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 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 O 2 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