Zoology最新文献

Islands provide excellent settings for studying the evolutionary history of species, since their geographic isolation and relatively small size limit gene flow between populations, and promote divergence and speciation. The endemic Bolle's Laurel Pigeon Columba bollii is an arboreal frugivorous bird species distributed on laurel forests in four islands of the Canary archipelago. To elucidate the population genetics, we genotyped ten microsatellite loci using DNA obtained from non-invasive samples collected across practically all laurel forest remnants, and subsequently grouped into eight sampling sites. Analyses including F-statistics, Bayesian clustering approaches, isolation by distance tests and population graph topologies, were used to infer the genetic diversity and the population differentiation within and among insular populations. Additionally, we evaluated the effect of null alleles on data analysis. Low genetic diversity was found in all populations of Bolle’s Laurel Pigeon, with no significant differences in diversity among them. However, significant genetic differentiation was detected among all populations, with pigeons from La Palma and El Hierro exhibiting the closest affinity. Bayesian clustering supported population separation between islands, and also detected fine-scale structure within the Tenerife and La Gomera populations. Our results suggest that, despite columbids have a high movement ability, they can show signature of genetic divergence among populations, particularly on oceanic islands. Geological history of the islands and distribution range of habitats could have close influence on the evolutionary trajectories of these birds. This approach can provide practical tools to implement appropriate conservation measures for range-restricted species and their habitat.

Living at high altitudes impose physiological and ecological challenges to which species may respond altering their body size, body proportions, and the shape of their body parts. Despite the importance of this topic for understanding the origin of species diversity, little attention has been invested in this phenomenon at the populational level. This paper study the relationship between altitude and body size, body proportions, and forewing shape venation of two populations of the parasitoid wasp Cotesia flavipes. Wasps were collected from Diatraea spp. larvae from sugarcane crops in two Colombian mountain ranges that cover between 600 m and 2143 m of altitude. Linear measurements of different body regions and geometric morphometrics of the forewing were subject to multivariate comparisons and allometric analyses to assess variation and to compare trends between ranges. Central (600 m to 1704 m) and Eastern Cordillera (877 m to 2143 m) populations showed different trends between body size and altitude. Allometric trends were not uniform within or between populations nor between structures. The allometric slopes of five body measurements from a single altitude differed from these from its own mountain range suggesting that body size trends along the cordilleras are a consequence of altitude and not of intrinsic body resource allocation processes. Wing shape between populations differed; however, these changes were poorly related to altitude. In agreement with recent studies in other groups, the observed allometric and wing shape differences between the two C. flavipes populations could be a plasticity response to altitude with interesting implications for posterior genetic differentiation.

Sexual activity (mating) negatively affects immune function in various insect species across both sexes. In Drosophila melanogaster females, mating increases susceptibility to pathogenic challenges and encourages within-host pathogen proliferation. This effect is pathogen and host genotype dependent. We tested if mating-induced increased susceptibility to infections is more, or less, severe in hosts experimentally adapted to pathogenic infection. We selected replicate D. melanogaster populations for increased post-infection survival following infection with a bacterial pathogen, Enterococcus faecalis. We found that females from the selected populations were better at surviving a pathogenic infection compared to the females from the control populations. This was true in the case of both the pathogen used for selection and other novel pathogens (i.e., pathogens the hosts have not encountered in recent history). Additionally, the negative effect of mating on post-infection survival was limited to only the females from control populations. Therefore, we have demonstrated that experimental selection for increased post-infection survival ameliorates negative effects of mating on host susceptibility to infections.

For small non-hibernating mammals, a high thermogenic capacity is important to increase activity levels in the cold. It has been previously reported that lactating females decrease their thermogenic activity of brown adipose tissue (BAT), whereas their capacity to cope with extreme cold remains uncertain. In this study we examined food intake, body temperature and locomotor behavior, resting metabolic rate, non-shivering thermogenesis, and cytochrome c oxidase activity, and the rate of state 4 respiration of liver, skeletal muscle, and BAT in striped hamsters (Cricetulus barabensis) at peak lactation and non- breeding hamsters (controls). The lactating hamsters and non- breeding controls were acutely exposed to −15°C, and several markers indicative of thermogenic capacity were examined. In comparison to non-breeding females, lactating hamsters significantly increased food intake and body temperature, but decreased locomotor behavior, and the BAT mass, indicative of decreased BAT thermogenesis at peak lactation. Unexpectedly, lactating hamsters showed similar body temperature, resting metabolic rate, non-shivering thermogenesis with non-breeding females after acute exposure to −15°C. Furthermore, cytochrome c oxidase activity of liver, skeletal muscle and BAT, and serum thyroid hormone concentration, and BAT uncoupling protein 1 expression, in lactating hamsters were similar with that in non-breeding hamsters after acute extreme cold exposure. This suggests that lactating females have the same thermogenic capacity to survive cold temperatures compared to non-breeding animals. This is particularly important for females in the field to cope with cold environments during the period of reproduction. Our findings indicate that the females during lactation, one of the highest energy requirement periods, do not impair their thermogenic capacity in response to acute cold exposure.

Osteoglossomorpha, the bony tongue fishes, show great variation in morphology, behavioural strategies, reproductive biology and gamete ultrastructure. The order Osteoglossiformes is the only vertebrate taxon, in which four types of sperm (monoflagellate, biflagellate and aflagellate aquasperm and the complex introsperm) have been described. It is also the only vertebrate lineage in which aflagellate spermatozoa exist. The aim of this study was to analyse the structure of the testis and the process of spermiogenesis in the mormyrid Campylomormyrus compressirostris during the breeding season using light and electron microscopy (transmission and scanning). Males of this species have a single testis of the anastomosing tubular type. The tubules of the anterior part of the testis contain cysts with developing germ cells, and this region is much wider than the posterior part, which consists of efferent ducts filled with sperm cells. The cysts are filled with single or mitotic spermatogonia, primary and secondary spermatocytes and early spermatids. At the stage of spermatids with fine granular chromatin, the cysts rupture and successive stages of spermatid differentiation take place in the testicular lumen; we therefore characterise this process as ‘extracystic spermiogenesis’. Sperm development in C. compressirostris is extremely simple and involves chromatin condensation in the central region of the nucleus, a slight decrease in nuclear volume, the appearance of numerous vesicles in the cytoplasm that form a tubular-vesicular system at the base of the nucleus. Both centrioles and mitochondria are translocated to the peripheral region of the midpiece, which forms the opposite pole to the nucleus. There are many differences between the types of spermiogenesis described so far in teleosts and that found in C. compressirostris, including the loss of flagellum formation. This unique type of spermiogenesis is restricted to species of the families Mormyridae and Gymnarchidae, all of which possess aflagellate spermatozoa. Our data demonstrate that the spermatid differentiation and existence of the aflagellate spermatozoon are a unique phenomena not only among teleosts but also in the whole vertebrate lineage.