1. 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 butter hamlet

2. bluehead wrasse (Labridae) female & juv. male harem dominance hierarchy dominant F becomes M 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 A pprox. 400 mi. long > 1 mi. deep 5315 ft 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. female male end

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

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. Hearing details: sound travels farther & 4.8 x faster in water sound waves cause body of fish to vibrate sensory structure of ear sensory hairs otolith 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. 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 Gnathostomata 1 in Myxini 2 in Cephalaspidomorphi end

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

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

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

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

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