Overview of Reproduction continued

1. butter hamlet Overview of Reproduction continued 3. Physiology • sex chromosomes: • XY = M; XX = F (most) • ZZ = M and ZW= F(Poeciliidae & Tilapia spp) • some fishes have 3 or more sex chromosomes • sex not under complete genetic control • hermaphrodites--both sexes (many in Serranidae) • usu. one sex at a time • exception hamlet (serranid) • sex changes--bluehead wrasse end

2. bluehead wrasse (Labridae) male • harem • dominance hierarchy • dominant F becomes M female & juv. end

3. Overview of Reproduction continued 3. Physiology continued • parthenogenesis -- egg develops w/o fertilization • Ex: Amazon molly • all female • produce genetic clones • Ex: gynogenesis in Phoxinus (Cyprinidae) • all female • gynogenesis--sperm required, DNA from male not incorporated in embryo end

4. Reproductive Modes in Fishes: • Oviparous -- egg layers; most fishes • internal or external fertilization • Ovoviviparous • internal fertilization • eggs hatch internally • live birth • yolk only nutrition • EX: Lake Baikal sculpins • marine rockfishes • some sharks end

5. Lake Baikal Approx. 400 mi. long 5315 ft > 1 mi. deep end

6. Reproductive Modes in Fishes: continued • Viviparous--live birth • nutrition provided directly by mother • EX: embryonic cannibalism -- a few sharks • fins against uterine wall -- surf perches • placenta-like structures--pericardial tissues in Poeciliidae end

7. nurse shark embryos end

8. lemon shark pup yolk sac and stalk function like placenta and umbilical cord end

9. Reproductive Strategies: Energy Investment egg size: number vs. survivability carp > 2,000,000 salmon 1500-2000 parental investment: energy vs. surviv. nest building parental care mouth brooders--cichlids; ariids end

10. Parental care: pouches (seahorses, pipefishes) end

11. male female end

12. Parental care: guarding smallmouth bass--males bullhead--both sexes end

13. end

14. Sensory Perception • Most fishes have familiar senses: • sight • hearing • smell • taste • touch • Senses generally similar to those of other verts. end

15. Overview of Sensory Differences 1. Chemoreception • taste & smell; distinction blurred in water 2. Acustico-lateralis System • sensing of vibrations; hearing & lateral line 3. Electroreception • sensing electromagnetism from earth & orgs. 4. Pheromones • chemical messages from other fish end

16. 1. Chemoreception details • Olfaction & taste --sense chemicals • Differences: • location of receptors: • olfaction -- special sensory pits • taste -- surface of mouth, barbels • sensitivity • olfaction -- high • taste -- lower end

17. Olfaction details: • Sense food, geog. location, pheromones • structure -- olfactory pit • incurrent & excurrent openings (nares) divided by flap of skin • olfactory rosette -- sensory structure; large surface area • water movement driven by: • cilia • muscular movement of branchial pump • swimming end

18. Olfaction details continued: • Sensitivity varies--high in migratory spp. • Odors perceived when dissolved chem. makes contact with olfactory rosette • anguilid eels detect some chems. in conc. as low as 1 x 10-13 M ! • M = # moles per liter • salmon detect amino acids from the skin of juveniles • sea lampreys detect bile acids secreted by larvae • directional in nurse, hammerhead sharks end

19. Taste details-- short-range chemoreception • detects food, noxious substances • sensory cells in mouth and on external surfaces, skin, barbels, fins • particularly sensitive to amino acids, small peptides, nucleotides, organic acids end

20. end

21. 2. Acoustico-lateralis system • Detects sound, vibration and water displacement • Functions in orientation & balance • Organs: • inner ear (no external opening, no middle ear, no ear drum) • lateral line system end

22. sensory structure of ear otolith sensory hairs Hearing details: • sound travels farther & 4.8 x faster in water • sound waves cause body of fish to vibrate end

23. Hearing details continued: • inertia of otoliths resist vibration of fish • sensory hairs bend, initiating impulse • nerves conduct impulse to auditory region of brain end

24. Hearing details continued: • certain sounds cause insufficient vibration • weak sounds • high frequency • distant sounds • enhancements for sound detection • swim bladder close to ear • swim bladder extensions (clupeids, mormyrids) • Weberian apparatus--ossicles (ostariophysans) end

25. Gnathostomata Structure of Inner Ear: • 3 semicircular canals--fluid-filled tubes w sensory cells (hair-like projections) • 3 ampullae--fluid filled sacs w sensory cells • 3 sensory sacs containing otoliths • otoliths--calcareous bones; approx. 3x as dense as fish • 1 in Myxini • 2 in Cephalaspidomorphi end

26. semicircular canal ampullae lagena otolith utriculus sacculus otolith (sagitta) otolith Fish Inner Ear: Fig. 10.2 end

27. Function of inner ear components: • semicircular canals & ampullae -- • detect acceleration in 3D • utriculus & otolith -- • gravity and orientation • sacculus/sagitta & lagena/otolith-- • hearing end

28. end

29. Lateral line • detects water movement • low frequency vibrations • specialized for fixed objects and • other organisms • Neuromasts -- fundamental sensory structure • single or part of lateral line system

30. cupula epidermis sensory cells background pulse rate Neruomast: Fig 10.4 water decreasing pulse rate increasing pulse rate fish

31. cupulae lateral line pores epidermis lateral line canal Lateral Line (cross section) Fig. 10.5 subeipdermal tissue endolymph end

32. nerve impulse to brain Lateral Line (cross section) Fig. 10.5 vibrations

33. Lateral line details: • often well-developed on head • system poorly developed in lampreys and hagfishes--neuromasts only • often no lateral line in inactive fishes • well-developed in blind cave fishes • functions like a sort of sonar • exploration -- higher speed “swim-by” end