Corolla ovate a rare sea butterfly

By Bec Crew | June 5, 2014

This tiny sea butterfly spends its days floating in the ocean, feeding on plankton

Contributor

Bec Crew

Becky Crew is a Sydney-based science communicator with a love for weird and wonderful animals. From strange behaviours and special adaptations to newly discovered species and the researchers who find them, her topics celebrate how alien yet relatable so many of the creatures that live amongst us can be.

FLOATING THROUGH THE ocean like a lonely spacecraft on a mission to smother its transparent hull in stars, Corolla ovate is a rarely encountered species of sea butterfly.

Found all around the world’s oceans at depths of up to 2km, this tiny creature is known to haunt the coast of Australia, in the Bismarck, Solomon and Coral seas up near the Cape York Peninsula and Papua New Guinea, and down south in the Bass Strait.

It’s delicate thing, at just 4cm long, and spends most of its days trying to avoid the enormous mucous webs laid out for it by carnivorous sea slugs called Cliopsis. Also known as sea angels, these formidable hunters are the sea butterfly’s own Doctor Who nightmare.

Sea butterfly rides on the ocean currents

When it’s not avoiding the sticky snares of lurking sea angels, C. ovate rides the ocean’s current in search of tiny pieces of plant matter or plankton to feed on. This lifestyle has allowed it to do away with the hard shell of its mollusc relatives, and it instead houses its mass of internal organs inside a gelatinous, spotty dome called a pseudoconch.

Its foot (the visible flesh that a garden snail gets around on) has morphed into a pair of wing-like lobes called parapodia, which can grow up to 8cm across. C. ovate gently flaps these transparent membranes back and forth for extra propulsion though the ocean.

Sea butterflies are protandric hermaphrodites, which means they start out with male reproductive organs, before replacing them with female reproductive organs later in life.Exactly why they do this is a bit of a mystery, but it could have something to do with size.

Eggs are bigger than sperm, so perhaps the smaller, younger males are better suited to carrying small sperm, and then as they grow older and larger, they become females to hold onto the larger eggs!