Spiders Of The Sea

It’s been a while since I’ve studied any marine biology, but this Ecotone wiki topic on spiders and place makes me think of pycnogonids. The Pycnogonida are a group of marine arthropods related to the arachnids such as spiders, scorpions, mites, and ticks. Another name for the group is the Pantopoda, meaning “all legs”, which is pretty much a description of what they look like.

I don’t know whether I’ve seen one live, but they’re to be found on the Pacific coast. One list gives nine species for the San Francisco Bay. Around Bodega Bay (home of the Bodega Marine Laboratory), one species Pycnogonum stearnsi is listed as uncommon under rocks (given the locality, I think this means the rocks of the breakwater). Members of its genus feed on coelenterates, especially sea anemones. To quote from Ricketts et al. book Between Pacific Tides:

A border design of these grotesque yet picturesque animals might surround the pen-and-ink representation of a nightmare. Most sea spiders spend part of their tender youth in close juxtaposition to a coelenterate—the larvae, in fact, usually feed on the juices of their hydroid or anemone host…It is especially common among the caves and crevices of Tomales Bluff, Marin County; sometimes half a dozen occur on a single anemone.