1. Exam Tuesday x pages, x questions –Natural flow regime: –Hydrology of streams: –RCC; FPC; RES –Arthropod taxonomy / evolution: –Insect physiology: Lab quiz: –x general invert ID –x insects to order –Label a diagram

2. Assigned readings Natural flow regime

3. Poff et al. 1997 Natural flow regime River management not working New paradigm is importance of natural flow = five components

4. Human alterations of flow Dams Urbanization, tiling, drainage Levees Groundwater pumping

5. Ecological functions of flow regime High flows, low flows Duration, timing

6. Ecological responses to altered flow regime Mortality of fishes below dams Loss of habitat Loss of flooded habitat

7. Solution to hydrologic alteration? Manage toward natural flow regime Controlled releases by dams Dam removal Alternative ag practices

8. Riverine Ecosystem Synthesis Thorp, Thoms, Delong

9. Review of River Ecosystem Concepts RCC Flood Pulse Concept FPZs

11. Creates new predictions about river functions Stochastic processes different in different patches? Communities distributed among FPZs. S highest at transition zones. % Autochthonous productivity varies among FPZs.

12. Internal structure and life systems

13. Exoskeleton Arthropods are supported by exoskeletons –Skeleton on outside –Muscles attach to inside Exoskeleton is like medieval suit of Armor –Articulating plates = sclerites –Membranes connect sclerites

14. Respiration Terrestrial animals must supply O 2 to cells without drying out Insect solution relies on waterproof cuticle that allows air to enter at only a few places = spiracles

15. Respiration Spiracles are invaginations of the epidermis Cuticle lined air conducting tubes = tracheae Tracheae branch and end close to tissues as tracheoles

16. Breathe air or water? Atmospheric breathers: Spiracles covered with hairs to prevent water from entering.

17. Breathe air or water? Plant breathers: Spiracles modified to pierce plant air channels –Some dipteran larvae, beetle larvae.

18. Breathe air or water? Temporary air stores –Bring bubble underwater Belostoma spp. Dytiscus spp. Permanent air stores –Hairs or meshworks hold gas film = plastron –E.g., riffle beetles (Elmidae)

19. Breathe air or water? Closed tracheal systems = no spiracles Tracheal gills = outgrowths –In every aquatic insect order, in some species

20. Circulatory System Open circulatory system Blood leaves dorsal blood vessel; percolates through body cavity (hemocoel) Thoracic portion of dorsal blood vessel conducts hemolymph to head Small pumps move hemolymph into legs, wings and antennae

21. The Alimentary Canal Gut of an insect is tube that runs from mouth to anus Gut functions include: –Digestion of food –Absorption of nutrients across gut wall to hemocoel Gut = integumental invaginations from mouth and anus (foregut and hindgut) Midgut = nonintegumental connection between foregut and hindgut

22. The Alimentary Canal As food moves through gut it will travel from: Mouth->Pharynx->Crop->Proventriculus & Gastric caeca->midgut->Ileum->Rectum

23. Excretion Excretion is removal of waste products of cellular metabolism Malpighian tubules = principle excretory organs of insects At junction of Midgut and Hindgut Absorb waste from hemocoel and deposit in hind gut

24. Exoskeleton Exoskeleton = series of tubes –Hollow tubes stronger then rods –Size limited, mammal-sized arthropods require prohibitively thick exoskeleton –larger animals subject to stress related injuries; endoskeleton protected by surrounding tissue

25. Hydrostatic Skeleton Relaxed membranous areas can be extended when muscles compress blood-filled body Hydrostatic skeleton maintains shape of soft-bodied larvae, and freshly-molted insect

26. Integument Exoskeleton = noncellular covering –Cuticle – noncellular outermost layer –Epidermis – single layer, secretes cuticle –Epidermis and cuticle separated by subcuticular space Cuticle + Epidermis = Integument

27. Integument: The cuticle Insect cuticles are diverse: –Permeability –Transparency –Rigidity Cuticle is laminate –Two major portions: Epicuticle Procuticle

28. Integument: The Epicuticle May be smooth or sculpted Rich in lipid and protein –High wax production If epicuticle is intact, insects lose little moisture

29. Integument: The Procuticle Divided into layers –Exocuticle – hard dark outer portion –Endocuticle – softer and lighter in color –Made of chitin, protein and lipid Chitin is: –colorless polysaccharide –clumped into microfibrils –microfibril orientation compensates for stress forces

30. Epidermis Epidermis = continuous layer that seals hemocoel from subcuticular space Secretes cuticle

31. Molting Arthropods periodically shed exoskeleton to allow for growth and/or metamorphosis 7 steps during each molt cycle

32. 1. Apolysis Retraction of epidermal cells from endocuticle Formation of subcuticular space Molting gel secreted New cuticle laid down

33. 2. Epicuticle formation Epicuticle laid down It is extensively wrinkled

34. 3. Procuticle deposition Formation of chitin microfibrils Endocuticular layers of old cuticle digested Enzymes in molting gel initially inactive

35. 4. Ecdysis Old cuticle splits along middorsal suture Cast skin = epicuticle and exocuticle Endocuticle recovered and recycled into new procuticle

36. 5. Expansion Insect swallows air Insect swells, removes wrinkles in epicuticle

37. 6. Hardening and darkening New procuticle stabilized Exocuticle formed

38. 7. Endocuticle deposition Depositing chitin and protein takes time Some insects deposit one lamina of endocuticle every 24 hours Note: Ecdysis under hormonal control

39. Dichotomous Key