Lecture 3 Class Chondrichthyes The Cartilaginous Fishes Chapter

Lecture 3: Class Chondrichthyes The Cartilaginous Fishes Chapter 24 pp. 525 -530

I. Classification A. Subclasses 1. Subclass Elasmobranchii -Sharks, skates, & rays -13 living orders, 937 species (only 28 freshwater) -toothed mouth 2. Subclass Holocephali -Chimaeras -1 order, 33 species -flat plated mouth

B. General Characteristics Body structure Spindle-shaped body (fusiform) Anterior rostrum (nose-like structure) Paired/unpaired fins Cartilaginous skeleton Powerful jaws Tooth-like scales http: //www. bio. gc. ca/sh arks/identity-identiteeng. php

C. Order Characteristics 1. Lamniformes -Marine -Pelagic (open ocean) -Dangerous to humans; great white and mako sharks

C. Order Characteristics 2. Carcharhiniform -Marine -Pelagic (open ocean) -Dangerous to humans -Blueshark, tigershark, hammerhead shark Blue Shark Tiger Shark Hammerhead Shark

C. Order Characteristics 3. Squaliformes -Marine -Pelagic (open ocean) -Dogfish shark (dissection)

C. Order Characteristics 4. Orectolobiformes -Marine -Ocean Bottom -Catsharks & carpet sharks

C. Order Characteristics 5. Rajiformes -Marine -Ocean Bottom -Skates Blue Skate Barndoor Skate

C. Order Characteristics 6. Myliobatiformes -Marine -Ocean Bottom -Rays Manta Ray Spotted-eagle Ray Blue-spotted Ray

II. Body Systems A. Skeletal/Muscular 1. Endoskeleton completely cartilaginous 2. Bundled longitudinal muscles, fin levator/depressors 3. Fins: 2 pectoral & pelvic (modified as clasper in males) 1 -2 dorsal Median caudal Anal (most) 4. Placoid scales arranged to reduce turbulence during swimming

II. Body Systems B. Respiratory/Circulatory 1. Gills -5 -7 pair leading to external gill slits 2. No swimbladder or lung

II. Body Systems B. Respiratory/Circulatory 2. Heart -heart with atrium (blood holder) and ventricle (blood pumper); chambers arranged in tandem -aortic arches around gills -cold-blooded (ecto-thermic)

II. Body Systems C. Nervous -adapted to predatory lifestyle 1. Differentiated brain -optic lobes (sight) -olfactory lobes (smellcan detect chemical in 1 part per billion) -cerebrum -cerebellum -medulla oblongata -semi-circular canals (hearing)

II. Body Systems C. Nervous -adapted to predatory lifestyle 2. Lateral line system (sense vibrations from prey from long distances)

II. Body Systems C. Nervous -adapted to predatory lifestyle 3. Electroreceptors (ampullae of Lorenzini) located on shark’s head guide final attack to prey

II. Body Systems D. Digestive 1. System -Mouth -Pharynx with openings to gill slits and spiracles -Short, wide esophagus -J-shaped stomach -Intestine -Spiral valve slows food -Large liver produces bile to breakdown fat and help with buoyancy

II. Body Systems D. Digestive 2. Specialization -Teeth on upper and lower jaws -Front row of teeth are backed by rows of developing teeth

II. Body Systems E. Excretory/Water Balance -opisthonephridic kidney regulates salt balance -rectal gland secretes fluid with high concentration of salt to assist kidney with salt balance in blood

II. Body Systems F. Reproduction Basics 1. True of Most -Separate sexes -Paired gonads

II. Body Systems F. Reproduction Basics -Reproductive ducts open into cloaca -Internal fertilization

II. Body Systems F. Reproduction Basics 2. Maternal Care of Eggs Varies a. Oviparous: Deposit eggs externally b. Ovoviviparous: Retain eggs in uterus, nourish by yolk c. Viviparous: Young develop inside uterus & are nourished by placenta