Modeling lead bioavailability and bioaccumulation by Lumbriculus variegatus using artificial particles. Potential use in chemical remediation processes

Artificial particles, specifically a diverse selection of chromatographical resins, have been recommended and used as a useful experimental model to predict the bioavailability and bioaccumulation of sediment-bound organic chemicals. In this work the same experimental model was adopted to investigate the bioavailability and bioaccumulation of lead by the freshwater oligochaete Lumbriculus variegatus. Particle-water partition coefficients were also determined. Sand particles and the anionic exchange resin promoted a similar uptake and bioaccumulation of lead. Instead, in the presence of the cationic exchanger the metal was not detected in the animals. For neutral particles, the uptake and accumulation depended on the chemistry of the functional groups at the active sites. In addition, a significant negative correlation was found between bioaccumulation and the particle-water partition coefficients. These studies may help to develop alternative methods for chemical remediation of lead-contaminated aquatic systems.     

Structural and functional heterogeneity of hemocyanin: intra- and inter-specific comparison in four species of portunid crabs (Crustacea: Portunidae)

This work is focused on hemocyanin (Hc) heterogeneity at population level and on the biochemical characterization of the different subunit patterns. Two different approaches have been used: we have characterized Hc subunit composition to describe the subunit polymorphism. Then, we have measured the Hc oxygen-binding affinity to disclose the physiological implications of such heterogeneity. In order to evaluate the intra- and inter-specific variability, different populations of Liocarcinus depurator, Liocarcinus marmoreus, Liocarcinus holsatus, Necora puber (Crustacea: Portunidae), from British Isles and Adriatic Sea, have been sampled. Results indicate that Hc polymorphism normally occurs at both intra- and inter-specific levels and involves the protein subunit type. These evidences extend to the portunid Hc the concept of molecular heterogeneity within species that have been previously reported for other decapod and amphipod crustaceans. Besides, the results support the view that subunit composition of crustacean Hcs is almost species-specific, but also that closely related species share a common pattern. Furthermore, this heterogeneity corresponds to different stability of the native oligomers quaternary structure and different oxygen affinity. The results are discussed in relation with the environmental regimes that characterize the different sampling areas. In addition to Hc, the hemolymph collected in specimens from different sampling areas contained also a non-respiratory pseudo-Hc. This paper reports for the first time the occurrence of pseudo-Hc at the level of population. Declaration: All the experiments comply with the current laws of Italy.     

Adaptations to semi-terrestrial life in embryos of East African mangrove crabs: a comparative approach

In this experimental study, we compared the embryonic respiration rate in air and water of six East African sesarmid species with intertidal, supratidal and arboreal habits, to highlight possible adaptations in embryonic metabolism to their different lifestyles. The embryos of all analysed crabs showed bimodal respiration, but we did not find a trend towards an enhanced embryonic oxygen uptake in air from the intertidal to the arboreal and supratidal species. However, the late-stage embryos of the most land-adapted species, Chiromantes spp., showed an enhanced metabolism when immersed in sea water that we interpreted as an adaptive recovery mechanism to cope with the storage of by-products due to marine-based metabolic pathways during long emersion periods. Thus, we showed that the embryos of land-adapted species, although still strongly water dependent, are well adapted to semi-terrestrial habitats and represent a minor limiting factor for females, which are not restricted in their emersion period by the oxygen requirements of their embryos.