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Consecutive Breeding Seasons (consecutive + breeding_season)
Selected AbstractsPhenology determines seasonal variation in ectoparasite loads in a natural insect populationECOLOGICAL ENTOMOLOGY, Issue 4 2010CHRISTOPHER HASSALL 1. The extent to which individuals are parasitised is a function of exposure to parasites and the immune response, which in ectotherms may be associated with temperature. 2. We test the hypothesis that seasonal variation in ectoparasite burden is driven by temperature using an extensive mark-release-recapture study of adult Coenagrion puella (L.) (Zygoptera) as a model system. Mite counts were taken both at capture and on a subset of subsequent recaptures over two entire, consecutive breeding seasons. 3. Emergence date was the most significant factor in determining individual differences in mite burden, and mean counts for individuals emerging on the same days showed strong unimodal relationships with time of season. Subsequent recounting of mites on a subset of individuals showed that patterns of loss of mites were similar between seasons. 4. While temperature did not significantly affect mite burdens within seasons and ectoparasite prevalence was very similar across the two seasons, intensity of infection and rate of mite gain in unparasitised individuals were significantly higher in the cooler season. 5. We demonstrate that, while temperature may modulate the invertebrate immune response, this modulation does not manifest in variations in mite burdens in natural populations. [source] Single layer centrifugation of stallion spermatozoa consistently selects the most robust spermatozoa from the rest of the ejaculate in a large sample sizeEQUINE VETERINARY JOURNAL, Issue 7 2010J. M. MORRELL Summary Reasons for performing study: An improvement in sperm quality after single layer centrifugation (SLC) has been seen in previous studies using small sample sizes (for example, n = 10 stallions). There is a need to investigate whether this improvement is repeatable over several breeding seasons with a larger number of stallions (n , 30 stallions). Objective: To make a retrospective analysis of the results of SLC performed on more than 250 sperm samples (176 ejaculates) from 31 stallions in 3 consecutive breeding seasons. Methods: Sperm quality (motility, proportion of morphologically normal spermatozoa and the proportion of spermatozoa with undamaged chromatin) was assessed before and after SLC. Results: All parameters of sperm quality examined were significantly better in sperm samples after SLC than in their unselected counterparts (P<0.001 for each parameter). The yield of spermatozoa obtained after SLC was influenced by the type of extender used and also by the concentration of spermatozoa in the original ejaculate, with fewer spermatozoa being recovered when the loading dose contained a high concentration of spermatozoa. The optimal concentration was approximately 100 × 106/ml. Sperm concentration in the samples loaded on to the colloid influenced the sperm yield while the type of semen extender affected sperm quality and survival. Furthermore, the scaled-up SLC method was found to be suitable for use with a range of ejaculates, with similar sperm kinematics being observed for standard and scaled-up preparations. Conclusions: SLC consistently improved the quality of stallion sperm samples from a large number of ejaculates. The method could be scaled-up, allowing larger volumes of ejaculate to be processed easily from a wide range of stallions. [source] Can the limited marsupium space be a limiting factor for Syngnathus abaster females?JOURNAL OF ANIMAL ECOLOGY, Issue 2 2008Insights from a population with size-assortative mating Summary 1Some syngnathid species show varying degrees of sex role reversal aside from male pregnancy, with females competing for access to mates and sometimes presenting conspicuous secondary sexual characters. Among other variables, brooding space constraints are usually considered a key element in female reproductive success, contributing strongly to the observed morphological and behavioural sexual differences. Nevertheless, a close relationship between sex role reversal and male brooding space limitation has not yet been accurately demonstrated in field studies. 2The present work, conducted over two consecutive breeding seasons in a wild population of the sex role-reversed pipefish Syngnathus abaster, simultaneously analysed egg number and occupied space, as well as the free area in the male's marsupium. The number of eggs that would fit in the observed unoccupied space was estimated. 3Contrary to what would be expected, given the marked sexual dimorphism observed in the population studied, where females were larger and more colourful, male brooding space did not appear to limit female reproduction as neither large nor small individuals presented a fully occupied pouch. Interestingly, the largest unoccupied areas of marsupium were found in the larger individuals, although they received more and larger eggs. Laboratory data also showed that larger females lay larger eggs. 4Together, these results suggest the existence of assortative mating, which may result from: (i) the reluctance of larger males (which tend not to receive small eggs usually laid by small females) to mate with lower quality females, even at the expense of a smaller number of offspring; or (ii) female,female competition, which might strongly reduce the hypothesis of a small female mating with a large male. The potential impact of temperature on reproduction and population dynamics is also discussed in the light of ongoing climatic changes. [source] Forest fragmentation relaxes natural nest predation in an Afromontane forestANIMAL CONSERVATION, Issue 4 2009T. Spanhove Abstract Nest predation is widely regarded as a major driver underlying the population dynamics of small forest birds. Following forest fragmentation and the subsequent invasion by species from non-forested landscape matrices, shifts in predator communities may increase nest predation near forest edges. However, effects of human-driven habitat change on nest predation have mainly been inferred from studies with artificial nests, despite being regarded as poor surrogates for natural ones. We studied variation in predation rates, and relationships with timing of breeding and characteristics of microhabitats and fragments, on natural white-starred robin Pogonocichla stellata nests during three consecutive breeding seasons (2004,2007) in a Kenyan fragmented cloud forest. More than 70% of all initiated nests were predated during each breeding season. Predation rates nearly quadrupled between the earliest and the latest nests within a single breeding season, increased with distance to the forest edge, and decreased with the edge-to-area ratio of forest fragments. These spatial relationships oppose the traditional perception of edge and fragmentation effects on nest predation, but are in line with results from artificial nest experiments in other East African forests. In case of inverse edge and fragmentation effects on nest predation, such as shown in this study, species that tolerate edges for breeding may be affected positively, rather than negatively, by forest fragmentation, while the opposite can be expected for species restricted to the forest interior. The possibility of inverse edge effects, and its conservation implications, should therefore be taken into account when drafting habitat restoration plans. [source] | ||||||||||