Download 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