Anatomy of an electric ray

I love my job. Sometimes I just get to participate in (or watch) cool stuff. As was the case a week ago, when I learned that we were going to be dissecting an electric ray.

This electric ray had been brought in by a fisherman, who didn't want to eat it or let it go to waste. So we decided to hold a public dissection, so that we could learn more about it. We also preserved some of the pieces for our collection, to be used for later research or teaching.


Electric rays are slow-moving rays that live off of the pacific cost, in cool waters. They don't have a stinger, but do have a specialized organ that produces electricity, which they use to capture food and defend themselves.

In this picture you can see the two-chambered heart, center, at the right most edge of the cut. Below that (center) is the stomach. To either side of the stomach are two very large livers. Like all sharks and rays, the electric ray lacks a swim bladder and depends on the oil reserves in the liver to help maintain buoyancy. The large green ball near the upper liver lobe is the gall bladder.


This is a nice close-up of the electric producing organ. Basically, it is little more than coin shaped muscle stacks. Since muscles produce electricity, the arrangement of muscle tissue in this configuration helps optimize the amount of electricity produced in the area. By having an organ on either side of the body, the electric ray can stun prey trapped between the two sides of their fins.

Slime star

This is Pteraster tesselatus, commonly known as a slime star. As its name implies, when disturbed this star can produce copious amounts of slime, which may protect it from predators [1]. It eats sponges and the like and lives in the colder waters off the west coast of the US.

It also has an interesting feature common to many members of its family. It has a 'brood pouch'. The surface that you see is actually a soft covering which covers the true surface of the sea star. In other members of the family, females will release their eggs from their gonopores (like all other sea stars), but retain them under that covering until they develop into juvenile sea stars and crawl out. In this particular species, they do not brood their young, and instead send them shooting out of the osculum, an opening in the covering. The osculum is generally used for exchanging water from the water vascular system to the outside, and can be seen opening and closing even in individuals who are not spawning.

My little squids

Well, the class is wrapping up, which is why I have not been able to post much. We did two projects which required a lot of sleepless nights. Luckily, I was able to finish my paper last night and actually went to bed before 1 am. I did a little study to see if I could reduce the number of embryos in squid egg capsules to see if it affected development. I was quite pleased with it, because they actually survived (not a sure thing when you are breaking open egg capsules).


So here is a pic from one of my squids...



If you look closely at the top of its mantel disk, you can see its two little bumps that will become the fins. The arms /tentacles are forming, and the eyes are becoming more defined and developed. And my favorite part... on its arms are little suckers!



They've still got a bit to go, but since tomorrow is the last day, I've returned the rest of the mass back where it was collected.

I have eyes!

Or at least eye primordia. This is a picture of one of the squid embryos I am working with for my second project. If you look closely at the lumps on either side of the embryo you'll see clear ovals, that's were the eyes will develop. I am very excited to see how they will look tomorrow!

It's been a bit busy, as the paper for my first project was due at the start of the week, at the same time as the proposal for my second (and a presentation on the first during the middle of the week). Hopefully, I'll get a good head start on the second paper tonight... so I can take the time to go whale watching this weekend. I can't believe the program is ending so soon.

Microplankton and Megaplankton!

Another member of the plankton. This is a larval ctenophore. You can make out its ctene rows along the side of the body and the massive mouth right in the center. When I see them, they normally have a copepod stuffed inside.

On the macro side, we found this large fried egg jelly (Phacellophora camtschatica) floating around our dock the other day. The bell can get up to 2 ft (60 cm) in diameter and the tentacles 20 ft (6 m) long. They eat other jellyfish.

Coolest thing ever?! I think so!

So we're encouraged to have pets in class, and I chose to take care of some Owenia sp. because I thought their development was cool. Today I was changing their water and giving the more food, when I thought I'd check them out under the scope. Some of them were really close to settlement, and even started settling on the slide. Luckily, there are tons of video cameras around and I was able to capture the process.

Here it is, Owenia settlement, speed up, in all its glory.

We were lucky to capture about two young giant pacific octopus larvae in one of our night light adventures. Although it looks more like a squid, it is an octopus. As it gets older the mantel becomes rounded and they spend more time on the bottom.



Just to give you some scale, this little guy is about the length of my pinky fingernail. He will live for 3 to 5 years and get to be about 14 ft from arm to arm.

More cute worms!

In addition to Owenia there were lots of other larvae in our plankton tows. These are just two of my favorites, although everything looks cute when it's a baby! The top is some sort of polychaete, and the bottom is not technically a worm although it is worm-like.


It is a phoronid, and is most closely related to bryozoans and brachiopods. Their bodies are shaped like worms, although they have a great feathery lophophore which they use to filter water for food, and their anus loops out near their mouth. They also live in tubes, and they can brood their young in it. There are only 20 species of phoronids world wide.

Revenge of the epitokes

Another night light at FHL. This time we got the large epitokes, about as long as my forearm. You can see a shrimp trying to break the worm open to get the gametes inside later in the movie.

Night lighting

One of the way we get larvae is by lowering a light into the water at night. Many animals are photopositive, that is attracted to the light, which helps them maintain their position in the water column and find food.

By lowering the light at night, we create a sharp gradient of light and can attract a lot of animals. Most of them in this video are megalopae (baby crabs) and epitokes. The epitokes are fast, pinkish, and wiggle as they swim, while the megalopae are much bigger and chunkier.

Friday Harbor

So, I have just gone up to Friday Harbor Laboratories and have been enjoying my immersion in science after quite a long spell without. I am learning all about larval biology, so have been going on field trips to many different sites, like this mudflat pictured above, to look at egg masses and collect larvae.

One of my favorites is this Owenia sp., which is a type of worm that builds tubes out of small sandy particles. This creature has an interesting development, as the juvenile worm develops around the intestine of the larval body. When it is ready to settle, it drops out of the sac where it was developing and eats its old larval body.

Life Photo Meme: Honor an Invert

Phylum: Ctenophora

This is a nice picture of a ctenophore from Monterey Bay Aquarium. Ctenophores are often confused with jellies, as they look similar, and have only two cell layers + the mesoglea. However, ctenophores lack the special stinging cells which characterizes all members of the cnidarians (jellies, anemones, and the like). They do have special sticky cells called colloblasts, which they use for feeding. They are active predators, and can use either sticky tentacles or muscular lobes to capture their prey. the above ctenophore is a lobed variety, and catches its prey by closing those large lobes around it. You can see some of the copepods that it had for lunch in its gut.

The other way comb jellies are different from your average jelly is: the way in which this animal moves. The creature cast produced an excellent movie describing this unique (for a multi-cellular organism) mode of locomotion. If you watch, you should also be able to explain why the comb jelly in my picture has beautiful rainbow stripes...

CreatureCast - Comb Jelly Movement from Casey Dunn on Vimeo.

After the storm...

Because of the storms and high winds which have recently rocked our coast, we've had a number of things wash up on the beach. The most spectacular of which was this...


A Risso's dolphin. We don't know why this guy died, but we do know that he is very young. Risso's get to be 10-12 ft in length, and are born at about 4-5 ft. He may have been just too inexperienced to ride out the storm. We won't know the cause of death for sure until someone does a necropsy. Very little is known about this species, so this little guy will help advance our knowledge.

Life Photo Meme: Ancient

I have lots of photos of ancient organisms, but I had to go with this picture of fossilized hadrosaur skin. First off, considering how fossils are formed, I am always impressed by seeing fossils such as these, and I am sure other feel the same way. Secondly, they offer a glimpse of what these animals may have looked like alive. Now, scientist are able to use some of these amazing fossils, notably fossilized feathers and protofeathers, and an old technique to get an even better view of what these animals looked like.

Zhang and others have reported that they are able to tell what color the dinosaurs feathers were by taking a look into the preserved parts of the cell using a scanning electron microscope. Protein pigments present in modern-day feathers and fur have unique shapes based on color, and are fairly resistant to breaking down. When these scientists looked at ancient dino (and bird) feathers, they found the same pigment shapes. Now they can tell by looking for the pigment shapes what color the feather was. What's more, by looking at the distribution of those shapes they can see if it had stripes, spots, or mottling.

I am looking forward to the new and improved museum models showing the actual colors of these amazing dinos and birds!