68 resultados para moulting


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The allometric growth of secondary sexual characters in Pachygrapsus transversus is investigated from the 2(nd) crab stage onward. Clear sexual dimorphism is restricted to abdominal morphology, but ANCOVA analyses showed that chelae become larger in males and the carapace becomes wider in females. Size at the puberty moult in both sexes was estimated using Somerton's computer techniques. Mature II analyses applied to bi-log gonopod length vs, carapace length relationships indicated a puberty moult at 5.0 mm in males.In females, Mature I analyses detected the overlapping growth phase lines in bi-log carapace length vs. abdomen width scatterplots. Fitting the logistic equation provided an estimate of 50% maturity at 5.5 mm. The regression lines separate young and resting individuals from the potentially reproductive females, but they do not separate young from adult crabs. Year-round monthly samples showed that the proportion of small adult-like females is higher during the breeding season. After breeding, females may moult to a young-like morphotype, as observed in controlled laboratory conditions. Moulting to a resting condition splits smaller mature females into different growth phase lines. Therefore, estimates of female size at sexual maturity by means of abdomen allometric growth analyses are inadequate in this species.

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Six cattle that had earlier exposure to Dermatobia hominis were infested experimentally with first-instar larvae of the parasite. Skin biopsies taken at intervals were studied in wax and in plastic sections. The avidin-biotin-peroxidase method was used to detect the presence and localization of host immunoglobulins (Igs) G and M and antigens of first and second instar larvae of Dermatobia hominis. The larvae penetrated actively through the skin and migrated towards the subcutaneous tissues. The great numbers of eosinophils suggest that they are the most important cell in mediating damage to D.hominis larvae. The immunoglobulins bound only to dead or moulting larvae in which access to binding sites may have been altered. This could represent a morphological manifestation of a mechanism that protects larvae from the host immune response. Large amounts of soluble antigens detected along the fistulous tract may be important in the maintenance of this tract by disturbing the normal cicatrization process.

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The larval development of Pyromaia tuberculata (Lockington, 1877) is described from specimens reared in the laboratory. Larvae were obtained from ovigerous females collected by trawl in Ubatuba, São Paulo state, Brazil. Rearing was carried out at 24 +/- 1 degrees C in 35 parts per thousand S. The larvae pass through two zoeal stages before moulting to the megalopa. A comparison is made with previously studied majid species occurring in the southern and southeastern regions of Brazil.

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Larvae of an estuarine grapsid crab Chasmagnathus granulata Dana 1851, from temperate and subtropical regions of South America, were reared in seawater (32 ‰) at five different constant temperatures (12, 15, 18, 21, 24 °C). Complete larval development from hatching (Zoea I) to metamorphosis (Crab I) occurred in a range from 15 to 24 °C. Highest survival (60% to the first juvenile stage) was observed at 18°C, while all larvae reared at 12°C died before metamorphosis. The duration of development (D) decreased with increasing temperature (T). This relationship is described for all larval stages as a power function (linear regressions after logarithmic transformation of both D and T). The temperature-dependence of the instantaneous developmental rate (D-1) is compared among larval stages and temperatures using the Q10 coefficient (van't Hoff's equation). Through all four zoeal stages, this index tends to increase during development and to decrease with increasing T (comparing ranges 12-18, 15-21, 18-24 °C). In the Megalopa, low Q10 values were found in the range from 15 to 24 °C. In another series of experiments, larvae were reared at constant 18°C and their dry weight (W) and respiratory response to changes in T were measured in all successive stages during the intermoult period (stage C) of the moulting cycle. Both individual and weight-specific respiration (R, QO2) increased exponentially with increasing T. At each temperature, R increased significantly during growth and development through successive larval stages. No significantly different QO2 values were found in the first three zoeal stages, while a significant decrease with increasing W occurred in the Zoea IV and Megalopa. As in the temperature-dependence of D, the respiratory response to changes in temperature (Q10) depends on both the temperature range and the developmental stage, however, with different patterns. In the zoeal stages, the respiratory Q10 was minimum (1.7-2.2) at low temperatures (12-18 °C), but maximum (2.2-3.0) at 18-24 °C. The Megalopa, in contrast, showed a stronger metabolic response in the lower than in the upper temperature range (Q10 = 2.8 and 1.7, respectively). We interpret this pattern as an adaptation to a sequence of temperature conditions that should typically be encountered by C. granulata larvae during their ontogenetic migrations: hatching in and subsequent export from shallow estuarine lagoons, zoeal development in coastal marine waters, which are on average cooler, return in the Megalopa stage to warm lagoons. We thus propose that high metabolic sensitivity to changes in temperature may serve as a signal stimulating larval migration, so that the zoeae should tend to leave warm estuaries and lagoons, whereas the Megalopa should avoid remaining in the cooler marine waters and initiate its migration towards shallow coastal lagoons.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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O presente estudo investigou se o callianassid Callichirus major apresenta um comportamento lecitotrófico durante o desenvolvimento larval. Dois experimentos foram realizados. No primeiro experimento, larvas foram submetidas a um período inicial de alimentação, enquanto no segundo elas foram submetidas a um período inicial de inanição. No experimento 1, 80% das larvas de C. major mudaram com sucesso para o estágio de juvenil no tratamento com larvas alimentadas diariamente. Nos tratamentos com larvas alimentadas por 1, 2 e 3 dias, houve uma mortalidade total antes de alcançarem o estágio de megalopa. No experimento 2, as larvas zoés mostraram mais resistência quando submetidas a um período inicial de inanição. Nos tratamentos nos quais as larvas estiveram em inanição por 1, 2 e 3 dias, as taxas de sobrevivência foram100%, 60% e 90%, respectivamente. Porém atrasos na duração do desenvolvimento dos estágios de zoés foram observados. Houve mortalidade total para as larvas cultivadas no tratamento com ausência constante de alimento. Os resultados sugerem não existir um comportamento lecitotrófico nas zoés de C. major.

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Megalopas de muitas espécies de caranguejos decápodes aceleram seu período de desenvolvimento até a metamorfose (TOM) quando são expostas a estímulos naturais físicos e/ou químicos característicos do habitat parental. No presente estudo, a influência de estímulos naturais sobre as taxas de muda e sobre o PDM foi investigada nas megalopas do caranguejo violinistac. Os efeitos da (i) lama de diferentes habitats (incluindo habitats de um manguezal bem preservado e de um degradado e poluído) e (ii) 'odores' dos adultos conspecíficos (água do mar acondicionada com caranguejos) sobre a indução da metamorfose foram comparados com (iii) água do mar pura e filtrada (controle). 95 a 100% das megalopas realizaram a metamorfose com sucesso para o primeiro estágio de caranguejo juvenil em todos os tratamentos, incluindo o controle. No entanto, o PDM diferiu significativamente entre os tratamentos. Os estímulos encurtaram significativamente o desenvolvimento, enquanto que a muda foi retardada na ausência deles. O fato de que as megalopas responderam aos estímulos indutores da metamorfose oriundos de ambos os habitats bentônicos dos adultos e de habitats onde eles são ausentes, demonstra que o assentamento nesta espécie pode ocorrer em uma grande variedade de habitats dentro do ecossistema de manguezal, incluindo áreas impactadas.

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Canada Geese overflying the runways at London’s Heathrow Airport have been struck on eleven occasions by aircraft during the last ten years. Four of these occurred during the pre-breeding season and seven during the post moult period. A monitoring study was initiated in 1999 to evaluate the movements of geese around the airport and determine appropriate mitigation strategies to reduce the risk of birdstrike. Moult sites within 13km of the airport were identified. 4,900 moulting geese were caught and fitted with colour rings and radio-transmitters between 1999 and 2004. 2,500 visits were made to over 300 sites resulting in over 10,000 sightings of known individuals. Birds that crossed the airport approaches whilst moving between roost sites and feeding areas in newly harvested cereal crops were identified. Throughout the monitoring period efforts were made to control the risk, but by 2003 it was estimated that 10,000 bird transits of the approaches involving almost 700 individuals occurred during a 50 day period. The knowledge of the movements of ringed and tagged birds was used to inform a revised habitat management, daily roost dispersal and on-airfield bird deterrence programme in 2004. By adopting a flexible approach to management, an estimated 70% reduction in bird transits was achieved. This paper discusses the techniques used to achieve this reduction.

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By the end of the 1960s, the argasid tick Ornithodoros peropteryx was described from larval specimens collected from the bat Peropteryx macrotis in Colombia. Since its original description, no additional record of O. peropteryx has been reported, and its post-larval stages have remained unknown. During July 2010, 18 larvae were collected from 9 bats (Centronycteris maximiliani), resulting in a mean infestation of 2.0 ± 2.2 ticks per bat (range 1–8). These bats were captured in a farm in northeastern Bolivia close to Guaporé River in the border with Brazil. Morphological examinations of the larvae revealed them to represent the species O. peropteryx. One engorged larva that was kept alive in the laboratory moulted to a nymph after 9 days. Fourteen days after the larval moulting, the nymph moulted to an adult female without taking any blood meal during the nymphal period. This adult female was used for a morphological description of the female stage of O. peropteryx. In addition, the larvae were used for a morphological redescription of this stage. One larva and two legs extirpated from the adult female were submitted to DNA extraction and PCR targeting a fragment of the mitochondrial 16S rDNA gene, which yielded DNA sequences at least 11 % divergent from any available argasid sequence in Genbank. We show that O. peropteryx ontogeny is characterized by a single, non-feeding, nymphal stage. This condition has never been reported for ticks.

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By the end of the 1960s, the argasid tick Ornithodoros peropteryx was described from larval specimens collected from the bat Peropteryx macrotis in Colombia. Since its original description, no additional record of O. peropteryx has been reported, and its post-larval stages have remained unknown. During July 2010, 18 larvae were collected from 9 bats (Centronycteris maximiliani), resulting in a mean infestation of 2.0 ± 2.2 ticks per bat (range 1–8). These bats were captured in a farm in northeastern Bolivia close to Guapore´ River in the border with Brazil. Morphological examinations of the larvae revealed them to represent the species O. peropteryx. One engorged larva that was kept alive in the laboratory moulted to a nymph after 9 days. Fourteen days after the larval moulting, the nymph moulted to an adult female without taking any blood meal during the nymphal period. This adult female was used for a morphological description of the female stage of O. peropteryx. In addition, the larvae were used for a morphological redescription of this stage. One larva and two legs extirpated from the adult female were submitted to DNA extraction and PCR targeting a fragment of the mitochondrial 16S rDNA gene, which yielded DNA sequences at least 11 % divergent from any available argasid sequence in Genbank. We show that O. peropteryx ontogeny is characterized by a single, non-feeding, nymphal stage. This condition has never been reported for ticks.

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The water spider Argyroneta aquatica (Clerck) is the only spider that spends its whole life under water. Water spiders keep an air bubble around their body for breathing and build under-water air bells, which they use for shelter and raising offspring, digesting and consuming prey, moulting, depositing eggs and sperm, and copulating. It is unclear whether these bells are an important oxygen reservoir for breathing under water, or whether they serve mainly to create water-free space for feeding and reproduction. In this study, we manipulated the composition of the gas inside the bell of female water spiders to test whether they monitor the quality of this gas, and replenish oxygen if required. We exchanged the entire gas in the bell either with pure O(2), pure CO(2), or with ambient air as control, and monitored behavioural responses. The test spiders surfaced and replenished air more often in the CO(2) treatment than in the O(2) treatment, and they increased bell building behaviour. In addition to active oxygen regulation, they monitored and adjusted the bells by adding silk. These results show that water spiders use the air bell as an oxygen reservoir, and that it functions as an external lung, which renders it essential for living under water permanently. A. aquatica is the only animal that collects, transports, and stores air, and monitors its property for breathing, which is an adaptive response of a terrestrial animal to the colonization of an aquatic habitat. J. Exp. Zool. 307A:549-555, 2007. (c) 2007 Wiley-Liss, Inc.