A scanning electron microscope study of normal and vitrified leaves from Datura insignis plantlets cultured in vitro

The surface anatomy of normal and vitreous leaves of plantlets obtained from Datura insignis Barb Rodr nodal segment cultures was compared using scanning electron microscopy. Normal and vitrified leaves are similar in several ways. They are both amphistomatic, and have similar distributions of glandular and non-glandular trichomes. Stomata have similar length, diameter and distribution in normal and vitreous plants. Immature stomata, which have closed pores, and plugged stomata, which contain an amorphous material between their guard cells, occur in both normal and vitrified leaves. Normal and vitreous leaves differ in the frequency of normal and abnormal stomata. Normal stomata have kidney-shaped guard cells and resemble closely those found in field-grown plants, whereas abnormal stomata have deformed guard cells. Normal stomata represent approximately 80% of the total number of stomata in normal leaves, but only 7% of the total number of stomata in vitreous leaves. Abnormal stomata represent 90% of the total number in vitreous leaves. The deformation of guard cells could possibly be a mechanical impediment to stomatal function.     

Culture of Hypnea musciformis (Rhodophyta,Gigartinales) on artificial substrates attached to linear ropes

Hypnea musciformis is the only species so far exploited in Brazil as raw material for the production of k-carrageenan. Due to the erratic production in space and time, increasing harvest and transportation costs, experiments have been performed in order to assess the viability of H. musciformis mariculture.In nature the species occurs as an epiphyte, and so mariculture using artificial substrates that simulated the natural host of the species was tried. These substrates were attached, at regular intervals, to linear ropes. In the sea, these ropes were stretched between cement blocks.Seeding occurs naturally, by means of spores, or detached pieces of H. musciformis scattered in the water column that get entangled on the ropes. The best yields (0.54 wet kg m^–1 month^–1) were obtained with unthreaded rope substrates maintained in a vertical position by small rafts. Production is highest in the first 18 m off the rocky shore (0–2.1 m deep), at the highest substrate density utilized (10 m^–1), 2–3 months after installing the ropes in seawater. The main factor controlling seasonal production is water movement.     

Life history and reproductive potential of the agarophyte Gelidium robustum in California

The reproductive potential of the tetrasporangial phase of Gelidium robustum was studied for 16 months at two sites off Santa Barbara, California. In all samples tetrasporangial thalli were always more abundant than gametangial ones. Tetratrasporangial sori were present throughout the duration of the study but relative fecundity was highest [300–400 sori g^–1 (w. wt)] in spring/summer samples of consecutive years, as a result of increasing numbers both of tetrasporangial branchlets per plant and of sori per branchlet. On the other hand, laboratory experiments showed that tetraspore release per sorus was highest (150–250 spores sorus^–1 d^–1) in winter. Inferring from these field and laboratory data plants released up to ± 34 000 tetraspores g^–1 (w. wt) d^–1 in the spring/summer of the second study year. Tetraspore germination, under defined culture conditions, also showed a marked seasonality increasing sharply from less than 10% in winter up to almost 60% in spring/summer, thus coinciding with the period of maximal spore output per plant. These results suggest that although relatively high numbers of tetraspores may be released by G. robustum plants all year round these might not always have the potential to germinate and recruit.     

Abundance of airborne Penicillium CFU in relation to urbanization in Mexico City.

Air was sampled simultaneously at three localities in Mexico City differing in urbanization index and air pollution level on 22 days during a period covering both dry and rainy seasons. An Andersen two-stage microbial sampler was used for 15 min at 28 liters min-1 to isolate culturable fungi on malt extract agar. After exposure, plates were incubated at 25 degrees C for 48 to 72 h before colonies were counted and identified to give concentrations of total fungal spores and of Penicillium spp., expressed as CFU per cubic meter of air. Total fungi numbered 91 to 602 CFU m-3 in Tlalpan Borough (southern area), 40 to 264 CFU m-3 in Cuauhtémoc Borough (downtown), and 26 to 495 CFU m-3 in Gustavo A. Madero Borough (northern area). Although Penicillium spp. were the second most frequently isolated fungal genus, concentrations were small, with a maximum of only 133 CFU m-3. Twice as many colonies were isolated in the southern area, with an urbanization index of 0.25 (arithmetic mean, 41 CFU m-3), as at other sampling stations with greater urbanization indices (arithmetic means, 19 and 20 CFU m-3). In the downtown area, with an urbanization index of 1.0, Penicillium spp. were more numerous than any other genus and formed 25% of the total fungal count compared with 14 and 17% in the other areas. Concentrations of airborne Penicillium spp. did not differ significantly between rainy and dry seasons.(ABSTRACT TRUNCATED AT 250 WORDS)     

Immunocytochemical localization of DNA in synaptonemal complexes of rat and mouse spermatocytes,and of chick oocytes

The distribution of DNA in synaptonemal complexes of rat and mouse spermatocytes, and of chick oocytes was investigated by immunogold electron microscopy. Except for a few specific sites, DNA was not immunolocalized in the space between lateral elements of the complex. Some labeled fibrils connecting the lateral elements with the central element were observed associated with recombination nodules or near them. However, other labeled fibrils in the space between lateral elements did not appear to present any relationship to recombination nodules. The immunocytochemical approaches used here confirmed the presence of significant amounts of DNA in the lateral elements as previously indicated by preferential DNA staining methods. Furthermore, our findings support the view that recombination nodules are the site of chiasma formation.     

Towards an ethical and legal framework in archeogenomics: A local case in the Atlantic coast of central Patagonia

Ethical discussions around ancient DNA (aDNA) research predate the technological breakthroughs that led to the accelerated generation of ancient genomic data, revealing a long-due need to address these aspects in the field. Given the diverse conflicts that genomics has raised towards the communities associated with the Non-living Human Ancestors under study, it has been suggested that the ethical and legal implications of genetically studying present-day and ancient human populations should be considered case-by-case. Nevertheless, the discussions have focused on US and European perspectives. To contribute from a local and Latin American position to the problem, we present the history of consensus and disagreement of the relationships between scientists and Indigenous communities of the Atlantic coast of the central Argentinian Patagonia. We describe how these relationships resulted in the approval of a groundbreaking provincial law that acknowledges the Indigenous community's right to be involved in decision-making concerning their Ancestors. In addition, we emphasize how these established relationships allowed the development of aDNA studies. With this background, we address the main ethical concerns of genomic studies of Ancestors identified in the reference literature and commit to applying some of the recommendations suggested in those ethical guidelines. Then, we reflect on possible negative consequences of ongoing research and propose some suggestions based on personal experiences that will contribute to moving the ethical field towards a more contextualized science with a local perspective.     

Acoustic communities in an environmental gradient from native to urban areas in Central Brazil

As urban areas expand due to increasing human populations, natural habitats are diminishing in quantity and quality. We conducted a study to examine the response of diurnal acoustic communities along a gradient of environments, ranging from native to dense urban areas. We hypothesized that acoustic indices would decline with urbanization, transitioning from natural and rural areas to urban environments. We conducted the research in and around Brasília, Central Brazil. We deployed 24 digital recorders in native, rural, low-density and high-density urban areas. We employed five commonly used acoustic indices (ADI, ACI, NDSI, H and BI) to characterize the acoustic communities and represent the existing biodiversity numerically. We initially compared the index values across different land use types using a non-parametric rank sum test. Subsequently, we selected eight landscape metrics and performed a principal component analysis to summarize the surrounding matrix at each sampling point. We then employed generalized linear models to determine if the acoustic indices exhibited the anticipated variations. The results indicated significant variations in all indices among the different land use types, indicating their responsiveness to distinct acoustic communities and environmental characteristics. ADI, H and NDSI exhibited declining values from native to urban areas, while ACI and BI displayed the opposite trend. These findings underscore the influence of landscape structure on acoustic indices. Consequently, we concluded that adopting appropriate landscape planning, mainly through integrating natural and urban areas, could help preserve biodiversity in tropical urban regions.     

Trophic ecology of juvenile bull sharks (Carcharhinus leucas) in the Coyote estuary,Costa Rica

Bull shark (Carcharhinus leucas) is a near-threatened elasmobranch species capable of moving between the fresh and salty waters of tropical and subtropical coastal areas, for which we still lack important ecological information. During their first years of life, bull sharks use estuarine systems as nursery areas, making them highly susceptible to environmental and anthropogenic pressures. We studied the trophic ecology of juveniles found in the Coyote estuary, a potential nursery area in Costa Rica, to understand the potential impact of further bull shark declines and gain knowledge that could aid in their conservation. We analysed the trophic ecology of juvenile bull sharks [81–103 cm total length (TL)] in the Coyote estuary, Costa Rica, using stable isotopes of δ¹⁵N and δ¹³C. Since one problem using this technique in juveniles is the confounding effect of the maternal signature, we sampled different tissues (muscle and plasma), verified the status of the shark's umbilical scar and identified the size at which the isotope signature is a result of the animal's current diet. The isotopic values of the muscle tissue reflected the maternal isotopic signature. In contrast, plasma values reflected the diet of juvenile bull sharks >95 cm TL and with a closed umbilical scar. Juvenile bull sharks fed primarily on teleost fishes of the order Anguilliformes and Siluriformes, and have a high trophic position (≥4.0) in the Coyote estuary. Our findings suggest that this estuary is an important feeding site for juvenile bull sharks of the Pacific of Costa Rica. Thus, the protection of essential habitats such as the Coyote estuary will benefit not only bull shark conservation, but also the conservation of an array of fish species that also use this habitat as a rookery, many of which are of commercial interest.