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Fig. 8.17

Fig. 8.17. Fishes - Biology Regulation of Internal Environment Chondrichthyes Concentration of solutes in blood similar to seawater Retain urea in blood (toxic to most other vertebrates) Absorb water through gills and skin Salts excreted by kidneys and rectal gland Osteichthyes

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Fig. 8.17

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  1. Fig. 8.17

  2. Fishes - Biology • Regulation of Internal Environment • Chondrichthyes • Concentration of solutes in blood similar to seawater • Retain urea in blood (toxic to most other vertebrates) • Absorb water through gills and skin • Salts excreted by kidneys and rectal gland • Osteichthyes • Concentration of solutes much lower than seawater • ~14 ‰ vs. ~35 ‰ • Drink seawater • Salts excreted by kidneys and chloride cells in gills • Kidneys produce small amounts of urine

  3. Fig. 8.18

  4. Fishes - Biology • Sensory Systems • Smell/Taste • Most fishes have a highly developed sense of smell • Detect food, mates, predators, navigational information • Sensory cells in olfactory sacs on both sides of head • Sacs connected to outside through nares (nostrils) • Sharks especially sensitive to scent of blood (1 ppm) • Salmon locate home stream by scent (imprinting) • Taste with taste buds in mouth and on lips, fins, skin, barbels • Lateral line • Clusters of sensory cells (neuromasts) in small canals lining head and along sides of body • Sensitive to vibrations in water • Used for orientation, detection of prey and currents, avoidance of predators and obstacles

  5. Fig. 8.19

  6. Fishes - Biology • Sensory Systems • Electroreception • Found in Chondrichthyes • Ampullae of Lorenzini • Detection of prey, navigation • Extremely sensitive (may be less than 1 nV/cm) • Can detect a marine mammal’s electric field 3 m away • Used in combination with other senses • Inner ears • Calcareous otoliths rest on sensory hairs • Detect sound waves + changes in fish attitude • Help to maintain equilibrium and balance • Can be used to determine age of fish

  7. Fishes - Behavior • Schooling • Displayed by ~4000 species • Some fishes school throughout life, others only when juveniles, feeding • School sizes vary • Atlantic herring – 4580 m3 • Pacific herring – 15 miles long! • Positioning in school may involve • Vision • Other senses (mechanical vibrations, olfaction, hearing) • Types • Mobile schools • Usually consist of single species, size range • Stationary schools • May contain multiple species, sizes • Functions • Protection against predators • Increased swimming efficiency • Beneficial when feeding • Beneficial when mating

  8. Swimming Feeding Predator Avoidance Fig. 8.21

  9. Fishes - Behavior • Migration • Generally related to feeding and/or reproduction • Diel • Horizontal • Vertical • Large Scale • Ex – Skipjack tuna feed in Eastern Pacific, spawn in Western and Central Pacific

  10. Fig. 8.22

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