation and local adaptation of B. platifrons, which can serve as an example for other deep-sea species with high dispersal potential, and contribute to the designation of marine protected areas and conservation of deep-sea chemosynthesis-based ecosystems. Molluscan shell formation is one of the most common and abundant biomineralization processes in metazoans. Although composed of less than 5 wt% of the molluscan shells, shell matrix proteins (SMPs) are known to play multiple key roles during shell formation, such as providing a gel-like micro-environment to favour mineral precipitation, promoting crystal nucleation, as well as guiding and inhibiting crystal growth. To date, all studies on SMPs have focused on molluscs in terrestrial and shallow-water ecosystems with no reports for those living in the deep ocean. Herein, the third part of my thesis was to study the shell proteomes of B. platifrons and its shallow-water relative Modiolus philippinarum with the aim to bridge such knowledge gaps in biomineralization studies. A total of 94 and 55 SMPs were identified from the shell matrices of B. platifrons and M. philippinarum, respectively, with 31 SMPs shared between two species. These SMPs can be assigned into six broad categories, comprising calcium binding, polysaccharide interaction, enzyme, extracellular matrix-related proteins, immunity-related proteins, and those with uncharacterized functions. Many of them, such as tyrosinases, carbonic anhydrases, collagens, chitin-related proteins, peroxidases, as well as proteinase and proteinase inhibitor domain-containing proteins, have been widely found in molluscan shell matrices and other metazoan calcified tissues (e.g. exoskeletons of corals, tubes of tubeworms), whereas some others, such as cystatins, were found for the first time in molluscan shell matrices, and ferric-chelate reductase-like proteins and heme-binding proteins were to be detected for the first time in metazoan calcified tissues. This is the first report of the shell proteome of deep-sea molluscs, which will support various follow-up studies to better understand the functions of these SMPs, especially in relation to environmental adaptation. Overall, my population genetics/genomics studies have improved our understanding of the population dynamics, genetic connectivity, fine-scale genetic structure, and local adaptation of B. platifrons in the Northwestern Pacific, and my proteomics study has shed light on the biomineralization processes of molluscs in the deep ocean.

No description available.