23 March 2007

Slugs 'n isopods

Many slug species tend to aggregate when they are resting. That behavior is called huddling. Here is a note I had in issue No. 15 of Tentacle that was about a specimen of the native U.S. slug Philomycus carolinianus that was huddling with an introduced Arion subfuscus.

I have many rocks in my backyard and almost every large rock has one or more resident slugs underneath it. Even more numerous in the same places are isopods, which appear to be more sensitive to dehydration than are slugs. On many occasions I have seen isopods clustered around resting slugs. This morning I was able to photograph 2 such clusters under one rock.

slugs&isopods1

The smaller slug was probably a juvenile Limax maximus, while the larger one in the picture below is probably an Arion subfuscus.

slugs&isopods2

If we define huddling loosely as the clustering of animals for mutual protection against environmental extremes, then what we have here would be an example of interphylar huddling. However, the isopods are probably benefiting much more from huddling against a slug than is the slug from having isopods lined up against its body.

2 comments:

Megan said...

Yes, I don't think those little dry, armored isopods are doing much in favor of the slugs. But you'd think they'd interact somehow. Slugs and isopods seem to like the same habitats - rocks and the underside of bark.

Anonymous said...

Maybe the slugs secertly eat the isopods when nobody is looking. Not a mutual relation ship still, the slugs need the moisture to and the isopods are robbing it from them.