Fat Body Flashcards
What does the fat body consist of?
Loose sheets, ribbons or loves of cells lying in the body cavity (haemocoel)
How are the cells in the fat body in communication?
Via gap junctions
What is the function of the fat body?
. Energy store/ liberation in the form of glycogen, fat, protein
. Translates nutritional information into systemic growth-promoting signals
. Regulates blood sugar- dietary amino acids activate TORC1 signalling in fat cells and induce the production of rely signals that promote the release of insulin/like peptides by brain insulin producing cells
. Synthesises major haemolymph proteins
What are the three ways insects can get rid of waste nitrogen and how are they different?
. Ammonia- toxic, must be excreted in diluted form or rapidly volatilised
. Urea- less toxic, more soluble-still needs water for elimination
. Uric acids- non-toxic, can be excreted dry and stored used by most terrestrial insects
What are the three basic conditions of the hindgut depending on an insects diet and habitat? Give examples of when they are seen
. General condition- seen in most insects (locusts)
. Liquid feeder- seen in blood feeders or sap eaters
. Water stress- seen in insects eating dry food
Describe the general condition in which nitrogen is removed from the body?
. Malpighian tubules absorb water, solutes and urate/ uric acid (nitrogenous waste) from the haemolymph in the body cavity
. Rectangle then reabsorbs water and solutes from the gut, leaving urate/ uric acid precipitate behind
. Water moves passively though the system attracted by the hypoosmotic solution in the middle of the tubule
(Most insects- locusts)
Describe the liquid feeder condition of excretion and osmoregulation. Give examples of animals that have this system
. E.g. Assassin bug (Rhodnius), mosquitoes, Tse Tse fly blood meal
. Distal Malpighian tubules absorb water, solutes and uric acid/ urate from haemocoel
. Proximal Malpighian tubules (can increase their rate of clearing water from the haemocoel by 1000 times) then reabsorb water and solutes leaving uric acid
. Tubules are then flushed out and uric acid excreted by the next blood meal
Describe the water stress condition of excretion and osmoregulation and give example species
. Coleoptera or larval Lepidoptera living in very dry conditions eating grain or flour. Water can be a absorbed from the air via the rectum
. Distal region of the Malpighian tubules (secrete a lot of KCL draws water from the tubules- it is then absorbed in Haemoplymph) are wrapped around rectum
. More efficient water absorption from atmosphere into haemplymph
How are trachea efficient at delivering oxygen to metabolically active tissues?
. Gas exchange occurs through diffusion, and diffusion of oxygen in air is 10,000 times faster than in liquid
. The tracheal system presents a huge surface area for gas exchange
Trachea have spirally arranges cuticular thinking’s designed to keep them open called what?
Taenidia
Describe ganglia
Collection of nerve cells that control that segment
Why are ganglia bigger in the thorax than abdomen?
Because these control the wings, legs (more complicated), so need more neurons
Describe the central nervous system in insects
. Ventral
. A ganglion for each body segment
. Each ganglion can act as a mini brain controlling functions of that segment
. Tiny
. Structures in each ganglion are often paired or bilateral, one on each side of the body
What do connectives do?
Connect ganglia
Describe segmental nerves
In pairs from each ganglion each nerve carrying signals (from sensory organs (neurons) to muscles)
What are trachioles?
Branches of trachea in cells. Supply oxygen right to the tissue that need it
What can trachiole cells do?
Can control water flow by secreting water into the trachioles and slowing respiration
What does holopreustic mean?
Breathing
Explain the open system of gas exchange in aquatic insects
Open to the air and get O2 that way:
. Insects protrude their spiracles beyond surface film. Trachea run length of tail and down body and deliver O3 to tissues that need them (e.g. Eristalis and nematoceran fly larvae)
. Insects insert spiralled into air bubbles or carry their own bubbles of air. Makes them very buoyant when they stop swimming (e.g. water beetles)
Explain the closed gas exchange system in aquatic insects
Diffusion of O2 from water
. Very thin cuticle overlaying fine network (black fly larvae)
. Tracheal fills (zygoptera larvae) - just a fine layer of chitin- then trachea underneath. Some have gill-like structures in their rectum
. Rectal gills (dragonfly larvae)- muscular nature of rectum- jet repulsion
Which of carbon dioxide or oxygen diffuses through tissues more readily?
CO2
What percentage of CO2 is lost through the cuticle and tracheae?
25% via cuticle
75% tracheae
What happens to the waters ability to hold oxygen as temperature increases?
Decreases- less O2 in water
What are the units of expression of dissolved oxygen?
Ppm- parts per million
Give the methods insects control respiration
. Secondary respiration centres: stimulates by lack of O2/ accumulation of O2
. Diffusion control (brain): level of fluid in trachioles can be varied, spirackes can be opened or closed
. Ventilation control (thorax): Vary intensity or frequency of movements
. Coordinated by ganglion of each segment
The hear is a muscular contractile tube held in place by what? Perforated with vertical skits called what?
Alary muscles
Ostia
Describe the aorta and where it carries blood
Is slender anterior prolongation of the heart
Carries blood to the head
The heart rate is automated, wth an intrinsic rhythm. What are these is adult and larva and pupa?
. Adult (rest) 40-50 bpm, (active) 110-140bpm
. Larva 80-90bpm
. Pupa 10-12bpm
Describe diastole
Blood is drawn into the heart through the Ostia under negative pressure (sucked)
Describe systole
. Blood driven forward in heart cavity, exiting in head
. Direction may reverse for short periods <24% of total
What are the flight muscles controlled by?
One or two motor neurons
Where is the optic lobe?
Behind the eye
Give the names of the three ganglia (and there purpose) that the brain is made up of
- Protocerebrum H1- processing signals arriving from the ocelli and compound eyes (via the optic lobes)
- Deutocerebrum H3- processing signals arriving from the antennae
- Triticerebrum H3- processing signals arriving from head and body
Where is the optic lobe?
Behind the eye
Give the names of the three ganglia (and there purpose) that the brain is made up of
- Protocerebrum H1- processing signals arriving from the ocelli and compound eyes (via the optic lobes)
- Deutocerebrum H3- processing signals arriving from the antennae
- Triticerebrum H3- processing signals arriving from head and body
What are the 5 main types of sense organs?
. Mechanoreceptors . Auditory receptors . Chemosensors . Temperature and humidity receptors . Photoreceptors
Describe mechanoreceptors
. Monitor: touch, muscle/ cuticle (outside or inside) tension, balance or stance of an insect
. Usually scattered over body surface
. Rarely have specialised organs (except halteres)
(Can cause locusts to swarm)
Describe auditory receptors
. Excited by sound . Located in a number of places (Antennae-Hemiptera Cerci- crickets and cockroaches First abd. Segment- locusts Tibia- grasshoppers, wetas)
Describe chemoreceptors
Smell/olfactory organs: usually on antennae e.g. mosquito
Taste- gustatory organs- usually found on ore-oral good cavity. (Palps; antennae(some Hymenoptera), tarsi(Lepidoptera etc.), or wing edges)
Processed differently from each other in the brain
Describe auditory receptors
. Excited by sound . Located in a number of places (Antennae-Hemiptera Cerci- crickets and cockroaches First abd. Segment- locusts Tibia- grasshoppers, wetas)
Describe chemoreceptors
Smell/olfactory organs: usually on antennae e.g. mosquito
Taste- gustatory organs- usually found on ore-oral good cavity. (Palps; antennae(some Hymenoptera), tarsi(Lepidoptera etc.), or wing edges)
Processed differently from each other in the brain
Describe auditory receptors
. Excited by sound . Located in a number of places (Antennae-Hemiptera Cerci- crickets and cockroaches First abd. Segment- locusts Tibia- grasshoppers, wetas)
Where are the taste neurons in drosophila?
Taste sensilla on the mouth parts, the tarsal segments of the legs and wing margins
What do insects taste?
Sugars, bitter substances, salts, pheromone and somatosensory stimulants
Describe temperature and humidity receptors
. Found on antennae, maxillary palps or tarsi
. Mainly in bloodsucking ectoparasites
Describe the two types of photoreceptors
. Ocelli (simple eyes, single ocelli: lens) - usually 3, in triangle on head - perceive light intensity changes - can detect horizon position . Compound eyes
Describe compound eyes
Many units called ommatidia having a lens plus 8 photoreceptors with their light capturing surfaces the rhabdomeres.
See page for examples
Describe compound eyes
Many units called ommatidia having a lens plus 8 photoreceptors with their light capturing surfaces the rhabdomeres.
See page for examples
What are the 2 hypotheses of flight development/ evolution
. Wing is a new structure- paranormal hypothesis- wing oriented as an extension of the thoracic tergum, or paranormal lobe
. Is a modified old structure- limb branch hypothesis proposes that the wing emerged by modification of a pre-existing dorsal limb branch (was there in ancestors, just didn’t look like a wing)
What preadaptive functions may have selected for an appendage that would become as wing?
Protection for legs Covers for spiracles Thermoregulation Sexual display Concealment Predator avoidance by extending an escape jump
What are 2 candidates for wing origin?
. Stylus of silverfish
. Tracheal gill of mayfly
