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No. of bitstreams: 1 haroldolobodossantosnascimento.pdf: 3868832 bytes, checksum: b4398e42d1a17af79bda9794eeb63bc3 (MD5) Previous issue date: 2009-02-06 / FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais / Os representantes da classe Oligochaeta são de grande importância para os ecossistemas dulciaquícolas, pois além de participarem do processo de mineralização da matéria orgânica, fazem a mistura do sedimento, transportando substâncias profundas para a superfície e tornando-as disponíveis a biota. Dentre os oligoquetas que habitam ambientes límnicos, destaca-se a família Tubificidae, na qual diversas espécies representantes são amplamente estudadas como indicadoras de ambientes poluídos (por exemplo, Tubifex tubifex, Limnodrilus hoffmeisteri e Branchiura sowerbyi). A biologia dessas espécies tem sido objeto de pesquisas em diversos países, porém no Brasil, apesar dos relatos de ocorrência, há uma carência considerável de trabalhos sobre este assunto. Com isso, o presente trabalho teve como objetivo estudar os atributos biológicos de L. hoffmeisteri e B. sowerbyi, oriundos de ambientes aquáticos brasileiros. Para tanto, foram realizados dois experimentos com L. hoffmeisteri: o primeiro para avaliar a influência da temperatura na reprodução e o segundo a influência da biomassa corporal na produção de casulos. Além destes, duas populações, de 30 organismos cada, cultivadas a 25 ± 1°C e em duas frações granulométricas de areia, foram observadas durante um período de 25 semanas, contadas a partir da eclosão do jovem, para verificar o tempo de maturação sexual, crescimento e reprodução da espécie. Já para B. sowerbyi, uma observação de 52 semanas foi realizada para uma população de 30 indivíduos mantida a 25 ± 1°C, tendo como objetivos verificar também a taxa de crescimento, tempo de maturação sexual e taxa de reprodução. A partir dos resultados, verificou-se que a temperatura tem influência na reprodução de L. hoffmeisteri, com maior produção de casulos a temperaturas mais elevadas (25 ± 1°C). Para alguns autores esse fato pode ser utilizado como um parâmetro para indicar poluição térmica em regiões temperadas. Além da temperatura, a biomassa corporal também teve influência na produção de ovos, sendo esta diretamente proporcional ao peso corporal do organismo. Com as observações realizadas durante as 25 semanas, foi possível determinar (valores para areia fina e média respectivamente): tempo de eclosão (8 a 12 dias, para os dois substratos testados), taxa média de crescimento diário (2,14 ± 0,75 e 2,04 ± 0,42%), tempo de maturação sexual (7,17 ± 2,93 e 9,00 ± 2,00 semanas) e número de casulos produzidos por adulto por dia (0,37 ± 0,22 e 0,23 ± 0,24 casulos) de L. hoffmeisteri. De acordo com os resultados, não foi possível afirmar que a espécie se desenvolva melhor em areia de granulometria fina ou média. Já a espécie B. sowebyi, apresenta dois ciclos anuais de reprodução, sendo o primeiro mais expressivo que o segundo   em relação ao número de casulos, visto que a postura foi constante durante o primeiro ciclo e inconstante no segundo. Os resultados do presente estudo revelaram aspectos sobre os atributos biológicos de duas espécies de tubificídeos (L. hoffmeisteri e B. sowerbyi), ainda pouco estudadas no país, os quais podem ser incorporados em futuros estudos ecológicos. / The organisms of the Oligochaeta Class are very important for the aquatic ecosystems, because they both participated in the organic matter mineralization and mixed the sediment, transporting substances deep into the surface, making them available to the biota. Among the limnic oligochaetes, stands the family Tubificidae, in which several species are widely recognized as indicators of organic pollution in aquatic environments (eg. Tubifex tubifex, Limnodrilus hoffmeisteri and Branchiura sowerbyi). The biology of these species has been researched in many countries, but in Brazil, despite the reports of occurrence, there is a lack of studies on their biologies. Thus, the present work aimed to gather information about biological attributes of L. hoffmeisteri and B. sowerbyi from Brazilian aquatic environments. To this end, two experiments involving L. hoffmeisteri were conduced, the first for assess the influence of the temperature on the reproduction and the second the influence of the biomass body on the production of cocoons. In spite of these experiments, two 30-individual populations, cultured in two granulometric fractions of sand and kept at 25 ± 1°C, were observed, during 25 weeks for verify the time spent for reach the maturity, growth and reproduction rate, for the two types of substrate. For B. sowerbyi, a 52-week observation was made for a 30-individual population, aiming to verify the same objectives describes for the other species. From the results, verified that the temperature has great influence on the reproduction of L. hoffmeisteri, a great production of cocoons was recorded at high temperatures. For some authors, this fact could be used as a parameter to indicate thermal pollution in temperate regions. Besides the temperature, biomass body also had an influence on eggs production, which is directly proportional to the weight of the organisms. From the observations during the 25 weeks, it was possible to determine (for fine sand and medium sand, respectively): hatching time (8 to 12 days, for both sediments), the mean specific daily growth rate (2.14 ± 0.75 e 2.04 ± 0.42%), maturation time (7.17 ± 2.93 e 9.00 ± 2.00 weeks) and the mean number of cocoons laid per adult per day (0.37 ± 0.22 e 0.23 ± 0.24 cocoons) for of L. hoffmeisteri. According the results, it isn’t possible to affirm that this species develops better in one of the substrates types tested. B. sowerbyi, according the results of the 52 weeks of observation, shown two annuals reproductive cycles, the first been more expressive, in the number of cocoons, than the second, since the posture of cocoons was constant during all the first cycle and inconstant during the second one. The results of the present work revealed important aspects of the biological attributes of two tubificids species   (L. hoffmeisteri and B. sowerbyi), little studied in Brazil, that should be incorporated into futures ecologies researches.

<p><i>Heterodrilus</i> is a marine group of small (3-25 mm) clitellates that occur interstitially in sandy sediments from the intertidal zone down to about 150 m depths. The taxon includes 42 valid species and has been recorded from localities in the Mediterranean Sea, the North-west Atlantic Ocean (including the Caribbean), the Galapagos Islands, and the Indo-Pacific Region. A majority of the species of <i>Heterodrilus</i> are characterized by having trifid anterior chaetae (i.e., chaetae with three teeth at the distal end). A few species have bifid chaetae, but these are regarded as having lost the third tooth secondarily. Within the taxon, species are distinguished by morphological characters in the internal organization of the male and female genitalia, but also by characters in the form and number of chaetae. In this thesis, two new taxa are introduced, <i>Heterodrilus tripartitus </i>and <i>H. ursulae</i>, both from the Mediterranean Sea. The ultrastructure of the cuticle in four species (<i>H. paucifascis, H. pentcheffi, H</i>. <i>flexuosus, H. minisetosus</i>) is studied and it is shown that there is interspecific variation in the morphology of the cuticle. One of the studied species, <i>H. paucifascis</i>, shows intraspecific variation, which is associated with sample locality. The systematic position of <i>Heterodrilus</i> within Tubificidae is studied with molecular markers, and the results support that <i>Heterodrilus </i>(earlier classified as a member of Rhyacodrilinae) is positioned within Phallodrilinae. Furthermore, the phylogenetic relationships within <i>Heterodrilus</i> are estimated based on molecular characters from mitochondrial COI, the 16S rRNA gene, and the nuclear 18S rRNA gene, and the result indicate that the two major clades in our tree corresponds to different geographical distributions. This thesis also includes a checklist, as well as a key, to the species of <i>Heterodrilus</i>.</p>

Heterodrilus is a marine group of small (3-25 mm) clitellates that occur interstitially in sandy sediments from the intertidal zone down to about 150 m depths. The taxon includes 42 valid species and has been recorded from localities in the Mediterranean Sea, the North-west Atlantic Ocean (including the Caribbean), the Galapagos Islands, and the Indo-Pacific Region. A majority of the species of Heterodrilus are characterized by having trifid anterior chaetae (i.e., chaetae with three teeth at the distal end). A few species have bifid chaetae, but these are regarded as having lost the third tooth secondarily. Within the taxon, species are distinguished by morphological characters in the internal organization of the male and female genitalia, but also by characters in the form and number of chaetae. In this thesis, two new taxa are introduced, Heterodrilus tripartitus and H. ursulae, both from the Mediterranean Sea. The ultrastructure of the cuticle in four species (H. paucifascis, H. pentcheffi, H. flexuosus, H. minisetosus) is studied and it is shown that there is interspecific variation in the morphology of the cuticle. One of the studied species, H. paucifascis, shows intraspecific variation, which is associated with sample locality. The systematic position of Heterodrilus within Tubificidae is studied with molecular markers, and the results support that Heterodrilus (earlier classified as a member of Rhyacodrilinae) is positioned within Phallodrilinae. Furthermore, the phylogenetic relationships within Heterodrilus are estimated based on molecular characters from mitochondrial COI, the 16S rRNA gene, and the nuclear 18S rRNA gene, and the result indicate that the two major clades in our tree corresponds to different geographical distributions. This thesis also includes a checklist, as well as a key, to the species of Heterodrilus.