A seleção sexual atua de forma significativa na evolução de características reprodutivas. Os machos apresentam diversas estratégias para garantir a fertilização da fêmea, a qual, por sua vez, possui papel crucial em processos pré- e pós-copulatórios. Nesse contexto, cefalópodes apresentam aspectos reprodutivos peculiares, apresentando transferência de espermatozoides via espermatóforos e, em alguns casos, armazenamento desses gametas em órgãos especializados (i.e., receptáculos seminais). Entretanto, pouco se sabe sobre a morfologia, funcionamento e mecanismos de captação, armazenamento e liberação dos espermatozoides pelos receptáculos seminais. Neste contexto, a presente dissertação teve como objetivo investigar a estrutura e função do receptáculo seminal de Doryteuthis plei, espécie de lula adotada como modelo, como base para compreensão de mecanismos pós-copulatórios de seleção sexual em cefalópodes. Para atingir esse objetivo, a morfologia do receptáculo seminal foi analisada com base em microscopia integrativa (microscopia óptica com emprego de técnicas histoquímicas, microscopia eletrônica de varredura e de transmissão, microscopia confocal e microCT), visando a uma caracterização detalhada da estrutura do órgão. Além disso, a morfologia e histologia/histoquímica do receptáculo seminal foi analisada em três situações experimentais distintas: (1) antes de cópula recente, (2) após cópula recente (e antes da desova) e (3) após a desova, para investigar alterações morfológicas no órgão e no volume de espermatozoides armazenados, como base para compreensão dos mecanismos de captação, armazenamento e liberação de gametas masculinos pela fêmea. Os resultados revelaram enorme complexidade do receptáculo seminal com relação à diversidade de células secretoras e de fibras musculares associadas. Constatou-se que há alteração das células secretoras após a cópula recente e após a desova, com liberação do conteúdo de parte dessas células. Com base nos resultados obtidos, discute-se o papel dessas secreções na captação, armazenamento e liberação de espermatozoides. Além disso, a estrutura dos sistemas nervoso e muscular associados ao receptáculo seminal sugere que a fêmea tenha controle sobre deformações precisas do órgão relacionadas à captação e liberação de espermatozoides. Entretanto, outros mecanismos seriam igualmente possíveis, como atração química, natação ativa dos espermatozoides e ação ciliar do órgão. Alguns receptáculos seminais foram encontrados com espermatângios (i.e., espermatóforos evertidos) bloqueando total ou parcialmente sua abertura. Devido à frequência, posição e morfologia dos espermâtangios dentro do receptáculo seminal, propõe-se a hipótese de que essas estruturas poderiam atuar também como plugues copulatórios. Esses plugues seriam mais eficientes nas primeiras 24 horas, sua eficiência sendo gradualmente reduzida com o tempo após a cópula, devido ao esvaziamento do conteúdo espermático e consequente redução de sua turgidez. Embora plugues copulatórios sejam conhecidos em inúmeras espécies de animais, este é o primeiro registro para cefalópodes, sendo, portanto, marco importante nos estudos de seleção sexual para o grupo. Cefalópodes são considerados modelos interessantes para o estudo de seleção sexual e os resultados desta dissertação contribuem para compreensão dos complexos mecanismos pós-copulatórios em lulas, como escolha críptica da fêmea e competição espermática / Sexual selection exerts a significant pressure on the evolution of reproductive attributes. Males show a diverse array of strategies to gain advantage in mating and fertilization success, but females also play a crucial role in pre- and post-copulatory sexual selection processes. Within this context, cephalopod mollusks show peculiar reproductive strategies, including sperm transfer via spermatophores, and the presence of female sperm-storage organs (seminal receptacles). However, the knowledge of the functioning of the cephalopod seminal receptacles is scarce, the mechanisms involved with sperm uptake, storage and release being unknown. To shed light on post-copulatory mechanisms in cephalopods, the present dissertation aimed at investigating the structure and function of the seminal receptacle of the squid Doryteuthis plei. To achieve this goal, the morphology of the seminal receptacle was thoroughly analyzed applying integrative microscopy (light microscopy including histochemical techniques, scanning & transmission electron microscopy, confocal microscpy and microCT). Moreover, to investigate morphological and sperm volume changes associated with possible mechanisms of sperm uptake, storage and release by the organ, the morphology and histology/histochemistry of the seminal receptacle was also analyzed under three distinct experimental manipulations: (1) before recent mating (2) after recent mating (and before egg release) and (3) after egg release. The results show a complex and striking diversity of secretory cells and associated muscle fibers in the seminal receptacle. There were changes in the composition and predominance of secretory cells between major reproductive events, suggesting a secretory activity associated with mating and spawning. The possible roles of these secretions in sperm uptake, storage and release are discussed in light of our data. Moreover, the structure of the nervous and muscular systems associated with the receptacle suggests that females have control over precise deformations of the organ, possibly related to sperm uptake and release. However, other mechanisms would be possible, such as chemical attraction, sperm active swimming, and ciliary action. Seminal receptacles were sometimes found with spermatangia (i.e., everted spermatophores) blocking totally or partially their openings. Given their frequency, position, and morphology, we hypothesize spermatangia might function as copulatory plugs that physically obstruct the female storage organ. Plug efficiency should be high within the first 24 hours after mating, gradually decreasing its efficiency with time, when spermatangia lose their turgidity by releasing part of their sperm content. Although copulatory plugs have been reported for numerous taxa, this is the first record for cephalopods, and as such this finding has an impact for sexual selection studies based on these mollusks. Cephalopods are considered interesting models to investigate sexual selection, and this study has cast some light on the understanding of complex post-copulatory mechanisms in squids, such as cryptic female choice and sperm competition

Taxonomic position of the cephalopod Bactroceras sandbergeri (Barr., 1867) from the Ordovician of the Prague Basin was subjected to wide discussions and disputes in the past. The species was first classified within the genus Bactrites. Later, a separate, monotypic genus Eobactrites was defined. At present, the species is assigned to the genus Bactroceras. It belongs to the family Baltoceratidae, the genera of which are supposed to represent the oldest orthoceridans. The order Orthocerida is one of the most successful and most diversified cephalopod groups of the Paleozoic Era. In this thesis, a revision of Bactroceras sandbergeri has been made after a detailed study of about one hundred specimens. Attention was paid to those features, that are missing in the original species descriptions or that were neglected in the past. Special attention was paid mainly to muscle scars, structure of the siphuncle and morphology of the embryonic shell. The embryonic shell was originally described as Tretoceras parvulum Barrande, 1868. In addition, Orthoceras naufragum Barrande, 1870 was synonymized with the studied species and the species Orthoceras interpolatum Barrande, 1870 was assigned to the genus Bactroceras. Key words: Cephalopoda, Ordovician, Czech Republic, Barrandian area

O processo de seleção sexual influencia de forma intensa o sucesso reprodutivo de cada indivíduo. Desde sua formulação teórica durante o século XIX, evidências cumulativas a respeito da poliandria em fêmeas permitiram a ampliação de seu conceito inicial, uma vez constatada que a disputa pela paternidade da prole não se limitava à competição pelo acesso à fêmea, mas poderia também prolongar-se mesmo após a cópula. Durante a década de 1970, essa disputa pós-copulatória entre machos foi formalizada sob o conceito de competição espermática, a qual visa a maximizar o sucesso do esperma de um macho sobre um rival na fertilização dos ovos. Evidências para um número crescente de táxons demonstram que a intensa competição pré e pós-copulatória entre machos é também uma das fontes responsáveis pela evolução e manutenção de táticas alternativas de reprodução dentro de uma mesma espécie, nas quais machos com menor sucesso na monopolização de fêmeas e combate com intraespecíficos adotam comportamentos furtivos para acesso ao sexo oposto, como forma de assegurar algum sucesso reprodutivo. Em muitas espécies, a adoção de táticas alternativas de reprodução são relacionadas não somente às diferenças comportamentais entre os machos, mas também à diversidade fenotípica dentro do mesmo sexo, caracterizada por descontinuidades morfológicas, fisiológicas e de ciclo de vida, conhecida pelo termo ‘dimorfismo intrassexual’. Em lulas da família Loliginidae, a existência de morfos alternativos, denominados machos consort e sneaker, já foi constatada para diversas espécies e é associada a diferenças comportamentais entre eles, principalmente relacionadas à posição de cópula e sítio de deposição de espermatóforos no interior da fêmea. No entanto, a associação entre táticas alternativas de reprodução e dimorfismo intrassexual em machos é praticamente desconhecida, com exceção à espécie Heterololigo bleekeri, para a qual esse dimorfismo tem sido estudado extensivamente ao longo da última década. Nesse contexto, a presente Dissertação de Mestrado teve como principal objetivo investigar a existência de dimorfismo intrassexual masculino em Doryteuthis plei (Blainville, 1823), uma espécie de importância comercial para as regiões Sul e Sudeste do Brasil e para a qual, apesar de evidências indiretas sugerirem sua presença, tal dimorfismo nunca havia sido averiguado. Por meio de análises morfológicas e modelos estatísticos, o primeiro capítulo descreve a existência desse dimorfismo na espécie, o qual foi reconhecido a partir da constatação da presença de duas classes de tamanho de machos sexualmente maduros, caracterizadas pela produção de espermatóforos e espermatângios com morfologias descontínuas. Além disso, espermatângios amostrados de machos das duas classes de tamanho mostraram-se congruentes àquelas implantados nos dois sítios distintos da fêmea, resultado que permitiu associar o dimorfismo intrassexual à adoção das táticas de sneaker e consort na espécie. A partir dessa constatação, o primeiro capítulo explorou ainda o investimento gonadal exibido por machos dimórficos. Os resultados mostraram que machos sneakers apresentavam maiores investimentos relativos em gônadas do que machos consorts, um resultado que se enquadra nos modelos teóricos de “sneaks and guarders” de competição espermática. No entanto, enquanto as premissas teóricas propõem também que machos sneakers devem apresentar maiores investimentos por fêmea, constatamos que, na espécie de estudo, machos sneakers produzem espermatóforos com menor proporção de massa espermática do que machos consorts. Esses resultados, somados a observações comportamentais realizadas ao longo desse trabalho, sugerem que a estratégia adotada por machos sneakers deve estar relacionada ao fracionamento de seu investimento em produtos ejaculatórios, de forma que investimentos menores por fêmea permitiriam a realização de maior número de cópulas. Dando continuidade à caracterização do dimorfismo intrassexual na espécie, análises comparativas entre machos dimórficos com relação a estruturas do sistema reprodutor, tema do segundo capítulo, demonstraram que as diferenças quanto à morfologia funcional de espermatóforos intactos estavam associadas às divergências encontradas quanto à reação espermatofórica, liberação de espermatozoides e morfologia de espermatângios entre machos sneakers e consorts. Além disso, sob o contexto da competição espermática, o segundo capítulo discute como o padrão de reprodução de lulas da família Loliginidae, e.g., a existência de dois sítios de fertilização e diferenças nos intervalos entre cópulas e desovas, resultaria em pressões seletivas divergentes sobre os produtos ejaculatórios de machos dimórficos e influenciaria a evolução e manutenção do dimorfismo intrassexual na espécie. Por fim, o terceiro capítulo aborda a descoberta de machos com espermatóforos e espermatângios com morfologias intermediárias entre os fenótipos de sneakers e consorts, além da questão da diferença de idade entre machos dimórficos. Combinados, os resultados desse capítulo permitiram a proposição de uma hipótese ontogenética sobre a expressão de fenótipos alternativos na espécie, uma questão extremamente inovadora para cefalópodes. Apesar de tratar-se de um campo ainda completamente inexplorado para o grupo, espera-se que esses resultados contribuam para a compreensão dos fatores responsáveis pela expressão sequencial de fenótipos alternativos e pela determinação do dimorfismo intrassexual em lulas / Sexual selection comprises a powerful force that intensively influences the reproductive success of each individual. Since its theoretical formulation in the nineteenth century, cumulative evidence regarding the existence of polyandry in females has expanded its initial concept, once it became clear that offspring paternity disputes were not limited to the competition for female access, but that they could in fact be prolonged even after copulation. In the 1970s, this male post-copulatory dispute was formalized under the concept of sperm competition, which aims at maximizing the success of one male’s sperm over its competitors in the fertilization of females’ eggs. Evidence gathered from a growing number of taxa has shown that intense pre and post-copulatory competition between males is also one of the responsible sources for the evolution and maintenance of alternative reproductive tactics within a species, in which males that are less successful in mate guarding and fighting contests with conspecifics adopt sneaking and opportunistic behaviors as a way to ensure some mating success. In many species, alternative mating tactics are not restricted to behavioral differences between males, being also related to a phenotypic diversity, with discontinuous morphological and physiological traits and distinct life histories between conspecifics, a phenomenon known as intrasexual dimorphism. In loliginid squids, the existence of alternative morphs (sneaker and consort males) has already been reported for several species, and it is has been correlated to behavioral differences, specially related to mating position and spermatophore deposition sites within the female\'s body. However, the association between alternative mating tactics and male intrasexual dimorphism is virtually unexplored, except for the species Heterololigo bleekeri, in which such dimorphism has been extensively studied over the last decade. In this context, the present Master’s Dissertation aimed to investigate the existence of male intrasexual dimorphism in Doryteuthis plei (Blainville, 1823), a squid of commercial importance in southern and southeastern Brazil, and for which such dimorphism has never been investigated, although indirect evidence suggests its existence. Using morphological analyses and statistical models, the first chapter describes the presence of such dimorphism in the species, which was detected based on the identification of two body size classes of sexually mature males, characterized by spermatophores and spermatangia displaying discontinuous morphologies between each other. Moreover, spermatangia sampled from both body size classes were congruent with those implanted on distinct female sites, a result that allowed the association between intrassexual dimorphism and adoption of sneaker and consort mating tactics in the species. Additionally, the first chapter also investigated the gonadal investment from dimorphic males, showing that sneakers exhibited higher investments in gonads than consorts, a result that fits into the theoretical ‘sneaks and guards’ models of sperm competition. However, while theoretical assumptions propose that sneakers should also present larger investments per female, we show that D. plei sneaker males produce spermatophores with lower concentrations of sperm mass than consorts. Combining these results with behavioral observations obtained throughout this study, we suggest that the sneaker strategy might be related to partitioning their ejaculate expenditure into extra mating opportunities, thus investing less per female but more in number of copulations. A further characterization of intrasexual dimorphism in this species was the main subject of the second chapter. Through comparative analyses of reproductive structures from dimorphic males, the results revealed that differences in the structural morphology of intact spermatophores were associated to differences regarding the spermatophoric reaction, spermatozoa release and spermatangia morphology between sneakers and consorts. Furthermore, under the context of sperm competition, the second chapter also provided a discussion on how the reproductive pattern of loliginid squids, e.g., the existence of two sites for fertilization of eggs and differences in the interval between mating and egg-laying, might result in divergent selective pressures on ejaculates from dimorphic males, influencing the evolution and maintenance of intrasexual dimorphism in this species. Finally, the third chapter describes the discovery of males that produced spermatophores and spermatangia displaying intermediate morphologies between both sneaker and consort phenotypes, and age differences reported for dimorphic males in the species. Combined, these results allowed the formulation of an ontogenetic hypothesis regarding alternative phenotype expression, which is extremely innovative for cephalopods. Although this hypothesis comprises a completely unexplored field for this group, it is highly expected that these results might contribute to the further understanding of possible factors that may be responsible for the sequential expression of alternative phenotypes, and ultimately for the determination of intrasexual dimorphism in squids

O processo de seleção sexual influencia de forma intensa o sucesso reprodutivo de cada indivíduo. Desde sua formulação teórica durante o século XIX, evidências cumulativas a respeito da poliandria em fêmeas permitiram a ampliação de seu conceito inicial, uma vez constatada que a disputa pela paternidade da prole não se limitava à competição pelo acesso à fêmea, mas poderia também prolongar-se mesmo após a cópula. Durante a década de 1970, essa disputa pós-copulatória entre machos foi formalizada sob o conceito de competição espermática, a qual visa a maximizar o sucesso do esperma de um macho sobre um rival na fertilização dos ovos. Evidências para um número crescente de táxons demonstram que a intensa competição pré e pós-copulatória entre machos é também uma das fontes responsáveis pela evolução e manutenção de táticas alternativas de reprodução dentro de uma mesma espécie, nas quais machos com menor sucesso na monopolização de fêmeas e combate com intraespecíficos adotam comportamentos furtivos para acesso ao sexo oposto, como forma de assegurar algum sucesso reprodutivo. Em muitas espécies, a adoção de táticas alternativas de reprodução são relacionadas não somente às diferenças comportamentais entre os machos, mas também à diversidade fenotípica dentro do mesmo sexo, caracterizada por descontinuidades morfológicas, fisiológicas e de ciclo de vida, conhecida pelo termo ‘dimorfismo intrassexual’. Em lulas da família Loliginidae, a existência de morfos alternativos, denominados machos consort e sneaker, já foi constatada para diversas espécies e é associada a diferenças comportamentais entre eles, principalmente relacionadas à posição de cópula e sítio de deposição de espermatóforos no interior da fêmea. No entanto, a associação entre táticas alternativas de reprodução e dimorfismo intrassexual em machos é praticamente desconhecida, com exceção à espécie Heterololigo bleekeri, para a qual esse dimorfismo tem sido estudado extensivamente ao longo da última década. Nesse contexto, a presente Dissertação de Mestrado teve como principal objetivo investigar a existência de dimorfismo intrassexual masculino em Doryteuthis plei (Blainville, 1823), uma espécie de importância comercial para as regiões Sul e Sudeste do Brasil e para a qual, apesar de evidências indiretas sugerirem sua presença, tal dimorfismo nunca havia sido averiguado. Por meio de análises morfológicas e modelos estatísticos, o primeiro capítulo descreve a existência desse dimorfismo na espécie, o qual foi reconhecido a partir da constatação da presença de duas classes de tamanho de machos sexualmente maduros, caracterizadas pela produção de espermatóforos e espermatângios com morfologias descontínuas. Além disso, espermatângios amostrados de machos das duas classes de tamanho mostraram-se congruentes àquelas implantados nos dois sítios distintos da fêmea, resultado que permitiu associar o dimorfismo intrassexual à adoção das táticas de sneaker e consort na espécie. A partir dessa constatação, o primeiro capítulo explorou ainda o investimento gonadal exibido por machos dimórficos. Os resultados mostraram que machos sneakers apresentavam maiores investimentos relativos em gônadas do que machos consorts, um resultado que se enquadra nos modelos teóricos de “sneaks and guarders” de competição espermática. No entanto, enquanto as premissas teóricas propõem também que machos sneakers devem apresentar maiores investimentos por fêmea, constatamos que, na espécie de estudo, machos sneakers produzem espermatóforos com menor proporção de massa espermática do que machos consorts. Esses resultados, somados a observações comportamentais realizadas ao longo desse trabalho, sugerem que a estratégia adotada por machos sneakers deve estar relacionada ao fracionamento de seu investimento em produtos ejaculatórios, de forma que investimentos menores por fêmea permitiriam a realização de maior número de cópulas. Dando continuidade à caracterização do dimorfismo intrassexual na espécie, análises comparativas entre machos dimórficos com relação a estruturas do sistema reprodutor, tema do segundo capítulo, demonstraram que as diferenças quanto à morfologia funcional de espermatóforos intactos estavam associadas às divergências encontradas quanto à reação espermatofórica, liberação de espermatozoides e morfologia de espermatângios entre machos sneakers e consorts. Além disso, sob o contexto da competição espermática, o segundo capítulo discute como o padrão de reprodução de lulas da família Loliginidae, e.g., a existência de dois sítios de fertilização e diferenças nos intervalos entre cópulas e desovas, resultaria em pressões seletivas divergentes sobre os produtos ejaculatórios de machos dimórficos e influenciaria a evolução e manutenção do dimorfismo intrassexual na espécie. Por fim, o terceiro capítulo aborda a descoberta de machos com espermatóforos e espermatângios com morfologias intermediárias entre os fenótipos de sneakers e consorts, além da questão da diferença de idade entre machos dimórficos. Combinados, os resultados desse capítulo permitiram a proposição de uma hipótese ontogenética sobre a expressão de fenótipos alternativos na espécie, uma questão extremamente inovadora para cefalópodes. Apesar de tratar-se de um campo ainda completamente inexplorado para o grupo, espera-se que esses resultados contribuam para a compreensão dos fatores responsáveis pela expressão sequencial de fenótipos alternativos e pela determinação do dimorfismo intrassexual em lulas / Sexual selection comprises a powerful force that intensively influences the reproductive success of each individual. Since its theoretical formulation in the nineteenth century, cumulative evidence regarding the existence of polyandry in females has expanded its initial concept, once it became clear that offspring paternity disputes were not limited to the competition for female access, but that they could in fact be prolonged even after copulation. In the 1970s, this male post-copulatory dispute was formalized under the concept of sperm competition, which aims at maximizing the success of one male’s sperm over its competitors in the fertilization of females’ eggs. Evidence gathered from a growing number of taxa has shown that intense pre and post-copulatory competition between males is also one of the responsible sources for the evolution and maintenance of alternative reproductive tactics within a species, in which males that are less successful in mate guarding and fighting contests with conspecifics adopt sneaking and opportunistic behaviors as a way to ensure some mating success. In many species, alternative mating tactics are not restricted to behavioral differences between males, being also related to a phenotypic diversity, with discontinuous morphological and physiological traits and distinct life histories between conspecifics, a phenomenon known as intrasexual dimorphism. In loliginid squids, the existence of alternative morphs (sneaker and consort males) has already been reported for several species, and it is has been correlated to behavioral differences, specially related to mating position and spermatophore deposition sites within the female\'s body. However, the association between alternative mating tactics and male intrasexual dimorphism is virtually unexplored, except for the species Heterololigo bleekeri, in which such dimorphism has been extensively studied over the last decade. In this context, the present Master’s Dissertation aimed to investigate the existence of male intrasexual dimorphism in Doryteuthis plei (Blainville, 1823), a squid of commercial importance in southern and southeastern Brazil, and for which such dimorphism has never been investigated, although indirect evidence suggests its existence. Using morphological analyses and statistical models, the first chapter describes the presence of such dimorphism in the species, which was detected based on the identification of two body size classes of sexually mature males, characterized by spermatophores and spermatangia displaying discontinuous morphologies between each other. Moreover, spermatangia sampled from both body size classes were congruent with those implanted on distinct female sites, a result that allowed the association between intrassexual dimorphism and adoption of sneaker and consort mating tactics in the species. Additionally, the first chapter also investigated the gonadal investment from dimorphic males, showing that sneakers exhibited higher investments in gonads than consorts, a result that fits into the theoretical ‘sneaks and guards’ models of sperm competition. However, while theoretical assumptions propose that sneakers should also present larger investments per female, we show that D. plei sneaker males produce spermatophores with lower concentrations of sperm mass than consorts. Combining these results with behavioral observations obtained throughout this study, we suggest that the sneaker strategy might be related to partitioning their ejaculate expenditure into extra mating opportunities, thus investing less per female but more in number of copulations. A further characterization of intrasexual dimorphism in this species was the main subject of the second chapter. Through comparative analyses of reproductive structures from dimorphic males, the results revealed that differences in the structural morphology of intact spermatophores were associated to differences regarding the spermatophoric reaction, spermatozoa release and spermatangia morphology between sneakers and consorts. Furthermore, under the context of sperm competition, the second chapter also provided a discussion on how the reproductive pattern of loliginid squids, e.g., the existence of two sites for fertilization of eggs and differences in the interval between mating and egg-laying, might result in divergent selective pressures on ejaculates from dimorphic males, influencing the evolution and maintenance of intrasexual dimorphism in this species. Finally, the third chapter describes the discovery of males that produced spermatophores and spermatangia displaying intermediate morphologies between both sneaker and consort phenotypes, and age differences reported for dimorphic males in the species. Combined, these results allowed the formulation of an ontogenetic hypothesis regarding alternative phenotype expression, which is extremely innovative for cephalopods. Although this hypothesis comprises a completely unexplored field for this group, it is highly expected that these results might contribute to the further understanding of possible factors that may be responsible for the sequential expression of alternative phenotypes, and ultimately for the determination of intrasexual dimorphism in squids

The modern cephalopod molluscs, particularly the octopods, are highly developed macrophageous predators which have a pronounced ability to learn. Striking resemblances are found between these animals and the vertebrates, particularly the fish. The study of cephalopods therefore provides an opportunity to examine systems which are composed of structural units common to molluscs but which may be similar in function and performance to those of vertebrates. This investigation concerns the alimentary canal and its innervation in the lesser octopus Eledone cirrhosa. Detailed anatomical investigation shows the alimentary canal of E. cirrhosa to be very similar to that of the better known Octopus vulgaris. Current concepts of the functions of the alimentary organs are discussed utilizing data from both E. cirrhosa and O. vulgaris. Silver staining reveals a basic pattern of innervation in the alimentary organs. Large nerve trunks running in the external collagenous layer give rise to a nerve plexus within the circular muscle. The longitudinal muscle plexus arises from branches of the circular muscle plexus or direct from the nerves of the external layer, Nerves of both plexuses contact muscle fibres in an 'en passant' manner. Fibres run out from the longitudinal muscle to the subepithelium, where they are observed associated with muscle fibres and beneath the epithelial basal lamina. Good evidence for fibres crossing into the epithelium was observed only in the cuticularized regions of the digestive tract. The digestive gland ducts differ from this pattern in the very large numbers of major nerves seen in their external and muscular regions. Outwith the alimentary ganglia nerve cells are only regularly observed within the major intestinal nerves. Receptor like cells were also repeatedly observed only in the posterior intestine. These results axe compared with data from O. vulgaris and the physiological evidence for the presence of receptors. The blood vessels of the alimentary canal are innervated at all levels. The distribution of other densely staining cells is reported. Evidence for the presence of particular neurotransmitters within the alimentary canal and alimentary nerve centres is reviewed. Fluorescence histochemistry shows that at least two types of nerves are present in the alimentary wall. The majority axe aminergic (including those associated with blood vessels and some sphincters), as the pattern of fluorescent nerves is predominantly that shown by silver studies. However, fluorescent nerves decrease and then disappear anteriorly from the crop/oesophageal sphincter and posteriorly from the mid-intestine. The stomach has fluorescent nerves, other than those associated with blood vessels. Fluorescent fibres enter the gut via the sympathetic and possibly the digestive gland duct nerves. Non-fluorescent fibres enter via the atrio-rectal nerves and from the gastric ganglion. The fluorescence is ascribed to catecholamines as no evidence of 5HT was obtained, Specific fluorescence was also observed in some cells of the subepithelium and the external region. These results are discussed with reference to available physiological data. The anterior intestine was the representative region chosen for fine structural studies. These show the alimentary muscles to be the same basic type (cross or pseudo-striated) as that found in cephalopod somatic or heart muscle. Three types of myomuscular and neuromuscular junctions axe described. The presence of mineralized concretions (spherites) in the external layer of the intestine, together with the complex relations of its epithelial cells and heavy vascularization suggest a secondary function of mineral and/or water balance for this organ. These results are discussed. Finally, a pathological condition affecting the octopuses during this study is described.

This dissertation thesis is a summary of five studies published in peer- reviewed, impacted scientific journals. All of the publications are taxonomic revisions of previously unknown or little known collections of fossil cephalopods from the Early Paleozoic strata of Bohemia, Estonia and Sweden. Paleogeogra- phical and stratigraphical distributions of the respective taxa were summarized, refined and compared with contemporary fossil assemblages known from other regions. Implications on the paleoecology of the cephalopods and original envi- ronmental conditions were made. The text of the thesis is divided into three main parts. In the first part, the morphology of cephalopods is explained, stressing out the most important diagnostic characters used for their descriptions. The current systematics of the Cephalopoda is overviewed and the main cephalopod groups during the Ordovician are briefly introduced. The second part of the thesis describes the geological development and settings of the regions, from which the studied fossil cephalopods originate. The third and final part of the thesis provides a discussion and interpretation of the results of the published studies in the context of the previously published research. The genus Bactroceras Holm, 1898 and some members of the order Litui- tida were studied...

Σκοπός της παρούσας διατριβής, ήταν α) η μελέτη της συστηματικής των Κεφαλοπόδων και ειδικώτερα της κατανομής και των συναθροίσεών τους στο Θρακικό πέλαγος και τους κόλπους Στρυμωνικό, Συγγιτικό, Τορωναίο, Θερμαϊκό και β) η μελέτη του βιολογικού κύκλου των ειδών Loligo vulgaris (καλαμάρι), Illex coindetii (θράψαλο) και Sepietta oweniana. Το υλικό που χρησιμοποιήθηκε προήλθε κυρίως από 8 δειγματοληψίες (9/91 – 12/93) που πραγματοποιήθηκαν από το EΛ.ΚΕ.Θ.Ε., με τράτα βυθού, σε βάθη 17- 400 m. Για τη μελέτη της βιολογίας των 2 Τευθοειδών το υλικό συμπληρώθηκε με μηνιαία λήψη δειγμάτων (2/92 – 6/93) από την επαγγελματική αλιεία στο ΒΑ Αιγαίο. Συνολικά προσδιορίστηκαν 28 είδη Κεφαλοπόδων, από 8 διαφορετικές οικογένειες: Enoploteuthidae (1 είδος), Histioteuthidae (1 είδος), Loliginidae (3 είδη), Ommastrephidae (3 είδη), Sepiidae (3 είδη), Sepiolidae (9 είδη), Argonautidae (1 είδος) και Octopodidae (7 είδη). Πολυπαραγοντικές αναλύσεις των λογαριθμικά τροποποιημένων δεδομένων αφθονίας των ειδών ανά δειγματοληπτική σύρση, έδειξαν διαφοροποιήσεις στη δομή των συναθροίσεων των Κεφαλοπόδων κατά κύριο λόγο με το βάθος και σε μικρότερο βαθμό με την εποχή και τη γεωγραφική περιοχή δειγματοληψίας. Στα είδη I. coindetii και S. oweniana διαπιστώθηκε αναπαραγωγική δραστηριότητα καθόλη τη διάρκεια του χρόνου, με μέγιστη ένταση αντίστοιχα το φθινόπωρο και χειμώνα – άνοιξη. Η αναπαραγωγική περίοδος για το νηριτικό L. vulgaris ήταν σχετικά πιό περιορισμένη (μέσα χειμώνα - αρχές φθινοπώρου) με μέγιστη ένταση την άνοιξη. Η ηλικία των 2 τευθοειδών, που εκτιμήθηκε απο την ανάγνωση των αυξητικών δακτυλίων σε στατολίθους, δεν ξεπερνά τους 14 μήνες ενώ ο ημερήσιος ρυθμός αύξησης του μανδύα φτάνει για το καλαμάρι τα 2-2,5 mm και για το θράψαλο τα 0,5-0,6 mm. Οι Οστειχθείς και τα Κεφαλόποδα αποτελούσαν τις πιο συχνά εμφανιζόμενες λείες στο στομαχικό περιεχόμενο των δύο Τευθοειδών, ενώ τα Καρκινοειδή την προτιμώμενη λεία για το είδος S. oweniana. / The twofold aim of this study was: firstly to contribute to the knowledge of the cephalopod species taxonomy in the Greek Seas, focusing particularly on faunistic composition at the N. Aegean (ΝΕ Mediterranean), and secondly to investigate the life history patterns of the species Loligo vulgaris, Illex coindetii and Sepietta oweniana. Faunistic study was based on samples collected from the N. Aegean Sea (N>39ο 50΄) during eight trawl surveys (9/91 – 12/93), carried out at depths 17 - 400 m. For the study of the two squid species biology, additional monthly samples were collected from commercial fishery in NE Aegean Sea during the period February 1992 - June 1993. In all, 28 species of cephalopods belonging to 8 families were identified including Enoploteuthidae (1 species), Histioteuthidae (1 species), Loliginidae (3 species), Ommastrephidae (3 species), Sepiidae (3 species), Sepiolidae (9 species), Argonautidae (1 species) and Octopodidae (7 species). To detect zonation patterns in cephalopod community structure, multivariate analyses of species abundance data per haul were performed. Considerable variability was shown in assemblage structure, determined primarily by depth, and to a lesser extent, by geographical location and season. Intermittent terminal spawning pattern has been shown for all 3 examined species. Spawning occurs throughout the year for I. coindetii and S. oweniana in the N. Aegean Sea, peaking respectively in autumn and winter-spring, as indicated by minimum ML50 values. The breeding season of neritic L. vulgaris extends from late winter to early autumn, with spawning intensity varying among years, due to variation in temperature and population age structure. Age of both teuthoid species, estimated by growth increment counts on statoliths, did not exceed 14 months. Daily growth rate (DGR) reached 2-2,5 mm in L. vulgaris and 0,5-0,6 mm in I. coindetii. L. vulgaris and I. coindetii feed primarily on fishes and cephalopods in the N. Aegean Sea, whereas S. oweniana on crustacean and fishes.