Membranipora serrilamella, Kelp-encrusting bryozoan
Bird's-eye view of the walls.
Where the colonies don't compete with others, they form almost perfect circles. If you look closely, you can see the bump of the tentacles at one end of each "brick".
In the water, the rolled edge of the kelp allows a side view of the tentacles, one tube with a spray of tentacles per case.
Some colonies of Membranipora, after being taken out of the water, have what look like little lumps of jelly of about the same color as the colony. If the colony is submerged in clean sea water and examined with a strong hand lens ... the little blobs may prove to be one of the marine zoologist's delights, Doridella steinbergae.The accompanying photo showed Doridella and its half-circle egg masses. And I remembered seeing tiny white semi-circles among the bryozoans; I should have been paying attention, but I was looking for unblemished colonies.
The kelp was in my aquarium. I fished it out and spread it full length in shallow water. Oh!
Another cluster of egg masses.
I poked this one with a plastic toothpick, and it woke up and started to crawl over the kelp. It's about as fast as a land-based slug. Here it is, crawling onto a bryozoan colony:
The two white ear-like protrusions on the front end are sense organs, the rhinopores.
Most nudibranches have prominent gills at the back, but as part of this one's camouflage, the gills are hidden underneath a flap of skin. Another nudibranch, the Corambe pacifica, also feeds on the kelp bryozoan; it is almost identical to Doridella, except that its gills show through a small notch at the tail. Photos for comparison: Doridella, (They call it Corambe steinbergae here.) and Corambe pacifica. The C. pacifica lays its eggs in a spiral, which helps with the identification.
In my search for information, I came across a great blog, Biological Tales from the Brine Queen. In her post on this sea slug, she writes,
They feed on Membranipora by creating a suction seal, using their rasping tongue (called a radula) to cut through the outer membrane, then they suck out the insides.And they leave the bryozoan colony with bare patches and irregular edges. Which is why I missed them on the first photo shoot.
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Really enjoying the posts, Weeta! This is the kind of observation and analysis I'd love to do, if only I lived near the ocean.
ReplyDeleteThanks, Tim.
ReplyDeleteWe're not all that close; a 20 minute drive from the beach. It helps to have set up a small saltwater aquarium at home, so as to have time to really examine things.
I just discovered your blog, Think big ... I've added it to my Reader. I hope you continue with it; you have some good stuff there!