Bonellia viridis
Female
Bonnelia viridis
Phylum: Echuira.
An example of environmental sex determination as well as sexual dimorphism.
In the early stages of life, those larva which settle on the sea bed become female and the larva which settle on the body of an adult female attach and develop into a male due to exposure to the chemical bonellin. The female have a main body which is usually buried in the sand and a long forked proboscis which protrudes above the sand on the sea floor. The male, however, is very small and a few days after settling on the female he detaches from the proboscis and moves to the uterus of the female where he lives the rest of his life in a special chamber: the androecium. The males get their nutrients by absorbing it straight from the female and so never develop a functioning mouth or gut. Their sole function in life is to fertilise the female which feeds on detritus and small animals.
