Arenicola brasiliensis (lug worm) hatching!

Arenicola brasiliensis is a large annelid worm that lives sub-tidally in a j-shaped sand burrow. It deposits its eggs in a big mucous mass anchored in the sand. We collected one of these egg masses weeks ago, and baby worms have begun hatching out!

A picture of the egg mass, courtesy of one of our favorite websites: Sea Net, run by James Watanabe.

The juvenile worms move by two types of motion: they beat their cilia, and move with muscles as well. In this video you can see the cilia beating, with especially long ones near the head and butt.

In this video you can see the two red eye spots at the anterior of the juvenile, the segmentation of the body, and the juvenile's muscle's flexing to move the animals "chaeta"(pronounced see-tee, the sharp and clubbed bristles protruding from the segments).