Ovoviviparity and the structure of the brood pouch in Melanoides tuberculata (Gastropoda: Prosobranchia: Thiaridae)

The freshwater gastropod Melanoides tuberculata broods its young in a pouch located in the anterodorsal region of the head-foot. The wall of the brood pouch is composed of smooth muscle surrounded by connective tissue. The lumen of the brood pouch is incompletely partitioned by trabeculae, formed by extensions or folds in the chamber wall that are composed of smooth muscle, connective tissue, nonciliated squamous epithelial cells, and some storage cells containing lipid and glycogen. The lumen of the chamber also contains a few cells with storage products. The general absence of secretory cells suggests that embryos derive little nutrition from the mother, and therefore embryonic development is probably ovoviviparous. Embryos in various stages of development were found within brood pouches, with later stage embryos varying in size. There was a negative relationship between embryo size and number of embryos in the brood pouch.