Fine structure of Lasaea subviridis and Mysella tumida sperm (Bivalvia, Galeommatacea)

摘要: Lasaea subviridis and Mysella tumida sperm resemble the primitive spermatozoan type, but exhibit several unique morphological features. L. heads vary in shape size owing to differing degrees of nuclear condensation. A fully mature, heterogenous acrosomal vesicle with an associated axial rod is present. Up 50% developing gonads have conspicuously angled flagella that propel cells irregular helical paths. This may represent a penultimate stage development because remainder posteriorly-directed swim nonhelical anterior direction. trend toward reduction both condensation swimming ability be long-term consequence increasing localized, non-internal self-fertilization marine invertebrates brood. are monomorphic possess numerous microvilli (30–60 nm diameter up 5.7 μm length) stereocilia radiate from cell membrane surrounding basal body. In this species, does not rod, complex contains five distinct zones varying electron opacity. One these transverse, electron-opaque band apparently composed rolled-up membrane. Following breakdown, unfolds cover tip cell. Although M. hermaphroditic, relative their male investments different. Approximately 40–50% gonadal volume testis compared about 5% subviridis.