A Treasure Trove of Tunicates

    Richard L. Howey, Wyoming, USA

 

 

In a previous article, I wrote about some of my early experiences with natural history in relation to my family.

This article also has a link to family, a remote one, but nonetheless worth mentioning, since it gives me a chance to take a rhetorical swing at a cousin I never liked much. While still in my early teens, I decided that I needed a reference book that was more focused than the encyclopedia and it was about this time that my cousin Tim, who was living with my maternal grandparents while he attended college, agreed to sell me his used, battered and heavily underlined copy of Hegner's "College Zoology". I thought then and I still think—70 years later—that he should have given it to me, but I'm sure that somehow, in some way, paying the silly twerp for it helped me build character. However, I can't complain too much. Although the book was a general survey and covered all of the phyla of the time, I happened to open it to the section on tunicates which I read with keen interest. I was utterly fascinated by the account even though it wasn't until years later that I was to encounter a preserved tunicate and another five years after that before I experienced a live one.

The encounter with preserved tunicates was an occasion of happy happenstance. At the time, I was an Assistant Professor of Philosophy, and in the basement of the house we were renting, I set up a lab and I had come across a catalog from Gulf Specimen in Florida which, at the time, was providing 5 gallon buckets of “Shrimp Trawl Trash” for $25 plus shipping. Since the shipping would have to be by truck, I decided that with that expense, it would be best to make a significant purchase, and so I order 6 buckets–$150 was a considerable expense for an Assistant Professor at that time. But I had a bit of help and, at this point, it’s necessary to go into a bit of personal history.

When I first started university at the University of Nebraska, I had decided that I wanted to pursue biophysics. Unfortunately after 2 years, the distinguished biophysicist, Herbert Jehle, with whom I was studying, left to go to an position at George Washington University.

When I first entered the Physics Department, the Chairman interviewed me regarding my interests and then introduced me to Dr. Jehle. I was overwhelmed that he would spend time with a mere undergraduate and I can remember wonderful conversations and discussions in his spendid office. As it turned out, he was renting a house not far from my parents’ house. I was working a night shift at the local telephone company garage and when I would get off work at midnight and was walking home, I would occasionally encounter Dr. Jehle at the mailbox at the end of the street almost assuredly sending off a document that had to with his work in the peace movement. He would always stop and we would chat. I was extremely sorry to see him leave the unversity as he was the first real academic friend I ever had and, at the time, I had little idea of the incredible range and importance of his work.

After he left, I shifted my major to mathematics and was already majoring in German and later added a major in Philosophy, to my parents’ chagrin. Mathematics, they could accept; I could probably get a job as a bookkeeper or tax accountant–but Philosophy!, as my mother put it: “How are you going to support yourself? What kind of job can you get with philosophy? Who’s going to be interested in marrying someone who can’t get a job?”

Well, I got a National Defense Act Fellowship for 3 years in Philosophy at the University of Southern California where I received my Ph.D. in Philosophy. However, my passion for biology and especially natural history persisted and when I accepted the position at the University of Wyoming, I was determined that I would find a way to pursue philosophical biology and maintain a personal research lab for my interests in natural history. Fortunately, the Dean of the College of Arts and Sciences at the time, was receptive and supportive, if somewhat puzzled by my strange mixture of interests. By the time I made the purchase of the 6 buckets of specimens, I was talking about, I had a small grant from the College and was able to use it to provide myself with those and later on with some other more specialized collections from Gulf Specimen. I also had access to the College’s Zoology Stockroom where I was able to use my modest grants to purchase items such as dissecting tools, pipettes, stains, etc. My strange academic bifurcation eventually led to my having a joint appointment as an Adjunct Professor in the Department of Zoology and Physiology. Later, on I also received a College Award that allowed me to spend an academic year doing research with a colleague who was a distinguished protozoologist and cell biologist.

So, all these machinations paid off in wondrous, preserved specimens, some of which I still have today and hope to more investigations on. The marvelous thing about the shrimp trawl trash buckets was that one never knew what one might find. There were small fish, jellyfish, occasionally a wee octopus, crabs, sea urchins, starfish, brittle stars, polychaete worms, flatworms, a few shrimp including some “hammer claw” or mantid shrimp, small skates and sting rays, and even a half dozen small hammerhead sharks, a variety of mollusks, and, of course, tunicates. Gulf Specimen some years later stopped providing preserved specimens completely and devoted its work to providing living specimens for medical and university research. I always thought that if this was a move motivated by ecological concerns, that it was misplaced, since shrimp trawl trash would now just be thrown back into the sea to decay. Perhaps, some of it would provide food for other organisms but, given the scale, I suspect that much of it may have ended up being a contaminant rather than a benefit. However, that may be a consequence of my ignorance about the details. In any case, the first tunicates I encountered in these collections were Styela plicata and I had no idea just how strange and interesting they were. They are certainly never going to win any beauty contests as they look like large eggs covered with warts, scars, and dried garbage. How’s that for sex appeal? One of my friends bestowed on them the description of “chucks of brain” which was also apposite. Here are a couple of images for your delectation.

A reasonably close relative is Styela montereyensis which you might well guess is from the Monterey, California coast. This species tends to attach to the cliff sides and drops down during low tide, looking like strips of brown okra. And here are a couple of images for you to get an idea of what savory treats tunicates can be.

What you don’t think these look like delicacies? Well, I didn’t and don’t either, but I wrote an article in which I stated that I was sure that no one would eat sessile tunicates. Boy, was I wrong. I got emails informing me that tunicates are indeed eaten and regarded as a special treat in some areas. I got messages from Chile, Japan, France, and even the U.S. (Texas, no less–where everything is bigger). If you’re interested in discovering a possible new culinary experience, I’ll provide you the link to my article recanting my claim about the inedibility of tunicates.

Just to give you a brief idea of the consensus of opinion which I received, I’ll give you a short comment by the gentleman from Texas.

“NO! I’m not suggesting that tunicates are a succulent delicacy and I have never read about any culture which uses them as food.

Tunicates are served in seafood restaurants in Chile. It is an acquired taste. They remind me of burnt rubber marinated in tincture of iodine.”

Well, back to the warty “chunk of brain” tunicates. Using bone cutters to sever the tunicate and get a view of the inside, I discovered an extraordinarily weird anatomy. There are 2 siphons (incurrent and excurrent) to bring food in (plankton) and expel waste. Once brought into the Styela, there is a membranous “basket” which secretes a “slime” which moves the food particles down into the stomach. The “basket” is highly fenestrated and rather resembles a version of cheesecloth, but made out of tissue–very odd. Next, connected to the hearts are two pacemakers. The heart beats in one direction for about 150 beats and then reverses as the second pacemaker takes over and the first one recharges. This, of course, means that the vessels must be capable of allowing “blood” to flow in opposite directions. Some species filter out a rare element, Vanadium, from the surrounding sea water and, as a consequence, have green blood! I was curious about the vessels and so examined sections of the warty tunicate, which is composed largely of cellulose compounds–a rarity in animals, common in plants. Another of those bits of weirdness! I was able to get some thin enough sections to indeed confirm that there was a central wall running through the vessels allowing for bidirectional blood flow. Another extraordinary feature is that the larval stages of the sessile forms have a notocord (the beginning of a backbone) which disappears in the adult form. Nonetheless, this explains why they are often scientifically referred to as Urochordates. I also found, to my amazement, tiny spicules embedded in the tunic. Early on, I developed a passion for both calcareous and siliceous spicules and have found then in an extraordinary variety of animals (and some plants as well).

In a colonial tunicate called Didemnum I also found some spicules. These organisms are a white to yellowish to gray encrusting form which can cover surprisingly large areas. To the casual eye, they look rather drab and insignificant. For the spicule seeker, I once again remind you that you can’t simply place sections of this material in a strong alkali and expect the tissue to dissolve due to the cellulose content. Nevertheless, with care, persistence (tinged with a bit of fanaticism, and a skillful use of some good micro-tools, you will be able to discover some quite interesting little spicules. In this case, each tiny white spot is a spicule.

However, I don’t want to mislead you into thinking that all tunicates are ugly; some are extraordinarily beautiful and look like transparent vases or are delicately colored or form small flower-like colonies or look like they are blown-glass. I’ll give you a link on Google to show you of the remarkable variety and we’ll take a closer look at a few types in a minute.

Free-swimming doliolids, appendicularia, and individual salps can be quite small, sometimes measuring less that 1 cm. (I’ll explain these types in a moment.) However, some salps can get up to 10 cm or about 4 inches. However, chains of salps and pyrosomes have been recorded at over 26 feet in length. O.K., let’s start with doliolids (partly, because it’s fun to say). In the water, they are often very difficult to see because they look like they are blown glass. They are, however, tougher than they look. Their appearance is that of a transparent, miniature barrel usually having 8 muscle bands around the inside of the barrel. The doliolid, like other tunicates, has an incurrent and excurrent siphon which, in this case, are located at opposite ends of the barrel. Water and minute plankton for food enter the incurrent siphon, the muscle bands contract, and the excess water is expelled, propelling the doliolid through the water–Mother Nature’s version of jet propulsion! The part in the center that looks like one of the aliens designed by Giger (you remember the film “Aliens”)-- has the mouth, the brain, the testis, the ovary, and the intestine, among other bits and pieces, such as the endostyle, the subdural gland, stigmata, and the branchial sac, all of which you can look up, if you’re interested. Below is an image (slightly improved) from Google which will give you an idea of the general appearance.

I already mentioned that salps can occur as individuals or, more usually as colonies. Individual salps can be less than an inch in length or several inches, as in the example which I’ll show you below. Colonial ones can be up to 26 feet as observed so far. You can see from the individual salp that it looks gelatinous and in water can be virtually invisible to us. It is, however, not as delicate as it looks; in fact, it is quite tough like gristle. The 2 images below are from Google and slightly enhanced. The individual one is one of the larger forms and is known as the “twin-tailed” salp. The colonial one is demonstrating bioluminescence. These are also known as pyrosomes or “fire bodies” and were first observed by a French explorer in the early part of the 19th Century. There is an old tale that a large colonial form was dredged up in a net at night and having been thus disturbed, it exhibited its bioluminescence. Then when the light show ceased, a sailor wrote his name with his finger on the organism which then displayed it luminescently. This is almost assuredly one of those fine old sea tales that bored sailors concocted to entertain the landlubbers when they returned home. So, it must be true. Pyrosomes can create quite dramatic displays. They are also capable of a kind of jet propulsion that slowly moves them through the water as they collect food.

Years ago, I sent out a plea to a number of marine biological laboratories for specimens of salps and said that I was willing to pay shipping and handling. Well, I did get a response from a researcher at the University of Hawaii, who generously sent me a half dozen of the large specimens of individual salps. I still have 4 of them preserved and hope, one of these days, to do some further examination. The 2 that I examined previously presented multiple challenges and I assure you that salps are not softies; they persistently resist revealing their secrets. Nonetheless, they are worth the frustration and effort for they are extraordinarily fascinating creatures.

The last group of tunicates that we’ll look at is perhaps the strangest of all, the Appendicularians or Larvacea.

First, I’ll show you a juvenile form before it has “constructed” its “house”. It makes one think that Giger must have been hanging out with some marine biologists. In an interview, when he was in his late 60s, he said that from childhood, he was fascinated with things like mummies and skulls.

These organisms produce a “house” or covering which consists of proteins and, once again, cellulose compounds. It surrounds the appendicularia (lovely word) and has incurrent and excurrent siphons. Remarkably, these houses are more or less disposable and, in some species, are replaced every 4 hours or so. It then “unfolds” a new house around itself and continues with feeding and propelling itself using “jet propulsion”. When the filters of the siphons clog or the organism feels threatened, it jets itself out of the “house”. Oh, I wish moving to a “new” house had been as easy for us a few years back.

And now a diagram to help you understand the location of the various parts. All three of the Appendicularia images are from Google and enhanced a bit.

The “tail” of these bizarre creatures contains some neurons which are absent in forms such as the sessile Ascidians.

At one time, I’m sure I had the largest collection of tunicates in Wyoming and very possibly in the Rocky Mountain area. These organisms are so strange and mysterious that they are well worth spending a great deal of time studying, but they require patience and ingenuity in order to unlock even a few of their secrets.

I have long since forgiven my cousin for charging me for that textbook that introduced me to tunicates. When my wife and I moved to Los Angeles in the early 1960s to go to graduate school, at the urging of some family members, I contacted my cousin who had taken a job in L.A. He generously invited us to join him and his wife for a picnic at Point Fermin Park at the southern tip of San Pedro near the entrance to Los Angeles Harbor. There are steep trails that lead down to the beach where there are tide pools. We arrived in my lovely, nicely used, black MGA convertible roadster–the second most favorite automobile in my life–and walked down the trail to a picnic table to wait. My cousin and his wife arrived a few minutes later, carrying two large wicker hampers. They wanted to go down to the beach itself where there were also tables and have our picnic there. So, we toted the hampers down and my cousin cautioned: “Careful with that. It’s got crystal in it.” I thought to myself, what sort of idiot would drag heavy rocks down to a picnic in a hamper. As it turned out the crystal was 4 lead crystal glasses and accompanying it was 3 bottles of very nice white wine, thus accounting for the weight. We found a table easily, as no one else was around except a few divers out in the water much further down the beach. The other hamper contained caviar, brie, Camembert, crackers, Melba toast, thinly sliced roast beef, honey roasted ham, grapes, sliced apples, and cherries. The sun was warm, there was a light breeze meaning that the air was clear of smog, the food and wine were delightful, the conversation, desultory, but congenial enough. However, I couldn’t resist the siren call of the tidepools and I dragged my cousin down with me and as we peered into pool after pool, occasionally dashing back a foot or two to avoid the splash of a wave, I held forth about all of the animals we glimpsed. I told him that it was in part due to his book that I was familiar with all of these wonderful creatures. His eyes glazed over with boredom; I think he now had a position selling insurance or some other such dull, but remunerative, occupation.

My wife and I returned home, gliding in my lovely MGA around the other cars, pickup trucks, and semis to our little house which we were renting. Yes, a little house with, unfortunately, no room for a lab or even a single space to set up a microscope. My tunicate studies had to wait for another 7 years and 1,000 miles away from Point Fermin.