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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
101

Spatial variation in Cellana grata populations: the interplay of population dynamics and foodavailability

黃道全, Huang, Richard. January 2001 (has links)
published_or_final_version / Ecology and Biodiversity / Doctoral / Doctor of Philosophy
102

Estudos ecológicos e ecotoxicológicos de Melanoides tuberculata Müller, 1774 (Gastropoda, Thiaridae), espécie exótica para a região neotropical / Ecological and ecotoxicological studies of Melanoides tuberculata Müller 1774 (Gastropoda, Thiaridae), exotic species for neotropical region

Okumura, Denise Tieme 07 June 2006 (has links)
As introduções de espécies exóticas têm significantemente modificado a estrutura das comunidades levando à extinção muitas espécies nativas. A crescente invasão, nas águas doces brasileiras pelo gastropoda Melanoides tuberculata, de origem africano-asiática, é preocupante. No presente estudo foram analisados diversos aspectos referentes ao ciclo de vida, à tolerância a variáveis abióticas e à sensibilidade a substâncias tóxicas de referência e aos sedimentos contaminados de três reservatórios do estado de São Paulo (Rasgão, Barra Bonita e Promissão). Testou-se a eficácia do látex de Euphorbia splendens e de Asclepias curassavica como moluscicida. Os moluscos foram coletados em tanques de piscicultura, em Pirassununga, SP, e cultivados em laboratório, determinando-se a taxa de crescimento e a tolerância à temperatura e à salinidade. Os resultados evidenciaram que esta espécie tolera temperaturas entre 16 e 37 'graus' C e tem ampla tolerância à salinidade (0,968 a 17,138 g/L). As 'CL IND.50' para substâncias de referência foram: 0,734 mg/L para o dicromato de potássio; 0,701 g/L para o cloreto de potássio e de 9,053 g/L para o cloreto de sódio. Em relação ao látex de plantas tóxicas, obtiveram-se 'CL IND.50' entre 2,924 ppm e 3,308 ppm para Euphorbia splendens, enquanto o látex de Asclepias curassavica não foi tóxico até o limite máximo de 20,0 ppm. Os sedimentos dos reservatórios de Barra Bonita e Promissão (rio Tietê) não foram tóxicos, enquanto o sedimento de Rasgão foi extremamente tóxico a este molusco. Concluiu-se que a alta tolerância de M. tuberculata a elevadas temperaturas e à salinidade corroboram sua ampla e rápida dispersão pelas águas doces tropicais e que o látex de Euphorbia splendens pode ser utilizado como moluscicida natural em baixas concentrações em programas integrados de controle da invasão desta espécie invasora / The introduction of exotic species have marcantly altered the structure of communities, leading to the extinction of many native species. The progressive invasion of brazilian freshwaters by the gastropoda Melanoides tuberculata, with afro-asian origin, is quite worrying at the moment. In the present study some aspects of the life cycle of M. tuberculata, its tolerance to abiotic variables and its sensibility to both toxic reference substances and contaminated sediments from São Paulo state reservoirs (Barra Bonita, Promissão and Rasgão) were evaluated. It was also tested the efficiency of the latex of Euphorbia splendens and Asclepias curassavica as natural moluscicids. Moluscs were collected from fish ponds in Pirassununga, SP, and cultured in the laboratory, in order to determine their individual growth rate and tolerance to temperature and salinity. The results have evidenced that this species can tolerate temperatures between 16 and 37 degrees C and have a wide tolerance to salinity (0.968 to 17.138 g/L). The 'LC IND.50' for reference substances were: 0.734 mg/L for potassium dichromate; 0.701 g/L for potassium chloride and 9.053 g/L for sodium chloride. In relation to the latex of toxic plants, a 'LC IND.50' of 2.924 ppm and 3.308 ppm was found for Euphorbia splendens, whereas the latex of Asclepias curassavica was not toxic up to the maximum of 20.0 ppm tested. Sediments from the reservoirs Barra Bonita and Promissão (rio Tietê) were not toxic, whereas the sediment of Rasgão was extremely toxic to this molusc. It was concluded that M. tuberculata can tolerate high temperatures and salinity, what is in accordance to its wide and rapid dispersion throughout tropical waters, and that the latex of Euphorbia splendens can be used as natural moluscicid in low concentrations in integrated control programs of this invader species
103

Taxonomical study on the Vetigastropoda (Mollusca) from Canopus Bank, NE Brazil, with further remarks on their distribution along the Western Atlantic / Estudo taxonômico sobre os Vetigastropoda (Mollusca) do Banco de Canopus, Nordeste do Brasil, com comentários adicionais sobre sua distribuição ao longo do Atlântico Oeste

Cavallari, Daniel Caracanhas 03 May 2017 (has links)
A taxonomic revision of 29 species distributed in 12 vetigastropod families collected in a 60-260 m depth range at Canopus Bank, a seamount off NE Brazil, is performed based on detailed shell morphology. Their distribution and bathymetric ranges are re-examined based on specimens from Canopus and the MZSP collection. Three possibly new species are revealed and tentatively described: Arene aff. brareus can be distinguished by a large shell for the genus; sculpture consisting of spiral cords ornamented by large, semi-hollow, scale-like spines; cords separated by equally wide, deep interspaces and thin axial growth lines more visible in the interspaces; protoconch sculptured by small, subsutural axial lamellae; and color ranging from white to intense reddish, darker on spiral cords, and lighter at the base, with a yellow apex. Parviturbo aff. tuberculosus can be told apart from local congeners by its slightly taller than wide shell, which is profusely sculptured by a reticulate pattern of equally strong axial ribs and spiral cords, with angular nodules at the intersections. Calliostoma sp.1 shows no close affinities with any other local congener and is characterized by a small shells with convex whorls and a large, rounded apex; ivory white ground color with honey yellow apex and spiral cords; sculpture consisting of 4-6 narrow, nodulous spiral cords per whorl; suture marked by a suprasutural cord; inflated and mostly smooth base; narrow, shallow, and axially sculptured umbilicus. Moreover, three species have their distributions expanded northward from SE to NE Brazilian waters: Emarginula suspira Simone & Cunha, 2014, Hemimarginula hemitoma Simone & Cunha, 2014, and Homalopoma boffi Marini, 1975. Three species have their northern range limit expanded from Bahia state to Ceará state: Arene flexispina Leal & Coelho, 1985 and Turbo heisei Prado, 1999; a single NE Brazilian species is newly reported from northern waters: Haplocochlias risoneideneryae Barros, Santos, Santos, Cabral & Acioli, 2002; and another species, previously known only from Pernambuco state, is newly reported from Ceará state, also in NE Brazil: Solariella quinni Barros & Pereira, 2008. Two Caribbean species are firstly reported in the SW Atlantic: Dentistyla dentifera (Dall, 1889) and Gaza cf. fischeri (Dall, 1889); and a species previously reported from the Venezuelan shelf is firstly recorded in Brazilian waters: Parviturbo annejoffeae Rubio, Rolán & Lee, 2015. The bathymetric ranges of 11 species are expanded. High-resolution photographs of the type specimens, SEM images, and comparisons with local congeners are also provided / Uma revisão taxonômica de 29 espécies distribuídas em 12 famílias de vetigastrópodes coletadas a 60-260 m de profundidade no Banco de Canopus, uma montanha submarina do Nordeste do Brasil, é fornecida com base na morfologia detalhada da concha. Sua distribuição e intervalos batimétricos são reexaminados com base em espécimes de Canopus e da coleção do MZSP. Três espécies possivelmente novas são reveladas e tentativamente descritas: Arene aff. briareus pode ser distinguido por uma concha grande para o gênero; escultura constituída por cordas espirais ornamentadas por espinhos grandes, semi-ocos e escalares; cordas separadas por intervalos igualmente amplos e profundos e linhas de crescimento axiais finas mais visíveis nos inter-espaços; protoconcha esculturada por pequenas lamelas axiais subsuturais; e cor variando de branco a avermelhado intenso, mais escura nas costelas espirais, e mais clara na base, com um ápice amarelo. Parviturbo aff. tuberculosus pode ser distinguida dos congéneres locais pela sua concha mais alta do que larga, profusamente esculturada por um padrão reticulado de costelas axiais igualmente fortes e cordas espirais, com nódulos angulares nas intersecções. Calliostoma sp.1 não apresenta estreitas afinidades com qualquer outro congênere local e é caracterizado por uma concha pequena com voltas convexas e um grande ápice arredondado; cor branco-marfim com ápice e cordas espirais amarelo mel; escultura de 4-6 cordas espirais estreitas e nodulosas por volta; sutura marcada por um cordão suprasutural; base inflada e lisa; umbílico estreito, raso e axialmente esculturado. Três espécies têm suas distribuições expandidas para o norte, de águas do SE para o NE do Brasil: Emarginula suspira Simone & Cunha, 2014, Hemimarginula hemitoma Simone & Cunha, 2014, e Homalopoma boffi Marini, 1975. Três espécies têm seu limite de extensão norte expandido da Bahia para o Ceará: Arene flexispina Leal & Coelho, 1985 e Turbo heisei Prado, 1999; Uma única espécie brasileira do NE é relatada para águas do Norte: Haplocochlias risoneideneryae Barros, Santos, Santos, Cabral & Acioli, 2002; E uma outra espécie, anteriormente conhecida apenas do estado de Pernambuco, é reportada para o estado do Ceará: Solariella quinni Barros & Pereira, 2008. Duas espécies caribenhas são registradas pela primeira vez no Atlântico sudoeste: Dentistyla dentifera (Dall, 1889) e Gaza cf. fischeri (Dall, 1889); e uma espécie reportada previamente para a plataforma venezuelana é registrada pela primeira vez no Brasil: Parviturbo annejoffeae Rubio, Rolán & Lee, 2015. As distribuições batimétricas de 11 espécies são expandidas. Fotografias dos espécimes tipo, imagens MEV e comparações com congêneres locais são fornecidas
104

The symbiotic relationship between Symbiodinium and coral reef larvae: gene expression, fatty acid biochemistry and responses to thermal stress / A relação simbiótica entre Symbiodinium e larvas recifais: expressão gênica, produção de ácidos graxos e respostas ao estresse térmico

Mies, Miguel 24 March 2017 (has links)
Very little is known about the association between Symbiodinium dinoflagellates, which perform the majority of primary production in coral reefs, and metazoan larvae. This thesis performed three experiments on the association between Symbiodinium and Mussismilia hispida (coral), Berghia stephanieae (nudibranch) and Tridacna crocea (giant clam) larvae. The first experiment monitored the expression of a symbiosis-specific gene in Symbiodinium clade A associated with the three larval forms during a 72-h window. The second experiment quantified the production of symbiosis-related ω3 fatty acids in Symbiodinium clades A-F also associated with the three larval hosts and the third experiment verified bleaching rates at 26, 29 and 32ºC in the larvae associated with clades A-F. The main results show that i) a symbiosis-specific gene is expressed by Symbiodinium A associated with M. hispida and T. crocea larvae, but not with B. stephanieae; ii) the DHA fatty acid is produced in significantly higher amounts by clades A and C associated with M. hispida and T. crocea larvae; and iii) that M. hispida and T. crocea larvae associated with Symbiodinium A and C have significantly lower bleaching rates. These findings suggest that clades A and C establish a more robust mutualism with M. hispida and T. crocea larvae, but there seems to be no mutualism between Symbiodinium and B. stephanieae. / Muito pouco é conhecido sobre a associação entre dinoflagelados do gênero Symbiodinium e larvas de metazoários. Essa tese realizou três experimentos sobre a associação entre Symbiodinium e larvas de Mussismilia hispida (coral), Berghia stephanieae (nudibrânquio) e Tridacna crocea (vieira gigante). O primeiro experimento verificou a expressão de um gene específico para a relação simbiótica em Symbiodinium A associado com as larvas dos três hospedeiros. O segundo experimento quantificou a produção de ácidos graxos nos clados A-F de Symbiodinium também associados com as larvas dos três hospedeiros; o terceiro monitorou a perda de simbiontes nos três tipos larvais associados com os clados A-F, em temperaturas de 26, 29 e 32ºC. Os principais resultados mostram que: i) um gene específico para a simbiose é expresso por Symbiodinium A associado com M. hispida e T. crocea, mas não com B. stephanieae; ii) o ácido graxo DHA é produzido em quantidades significantemente maiores pelos clados A e C associados com M. hispida e T. crocea; e iii) M. hispida e T. crocea associadas com Symbiodinium A e C possuem taxas de perda de simbiontes significantemente menores do que os demais. Esses resultados mostram que os clados A e C estabelecem um mutualismo mais robusto com M. hispida e T. crocea, mas não há relação mutualística entre Symbiodinium e B. stephanieae.
105

Taxonomical study on the Vetigastropoda (Mollusca) from Canopus Bank, NE Brazil, with further remarks on their distribution along the Western Atlantic / Estudo taxonômico sobre os Vetigastropoda (Mollusca) do Banco de Canopus, Nordeste do Brasil, com comentários adicionais sobre sua distribuição ao longo do Atlântico Oeste

Daniel Caracanhas Cavallari 03 May 2017 (has links)
A taxonomic revision of 29 species distributed in 12 vetigastropod families collected in a 60-260 m depth range at Canopus Bank, a seamount off NE Brazil, is performed based on detailed shell morphology. Their distribution and bathymetric ranges are re-examined based on specimens from Canopus and the MZSP collection. Three possibly new species are revealed and tentatively described: Arene aff. brareus can be distinguished by a large shell for the genus; sculpture consisting of spiral cords ornamented by large, semi-hollow, scale-like spines; cords separated by equally wide, deep interspaces and thin axial growth lines more visible in the interspaces; protoconch sculptured by small, subsutural axial lamellae; and color ranging from white to intense reddish, darker on spiral cords, and lighter at the base, with a yellow apex. Parviturbo aff. tuberculosus can be told apart from local congeners by its slightly taller than wide shell, which is profusely sculptured by a reticulate pattern of equally strong axial ribs and spiral cords, with angular nodules at the intersections. Calliostoma sp.1 shows no close affinities with any other local congener and is characterized by a small shells with convex whorls and a large, rounded apex; ivory white ground color with honey yellow apex and spiral cords; sculpture consisting of 4-6 narrow, nodulous spiral cords per whorl; suture marked by a suprasutural cord; inflated and mostly smooth base; narrow, shallow, and axially sculptured umbilicus. Moreover, three species have their distributions expanded northward from SE to NE Brazilian waters: Emarginula suspira Simone & Cunha, 2014, Hemimarginula hemitoma Simone & Cunha, 2014, and Homalopoma boffi Marini, 1975. Three species have their northern range limit expanded from Bahia state to Ceará state: Arene flexispina Leal & Coelho, 1985 and Turbo heisei Prado, 1999; a single NE Brazilian species is newly reported from northern waters: Haplocochlias risoneideneryae Barros, Santos, Santos, Cabral & Acioli, 2002; and another species, previously known only from Pernambuco state, is newly reported from Ceará state, also in NE Brazil: Solariella quinni Barros & Pereira, 2008. Two Caribbean species are firstly reported in the SW Atlantic: Dentistyla dentifera (Dall, 1889) and Gaza cf. fischeri (Dall, 1889); and a species previously reported from the Venezuelan shelf is firstly recorded in Brazilian waters: Parviturbo annejoffeae Rubio, Rolán & Lee, 2015. The bathymetric ranges of 11 species are expanded. High-resolution photographs of the type specimens, SEM images, and comparisons with local congeners are also provided / Uma revisão taxonômica de 29 espécies distribuídas em 12 famílias de vetigastrópodes coletadas a 60-260 m de profundidade no Banco de Canopus, uma montanha submarina do Nordeste do Brasil, é fornecida com base na morfologia detalhada da concha. Sua distribuição e intervalos batimétricos são reexaminados com base em espécimes de Canopus e da coleção do MZSP. Três espécies possivelmente novas são reveladas e tentativamente descritas: Arene aff. briareus pode ser distinguido por uma concha grande para o gênero; escultura constituída por cordas espirais ornamentadas por espinhos grandes, semi-ocos e escalares; cordas separadas por intervalos igualmente amplos e profundos e linhas de crescimento axiais finas mais visíveis nos inter-espaços; protoconcha esculturada por pequenas lamelas axiais subsuturais; e cor variando de branco a avermelhado intenso, mais escura nas costelas espirais, e mais clara na base, com um ápice amarelo. Parviturbo aff. tuberculosus pode ser distinguida dos congéneres locais pela sua concha mais alta do que larga, profusamente esculturada por um padrão reticulado de costelas axiais igualmente fortes e cordas espirais, com nódulos angulares nas intersecções. Calliostoma sp.1 não apresenta estreitas afinidades com qualquer outro congênere local e é caracterizado por uma concha pequena com voltas convexas e um grande ápice arredondado; cor branco-marfim com ápice e cordas espirais amarelo mel; escultura de 4-6 cordas espirais estreitas e nodulosas por volta; sutura marcada por um cordão suprasutural; base inflada e lisa; umbílico estreito, raso e axialmente esculturado. Três espécies têm suas distribuições expandidas para o norte, de águas do SE para o NE do Brasil: Emarginula suspira Simone & Cunha, 2014, Hemimarginula hemitoma Simone & Cunha, 2014, e Homalopoma boffi Marini, 1975. Três espécies têm seu limite de extensão norte expandido da Bahia para o Ceará: Arene flexispina Leal & Coelho, 1985 e Turbo heisei Prado, 1999; Uma única espécie brasileira do NE é relatada para águas do Norte: Haplocochlias risoneideneryae Barros, Santos, Santos, Cabral & Acioli, 2002; E uma outra espécie, anteriormente conhecida apenas do estado de Pernambuco, é reportada para o estado do Ceará: Solariella quinni Barros & Pereira, 2008. Duas espécies caribenhas são registradas pela primeira vez no Atlântico sudoeste: Dentistyla dentifera (Dall, 1889) e Gaza cf. fischeri (Dall, 1889); e uma espécie reportada previamente para a plataforma venezuelana é registrada pela primeira vez no Brasil: Parviturbo annejoffeae Rubio, Rolán & Lee, 2015. As distribuições batimétricas de 11 espécies são expandidas. Fotografias dos espécimes tipo, imagens MEV e comparações com congêneres locais são fornecidas
106

Estudos ecológicos e ecotoxicológicos de Melanoides tuberculata Müller, 1774 (Gastropoda, Thiaridae), espécie exótica para a região neotropical / Ecological and ecotoxicological studies of Melanoides tuberculata Müller 1774 (Gastropoda, Thiaridae), exotic species for neotropical region

Denise Tieme Okumura 07 June 2006 (has links)
As introduções de espécies exóticas têm significantemente modificado a estrutura das comunidades levando à extinção muitas espécies nativas. A crescente invasão, nas águas doces brasileiras pelo gastropoda Melanoides tuberculata, de origem africano-asiática, é preocupante. No presente estudo foram analisados diversos aspectos referentes ao ciclo de vida, à tolerância a variáveis abióticas e à sensibilidade a substâncias tóxicas de referência e aos sedimentos contaminados de três reservatórios do estado de São Paulo (Rasgão, Barra Bonita e Promissão). Testou-se a eficácia do látex de Euphorbia splendens e de Asclepias curassavica como moluscicida. Os moluscos foram coletados em tanques de piscicultura, em Pirassununga, SP, e cultivados em laboratório, determinando-se a taxa de crescimento e a tolerância à temperatura e à salinidade. Os resultados evidenciaram que esta espécie tolera temperaturas entre 16 e 37 'graus' C e tem ampla tolerância à salinidade (0,968 a 17,138 g/L). As 'CL IND.50' para substâncias de referência foram: 0,734 mg/L para o dicromato de potássio; 0,701 g/L para o cloreto de potássio e de 9,053 g/L para o cloreto de sódio. Em relação ao látex de plantas tóxicas, obtiveram-se 'CL IND.50' entre 2,924 ppm e 3,308 ppm para Euphorbia splendens, enquanto o látex de Asclepias curassavica não foi tóxico até o limite máximo de 20,0 ppm. Os sedimentos dos reservatórios de Barra Bonita e Promissão (rio Tietê) não foram tóxicos, enquanto o sedimento de Rasgão foi extremamente tóxico a este molusco. Concluiu-se que a alta tolerância de M. tuberculata a elevadas temperaturas e à salinidade corroboram sua ampla e rápida dispersão pelas águas doces tropicais e que o látex de Euphorbia splendens pode ser utilizado como moluscicida natural em baixas concentrações em programas integrados de controle da invasão desta espécie invasora / The introduction of exotic species have marcantly altered the structure of communities, leading to the extinction of many native species. The progressive invasion of brazilian freshwaters by the gastropoda Melanoides tuberculata, with afro-asian origin, is quite worrying at the moment. In the present study some aspects of the life cycle of M. tuberculata, its tolerance to abiotic variables and its sensibility to both toxic reference substances and contaminated sediments from São Paulo state reservoirs (Barra Bonita, Promissão and Rasgão) were evaluated. It was also tested the efficiency of the latex of Euphorbia splendens and Asclepias curassavica as natural moluscicids. Moluscs were collected from fish ponds in Pirassununga, SP, and cultured in the laboratory, in order to determine their individual growth rate and tolerance to temperature and salinity. The results have evidenced that this species can tolerate temperatures between 16 and 37 degrees C and have a wide tolerance to salinity (0.968 to 17.138 g/L). The 'LC IND.50' for reference substances were: 0.734 mg/L for potassium dichromate; 0.701 g/L for potassium chloride and 9.053 g/L for sodium chloride. In relation to the latex of toxic plants, a 'LC IND.50' of 2.924 ppm and 3.308 ppm was found for Euphorbia splendens, whereas the latex of Asclepias curassavica was not toxic up to the maximum of 20.0 ppm tested. Sediments from the reservoirs Barra Bonita and Promissão (rio Tietê) were not toxic, whereas the sediment of Rasgão was extremely toxic to this molusc. It was concluded that M. tuberculata can tolerate high temperatures and salinity, what is in accordance to its wide and rapid dispersion throughout tropical waters, and that the latex of Euphorbia splendens can be used as natural moluscicid in low concentrations in integrated control programs of this invader species
107

Peptidomic analysis and characterization of the venom from Conus purpurascens

Unknown Date (has links)
The venom of cone snails is a potent cocktail of peptides, proteins, and other small molecules. Several of the peptides (conopeptides and conotoxins) target ion channels and receptors and have proven useful as biochemical probes or pharmaceutical leads. In this study, the venom of a fish-hunting cone snail, Conus purpurascens was analyzed for intraspecific variability; α-conotoxins from the venom were isolated by high performance liquid chromatography, identified by mass spectrometry and nuclear magnetic resonance, and tested in a electrophysiological assay in Drosophila melanogaster; the effects of diet change on venom composition was investigated. It has been determined that each specimen of C. purpurascens expresses a distinct venom, resulting in the expression of more than 5,000 unique conopeptides across the species. α- conotoxin PIA was shown to inhibit the Dα7 nicotinic acetylcholine receptor. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2015. / FAU Electronic Theses and Dissertations Collection
108

Functional Morphology of Gastropods and Bivalves

Sälgeback, Jenny January 2006 (has links)
<p>Functional morphology analyzes the relationships between form and function in organisms. However, a comprehensive analysis of any organic structure requires an integrated approach to morphology. For this purpose constructional morphology was developed, where function, phylogeny and construction together explain form. This thesis investigates functional and constructional aspects of gastropods and bivalves; two groups of molluscs which are among the most common shell-bearing invertebrates. Their shell protects the soft parts and different morphologic specializations enhance this function. Morphology and mode of life are often closely coupled. </p><p>Comparison of the distantly related cardiid bivalves <i>Cardium</i> <i>costatum</i> and <i>Budmania</i> spp. reveals similar shell modifications. Both have prominent keels functional in anchoring the shell within the sediment. The straight keels in <i>C. costatum</i> indicate an additional strengthening function, whereas the keels in <i>Budmania</i> spp. often are deformed and do not. Other shell modifications include secondary resorption of shell material and hollow keel interiors, reducing shell weight. These similarities are explained by parallel evolution and a common cardiid <i>Bauplan</i>.</p><p>Morphological shell characters in cerithiform gastropods have evolved independently in different taxonomic groups and multiple times within the same group. Shell characters are adaptive within five functional areas: defence from shell-peeling predators, burrowing and infaunal life, clamping, stabilization, and righting of the shell. Most characters are made feasible by determinate growth and a count-down programme.</p><p>In most environments predators that crush, peel and bore shells are present. As bivalves and gastropods grow by marginal accretion, and are able to replace lost shell material, traces of unsuccessful predation are preserved as scars. Experiments on the snail <i>Nucella lamellosa</i> show that repaired shells are just as strong as shells without damage. However, new scars follow old scar lines in 43% of tested specimens. This might be due to a higher organic content in this area.</p>
109

Functional Morphology of Gastropods and Bivalves

Sälgeback, Jenny January 2006 (has links)
Functional morphology analyzes the relationships between form and function in organisms. However, a comprehensive analysis of any organic structure requires an integrated approach to morphology. For this purpose constructional morphology was developed, where function, phylogeny and construction together explain form. This thesis investigates functional and constructional aspects of gastropods and bivalves; two groups of molluscs which are among the most common shell-bearing invertebrates. Their shell protects the soft parts and different morphologic specializations enhance this function. Morphology and mode of life are often closely coupled. Comparison of the distantly related cardiid bivalves Cardium costatum and Budmania spp. reveals similar shell modifications. Both have prominent keels functional in anchoring the shell within the sediment. The straight keels in C. costatum indicate an additional strengthening function, whereas the keels in Budmania spp. often are deformed and do not. Other shell modifications include secondary resorption of shell material and hollow keel interiors, reducing shell weight. These similarities are explained by parallel evolution and a common cardiid Bauplan. Morphological shell characters in cerithiform gastropods have evolved independently in different taxonomic groups and multiple times within the same group. Shell characters are adaptive within five functional areas: defence from shell-peeling predators, burrowing and infaunal life, clamping, stabilization, and righting of the shell. Most characters are made feasible by determinate growth and a count-down programme. In most environments predators that crush, peel and bore shells are present. As bivalves and gastropods grow by marginal accretion, and are able to replace lost shell material, traces of unsuccessful predation are preserved as scars. Experiments on the snail Nucella lamellosa show that repaired shells are just as strong as shells without damage. However, new scars follow old scar lines in 43% of tested specimens. This might be due to a higher organic content in this area.
110

ENZYME VARIATION IN ASHMUNELLA LEVETTEI (BLAND) (GASTROPODA: POLYGYRIDAE)

Fairbanks, Harold Lee January 1979 (has links)
No description available.

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