What does the freshwater clam, Corbicula largillierti, have to tell us about chlorothalonil effects?

Chlorothalonil (CLT) is a broad spectrum, and non-systemic fungicide applied in foliar structures to prevent and treat pathogens. This compound reaches to aquatic environments and affects the biota. In this context, the main goal of this study was to assess the effects of CLT at biochemical, tissular, and individual levels of biological organization using the invasive bivalve Corbicula largillierti as a bioindicator species. Clams were exposed to different sublethal concentrations (0, 10, 20 and 50 µg. L-1 CLT) for 96 h. At biochemical level, the enzymatic activity (Glutathione-s-Transferase, Catalase, Acetyl-, Butiryl- and Carboxyl-esterases) and lipid peroxidation were measured in gills and the visceral mass. Also, the digestive gland morphometry through quantitative histological indexes was registered at the tissular level. Finally, filtering activity and burial behavior at the individual level were measured. At the highest CLT concentration, the most significant changes were observed in enzymatic activity (except for butyrylcholinesterase), lipid peroxidation and in digestive gland morphometry. It was also registered increases of the filtering activity and the latency time to burial. Most of the biomarkers assessed showed significant responses under CLT exposure. Therefore, taking into account that C. largillierti was affected by CLT, it can be expected that other species could be in a potential risk if this fungicide is present in freshwater systems.

A multilevel response approach reveals the Asian clam Corbicula largillierti as a mirror of aquatic pollution.

The endobenthic bivalves are widely used as a bioindicators since they inhabit the sediment-water interface and are able to accumulate a different kind of contaminants. In the present work, we evaluated wild Corbicula largillierti (Phillippi, 1844) as a bioindicator of water quality in the central region of Argentina. The responses at different levels of the biological organization were used. We measured organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) levels in water and clams tissues. The biomarkers selected were enzymatic activities (Glutathione S-Transferase, Catalase, Acetyl-, Butyryl-cholinesterase, and Carboxylesterase) morphometry of the digestive gland, condition index and morphology of valves. In order to integrate all the responses a multivariate analysis and integrated stress index were applied. Our results showed the presence of contaminants along the studied river and the ability of C. largillierti to bioaccumulate them. All the biomarkers selected varied according to the water quality gradient, although there was no specific correlation with OCPs and PCBs levels. At the most polluted sites, the detoxification and oxidative stress enzymes, the morphometric analysis of the digestive gland and the variation in the morphology of the valves indicated the water quality degradation. The multivariate analyses allowed to discriminate the sites according to the different biomarker responses. The IBR index also showed a variation pattern according to the environmental quality gradient along the basin. According to the responses shown by C. largillierti we suggest this species as an useful bioindicator of aquatic pollution.

Effects of grazing on chemical soil properties and vegetation cover (case study: Kojour rangelands, Noushahr, Islamic Republic of Iran).

This research is conducted to study the effects of grazing on chemical soil properties and vegetation cover in three areas separated as the key, reference and critical areas. The study area is located at the river basin of Kojour in the Southwestern of Noushahr (in the North of IR-Iran). Sampling and collecting the soil and vegetation cover data from the site areas are accomplished in the first step of the research. The vegetation cover data was collected in 20 sample plots of 1 m2 in each area. The data was collected through a random- systematic method in the early grazing season. The soil data was collected out of two layers (0-10, 10-30 cm), in two time intervals before and after grazing. Five samples were selected per layer. Some edaphical factors such as organic carbon, percentage of soil organic matters, total nitrogen, absorbable phosphorus and potassium, pH and EC were measured. The results revealed that there is an inverse relationship between the grazing intensity and amount of carbon, nitrogen, soil organic matter and EC. However, a direct relation exists between the grazing intensity and amount of soil potassium, phosphorus, pH and the ratio of carbon to nitrogen. Vegetation in class 1 and 2 which were cereals and forbs had greatest percentage in the reference area. Furthermore, the percentage forage cover increases with the grazing intensity. The more unpalatable vegetation of class 3 forms the prevailing coverage in the critical area. The conclusion of this study shows that overgrazing is considered as a threat for the nutritional elements of soil and vegetation cover.

A fatty acid-binding protein and a protein disulphide isomerase-related protein expressed in urochordate gonad cytosol.

Despite the evolutionary-tree data suggesting that gene duplication leading to the divergence of the three branches which heart, liver and intestinal fatty acid-binding proteins belong to must have occurred before the vertebrate/invertebrate split, only the heart fatty acid-binding protein has been reported for invertebrates. In an attempt to shed light on this apparent inconsistency the presence of the other two branch members was investigated in the Urochordata Molgula pedunculata, an ascidian species close to vertebrates. The mantle-, gonad- and digestive tube-cytosolic fractions, obtained by centrifugation at 106,000 g, were incubated separately with [1-(14)C]palmitic acid and then fractionated on a Sephadex G-75 column. In the case of gonads and digestive tube, radioactive peaks corresponding to a molecular mass of 14-16 kDa, characteristic of fatty acid-binding proteins, were detected. When the experiment was performed on the mantle, this peak showing fatty acid binding capacity was absent. Western Blot of the radioactive 14-16 kDa Sephadex fraction from the urochordate gonad cross-reacted with rat liver fatty acid-binding protein anti-serum but did not do so with anti-rat intestinal, adipocyte or heart fatty acid-binding protein antisera. The material from the digestive tube was not recognized by any of the antisera. The most abundant protein in said 14-16 kDa fraction was a protein disulphide isomerase-related protein. Its partial amino acid sequence was determined.

Indole alkaloids from the tunicate Aplidium meridianum.

Five new indole alkaloids, meridianins A-E (1-5), have been isolated from the tunicate Aplidium meridianum, which was collected at a depth of 100 m near the South Georgia Islands, and their structures were elucidated by spectroscopic techniques. Compounds 2-5 showed cytotoxicity toward murine tumor cell lines.