Mesencephalic Trigeminal Nucleus in Sharks

Abstract

In 22 adult sharks representing 8 spp. [Scoliodon terranovae, Mustelus, Carcharinus obscurus, C. limbatus, C. milberti, Isurus oxyrinchus, Prionace glauca and Galeocerdo cuvieri],the mesencephalic trigeminal nucleus (Mes V) was examined by Romanes reduced Ag method. Morphological evidence is presented of extensive development of neurites and intranuclear communication among Mes V cells of sharks and their apparent innervation by extranuclear neurons. Species differences and the possible significance of the morphology of the Mes V in sharks on certain aspects of their behavior are discussed. A comparison of the Mes V of elasmobranchs and those of reptiles and mammals is included.