04 June 2010

The earthworm that didn't get eaten while getting eaten

The terrestrial planarian Bipalium adventitium that has been the star of several posts since September 2009 and which also provided enough experimental data for a note in Tentacle #18 is still alive and well. I have no idea when it was born. I found it near the end of September; it is now at least about 8 months old. I also don't know how long the natural average lifespan of this species is. I feed it an earthworm about once a month. I also don't know how often and how much it would eat in the wild. Maybe may feeding regime is sort of a dietary restriction that is extending the planarian's life.

Anyway, the other day I put a small earthworm in the planarian's container, closed the lid and left. About a half an hour later when I returned, I saw the worm crawling on the dead leaves covering the bottom of the container. But it looked strange: it was shorter and its posterior end ended rather abruptly instead of being pointed the usual way.

The planarian, on the other hand, was in a corner with its pharynx everted over an earthworm that it was in the process of consuming. So what seems to have happened was this: the planarian had seized the worm, but the latter apparently amputated its back half and crawled away, while the less fortunate half became food for the planarian.

The pinkish segment under and to the left of the planarian's head is a piece of the earthworm and the whitish tissue on the left covering what seems to be the rest of the worm is the planarian's everted pharynx.

The worm survived the predator's attack by letting a part of itself get eaten. After I realized it was a true survivor, I returned the worm to the yard whence it had come. Hopefully, it has regenerated its missing half and will soon be passing on its good genes to its offspring.

This is part 6 in this series of posts about Bipalium adventitium.

1 comment:

xoggoth said...

Some say worms can only regenerate from the front end. If they do happen to regenerate from the rear end they become progressively more evil. Well known fact.