Every spring the barn swallows return to the marine lab, not exactly on the first day of spring as in San Juan Capistrano, but I always know it's really spring when they arrive. They build their mud nests against the eaves of the buildings, and spend time chattering at us from the fences.
However, the swallows don't always choose the best location for their nests. About two weeks ago a pair of swallows were determined to build their nest here:
The poor birds would build up a small pile of mud, only to get all twitterpated and bent out of shape whenever anybody walked out the door, which is every few minutes. I'm not sure if the proto-nests fell down by themselves or were hosed off, but it took the birds about a week to take the hint.
Then they decided to build the nest here, which makes a lot more sense:
Doesn't the little guy (or gal) look pretty satisfied up there? This site is farther away from any doors and is on a building that people don't go into or out of nearly as frequently, so the swallows should be able to raise and fledge their young successfully.
The marine gastropods and bivalves go through a larval stage called a veliger. This larva gets its name from the ciliated structure, called a velum, that the animal uses for swimming. Veligers have shells--1 for gastropods and 2 for bivalves--and can withdraw the velum into the shell. Even gastropods that lack shells as adults, such as nudibranchs, have shells as larvae.
The egg mass from Dendronotus is still intact and the embryos are developing nicely. This morning when I looked at it through the microscope I could see the little larvae swimming around inside their egg capsules. I wanted to take a closer look under the compound scope, and when I teased apart the egg mass some of the larvae were forced to "hatch" prematurely. They're not yet ready for life on their own but now they're out in the real world swimming, for better or for worse.
Not being one to let an opportunity like this go to waste, I took some video of the almost-veligers.
You can see the cilia on their little velums whirling around. The larvae aren't as spherical as I had expected, based on what I've seen in other nudibranchs, and I think it'll be fun seeing how they develop. More as things unfold!