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Fish Notes: Skin, Scales, Color, Defense, Migration, and Reproduction

Learn about the fascinating world of fish skin, scales, coloration, defense mechanisms, migration patterns, and reproductive strategies. Explore the diversity of scales, the importance of coloration, and the various ways fish protect themselves in their aquatic environment. Discover how migrations help fish find breeding grounds and food sources, and delve into the intriguing world of fish reproduction, including spawning behaviors and unique reproductive strategies. This comprehensive guide provides insights into the complex lives of fish and their remarkable adaptations.

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Fish Notes: Skin, Scales, Color, Defense, Migration, and Reproduction

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  1. Fish Notes Part 3 Skin, scales, color, defense,migration and reproduction

  2. Skin • Entire skin of fish is alive (unlike vertebrates) • Covered in scales – grow from pockets in skin • Not covered by a layer of dead skin, hair or feathers • Covered by water at all times • Scales covered by a thin layer of living cells  epidermis

  3. Protection is provided by a thin covering of mucus which reduces friction and lessens the possibility of bacteria and parasites from invading the skin • “fish” odor – found in slimy covering – serves as a means of communication • Scales can also help the fish “taste” the water—some fish have taste buds on their scales & fins!

  4. Scales • Have about the same # for life – count rings on them for growth (although can be tricky…) • Fish w/o scales  lampreys, freshwater catfish • Eels appear “scaleless” but actually have small scales deeply embedded in the skin

  5. Scales (con’t) • Placoid Scales • Tooth-like • like sandpaper • Ex. sharks and skates

  6. Ganoid Scales • Large and plate-like – made of bone • Generally fused to form a hard bony covering • Ex. primitive fish, gar, sturgeon

  7. Scales (con’t) • Cycloid scales • Overlapping covering like shingles • Thin/flexible • Smooth • Found in soft-rayed bony fish • Ex. salmon

  8. Ctenoid scales • Overlapping like cycloid but rough • Comb-like edge • Spiny-rayed bone fish  mackerel

  9. Coloration • Fish show a variety of colors with a variety of functions: • Species recognition during breeding • Camouflage • Warning/poisonous • Advertisement for willingness to remove parasites from other fish (remora)

  10. Two types of cells are located in fish skin: • Chromatophores – star shaped pigment cells – fish can change colors by contracting or expanding these • Iridocytes – contain reflecting granules that work like small mirrors Those in the open water are less colorful. Why?

  11. Defensive strategy • Other than feeding • Modified scales  sharp spines, armor, camouflage • Prehensile tails (sea horse) • Sudden expansion (puffer fish) • Coloration • Countershading – dorsal area is darker than ventral • Disruptive contrast – violently contrasting coloration – ex. stripes, etc.

  12. Defensive strategy • Secretions (ink/poisons) • Schooling – safety in numbers – some part time and some do this their whole life • Intimidating behavior = bluffing, raised fins, open mouth, rapid darting, grinding teeth, rubbing spines

  13. Migrations • 2 underlying needs are directing seasonal migrations and they are: • Locating a suitable place to breed • Seeking food • Migratory fish are grouped according to the type of water in which they breed…

  14. Anadromous • Adult life in ocean – return to fresh water to breed – ex. salmon, sturgeon, shad, smelt, sea lamprey **Salmon live several years in the sea and mature sexually then return to rivers. They don’t feed once in freshwater – rely on stored fat. Eventually they reach the exact stream where they were born. Females dig a shallow next where she lays her eggs. The males fertilize and then both die. How do they find the exact place? They use chemical smells as a homing technique.

  15. Catadromous • Adult life in freshwater – return to sea to breed • Ex. eel Some fish remain in the ocean and move on definite pathways b/n feeding areas and spawning areas – ex. herring and tuna

  16. Reproduction • Fish reproduce sexually in many ways • Most do it externally (females release eggs, males release sperm – millions of eggs – called spawning) – sharks are internal • Terms to know: • Milt – fish sperm produced in testes • Roe – fish eggs produced in ovaries • Some are dioecious (most) but some hermaphroditic (they are able to produce sperm and egg in combination – have ovotestes – ex. lancelfish, tripod fish, top minnow (may self-fertilize) • sex reversal – a means to improve reproductive success – maintains an even number of males and females – ex. grouper, sheepshead, and wrasse

  17. Reproduction • For some the urge to breed in controlled by hormones  timing is controlled by: • Temperature • Day light length • Salinity • Tide cycles • Courtship rituals (provide for species identification) • Bright color display • Nest building • Aggression • “dances” • Specific sounds

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