An ultrastructural examination of developing and mature paraspermatozoa in Pyrazus ebeninus (Mollusca, Gastropoda, Potamididae)

摘要: The mesogastropod Pyrazus ebeninus, produces true spermatozoa (here termed euspermatozoa) and multi-flagellate, mobile cells paraspermatozoa). mature paraspermatozoon consists of an elongateconical ‘head’ (6.5–8.5 μm in length), constructed electron-dense mosaic sheath surrounding a similarly dense, rod-shaped nuclear core (which runs almost the full length head). An acrosome-like structure forms apex head. Five to eight axonemes are fixed posterior extremity core, each by means attachment complex (dense rod, centriolar cap centriole). A short (3–4 μm) ‘midpiece’ zone follows head multiple interspersed with very elongate mitochondria. tuft (20 tails (termed minor tails) emerges from midpiece addition one long tail major tail) ensheathed dense granules which resemble glycogen granules. single membrane surrounds head, whilst retains original double membrane. Developmentally, arise pair wheel-shaped arrangements centrioles attach indentations nucleus prior its transformation into core. Dense vesicles, derived apparently endoplasmic reticulum, accumulate along around developing (in presence microtubules) condense sheath. Cytoplasmic mitochondria collect at axis cell, where, together axonemes, they form midpiece. Features not previously reported other ultrastructural studies paraspermatozoa include zone, tail, annular junction microtubules final phase maturation. Some features euspermatozoon also described comparative ultrastructure their possible functions Gastropoda, reviewed.