Saturday, March 25, 2017

A wormy post

Marine biologists count some 67,290 species of sea worms. (I checked each wormy page on this site and added them up.) And with millions - trillions - of individuals of the more prolific species, no wonder I find worms everywhere I look!

These were waiting out the low tide in the shelter of loose rocks on the Tyee Spit shore.

Shiny, multicoloured polychaete

I find these in the sand underneath the rocks, rarely on a rock or stone. They are shy and quick; mostly, if I look first at the rock, then at the sand, all I see is the last few segments of the worm squirming down underground. The only way to get a photo is to hold the camera ready and aimed, then lift the rock.

Their mouths vary depending on their diet, since the group includes predators, herbivores, filter feeders, scavengers, and parasites. Most have a pair of jaws and a pharynx that can be quickly turned inside out, allowing the worm to grab food and pull it into the mouth. (MESA)

There are 12,000 species of polychaetes. My encyclopedia lists 44 more or less free-living polychaetes in the Pacific Northwest.

A Mud nemertean, Paranemertes peregrina, and something green in a long tube.

Paranemertes, aka the Wandering ribbon worm, or the Restless worm, is easy to identify. It's a long ribbon, up to 25 cm. long, with a purple back and a creamy belly, usually found wandering alone, searching for its dinner: other worms, even worms much larger than itself.

On contact with nereid prey, P. peregrina pulls its head back and everts its light-colored proboscis, which wraps around the prey.  The prey is soon paralyzed, ...  P. peregrina then swallows the nereid.  After feeding it follows its own slime trail back to its burrow.  It eats about one prey worm per day ... (WallaWalla.edu)

I can't identify the green worm in the long tube, other than to guess that it's another ribbon worm.

A typical squirm of green ribbon worms, Emplectonema gracile. And a lone, brown flatworm.

The green ribbon worms are gregarious; where you find one, there are probably several more entwined with it. It eats barnacles, mostly the small acorn barnacles, slithering into cracks or the open mouth of the barnacle, using a poisonous needle-like stylet* to paralyze its prey. (That isn't going anywhere, anyways, but you never know.)

The flatworm also eats barnacles, and is so thin and flexible that it seems sometimes to be simply a brownish coating on the barnacle it's attacking.

In this photo, I've been puzzling over a perfect circle in the bottom of an empty barnacle shell. (Just above the flatworm.) It looks like the edge of one of those finger cots that I use instead of bandaids. A short worm, maybe? A mini Ouroboros?

*Photo of the stylet, here, at the bottom of the page, Row 1, on the right.

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