My time with a heteropod

We got a new addition last week, a Carinaria japonica an unusual animal commonly called a sea elephant, after its long snout-like proboscis. It is generally around 13 cm (5 in) but can get to 50 cm (20 in) long. This one is about 30 cm (12 in). This animal is a type of snail, called a heteropod, that is modified to spend its entire life swimming in the water column.


Its shell is very reduced, to decrease the weight on the animal, and located on the bottom of the creature. Because of the shell's weight, small that it is, the animal spends its life swimming 'upside down'. The flap that it uses to swim with is a modified foot, and it has a large radula at the end of its proboscis for capturing prey.

It has very well developed eyes for a snail, complete with spherical lenses and ciliated retinas. The retinas themselves are interesting, because they are a thin strip, rather that a large patch. Because of that its vision field is only a few degrees high, and 80 to 180 degrees long [1]. Some species solve that problem by constantly sweeping their eyes up and down.

They eat other things in the plankton, preferring things like arrow worms, salps, copepods, and krill [2]. The prey is ingested whole, and digestion generally takes place without any mastication. There really is not much known on how they capture their prey, and I'd like to make a few comments based on observations made while feeding this little guy.

I have been feeding him by hand, which is certainly not natural, but I have noticed that when I drop food or put food near him, he cannot capture it without some sort of pressure behind it. The jaws of the radula seem to push out, then open, clamp the food then drag it back in. If there is no pressure behind the food, the radula just pushes it away. He generally solves the pressure problem by maneuvering his proboscis so that the food is trapped between it and the wall of the tank.

Obviously, that trick would not work in the wild, but I have noticed a second trick which would work in the wild. With floating food, he sometimes curls in to a circle and traps it between his proboscis and his large broad tail. This may be a behavior which helps them capture food in the wild... we won't know for certain until someone seriously takes a look at that.

In the meantime, I will continue to observe and marvel at my new companion...

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.

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.

Life Photo Meme: Quiet

Kingdom: Animalia

Phylum: Chordata

Class: Actinopterygii

Order: Atheriniformes

Family: Atherinopsidae

These are grunion (Leuresthes tenuis). Found off the coast of California, these fish breed from March to July. Approximately three days after the full and new moons, these fish throw themselves on the sandy beaches of southern CA to lay their eggs. Any noise causes them to quickly flop back into the ocean.

Females bury themselves upright in the sand, while males lay on top of the sand next to the females. After the eggs are laid in the sand and fertilized, both sexes return to the ocean. The female can lay up to 3,000 eggs on a single night, and will return to the beach each time the tide is right.

Eggs take about 9 days to develop, but won't hatch until the waves from the high tides break them open, about 12 to 14 days later. Here is a picture of the developing eggs at about 6 days of age. You can already see the well-developed eyes.



If you were to look at these eggs under a microscope you can also see small red blood cells flowing through the blood vessels covering the yolk. You can also see the heart beating ( in this video, it looks like the heart is above the eyes). The tail and its associated muscles are also well developed and serve to move the small fish around in its egg.

Life Photo Meme: Honor an invert... the coolest invert!

Kingdom: Animalia

Phylum: Mollusca

Class: Cephalopoda

Order: Octopoda

Family: Opisthoteuthidae

This lovely fellow is the flapjack octopus or Opisthoteuthis californiana. Normally deep water creatures, this guy was caught ~1,000 ft (~333 m) from the surface off the coast of California. He possesses very large eyes, which help him find food using the barest glimmer of light that reaches those depths. There really is not much known about their diet, lifestyle, or even distribution (although they've caught them off of California and Japan).

They think that these guys are benthic, but they do have two very distinct swimming modes. The first is pretty common to all octopuses and squids; jet propulsion. They can squirt out a stream of water from their mantle which pushes them head first through the water. The second swimming mode is less common among octopuses. They can use the flaps attached to their heads as fins to swim.

Enjoy this video our flapjack friend swimming about...

Life photo meme: Mystery Sacoglossan

Kingdom: Animalia

Phylum: Mollusca

Class: Gastropoda

Order: Sacoglossa

Family: Hermaeidae

I recently went on a collecting trip up the coast, and there were hundreds of these sea slugs wandering around on the mud flats we were at. They are really small (my hand is the background in the picture), and the trip leader could not identify them. I took a quick picture and they took a egg mass back with them, to try and ID these slugs. I asked a friend who works with sea slugs and she tentatively identified them as an Aplysiopsis species. Interestingly, she had gone on a trip farther north, and seen hundreds of these as well. So they seemed to be blooming all along the central/northern part of the coast.

Alas, we won't truly know what species it is unless we look at its radula and penis, two of the main features used to distinguish different sea slugs. But this little adventure has allowed me to get some fun footage of mystery slug veliger larvae! This larval type is characteristic of gastropods, and if you look at them you will notice that as larvae, they all have shells. The shell is lost in the adult sea slug.

Without further ado...

Some-what weekly video...

Here's what I've been doing for the past two weeks or so... Frantically hunting the docks for my bryozoans and videotaping the larvae.

I am basically trying to see if there is a relationship between larval size and juvenile size. So, after videotaping my little larvae, I settle them and take a look at the juvenile feeding structure. The idea is that these larvae don't feed until after they are juveniles, so the size they are reflects how much energy they have. Any differences between larval size (and thus energy content) should translate into differences in juvenile size.

These larvae swim using cilia, which is either in several rows around the larvae (1st larva) or in a large band around the center of the larvae (2nd larva). They both have a ciliated groove which not only helps propel them, but they also use to 'smell' the surface (so they can find a good spot to settle on).

Enjoy!

Weekly Video: Science Music Video

I finally got around to updating my 'That's What Slugs are For' music video. This video was inspired by and makes use of Greg Crowther's song. For more of his fantastic songs click here!

Without further ado, here is 'That's What Slugs are For', now with more slugs!

Weekly Video: Fertilization envelope formation

Furious bouts of writing followed by furious bouts of procrastination (or is it preceded by?). My newest draft of thesis intro is done (I think this is version seven...), and now I am on to rewriting the methods section...tomorrow. Here is a video of a fertilization envelope forming around a sand dollar egg. Next semester, I might re-film it at a higher magnification.

Weekly Video: Cuttlefish

Weekly video: Blue Pearl Bay, Australia

They say watching fish is relaxing, and boy, could I use that right now... So, a video taken from Blue Pearl Bay, also referred to as the 'fish tank'.



I want to do a post on some of the cool talks I heard at the meeting I went to last week, and I will soon. I just need to finish the results section of my thesis and get back on track with grading. That is so enjoyable. After all, "the results showed that higher temperatures did not decrease the population growth, instead slowed it down from growing".

However, in all fairness, my writing probably distresses my advisor to a similar degree!

Weekly video: Humpback whales

Always a favorite, some humpback whale playing around our boat on the way to a coral island.

Weekly Video: 1st Division

It's my favorite lab to teach, development! Here is a video of the first division of a fertilized sand dollar embryo. It's a little choppy, I was trying to figure out how to speed it up in the new iMovie program and was only partially successful.

Weekly Video: Bryozoan Lophophore

To get me in the mood for my upcoming talks, a video of one of my study organisms filtering water.



I look at the cilia beating, and long to be that industrious (or mindless!).

Weekly Video: Whelks

For your enjoyment, whelks feeding on fish!