Reproductive Activities of Decapod Crustacea

Abstract

"Breeding-form [female][female] of the shrimp Palaemonetes vulgaris are recognized by the [male][male] on physical contact, by means of an integumentary coating which loses its attractive properties after mating or spawning. The spermatophores are dissolved shortly before spawning by a secretion evidently released from the oviduct. The 1st component of the egg-shell is secreted by the egg upon exposure to foreign media; the 2d a half-hour later, whether or not the egg has been laid or fertilized; the 3d only during late segmentation stages. Entry of the sperm-cell seems to occur at the moment of opposition, before development of the egg-mem-branes. It is suggested that a passive spermatozoan is taken up by a naked egg in all decapods. Egg-attachment is effected solely by inter-fusion of the first vitelline membrane with that of other eggs or itself, although the pleopodal glands of the mother evidently release an intensifier required for full development of the inherent property of temporary self-fusibility, especially in decapods in which cross-stalks between eggs do not occur. Hatching begins with rupture of the outer capsule at a fixed locus apparently predetermined in the 2d membrane during segmentation; it is dependent on pressure within the embryo. In contrast, hatching in the fresh-water P. exilipes is by development of. pressure between 3d membrane and embryo, evidently on dis-charge of an osmotic agent.