Mysteries at the Tideline

by Philip Lambert, Curator of Invertebrates, RBCM.

 "Any idea what these are?" Nestled in the palm of a colleague's hand were several oval pieces of clear, firm jelly. "They were washed up on the beach along Dallas Road." Usually, I have some idea what mystery items are, but this time I was stumped. They were shaped like a small, heelless slipper, about the size of a quarter, and consisted of a firm, crystalline jelly covered in bumps.

Several days later, I was browsing through a journal, when suddenly, there they were! Our specimens were the remnants of Sea Butterflies – the bodies (minus their eight-centimetre wings) of animals that usually swim near the surface of the open ocean.

If you stroll along beaches between Victoria and Port Renfrew on Southern Vancouver Island, eventually you will discover an open-ocean mystery object. The winter can be the best time, especially after a big storm combined with a low tide. Then, animals normally attached out of sight in deep waters get uprooted and deposited high on the beach.

Like the Sea Butterfly, another organism that gets washed ashore in the stormy season is the Purple Sailor, a colonial animal made up of many polyps surrounding a clear, stiff vertical sail. By regulating their buoyancy, the animals can expose more or less sail to the wind and migrate great distances. However, in a storm, the strong winds overpower them and drive them ashore we sometimes find thousands of them, in long drifts on the upper beach, recent strandings that still retain their bright purple rims.

Beachcombers commonly find mysteries that are types of sponges. One shaped like a hand, is aptly named Deadman's Fingers and another, the Hermit Crab Sponge, is a smooth, rounded orange ball with a hole in one side. This sponge first grows around a hermit crab's shell and then gradually dissolves it. The result is a hermit crab living inside a sponge instead of a shell. You may also find evidence of another sponge when you discover an unusual "rock" perforated with holes. A bright-yellow Boring Sponge  bores into the Purple-hinged Rock Scallop, creating a labyrinth of holes and tunnels in its shell. When the scallop dies, the surf tumbles and erodes the shell, creating a cinder-like rock. But the scallop "rock" usually has a splash of purple near the hinge and is usually more white than gray.

Lots of seaweeds wash ashore to form windrows, which are quickly broken down and recycled by sand fleas and other small critters. But some seaweed, made mostly of calcium carbonate, do not decompose as easily. The skeletons of coralline algae look like white-segmented bushes; in the living plant, a thin layer of pink cellular tissue surrounds this hard core. Other species you may find are colonial animals. The hydroid, for example, in life looks like a small bushy plant, but a closer view reveals hundreds of tiny polyps like small sea anemones, emerging from vase-shaped receptacles that branch out from the central stalk. All the polyps connect internally, and food gained by one is shared with the colony.

If you are lucky, you might find a Mermaid's Purse. The cartilaginous fishes, called skates produce a leathery pouch in which a yolky egg is laid. The purse has tendrils at the corners that anchor it, but in rough seas, it may be dislodged and cast ashore, to the detriment of the embryo inside.

The sand collar of a moon snail has stumped many a beachcomber. Moon Snails lay their eggs near low tide on protected sandy beaches, in places like Parksville on Vancouver Island. Using their massive foot as a mold, they create a sandwich of eggs between two layers of sand, glued together by mucus. The result is a rubbery collar reminiscent of a toilet plunger. As one person remarked, "I was sure it was a man-made object."

I remember someone insisting they had found part of a lobster on a beach in the Gulf Islands. While lobsters are not native to the West Coast, an escapee from a restaurant live-tank was a possibility. But on inspection, it turned out to be a decomposed Gumboot Chiton - its overlapping plates resembled the segments in the tail of a lobster. Another mystery solved.