What is an invertebrate?
The word invertebrate refers to any animal that does not have a notochord, or backbone. Invertebrates are incredibly diverse. There is just one phylum of vertebrates (animals with backbones), and there are 34 phyla of invertebrates.
Pacific Marine Invertebrates
Pacific marine invertebrates can be divided into a number of major groups and inhabit both intertidal and subtidal zones. They have been around for a very long time, some as long as 500 million years. Despite this, we know scarcely little about some of the most abundant animals on our planet.
Invertebrate of the month: The rainbow sea star
The rainbow sea star, Orthasterias Koehleri, is a large, growing to a diameter as large as 50 cm. It usually occurs at greater depths than the Pisaster Ochraceus, although at low tides in the summer, lucky beachcombers can be rewarded with a sighting of this colourful species.
They are characterised by a small central disc and long slender arms covered in white spines, which are surrounded by rings of tiny pincer-like organs called pedicellariae. Like other sea stars, Orthasterias is a predator that feeds on a variety of other invertebrates such as gastropods, limpets, bivalves, chitons and barnacles. Much like Pisaster, it can also evert its stomach and insert it into the animal, excreting digestive enzymes onto its tissues. They are also known for their ability to dig clams out from muddy bottoms. They can also regenerate their arms, as long as their central disc remains intact. See them on our T-shirts here.
Sea star wasting disease
July 2013 marked the beginning of a mass die-off of various species of sea stars off the Northwest coast of United States and the West coast of British Columbia. The source was unknown, and was given the name "sea star wasting disease". The cause is not yet fully understood, and it is believed to be the result of multiple factors, including climate change, and oceanic warming in particular. The species most affected is the sunflower sea star, the world's largest. It has seen it's numbers reduced by between 80-100% over a range of roughly 2000 km. There have been sea star wasting events in the past, but nothing on this scale, and with such large mortality. It is a reminder that marine invertebrates are just as vulnerable to the effects of climate change and environmental degradation as other marine species.
Find out more about sea star wasting disease here.
Find out more about invertebrates