Know Your Neighbours: Bugs That Don't Bite - Crustaceans
June-July 1999
This is an article from WaveLength Magazine, available in print in North America and globally on the web
by Bryan Nichols
I loathe bugs with wings. Mosquitoes and midges make me mad and flies fill me with fury.
Class Insecta can make even the most hardcore environmentalist consider the merits of noxious insecticides. While insects are very successful on land, in our beloved oceans they are less than scarce. Their salty relatives-crustaceans-are the bugs of the sea.
I love sea bugs. Shrimp, crab and lobster can make even the most hardcore vegetarian want to crack their armor and consume their flesh. But let's look at sea bugs from a more peaceful perspective.
Taxonomy (What are they and who are they related to?)
They are arthropods (Phylum Arthropoda) which are relatively easy to define, especially considering they belong to the largest phylum of all. Just think of every thing that has hard, jointed legs. From minuscule no-see-ums through black widow spiders to four meter spider crabs, this phylum is immense and diverse but they all have jointed legs. In the ocean, you are almost always dealing with Class Crustacea, the familiar crustaceans.
Anatomy (How do they work?)
An external "skeleton" made of chiton has allowed these critters to conquer most of the world's environments. Serving well as effective body armor, it does however, make growing bigger a bit awkward. Crustaceans usually go through odd looking, nearly microscopic larval stages that drift throughout the ocean. Once in their recognizable adult stage they still have to "shed" their hardened exoskeleton to grow. We call it molting and often find the old "skins" washed up on beaches, looking remarkably like dead crabs or shrimps.
Ecology (What do they do?)
Many are effective scavengers, well suited to roaming about and feeding as the opportunities arise. You'll find small crabs on rocky shores, shrimps along docks and pilings, big dungeness crabs in muddy bays. Barnacles are a notable exception-they fasten their heads to solid objects and filter feed with their feet.
This month's checklist has ten crustaceans to look for on your kayak trips. They might look like big bugs, but you'll be more inclined to eat them than swat them.
Lifelist #7 - Biteless Sea Bugs for Northwest Kayakers
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Acorn Barnacle Balanus glandula (acorn acorn?) This is one of those ubiquitous barnacles that form a white line at higher tide levels. They can only open and feed when submerged or splashed but most seem to be high up-why? Because up there the voracious snails and sea stars have trouble getting at them
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Goose Barnacle Pollicipes polymerus (many pieced ?) This species can be truly beautiful-ravishing reds, banded feeding cirri and ivory to plates. Unlike most barnacles, they grow 8 cm on a stalk and you'll find them only where there is wave action (or extreme currents). They close up as the surf pounds and then feed by holding out their legs as waves wash off the rock.
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Coonstripe Shrimp Pandalus danae (dana's glowing) Shrimps of this genus are popular on Northwest dinner plates. They taste so good it makes me wonder why we never eat other bugs like grasshoppers. Look for live shrimp on docks and pilings-their clear bodies are at tractively marked with reds and whites. You'll probably spot the long, banded antennas waving around first.
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Hermit Crab Pagurus spp (a Latin crab) Snail shells that walk around on jointed legs aren't snails at all, of course. After the original builder and owner has expired and rotted away, hermit crabs will move in. Their soft abdomens would be vulnerable without the protection. There are a couple of common intertidal species-one hairy looking, one smooth. We've all seen ehemgently pick one up and have a closer look. If it is getting too big for its shell it won't be able to hide its head-you might be able to stare fondly into emerald green eyes
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Purple Shore Crab Hemigraspus nudus (naked halfgrabber) Every kid knows these-lift up a small rock on many of our more exposed shorelines and oodles of them will scatter. They come in a variety of colors but usually have dark spots on their claws. Formidable as their pincers seem, they are vegetarians-they eat Ulva, the green algae that grows intertidally
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Red Rock Crab Cancer productus (leading crab) This is the large crab you're likely to see roaming around just below your boat, whether you're over rocks or sea grass or whatever. Growing to about 15 cm max, they have thick dark red shells protecting their tasty muscles underneath.
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Dungeness Crab Cancer magister (master crab) This crab is well known to seafood lovers, of course-it gets to be twice as big as the similar red rock crabs but prefers deeper water in muddy bays and sea grass beds. It can bury itself in mud and uses its claws to open young clams. Outside of crab traps, paddlers are most likely to see it while cruising over eel grass beds at low tide
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Decorator Crabs various A number of different types of spider crabs actively encourage other critters to grow on their backs and legs. Spider crabs have spindly legs and small claws, but they may be nearly completely overgrown by algae and colo nies of sponges, bryozoans and even stinging hydroids. This makes for nearly perfect camouflage-often you will only spot them when a bit of the bottom starts walking away.
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Kelp Crabs Pugettia producta (leading puget) This is a big (to 10 cm), clean living spider crab usually found clinging to kelp. Pull up some big fronds of bull or giant kelp and you might well end up with one of these nifty looking crabs on your sprayskirt. Their backs and legs often match the color of the kelp exactly, with a more reddish tinge underneath.
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©Bryan Nichols 1999 No reproduction without permission of the author
Bryan Nichols(brynance@pacificcoast.net) left the forest to take up marine biology after discovering rum tasted far better than Deet.
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