Story of a black jelly

Last summer we had a rare event. Tens of black sea nettles (Chrysaora achlyos) washed ashore on our beach. These guys are pretty rare, so we jumped at the chance to get some gonadal tissue to start a new culture of jellies. We collected the adults from the beach, and I extracted the gonadal tissue from the insides of the bell. (This was a rather painful process which involved me getting stung for three days.)

I used bits of the tissue to sex the animals; females had eggs, and males had packets of sperm. After I figured out who was what, I put a little bit of male gonads and female gonads together in a petri dish and mixed them up, to beak open the male's sperm packets. (It felt a bit like making red scrambled eggs.)

Male sperm packets

Female tissue with eggs

After 3 days, planulae were spotted swimming in the petri dishes.


After 5 days, the planulae settled to the bottom to become polyps. These are newly settled with only 2 fully formed tentacles.


Four months later, I am very happy to say that my polyps have begun to strobilate. I have some beautiful ephyrea, that will become (in my opinion) the prettiest-colored jellies ever.

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.

Life Photo Meme: Hostile

Kingdom: Animalia

Phylum: Cnidaria

Class: Anthazoa

Order: Actiniaria

Family: Actiniidae

This is a starburst anemone (Anthopleura sola), which is common in intertidal areas along the west coast. Anemones, like jellies, have stinging cells which they use to capture food and defend themselves. If you've ever touched an anemone, you've felt the sting as a sticky sensation.

In addition to the normal tentacles used to capture food, some anemones have a second set of tentacles which they inflate in the presence of other anemones. These tentacles, called acrorhagi, have larger stinging cells... larger than those found in the feeding tentacles. They will use the acrorhagi to fight with the anemones encroaching on their area.

This is complicated be the fact that some anemones with acrorhage asexually reproduce by splitting down the center. The two new anemones will not fight with each other, but will fight with any anemone that is genetically different. The anemone pictured above is solitary, and will not have any cloned neighbors, as clones from this anemone generally move away quick.

If an anemone gets beat very badly and needs a hasty retreat, they can inflate the bottom part of their body with air, and float away.

Life Photo Meme: Glassy

Kingdom: Animalia

Phylum: Cnidaria

Class: Hydrozoa

Order: Leptothecatae

Family: Aequoreidae

How can you not think of jellies, when given the word glassy? This a crystal jelly (Aequorea sp.), one of the clearest jellies I can think of. I think this jelly is pretty neat because it is the jelly that GFP (green fluorescent protein) was isolated from.

I also really dig the way these guys eat. The batch of tentacles in the center surrounds the mouth. Unlike other jellies, the mouth can open really, really wide so that it can swallow and eat other jellies that are up to half its size. I've never seen another jelly that could open its mouth this wide, or even open its mouth at all. And they look pretty neat all full of food, too.

Life Photo Meme: Secret

What is the secret behind the demise of this coral? I don't know for sure, but I can make a pretty good guess based on the picture. Can you?

It looks like this coral has been the victim of that famous corallivore, the crown of thorns starfish (Acanthaster sp.). You can see part of the culprit in the center bottom of the picture. What looks like a patch of grey, red-tipped spines is actually the starfish. The crown of thorns is infamous for eating corals. They crawl on top and digest the fleshy parts, leaving the stripped white skeleton of the coral behind. Their spines are also a painful irritant to humans.

The crown of thorns is distributed throughout the indo-pacific, and has been thought to consist of single species, Acanthaster planci. However recent molecular evidence suggests that there are actually four species of Acanthaster [1].

This coral-eating starfish can devastate reefs when they appear in high numbers, but there is hope from a coral eating starfish.

Kingdom: Animalia

Phylum: Echinodermata

Class: Asteroidea

Order: Spinulosida

Family: Acanthasteridae

Photohunter: clouds

This is a picture of a cloud of sperm. You can see the green anemone which produced these clouds wedged in between the upper rocks. Anemones are broad-cast spawners, which means that they release their eggs and sperm in the water column and hope that they get fertilized. They do try to coordinate their spawning efforts by using external cues, such as temperature. When the water gets warm enough, they release their gametes (eggs or sperm). However, for those living in the shallow tidepools, this can get a little tricky, as the temperature of the tidepool's water is often warmer than the ocean water. So, during the reproductive season, you can sometimes find anemones that were fooled into releasing their gametes early.

Two layers or three?

Most creatures in the animal kingdom have three cell layers; endoderm, ectoderm, and mesoderm. Mesoderm is particularly important in increasing complexity, as many of our internal organs are derived from this layer. So when did this layer arise?

To look at this question many researchers have turned to cnidarians (jellyfish & anemones), which only have two layers, to examine the developmental and genetic clues. To make things confusing, some cnidarians posses a third layer, called a entocodon, where some muscle cells reside. Also, all ctenophores (comb jellies) also posses muscle cells. Muscle cells are generally thought to have arisen from mesoderm. So was the ancestor to cnidarians, ctenophores, and bilaterians (everybody else) triploblastic (having three layers), and the cnidarians and ctenophores just lost that layer? Or was the ancestor diploblastic (having two layers) and muscle cells arose separately in all groups?

Looking at some of the genes that are commonly associated with mesoderm, Martendale et al. (2004) found that a majority of these genes are present in his model anemone, and generally tend to be expressed in the endoderm. This means that the tools for creating mesoderm was present in cnidarians, and that most likely, mesoderm arose from endoderm at some later date. However, finding the genes in the endoderm does not completely rule out the possiblity that cnidarians had mesoderm, but that it was lost at a later date.

Burton (2008) reviewed the two possibilities, diploblastic or secondarily diploblastic through mesoderm loss, and makes several excellent points based on numerous papers. First, the third tissue in some cnidarians (entocodon), is not the same genetically or developmentally as mesoderm. The entocodon arises from the ectoderm at a much later developmental time (after gastrulation) than mesoderm. Plus, genes associated with mesoderm are not always expressed in the entocodon, they are more likely to be expressed in the endoderm. So the entocodon is most likely a new cell layer and not a modified mesoderm layer.

Muscle cells found in ctenophores and cnidarians are not the same as those found in bilaterians or even to each other, however the genes are similar. Therefore, it is likely that the genes for muscles were found in the ancestors to ctenophores, cnidarians, and bilaterians and each group slightly modified those genes to get their present shape. In triploblasts, these genes along with others became associated with the mesoderm cell layer, when those cells migrated from the endoderm. Interestingly, in cnidarians the genes associated with mesoderm in bilaterians appear to be used in body patterning. So essentially, cnidarians have two sets of body patterning genes, one of was free to develop into mesoderm and subsequently, internal organs. Even cooler, (I think) ctenophore lack one set of body patterning genes, the Hox genes. Did they lose it? Or did they never have it and we are more closely allied with cnidarians? Do sponges and placazoans have Hox genes? I guess it's time for more reading!

Burton, P.M. 2008. Insights from diploblasts; the evolution of mesoderm and muscle. Journal of Experimental Zoology Part B-Molecular and Developmental Evolution. 310B:5-14

Martindale, M.Q., K. Pang, and J.K. Finnerty. 2004. Investigating the origins of triploblasty: 'mesodermal' gene expression in a diploblastic animal, the sea anemone Nematostella vectensis (phylum, Cnidaria; class, Anthozoa). Development. 131:2463-2474

Photohunter: water

This was a hard choice, since most of the photos I have have to deal with water in some way or another. I chose this photograph of the Great Barrier Reef because I thought it was beautiful and amazingly intricate. You can see so many different types of corals, as well as fish and even some clams. There are over 1200 species of hard corals known and the differences in morphology often translates to different growth rates. Branching corals tend to grow the fastest at 2 to 4 cm a year (but tend to break really easily), while dense, globular corals (brain corals) grow the slowest at 0.06 to 1.2 cm a year. Of course the growth rate depends on nutrient availability, temperature, light, and pH of the water (low pHs can dissolve coral skeletons).

Most people have heard of coral bleaching, the process where corals reject their algal symbiont and turn white. What few people know is that generally this is a natural process. If the water gets so hot that the algae living inside of the coral cannot function, the coral will reject that species of algae and try to obtain a species which does work in the warmer temperature. The issue comes in when the coral cannot get a higher temperature resistant algae or the water temperature rises well beyond what any coral-helping algae can handle. Then the corals die.

Life photo meme: Ancient

Kingdom: Animalia

Phylum: Cnidaria

Class: Scyphozoa

This is a fossil impression of a jellyfish. Considered to be one of the first fossilized evidence of multicellular organisms and still going strong today. Just last year they discovered a jellyfish fossil that was 500 mya old, pushing back the origins of jellyfish by over 200 mya (link here). The impressions were incredibly similar to jellies found today, implying that the origins of jellies may be earlier.

In my opinion, cnidarians are interesting in their simplicity. They only posses two tissue layers, lacking the mesoderm layer which provides the cellular base for many internal organs that other organisms posses. There is some interesting research going on involving cnidarians trying to determine how mesoderm could have arisen from endoderm or ectoderm (I'm in the middle of reading a paper on it now, and promise to write it up later).

How does it do that? Jelly stings

This is a picture of a hydra tentacle. The cool thing is, if you look closely you can see a discharged nematocyst. This special cell is made by all members of the cnidarians (jellies, anemones, and hydras). It has a coiled up thread inside, that when triggered releases and stings the prey. When the trigger is ‘touched’ the bulb of the nematocyst is filled with calcium. This causes an osmotic reaction. In other words, the water from outside the bulb forces its way in to try and dilute the calcium. This causes the barb and ‘whip’ to evert. The firing of the nematocyst takes only a few microseconds.

After the nematocyst has fired, that cell is useless and falls off. New nematocysts are constantly being produced. This process is taken advantage of by some nudibranchs, who eat cnidarian tentacles. The mature nematocysts fire, but the immature ones are incorporated onto the back of the nudibranch where they finish maturing. These pilfered nematocysts can then be used to sting fishes trying to eat the nudibranch.

Tube Anemones

There are several types of nematocysts, depending on their function. There is a harpoon-like one used to inject venom, a sticky one for capture, a lasso-like one for capture and injection, and one that is only found in tube anemones which makes up the parchment structure of their tubes.