by Philip Lambert, Curator of Invertebrates, RBCM

 

I placed my hand on the taut cable, feeling for tell-tale bumps and twangs, indicating that the trawl was skimming the bottom 1000 m below. I braced myself as the deck dipped and heaved with the unseen swells coming at us from the blackness. The horizontal rain pelted the back of my raingear. A few more minutes and I would signal the winchman to bring in the last trawl sample before the ship headed for shelter. Five minutes seems like an eternity in these conditions. On cue, the winch whined into action and began the slow retrieval, the cable twanging and jerking as it seated into the grooves on the spool of cable. Half an hour later our eager crew was hunched over the catch picking out specimens and sorting them into various buckets. But word came down from the captain that we had better hurry up and stow everything.

 

Hurricane force winds were in the forecast. We never made it to shelter that night, the ship had to heave-to in the middle of Dixon Entrance facing into the hurricane force winds. It was probably one of the longest nights I have spent on a ship. But boy, did we get some neat stuff on that last haul!

 

In this day and age of high-tech it may seem archaic to be using essentially the same gear that the Challenger expedition used in 1872 but it works. Most of the deep water specimens in our invertebrate collection were acquired in this way. The rest have been picked up by hand with the aid of scuba. With each specimen,

another spot can be placed on the map of a species’ distribution. We now have about forty-five thousand jars, each one representing a distribution point on a map of BC. These are the raw data we use in writing authoritative, up to date handbooks on various taxonomic groups, like the revised edition of my book on the sea stars of British Columbia and Southeast Alaska (see Reference).

 

The animals I have been studying and collecting for 25 years are more than just dots on a map, however, they have their own curious personalities and habits. Sea stars are mostly hunters and carnivores at the ends of their particular food chains. As adults, few predators will eat a sea star, except perhaps other stars. Filter feeders and planktonic predators, like jellyfish, harvest thousands of planktonic sea star larvae, thereby controlling their population numbers at this early stage in their life histories. Only a small fraction make it to the tiny juvenile sea star stage and they are still not safe from harm. But many can take care of themselves, thank you very much. The Slime Star produces vast quantities of a viscous mucus that repels many would be predators. But there is a bit more to this than meets the eye.

The Slime Star Pteraster tesselatus

Spewing mucus onto the skin would normally suffocate the small finger-like gills protruding through pores in the body surface but the Slime Star has evolved an ingenious extra skin supported on the tops of spines like a canvas awning. Mucus is secreted on the outer surface of this layer leaving the gills free to exchange oxygen with a current of water brought in by the sucking action of this inflatable covering.

Sunflower Star Pycnopodia helianthoides

   Juveniles of the Sunflower Star, when bothered by some bigger bully, will readily drop off an arm or two, if it will help them to get away. We often find them with arms at various stages of regrowth. This same species, when it grows up, is the scourge of the deep, reaching a maximum diameter of about one metre and devouring just about anything that gets in the way. Of course, having no eyes, this can be a hit and miss affair, but using its keen sense of smell this sea star can home in on food sources from great distances. If you have ever used a crab trap you have, no doubt, been blessed with one of these babies hogging the bait. But over millions of years, prey species have adapted to predators like these. Each tries to keep one step ahead of the other by evolving new escapes or new attack methods. The abalone can accelerate out of danger and outrun an oncoming Sunflower Star, the California Sea Cucumber writhes and flips itself out of danger, and the Swimming Scallop jets away, leaving this predator to snare those few that are a bit slow off the mark.

A Swimming Scallop preparing to escape from a Sunflower Star

 Anyone who dives has probably seen those flat gravelly areas that resemble a field of miniature bomb craters where this predator has excavated and devoured clams.

The Mottled Star Evasterias troschelii devouring a bivalve

These are just a few of the forty three species described in detail in my new handbook on sea stars. The book covers the geographic area from Glacier Bay in Southeast Alaska south to the waters of Puget Sound and out to the edge of the continental shelf at a depth of 200 metres. Another twenty-six species occur farther out on the continental slope below 200 metres and 14 more species have been collected just to the north of Glacier Bay or south of Cape Flattery and in time, may turn up in trawls or dredges within the books coverage. No wonder Walter K. Fisher stated in his 1911 monograph that “ the west coast of North America is more prolific in species and individuals than any other portion of the world.”

 

Purple Sea Stars Pisaster ochraceus

 

 

Article first published in  Discovery: News and Events from the Royal British Columbia Museum 28: 1-2 (2000).  Photos: Copyright RBCM.



Reference

Lambert, P. 2000. Sea stars of British Columbia, Southeast Alaska and Puget Sound. Vancouver and Victoria: UBC Press and Royal BC Museum.