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Horseshoe crabs as potential sentinel species for coastal health: juvenile hemolymph quality and relationship to habitat conditions
As an interface between terrestrial and marine environments, coastal and estuarine areas are particularly prone to various pollution stresses. Identification of sentinel species is therefore essential to provide precautionary information on coastal health conditions. Given their significant ecological roles in estuarine ecosystems, horseshoe crabs are a potential species to indicate the general health status of coastal habitats. The present study demonstrated that the changes in hemolymph composition pattern of two Asian juvenile horseshoe crab species (Tachypleus tridentatus and Carcinoscorpius rotundicauda) are sensitive to reflect heavy metal (Pb, Ni and Fe) and nutrient (nitrate and ammonia) levels of intertidal sediments. In particular, a significantly negative correlation was found for the amebocyte viability and ratio of granular-spherical morphological state of amebocytes in juvenile hemolymph with nitrate and lead concentrations, respectively. There were also significantly higher concentrations of hemolymph hemocyanin and plasma protein in juvenile C. rotundicauda as compared to that in T. tridentatus on the same shore, possibly related to the difference in foraging habitats of these two horseshoe crab species. Such non-lethal sampling of hemolymph from juvenile horseshoe crabs can be useful for further development of monitoring program in assessing potential environmental impacts by anthropogenic activities.
MF17210 Accepted 11 November 2017
© CSIRO 2017