Formation of flagella during interphase in secondary spermatocytes from Xenopus laevis in vitro

In cell culture, single motile flagella, 1 micron in length, were observed to grow from secondary spermatocytes of Xenopus laevis within 2-3 hours after telophase I, at 22 degrees C. About 90% of the secondary spermatocytes formed flagella as observed by phase-contrast microscopy. The flagella grew up to 2-6 microns in length during interphase II, which lasted about 18 hours. The presence of the "9 + 2" microtubular structure of the flagellar axonemes of secondary spermatocytes was confirmed by electron microscopy. When chromosomal condensation began (prophase II), the flagella were resorbed into the cells and, after the second meiotic division, a flagellum was formed again by each of the round spermatids. Thus, there appears to be a close relationship between the meiotic division cycle and the formation of flagella. The possible contribution of Sertoli cells to the formation of flagella in secondary spermatocytes was examined by reducing the number of Sertoli cells to less than ten per culture. Under these conditions, flagella formed in secondary spermatocytes with very high efficiency. It is very likely that secondary spermatocytes form flagella in vivo, since the secondary spermatocytes were observed to have flagella immediately after dissociation of the testes.     

Technical difficulties and solutions of direct transesterification process of microbial oil for biodiesel synthesis

Microbial oils are considered as alternative to vegetable oils or animal fats as biodiesel feedstock. Microalgae and oleaginous yeast are the main candidates of microbial oil producers’ community. However, biodiesel synthesis from these sources is associated with high cost and process complexity. The traditional transesterification method includes several steps such as biomass drying, cell disruption, oil extraction and solvent recovery. Therefore, direct transesterification or in situ transesterification, which combines all the steps in a single reactor, has been suggested to make the process cost effective. Nevertheless, the process is not applicable for large-scale biodiesel production having some difficulties such as high water content of biomass that makes the reaction rate slower and hurdles of cell disruption makes the efficiency of oil extraction lower. Additionally, it requires high heating energy in the solvent extraction and recovery stage. To resolve these difficulties, this review suggests the application of antimicrobial peptides and high electric fields to foster the microbial cell wall disruption.     

Intraspecific divergence in the lateral line system in the nine-spined stickleback (Pungitius pungitius)

The mechanosensory lateral line system of fishes is an important organ system conveying information crucial to individual fitness. Yet, our knowledge of lateral line diversity is almost exclusively based on interspecific studies, whereas intraspecific variability and possible population divergence have remained largely unexplored. We investigated lateral line system variability in four marine and five pond populations of nine-spined stickleback (Pungitius pungitius). We found significant differences in neuromast number between pond and marine fish. In particular, three of seventeen lateral line regions (viz. caudal peduncle superficial neuromasts; canal neuromasts from the anterior trunk and caudal peduncle) showed strong divergence between habitats. Similar results were obtained with laboratory-reared individuals from a subset of populations, suggesting that the patterns found in nature likely have a genetic basis. Interestingly, we also found habitat-dependent population divergence in neuromast variability, with pond populations showing greater heterogeneity than marine populations, although only in wild-caught fish. A comparison of neutral genetic (F(ST)) and phenotypic (P(ST)) differentiation suggested that natural selection is likely associated with habitat-dependent divergence in neuromast counts. Hence, the results align with the conclusion that the mechanosensory lateral line system divergence among marine and pond nine-spined sticklebacks is adaptive.     

Fishes of the southeastern Brazil Atlantic Forest

The largest preserved areas of Atlantic Forest are located in the southeastern region of Brazil. Estuaries, mangroves, rivers and streams are home to a community of fish that is still poorly understood. The composition of fish species and their relationships with environmental conditions were used to identify homogeneous areas within a landscape of 33,000 km². A total of 6,542 specimens, representing 124 species and 13 orders of bony fishes were collected at 102 sampling stations. Resulting scores from a canonical correspondence analysis applied to biological and environmental data were used in a cluster analysis to identify fish species with similar spatial distributions and localities with similar fish fauna and abiotic conditions. Five micro-regions were identified, with homogeneous compositions of species, allowing better planning of conservation of aquatic biodiversity. Despite a high degree of preservation, impacts due to deforestation, drainage of wetlands and overfishing were detected, as well as the introduction of 41 exotic species.     

Prospects for fen meadow restoration on severely degraded fens

The majority of fens in Europe have been transformed for agricultural purposes and have disappeared or become degraded. Fen meadows that developed under low-intensity management of fens also have become degraded. In this paper, we consider the available restoration methods, biotic constraints for restoration and new prospects and approaches for the restoration of severely degraded fens. Due to irreversible changes in landscape settings, hydrology, soil and trophic conditions, a full restoration to natural mires is unlikely. Yet, an improvement of the ecosystem functions and revival of biodiversity in degraded fens is possible. A restoration of semi-natural meadows is one of the alternative targets. Important for restoration efforts to succeed are a sufficient reduction of nutrient levels and preventing acidification. In general, a combination of topsoil removal and seed transfer is an effective measure for fen meadow restoration, provided that groundwater seepage can be re-established. There are also several biotic limitations to fen meadow restoration, due to limited propagule availability of target species and the legacy of the former vegetation in form of its soil seed bank and high seed production by unwanted species. Under the present environmental conditions, the re-development of fen meadows on degraded fens will result in species compositions different from those observed in the past and such restoration may require considerable time and effort.