Dendraster metamorphosis!

Dendraster excentricus (otherwise known as a sand dollar) is a flattened, burrowing echinoid. Like traditional sea urchins, its rounded body is covered in spines. D. excentricus uses its spines to move sand grains over its body to bury itself into the substrate.

The Dendraster in the lab were fertilized on the fourth of April. By the 25^th of April, we started to see the rudiment forming in the late pluteus larvae. The rudiment appeared on the left side of the larvae, taking up more than half of the space within the body. 

The fenestrated spines and early tube feet of the juvenile sand dollar are visible even within the larva. The juvenile will emerge from its larval skeleton oral-side first so that it can orient itself correctly on the substrate.

Here is a metamorphosed juvenile Dendraster. It is extremely active as it moves along on its tube feet.

         -Jacqueline and Monica

Patiria miniata metamorphosis

Species: Patiria miniata

Phylum: Echinodermata

Class: Asteroidea

Order: Valvatida

Today, we noticed that our Patiria have begun to metamorphose. Below you can see a brachiolaria (advanced Asteroid larva) crawling along the filmy substrate in preparation for metamorphosis, as well as several juveniles that have already metamorphosed.

Up close shots of the brachiolaria:

Juvenile up close:

- Andrew Miller

Lined Shore Crab eggs!

Hey team, 

Here is a short clip of the Lined Shore Crab eggs that Andrew helped me to take off the brooding female.  There is a little bit of movement in the middle of the video, don't miss it!  Otherwise, I know nothing about what is going on and will more research on this species' (Pachygrapsus crassipes) embryology.  

-Chris

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).

Echinoderms: Late Larvae Diagrams

Pisaster giganteus bipinnaria (4/25/2013)

Parastichopus parvimensis auricularia (5/25/13)

Patiria miniata brachiolaria (4/25/2013)

Dendraster excentricus late pluteus (4/26/2013)

Strongylocentrotus purpuratus late pluteus (4/27/2013)

Hermissenda crassicornis, round 2

Species: Hermissenda crassicornis

Phylum: Mollusca

Class: Gastropoda

Order: Opisthobranchia

Just a quick update on our little Hermissenda friends:

We are now 7 days into the veliger stage, and unfortunately a good chunk of our population has died  (likely due to overcrowding). The good news is that those that are left are going strong, and should begin to metamorphose in 27-51 days. When I have the opportunity to go collecting, I will introduce some thecate hydroids to their bowl in an attempt to induce earlier metamorphosis.

In the mean time, here are some of our remaining veligers having fun. See if you can find the eye spots behind the velum (the ciliated, figure-eight-shaped foot protruding from the shell):

- Andrew Miller

Miscellaneous pictures from class!

Yesterday we spawned compound ascidians by incubating them in the dark for approximately 12 hours and then exposing them to sunlight:

And now we're in class, making observations and taking names! 

Taking pictures of sand dollar larvae

And the sand dollars those larvae came from! 

The ribbon egg case of a nudibranch: Peltodoris nobilis

Everyone checking out their larvae.