Who Needs A Body? Not These Larvae, Which Are Basically Swimming Heads
Graduate student Paul Gonzalez at Stanford University’s Hopkins Marine Station recently became a hunter, breeder and farmer of a rare marine worm, all to fill in a considerable gap in our understanding of how animals develop. He knew that some animals go through a long larval stage, a developmental strategy known as indirect development, and this rare worm was his chance to better understand that process.
(From Phys.org)– What Gonzalez and his colleagues found was that the worms go through a prolonged phase with little more than head. This work, published in the Dec. 8 issue of Current Biology, suggests that many animals in the ocean likely share this trunk-less stage, and it may even shed light on the biological development of early animals.
“Indirect development is the most prevalent developmental strategy of marine invertebrates and life evolved in the ocean,” said Chris Lowe, senior author of the paper and associate professor of biology. “This means the earliest animals probably used these kinds of strategies to develop into adults.”
Most research animals commonly found in labs, such as mice, zebrafish and the worm C. elegans, are direct developers, species that don’t go through a distinct larval stage. To understand how indirect developers differ from these, Gonzalez needed to study an indirect developer that was very closely related to a well-studied direct developer.
His best bet was a group of marine invertebrates called Hemichordata because there is already a wealth of molecular developmental work done on direct developers in this group. A flaw in this plan was that the indirect developers in this phylum were uncommon in areas near the station.
Undeterred, Gonzalez poured through marine faunal surveys until a 1994 study gave him his big break: Schizocardium californicum, a species of acorn worm and indirect developer in the Hemichordata phylum, was once in Morro Bay, only two hours away.
Through contacting the researchers from that decades-old paper, Gonzalez obtained the exact coordinates of the worms. Once there, he pulled on a wet suit, readied his shovel and began his hunt for the odd-looking ocean-dwellers.
Direct developers are more often used in research largely for reasons of practicality.
“Terrestrial, direct developing species develop fast, their life cycle is simple and they are easy to rear in the lab,” said Gonzalez, who was lead author of the paper.
By comparison, indirect developers develop slowly, have a long larval stage, and their larvae are difficult to feed and maintain in captivity. The reproductive adults are also challenging to keep in the lab and, as Gonzalez has shown, collecting them can be an arduous process. However, the relative ease of studying direct developers has made for a lack of diversity in what scientists know about evolution and development, Gonzalez said.
Read the full article here: http://phys.org/news/2016-12-body-larvae-basically.html#jCp