In barnacles

Feb 7, 2008 19:06 GMT  ·  By
Barnacles with feathery legs and penis from calm water (up) and rough wave area (bottom)
   Barnacles with feathery legs and penis from calm water (up) and rough wave area (bottom)

Blue whales may have 2,4 m (8 feet) long penises, but that's relatively short: it is like a human having a 10 cm penis, as the blue whale can reach 33 m (100 feet) body length.

But barnacles, small crustaceans looking like small shells fixed on rocks or man made structures (or sometimes even on whales!) with a muscular stalk or not are better known for other reasons: Gooseneck barnacle, for example, is one of the most expensive seafoods.

Barnacles are hermaphroditic and alternate male and female roles over time. But how to mate with you neighbor when you're stuck on the place? Simple: by developing the longest penis in the animal kingdom, in proportion to their body length: it is 8 times bigger than the animal's body! As the barnacles are just a few cm long, their penises won't be so obvious for humans, but it's like a 1.8 m (6 ft) man having a 14 m (47 ft) long penis!

But such large penises pose a problem: waves weep on the surfaces where these crustaceans use to live, and a too-long penis could not be used in such turbulence.

"The benefit of a longer penis is obvious for the barnacles - it helps them reach more barnacles - but the tradeoff is that it could wave around wildly on shores exposed to waves," explained researcher Christopher Neufeld, an evolutionary marine biologist at University of Alberta in Edmonton.

His team found how barnacles solve the issue, in a research published in the journal Proceedings of the Royal Society B: they can radically shift the size and shape of their penises according with the waves. Barnacles collect food (detritus, bacteria and small particles) by sticking them with their feathery legs into the water. The legs can change size and shape very easily.

"We thought maybe barnacles could change the size and shape of their penises as well," Neufeld told LiveScience. Neufeld's team compared barnacles (Balanus glandula) from gentle, protected harbors and rougher, exposed shores. The penises of the barnacles were artificially inflated using tubes and hypodermic syringes. Barnacles living in agitated coasts had shorter, stouter and over twice more massive penises than individuals inhabiting gentler waters. Barnacles located away from their native shore could readily come with the right type of anatomy corresponding for the water they were put to live in.

"This adaptability results from the fact that these creatures could end up stuck on surfaces with various ocean conditions. There's the chance that the environment barnacle larvae end up settling is vastly different from the one experienced by their parents - their parents might have lived in a protected harbor, but the larvae might end up drifting to a wave-exposed shore. So they deal with this variation by being able to change their legs and penises," said Neufeld.

While in other species competition with other males, sperm competition, female choice or sex war explain penis's morphology, here is a non-biological factor controlling this: waves.