Amphibious Hawaiian Caterpillar Proves Evolution is Cool

Amphibious Hyposmocoma larvae on silk line underwater by Patrick Schmitz, Rubinoff Lab

Scientists at the University of Hawaii have discovered the first truly amphibious insect. Daniel Rubinoff and Patrick Schmitz observed larvae from the endemic moth genus Hyposmocoma surviving for weeks in fast moving streams across the Hawaiian archipelago - without coming up for air. Rubinoff and Schmitz say that at least 12 out of 400 species in the genus have the ability to live underwater or on dry land during the insect's larval stage.

We think that's pretty cool, but their research uncovered something else. The truly remarkable part of this story is that in the last 6 million years the moths have independently evolved the amphibious trait in three separate lineages. Scientific American explains:

After genetic sequencing of 2,243 base pairs from 216 individuals in 89 species and 12 lineages, the two researchers...found that the three lines of amphibious species were separated by fully terrestrial lineages, which means that these aquatic capabilities evolved three distinct times or, conversely, that several of the other, terrestrial lineages lost the abilities independently.

"Either scenario is remarkable," noted the study authors. It would "represent the repeated acquisition or loss of a truly amphibious lifestyle not recorded anywhere else" in the insect world--and possibly elsewhere in the animal kingdom.

The researchers believe that the caterpillars get the oxygen they need from the highly oxygenated water of the fast moving streams where they live through specialized skin on their abdomen. This theory is backed up by the fact that the caterpillars quickly drown in stagnant water.

The new discovery also reaffirms the importance of islands in our study and understanding of evolution. (Another reason to mitigate rising sea levels caused by global warming - not that we needed one.) Again, Rubinoff in Scientific American:

"The extreme diversification of Hyposmocoma suggests the importance not only of the right place (Hawaii), but also of the right template (the ancestor of Hyposmocoma), which was able to take advantage of the ecological opportunities provided by the Hawaiian Islands over the past 20 million years."

Visit the researchers website for more pictures and videos of amphibious Hyposmocoma.

(Thanks to tipster Rosy.)

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Tags: Evolution | Hawaii | Insects