Practice question

Reproductive biology in most brachiopods is gonochoristic with separate sexes, gonads in coelomic lining associated with mantle canals, gametes shed via paired metanephridial gonoducts opening into mantle cavity then seawater where external fertilization occurs through synchronous broadcast spawning triggered by seasonal cues. Eggs moderately yolky cleavage holoblastic radial gastrulation forms free-swimming lecithotrophic larva with setae. No copulatory organs or internal fertilization except few brooding genera retaining larvae. External fertilization ensures wide dispersal but requires dense adults for success, explaining restricted contemporary distribution to cool low-predation refuges unlike internal fertilization in cephalopods and gastropods.