Fishes Notes Part 2 Cartilaginous Fish vs Bony

Fishes Notes Part 2 Cartilaginous Fish vs Bony Fish Mr. Walker Vertebrate Zoology

Introduction q Jawless fishes evolved into jawed fishes. There are two types cartilaginous and bony fishes. q 12 000 years ago any human venturing into the sea, faced an encounter with the largest fish-eating shark ever to inhabit the oceans, a 15 m monster known as Carcharodon megalodon. q This is not the first cartilaginous fish on earth however, their lineages can be traced back to the Silurian era, 440 million years ago. q Cartilaginous fish are among the oldest surviving vertebrate groups. q The popular belief that sharks have not evolved and have remained virtually unchanged over the centuries, is incorrect. q Sharks have in fact evolved slowly relative to mammals for example, throughout the centuries. q Are they thus primitive animals?

Jaws q Early sharks had their jaws fixed to their braincase anteriorly as well as posteriorly. q Present day sharks have their upper jaw fixed to their braincase posteriorly. q As a result early sharks were not able to protrude their upper jaws as commonly seen with the modern sharks (Great White sharks) also they would have been restricted in the size of pray. http: //www. elasmo-research. org

Teeth q Ancient sharks had smooth-edged, multicusped teeth with a large central blade, flanked by two or more cusplets on either side. q Multi-cusped teeth is still evident today in some species, most modern day sharks have single-cusped teeth. Multi-cusped tooth of early sharks Single-cusped tooth of modern sharks. http: //www. elasmo-research. org

Cartilaginous Fishes • Made up of sharks, skates, and rays • The fish in this class have skeleton composed of cartilage, which is a flexible lightweight material made of cells surrounded by tough fibers of protein. Cartilage is lighter than bones and helps the shark to float. • Unlike jawless fish, they have movable jaws, skeletons, and paired fins • Most live in saltwater and are carnivores • Some cartilaginous fishes are also scavengers • The skin of cartilaginous fishes is covered in placoid scales – They are small toothlike spines that feel like sand paper – They are thought to reduce turbulence of the water flow and thus increase swimming efficiency

Placoid Scales • These scales point towards the tail and helps to reduce friction from surrounding water when the shark swims

Shark Senses Tapetum lucidum • Lateral Line System Reflects light in the eye

Sharks • Sharks have a fusiform body shape, which is a smooth, torpedo-shaped body , that reduces turbulence when swimming • The largest sharks, the whale shark and basking shark , feed on plankton and floating plants and animals – Like other filter feeding fish they have gill rakers to help filter the water

Sharks • The mouth of a typical shark has 6 to 20 rows of teeth – When a tooth breaks or wears down a replacement tooth moves forward to take its place – Sharks may use up to 20, 000 teeth over its lifetime – The structure of each species’ teeth has been adapted to that species’ feeding habits • Example: Sharks that eat large fish or mammals have big, triangular teeth with saw-like edges that hook and tear flesh

Adaptations of Cartilaginous Fishes • Gas exchange: occurs in the gills, which lie behind the head – Fast-swimming sharks push water through their mouths, over their gills, and out their gill slits by swimming – Most cartilaginous fish pump water out of their gills by expanding and contracting their mouth cavity and pharynx – Rays and skates draw water through their spiracles, which are two large openings on the top of their head behind their eyes

Adaptations of Cartilaginous Fishes • Elimination of Waste: Instead of releasing ammonia cartilaginous fishes use energy to convert ammonia into a compound called urea – Sharks retains large amounts of urea in their blood and tissues, which raises the concentration of solutes in their body to the same level of that found in water – The concentration of sodium and chloride in a shark’s body is less than the concentration found in sea water, therefore these ions diffuse into the body across the gills and are absorbed with food. – The rectal gland removes excess sodium and chloride ions from the blood and releases them to the rectum for elimination

Adaptations of Cartilaginous Fishes • Cartilaginous fishes maintain their position in the water in two ways: – 1. The caudal and pectoral fins generate lift as the fish swims and it can remain at the same level in the water as long as it keeps moving – 2. The storing of large amounts of low-density lipids in their livers. The lipids give sharks buoyancy by reducing the overall density of the body

Reproduction in Cartilaginous Fishes • Fertilization occurs inside the female’s body (Internal Fertilization) • Internal Fertilization occurs when the male transfers sperms into the female using modified pelvic fins called claspers

Mermaid Purses? • Young are born in three ways – 1. After fertilization the female lays large yolky eggs – 2. The eggs develop inside the females body and the young are born alive – 3. The mother nourishes the developing sharks while they are in her body • No cartilaginous fish provide parental care for their young after they are born or hatched § Shark egg sacs

Sharks Comes in all Sizes Whale Shark Dwarf Dog Shark 6. 5 in to 59 ft.

Rays and Skates Family: Myliobatidae) • Rays and Skates have flattened bodies with paired winglike pectoral fins, and in some species whiplike tails • Rays have diamond or disk shaped bodies, while skates have triangular bodies • Rays and Skates are less than 1 meter long • They both are primarily bottom dwellers – Their flat shape and coloration camouflage them against the floor of their habitats – They feed on mollusk and crustaceans

Rays & Skates The major difference between skates and rays is the way in which they reproduce. Rays are viviparous (live bearing) Skates are oviparous (egg laying), releasing their eggs in rectangular cases sometimes called "mermaid´s purses".

Bradyodonti • Includes forms with an upper jaw fused to the braincase and a flap of skin, the operculum, covering the gill slits. • The Bradyodonti includes the chimaeras and ratfish, which are relatively rare, deep-water, mollusc-eating forms. Chimaera Ratfish

Summary of Chondrichthyes • Class Chondrichthyes: (Sharks, skates, and rays) Large in size (average 2 meters). Body is fusiform with a herterocercal caudal fin. Pelvic fins in males modified as claspers. Skin with placoid scales or without scales in elasmobranchs. Cartilaginous skeleton. Digestive system with J shaped stomach. 5 -7 pairs of gills. No swim bladder or lung. Brain of two olfactory lobes, two cerebral hemispheres, two optic lobes, cerebellum, medulla oblongata. Lateral line system present and developed senses of smell. Sexes are separate. Oviparous, ovoviviparous, or viviparous; direct development; internal fertilization. Some species in rare conditions can use parthenogenesis.

Shark Anatomy for Dissections

Bony Fishes: Class Actinopterygii: Ray Finned Fishes -Fishes in Idaho: Clupeidae-Herring Family Salmonidae-Salmon/trout Family Cichlidae- Tilapia Family Poecilliidae-Mosquitofish Family Ictaluridae-Catfish Family Gadidae- Burbot Family Petromyzonidae-Lamprey Family Cyprinidae-Minnow Family Percidae-Perch Family Esocidae-Pike Family Cottidae-Sculpin Family Acipenseridae-Sturgeon Family Catostomidae-Sucker Family Centrarchidae-Sunfish Family Percopsidae-Troutperch Family Cobitidae- Weatherfish Family Class Sarcopterygii: Lobe Finned Fishes (example Lungfish)

Summary of Ray-Finned Fishes • Class Actinopterygii (Ray-finned fishes) Skeleton made of bone. Scales can be ganoid, cycloid, ctenoid or absent. Paired and median fins present. Jaws present. Teeth usually present with enamaloid covering. Respiration by gills and covered with an operculum. Swim bladder often present with or without a duct connecting to esophagus. Two chambered heart. Sexes usually separate. Fertilization usually external. Nervous system of a brain with small cerebrum, optic lobes, and cerebellum. •

Summary of Lobe-Finned fishes • Class Sarcopterygii (Lobe-finned fishes) Skeleton made of bone. Paired and median fins present. Jaws present, teeth are covered with true enamel and typically are crushing plates restricted to palate. Gills supported by bony arches and covered by an operculum. Swim bladder vascularized and used for respiration and buoyancy. Nervous system with a cerebrum, cerebellum, and optic lobe. Sexes separate; fertilization external or internal.