PINE STRUCTURE OF THE PODIA IN 3 SPECIES OF PAXILLOSID ASTEROIDS OF THE GENUS LUIDIA (ECHINODERMATA)

Individuals of the paxillosid asteroid genus Luidia use their podia in locomotion and burrowing. Each podium in the three considered species consists of a stem with a pointed knob at its tip. The knob consists of four tissue layers that are, from the inside to the outside, a meso thelium, a connective tissue layer, a nerve plexus, and an epidermis. The latter is made up of four cell categories : secretory cells, neuro secretory cells, non-secretory ciliated cells, and support cells. The epidermal cells of the podial knob are presumably functioning as a duo -gland adhesive system in which adhesive secretions would be produced by secretory cells while de-adhesion, on the other hand, would be due to neurosecretory cell secretions. Although the podia of the three con sidered species of Luidia share numerous similarities, there are never theless several important morphological differences between, on the on e hand, the podia of L. ciliaris and L. maculata, and, on the other ha nd, the podia of L. penangensis. These differences stress that careful ness is required when generalizations, drawn from the morphology of a single species, are applied to related species having the same life st yle; but also that the genus Luidia needs to be re-examined from a tax onomic point of view.