Morphometric, elemental and biochemical characterisation of three Haliclona species (demospongiae) from the Gulf of Mannar, India

Abstract

Marine sponges, in particular the Haliclona species (Demospongiae: Haplosclerida: Chalinidae) and/or their associated microorganisms, continue to yield an array of novel compounds. The aim of this work was the characterisation (morphometric, elemental and biochemical) of the three Haliclona species (Haliclona tenuiramosa, Haliclona cribricutis and Haliclona retiderma) from the Mandapam coast, Gulf of Mannar, India as an aid in the discrimination of the desired species for in vitro production of bioactive products and further ecobiotechnological applications. Diversity of the Haliclona species was analysed based on morphometric variables and elemental composition of the pinacoderm (outer epithelioid layer). Scanning electron microscope equipped with energy dispersive X-ray analysis did not reveal any change in elemental composition in spicules; however, the percentage of elemental composition in pinacoderm was significantly different among the species. The order and range of pinacoderm elemental composition were chlorine (36-51%), sodium (29-43%), silicon (0.72-2.2%), iron (0.46-0.73%). Aluminium (1.86-8.88%), calcium (0.92-16.19%) and sulfur (0.44-9.74%) varied greatly among the species. Total carbohydrate, protein and lipid contents also showed diversity among the species, i.e., carbohydrate content was high in H. tenuiramosa; proteins in H. cribricutis and lipids in H. retiderma, respectively. The order of ratio of spicule/protein content among the species were H. retiderma > H. cribricutis > H. tenuiramosa. The current approaches and results could direct an efficient application of discriminating sponge species in situ.