Know Your Neightbours: The Last of the Spineless

August-September 1999

This is an article from WaveLength Magazine, available in print in North America and globally on the web.

by Bryan Nichols

Well, that's about it. Over the last seven checklists we covered every group of critters you've seen wiggling around sans backbone on shore and beside your kayak, right?

Not quite. A few groups of invertebrates slipped through the cracks - what about those big prickly things? And that colorful gunk? And those long squishy ..wait-let's learn the lingo shall we?

First off are the simplest of all animals - so simple they are confusing and hard to identify - the sponges (phylum Porifera, small holes). The Caribbean is noted for its huge barrel sponges and those "commercial" sponges Grandma used to bathe with. Northwest sponges are less obvious - most of our species form colorful, felty encrustations, often with tiny volcano-like holes. All of them lack organs or even real tissues - they use specialized cells to pull in water and filter feed very small particles. They grow nearly randomly and don' t move when touched. Are they animals at all? Barely

Much more complex are the Bryozoans (phylum Bryozoa, moss animals). This is a major animal phylum but is almost unheard of by anyone but bionerds, mostly because although they are complex, individual bryozoans are tiny - usually less than half a millimeter. Furthermore, they grow in colonies that look suspiciously like other things, especially hydroids (list#2), corals, sponges and algae. The Northwest has some interesting species though, at least one of which you've seen.

We covered my favorite inverts, the sea stars, way back in list#1. But what about their relatives? Phylum Echinodermata (spiny skin) also includes sea urchins, sand dollars and sea cucumbers, all of which have big, colorful representatives us northwest kayakers see regularly.

Finally, what about our own phylum, Chordata? Feel the back of your neck. Yup, those are vertebrae, so we're not invertebrates. But one somewhat obscure group of chordates doesn't have those bony lumps. Tunicates (subphylum Urochordata, the tail cords) start out embryonic like us - tadpoles with a dorsal nerve and stiff notochord. But their larval stage then attaches itself to the bottom and changes into a two siphoned filter feeder that looks nothing like any other chordate. We call the bigger ones sea squirts and yes, you've seen these distant relatives of yours as well.

So here are ten more notable invertebrates, a grab bag of spineless obscurities and leftover curiosities. Don't hurt their fragile feelings - go out and find them.

Bryan Nichols wonders how many of the invertebrates from the last eight lists you have found and checked off.

Lifelist #8 - Invertebrate Roundup

SPONGES Phylum Porifera V
Various Northwest sponges don't sting like many of their warm water relatives so they can often be (gently) recognized by their felt-like feel. Forming thick, colorful encrustations on rocks and docks, you might also spot the tiny, raised holes where seawater exits their filter feeding forms.

BRYOZOANS Phylum Bryozoa Various
Though most of these guys are difficult to identify without microscopes and considerable dedication, there are a couple that are easy to recognize. The easiest is kelp encrusting bryozoan (Membranipora), colonies of which grow as silvery circles on summer kelps - we've all seen these. There are also fuzzy tree-like ones on floats (Bugula), nifty ones that resemble lace (Phidolopora) and even staghorn bryozoan (Heteropora) which looks remarkably like tropical forger coral. Grab a field guide and good luck

GREEN SEA URCHIN Strongylbcentrotus droebachiensis (spine ball from Drobak)
This familiar critter is a whitish looking ball of short spines, usually with a greenish tinge. It grows to about 8cm in diameter and is common in protected water. Look for it intertidally and even on floats. Urchins are herbivores and roam about peacefully denuding the bottom of seaweed (more or less - some have predatory lapses; who doesn't?).

GIANT RED SEA URCHIN Strongylorentrotus franciscanus (Francisco spine ball)
This is a big, beautiful reddish sea urchin - its skeleton can be 15cm across with 8cm spines. You can spot them nearly anywhere along our coast, sometimes in huge aggregations (called "urchin barrens") that literally strip the bottom of algae. They are taken commercially for their slimy, caviar-like eggs, a delicacy in Japan

PURPLE SEA URCHIN Strongylocentrotus purpurdus (purple spine ball)
This smaller (to 8cm), decidedly purple urchin loves surf - you'll only find them on exposed coastlines. West coast paddlers will recognize it as the urchin that lives in sandstone holes, which it seems to slowly excavate with its spines.

NORTHWEST SAND DOLLAR Dendraster excentricus (not centered tree star) Clean sandy beaches will often have sand dollars - ours are gray or dark red and if alive, will usually stick part of their body above the sand to feed. Think of them as flattened sea urchins with very short spines. A close look will also reveal their relation to sea stars--five leafy "arms" are imprinted onto their round skeletons.

CALIFORNIA SEA CUCUMBER Parastichopus californicus (california row foot) Though it looks like a big worm or worse (no french tickler jokes please), this is also an echinoderm. It is common in protected areas throughout the coast and grows up to a half meter long (and I wouldn't exaggerate about something that shape). They feed with a mop of tentacles that slurps up goodies from the bottom. Oddly enough, specimens taken in winter seem to have no internal organs - they likely absorb them and go dormant.

ORANGE SEA CUCUMBER Cucumaria miniata (vermilion cucumber) Anyone who has paddled the current swept Gulf Islands has seen the ten bright red feeding tentacles of this sea cucumber, which can be abundant in shallow water. The cucumber wedges its body between racks and you can watch each tentacle retract into the mouth as it fills with planktonic food. If you've a passion for sea cucumbers, there are many more--check out Philip Lambert's new book on them (UBC Press).

BROAD BASED SEA SQUIRT Cnemidocarpa finmarkiensis (finmark's fruit with legs) This odd little relative of ours is unmistakable - its 2cm body is a glossy orange red. True to sea squirt form it has two siphons that stick up - disturb it and they will pull down and close. Look for them among rocks when the tide is out.

COLONIAL TUNICATE 8 Various - These are especially confusing as they grow in encrusting colonies and can resemble sponges (which are felty) or bryozoans (which are hard). Look close to see the soft individual tunicates immersed in a shared matrix. Common ones like Aplidium grow as mats on rocks - we often call them "sea pork". Distalpia (mushroom or club tunicate) species are common on floats and rocks. All types come in a variety of colors

Know Your Neightbours: The Last of the Spineless

August-September 1999

Lifelist #8 - Invertebrate Roundup

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