Ultrastructure and Morphogenesis of the Apyrene and Eupyrene Spermatozoa in the Gypsy Moth (Lepidoptera: Lymantriidae)

Abstract

The ultrastructure and morphogenesis of apyrene and eupyrene spermatozoa of Lymantria dispar (L.) is examined. Apyrene prophase I spermatocytes are characterized by sparse perinuclear membrane, smaller nuclei, bivalents lacking synaptonemal complexes, and few mitochondria. Eupyrene prophase I spermatocytes are characterized by dense perinuclear sheathing, large nuclei, diffuse chromatin, synaptonemal complexes, and numerous mitochondria. Apyrene metaphase I is atypical involving chromatin clumping and mis-segregation. Eupyrene metaphase I spermatocytes show localized meiotic centromeres and sheathed nuclear division. However, kinetochores are amorphous and difficult to discern. Apyrene spermiogenesis involves the morphogenesis of the axoneme and mitochondrial derivatives in the absence of differentiating nuclei and acrosomes. Eupyrene spermiogenesis involves the differentiation of nuclei, axonemes, acrosome tubes, mitochondrial derivatives, lacinate appendages, and reticular appendages. Both eupyrene spermatozoa and apyrene spermatozoa undergo additional morphogenesis upon leaving the testis. The most apparent of these are the loss of lacinate appendages in eupyrene sperm and the gain of an extracellular sheathing in both eupyrene sperm and apyrene sperm.