The medusae's tentacles are beginning to lengthen. Right now they only seem to have one pair on opposite "corners," but eventually they will have up to 150 on the fully grown animal. The tentacles can be contracted closely towards the body.
A. victoria moves with strong muscular contractions of the bell. Here you can see one moving its manubrium around. The manubrium of a jellyfish bears the mouth at its tip.
Several different species of adult Colonial Ascidians.
Below are tadpoles fertilized around 15:00 4/23/13. Spawned from adults above. Spawning Colonial Ascidians release sperm and ova. Pictures below taken around 18:30 same day. They attach to a substrate and metamorphose rapidly. In the first picture the notochord is clearly visible.
Below are pictures of Nematostella vectensis (starlet sea anemone) eggs and planula. The life cycle of N. vectensis is egg-->gastrula-->planula-->primary polyp-->adult polyp. They are in the same phylum as jellies and the same class as corals. All these creatures have a polyp phase but, like corals, anemones don't have a medusa phase which is that classic jelly fish image.
These egg pictures show the fertilized eggs encased in jelly. The sperm penetrates the jelly and it remains until the planula larvae break out of it about 36-48 hours after fertilization (Uhlinger, 1997). The cell masses surrounding the eggs are 'nematosomes' which are made up of nematocytes and flagellated cells (Uhlinger, 1997). These eggs were fertilized 4/18/13 at 13:30 and the photos were taken a few hours later.
Below is a video of a planula that was fertilized on 4/16/13 at 15:00 and was taken on 4/23/13. This looks like a 'late' planula, the Oral-Aboral (OA) axis is elongated. The aboral pole is the end where we see the long apical tuft (lines coming off the planula to the left in the video). The opposite end is the oral pole. The aboral pole is where the apical tuft is and is where the anemone polyp will attach to a substrate and the oral pole is where the tentacles will form around the mouth. Also note the cilia pulsating all around the planula.
1. Uhlinger, Kevin R.(1997). Sexual Reproduction and Early Development in the Estuarine Sea Anemone, Nematostella vectensis Stephenson, 1935. UC San Diego: California Sea Grant College Program. Retrieved from: http://www.escholarship.org/uc/item/6cq8h6f3
Today we are going to be looking at ascidian development. These animals belong to our own phylum and are representatives of the group of invertebrates most closely related to us.
This embryos is surrounded by follicle cells which are involved in fertilization, block to polyspermy, and in some species, secrete sperm attractants.
Saturday, April 20, 2013
Take a look in the sea water table at the adult Pleurobrachia, the look at this video of the Cydippid larva. There's a small jar of these larvae with about 7-10 of them next to the adults. They are pretty tiny, but you can see them under the scope by their tentacles being cast.
CL
Last week, we collected a pair of Hermissenda crassicornis on the San Carlos Beach breakwater. Even though individuals of this species are simultaneous hermaphrodites (each individual contains both male and female gametes at any given time), current evidence suggests that they reproduce exclusively via allogamy (the sperm from one individual must fertilize an ovum from another individual; self-fertilization is either not possible or not common). This meant that we had to encourage our specimens to mate before we could observe any embryonic development:
Several days after excretion, developing veligers (free-swimming nudibranch larvae) became active within their rapidly-dissolving egg capsules. The tubes around the capsules kept the fertilized eggs in a spaghetti-like mass until they were ready to hatch.
Several egg capsules broke free during collection, and provided an excellent view of developing veligers. Close inspection reveals the embryonic shell (looks like a snail shell) that will disappear later in the organism's development.
Hatched veligers are fast swimmers, but the putting them in the correct dish corrals them long enough to make basic observations about their body plan. Shortly before the following videos were taken, we fed these larvae red microalgae. As a result, their gut compartments have a distinctive pink glow:
We now have some Aeqorea victoria (Crystal jellies) from the Monterey Bay Aquarium. These hydromedusae are found off the North American west coast of the Pacific ocean, from the Bering Sea to southern California. Crystal jellies are bioluminescent and emit blue-green light from their outer bells. One of the proteins they use to produce this light, a green fluorescent protein (GFP), is often used in experiments as a biological marker. The scientists who isolated GFP from A. victoria won a Nobel Prize in 2008.
Little medusae swimming around. The manubrium (stalk-like structure dangling from the center of the jelly) can move back and forth. We are feeding them brine shrimp and rotifers right now.
