bothriembryons

Bothriembryons are a type of embryo characterized by the presence of a blastopore, which is an opening in the blastula stage of development. This blastopore is the precursor to the anus in the adult organism. Bothriembryons are found in the phylum Echinodermata, which includes sea stars, sea urchins, and sea cucumbers. The development of bothriembryons is distinct from that of enterocoelous embryos, which have a blastopore that becomes the mouth.

In bothriembryons, the blastopore remains open during the early stages of development, allowing for the exchange of materials between the embryo and the external environment. This is in contrast to enterocoelous embryos, where the blastopore closes early in development, forming the anus and creating a digestive system.

The term "bothriembryon" comes from the Greek words "bothros," meaning "hole," and "embryon," meaning "embryo." This name reflects the characteristic feature of these embryos, which is the persistent opening that serves as the anus in the adult organism.