No abstract

No abstract

Electron microscopic study of sperm head differentiation in the lizardAgama stellio. Can. J. Zool. 65: 2959-2968. Early differentiation of the spermatid of Agama stellio is demonstrated by two anterior nuclear depressions, occupied bv two proacrosomal vesicles, which fuse to form one vesicle. Later, this vesicle exhibits an acrosomal granule in its midposterior portion. The space between the posterior acrosomal membrane and the nuclear envelope is occupied by a subacrosomal fibrous layer which later exhibits a subacrosomal granule posterior to the acrosomal granule. The acrosomal vesicle and the nuclear depression flatten and later elongate. The acrosomal granule spreads and assumes the inverted V shape of the acrosomal vesicle, and the subacrosomal material assumes a feathery shape capping the nuclear prolongation. The subacrosomal granule on top of this feathery material forms a long, cross-striated subacrosomal rod which extends towards the tip of the acrosome. The chromatin material undergoes condensation into spirally oriented fibers, which eventually become homogeneous and dense. This process is accompanied by a change in the orientation of the manchette microtubules, which initially occur as rings around the nucleus and are eventually found parallel to the longitudinal axis of the nucleus. AL-HAJJ, H., JANAKAT, S., et MAHMOUD, F. 1987. Electron microscopic study of sperm head differentiation in the lizard Agama stellio. Can. J . Zool. 65 : 2959-2968. Le ddbut de la diffdrentiation de la spermatide chez Agama stellio se manifeste par la formation, sur le noyau, de deux ddpressions antdrieures contenant deux vCsicules proacrosomiennes qui se fusionneront. Plus tard, il se forme un granule acrosomien dans la region mdsopostdrieure de la vdsicule. L'espace compris entre la membrane postdrieure de l'acrosome et l'enveloppe du noyau est occupd par une couche fibreuse subacrosomienne qui contiendra dventuellement un granule subacrosomien postkrieur au granule acrosomien. La vdsicule acrosomienne et la ddpression du noyau s'aplatissent, puis s'allongent. Le granule acrosomien s'dtend et prend sa forme typique en accent circonflexe, alors que la substance subacrosomienne devient ramifiee et couvre le prolongement du noyau. Sur cette substance, le granule subacrosomien forme un bitonnet allongd a stries transversales qui se prolonge vers le sommet de I'acrosome. La chromatine se condense en fibres spiraldes qui deviennent homogknes et denses. Ces ddveloppements s'accompagnent d'un changement d'orientation des microtubules du manchon qui, au ddpart, sont disposks en anneaux autour du noyau, puis deviennent parallkles a l'axe longitudinal du noyau.[Traduit par la revue]

No abstract

The feasibility of fertilizing preovulatory lobster oocytes was examined in vitro under various experimental conditions. Large (1.6 mm diameter) and small (0.6 mm diameter) oocytes were compared in fertilization trials. Small oocytes were surrounded by a thin envelope thought to correspond to envelope 1A of mature oocytes. Large oocytes were surrounded by a fully formed vitelline envelope comprised of two distinct sublayers, 1A and 1B. Although sperm bound very effectively to the coat surrounding small oocytes, none penetrated the coat or fertilized the oocytes. Large diameter oocytes that were removed from follicles by dissection were fertilized by sperm from the proximal vas deferens of males and by sperm from the seminal receptacle of females. Fertilized oocytes showed a high degree of polyspermy. Higher numbers of sperm bound to, penetrated, and fertilized large diameter oocytes when inseminations were done in a saline solution (2.5LSH) than when done in artificial sea water (ASW). Sperm failed to bind to large diameter oocytes that were induced to ovulate in vitro by collagenase treatment. Contaminating enzymes may have destroyed the sperm receptor in envelope 1A of collagenase treated oocytes. Our in vitro fertilization method will allow the process of fertilization to be studied experimentally in lobsters, and it may be applicable to other decapods.Many aspects of lobster (Homarus) reproductive biology have been well characterized in numerous studies done during the past 100 years (reviewed by Aiken and Waddy, '80; Talbot, '90). The structure of the gametes has been examined in considerable detail at both the light and electron microscopic level (Herrick '09; Kessel, '68; Talbot, '81a,b; Pochon Mason, '68; Talbot and Chanmanon, 80a; Schade and Schivers, '80). Morphological changes occurring in sperm during the acrosome reaction have also been described (Pochon-Mason, '68; Talbot and Chanmanon, '80b), and the role of the cortical reaction in formation of the fertilization envelope has recently been analyzed (Talbot and Goudeau, '88).In spite of much interest in this topic, relatively little is known about the mechanism of fertilization in Homarus americanus. This is due to the biennial ovarian cycle characteristic of this species and the difficulty in obtaining ovulated unfertilized oocytes or freshly spawned oocytes. Studies of gamete interaction in the lobster would be facilitated by an in vitro technique for fertilizing eggs. Goudeau and Goudeau ('86) have successfully fertilized lobster eggs in vitro using sperm from the seminal receptacle of a female that was spawning. To catch a female in spawning, however, requires constant monitoring of mature females and is not practical for most experimental applications.The main purpose of this study was to examine the feasibility of fertilizing preovulatory lobster oocytes in vitro. Oocytes were collected from ovaries by dissecting them free of follicle cells and inseminating them in vitro with sperm from either the proximal vas deferens (PVD) of males...