The Caribbean hermit crab (Coenobita clypeatus) is one of 15,000 living species of decapods.© J. Wolfe
Decapods, 10-legged crustaceans broadly categorized into shrimp, lobsters, and crabs, are a globally important food source worth billions of dollars.
But the animals in this order, which contains more than 15,000 living species and 3,000 extinct ones, are also ecologically fascinating. Decapods make homes in a wide variety of global habitats, from the open oceans to coral reefs, as well as in freshwater streams and lakes. But despite the economic and environmental significance of decapods, piecing together the evolutionary relationships of this group has been difficult.
Now, a new study led by researchers at the Museum, Harvard University, and Florida International University resolves gaps in our understanding of the decapod tree of life.
“When we started this work in 2013, most studies that looked at the evolutionary relationships of decapods were based on physical traits, and the genetic work that had been done was very limited in scope,” said lead author Jo Wolfe, a postdoctoral researcher at Harvard University and former Gerstner Scholar at the Museum who spearheaded the research along with Heather Bracken-Grissom from Florida International University.
To determine the evolutionary relationships within the clade, the researchers used a newly developed set of more than 400 genes conserved across the genomes of all known decapods, which they sequenced for 94 species representing almost all major groups. The team, whose study is out this week in the journal Proceedings of the Royal Society B, expects that their framework can be used for future studies of decapod evolution.
One of their central findings is that decapods first evolved 450 million years ago—100 million years earlier than previously thought—with most modern lineages diversifying shortly after the “great dying” mass extinction that took place 250 million years ago. The research also finds that the main groups of lobsters and crabs each have a single evolutionary origin, while shrimp groups evolved earlier.
“This was one of the earliest recipes in the Museum’s next-generation DNA sequencing cookbook, with Jo Wolfe as head chef,” said Mark Siddall, a curator in the Museum’s Division of Invertebrate Zoology and coauthor on the study. “The results in many respects validate more than 200 years of research covering a span of almost half a billion years of animal evolutionary history, about which there has been considerable debate—a delicious outcome.”