Reproduction in a carnivorous sponge: the significance of the absence of an aquiferous system to the sponge body plan.

摘要: Sponges usually produce, release, and capture gametes via the aquiferous system, so absence of both choanocytes an system in carnivorous sponge Asbestopluma occidentalis has led to unusual characteristics development for this Phylum. Sperm are highly specialized elongate cells tightly packed into spermatic cysts peripheral tissue sponge. Mature spermatozoa have proacrosomal vesicles at anterior end a ciliary pit surrounding flagellum. Clusters four five oocytes synchronous stages cleavage, suggesting that fertilization is synchronous. All embryos occur same individual. Early cleavage was holoblastic equal; blastomeres two-, four- eight-cell were compact 16-cell stage bi-layered. Late-stage show three cellular regions along anterior-posterior axis: hemisphere with heterogeneous cells, mid-region lying perpendicular A-P axis collagenous matrix, small posterior pole. Unusually Porifera, multiciliated cover all but It inferred occurs by intact whose forceps spicules become trapped anisochelae neighboring sponges. The shape sperm may be designed penetrate loose mesohyl, such arrival packet would lead simultaneous cluster. Loss water canal sponges allowed evolution features habitat animal, modifications not necessarily prerequisite subsequent metazoans. Given extremely versatile mechanisms gametogenesis, embryogenesis, tissue/body structure sponges, generalizations regarding basal metazoan reproduction, development, must approached caution.