Cláudia T. Callil

Variação temporal de larvas de Chironomidae (Diptera) no Alto Rio Paraguai (Cáceres, Mato Grosso, Brasil)

The aim of this study is to determine the influence of environmental variables on the time distribution of assemblages of Chironomidae in the Upper Paraguay River. The samples were collected from November 2004 to October of 2005. To consider the diversity of habitats in the region, nine different sampling points were sampled and 2988 individuals were collected, distributed in 34 species, eight tribes and three subfamilies. The genus Labrundinia sp.1, Polypedilum (Asheum) and Polypedilum (Tripodura) occurred almost every month during the study. Richness and abundance were higher during the dry period of the year, and the genus Polypedilum was the most abundant. There was evident the effect of the environmental variables on the attributes of diversity in the Upper Paraguay River.

Bivalve distribution in hydrographic regions in South America: historical overview and conservation

Based on literature review and malacological collections, 168 native freshwater bivalve and five invasive species have been recorded for 52 hydrographic regions in South America. The higher species richness has been detected in the South Atlantic, Uruguay, Paraguay, and Amazon Brazilian hydrographic regions. Presence or absence data were analysed by Principal Coordinate for Phylogeny-Weighted. The lineage Veneroida was more representative in hydrographic regions that are poorer in species and located West of South America. The Mycetopodidae and Hyriidae lineages were predominant in regions that are richest in species toward the East of the continent. The distribution of invasive species Limnoperna fortunei is not related to species richness in different hydrographic regions there. The species richness and its distribution patterns are closely associated with the geological history of the continent. The hydrographic regions present distinct phylogenetic and species composition regardless of the level of richness. Therefore, not only should the richness be considered to be a criterion for prioritizing areas for conservation, but also the phylogenetic diversity of communities engaged in services and functional aspects relevant to ecosystem maintenance. A plan to the management of this fauna according to particular ecological characteristics and human uses of hydrographic regions is needed.

Ultrastructural analysis of the shells of Anodontites trapesialis (Lamarck) and Anodontites elongatus (Swaison) (Mollusca, Bivalvia, Etherioidea) from the Mato Grosso Pantanal Region, Brazil

Based on optical and SEM microscopic observations, the projections of the outer surface of the periostracum and inner micro-structures of the shell are described and redefined. The outer surface of the periostracum is practically smooth in both species. Considering a mesoscopic view of the periostracum, A. trapesialis (Lamarck, 1819) presents regular corrugations in the form of radial sequences of arches on the disk region, isolated rays or horizontal sequences of rays on the anterior lower region. A. elongatus presents corrugations formed by series of oblique arches on the disc and oblique rays on the carina. Under SEM, micro ridges were more evident in A. elongatus, but a wide diversity of shapes and patterns of micro fringes were observed in A. trapesialis, especially in young individuals. Considering the profile of the shell layers, the periostracum is relatively thin and apparently simple in A. trapesialis and thinner in A. elongatus. The prismatic layer is thick in both species, consisting of a single series of elongated prisms and wedge-shaped prisms close to the outer surface. The nacreous layer consists of very fine lamellae without pattern or with a slight staircase-like; in A. elongatus this layer is divided by a laminar inclusion of conchiolin. The fringes are abundant and diversified in A. trapesialis, a species less resistant to desiccation due to the presence of a wide intervalvar gap. The existence of a greater density of micro fringes and spikes in juveniles may be related to the orientation of the animal in order to search for an ideal site for development or for escape from regions subject to seasonal droughts, like Pantanal.

Factors structuring the spatial distribution of Chironomidae larvae community in the floodplain of the northern Pantanal, Brazil

AIM: In order to identify the factors structuring the spatial distribution of the Chironomidae community, we analyzed the effects of water and sediment characteristics, flood duration and type of phytophysiognomic unit on the taxa composition of this community. METODOS: O estudo foi realizado em 26 parcelas do Sitio de Amostragem de Longa Duracao (SALD), localizado em uma area sazonalmente inundavel na parte norte do Pantanal (Brasil). The study was conducted at 26 plots of the Long-Term Sampling Site, located in a seasonally flooded area in northern Pantanal (Brazil). Sediment samples were taken from each plot to analyze the Chironomidae community, organic matter and particle size; limnological parameters (depth, water temperature, dissolved oxygen, electrical conductivity and pH); besides the duration of flood. RESULTS: We identified 432 individuals distributed into 21 Chironomidae taxa. Polypedilum and Ablabesmyia were the most frequent spatially. The multivariate multiple regression analysis showed that the community composition was significantly related to the flood duration and grain size characteristics, but not to phytophysiognomic units and limnological parameters. Plots with predominantly sandy substrate and flooded for a shorter time presented a greater occurrence of taxa. CONCLUSIONS: The gradient produced by the spatial distribution of sediment grain size and flood duration determined the distribution of Chironomidae taxa. Changes in the hydrological functioning of the Pantanal, such as those from reservoir construction in the uplands region and roads and dykes construction in the floodplain could then impact the local chironomid biodiversity.

Influence of the flood pulse on reproduction and growth of Anodontites trapesialis (Lamarck, 1819) (Bivalvia: Mycetopodidae) in the Pantanal wetland, Brazil

Abstract Determining how, when, and why energy allocation occurs based on different life history traits, provides core knowledge for understanding evolution, ecology, and conservation of populations. We assumed that, in seasonal environments, Anodontites trapesialis, a common freshwater mussel in the Pantanal wetland, has to time its maturation, its larvae incubation time, and adjusts its breeding strategy seasonally. From histological analyses of gametes, larval count, and marginal increment of the shell rings, we present information about phenology and growth strategies to investigate the influence of environment and reproductive period on growth. We determined for the first time, asymptotic maximum size and longevity for this mussel. This species is a functional hermaphrodite, with maturation and spawning starting at the end of the flood period, when the water begins to recede and fishes return to the main river channel. The larvae, lasidium in this case, disperse on host fishes at this time. As we predicted, the flood pulse is the main regulatory factor to the growth patterns and reproductive period establishment. The species’ life history traits are discussed in the context of life history theory as adaptive responses to the dynamic balance imposed by the seasonality of the Pantanal.