Calcimycocavitological studies on seashells from beaches of North Goa, India

Abstract

Calcimycocavitology deals with the study of hollowing out of spaces in hard calcareous seashells by the fungi called calcimycocavites. Endolithic fungi in the shells were first reported and named as the trace fossils in 1889 by Bornet and Flahault. Endolithic fungi bore inside the shell by the process of bioturbation by using organic acids (oxalic acid, citrate) and enzymes (proteases, dehydrogenases and oxidoreductases). Previous reports show the presence of tunnels formed by fungal hyphae in the shells. The present work reports preliminary results of calcimycocavitological studies on the seashells from beaches of north Goa, India. The calcareous sand samples were collected from Arambol, Ashvem, Morjim, Vagator, Anjuna, Baga and Miramar beaches by pool sampling method and were separated into different fractions by using standard sieves. Each fraction of sand was subjected to stereomicroscopic studies which revealed that the sand fraction between 150-250 ?m included irregular shell fragments showing positive colonization by calcimycocavites. Hydrochloric acid treatment was used to dissolve the shells and release calcimycocavites biomass which was stained with Congo Red and tentatively identified as distinct microfungal forms. SEM studies of the calcareous shell fragments revealed the microtunneling behavior of the fungi. Digital analysis of SEM images using Mountain premium 7.2 software revealed the fine topography of calcimycocavites hyphae along with unidentified presumptive biomineral encrustations. The ecological, biological and biogeochemical implications of the findings are presented with respect to possible role of calcimycocavites in Calcium and Carbon cycling by breakdown of the calcareous shells and release of inorganic and organic components in the ecosystem.