Friday, July 14, 2017

Eyes Under Puget Sound: Critter of the Month – The Ice Cream Cone Worms

I scream, you scream, 
we all scream for ice cream!  
(Don't worry, worm shown above is not
actual size; ice cream cone 
are only about an inch long!)
Summer is here, and what better way to beat the heat than to cool off with a nice refreshing frozen treat? We think this month’s group of critters, the Ice Cream Cone Worms, are some of the coolest creatures around…although maybe not quite so delicious as the real thing!

Ice ice baby

Ice cream cone worms (belonging to the family Pectinariidae) are easily recognized by their distinct
cone-shaped tubes that can be up to 5 cm (2 inches) long. Here in Puget Sound we find two species of these ice cold beauties - Pectinaria californiensis and Pectinaria granulata.

Although both of these species are widespread throughout the Sound in depths up to 230 meters, Hood Canal is where we encounter them in the highest abundances - we can sometimes get over 30 of these critters in a single benthic sample!

Lashing out

Another distinct feature that sets pectinariids apart is a pair of glistening “eyelashes” protruding from the tops of their cones. These spiky eyelashes are actually hardened hairs, called paleae.

The paleae may look pretty and delicate, but they serve a practical purpose – to help the worm burrow head-first into the sediment.

Everybody poops

A Pectinaria granulata specimen, removed from its tube
 to reveal its translucent body with visible sediment inside.
Ice cream cone worms spend most of their time face-down in the mud, with the pointy ends of their tubes turned upright sticking out just above the sediment’s surface. This allows them to use their tentacles (located near the paleae) to search around in the mud for large particles of sediment to ingest.

This strategy of picky eating is called selective deposit feeding. Anything the critter can digest that attaches to the particles gets absorbed by the worm’s gut.

The sediment grains they can't digest basically go in one end and out the other. The passed material is called pseudofeces - meaning “false poop”. It can take up to six hours to make its way through the worm’s body and out the open end of the cone. If you were to observe a living ice cream cone worm without its cone, you would be able to see this whole process through its translucent body wall.

Go your cone way

If you’re looking for ice cream cone worms, chances are you can find them in areas with a higher sand content (versus rock or fine clay). This makes sense when you think about how they build their cones.

Pectinariids construct their cones by reaching out with their tentacles to collect sand grains, shell pieces, or other small particles. These grains are tightly placed together in layers, giving the cone a smooth but speckled appearance, almost like a colorful stained glass window or a tile mosaic. The cone protects the critter, housing the animal’s soft, fleshy body in a speckled coat of armor.

A worm’s place is in the cone

A comparison of the tubes of P. granulata and P. californiensis shows the 
difference in preferred grain size between the two species.
Some pectinariids prefer large grains over small grains for tube-building, which makes it easy to tell those species apart if the cone is still intact. This is quite convenient for us taxonomists!

For example, P. californiensis chooses fine sediment granules for its straight, delicate tube, while P. granulata prefers coarser sediment for its robust, slightly curved tube. If the worm doesn’t have an intact cone, it can still be identified by the color and shape of its paleae – P. californiensis has copper-colored paleae with fine tips, and P. granulata’s are golden-colored, with blunt tips.

P. granulata (left) has blunt-tipped, golden paleae while P. californiensis (right) has fine-tipped, copper-colored paleae.

 By: Dany Burgess & Angela Eagleston, Environmental Assessment Program

Critter of the Month

Our benthic taxonomists, Dany and Angela, are scientists who identify and count the benthic (sediment-dwelling) organisms in our samples as part of our Marine Sediment Monitoring Program. We are tracking the numbers and types of species we see in order to understand the health of Puget Sound and to detect any changes over time.

Dany and Angela share their discoveries by bringing us a benthic Critter of the Month. These posts will give you a peek into the life of Puget Sound’s least-known inhabitants. We’ll share details on identification, habitat, life history, and the role each critter plays in the sediment community.

Can't get enough benthos? See photos from our Eyes Under Puget Sound collection on Flickr.

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