ORGANIZATION AND FINE-STRUCTURE OF THE MANTLE OF LAEVIPILINA-ANTARCTICA (MOLLUSCA, MONOPLACOPHORA)

The organisation of the mantle edge and the fine structure of the mant le epithelia (dorsal mantle, mantle edge, mantle cavity) of the neopil inid limpet Laevipilina antarctica Waren & Hain, 1992 are described by means of transmission electron microscopy. Comparative data on Neopil ina galatheae, Vema ewingi and Micropilina arntzi, which are based on light microscopy, are also discussed. All results show that the origin al description of the neopilinid mantle edge has to be corrected in se veral aspects. In particular the periostracum groove is in fact situat ed between the inner surface of the median mantle fold and the weakly developed inner mantle fold, a condition being not found in any other molluscan group. The organisation of the tryblidiidan mantle edge is p robably an autapomorphic character of the group and does not represent an archaic conchiferan condition. Implication for the proposed evolut ion of the molluscan mantle edge in general is re-evaluated.