Reading Assignment:

1. Reading Assignment: Chapter 21: Silversides, Flying fish, and Killifish

2. Recap: 1. Chemoreception 2. Acustico-lateralis System 3. Electroreception 4. Pheromones end

3. cupulae lateral line pores epidermis lateral line canal Lateral Line (cross section) Fig. 10.6 subeipdermal tissue endolymph end

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

5. lateral line

6. 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

7. 3. Electroreception • detection of weak electrical current • common in all groups except teleosts • exceptions--teleosts with electroreception • mormyrids -- elephantfishes • Gymnotiformes -- electric knifefishes, elec. eel 650V • Malapteruidae -- electric catfishes (450 V) end

8. Malapteridae -- electric catfish Gymnotiformes -- electric eel Gymnotiformes -- knifefish Mormyridae--elephantfishes end

9. pit sensory cells gel nerve Electroreception structures: • Pit organs in teleosts (0.3 mm in depth) • Ampullae of Lorenzini in marine elasmobranchs (5-160 mm in length) • magnetite crystals in tunas end

10. Electroreception Function: • detection of geomagnetic lines (earth’s mag. Field) • detection of signals given off by muscle • detection of signals produced by conspecifics • electric organs--produce electric field • weak -- most • strong -- electric catfish, electric eel, electric ray--stun prey end

11. distorted electric field voltage end

12. non-conducting object -10 mV +10 mV electric field fish end

13. lesser electric ray end

14. end

15. Pheromones: Defn: Chemicals released onto environment that elicit an immediate and specific reaction in conspecifics. • Schreckstoff: ostariophysan fright substance (pike defecation habits) • Ovarian pheromone elicits courtship behavior in male frillfin gobies • difficult to study end

16. end

17. Behavior & Communication: 1. Schooling 2. Feeding 3. Aggressive Behavior 4. Dominance Hierarchies 5. Resting Behavior end

18. 1. Schooling - moving in close coordinated association • 25% of fishes school • herring schools to 4.5 billion m3 • @ density 0.5-1 fish per m3 • 1/7 th vol. of Lake Sakakawea • consider: Lake Sakakawea 30 billion m3 • 200 mi long; 185 ft max depth end

19. end

20. Advantages of Schooling: • Reduced risk of predation • school may appear as large organism • collective alertness • predator confusion • difficulty of selecting target (flock-shooting) • movement camouflage end

21. sergeant major end

22. Advantages of Schooling continued: • Hydrodynamics--energetic efficiency in swimming • drafting • snout-cone effect • similar to V-formation in birds • 25 birds could get a 70% increase in distance for a given energy expenditure end

23. thrust turbulence streamlines Hydrodynamics of Schooling end

24. Carangidae--bigeye jack school end

25. diagonal banded sweetlips end

26. Advantages of Schooling continued: • increased efficiency in finding food • increased reproductive success end

28. 2. Feeding Behavior • Generalists--wide variety of prey • omnivores -- catfishes • Specialists--specific prey • herbivores -- plant/algae eaters • planktivores • piscivores -- fish eaters • extreme specialists • scale-eating cichlids • parrot fishes -- coral • cookie-cuter sharks end

29. Scaridae--parrot-fishes end

30. cookie cutter shark end

31. cookie cutter shark end

32. caught at depth of 960 m goblin shark end

33. end

34. Feeding Behavior continued: • Opportunists -- take advantage of abundant prey • even if outside normal mode of feeding • non-surface feeders may feed at surface during mayfly hatch • trout feeding on insect hatches end

35. Foraging Factors: • prey size versus mouth size • energetic efficiency--energy spent versus energy gained • prey distance • ease of capture - speed; maneuverability • handling - spines; armor • ease of digestion - composition; scales; bone • energy/nutrient content end

37. 3. Aggressive Behavior • Territoriality - some defend territories, generally for a limited resource • mates • breeding sites • feeding territories • Ex. Tilapia in thermal gradient end

38. Aggressive Behavior continued: • Aggressive encounters: • charges • nips • flare fins • lateral displays • submissive behaviors end

39. Aggressive Behavior continued: • Factors affecting aggressive advantage: • size • prior residency • result of previous encounters • Dominance Hierarchies • often established in interacting groups • Advantages/Disadvantages? end

41. 4. Resting Behavior • “sleeping” or inactive • observed in many species • day night dusk dawn • schools become disorganized • some change color • some do not react to vision or touch end

43. Communication Pheromones--already covered 1. Visual Signals 2. Auditory Signals end

44. 1. Visual Signals: • Color -- important in visual comm. • pigments: • carotenoids - reds, yellows (contribute to green) • melanins - dark red, brown, black end

45. Color continued: • Structural colors: (reflected light) • purines - reflective (colorless) • ex: guanine (iridiophores) cells containing guanine • iridescence: produced when light waves are reflected in parallel end

46. carotenoids clown fish end

47. carotenoids Salvelinus fontinalis--brook trout end

48. carotenoids diagonal banded sweetlips end

49. melanins end

50. melanins Poeciliidae -- black molly end