Now, this is a classification of the fish that you are goingto need to memorize for the first midterm exam in a week and ahalf. And this is in your Illustrated Notes. So you don't haveto frantically copy it down.
The this is a example of a what's called hierarchical classification.It's a hierarchy. It's a series of progressively smaller groupings,if you will.
And some of this you should be sort of generally familiar with.We are dealing with kingdom Animalia. We are dealing with thephylum Chordata. You'll hear about that in lab. That's the phylumthat includes several different kinds of animals including thesub-phylum Vertebrata, which are the vertebrates, the animalsthat are the subject of this course.
And the sub-phylum vertebrata is divided into 2 what a calledsuper classes. The super class "agnatha" Translationof "agnatha" is without jaws.
When you put that prefix "A" in front of somethinglike amoral, means without morals. Asexual means without sex."Agnatha" means without jaws. Gnathostomata, means jawed-mouth."Stomate" is an opening. And "gnath" meansjaws.
We have 2 groups of vertebrate animals. 2 major sub-divisionsof the of the vertebrate animals.
The ones that don't have jaws are in the super class "agnatha."And the one's with jaws are in the group "gnathostomata "
And then you see a whole bunch of classes of animals, and someof these are extinct and some are still alive.
And some of these animals -- well, I'm going to go throughall of them before the midterm, so that you understand somethingabout the characteristics, and the distribution, and when theyoccurred, some of these are fossil groups are living groups.
But just in terms of understanding this classification, takea look here at these animals in this group, this class. By theway, each of these groups, like the class "chondrichthyes,"the general term for a group like that is a taxon. The class chondrichthyesa taxon. The sub-class elasmobranchii is a taxon, a grouping,it's a scientific name for a group.
Now, the shark are placed into the sub-class elasmobranchii.
And what I want to do is I wanted to give you an example ofthe kind of question, because I think in terms of studying forthe exam it's going to be helpful for to you understand the kindof questions that I'm going to asking you on in the exam.
One of the things I'll be doing in the remaining lecture istelling you a fair amount of information about anatomy, the physiology,the natural history, the modes of reproduction of these groupsof animals. And there's going to be a lot of terminology associatedwith that.
And I'm going to expect you to know that terminology and knowwhat group it describes. So for example, a sample midterm questionmight be:
Blank is the sub-class including, let's say marine vertebrateswith separate external gill slits and a hetero circle tail.
And in lecture I would have told you that -- there is only onespecies of shark that does not live in the ocean. Marine meansliving in the ocean. I would have explained to you separate externalgill slits means. It means they have these little separate openingsalong the side there of their body, behind the eye and in frontthe pectoral fin. And I would have explained to you that a heterocircle tail is a tail which has a bigger and massive dorsal lobeand a more thin like ventral lobe.
And I would have told you probably 4 times as much informationabout sharks. You know, they have spiracles, how they feed, howthey reproduce, they have structures called claspers. I wouldbe asking to you be tell me what would be the answer to this question?What's the answer to the question? The answer is elasmobranchii.
Notice that I do not want you to write sub-class elasmobranchii.Why? Because sub-class is part of the question. You don't needto repeat the question.
So in this case the answer would be elasmobranchii.
The point I want to make is that in an hierarchical classificationlike the one you are looking at here, there are what we call lowerlevels and higher levels in this classification.
The lowest level in the classification is the most indentedone. And that would be sub-class elasmobranchii. There is anotherlevel at the same sub-class levels, some animals that you arenot as familiar with. But those 2 sub-classes together, constitutethe class chondrichthyes. That's why they are indented underneaththe class chondrichthyes.
And the class chondrichthyes along with a number of other classesmake up the superclass gnathostomata, which combined with thesuperclass agnatha make up the sub-phylum vertebrata. And theseare the higher levels in the classification. Anamalia in thiscase is the highest level in the classification. Elasmobranchiiis the lowest level in the classification. And there are a bunchof intermediate levels in the classification.
So exactly the same set of characters -- so the bottom lineis you need to know the lower levels of the classification. Youneed to associate the characteristics with the lowest level inthe classification, but you also need to know the whole classification.You need to know the higher levels of the classification.
What that means is this exact set of characters could be usedto test your knowledge of the higher levels in the classification.All I have to do is change the question to that:
Blank is a class including, not exclusively made up of, butincluding marine vertebrates with separate gill slits. What'sthe answer to that? Chondrichthyes. And what if the question isthis, superclass? Gnathostomata.
And obviously it could be a sub phylum or kingdom or anythingelse that I wanted it to be.
You need to do two things in memorizing this material for thispart of test. This going to be 25 to 30 percent of the test. Everyquarter I have some students who refuse to learn this material.What does that mean? You are condemning yourself to getting --the best possible grade in this class is a C.
You throw away 30 percent of the points, and you are absolutelyguaranteed -- you are not going to get a hundred percent of thebalance. You're headed for D city or maybe repeating the class.So don't kiss off this material.
You have to do two things, you need to associate the characteristicswith lowest levels in the classification. You can do that in ateaching machine. Abbreviate a list of the characteristics onone side and the name of the taxon on the other side.
You have learn all the characteristics. You can't say that turkeyHoyt give me 15 characters of the elasmobranchii. I'm not goingto learn all 15, I'll just choose 7 arbitrarily. What if I choosemy 3 from the other ones. You're out. You have to learn all thecharacteristics of the group.
And that's not as impossible as it sounds, because these areinteresting, living organisms. All right. There is a picture ofone. You are familiar with a lot of these animals. You alreadyknow a little bit about some of these animals.
So you have learn the characteristics.
But other thing is you have to memorize the classification.And that's a matter, you know, you go over to the computer center,and you grab a big pile of thrown away printouts, and you justwrite that sucker out over and over again.
Remember when you had to memorize some poem from Robert Frostin 10th grade. That's what we're talking about here. Memorizeit stanza by stanza. It makes sense, there are groupings. Thesegroupings have characteristics. It's not a phone book.
But memorize and be able to write out that classification. Soyou have to memorize the classification so that you know thehigher levels, and you have to associate the characteristics withthe lower levels.
And when you do that teaching machine, you need to use it inboth the directions. One time you go through and cover up theright-hand side, which is the way I have been explaining and youwrite out the characteristics. But another time you go throughand you read the characteristics, and you write out the name ofthe taxon. Because that's really the way you are going to be testedon that material.
Now, we're looking at the living vertebrates. And we're lookingin the subclass agnatha again. If you look at your classification,we're back up at the top there, and we're looking at the ordercalled petromyzontiformes.
These animals, you have already seen is a larval version ofone of these guys. In lab you looked at the ammocetes larva. Remember,you have these 2 organisms that when you look at them on the slide,they look an awful lot like each other. They both start with "A"so you know you are going to have to concentrate on how you totell the difference.
One of those animals is the ammocetes larva. Larva means thatit doesn't have functional gonads. That's how you tell the differencebetween Amphioxus, which does have gonads, where you can tella male from the female. And ammocetes, which is a larva, thatdoes not have gonads.
It's a larval form of an animal called a "lamprey."And that is the type of animal that is placed in this group thepetromyzontiformes.
I'm going to be continually, throughout the quarter, tellingyou some things about these various taxa. One of them is goingto be the number of species of animals. And I really do not expectyou to memorize the exact number of species, but you ought toremember kind of -- what we would call an order of magnitude withina multiple of ten.
So when we are looking at a taxon that has a single speciesin it, that's really and unusual specie to be placed in its ownorder or suborder or something like that, for a single speciesto be listed at the level the classification that we're talkingabout here is very noteworthy.
Then we have some taxa that have maybe 10 to 20. This is a mediumsize taxa around 100 to maybe 500. And then we have some big taxaaround 1000, and one huge one that's around 30,000.
So remember approximately to an order have of magnitude toa number of specie. And pay particular attention to the taxa thatare the biggest, and the mono (spelling) specific taxon have onlya single species.
There are 30 specie of lampreys. And there are 2 basically differenttypes of lampreys. They all start out as an ammocetes larva, theyare little filter feeders, they pump water through their mouthand they filter out suspended particles.
The other 2 -- some species of lampreys, after, maybe, 7 years,as a little filter feeder, and they get to be pretty big, like20 centimeters in length, and can still make a living as a ammocetesfilter feeder larva. Obviously, we get them little tiny ones toput on microscopes.
Some specie metamorphose. There is an important characteristic.They are not very many vertebrate taxa that undergo metamorphosisbut this is one of them. Metamorphose into ecto-parasite, intoan animal that goes down street out of the freshwater habitatinto the ocean and attacks other fish, hooks on to the side ofthe body of the animal, they have a sucker-like mouth.
And they become these marine lampreys, which are ecto-parasites.They don't have jaws because they are in the agnatha. But theyhave a kind of a file-like tongue. And they suck on the side ofa fish and they kind of grasp a whole and suck the blood andlymph out of the animal's body as an eco-parasite.
And they can get to be pretty big, a meter in length. Thoseare the sea lampreys.
The other lampreys have a much more benign, but short adultlife. After they undergo metamorphose, those are the called thebrook lampreys, and they just live for sex. They live for severalweeks and there only reason, the only thing they do after metamorphoseis to mate.
You have an X-rated picture of lamprey sex on the bottom ofthe page there. And thing that's interesting about the brook lampreysis that they are trying to save their energy for reproduction.They don't want to waste a lot of energy swimming.
They also have a little sucker mouth as a result of that metamorphosis,so they can no longer feed by filter feeding. What they use theirlittle sucker mouth for is to attach to a rock.
Instead of sucking onto another fish and sucking the vital bodilyfluids out of the fish, they suck on a rock as a way of savingenergy so they don't have to continually swim against the current.
And the name petromyzontiformes, "petro" means rock.The translation of "petromyzontiformes" is stone suckerbecause of this behavior of the brook lampreys of sucking ontorocks as a way of keeping from wasting energy on swimming.
Now, we have some terms that we use when we are talking aboutaquatic vertebrates that tell us about the life history of theanimals.
The 2 terms are anadromous and catadromous. Anadromous and catadromous.
And one of these means upstream; and one of these means downstream.
Upstream and down stream.
Anadromous and catadromous. If an animal goes -- it means tobreathe. The larval -- the lamprey goes downstream -- I'm sorry,it goes upstream to breathe.
The marine lamprey, when it gets to be a meter in length, goesup -- he's living in the ocean, he's a marine, he goes upstreaminto freshwater the males and females find each other, you getthe mating that's shown on the bottom the of the page. The eggsare laid in freshwater. The larval lamprey live in freshwater.
And then after they live in freshwater as filter feeders, thenthey go back out to sea to live, but they come upstream to breathe.What is the most famous fish that you know?
STUDENT: Salmon.
INSTRUCTOR: So salmon go upstream to breathe. The babies areborn up there and they go down after. How are you going to rememberthese 2 terms? How are you going to tell the difference?
Are there any words that you know from biology classes or justfrom everyday existence that have either of both of these prefixes.
STUDENT: Catabolism.
INSTRUCTOR: And the opposite is anabolism.
Catabolism is more common. Any other terms that you can thinkof that have the same prefix?
STUDENT: Catalysis, probably.
How about anabolic steroids? Same root is here. Anabolic. Everybodyknow what anabolic steroids are? Who doesn't know what anabolicsteroids are? Who knows and can tell us what they are?
STUDENT: Lowers your metabolism?
STUDENT: They make you build muscle.
INSTRUCTOR: That is what the weight lifters that are willingto risk cancer and detection by the International Olympic Committeeare taking.
That's anabolic steroids, building up muscle. So anabolic steroidsand anabolism means up. Catabolism is the breaking down of food.
So catadromous means to go downstream and anadromous means togo upstream.
So the lampreys are anadromous, they go upstream to breathe.The babies are born in freshwater and the adults go out to sea.
The next group, and the last of the 2 living groups of agnathavertebrates, jawless vertebrates, is order myxiniformes, whichyou probably have not encountered. These animals have really uglynames. They are called slime hags because they have can producecopious amounts of mucous. They are little scavengers.
There are about 15 species of these animals. I think they arein the taxon which is the most unlike all other vertebrates inmany respects. They're really, really weird critters.
The slime hags, myxiniformes, that root "myxi" refersto slime. And that's not a really important part of their biology.If you catch one of these things and you put them in a bucketof sea water, come back in an hour, you have got a bucket of jello,they produce so much slime. But that's not a particularly importantthing about their biology.
You have in your ear region, you have 3 semi-circular canals,little fluid filled tubes that responsibility for the abilityto sense movement and direction. If you go to the amusement parkand get on one of these spinning rides and feel real weird, that's because you messed up your semi circular canal. Most vertebrateshave 3, these guys have only one, the myxiniformes.
They also have a bizarre sex life. They are capable of serialhermaphroditism.
Now, if have had ZOO 137, and you studied some of invertebratephylum, you know that hermaphroditism, means the ability to functionas either a male or a female.
It has this word "Hermes" was a Greek male God, Aphroditewas a Greek female God. So hermaphrodite is an animal that canfunction as either a male or a female.
Many invertebrates are simultaneously functioning, like tapewormsand things like that, can function as both male and female. Theyproduce both eggs and sperm at the same time.
These slime hags are hag fish, as they are also called, theywould rather switch than fight. They can be a male in one breedingseason and a female in the next season. That's what "serial"means. They can go from one to the other, one after the other.
They are scavengers. They feed on the sort of decaying carcassesof fish and other things that they find in the water. They aremarine. Exclusively marine, only in the ocean. And they are usuallyfound near the mouths of big rivers.
Why is it a good idea, if you are a scavenger, to live at themouth of a river. It's like living at the end of a conveyer belt.Sit there and let the river bring you the carcasses. So they arefeeding on these decaying carcasses and everything.
And they have a feature that we see -- and they burrow throughthe flesh of the animals that they are feeding just on like worms.And look they have a feature that we will see over and over againamong burrowing vertebrates. They is they have what we calledvestigial eyes.
Vestigial is a general term. It's not something only appliesto eyes. It just means something which is a vestige, kind of aleftover, a nonfunctional remnant of formally functional organ.That's a vestigial organ.
Our appendix is a vestigial organ. Nipples in male mammals arevestigial structures.
These guys have vestigial eyes and they are covered over witha continuous layer of skin. They have some sensitivity to light,but they don't have lens, they can't form an image. They havedegenerate a eye. They means they have evolved from some ancestorthat had a good vertebrate eye but they have given it up.
Well, obviously, if you are going to make your living borrowingthrough flesh, you might want to have your eyes closed all thetime anyway.
And having that eye sealed over so you can't get pieces of stuffin your eyes is actually probably a useful adaptation.
So these animals have vestigial eyes. A single semi circularcanal, serially hermaphroditic. And they exhibit direct development.Even though are placed in the same class, agnatha, as the lampreys,which undergo metamorphosis, these guys exhibit direct development.They look like a little tiny version of the adult when they areborn.
So the next class that we need to talk about is the class Chondrichthyes.Translation of that class name chondr, ichthyes, who can tellme the translation of that?
STUDENT: Cartilage fish.
INSTRUCTOR: "Ichthyes" means fish. "Chondr"is cartilage. These are the cartilaginous fish. That is they allhave a skeleton composed cartilage and not bone.
There are 2 sub classes of cartilaginous fish. And the firstof these is the Elasmobranchii. That term "Elasmobranchii"is a reference to the structure of their gills. "Branch"refers to breathing and it has to do with the structure of theirgills, it's not a particularly informative term.
The subclass Elasmobranchii includes the sharks as well as theflattened bottom dwelling skates (spelling) and rays. And youhave a picture of one here on the page. This is a skate, and rayslook sort of like that only with a little bit of less tail tothem. There are about 575 species, maybe 600 species, placed inthis subclass. And they have a world-wide distribution, and theylive -- with only a single exception they are all marine animals.
Sharks, there is only a single example of a freshwater shark.
The sharks have this sort of streamlined or what's called a"fusiform" body shape, which is simply an adaptationto reduce the drag as they swim through the water.
They have a hetero circle tail. I have already defined thatfor you. It means the dorsal lobe is larger and it -- the wayit pushes on the water it tends to push the water down a littlebit, which tends to generate a little bit of an upward force thathelps to support the body of the animal. These animals do nothave swim bladders. They are usually somewhat denser than water,so this have a tendency to sink.
And, in fact, the reason that they have a cartilaginous skeletonis that that's a way of decreasing their density. So the cartilaginousskeleton in these animals is not a primitive feature. It's notsort of a left over embryonic structure. It's an adaptation ofa means of reducing density in a group of animals that have notevolved the swim bladder, which is the mechanism for reducingthe density.
They have separate external gills slits. If you look at thepicture of the animal on the page there, you can see it has theselittle vertical openings on the side of the body behind the eyeand in front of the pectoral fin. And those are the openings throughwhich water passes.
The way all fish obtain oxygen is they pull water into theirmouth and it passes over their gills and it exits the body throughthe side. And the primitive condition which we see here in thesharks is to have these separate openings on the side of the animal'sbody through which that water passes. Those are the gill slitsor gill openings.
A different species of sharks can have anywhere from 5 to 7gill slits on the side of their body.
Now, the rays and skates are animals that to some extent atleast have sort of given up the battle on this density issue.They still have cartilaginous skeletons, but they are dorsoventrallyflattened just like the Ostracoderms.
They are bottom dwellers. And they settle to the bottom andsit there and they have these big enlarged pectoral fins, thefins on the front of the body of an animal are called the pectoralfins. Pectoral is a general term that we use for the front legs,your arms are your pectoral appendages. These are the pectoralfins from which the front legs and arms of animals have evolved.The pectoral fins are very enlarged, so when you look at pictureof the skate, this area out here is a specialized pectoral finon the animal.
Of course, we know that most sharks are carnivores. There aresome very large sharks. The largest, in fact, are filter eaters,feeding on the same kinds of crustaceans, shrimp and krill andthings like that that some kinds of whales feed on. Really thelargest sharks are filter eaters. Convergence in a sense withthe whales.
But some of the skates and rays feed on various kinds of invertebrateanimals. They have a flattened -- almost like crushing platesin their mouth. Their teeth have evolved from these crushing platesand they can feed on sea urchins and other things like that. Theycan even crush the shells of shell fish like barnacles and clamsand things like that.
Sharks have the ability to detect electric fields. They cansense an electric field, which is a relatively unusual sensorycapacity among vertebrate animals. They have structures on thenose that are the called the "Ampullae of Lorenzini."
And these are sensitive to electric fields. So they can detectvery, very weak electric fields. They can sense -- there are fishlike flounder, for example, that are bony fish, that bury themselvesin the stand. At the bottom of the ocean, they will bury themselvesa couple of inches beneath the surface of the sand. A shark cansense the electric field produced by the beating of the heartof that animal a couple of inches beneath the surface of the soilusing these Ampullae of Lorenzini. They are pretty amazing animals.
Sharks have internal fertilization, which they achieve by meansof an intromittant organ that I have already mentioned, and thatis a clasper.
And you have a picture here at the bottom of the page of a maleshark, and he has a pair, one pair of claspers. They are sortof finger-like projections that are on the pelvic fins. The pelvicfins are the fins at the back of the animal, and they are analogousto your legs or to the hind legs of a 4-legged animal.
These are the claspers on the shark. And the male presses those2 together and they form just kind of a little groove, and thenhe sticks that paired structure into the female's cloaca and transfersthe sperm over to her cloaca which is the opening of the digestive,renal and reproductive tracts.
After fertilization is achieved, then in different species ofsharks, maybe oviparous, ovoviviparous, or viviparous, that isthere are sharks that are live bearing. They even have -- someof these viviparous sharks have a placenta for means to transfernutrients from the bloodstream of the female to the developingbaby.
And then are some sharks that lay eggs. There is a full rangeof embryonic development is possible in this subclass.
In the other subclass in the class Chondrichthyes is the subclassholocephali. These are sometimes called "ratfish," andtheir fairly rare. There are only 25 species. They're found insort of moderately deep marine waters. There are only found inthe ocean. They are found in waters that are maybe 80 meters deep.
They do come in close to shore to breed so that people occasionallyfind their eggs that are deposited near the shore. But we don'tsee the adults themselves. They do that at night, so that thereare not many observations of the behavior of these holocephaliansor ratfish in nature.
And they are placed in the class Chondrichthyes because theyhave a cartilaginous skeleton like the sharks do, but they areseparated into a separate subclass because they do not have separateexternal gill slits. They have the other -- they have a versionof the other way in which fish handle this.
If you look on the side view of the animal, which you can seeis there is a kind of a line right here. What they have is a coveringover those gill slits. And that covering is called an operculum.
That's a name that you will encounter in many different placesin biology. Any kind of a door or covering will be called an operculum.Snails, for example, have an operculum.
But these animals have -- since their skeleton is composed ofcartilage, they have an operculum that is composed skin and muscle.So they are said to have fleshy operculum.
Here we have a holocephali and they have a fleshy operculum.And that distinguishes them from the subclass Elasmobranchii whohave separate external gill slits.
That's basically the two different ways in which aquatic vertebrates-- either you have external gill slits or you have some kind ofan operculum. Most of the fish are bony fish, and they have abony operculum. These animals have a fleshy operculum.
In terms of their feeding, they feed on shrimp and mollusks.And they also have this development of these sort of crushingplates, where the teeth, instead of forming like the teeth inyour mouth do, you know a series of cutting surfaces around --on the jaw around the periphery, what they end up with is kindof like a cobblestone street affect in the bottom and top of theirmouth.
so they have whole plates that are composed of separate teeth.It would be like a cobblestone street. And name for that is duroghagusdentition. Durophagus dentition is the technical term for thisarrangement of these crushing plates of teeth. "Phagus"means to eat and "duro" means hard or durable or somethinglike that.
Another thing that distinguishes this subclass from the othersubclass is that they have 2 pair of claspers. Remember we lookedat the claspers on that male shark, and we saw a single pair;these guys have 2 pair of claspers, the only group of fish thathave 2 pair of claspers. We don't know what that implies abouttheir sex life, but it is certainly something that can be usedto distinguish them anatomically from the other subclass of cartilaginousfish.
Now, the remainder of the fish that -- well, as I said, in termsof reproduction, I mentioned that they are oviparous. They allhave internal fertilization obviously, that's why they have claspers.But they are oviparous because they produce eggs cases that theylay in close to shore at night.
STUDENT: They are only oviparous?
INSTRUCTOR: Yes, they don't have a whole range of other possibilities.
Now, the rest of the fish are in the last of these classes.And they are in the class Osteichthyes. And what is the translationof Osteichthyes? Bony fish. "Osteo" means bone. Andthese are the Osteichthyes. The term "Osteichthyes"is not on the page that you are looking for, but this is whatthe next page in the notes looks like.
The class Osteichthyes is divided into 2 subclasses on the basisof the appearance of the fins. So we have the class Osteichthyes,and then we have a subclass that we are looking at right here,which are the fish that have fleshy fin, this is the Sarcopterygii.
The other subclasses really contains the majority of the livingis the subclass Actinopterygii, I'll get to them in a second.
Now, both of these terms of the root "terygii" whichis a root that means either a fin or a wing. It means either afin or a wing. Sarcopterygii, what's another term that you encounteredthat has that root "sarco"?
STUDENT: Sarcoplasmic reticulum, sarcolemma, it just means theflesh. A sarcophagus was the thing that the body of an Egyptianking was put in. So these are fleshy finned fish, the subclassSarcopterygii.
There are 2 superorders. The Sarcopterygii, if you look at theside of the body of a Sarcopterygiian fish, what you see is anarrow base to the fin. And there are going to be -- if youcould look inside of that, you could find that there are somebones.
And then peripherally, you have more bones further away. Andthen finally the distal portion the fin is going to be supportedby a series of long, thin, needle-like structures that are calledfin rays.
And this particular group of animals is interesting to us becausethese bones that form the base of the fin, at least in one group,evolved into the bones that form our arms and legs.
The Actinopterygii, if you look at the side of the body of oneof these guys, you see a more broad-based fin. And the fin rays,which are basically the same kind of structures, these long, needle-likestructures, they go all the way down to the base of the fin.
Now, inside the body of this animal, underneath the skin, therewill be some bones that the fin rays attach to. But the base ofthe fin itself is broad and they of this structure of the finrays. Actinopterygii, "actino" does anybody know whatthat means? It has a root in Spanish. It means needle, narrow.
So these animals have fins that are supported by needle-likestructures. It's a reference to fin rays. Obviously, the otherguys, also, have fin rays, but they have this fleshy base withmuscles and bones making up that fleshy structure.
So the animals that we're talking about here are in the subclassSarcopterygii, and we'll get to the Actinopterygiians in a littlebit.
Within the subclass Sarcopterygii there are 2 superorders. Andthis one is the super order Dipnoi, they are the lung fish. Rememberthey go back to the Devonian, and they are a very interestinggroup of animals, because they represent that stage, that criticalstage in the evolution of vertebrates when fish had to evolvelungs in order to be able to obtain oxygen when the water wasstagnate and the oxygen content was low.
Dipnoi "di" means two. "Pnoi" refers tobreathing. And there was a reference to the fact that these guyshave both lungs and gills. They are only 6 living species. Andthey have a very interesting distribution. They are found on thesouthern continents. They are found in Africa, South America andAustralia. And throughout the quarter, we're going to be encounteringdifferent groups of vertebrate animals that have a southern continentdistribution. That used to be very, very troubling to zoo geographers,the people that try to study and understand the distribution ofanimals, why do we find animals where we find them?
How is it that you can find on 3 southern continents animalsthat are very similar to one another, found only in freshwater,you put them in the ocean and they die. How do you get freshwateranimals, restricted freshwater streams on 3 southern continents?There were all sorts of hypotheses in the 50s and 60s to explainthis. Fortunately, the geologist solved the problem by discoveringthat the continents drift.
And these animals originated and were distributed on a singlecontinent, which we call pangea, which was composed of Africa,South America, Australia Antarctica and the continent of Indiawere all one single body of land which, obviously, had an extensiveriver system. And these animals lived in that river system duringthe Devonian.
And then the continents went rocketing off to their presentposition about an inch a year. So that's why we find those animals.And that will be same explanation for the other animals with southerncontinent distributions.
First fossils of these animals come from the earlier Devonian.They also have duroghagus dentition. A couple of species, whentheir ponds completely dry up, the African ones, for example,they completely dry up and these animals burrow down into themud at the bottom of the pond while it's still a little bit soft.And they form a cocoon. They secrete mucus that's on the outsideof their body.
And they can remain for as long as four years burried in thisdried sun-baked mud in a state of what is called "estivation"with a very, very low metabolic rate. Essentially, almost in astate of physiological suspended animation. If the rains comeanytime in the next four years, then the water softens up themud and the animal comes out, and it's able to continue to survive.
Some of them also have burrows in which they deposit their eggs,as you can see at the bottom of the page here.
Now, the other super order in the subclass Sarcopterygii isshown on the next page. And this is the superorder crossopterygii.The abbreviation that I'm using here are the ones that I recommend.It's capital "S" for super and a lower case "s"for sub. So this is the superorder crossopterygii. Again, terygiimeaning fins or wings. In this case it means fins.
These are the lobe finned fishes. It's also sort of anotherreference to the structure of the fins having bones and so forthin them.
And I have already mentioned one of the 2 orders in this superorder,that's the order rhipidistia. These are ones that are the ancestorsof the terrestrial vertebrates, one of those groups of freshwaterDevonian fish, the one that gave rise to the chimpanzee.
This order is one which is a very, very interesting becauseit is placed in the same superorder. We had the order rhipidistiathat I told you about before. These are the ancestors of terrestrialvertebrates.
This ordered order actinistia. So it's the closest living --there are no living rhipidistia; they all went extinct time agoafter giving rise to the amphibians. The order actinistia wasthought to have gone extinct. On the basis of the fossil record,was thought to have gone extinct in the Cretaceous, somewherearound a hundred million years ago.
And then in 1938, a single specimem, living specimem was caughtby some fishermen off the coast the South Africa. And it cameto the attention of a well trained ichthyologists, a young womannamed Courtney Lattimer, this was a big fish, it's like over ameter in length. And she had a museum that she was keeping inthis little town on the coast of South Africa. And she had a dealwith local fishermen that if they found anything weird, she wouldbuy it from them.
So these guys caught this weird fish, and they brought it toher. And she was well enough trained that immediately recognizedit was living example, fossil, if you will of an example thatwas thought to have gone extinct a hundred million years earlier.
And she was able to save enough of the parts to convince theother ichthyologists that she found an actinistian, it's calleda coelacanth, that means that it has some hollow fin structures.
But that was in 1938, the world got involved in some other activitiesfor five or six years shortly after that. And wasn't until thelate 1940s, that scientists were able to really get hot on tryingto figure out where these animals came from. And it was subjectof a lot of excitement among the scientific community to finda living species that was the closest relative of the animalsthat gave rise to the terrestrial vertebrates.
And still there is only a single species known. And it turnsout that that one that was caught, was not caught in the normalplace where the most of the population of these animals is known.It's apparently not unusual for large specimens to kind of wonderaround from the ancestral home.
These animals are now known to be found in very deep ocean waters,waters that are as much as 300 meters deep, 1800 feet.
If you have ever been scuba diving, you know that 30 to 60 feetis a good dive. These guys are down one 1800 feet. So you cansee why people didn't know them well, because human beings don'tspend a lot of time scuba diving at 1800 feet.
And they are also found in a place call the Kamora Islands,which are off the coast the East Africa. Now, the Kamora Islandsis a fairly primitive place. There was an airplane crash in theKamora Islands just last month, and the airplane was hijackedand it crashed into the surf and there was some pretty dramaticfootage of the plane in the surf.
The natives who live in the Kamora Islands -- you are kind oflike fixed for life, financially, if you can catch one of thesecoelacanth fish because these crazy western scientists will payyou a tremendous amount of money for one specimem.
But they are really interesting animals because of their evolutionaryrelationships. They have internal fertilization. Somebody wascutting around on the insides of one of these animals, lookingfor something else, and found a uterus with some babies in it.But the males do not have claspers, so it's not at all clear asto how they mate and achieve internal fertilization.
And there aren't a lot of scuba divers down there watching themdo it, so that's one of the mysteries of the coelacanth. But theyare a pretty interesting group of animals.
Now, the remaining fish that I need to talk about in the timeavailable are all in the other subclasses, not the subclass --so anyway, if you hear me talking about -- I'll sort of rip throughwhen I'm talking about the invasion of land, I'll talk about theRhipidistian and Crossopterygiian fish. That's an order rhipidistia,in the superorder Crossopterygii. Those are ancestors of the terrestrialvertebrates.
The rest of animals that we will be talking about today andare covered on the midterm, are in the subclass actinopterygii.
And the first group is shown on the next page in the IllustratedNotes. This is the infraclass chondrostei.
Now, you are all familiar with the idea that we start off witha kingdom. What's the next lowest taxonomic level of a kingdom?Phylum. And below that class? Class. So obviously we can havesuperclasses and subclasses. Well, we can have also have infraclasses,and that's where we are now.
So we go from superclass to class, to subclass to infra class.And we can also have all 4 of those for any taxonomic level. Wecan even go below. What is below class? Order. And can you havesuperorder?
STUDENT: Yes.
INSTRUCTOR: Right. So if you wanted to have something that wasabove superorder and below infraclass, because infra is as slowas you can get within one taxon, super is as high as you can getin another one. But there are 30,000 species of fish in the taxon.The fish taxonomist like Dr. Baskin, he's a specialist in thecatfish of the Oronocha River. That's how specialized you to haveto be in order to be able to know your discipline.
What we have is an infraclass, which is below subclass, becausesubclass is actinopterygii. So we have subclass, and the nextlevel is infraclass. And we're going to see that we have 2 infraclassesin the subclass. And then the level below infraclass, which isstill above superorder, is series. And we'll get to that beforethe end.
Infraclass chondrostei. There are only 36 living species. Andthe translations of the names of these next three or four groupsare not very informative. They are based upon some old theoriesabout the evolutions of the skeleton of these animals, and it'snow known that those theories are incorrect.
How would you translate chondrostei? Cartilaginous bone, whichis kind of like not a real helpful term.
There are 36 species in the infraclass chondrostei. This isthe last of those five groups of Devonian freshwater fish thathad lungs. And the extinct forms are the ones that are shown hereat the top of the page that are called paleoniscoids. But theliving ones are the ones that I want you to focus on.
There are 3 different types of living chondrosteian fish. Andthey are representative of an early stage in the actinopterygiifish, which is again this big group that's very interesting.
You have a sturgeon shown here at the top of the page. And sturgeonsare very interesting because some of them get to be really huge.There was 20 foot sturgeon caught in Lake Washington about 10or 15 years ago. And they are found throughout the northern hemisphere.
They are found in the ocean and in freshwater, lakes and streams.So what is the term that we use for an animal that goes upstreamto breed? Anadromous.
And they are the guys that produce caviar. They will lay --the females lay these huge masses of eggs. And those masses ofeggs are collected in the freshwater streams in Russia and arepackaged up in tiny cans and charged outrageous amounts of moneyfor them for probably the saltiest thing you have eaten in yourlife. How many of have eaten caviar? How many like caviar? Sowe have couple people with well-developed tongues here. So theseare the sturgeons. They get up to 6 meters in length. And theyare found in the northern hemisphere.
There is also another type which is a really interesting animal,it's called a paddle fish. And the bizarre thing about the paddlefish, it's got this really long nose. If you watch the Life onEarth videotape, you'll see they have a huge mouth and swim aroundwith their mouth open, they are filters eaters.
But the thing that is really startling about them is the distribution.They are found in the Mississippi River of North America and theYangtze River of China. And they are freshwater animals.
So we're faced with this same dilemma of how do you get freshwaterfish in those conditions as well? The geologist solved that onefor us as well, because at the same time that the southern continentswere forming a single giant content called pangea, the northerncontinents were united in a single continent called Lower Asian.
So the paddle fish were an animal that was very interestingin terms of trying to understand its history. There are also anumber of species of these African reed fish, which are shownat the bottom of the page there, and have this bizarre arrangementof their dorsal fins.
These animals all have hetero circle tails, particularly obviousin the paleoniscoids and the sturgeon and the paddle fish. Andthat's, even though they do have a swim bladder, it's not verywell developed. So that hetero circle tail may still be used supporttheir body against gravity, in essence, because they may be indenser water part of the time because their swim bladder is notthat well developed.
Paleoniscoids, the fossil chondrostei evolved into the nextgroup of fish which is a series holostei, but that's in a differentinfraclass. So we now have another infraclass, an infraclass calledneopterygii. And in that infraclass is this new taxonomic levelthat you wouldn't have anticipated the existence of which is calleda series, series holostei.
Again, holostei, "holo" means whole, entire or completebone. So they have complete bone rather than cartilaginous, whichis not a useful term. I wouldn't bother to remember the translationof it.
There are only 2 types of holosteians. They are sort of an intermediatelevel in the evolution of the fish. There are 8 species. One ofthese 2 species is called a bowfin. That's a single species. Andthen the remaining species are called "gar." And thegars are the long skinny guys with the long noises sort of likea cigar-shaped animal. They get up to 4 meters in length, butyou'll see also see little ones.
The living holosteians are all freshwater. The fossil ones --there is a primitive one, a fossil-type, shown at the top of thepage. Those guys are found in marine as well as freshwater. Butthese 2 remnant types, the one species of bowfin and 7 speciesof gar, they are found only in freshwater.
And they have a slight change in the shape of the tail. Noticethat their tail is -- if you look at the back edge of their tailit's symmetrical, unlike the hetero circle tail that we saw herewhere the upper lobe is larger and the fins are on the bottom.This guy's tail is symmetrical. But we can see the base is stillsomewhat asymmetrical.
That's sort of an evolutionary remnant of this earlier stagein this hetero circle tail. So these guys are said to have anabbreviated hetero circle tail. And that represents the intermediatestep. It's the most obvious in the primitive animals and in thegar. The bowfin's tail is not as obviously like that.
There are some other things that distinguish these holosteiansfrom the more advanced group. We need to take a look at that.
If you look at the picture of, say, the sturgeon, notice theseguys -- and you'll see some of these in lab. They all have greatbig scales, bony complicated scales. The scales are reduced somewhatin the holosteians. And we are going to see sort of the ultimatein the evolution of both the tail and scale when we get to thislast series, the series teleostei. And this is the really monstergroup. There are what, 8 species here.
We get to the series teleostei and ichthyologists can't evenagree on how many species there are. They say anywhere from 25,000to 30,000 species. Their uncertainty is five thousand species.That's as many species as a mammalogist know there are mammals.There is only 5000, 200 and something species of mammals. Butthere is around 30,000 species of teleosts, that's the generalterm used for them.
And they are the majority of the different types of fish thatyou have ever seen or encountered in any place in nature or inan aquarium or anything like that.
There are as many is 300 families of these animals. There are4 superorders. That's why we have series here because there areactually 4 superorders in the series teleostei.
But some of the characteristics that they share are shown here.They have a very symmetrical tail. Even the base of the tail issymmetrical. Remember the base of that abbreviated, that holosteiantail, this holosteian tail is symmetrical externally, but at thebase it still has a remnant of that hetero circle tail.
When we look at the tail of a teleostei, it's symmetrical externallyand even at the base of the tail it appears to be very symmetrical.It's only when you look internally that you can see still seesome remnants of some asymmetry in the bones.
So this tail, which is one of the major characteristics of theseries teleostei, is said to be homocercal tail. And one of thingsthat I have had to leave out of lecture to get to this point ontime, was why the tail shapes change and there are some very interestingthings.
But these guys have a homocercal tail. And they also have thegreatest reduction in the size and complexity of their scales.They have a new kind of scale that's not found in any other fish,it's called a "ctenoid" scale. I'm going to write itup here so you can see it, because it's not spelled the way it'spronounced. It's pronounced "ctenoid" as if it didn'thave a C in front of it.
So what we see when we look at the evolution of these very,very important ray fin fish going from the chondrostei to theholostei to the teleostei are a series of changes. A changefrom hetero circle tail to an abbreviated hetero circle tail toa homocercal tail.
Changes in fins, and there are names of changes in the structureof the scales, and not going burden you with the names of thosescales. But we get ultimately to the ctenoid scale which is characteristicof this group.
And if you look at the diagrams or if you read the informationin the lecture transcripts, you'll also see that there is somechanges in the structure of the mouth, the rotation of maxillaand the placement of the various fins.
But the teleost fish in terms of their feeding habits, obviouslythere are carnivores, herbivores, omnivores. Their reproductionspans all the of the possibilities that we have talked about.There are thousands of species of teleost fish that have internalfertilization. There are thousands of species that are viviparous.
If you have ever kept an aquarium of fish and you probably hadsome that gave birth to baby fish in the aquarium. And they havepatterns of reproduction that are imcomprehensive. They have justbizarre things, some species of fish where the male baby attachesto the fin of the female. And the female grows up really big andthe male remains as this little tiny thing that's nothing more than a pair of gonads. And he obtains his nutrients from theblood stream of the female.
And all he does is produce sperm once a year. And that's therest of his life, he's a total ectoparasite. Some of you may knowother species of males like that as well.
That's a quick list through the most numerous of all the vertebrates.