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The shape of fish is dictated by the properties of water and the lifestyle of the fish

Head Trunk Tail . Pectoral fins Pelvic fins Nape Lateral line Dorsal fin spiny dorsal soft dorsal Vent (anus). Snout Mouth Nares Eye Operculum Branchiostegal membrane. Caudal fin Caudal peduncle Adipose fin Anal fin.

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The shape of fish is dictated by the properties of water and the lifestyle of the fish

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  1. Head Trunk Tail Pectoral fins Pelvic fins Nape Lateral line Dorsal fin spiny dorsal soft dorsal Vent (anus) Snout Mouth Nares Eye Operculum Branchiostegal membrane Caudal fin Caudal peduncle Adipose fin Anal fin The shape of fish is dictated by the properties of water and the lifestyle of the fish

  2. Basic body shapes Fusiform – streamlined, elliptical in cross-section, narrow peduncle trout Compressiform – similar to fusiform but laterally compressed crappie Depressiform – body flattened from top to bottom skates and rays – NOT FLOUNDER Sagittiform - elongated body, dorsal and anal positioned posteriorly. muskellunge Anguilliform – long snake-like body – attenuated eels, lampreys globiform – short round body – truncated puffer fish

  3. Body shape often indicates the lifestyle of the fish Rover-predator – actively swims to find prey – streamlined, terminal mouth, forked tail – bass, trout Lie-in-wait predators/ ambush predators – sagittiform body, rapid acceleration - muskellunge Surface-oriented fish – depressed head, superior mouth, dorsal fin posterior – mosquitofish, top-minnows Bottom fish - depressed head, subterminal mouth, barbels common - catfish Deep-bodied “Pickers”- compressiform body, short head, large eye, paired fins anterior (pect high on body),

  4. Mouth orientation superior – up turned terminal - front inferior – below The mouth is often protusible – forms a tube for suction feeding Fins Dorsal and Anal fins – used for stability in swimming Two dorsals (spiny, soft) is a derived trait Caudal fins Heterocercal – unequal lobes Homocercal – equal lobes Isocercal – no lobes

  5. Pelvic fin – may be positioned forward in derived fishes (abdominal, thorasic, jugular) Pectoral fin – may be positioned higher and oriented vertically on body in derived fishes, used to grasp substrate in some benthic species (Cottus). Modified as wings in flying fish Adipose fin – fleshy fin between dorsal and caudal – vestigal? primitive characteristic Spines at the origin of dorsal, anal, pelvic, pectoral fins is a derived trait

  6. Other body characteristics Scales – support and protect outer covering skin is waterproof, protects from parasites Placoid scales – Chondrichthyan fishes large dentin, very thick Ganoid scales –gar – diamond shaped, ganoin Teleosts (derived bony fishes) ossified Cycloid – circular scales with a smooth edge Minnows and suckers • Ctenoid – derived characteristic, exposed portion of scale has small projections that “rough up” the surface of the fish – aids in making the fish hydrodynamic (think golf ball) sunfishes, darters

  7. Scales – continued Fish scales are dermal and covered by an epidermis – up to 30 cells thick. Epidermis contains mucus glands. Scales grow in an asymmetric pattern focus – center of growth circuli – bony ridges annuli – thickened ridge used for age determination Scales that are lost or damaged can be quickly replaced – inner area contains no information about growth.

  8. Gas bladder saltwater fish bladder 5-6 % of volume freshwater 7-10% Physostomes - bladder connected to esophagus by pneumatic duct – ancestral condition Gas is forced into the bladder by gulping air and buccal contraction. Fishes with physostomous bladder are usually found near surface.

  9. Physoclists - bladder not connected to esophagus Gas gland with (rete mirabile) – secrete gas from blood Oval – absorbs gas back to blood stream Some other fishes have reduced bladders (fast water) or no bladder (benthic) Circulation and Respiration Oxygen - air is 21% oxygen partial pressure .21 * 760 (1 atmosphere) = 159.6 mm Hg 296 mg Oxygen/ liter (ppm) Water has low oxygen solubility at 5 C, water holds 12.76 mg oxygen/l (4.3% of air) Temperature, pressure, and total dissolved solids affect solubility: at 35 C, water holds 6.94 mg oxygen/l (2.3% of air)

  10. Circulation Gill structure gill arch gill filaments lamella Blood flow/ Water flow - Counter current orientation Teleosts usually have four functional gills Pseudobranch – 1st gill arch (visceral arch) is attached to operculum – receives oxygenated blood 4 pair of branchial arches - respiratory Pharyngeal arch – last element – may contain pharyngeal teeth - Cyprinids

  11. Gill ventilation – buccal/ opercular pump – ram ventilation paddlefish, tunas, billfish Alternative modes of respiration Cutaneous – more important for larvae, eels, bullhead catfish, walking catfish (Clarias), Respiratory tree/ labyrinthine organ – modified gill, does not collapse when exposed to air walking catfish, snakeheads Vascularized tissue: in mouth – electric eel, snakeheads chambers off esophagus – lungfishes, bowfin, gar stomach – South American catfishes Obligate air breathers – Clarias, snakeheads, Arapaima, lungfishes, Facultative air breathers – gar, bowfin, American eels

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