[Teratogenic and metamorphosis inhibiting activity of retinoic acid in Ciona intestinalis].

Exposure of embryos of the sea squirt, Ciona intestinalis, to all-trans-retinoic acid (between 10(-5) and 10(-7) M) causes specific malformations of the larvae and suppression of settlement and metamorphosis. Whether the vitamin A derivative was administered at the 2-cell stage, or at the early gastrula stage did not affect the nature of the extent of the ensuing anomalies. Malformations include a dorsal bulge of the body, an irregular disposition of ocellar pigment, and a twisted tail. Treated larvae have no statocyst pigment. There is also a reduction in size of the body, compared to control larvae. Retinoic acid retarded hatching, or even blocked it (at 10(-5) M). Obviously retinoic acid interferes with the induction of metamorphosis, possibly through neutralizing one or more factors responsible for settlement and metamorphosis. The possible role of thyroxin in these processes is being critically evaluated.