Feeding and morphological analysis of the digestive tract of four species of fish (Astyanax altiparanae, Parauchenipterus galeatus, Serrasalmus marginatus and Hoplias aff. malabaricus) from the upper Paraná River floodplain, Brazil

The present study is inspired by the great wealth of species exhibited by the ichthiofauna. Not only concepts and techniques of ecology deserve attention, but also knowledge in other biological areas, such as zoology and anatomy, are necessary. The intention of the present work is to discover the morphology of fish through the study of the digestive tract morphology, associating it to diet data, in order to better understand the biology of four fish species of the upper Paraná River floodplain. The samples were collected quarterly in the year 2000 with gillnets of different meshes. The stomach content was analyzed under a stereoscopic microscope and the frequencies of occurrence (FO) and volumetric (FV) and the alimentary index (IAi) were calculated. Various morphologic characteristics were analyzed and schematized using a light chamber. The species were grouped into two trophic guilds - insectivores (Astyanax altiparanae and Parauchenipterus galeatus) and piscivores (Serrasalmus marginatus and Hoplias aff. malabaricus). The first two, although consumers of insects, preyed on different alimentary groups, notably Hymenoptera in the case of A. altiparanae and Coleoptera in the case of P. galeatus. Serrasalmus marginatus and H. aff. malabaricus consumed mainly fishes. However, only pieces of prey were usually found in the stomach content of the first species, whereas whole fishes were found in the stomach content of the second. Astyanax altiparanae exhibited characteristics that allowed it to obtain food in several compartments of the water column. Similarly P. galeatus consumed food resources that were available in all aquatic compartments, although the abilities to capture, to manipulate and to absorb food differed, as shown by the importance of teeth plates and pharyngeal teeth. Serrasalmus marginatus and H. aff. malabaricus, although resembling each other in many aspects of the digestive tract morphology, differed in the strategies used to capture prey. The analysis showed that, according to the main food item of the diet, the species were grouped into two trophic guilds. However, those within the same category used different feeding methods, and similarity in items consumed does not imply the same group of morphological characteristics

L-selectin-negative CCR7(-) effector and memory CD8(+) T cells enter reactive lymph nodes and kill dendritic cells

T lymphocytes lacking the lymph node-homing receptors L-selectin and CCR7 do not migrate to lymph nodes in the steady state. Instead, we found here that lymph nodes draining sites of mature dendritic cells or adjuvant inoculation recruited L-selectin-negative CCR7- effector and memory CD8+ T cells. This recruitment required CXCR3 expression on T cells and occurred through high endothelial venules in concert with lumenal expression of the CXCR3 ligand CXCL9. In reactive lymph nodes, recruited T cells established stable interactions with and killed antigen-bearing dendritic cells, limiting the ability of these dendritic cells to activate naive CD4+ and CD8+ T cells. The inducible recruitment of blood-borne effector and memory T cells to lymph nodes may represent a mechanism for terminating primary and limiting secondary immune responses

Real-time imaging of the cellular interactions underlying tolerance, priming, and responses to infection

Much of what we understand about the anatomy and architecture of the immune system was revealed through exquisite experiments performed in the 1950s–1970s. These studies identified the role that anatomy played in a number of fundamental immunological phenomena including recirculation, induction of immune priming or tolerance, and the interactions of T and B cells. The recent resurgence of interest in the role of immune architecture and anatomy in basic immunological phenomena is almost entirely due to technological developments in identifying and tracking cells in vivo, not least through the ability to do this dynamically, in real time through the application of multiphoton microscopy. Here we outline the background to our own studies applying multiphoton microscopy to analysis of immune priming and tolerance, the role of adjuvants, T‐ and B‐cell interactions, and the application of these studies in infectious and inflammatory diseases. We then describe the impact that real time in vivo imaging has had on these areas. Finally, we engage in some ‘crystal ball gazing’ to look at what developments in imaging are likely to occur, why they are important, and what further information these approaches may distill regarding the development of the immune response

Biological aspects of Schizodon nasutus Kner, 1858 (Characiformes, Anostomidae) in the low Sorocaba river basin, São Paulo state, Brazil

Four biological aspects of Schizodon nasutus in the low Sorocaba river basin, São Paulo, Brazil were analysed. These were accomplished during the year seasons. The fish diet and the feeding activity were investigated by studying the repletion index, which showed no significant differences between seasons. The food items analysed by frequency of occurrence and dominance showed a predominance of vegetable items in the diet. The reproduction, analysed by using the gonadosomatic index, indicated that the reproductive period occurs during the summer period when temperatures are higher and rainfalls are more intense. The amount of accumulated fat and condition factor varied according to reproduction, especially for females

Plasticity in the diet of Astyanax taeniatus in a coastal stream from south-east Brazil

In this work we aimed to characterise the diet of Astyanax taeniatus (Jenyns 1842) (Characiformes, Characidae) along the Mato Grosso stream and we hypothesised that the diet of this species would vary according to spatial, seasonal and ontogenetic differences. Specimens were collected every second month at three sites with different physical attributes. The feeding habits of 651 specimens were analysed using the Alimentary Index (IAi). Analysis of the diet showed an effect of spatial, temporal and ontogenetic factors. Vegetal allochthonous items were more important in the diet of Astyanax taeniatus in upstream sites while animal autochthonous items were more important downstream. Ontogenetic differences in the diet were significant only in upstream sites, where adults consumed a greater amount of vegetal matter than juveniles. These results reinforce the idea that Astyanax species are opportunistic and show trophic plasticity