008b Fish Morphology

Classification Scheme of the Vertebrates Phylum Chordata Subphylum Vertebrata Class Agnatha Class Chondrichthyes Class Osteichthyes Class Amphibia Class Reptilia Class Aves Class Mammalia

Chordate Characteristics

Distribution - Anatomy - Circulation - Respiration Chondrichthyes (370) Placoderm (395-345) Ostracoderm (510-=350 mybp)                                                                                                                      (360) Osteichthyes (395) allows. Class Agnatha or Cephalaspidomorphi, the jawless fishes Subclass (or order) Cyclostomata, the lampreys and hagfishes. (In certain classifications, the lampreys and hagfishes are each considered separate superclasses: Cephalaspidomorphi and Pteraspidomorphi, respectively.) Class Chondrichthyes, the cartilaginous-skeleton fishes Subclass Holocephali, the chimaeras, or ratfishes Subclass Elasmobranchii, the sharks, skates, and rays Class Osteichthyes, the bony fishes Subclass (or order) Crossopterygii, the coelacanth Subclass (or order) Dipnoi or Dipneusti, the lungfishes (In some classifications, the above two subclasses are treated as orders of a single subclass, the Choanichthyes or Sarcopterygii, the lobe-finned fishes.) Subclass Actinopterygii, the ray-finned fishes Infraclass (or superorder) Chondrostei, the primitive ray-finned bony fishes: sturgeons, paddlefish, and bichirs (In some classifications, the bichirs are placed in a subclass of their own, the Brachiopterygii.) Infraclass (or superorder) Holostei or Neopterygii, the intermediate ray-finned fishes: gars and the bowfin (In certain classifications, the gars are treated as a separate superorder, the Ginglymodi. The term Ginglymodi also has been used to designate the gars as an order, but this term has been replaced at the ordinal level by the term Lepisosteiformes; orders are now indicated by the ending -formes.) Infraclass (or superorder) Teleostei or Neopterygii, the advanced bony fishes: herring, salmon, perch. Distribution - Anatomy - Circulation - Respiration lamprey & hagfish

Jaw Development agnathostome gnathostome 1st appeared 400 mya

Basic Anatomy Class Agnatha Possess medial nostril, medial fins, notocord rather than vertebral column 7 or more pr gill pouches present Light sensitive pineal eye Fertilization external Cartilaginous skeleton Lack jaws, paired fins, scales GI track w/out stomach Lampreys and hagfish 100 species

Class Agnatha Lamprey ammocoetes

Class Agnatha Hagfish What do they do? For a long time, people thought of hagfish as scavengers and parasites, probably due to their habit or burrowing into dead or dying animals and eating them from the inside out. In fact, most of their diet is made up of marine worms and other invertebrates. Scientists used to think the hagfish looked primitive as a result of the loss of characteristics often associated with being a parasite. Now common belief is that hagfish just haven't needed to change for the last couple of hundred million years. Now that's a successful body plan and lifestyle! Another ability that had won fame for hagfish is the mass amounts of slime almost instantly secreted as a defense mechanism. Where are they found? Hagfish can be found in the chilly waters of the antitropical north and south. They tend to live on and in muddy sea floors in very dense groups (up to 15,000 in an area). Because females tend to produce large eggs in small numbers, their population sizes suggest a low death rate. One very useful trick hagfish have developed is the ability to tie themselves in knots, and be able to slide in and out of this knot. This can be used to escape predators, to clean themselves of slime, and to work their way into a carcass. This picture shows: A) knotting; this movement is used to clean slime off the body; B) escaping from capture using knotting, a very powerful motion; C) pulling on food by knotting They can also sneeze to unclog their nostrils of their own slime. Hagfish don't really have jaws. Instead they have two pairs of rasps on top of a tongue. They pull meat into their mouths with the tongue, then tear it off the prey with the rasps. Newly hatched hagfish look just like the adults, but have both male and female sex organs. When they mature, they will be either male or female, but have the ability to change from one to the other if the population structure demands it. Although hagfish have a partial skull, they have no back bone, so are not true vertebrates. What skeleton they do have is made of cartilage. How are they used by people? Yes, humans will find a way to exploit even these seemingly useless and repulsive animals. In Korea, almost 5 million pounds of hagfish meat are consumed each year. Hagfish skin is processed into "eelskin" boots, bags, wallets, purses, and other products. Overfishing in Asia has decimated their local hagfish stocks, so the Asian hagfish fishery has turned its eyes towards North America, where these "slime eels" are considered a worthless bycatch. It could mean a boost of over $2 million to the local fisheries, but care must be taken not to damage these stocks as well. Hagfish may not be pretty in most people's eyes, but they serve a purpose and are slow to reproduce. It would take them a long time to recover from over-harvesting. Who can tell what removing them from the local food web would do?   Phylogenetics amongst species (for hard core scientists): There are about 20 species of hagfish divided into four genera (Myxine, Neomyxine, Paramyxine, and Eptatretus). These four groups make a sort of evolutionary continuum with regards to external traits. For example, the Myxine and Neomyxine are considered more advanced than the latter two for several reasons: They have a single pair of common external gill openings. The latter two have two minute separate gill openings (considered primitive). Paramyxine's openings are closer together than Eptatretus' so Paramyxine is considered more closely related to the first two. The eyes in Myxine and Neomyxine are smaller than those of the other two, suggesting a less primitive condition by an adaptation to the dark environment favoured my hagfish.

Basic Anatomy Class Chondrichthyes Sharks, skates, rays

Basic Anatomy Class Chondrichthyes Sharks, skates, rays Posses jaws with teeth, cartilaginous skeleton, paired fins Scales (denticles) have same origin and composition as teeth Possesses 5-7 gills Spiral valve intestine Ureoosmotic strategy Electroreception Lateral line No swim bladder Heterocercal tail Relatively unchanged (480 mybp)

Basic Anatomy                                                                                                                                                                                     

Basic Anatomy Class Osteichthyes

Basic Anatomy Class Osteichthyes Posses jaws with teeth, bony skeleton, paired fins 4 paired gill arches covered by operculum Intestine- simple, no spiral valve Swim bladder Lateral line Homocercal tail Scales- cycloid, ctenoid

Basic Anatomy bony fish

Internal Anatomy anus

Common Measurements

Basic Anatomy Coelacanth Latimeria Swim bladder modified to lungs Paired appendages May have given rise to terrestrial tetrapods Bony head Scales and teeth

Coelacanth Thought to be extinct 80 million years ago Found in 1938 off the coast of the Comoro Islands

Who found it first? 1938 Marjorie Courtenay-Latimer How the coelacanth became known to science  Marjorie Courtenay-Latimer Marjorie Courtenay-Latimer was born in East London on 24th February 1907. From the childhood she was interested in birds and mammals, and fossil collecting was also a hobby of hers. In 1930 she was appointed Curator of the newly established East London Museum which had at that time a very small collection of bird specimens. She worked hard to create a display of natural history of the Eastern Cape. Since fishing was a major local industry, she decided to concentrate on marine life. She interviewed fishing clubs and managers of fishing trawlers; specimens were enthusiastically donated and she made mounts of the small fish. She first met JLB Smith, then a Lecture in Chemistry at Rhodes University College, in December 1933 when he visited the museum during a camping trip at Igoda. He had been advised by doctors to spend his vacations in the open air because of ill health, and his love of angling soon turned into scientific interest .He was very impressed with the work she was doing, and offered to help her with any specimens which might want to classified, because she had on books on fish at the museum. In November 1936 she and her parents visited Bird Island where she spent weeks amassing a huge collection of sponges, seaweeds, sea shells and bird eggs. She also went out to sea in the Irvin & Johnson trawler, Nerine, and made friends with the Captain, Hendrik Goosen, who took her crates of specimens back to East London and thereafter saved interesting fishes from the trawl nests for her attention. Miss Courtenay-Latimer's sketch of the first coelacanth which she posted to JLB Smith On December 22, 1938, Captain Goosen and the Nerine put into East London harbour with the usual catch of sharks, rays, starfish and rat-tail fish. But there was one unusual fish amongst the catch that had been caught in about 70 meters, near the mouth of the Chalumna River. Once ashore Captain Goosen left word at the Museum that there were several specimens at the ship for Miss Latimer. At first she said that she was too busy because she was hard at work cleaning and articulating the fossil reptile bones collected from Tarkastad. But as it was so near Christmas time she decided to go and wish the crew a “Happy Christmas” and took a taxi to the docks. There, attracted by a blue fin amid the pile of sharks, she found a magnificent fish. She and her assistant put it in a bag and persuaded a reluctant taxi driver to take it to the museum in the boot of the car .It measured 150 cm and weighed 57.5 kg. From its hard bony scales with sharp, prickly spines and paired fins looking rather like legs, she knew that it must be some kind of primitive fish. But her greatest problem was to preserve it until it could be identified. It was extremely hot, the fish was too big to go into a bath and she could not find any organization willing to store it in a freezer. Although she was told by experts that it was only a type of rock cod and that she was making a fuss about nothing, she persisted in her attempts to save the fish for science. At first it was wrapped in cloths soaked in formalin but eventually, on the 26th, Mr. Center, a taxidermist, skinned it. Unfortunately the internal organs were thrown away. Marjorie went home disappointed and worried that she had not saved all the soft parts. What she had done, however, was to write immediately to her friend, JLB Smith, and send him her famous sketch of the strange fish. James Leonard Brierley Smith The next part of the story concerns JLB Smith, at that time enjoying a working holiday in Knysna. The next fourteen years of his life were to be dominated by this coelacanth and an almost obsessive search for the second specimen. JLB Smith, born in 1897 at Graff-Reinet, was a self-taught ichthyologist who had published several papers on the marine fishes of South Africa. He knew at once when he opened Marjorie’s letter that. Though the last coelacanths were supposed to have died out with the dinosaurs, he was looking at a drawing of a fossil fish: “One of my most constant and peculiar obsessions had always been a conviction that I was destined to discover some quite outrageous creature” He sent to Cape Town for a copy of Arthur Smith Wood-ward’s Catalogue of Fossil Fishes of the British Museum and, after he had received it, positively identified Marjorie’s unusual fish as a coelacanth. But he did not commit himself or risk his reputation in the scientific community until, some time later; he traveled to East London and saw the specimen for himself: “ Yes, there was not a shallow of doubt, scale by scale, bone by bone, fin by fin, it was a true coelacanth. It could have been one of those creatures of 200 million years ago and come alive again.” He gave the fish its formal scientific name, Latimer chalumnae in honour of Miss Courtenay-Latimer who had preserved it, and the river near which it was trawled. From January to June 1939 JLB Smith and his young wife, Margaret, worked furiously on the first scientific paper describing the coelacanth, completing it just four days before the birth of their son William. All this time the coelacanth, pervasive smell and all, stayed in their house. It was then returned to be displayed at the East London Museum. Thousands of people visited the museum to see the famous fish.

Where was it found?

J.L.B. Smith, Rhodes Univ., Grahamstown On the 22 December, 1938, a fish was netted by fishermen of the Irving and Johnson vessle, Nerine, trawling off the mouth of the Chalumna river on the southeast coast of South Africa. The fish was about 1.5 m (5 ft) long, weighed 57 kg (126 lb), and was covered with deep-blue scales. A young curator of the East London Museum, Marjorie Courtenay-Latimer, as was her usual practise, inspected the catch at the wharf with the permission of Captain Hedrick Goosen, and came across this unusual fish which she kept as a specimen for the museum. She could not identify this fish and wrote a letter, including a rough sketch of the fish, and sent it to Prof. J.L.B. Smith at Rhodes University, Grahamstown, South Africa.The announcement that a Coelacanth had been caught off the Chalumna River mouth was made on 20 February, 1939. And so began the amazing and wonderful story of the Coelacanth, considered to be the zoological find of the 20th century and an event that was heralded with banner reports world wide. To date, approximately 200 fish have been caught in and around the Comoros Archipelago. The second Coelacanth known to science was caught off the Comoran island of Anjouan on the 20 December 1952. This concluded what Prof. J.L.B. Smith had suspected, these waters were the natural habitat of the Coelacanth. The fish was transported across the island and given to Capt.Eric Hunt who salted the fish to preserve it and set sail on his vessel, “Nduwaro” for Mayotte Island. Hunt arrived at Dzaoudzi, Pamanzi, a small Mayotte islet, early morning of the 22 December. The fish was injected with formalin and Hunt telegraghed J.L.B. Smith on the 22 December 1952. Further telegraphs were sent urging Smith to act without delay in order to secure his fish as the French authorities were trying to claim it. Smith and his wife were returning home from an East African expidition on the Dunnotar Castle and when the ship reached Durban on the 24th December, Smith received the cable from Hunt. Because it being Christmas Eve, there were no commercial flights. Smith finally managed to contact the Prime Minister, Dr.D.F.Malan, who also was on vacation at the time, on the 26th December. Permission was granted to use a military aircraft and the Dakota 6832 departed Pretoria on the 28th December, reached Pamanzi on the 29th, returned to Durban that same evening, Grahamstown on the 30th and returned to Pretoria on the 31 December 1952. (This is the only aircraft ever to have flown 3000 miles to collect a dead fish) J.L.B. Smith, Rhodes Univ., Grahamstown

Coelacanth Anatomy Fins: 2 dorsals 2 pectorals 2 pelvics 1 anal 1 caudal

Coelacanth Anatomy Unsegmented notochord Rostral organ Intercranial joint Fat filled swim bladder Ovoviviparous

Anatomical comparison between Sarcopterygian, amphibian, and reptile.

Anatomical Similarities to Sharks: Spiral valve intestine Give birth to live young Long cartilaginous tube instead of backbone Osmoregulatory strategy Anatomical Similarities to Fish: bony head teeth scales

The coelacanth’s phylogenetic classification remains inconclusive Anatomical Similarities to Tetrapods: fat filled lung fleshy lobed-fins circulatory system inner ear tooth enamel intracranial joint- a feature once found in ancient frogs The coelacanth’s phylogenetic classification remains inconclusive

General Life Style Categories Fish Adaptations and Life Styles General Life Style Categories a. pelagic cruisers occurring in water column far away from the bottom (benthic) environment often referred to as "blue water" includes tuna, billfish, blue sharks, mackerel sharks (great whites and mako sharks)

b. demersal bottom-associated fishes, but not usually sitting on the bottom rely on the benthic environment as a source of food, place to reproduce, and/or place of refuge, etc. includes most reef fishes (e.g., butterfly fishes, surgeon fishes, wrasses, parrot fishes, etc.)

c. benthic bottom-dwelling fishes that spend the majority of time sitting on the bottom includes flatfishes, lizard fishes, many scorpion fishes, many hawkfishes, gobies, etc.

Body shape tuna 1) fusiform a) = torpedo-shaped b) allows minimal drag while swimming c) best shape for a pelagic cruise

2) compressed laterally flattened (e.g., butterflyfishes & surgeonfishes) allows for maneuverability in surge environments useful for demersal fishes that hover above the reef exception seen in flatfishes that lie on one side of the body as benthic fishes

3) elongated or attenuated long body (e.g., trumpetfish, cornetfish, eels) seen in demersal fish that either hover motionless in the water) seen also in benthic fishes (e.g., eels) that hide in holes in the reef

4) depressed dorso-ventrally flattened (e.g., frogfishes, scorpionfishes & gobies) broad ventral surface facilitates resting on the bottom seen in many benthic fishes

Body Coloration 1) source of color pigment color - chromatophores for yellows, reds, oranges, browns, & blacks structural color - iridophores (reflection) & light refraction for blues, silvers, & rainbows

2) patterns a) countershading dark blue or black dorsally, white or silvery ventrally results in blue water "camouflage“ observed most frequently in pelagic cruisers

b) camouflage matching the background coloration usually involves having irregular dark blotches and spots typically seen in benthic fishes, especially benthic ambush predators (e.g., frogfishes, gobies, & many scorpionfishes) some fishes (e.g., flatfishes) may exhibit rapid color changes in response to different backgrounds

5) matching downwelling light b) camouflage 5) matching downwelling light Hatchet fish Cookie cutter shark

c) disruptive coloration 1) color pattern breaks up the silhouette of the fish 2) may involve dark bars across the eye and tail region 3) seen in many demersal fishes such as butterfly fishes

d) bars and stripes 1) bars are vertical (e.g., manini) 2) stripes are horizontal (e.g., ta'ape) 3) seen frequently in schooling demersal fishes 4) may confuse potential predators by making it difficult to select individual prey from the school

  e) misdirection 1) false eye spots, etc. 2) observed in many demersal butterfly fishes

f) advertising coloration 1) bright, obvious color patterns 2) possible functions a) advertising a cleaning station (e.g., cleaner wrasses) b) advertising a warning (e.g., nohu) c) advertising for mates (e.g., male parrotfishes) Hawaiian cleaner wrasse Nohu

g) mimicry 1) imitating other creatures 2) seen in a few demersal and benthic fishes 3) examples a) blenny (Aspidontus taeniatus) mimics cleaner wrasses b) shortnose wrasse mimics Potter's angel which sports a defensive spine

g) mimicry 4) leafy sea dragon (Australia)                                      

h) uniform red coloration most often observed in deep-dwelling or night active demersal fishes examples include opakapaka, oweoweo, menpachi, & squirrelfishes

i) noctural versus diurnal color changes j) male versus female color differences k) juvenile versus adult color differences Dragon wrasse Stoplight parrotfish Bluehead wrasse

Fish Anatomy and Physiology

Sensory system vision hearing – inner ear; swim bladder amplifies in some fish olfaction –  olfactory sacs; taste buds lateral lines of fish – detect vibrations in the water Electrical Sense: ampullae of Lorenzini (sharks and rays) – sensitive to electric currents geomagnetic sensory system (long distance migration- tuna)

Sensory system Vision

Sensory system Olfaction Locate prey Find a mate Migration

Sensory system Olfaction Find a mate

Migration Anadromous- salmon can return to the same stream in which they hatched may use land features, currents, salinity, temperature, the sun or magnetic field to get close to land sense of smell die after spawning young return to the sea 2. catadromous –freshwater eels 3. Extensive migration-anatomical basis for magnetotaxis -- magnitite

Sensory system Lateral Line

Sensory system Electric sense Ampullae of Lorenzini pores The ampullae of Lorenzini are small vesicles that form part of an extensive subcutaneous sensory network system.  These vesicles are found around the head of the shark.  They detect weak magnetic fields at short ranges that are produced by other fishes.  This enables the shark to locate prey that are buried in the sand or orient to nearby movement.  Each ampulla is a bundle of sensory cells that are enervated by several nerve fibers.  These fibers are enclosed in a jelly filled tubule which has a direct opening to the surface through a pore.  These pores on the head of the shark are visible to the naked eye, and appear as dark spots in the photo of a porbeagle shark head below. pores Detects weak magnetic fields produced by other fish May also detect geomagnetic orientation

Sensory system Electric sense Paddlefish

Sensory system Electric sense knifefish

Sensory system Electric sense Electric ray The Electric eel (Electrophorus electricus), is an electric fish, and the only species of the genus Electrophorus. It is capable of generating powerful electric shocks, which it uses for both hunting and self-defense. It is an apex predator in its South American range. Despite its name it is not an eel but rather a knifefish. The electric eel generates its characteristic electrical pulse in a manner similar to a battery, in which stacked plates produce an electrical charge. In the electric eel, some 5,000 to 6,000 stacked electroplaques are capable of producing a shock at up to 500 volts and 1 ampere of current (500 watts). Such a shock could be deadly for an adult human. The Sachs organ is associated with electrolocation.[3] Inside the organ are many muscle-like cells, called electrocytes. Each cell can only produce 0.15 V, though working together the organ transmits a signal of about 10 V in amplitude at around 25 Hz. These signals are what is emitted by the main organ and Hunter's organ that can be emitted at rates of several hundred Hz.[3] The electric eel is unique among the gymnotiforms in having large electric organs capable of producing lethal discharges that allows them to stun prey.[4] There are reports of this fish producing larger voltages, but the typical output is sufficient to stun or deter virtually any other animal. Juveniles produce smaller voltages (about 100 volts). Electric eels are capable of varying the intensity of the electrical discharge, using lower discharges for "hunting" and higher intensities for stunning prey, or defending themselves. When agitated, it is capable of producing these intermittent electrical shocks over a period of at least an hour without signs of tiring. The species is of some interest to researchers, who make use of its acetylcholinesterase and ATP.[5][6] The electric eel also possesses high-frequency–sensitive tuberous receptors patchily distributed over the body that seem useful for hunting other Gymnotiformes.[3] Electric eel (really a knifefish) Electric ray

Fish Locomotion

Types of Fins The source of propulsion for virtually all fish comes from: Undulation of the body Paired Fins: Pectoral Pelvic Unpaired Fins: Caudal Dorsal Anal A combination of the above

Anguilliform swimming (Undulation)

Dorsal & Anal Fin Propulsion

Anal Fin Propulsion Black ghost knifefish

Pectoral Fin Propulsion

Dorsal fin                                                              Bowfin Sea horse Knifefish

Pectoral Fin Frogfish

Walking catfish              

Mudskipper

Hydrodynamics: Effects of shape on drag Disk Sphere teardrop Mechanisms for reducing resistance (air more dense than water, so there is more resistance)             a. types of resistance                 (1) frictional resistance -- proportional to the amount of surface area in contact with the water (least for a sphere -- least SA/V);                 (2) form resistance -- drag while moving is proportional to the cross-sectional area of the object in contact with the water                     (a) big for a sphere                     (b) smaller if long and thin                 (3) Induced drag – turbulence (vs. smooth laminar flow) creates vortices (eddies) and increases the drag             b. Generally advantageous to maximize laminar flow – smooth or absent scales; covered with slime --                     streamlined body surface             c. BUT, if the animal is large and fast, you can’t prevent turbulent flow – have controlled turbulence                 (1) swordfish:  rough sandpaper-like skin on their sword                 (2) tunas: scales behind the head (corselet)             d. most streamlined bodies have a teardrop shape balance between frictional resistance, form resistance and induced drag -                 (1) gives the lowest resistance for the largest volume                 (2) ratio of largest diameter to length is about 0.22 (whales, dolphins and tunas)             e. Fast swimmers outperform subs and torpedos by behavioral mechanisms teardrop Laminar flow and turbulence

Slowest Fish Ewa Blenny 0.5 mph

Fastest Fish                                                      Blue-fin tuna 43.4 mph leaping Sailfin 68 mph, leaping

Tuna- long distance swimmer Snapper- short bursts

Respiration Gills

               

Countercurrent Exchange                

Respiratory and Circulatory System

Ram Jet Ventilation

Buccal Pump Ventilation

Feeding Behavior Suction feeding Slingjaw wrasse

Organisms adaptation to buoyancy in water Blubber Swim bladder Pneumatophore                                      

Organisms adaptation to buoyancy in water Air chambers Large liver & heterocercal tail Buoyancy Compensator Device (BCD)                                       lipid reserves in fish without swim bladders (e.g., sharks, mackerels, bluefish, and bonito)             a. distributed throughout the body             b. localized                 (1) pelagic sharks  -- enlarged liver with lipids

Swim Bladder Physostomous Gas Bladder air PHYSOSTOME Chum salmon

Swim Bladder Physoclist gas bladder Rete mirable

No Swim Bladder Missing in fish that swim fast or change depth rapidly (Tuna) Benthic fish (blennies, hawkfish, stonefish…) Sharks, skates, rays Deep water fish

Osmoregulation Osmoregulation- the control of the concentration of body fluids. Diffusion- movement of substance from an area of greater concentration to an area of lower concentration Osmosis- diffusion of water through a semipermeable membrane

Less salt than external environment Marine Fish: hypoosmotic Less salt than external environment H2O continually leaves body continually drinks seawater excretes salt through gills produces small amts of dilute urine

More salt than external environment Freshwater Fish: hyperosmotic H2O continually enters body does not drinks water More salt than external environment produces large amts of dilute urine

Shark and Coelacanth: ureoosmotic Maintains high levels of urea and TMAO in blood excretes salt through rectal gland coelacanth

Hagfish: ionosmotic nonregulator Seawater concentration = internal concentration

Osmolarity in Freshwater and Saltwater Osmolarity- measure of total solutes(dissolved particles) Ions FW m osmol/l SW m osmol/l Na+ 1 470 Cl- 1 550 Ca++ variable 10 Total 10 1000

Concentration of Ions Habitat Na+ Cl- Urea seawater sw 478 558   Habitat Na+ Cl- Urea seawater sw 478 558 hagfish (Myxine) 537 542 lamprey fw 120 96 Goldfish (Carassius) 115 107 Toadfish (Opsanus) 160 Crab-eating frog (Rana) 252 227 350 Dogfish 287 240 354 freshwater ray 150 149 <1 coelacanth 197 199

Inquiry Describe the uses of a countercurrent exchange system. Describe 4 strategies of osmoregulation. Describe the differences between the two types of swim bladders. What is the difference between buccal pump and ram jet ventilation? Describe the difference between anadromous and catadromous.