The crabs are molting, the crabs are molting! Last week at Prison Rocks, divers noticed a plethora of Dungeness crab (Metacarcinus magister) carapaces. Pictured above is one that Chris brought back to the College and below is a photo that Malou took underwater of a live crab.
Tuesday morning, 11 am, F block first year Marine Science students explored Weir’s Beach. Not many photos to mark the occasion, but two great ones thanks to Adva.
Below is the moult of a first instar juvenile Dungeness crab, Metacarcinus magister.
After a question from Johan about ‘weird, somewhat disgusting, sea snake/fish slithering around the surface’ at night and from Max (Dock worker extraordinaire!) about ‘long skinny creatures’ ranging in size from 6″ to 1′, I thought I better go investigate…
Max also sent the photo above and the two below:
These creatures are what I learned as Nereis brandti but are now called Alitta brandti. Learn more about these giant pileworms from:
Alitta brandti at Encyclopedia of Life
Nereis (Neanthes) brandti at Invertebrates of the Salish Sea
Alitta brandti at World Polychaete Database
On Sunday 2 June we hung a light off the Pearson College dock which attracted many, many megalopae (Dungeness crab, Metacarcinus magister). Periodically a worm would also be attracted to the light.
I did pester a few of the worms and they released big clouds of sperm. The reproductive strategy is called epitoky where the posterior end of the polychaete worm is transformed into a bag of gametes (either sperm or eggs). The epitokes swarm at the surface and then explode to release the gametes. Crazy but cool!
While the students deserted us on 24 May, the Pearson College dock has thousands (maybe hundreds of thousands?) of visitors right now. The final larval stage of the Dungeness crab (Metacarcinus magister) is called a megalopa and there a many, many megalopae swarming around the dock.
On the dock, there are also thousands of juvenile crabs scrambling around. The megalopae molt and metamorphose into the benthic juvenile stage seen below.
There are also many megalopae and juveniles on the succession substrates that students put in the water in September 2012.
And Ivan thought nothing was using his wire!
Pearson College Marine Science 