Invasional meltdown: an experimental test and a framework to distinguish synergistic,additive, and antagonistic effects

The potential role of positive interactions among co-invaders is at the core of the invasional meltdown hypothesis. The interaction of non-native species could result in an exacerbation of each other’s effects. Thus, the resulting effect of multiple non-native species on ecosystems can be greater than the sum of their individual effects. We designed an analytical framework and a set of mesocosm experiments to assess the potential synergistic effects of three non-native species (Limnoperna fortunei, Astronotus crassipinnis, and Hydrilla verticillata) in a highly invaded floodplain in southern Brazil. We analyzed ecosystem, community, and population attributes in scenarios with non-natives. Our hypothesis of a synergistic effect was not supported. Even though effects of the invasive species were detected for all ecological levels, evidence indicated that these effects were additive. In addition to adding to the statement that origin (i.e., native vs. non-native status) does matter, we provide a tool to differentiate additive, synergistic, and antagonistic effects in situations with multiple invasions, and experimentally demonstrate additive effects of non-native species at different ecological levels.

     

Influence of the macrophyte <Emphasis Type="Italic">Eichhornia azurea</Emphasis> on fish assemblage of the Upper Paraná River floodplain (Brazil)

The architecture of aquatic macrophytes adds structural complexity to the littoral region. This increased habitat heterogeneity prompts greater diversity and stability of biotic communities. However, there are few studies that explore the ecological role of macrophytes in the Neotropical region. Then, the aim of this study was to determine spatial and diel influence of near-shore Eichhornia azurea stands on fish assemblage attributes and structure, in the Upper Paraná River floodplain, considering a meso-habitat scale. To achieve this objective, fish were trapped in four stands of macrophytes, in three positions (middle and border of the stand and open area) with samplings taken at different times of the day (6 h, 12 h and 18 h). A total of 537 fish of 16 species were caught. Dissolved oxygen varied significantly among positions. Fish assemblage attributes (species richness, evenness and Shannon Diversity Index) also varied among positions. Fish assemblage structure (summarized by a detrended correspondence analysis) and size structure were strongly influenced by times of the day and positions. The patterns observed can be explained by factors such as oxygen concentration, food resource availability and predation, all influenced by macrophytes. We suggest that any strategy to manage fish diversity and fish stocks has to consider aquatic macrophytes.     

Raman spectroscopy of dorsal root ganglia from streptozotocin‐induced diabetic neuropathic rats submitted to photobiomodulation therapy

In this study, we used Raman spectroscopy as a new tool to investigate pathological conditions at the level of chemical bond alterations in biological tissues. Currently, there have been no reports on the spectroscopic alterations caused by diabetic neuropathy in the dorsal root ganglia (DRG). DRG are a target for the treatment of neuropathic pain, and the need for more effective therapies is increasing. Photobiomodulation therapy (PBMT) through infrared low‐level laser irradiation (904 nm) has shown analgesic effects on the treatment of neuropathy. Thus, the aim of this study was to use Raman spectroscopy to characterize the spectral DRG identities of streptozotocin (STZ)‐induced diabetic neuropathic (hyperalgesic) rats and to study the influence of PBMT over such spectra. Characteristic DRG peaks were identified at 2704, 2850, 2885, 2940, 3061 and 3160 cm^?1, whose assignments are CH₂/CH₃ symmetric/asymmetric stretches, and C─H vibrations of lipids and proteins. DRG from hyperalgesic rats showed an increased normalized intensity of 2704, 2850, 2885 and 3160 cm^?1. These same peaks had their normalized intensity reduced after PBMT treatment, accompanied by an anti‐hyperalgesic effect. Raman spectroscopy was able to diagnose spectral alterations in DRG of hyperalgesic rats and the PBMT reduced the intensity of hyperalgesia and the altered Raman spectra.     

Pseudotumoral presentation of chronic pulmonary paracoccidioidomycosis: Report of a case

A case of unilateral paracoccidioidal pulmonary lesion simulating a neoplasm is reported.This case was presented on the XVII World Congress on Diseases of the Chest, Amsterdam, The Netherland, June 1993.     

The influence of “Homage to Santa Rosalia” on aquatic ecology: a scientometric approach

In 1959, G.E. Hutchinson provided a general explanation for the diversity of species in his paper “Homage to Santa Rosalia or why are there so many kinds of animals?” To assess the contribution of the ideas Hutchinson introduced in “The Homage” to aquatic ecology research, we performed a bibliometric evaluation of all the articles that cited this paper between 1960 and 2009. The articles were retrieved using the database from Thomson Reuters (ISI Web of Knowledge) in March 2009. For each paper, we first identified the studied environment (terrestrial, marine or freshwater) and whether the study was theoretical or empirical. For marine and freshwater studies, we recorded the journal where the article was published, the year of publication, the number of citations, the taxonomic group (e.g. fish, phytoplankton, zooplankton, macroinvertebrates or macrophytes), the habitat (e.g. wetlands, lakes, rivers, streams or ocean) and the main ideas addressed. A total of 1345 articles cited “The Homage”, and the number of citations increased significantly with time. Most of the articles that cited “The Homage” described research carried out in a terrestrial environment or were theoretical, and a lesser number of citations came from freshwater and marine papers, which used mainly fish and invertebrates as model organisms. In the aquatic sciences, most of the papers discussed the influences of competition and energy (productivity) on diversity. Our results indicate that “The Homage” can still be considered a “citation classic” and a breakthrough contribution, and that it is still having a great impact on different fields of ecology, including limnology and marine ecology.     

Alternative reproductive tactics in atlantic salmon: factors affecting mature parr success

In Atlantic salmon, as in most salmonids, males can mature early in the life cycle, as small freshwater fish, termed parr, and/or undergo a sea migration before maturing as full-size adults. The alternative life histories are contingent on environmental and social circumstances, such as growth rate, territory quality or any other factor that affects the individual''s state. In order to model the choice of life history in this group of commercially valuable species, it is necessary to understand not only the relative contribution of the different male types to subsequent generations, but also to know the factors that affect reproductive success in each type. In this paper we present the results of a study designed to investigate the factors that affect the reproductive success of mature parr. We used highly polymorphic minisatellite DNA markers to analyse paternity in a series of mating experiments where the number and body size of parr were manipulated. The fraction of eggs fertilized by mature parr ranged from 26 to 40 per cent, with individual parr fertilizing up to 26 per cent of the eggs. A strong positive correlation was found between parr size and reproductive success. The relative success of parr decreased with increasing parr number. Data from this and other studies on variation in the timing and degree of parr reproductive success are discussed in relation to the evolution of male mating strategies and life history in salmonids.     

Effects of Desiccation and Sediment Type on Early Regeneration of Plant Fragments of Three Species of Aquatic Macrophytes

We tested the effects of desiccation and type of sediment (clay or sand) on the regeneration of fragments of the apical shoots of three species of Hydrocharitaceae: Egeria najas, E. densa and Hydrilla verticillata. The shoots were left to dry on clay or sand from zero to four days, and were then returned to aquaria containing water. To approximate natural conditions, the aquaria containing clay had higher turbidity and nutrient (P and N) concentrations than did the aquaria with sand. All species dried faster on sand substrate, which led to lower regeneration (in terms of dry weight, length, sprout and root formation) in this treatment. H. verticillata fragments elongated faster than the other species, but E. najas was the most successful species (in terms of increase in dry weight) in the sand treatment. Our results indicate that the exotic H. verticillata has a competitive advantage, at least in its early stages of regeneration, over the other two, native species, especially in more eutrophic and turbid habitats; whereas E. najas fragments have a competitive advantage in less‐turbid, oligotrophic and sand‐dominated sites. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Occurrence of Cryptosporidium (Apicomplexa,Cryptosporidiidae) in Crotalus durissus terrificus (Serpentes,Viperidae) in Brazil

The objective of the present study was to investigate the prevalence of Cryptosporidium (Apicomplexa, Cryptosporidiidae) in the snake Crotalus durissus terrificus (Serpentes, Viperidae). Fifty animals were evaluated for the presence of oocysts of Cryptosporidium sp. at the time of arrival and 30 and 60 days later. Intestinal washings with saline solution (1% body weight), fecal samples, and organ scrapings were collected during the study. Oocysts were concentrated by an ether-phosphate-buffered saline sedimentation technique and then separated by a density gradient centrifugation technique. Smears were made with the sediment and submitted to modified acid-fast and auramine-rhodamine staining. Cryptosporidium-positive smears were used as controls for the experimental findings. The overall prevalence of Cryptosporidium sp. oocysts was 14%. Among the positive snakes, oocysts were detected only in the intestinal washing in two specimens, only in the feces in four specimens, and in both materials at least once in one specimen. The positive snakes were predominantly from Santa Maria da Serra city State of S?o Paulo (57.1%). We also observed that all of the examinations that presented positive results were obtained at least 27 days after the capture of the animals.     

Spectral characteristics of a compound altering cytochrome P450 spectra from vertebrate microsomes suggest that it is a functional protein

A peak near 420 nm interfering with the spectral detection of cytochrome P450 has been reported for invertebrates and fish. It has been variously suggested to be a breakdown product of P450, or a hemoprotein with unknown functions. Similar spectra were observed in the present work with a neotropical fish, an amphibian, and rodents. Comparative analysis showed that difference spectra resulted from an unknown hemoprotein and neither from P420, nor from hemoglobin, that may contaminate animal microsomes. Seasonal appearance of this protein was observed and its spectrum described. This protein completely substituted P450 in spectra of liver microsomes of fish and rodents collected in the summer, while in the winter the same animals displayed either the classic P450 spectra (rodents) or those accompanied with the low-intensity 421-nm peak (fish). We suggest that the compound visualized in P450 spectra is a functional protein and not an artifact. The possibility that an unknown protein may substitute for cytochrome P450 in microsomes under certain environmental conditions and play a role in animal adaptation to unfavorable environmental fluctuations is discussed.     

Positive selection of the long-wavelength opsin gene in South American cichlid fishes

Hydrobiologia - Cichlid fishes use their vision for recognition of other fishes, feeding, and in habitat selection. Neotropical cichlids can be found in a range of different habitats differing in...