Wednesday, September 12, 2007

It's Confirmed!

Mike Tripp and I headed out to Lau Lau Tuesday afternoon to see if we could find anything else out about the Philinopsis gardineri nudibranchs and the cocoons that seem to be connected to them. In my previous post I talked about watching 3 of them mating, then I watched as each of them wandered a few inches away and proceeded to bury themselves in the sand. Yesterday was 2 days after I witnessed the mating ritual, and sure enough right there in the exact spot that each of them buried themselves, there was now a cocoon floating in the water attached to the sand. So I considered that positive proof that these cocoons were indeed related to the mating of this particular nudibranch. Then with a little investigation on The Sea Slug Forum, I found pictures of another nudibranch spawning. It's not the exact same nudibranch, but in the same general family.

From reading that particular post on Sea Slug Forum I learned that these cocoons are actually egg masses. The nudibranch wraps the egg string around its body, then coats it with mucus, and pushes it off of the head end of its body leaving the cocoon shaped structure. The little string holding the egg capsules together is called the chalaza and is a characteristic feature of opisthobranch egg masses. The number of eggs in each capsule varies from species to species, some only have one egg per capsule, while others, such as some species of Aplysia can have 40 or 50. So the next time you're swimming over the sand flats at Lau Lau and you see all those little cocoons attached to the sand and swaying in the current, you will know they are actually egg masses laid by the Philinopsis gardineri nudibranch. The more we learn about our oceans and all the inhabitants of it, the more we can try to protect it. This is obviously the mating and spawning season for this particular nudibranch as these cocoons are popping up all over in the sand flats. So if you're swimming over the sand out there, be sure to keep your fins safely above the bottom so as not to disturb these delicate egg masses.