Mitochondrial ATPase in the gills of the shore crabCarcinus maenas

The crab Carcinus maenas as a suitable experimental model in ecotoxicology

Aquatic ecotoxicology broadly focuses on how aquatic organisms interact with pollutants in their environment in order to determine environmental hazard and potential risks to humans. Research has produced increasing evidence on the pivotal role of aquatic invertebrates in the assessment of the impact of pollutants on the environment. Its potential use to replace fish bioassays, which offers ethical advantages, has already been widely studied. Nevertheless, the selection of adequate invertebrate experimental models, appropriate experimental designs and bioassays, as well as the control of potential confounding factors in toxicity testing are of major importance to obtain scientifically valid results. Therefore, the present study reviews more than four decades of published research papers in which the Green crab Carcinus maenas was used as an experimental test organism. In general, the surveyed literature indicates that C. maenas is sensitive to a wide range of aquatic pollutants and that its biological responses are linked to exposure concentrations or doses. Current scientific knowledge regarding the biology and ecology of C. maenas and the extensive studies on toxicology found for the present review recognise the Green crab as a reliable estuarine/marine model for routine testing in ecotoxicology research and environmental quality assessment, especially in what concerns the application of the biomarker approach. Data gathered provide valuable information for the selection of adequate and trustworthy bioassays to be used in C. maenas toxicity testing. Since the final expression of high quality testing is a reliable outcome, the present review recommends gender, size and morphotype separation in C. maenas experimental designs and data evaluation. Moreover, the organisms' nutritional status should be taken into account, especially in long-term studies. Studies should also consider the crabs' resilience when facing historical and concurrent contamination. Finally, experimental temperature and salinity should be harmonised so as to obtain reliable comparisons between different studies. Concerning future reaserch areas, data gathered in the present review reveals that in vitro assays derived from C. maenas are still lacking. Also, a complete C. maenas genome sequencing programme will be essencial for cutting-edge reseach.

Tributyltin inhibits the oligomycin-sensitive Mg-ATPase activity in Mytilus galloprovincialis digestive gland mitochondria

Tributyltin (TBT), widely employed in the past in antifouling paints, is one of the most toxic organic pollutants. Although recently banned, it still threatens coastal water ecosystems and accumulates in filter-feeding molluscs. TBT is known to act as a membrane-active toxicant; however data on mussels are scanty and exposure effects on mitochondrial ATPase activities remain hitherto unexplored. TBT effects on the mitochondrial Mg-ATPase activities in the digestive gland of Mytilus galloprovincialis were investigated both in vitro and in TBT-exposed mussels. Both an oligomycin-sensitive Mg-ATPase (OS Mg-ATPase) (70% of total Mg-ATPase activity) and an oligomycin-insensitive ATPase (OI Mg-ATPase) (30%) were found. The OS-Mg-ATPase was as much as 70% in vitro inhibited by 0.7 μM (203 μg/L) TBT, while higher concentrations promoted a partial inhibition release up to 5.0 μM TBT; higher than 10.0 μM TBT concentrations yielded nearly complete enzyme inhibition. Concentrations higher than 1 μM TBT enhanced the OI Mg-ATPase. Mussels exposed to 0.5 and 1.0 μg/L TBT in aquaria showed a 30% depressed OS Mg-ATPase activity, irrespective of TBT dose and exposure time (24 and 120 h). The OI Mg-ATPase activity was apparently refractory to TBT exposure and halved both in control and TBT-exposed mussels after 120 h exposure.

Gill Na+, K+-ATPase in a series of hyper-regulating gammarid amphipods. Enzyme characterisation and the effects of salinity acclimation

The enzyme Na(+), K(+)-ATPase was investigated in the gills of selected hyper-regulating gammarid amphipods. Gill Na(+), K(+)-ATPase was characterised with respect to the main cation and co-factor concentrations for the freshwater amphipod Gammarus pulex. The optimum cation and co-factor concentrations for maximal gill Na(+), K(+)-ATPase activity in G. pulex were 100mM Na(+), 15mM K(+), 15mM Mg(2+) and 5mM ATP, at pH 7.2. The effects of salinity acclimation on gill Na(+), K(+)-ATPase activity and haemolymph sodium concentrations was investigated in selected gammarid amphipods from different salinity environments. Maximal enzyme activity occurred in all gammarids when acclimated to the most dilute media. This maximal activity coincided with the largest sodium gradient between the haemolymph and the external media. As the haemolymph/medium sodium gradient decreased, a concomitant reduction in gill Na(+), K(+)-ATPase activity occurred. This implicates the involvement of gill Na(+), K(+)-ATPase in the active uptake of sodium from dilute media in hyper-regulating gammarids.

Branchial carbonic anhydrase (CA) of gills of Chasmagnathus granulata (Crustacea Decapoda)

The occurrence, localization and response to environmental salinity of carbonic anhydrase (CA) activity were studied in all of the gills of the euryhaline crab Chasmagnathus granulata from Mar Chiquita coastal lagoon (Buenos Aires Province, Argentina). CA activity in all gills appeared to be dependent on salinity. The pattern of distribution of CA activity among gills was different upon transition of C. granulata from osmoionoconformity (more uniform distribution) to hyperregulation (highest activity in posterior gills 6-8). Upon abrupt salinity change a differential response of CA activity occurred among gills which could suggest a differential role of CA in ion transport process in different gills of this crab. Furthermore, CA activity in anterior and posterior gills was found in cytosolic and microsomal fractions, although highest activity appeared to be membrane-associated. Both pools of CA were also strongly influenced by salinity and very sensitive to sulfonamide acetazolamide. The results suggest a differential participation of branchial CA in ionoregulatory mechanisms of C. granulata.