Class Osteichthyes. Bony Fish

Transcription

1 Class Osteichthyes Bony Fish

2 General Characteristics of Class internal skeleton ossified (turned to bone) Paired fins made of rays and spines, or lobed fins swim bladder or lung present bony scales (ganoid, cycloid, ctenoid) gill slits covered by an operculum (single external gill opening) 2 chambered heart

3 Actinopterygii VS Sarcopterygii Ray-finned fins with multiple parallel supports fins controlled by muscles in body wall Lobe-finned Have lungs as well as gills Can live periods outside of water Ex: lung-fish coelacanth

4 Great Diversity 27,000 species Modern Fishes Representing 96% of all living fishes or about ½ the vertebrates Thought to be 5-10,000 undescribed species Diverse Habitat Highest mountains to 8,000m below surface Hot springs (44ºC) to polar seas (-2ºC) Freshwater to extreme salt concentrations

5 The Aquatic Environment: Life in the Water Water has a high specific heat Endothermy is not needed Less O 2 in water efficient gills required Water is dense bony skeleton not needed (but Osteichthyes does) Water will conduct electricity, air does not Can use this to help detect predators or prey Water is more viscous than air Develop methods to propel self

6 Ectothermy vs. Endothermy Ectotherms- Low metabolic rates Little insulation Rapid heat exchange F I S H Endotherms- High metabolic rate Insulation (large quantities) hair/feathers Minimize heat exchange

7 Modern Fish: Agnatha: Jawless fish (primitive) ex: Chondrichthyes: cartilaginous fish ex: Osteichthyes: bony fish ex: Lamprey and Hagfish Sharks Perch, salmon

8 External Anatomy Operculum Dorsal Fins Pectoral Fin Pelvic fin Caudal Fin Anal fin

9 SCALES

10 Figure 24.18

11 Tale of Tails A) - Heterocercal, (B) - Protocercal, (C) - Homocercal, (D) - Diphycercal Sharks Lungfish Perch Coelacanth

12 Swim Bladder Arose from the paired lungs Needed to achieve neutral buoyancy Secreting gas into the bladder as it swims up, and removing gas as it swims down.

13 Types of gas bladders 1. Physostomous Fish Pneumatic duct connect swim bladder to esophagus used for air removal 2. Physoclistous Fish No tube - gas in blood used to fill bladder

14 How Swim Bladder Works Ovale a vascularized area of the swim bladder Used to get air out of the swim bladder Rete mirabile Physoclistous Fish moves gas from the blood into the swim bladder Flow of water is opposite the flow of blood Maximal Oxygen uptake This is called: Counter-current Exchange System

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18 Ventilation in Fish: The Gill Gills: thin filaments/ covered epidermal membrane These membranes fold into lamellae. Richly supplied with blood Covered by operculum (protection and pumping system) Mouth gills out operculum

19 Osmotic Regulation Freshwater (fish are hyperosmotic regulators) Low salt so water tends to enter the bodies osmotically and salt is lost by diffusion outward. Body has mucous covering to try to prevent this, but most exchange occurs in the gills Defense against this Excess water pumped out by kidneys which create very dilute urine Salt absorbing cells move salt from water to blood.

20 Osmotic Regulation Marine (fish are hyposmotic regulators) High salt so fish need to lose water and gain salt. (risk: fish can dry-out) To compensate for water loss a marine fish drinks seawater. Salt is carried by the blood to the gills where they are secreted by salt-secretory cells.

21 Integument Live cells next to environment Mucous layer (to get rid of bacteria?) Scales evolved from armor for protection: A. Cycloid (perfectly smooth) B. Ctenoid (comb-like)

22 Pigment cells-under Neural Control 1. Chromatophores-contain true pigments A. carotenoids B. erythrophores C. melanocytes 2. Iridocytes-contain waste products (guanin) helps to reflect light

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25 Digestion Buccal cavity esphogus stomach intestines Some species don t have a stomach (minnows) possess a pyloric caecae Food swallowed whole Primitive teeth Gill rakers and gill filaments screen objects exchange air Generalized feeders Pharyngeal teeth: last arch in back, help to tear