True sea snakes stick to one male only

Gliding silently through the ocean, sea snakes are a rarity in more ways than one. Each female allows only one male to father her brood.

As a general rule, female reptiles mate with multiple males to produce a single brood. But when Vimoksalehi Lukoschek of James Cook University in Townsville, Queensland, Australia, decided to verify this in elapid snakes, a family that includes cobras and sea snakes, she found something new.

Lukoschek looked at 12 pregnant female sea snakes, from six species, that had been killed by fishing trawlers. She took DNA samples from both the females and their unborn offspring, and used 10 chunks of the genome that vary widely to work out how many males contributed to each brood. To her surprise, each brood had only one father (Journal of Heredity, DOI: 10.1093/jhered/esr017).

“The contrast with what we’ve seen in other groups is striking,” says Richard King of Northern Illinois University in DeKalb. The pros and cons of single and multiple matings are poorly understood, he adds.

The sample size is small, warns Tobias Uller of the University of Oxford. “Three out of six of the species were represented by a single clutch,” he says.

Lukoschek says she has no idea why the females are so selective.