Basically Marine Acorn Worms Have A “Swimming Head”

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Most marine worm have a complex life cycle which is divided into a pelagic, one is planktotrophic larval stage and second is benthic adult stage. According to genetic analyses, Adult worms can grow up to about 40 centimeters.

These marine worms spend their larval phase as little more than a tiny, transparent "swimming head" (left) before metamorphosing into a juvenile (middle). The larval forms of these indirect developing animals are so different from adults, that they are said to possess their own body plan.

Graduate student Paul Gonzalez at Stanford University's Hopkins Marine Station in Pacific Grove, California. He recently became a hunter, breeder and farmer of a marine worm, just to know how animals develop. In California, a mud flat in Morro Bay is the only place where this one species of acorn worm, Schizocardium californicum, is found. After digging up these creatures, Paul Gonzalez, an evolutionary developmental biologist at Stanford University, knew that some animals go through a long larval stage a developmental strategy known as indirect development.

Gonzalez and his colleagues found that the worms go through a prolonged phase with little more than head. They suggest that many animals in the ocean likely used to share this trunk-less stage, and it is the development of early animals. Whereas Genes linked to trunk development are switched off during the larval phase, and most of the genes are switched on with head development, Gonzalez says. So a larva and an adult worm look so different, this work was published in the Dec. 8 in Current Biology.

The larvae come from eggs laid on the mud. When tides or flood comes in the area, the gel-filled animals use hairlike cilia to swim upwards to algae buffet. "They used like a feeding machines," Gonzalez says. They transferred them in balloon-shaped noggins instead of transferring them into wriggling noodles, which can help them to float and feed more efficiently. After two months, larvae gorging at algae buffet, they used to grow roughly about 2 millimeters and they can stretch up to about 40 centimeters.