70 Sexuality and gender, animal sexuality

Tough Survivors: Gender Fluid Eels

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To rice farmers and agricultural economists, the rice paddy eel is a pest, presenting an indirect threat to rice crops. To me, it’s yet another example of the remarkable gender and sexual diversity of the natural world – and one which is a real tough survivor.

REFLECTING nature’s remarkable diversity, the rice paddy eel is both hermaphrodite and transgender.
All the young start as females; some become masculine as they mature. When female densities are low, some of the male eels become transgender, turning into the opposite sex again.
The process, which takes up to a year, allows the replenishment of female populations. The greater the proportion of females in the eel population, the greater the reproduction rate.
This remarkable agility to adapt, and without natural predators, allows the paddy eel to multiply fast.
A rice paddy eel may grow as long as 3 feet to 4 feet and weigh as much as half a kilogram. As a voracious predator, its rapid spread threatens fishes, frogs, snails, worms and aquatic insects.
It survives harsh environments as well, from fresh and brackish to saline conditions and even cold temperatures well below freezing.
It can survive for weeks without food and, by burrowing in moist ground, can live for long periods without water.
When not using gills underwater, the rice paddy eel gets a fourth of its oxygen needs from the air – through the skin.”