Spermiogenesis and ultrastructure of the spermatozoon of two bothriocephalidean cestodes, Oncodiscus sauridae and Senga sp., have been studied using transmission electron microscopy. The presence of a classical pattern for spermatological characters (spermiogenesis of type I with dense-material in early stages and sperm of type II with a characteristic ring of cortical microtubules in the anterior part) in Bothriocephalidea is discussed.

Estudos co-evolutivos requerem uma base taxonômica e filogenética robusta para estabelecerem de forma inequívoca as relações entre as linhagens envolvidas. Neste sentido, a presente contribuição identificou as linhagens de parasitas marinhos das espécies anfi-Americanas de Himantura Müller & Henle, considerado o suposto grupo-irmão dos potamotrigonídeos - arraias Neotropicais restritas ao sistemas fluviais da America do Sul. O objetivo do presente estudo foi contribuir com o alicerce taxonômico necessário para a elucidar as associações históricas entre as arraias de água doce, seu suposto grupo-irmão marinho, e suas faunas helmintológicas. Neste sentido, este estudo aborda a diversidade de três gêneros de cestóideos, cujas linhagens são compartilhadas entre arraias marinhas e potamotrigonídeos: Acanthobothrium Blanchard, 1948, Anindobothrium Marques, Brooks & Lasso, 2001 e Rhinebothrium Linton, 1890. Cada um destes grupos é abordado em um capítulo individualmente. Os resultados deste estudo incluem a descrição de 11 espécies novas, dentre as quais, sete são parasitas de H. schmardae (Werner) e 4 parasitas de H. pacifica (Beebe & Tee-Van), além da redescrição de três espécies previamente conhecidas para H. schmardae. Todas as descrições e redescrições foram baseadas em um número de indivíduos sem precedentes na taxonomia dos grupos e incluíram dados sobre microscopia eletrônica de varredura dentro dos padrões atuais de descrições taxonômicas. Este estudo também abordou as relações filogenéticas das linhagens de Acanthobothrium e Anindobothrium. Em ambos os casos, dados moleculares revelam congruência entre as relações de parentesco de seus membros e aqueles evidenciados para seus hospedeiros. Os dados parasitológicos apresentados corroboram hipóteses recentes que postulam que potamotrigonídeos compartilham um ancestral comum com as linhagens anfi-Americanas de Himantura. Por fim, algumas abordagens utilizadas neste estudo ilustram os benefícios de integrar diferentes bases de dados no refinamento taxonômico destes grupos dentro do conceito do que hoje reconhecemos como taxonomia integrativa / Studies on the co-evolution require accurate taxonomic and phylogenetic information to unambiguously establish associations within the lineages involved. Therefore, the present study identified marine parasite lineages from amphi-American species of Himantura Müller & Henle, H. schmardae (Werner) and H. pacifica (Beebe & Tee-Van). These hosts are considered the sister-group of potamotrygonids, which are Neotropical freshwater stingrays restricted to river systems in South America. Our motivation was the contribution on sound taxonomic grounds, in order to elucidate the historical associations among freshwater batoids, their alleged marine sister-group and their cestode parasites. To achieve this goal, we documented the fauna of three genera of cestodes, whose lineages can be found both in marine and freshwater stingrays, namely Acanthobothrium Blanchard, 1948, Anindobothrium Marques, Brooks & Lasso, 2001 and Rhinebothrium Linton, 1890. Each chapter addresses each genus separately. Our results consist of descriptions of 11 species new to science, among which seven are found parasitizing H. schmardae and 4 infecting H. pacifica. Furthermore, redescriptions are provided for three species detected in H. schmardae. All descriptions and redescriptions were based on an unprecedented number of specimens and included data obtained from histology, ligth microscopy and scanning electron microscopy. In addition to the taxonomic approach, we evaluated the phylogenetic relationships of Acanthobothrium and Anindobothrium. Molecular data from both genera revealed the congruence between the known patterns of host relationships and their parasites. The parasitological data presented in this study supports the recent hypothesis that potamotrygonids and amphi-American species of Himantura share a common ancestor. Moreover, the combined approach applied in this study illustrates the benefits of integrating different data sources for the taxonomic refinement of these groups within the concept of integrative taxonomy

<p>In the freshwater copepod, <i>Macrocyclops albidus,</i> food availability, rearing conditions and tapeworm infection clearly affected various life-history traits and their trade-offs. I found that low food availability clearly constrained resource allocations to several life-history (often phenotypically plastic) traits, whereas high food availability either allowed for adjustments in resource allocation patterns or allowed resources to be allocated to several traits without apparent trade-offs. </p><p>Both male and female copepods allocated resources according to food availability; developing more slowly and achieving smaller adult body size when food was scarce. When food availability was low females were constrained and produced fewer eggs (in total and per clutch), and started reproduction later than females with more food available. Males under low food availability allocated relatively more to spermatophore size (current reproduction) with decreasing body size. In contrast, when food availability was high males allocated resources to body size as well as spermatophore size. Overall, at maturity, copepods of both sexes were more similar in size than in age, suggesting that large body size was more important for fitness than fast development. </p><p>In nature the prevalence of copepods infected with cestode tapeworms was found to be low (0-3%). Female copepods, experimentally infected with the cestode <i>Schistocephalus solidus</i>, showed lower overall fecundity, especially when food availability was low. However, infected females produced a larger proportion of their life-time egg production early in life than non-infected females. This might be an adaptation to reduce future fitness costs of infection. Females grown under bad rearing conditions, but with high food availability, produced their first clutch earlier than females grown under good rearing conditions, indicating an adjustment in timing of reproduction. These findings contribute to our fundamental evolutionary understanding of how environmental conditions interact with life-history traits.</p>

In the freshwater copepod, Macrocyclops albidus, food availability, rearing conditions and tapeworm infection clearly affected various life-history traits and their trade-offs. I found that low food availability clearly constrained resource allocations to several life-history (often phenotypically plastic) traits, whereas high food availability either allowed for adjustments in resource allocation patterns or allowed resources to be allocated to several traits without apparent trade-offs. Both male and female copepods allocated resources according to food availability; developing more slowly and achieving smaller adult body size when food was scarce. When food availability was low females were constrained and produced fewer eggs (in total and per clutch), and started reproduction later than females with more food available. Males under low food availability allocated relatively more to spermatophore size (current reproduction) with decreasing body size. In contrast, when food availability was high males allocated resources to body size as well as spermatophore size. Overall, at maturity, copepods of both sexes were more similar in size than in age, suggesting that large body size was more important for fitness than fast development. In nature the prevalence of copepods infected with cestode tapeworms was found to be low (0-3%). Female copepods, experimentally infected with the cestode Schistocephalus solidus, showed lower overall fecundity, especially when food availability was low. However, infected females produced a larger proportion of their life-time egg production early in life than non-infected females. This might be an adaptation to reduce future fitness costs of infection. Females grown under bad rearing conditions, but with high food availability, produced their first clutch earlier than females grown under good rearing conditions, indicating an adjustment in timing of reproduction. These findings contribute to our fundamental evolutionary understanding of how environmental conditions interact with life-history traits.

No description available.