The bizarre sex life of squids

[Harlequinmania]

Click through to see the images.

Female Bleeker's Squids (Loligo bleekeri) seek out the most impressive large males, which put on fantastic technicolor courtship displays to attract females.  When a female selects her mate, the male will hold her above him while inserting his tentacle holding a sperm packet into her oviduct where his sperm travels to her ovaries.  The large male will watch over her while she spawns to ensure no other males fertilize her eggs.

However, as the female squid begins to lay her eggs, small sneaker males will dart in and mate head-to-head with the female - an act that takes less than six seconds.  Not only do females willingly accept the scrawny sneakers after she's already mated with the larger jocks, but she even has a special sperm storage organ for the sneakers!  The net result is even the small males get a chance at becoming fathers.  The females likely accept both types of partners because this behavior creates more genetically variable offspring.

If that isn't strange enough, science has discovered the smaller sneaker males actually have bigger sperm ... upwards of 25% bigger.  But it's not what you think.  In the recent study published in BMC Evolutionary Biology, researchers concluded both sperm sizes swam at the same speed, meaning that the bigger sperm from the smaller male actually do not have a competitive advantage over the smaller sperm from the larger male.  So what's with the drastic size difference?  The authors believe the sperms likely evolved to suit females' two segregated sperm reservoirs.  The sneaker's and jock's sperm end up in distinct receptacles, and the seawater around these receptacles may have varying parameters such as pH and salinity that favor one sperm size over another.  According to the study, this is the first evidence of males of two different sizes possessing differently sized sperm and employing different sexual positions to copulate.

This isn't the only cephalopod known for its bizarre sexual escapades.  Take, for instance, the 'cross-dressing' Indonesian Octopus Abdopus aculeatus. Big males will guard the den of females in an attempt to prevent lesser males from mating.  But smaller males will impersonate as females to sneak inside the den, mate with the female, then make a quiet retreat after the deed.  The masquerade works so well that scientists have documented big males actually trying to mate with the small males sneaking in!

The things guys will do to get with girls ...

 

via BMC Evolutionary Biology and National Geographic and evolution.berkeley.edu

View the full article