Apr 23, 2009

Of Hydrophobicity and Ambulation

Here's today's buzz word: hydrophobicity, the property of being water resistant. Some spiders, when placed on the water's surface, simply get wet and sink. But many are hydrophobic to some extent and can ambulate across the water's surface much like they do on land. Still others, like those in the family Pisauridae, can row across the water. But all spiders, when placed upon the surface of a human soul, can devour it.

I'm guessing that this spider belongs to the family Lycosoidea. Anyone care to confirm or correct?


Joe Lapp ("Spider Joe") said...

This is a nursery web spider, family Pisauridae. The Lycosids (wolf spiders) have two large forward-facing eyes, which this one doesn't have. This one is likely in the genus Dolomedes, the fishing spiders.

Where are you getting the hydrophobic/hydrophilic business with spiders? My understanding is that this is a surface tension issue, with the distribution of hairs maximizing surface tension. It's not an issue of whether water sticks to the spider. Water hardly sticks to any spider; they're all hydrophobic, otherwise they'd drown in the morning dew.

Fishing spiders have to dive fast into the water to catch prey, such as small fish. Sinking is something they need to do very well for survival.

This family of spiders is also known for hairs that allow woodland dwelling species to slowly glide to the forest floor, unharmed by the fall.

You missed the opportunity to title the post, "Hairy walking on water."

(I teach people about spiders in Austin, TX.)

Raging Wombat said...

Spider Joe: I got my information from the link I included in my post.

Thanks for the correction(s).

Joe Lapp ("Spider Joe") said...

I gotcha. That link is to a google search, and you appear to be pulling your information from the abstract of the first search result. Most of the other search results focus on the issue of surface tension, though there is also mention of a water-repellent "waxy coating" on the surface of the Pisaurid legs.

I spritz spiders in jars and find that the water beads up on pretty much all of them. It's curious that some spiders simply sink when dropped in water, according to that first article. My suspicion is that the authors of this first article need to tease out the interplay between hydrophobicity and morphology-generated surface tension.

Meantime, I'll keep an open mind about how much this is due to hydrophobicity and how much is due to morphology. Thanks for the bit of education.

Jack Ruttan said...

Pritty pictcha!