Antarctic Bivalves Change Sex to Breed and Brood

A new study suggests that Antarctic bivalves change sex in order to brood their young.

Researchers from the National Oceanography Centre, Southampton in UK, studied the hermaphrodite nature of the Antarctic bivalves, a type of freshwater molluscs.

They described the nature of invertebrates Lissarca miliaris from King George Island and Signy Island, Antarctica, using histological and dissection techniques. The species is found abundantly in sub-Antarctic Magellan Region and islands of the Scotia Arc.

While the marine environment in Antarctic will be exposed to cold temperatures, the marine mammals have shorter spans of primary productivity. Hence invertebrates like molluscs have to adapt themselves to the surrounding ambience in order to increase their productivity.

When the research team studied the species of L. miliaris, they found that the male and female have hermaphrodite reproductive traits, wherein the male and female develop gonads simultaneously.

During a previous study, experts concentrated on the eggs brooded by females. But in the new study they also observed the process of reproduction at cellular level, which is when they found that the eggs were present in males, reported BBC.

"Curiously, we found huge numbers of very small eggs in functional males, which appear to be far higher in number than an individual could brood throughout the life of the animal," PhD student and lead author Adam Reed from the university told BBC Nature.

The BBC report pointed out researchers as saying that the bivalves reproduce as males when they are in their development stage, but they change their trait and become females when they grow up and become large to brood the young ones. This suggests the possible idea as to how female molluscs brood more number of offspring.

While brooding is common among the marine invertebrates including molluscs, this is the first time that researchers have observed a hermaphrodite trait among Antarctic bivalves.

Researchers pointed out that hermaphroditism in L. miliaris increases the reproductive efficiency as the females have short periods to brood their young ones in a harsh environment, where natural food resources are limited.

The findings of the study are published in the journal Polar Biology.