Development beyond the gastrula stage and digestive organogenesis in the snail Pomacea canaliculata (ARCHITAENIOGLOSSA - AMPULLARIIDAE)

KOCH E; WINIK BC; CASTRO-VAZQUEZ A

BIOCELL

Año: 2008

0327-9545

The development of Pomacea canaliculata from the gastrula stage until the first day after hatching was studied. Typical trochophore embryos were developed after gastrulation. However, the velum did not go beyond the formation of a double row of ciliated cells. The foregut (first composed by the stomodaeum, and latter accompanied by the radular sac) was permeated while the velar remnants were still apparent and the midgut became full of the typically pink albumen. Apparently, the albumen which entered through the stomodaeum, was first stored into a central archenteron’s lake and was then endocytosed into some “giant cells” that were lining the wall of the midgut and that developed until being 100 µm high. Giant cells diminished both in size and in number by the end of intracapsular development, and they were gradually replaced by two different types of epithelial cells similar to those containing the putative endosymbiotic corpuscles of the adult: the precolumnar and the prepyramidal cells. The latter had very large nuclei with 2-3 nucleoli and a striking development of the rough endoplasmic reticulum. The genesis of the three cell lineages (giant, precolumnar and prepyramidal cells) is hypothetically attributed to bilateral epithelial streaks that occur in the midgut since the very early stages and that appear to convert into a superficial prolongation of the stomach when hatching is about to occur and it is even more notable after hatching.