Shrunken Heads of Sea Snakes Explained

Some sea snakes have heads that look comically small compared with the rest of their body. New research shows these shrunken heads evolved quite rapidly, allowing the snakes to hunt eels hiding in tight spaces.

If you only looked at the genes of the blue-banded sea snake and the slender-necked sea snake, the two species would seem nearly identical. But the close cousins, which are found in waters around Southeast Asia and Australia, have quite different physical looks, researchers say.

"The slender-necked sea snake is half the size, and has a much smaller head, than the blue-banded sea snake," study researcher Mike Lee, from the South Australian Museum, said in a statement. "This suggested they separated very recently from a common ancestral species and had rapidly evolved their different appearances."

The researchers believe some sea snakes developed shrunken heads to be more effective eaters since these species poke their heads into narrow eel burrows to look for food, whereas their big-headed cousins feast on crevice-sheltering eels and gobies.

"One way this could have happened is if the ancestral species was large-headed, and a population rapidly evolved small heads to probe eel burrows — and subsequently stopped interbreeding with the large-headed forms," Lee added.

Both the blue-banded sea snake and the slender-necked sea snake belong to the genus Hydrophis. With more than 30 species, this group is by far the most diverse group in the Hydrophiinae subfamily and it has a lot of tiny-headed members. In fact, microcephaly (the condition of having a small head) has evolved at least eight separate times in Hydrophis during their relatively rapid diversification over the past 3.5 million years, researchers say.

For Subscribers

FOR SUBSCRIBERSCBP leaders cut out of Trump ad buy decision

FOR SUBSCRIBERSAmerican passenger drafted goodbye texts to her family as Flydubai plane plummeted

FOR SUBSCRIBERSCornell rape allegation pushes embattled New York prosecutor into national spotlight

FOR SUBSCRIBERSAbdul El-Sayed tries to woo MAHA voters as Democrats seek inroads with RFK’s supporters

FOR SUBSCRIBERSKratom-like substances are popping up in a typically benign supplement

FOR SUBSCRIBERSGOP super PAC increases its spending for Sen. Jon Husted in tough Ohio race

FOR SUBSCRIBERSRecords reveal tumultuous marriage between slain New York Times executive and wife

FOR SUBSCRIBERSFrom clean energy warrior to ‘wall of shame,’ James Talarico reverses on a fossil fuel money pledge

FOR SUBSCRIBERSCongressional staff planned official trip with luxury stops in Italy and France weeks before election

FOR SUBSCRIBERSA harrowing ordeal aboard an Israel-bound plane

FOR SUBSCRIBERSOpenAI CEO Sam Altman to skip congressional hearing on rogue AI agents

FOR SUBSCRIBERSKey DOJ lawyers departed Trump ‘grand conspiracy’ probe amid pressure to produce, source says

FOR SUBSCRIBERSTrump’s new AI chatbot often links to a site launched under Clinton 26 years ago

FOR SUBSCRIBERSAt MAHA summit, industry CEOs the movement once vilified take the stage

FOR SUBSCRIBERSThis Paralympian has two goals: Win medals and give away $500,000 to her teammates

Meanwhile, no other genus in the sea snake family (not Aipysurusnor Ephalophis nor Hydrelaps) has snakes that have evolved shrunken heads. What's more, these groups tend to be much less diverse, each represented by a half-dozen species at best.

For Subscribers

FOR SUBSCRIBERSCBP leaders cut out of Trump ad buy decision

FOR SUBSCRIBERSAmerican passenger drafted goodbye texts to her family as Flydubai plane plummeted

FOR SUBSCRIBERSCornell rape allegation pushes embattled New York prosecutor into national spotlight

FOR SUBSCRIBERSAbdul El-Sayed tries to woo MAHA voters as Democrats seek inroads with RFK’s supporters

FOR SUBSCRIBERSKratom-like substances are popping up in a typically benign supplement

FOR SUBSCRIBERSGOP super PAC increases its spending for Sen. Jon Husted in tough Ohio race

FOR SUBSCRIBERSRecords reveal tumultuous marriage between slain New York Times executive and wife

FOR SUBSCRIBERSFrom clean energy warrior to ‘wall of shame,’ James Talarico reverses on a fossil fuel money pledge

FOR SUBSCRIBERSCongressional staff planned official trip with luxury stops in Italy and France weeks before election

FOR SUBSCRIBERSA harrowing ordeal aboard an Israel-bound plane

FOR SUBSCRIBERSOpenAI CEO Sam Altman to skip congressional hearing on rogue AI agents

FOR SUBSCRIBERSKey DOJ lawyers departed Trump ‘grand conspiracy’ probe amid pressure to produce, source says

FOR SUBSCRIBERSTrump’s new AI chatbot often links to a site launched under Clinton 26 years ago

FOR SUBSCRIBERSAt MAHA summit, industry CEOs the movement once vilified take the stage

FOR SUBSCRIBERSThis Paralympian has two goals: Win medals and give away $500,000 to her teammates

"Rapid evolution of head size variation is therefore a likely contributing factor in the explosive speciation in Hydrophis group sea snakes," the researchers wrote in an article published this week in the journal Molecular Ecology.

Follow Megan Gannon.Followus, &.Original article on LiveScience.com.

• Image Gallery: Snakes of the World
• That's Odd! The 10 Weirdest Animal Discoveries
• Dangers in the Deep: 10 Scariest Sea Creatures