A slug saves the trip

Yesterday we drove up to San Francisco to attend my mom's graduation. While the graduation ceremony went well, the rest of the trip hasn't been stellar.

First, as regular readers will remember, the two subs I lined up to cover my classes both ended up in the hospital over the weekend, forcing me to cancel my lecture and lab classes. Then our car started acting up on the drive north; the car made it to both the graduation and my parent's house, but not without causing much worrying and emitting worrying odors.

So, rather than sleeping late and relaxing on the couch today, we've been on the phone with mechanics who are trying to diagnose the frustratingly sporadic problems. It has been neither fun nor cheap.

However, while investigating who's been eating all the seeds from my dad's birdfeeder (our surprising discovery: birds!), we found this cute little slug climbing up the sliding glass door:



How adorable!
Slugs are one of the few types of terrestrial mollusks; they're closely related to snails (but either lack a shell or have much reduced shells). My students often think, incorrectly, that slugs are just snails that have lost their shells. Slugs and snails are two completely different lineages; snails that lose their shells die, they do not turn into slugs.

The slug's head is at the lower right of the picture, and has two sets of tentacles. The smaller tentacles lower to the ground are the oral tentacles, which contain chemosensors, while the longer tentacles are cephalic tentacles, which contain photoreceptors. As the slug crawls over surfaces, it tastes the surface it's walking on by touching it at regular intervals with its oral tentacles.

There's no better way to brighten a day than to find a slug.