Phronima, makes a morbid nursery

Phronima or as her friends call her, the Pram Bug, is a highly specialized amphipod that has taken the motto "waste not, want not" to heart. But before I get to that, let me introduce you to this all to often overlooked crustacean.

The many eyes of Phronima.

Phronima is a genus of very specialized amphipods. Each comes equipped with four eyes. This has nothing to do with myopia but an adaptation where two of its eyes are constantly fixed in an upward gaze while the other two eyes are focused on the world ahead or the task at hand. Its two stargazers are, what at first inspection, appear to be some sort of crest upon the amphipods head. The other two eyes are forward facing and on movable stalks for better seeing in many directions.


If you happen to have a submersible, you would find these critters throughout the pelagic zone (essentially every part of the deep ocean other then the ocean bottom). In this state your average Phronima would look something like this:

Did I forget to mention that they are almost entirely transparent?

Your typical solitary variety of salp.

But remember that thing I stated about "waste not, want not"? Well now is when I get to tell you about that as well as a harrowing story of a single mother gaining and maintaining a home for her precious children. Enter the pregnant mother, desperate for a home, unfortunately it is the middle of the ocean so rental property is a bit hard to come by. But this does not dissuade her, for she knows something better then real estate tips. She knows how to find salps. For those who have not heard of these members of the oceanic plankton, sapls are mobile tunicates, Sea Squirts that couldn't stand becoming a sessile brainless filter feeder so instead settled for being a free-swimming brainless filter feeder.

But as we said, our mother Phronima is in desperate need of a home and when that delicate little salp comes along it is the very solution to all her problems.  The only thing stopping Phronima from moving into this nice cylinder of tunican is all these messy internals.  But being pregnant, Phronima could do with a bit of a meal, so she begins eating the insides out of the hapless salp (it is almost a pun yet far enough to be safe, amazing).   Once all that messy internal tissue is done away with, Phronima can get around to her main goal of raising her family.  So she lays her eggs along the inside of the hollowed out salp and continues to swim along with it so that it will get plenty of fresh water and nutrients flowing by.  This leaves our once homeless mother with not only a chic new house but the foundings of a whole new brood, a brood that will continue on  living the double lives of the female Phronima, part free living, part necro-parasitic, as Michael Bok described it. Michael, on his own blog, also shows how this endearing little creature may have been the inspiration for the Alien Queen from the film Aliens.

As cozy as one could be in a corpse.

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References:
Photo, Phronima eyes: Woods Hole Oceanographic Institute, Mike Land
Photo, Corpse home.
Arthropoda