Meeting Abstract

P3.114  Tuesday, Jan. 6  Skin Deep: Examining transepithelial resistance and epithelial morphology in sponges. ADAMS, E. D. M*; LEYS, S. P.; University of Alberta; University of Alberta edadams@ualberta.ca

The phylogenetic position of sponges (Porifera) at the base of the metazoan tree makes them valuable subjects for studying the evolution of animal body plans. Unfortunately, past descriptions of features such as epithelial tissues have been vague in this diverse phylum. Sponges are said to lack true epithelia because tight junctions and basal lamina are absent. However, homoscleromorph sponges have a type IV collagen found in basal lamina and a demosponge was reported to express cell junction molecules such as MAGI and tetraspanin. Further, the recent genome project of Amphimedon queenslandica has revealed the presence of most cell junction molecules. We present evidence of functional sponge epithelia by identifying morphological and physiological similarities between true epithelia and the pinacodern of several sponge species. Ultrastructural descriptions are produced using SEM and TEM preparations of adult and juvenile sponges. Actin labeling is used to highlight organized epithelial architecture and identify points of cell-cell contact. Transepithelial resistance (TER) measurements and the transport of labeled dyes are used to test whether sponge epithelia are leaky or have the ability to seal off a defined internal milieu. This research informs theories on the origin of cell-cell junctions and functional tissue layers within Metazoa.