View From On Top: Mine's Bigger Than Yours!

February-March 1997

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

by Richard Martin

Dr. Ruth notwithstanding, size DOES matter. Size is a fundamental quality of organisms and the ability to survive in a given environment depends, in part, on being the 'right' size. Critters come in a mind-boggling range of sizes, from the puny to the downright humungous. Small size carries with it both benefits and drawbacks: on one hand, small critters don't need a lot of food and can make use of teensy shelters and hidey holes; on the other hand, they generally don't live long and are always the last to be picked for sports teams. Bigger is not necessarily better: big critters need more food and cannot easily take shelter-but, then again, they usually have long lifespans and NO ONE beats them up at recess.

Unlike on land, in the sea large size actually makes getting around easier and great weight is not a problem. Because water is about 775 times as dense as air and composed of polar molecules (since the 'O' of H2O has a greater affinity for electrons than the H's, there is a slight charge separation that causes water molecules to 'stick together' like tiny magnets - now aren't you sorry you fell asleep in Chemistry 101?), it is much more viscous than air and much harder to move through. Large critters have much lower body mass to surface area ratios than small ones (due to the cube-square law most of us have forgotten from high school), thereby greatly reducing drag. Water is also buoyant (due to its density), effectively canceling the effects of gravity -which accounts for the lack of Jenny Craig centres in the ocean! The upshot of all this is being big is a virtue in the ocean. By some quirk of biogeography, here in the Pacific Northwest we have a disproportionate number of very large marine creatures. Many of these local giants are, in fact, the world's largest representatives of their taxonomic groups.

Consider the humble barnacle. The familiar form of these crunchy shoe-shredders is usually about the diameter of a human fingernail and generally regarded as about as interesting. But barnacles are actually really neat critters. Although they look kinda like a mollusc, they are actually crustaceans-basically tiny crabs mounted on their butt-ends inside a little limestone tee-pee. This 'tee-pee' usually consists of eight plates of calcium carbonate and, unlike the shell of snails, is permanently stuck to the substrate (rocks, wharf pilings, boat hulls, etc.); the glycoprotein 'glue' that keeps barnacles firmly attached works so well in wet environments it is being studied as a way to help dentists devise better ways to keep fillings from coming loose. Barnacles are filter feeders, their six pairs of long jointed legs (their class name, Cirripedia means 'feather feet') extend from the shell to rhythmically kick planktonic food and detritus into their shells, there to be eaten. Barnacles come in a variety of forms, from the familiar acorn barnacle, to the rubbery-stalked goose barnacles, to the highly specialised parasitic forms that grow on whales (a single humpback whale may carry up to half a tonne of barnacles), sea turtles, and even sea snakes. Well, the Pacific Northwest is home to the World's Largest Barnacle, the giant acorn barnacle (Balanus nubilis), which frequently reaches a diameter of 13 to 15 centimetres and when crowded (especially in deep water) can reach a length of over 30 centimetres (12"). The empty limestone shells of giant acorn barnacles are sometimes cast ashore during winter storms, and are so large they make excellent pencil-holders.

And if all this isn't enough for you to appreciate these nifty critters in a new light, consider that barnacles are also the 'best hung' of any animal on this planet. Really! Because they are permanently attached to the substrate, barnacles can't go cruising for sex partners, so they've developed organs of both sexes, including an enormous, hyperextended penis up to 11 times the length of the rest of the animal (a human male similarly endowed would have a penis 22 metres long! Marine biology is a humbling pursuit.). To prevent self-fertilisation (which is illegal throughout most of the Pacific Northwest), male and female organs are usually not functional at the same time in any given individual. When a (functioning) male barnacle is 'in the mood', he simply extends his whip-like schlong to reach over to the nearest mature female barnacle, pokes inside and releases his sperm. The female barnacle, being as firmly attached as the male, cannot run away. But she's not completely helpless, either. Barnacles have a pair of sharp plates on top that can be closed tightly. This is primarily an adaptation that allows barnacles to avoid desiccation while exposed at low tide, but may also serve as a way for female barnacles to prevent unwelcome males from entering. If he does not withdraw his probing member quickly enough, a male barnacle is likely to experience the "unkindest cut of all" (funny, you don't LOOK Jewish!).

As I said, the Pacific Northwest is home to a lot of fascinating giants. I could describe each and every one of them in loving detail, but space restrictions demand that I keep things brief. Toward that end, consider the table below

I think you can see I've made my point (perhaps ad nauseam): we DO have a lot of really big animals living in our waters. But from a biological perspective, it is much more interesting to speculate WHY so many giants live in the waters of the Pacific Northwest. In solving this puzzle, three factors seem likely to be particularly important: 1) our waters are very cold, typically hovering year-round at a goosebump-inducing 8 to 10 degrees Celsius, 2) our waters are very nutrient-rich, and 3) large body size helps retain body heat. Let's look at each of these in turn.

Temperature is one of the most potent forces in biology, influencing everything from ecosystems to individuals. In cold environments, the complex choreography of biochemical reactions which sustain life is significantly slowed down; this results in longer lifespans and thus (given a longer period for growth) greater overall size. In addition-and of particular importance for gill-breathing critters-cold water can hold more than four times the dissolved oxygen that warm water can. On the 'down side', cold water also induces what Seinfeld's George Costanza called "shrinkage", but I digress ...

The oceanic currents which well upward against the continental slope bring nutrients from the deep waters to the surface, where they can be used by photosynthetic organisms like diatoms, dinoflagellates, and kelp. This 'kick starts' local food webs by providing food for copepods and other zooplankters, which in turn are eaten by bivalves and small bony fishes, which are fed upon by larger bony fishes, cephalopods, pinnipeds, sharks, and killer whales; the byproducts of all this feeding, in turn, provides food for crabs, shrimps, starfishes, sea cucumbers and other scavengers or detritus feeders. Baleen whales circumvent this whole gastronomic drama by feeding directly on the plankton, which exists in such profusion in part because of the nutrients borne on upwelling currents.

Water has a high heat capacity, and can therefore conduct heat some 20 times faster than air. Since nerves, muscles, and other tissues function best at warm temperatures, it behooves marine organisms to retain as much metabolic heat as they can. One of the most expedient ways to do this is by attaining large size: because volume increases as a cube of dimension and surface area as a square, a big organism has a large quantity of tissue to produce body heat but only a relatively small amount of surface area from which to radiate it. Hence in large animals, heat production is typically faster than heat loss.

There are almost certainly other factors involved that help account for the large size of Pacific Northwest marine creatures, but at present these are only poorly understood. In the mean time, take pride in the fact that many our sea critters are larger than anyone else's. Bigger may not be better in any absolute sense, but the giants of the Pacific Northwest certainly help make living here all the more spectacular and awe-inspiring.

A word to the wise, though: paddle with respect. Richard Martin is a Marine Educator & Consultant and a regular WaveLength columnist. He can reached by email at rmartin@direct.ca

GIANTS PACIFIC NORTHWEST MARINE ANIMALS

Animal

Claim to Fame

Size

Giant Acorn Barnacle Balanus nubilis

Largest Barnacle

15 cm across30 cm tall

Weathervane Scallop Pecten caurinus

Largest Swimming Scallop

25 cm across

Dungeness Crab Cancer magister

Most Valuable Crab

30 cm across the carapace

Puget Sound King Crab Lopholithodes mandtii

Largest Lithode Crab

30 cm across the carapace

Basket Starfish Gorgonocephalus eucnemis

Largest Brittle Starfish

30 cm across

Orange Peel Nudibranch Tochuina tetraquestra

One of the Largest Nudibranchs

30 cm long

Rainbow Nudibranch Dendronotus iris

Another of the Largest Nudibranchs

30 cm long

Moon Snail Policines lewisii

Largest Bubble Shell

15 cm shell, 35 cm long

Gumboot Chiton Crytochiton stelleri

Largest Chiton

46 cm long

Plumose Sea Anemone Metridium senile

Largest Sea Anemone

51 cm tall

Geoduck Panopea generosa

Largest Burrowing Bivalve

25 cm long shell, 91 cm siphon

Sunflower Starfish Pycnopodia helianthoides

Largest Echinoderm

91 cm across

Chinook Salmon Oncorhynchus tshawytscha

Largest Salmon

147 cm long, 57 kg

Pacific Halibut Hippoglossus stenolepsis

Largest Flatfish

244 cm long, 205 kg

Giant Pacific Octopus Octopus dofleini

Largest Octopus

350 cm long, 54 kg

Stellar's Sea Lion Eumetopias jubatus

Largest Sea Lion

370 cm long, 1000 kg

White Sturgeon Acipenser transmontanus

Largest Anadromous Fish in N. America

610 cm long, 818 kg

Northern Elephant Seal Mirounga angustirostris

2nd Largest Pinniped

650 cm long, 4000 kg

Great White Shark Carcharodon carcharias

Largest Predatory Fish

714 cm long, 2730 kg

Killer Whale Orcinus orca

Largest Dolphin

762 cm long, 5450 kg

Basking Shark Cetorhinus maximus

2nd Largest Fish

980 cm long, 9000 kg

Giant Squid Architeuthis japonica

Largest Invertebrate

1737 cm long, 1000 kg

Sperm Whale Physeter macrocephalus

Largest Predator

1800 cm long, 55000 kg

Blue Whale Balaenoptera musculus

Largest Animal

3300 cm long, 120000 kg