Sunday 25 February 2018

Marine creatures eat, prey, love

BENEATH the waves, sea creatures lead secret lives. Occasionally, when details are revealed, they can be surprising.

Not many people know, for example, that a barnacle's penis is 20 times its body length. Didn't know it had one; thought the creatures reproduced by osmosis while glued to rocks?

The hermaphrodite marine flatworm (pseudoceros bifurcus) possesses both male and female sex organs and when two of the creatures meet both want to be the male as this confers a reproductive advantage. So a dramatic duel develops -- with penises as swords. The flatworm's is rapier-like with a sharp tip.

Both go 'en garde' and the loser is the first to be impaled, receiving sperm by hypodermic injection from the successful swordsman. Before the final thrust, however, there is feinting and parrying with occasionally one creature gliding out of reach to fight another day.

Scientist-observers at the Max-Planck Institut in Germany explained that such avoidance could offer the benefit of being inseminated later by other and perhaps more attractive 'stabbers' resulting in more successful offspring.

The big blue octopus (octopus cyanea) grows to 16cm in body length with arms of up to 80cm.

When the animals mate the male inserts its third right arm into the female's mantle cavity and then into one of two paired oviducts. But there can be a horrifying outcome of such coupling.

Scientists from Woods Hole Marine Biology Lab in Massachusetts observed a male creep up on a female and mate 13 times. Then the female suddenly grabbed her partner, suffocated him and dragged him into her den. She spent the next two days devouring him.

Sexual cannibalism is a rare phenomenon and was thought to be confined to certain insects and amphipods such as sandhoppers.

The behaviour of the female octopus might explain why some males prefer to make sexual advances in the open where they have a better chance of escape. Males also seek females which have had a meal, believing they can escape being next for dinner.

The Woods Hole team observed that on the morning after the female had polished off her first admirer another one appeared and mated successfully for about three hours -- but at arm's length. He was a very careful suitor, hiding behind a nearby rock and inserting his mating arm into the den, and the female, making sure she did not see him.

Mating may be a dangerous business for octopuses, and an ultimately final one for salmon and squid, but the male paper nautilus, another cephalopod mollusc, uses its intelligence and speed in the game.

It has a detachable penis that swims off searching for a female, leaving the nautilus free to go chasing other creatures to ingest, grabbing them with its sucker-like tentacles. For the nautilus, sex can be a secondary consideration. Dinner comes first.

Sunday Independent

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