Transcript Document
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 Assigned readings • Natural flow regime • Poff et al. 1997 Natural flow regime • River management not working • New paradigm is importance of natural flow = five components • Human alterations of flow • • • • Dams Urbanization, tiling, drainage Levees Groundwater pumping Ecological functions of flow regime • High flows, low flows • Duration, timing Ecological responses to altered flow regime • Mortality of fishes below dams • Loss of habitat • Loss of flooded habitat Solution to hydrologic alteration? • Manage toward natural flow regime • Controlled releases by dams • Dam removal • Alternative ag practices Riverine Ecosystem Synthesis Thorp, Thoms, Delong Review of River Ecosystem Concepts • RCC • Flood Pulse Concept • FPZs 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. Internal structure and life systems 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 Respiration • Terrestrial animals must supply O2 to cells without drying out • Insect solution relies on waterproof cuticle that allows air to enter at only a few places = spiracles Respiration • Spiracles are invaginations of the epidermis • Cuticle lined air conducting tubes = tracheae • Tracheae branch and end close to tissues as tracheoles Breathe air or water? • Atmospheric breathers: • Spiracles covered with hairs to prevent water from entering. Breathe air or water? • Plant breathers: • Spiracles modified to pierce plant air channels – Some dipteran larvae, beetle larvae. 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) Breathe air or water? • Closed tracheal systems • = no spiracles • Tracheal gills = outgrowths – In every aquatic insect order, in some species 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 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 The Alimentary Canal • As food moves through gut it will travel from: • Mouth->Pharynx->Crop->Proventriculus & Gastric caeca->midgut->Ileum->Rectum 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 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 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 Integument • Exoskeleton = noncellular covering – Cuticle – noncellular outermost layer – Epidermis – single layer, secretes cuticle – Epidermis and cuticle separated by subcuticular space • Cuticle + Epidermis = Integument Integument: The cuticle • Insect cuticles are diverse: – Permeability – Transparency – Rigidity • Cuticle is laminate – Two major portions: • Epicuticle • Procuticle Integument: The Epicuticle • May be smooth or sculpted • Rich in lipid and protein – High wax production • If epicuticle is intact, insects lose little moisture 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 Epidermis • Epidermis = continuous layer that seals hemocoel from subcuticular space • Secretes cuticle Molting • Arthropods periodically shed exoskeleton to allow for growth and/or metamorphosis • 7 steps during each molt cycle 1. Apolysis • Retraction of epidermal cells from endocuticle • Formation of subcuticular space • Molting gel secreted • New cuticle laid down 2. Epicuticle formation • Epicuticle laid down • It is extensively wrinkled 3. Procuticle deposition • Formation of chitin microfibrils • Endocuticular layers of old cuticle digested • Enzymes in molting gel initially inactive 4. Ecdysis • Old cuticle splits along middorsal suture • Cast skin = epicuticle and exocuticle • Endocuticle recovered and recycled into new procuticle 5. Expansion • Insect swallows air • Insect swells, removes wrinkles in epicuticle 6. Hardening and darkening • New procuticle stabilized • Exocuticle formed 7. Endocuticle deposition • Depositing chitin and protein takes time • Some insects deposit one lamina of endocuticle every 24 hours Note: Ecdysis under hormonal control Dichotomous Key