I started this blog with some posts about the marine biology of Vancouver Island. I was impressed by the rich underwater life of this part of Canada. That was before I could dive. So last summer we revisited the island. I made 10 dives, 3 snorkeling trips and did some beachcombing.
I hoped for a lot of new species and to do something I dreamed about since 1976: diving in an underwater forest of kelps. To be honest: I already had been diving in kelp forests last year in Ireland and in May in France. But this was different because of the size of the kelp forest. I dived at three spots in the vicinity of Nainamo: Cottam Point, Tyee Beach and Neck Point. The fourth divespot was Rock Bay (40 km north of Campbell River).
My first dive was special. I expected clear water, as I could remember of my trip in 2008. It was not. A bit of a disappointment, but the number of species of sea stars made my day: 12 species in total! That's why I start with a post about sea stars.
This is the vermilion star, Mediaster aequalis. Up to 20 cm across. It is an omnivore: it feeds on sponges, bryozoans, loose algae, detritus and dead animals.
Membranipora serrilamella in detail, showing the honeycomb like structure and individual polyps.
I took this leather star of five-ribbed kelp, where it was feeding on the before mentioned bryozoan.
Solaster dawsoni, the morning sun star. It can grow up to 40 cm in radius. This is a juvenile.
It is a 'top predator': it feeds on a lot of sea star species, including other morning sun stars. A cannibal, but that is not so unusual in marine species. Lambert (2000) on attacking its own species: 'but its success rate is low because of a well developed escape response. S. dawsoni bends its arm back and pushes the attacker off while rapidly moving away (10 cm/min.).'
He does not mention the morning sun star preying on the California sea cucumber, Parastichopus californicus (left on the photo above), but mentions that it swims away when contacted. Sea cucumbers are related to sea stars, the primal food of this sea star. And as other sea stars are preying on sea cucumbers, I am in no doubt he is also preying on them.
A whole lot of information in this post comes from this book, as well as their identification. For sale at a very reasonable price of $26. Highly recommended.