Sensory system Flashcards
Mechanoreceptors Functions
Detect physical forces: touch, tensions, or vibrations
* Tactile receptors: Perceive stimuli outside the insect
* Proprioceptors: Respond to the deformations, tensions and compressions in the body. They also provide information on posture and position
* Auditory receptors: Respond to vibrations
Tricoid sensilla
Most common and least modified mechanoreceptor
* Tactile: Perceive currents of air/water and direct touch
* Proprioceptor: When grouped together in the form of hair plates, they are used to tell the position of the body and body parts
* Auditory: Respond to vibrations produced by nearby sounds
Campaniform sensilla
- Similar totrichoid sensilla except the hair replaced by domelike plate
- Respond to pressure and cuticle deformation.
- Common at the base of the wings and halteres in flies.
Chordotonal sensilla
- More complex and internal
- Attached to the cuticle at one or both ends
- Proprioceptors: Very sensitive to pressure changes and to muscle tension
- Auditory: Very sensitive to vibrations. When clustered together, form highly evolved auditory organs
Johnston’s organ
- Present in the second antennal segment (pedicel) of all insects
- Detect movements of the antennal flagellum
Tympanal organ
- Specialized auditory organ found in a few insects.
- Very sensitive to airborne vibration
- Consists of a thin cuticle lying on top of an air-sac and linked to chordotonal organs
Chemoreceptors
Detect aqueous (taste) and airborne chemicals (smell)
* Sensory dendrites are exposed to the environment through small openings in the cuticle.
Olfactory (distant) receptors
Perception of chemicals in a vapor state.
* Mostly found on antennae
* Detect chemicals in the air at low concentration
* Large number of sensory neurons
* Mulitporous
Gustatory (contact) receptors
Perception of chemicals in aqueous state.
* Detect substances in a high concentration
* Very abundant on mouthparts
* May also be found on tarsi, antennae, or ovipositor.
* Uniporous
Photoreceptors
Percetion of light
* Compound eyes
* Ocelli
* Stemmata
* Dermal detection
Compound eyes
- Principal visual organ of insects
- Most adult insects & nymphs
- Made up of ommatidia
Ocelli
- In addition to compound eyes in many insects
- Ocelli can only detect changes in light intensity
- Insects have usually 3 ocelli
Stemmata
- Found mostly in holometabolous insect larvae
- Provide info about light intensity, size, shape, movement and colour of objects but no images
- From 1 to 6 on each side
Insect vision
- Insects perceive image, in composite or mosaic form
- Insects detect movement much faster than we do
- Insects with large compound eyes have a wide field of view
- Colour vision is shift towards the shorter wavelenth
