Thursday, August 02, 2007

Update on egg cases

I'm still looking for an ID on those egg cases we found on Boundary Bay beach.

In the comments on my last post, Hugh Griffith, of Lulu Island Blog, suggested that they may be lugworm (Arenicola) egg cases.

Back to the books and Google.

My books on seashore life mention lugworms, of course, and show photos of them and their fecal castings. None of them mention egg cases.

"Cake decorator" fecal castings.

Wikipedia does. But they are described thusly; "The ova are enclosed in tongue-shaped masses of jelly about 8 in. long, 3 in. wide and 1 in thick. Each mass is anchored at one end." Hmmm. "Ours" were about 3 - 4 inches long, 2 wide, equally thick. More pear-shaped than tongue-shaped.

CalPhotos has a photo of an egg case of Arenicola brasiliensis . It is similar to the ones we found, although the size is not given. But this one was found in California at a depth of 15 metres. Ours, even at high tide, must not be under more than a metre of water.

mentions three species that are found on this coast, Abarenicola pacifica, A. claparedii oceanica and A. c. vagabunda. Googling these, I get all kinds of info on their cell structure and chemistry, nothing about egg cases. No photos.

Anyhow, given that the lugworms do create large egg masses and that the beach in Boundary Bay is covered with their fecal castings (curlicue mud-poops, Hugh calls them), I think we can be fairly confident that these are produced by one of our local varieties of lugworm.

Thanks, Hugh!

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