Senses and Communication Flashcards
Mechanoreceptors - where found? types? innervated by? some produce?
- almost anywhere on surface on insect’s body
- tactile receptors (detect movement of objects in environment) or provide proprioceptive cues
- innervated by one+ sensory neurons that fire in response to stretching, bending, compression, vibration , or other mechanical disturbance
- some produce phasic response when stimulated; others generate tonic response
3 broad categories of mechanoreceptors
- Cuticular (bipolar neurons) = 2 classes
- Sub-cuticular (bipolar neurons) = chordotonal organs
- internal stretch/tension receptors (multi-polar neurons
- cuticular mechanoreceptors
(a) projections from cuticle w/ basal socket (hair-like)
- taper from base to tip = trichoid sensilla
- shorter, peg-like = basiconic (chemosensory)
- club-shaped hairs may react to gravitational field
- some act as proprioreceptors
(b) Campaniform sensilla (dome-like)
- structure may vary according to position
- occur on mouthparts, tibial spines, basal segments of antennae, veins close to wing base, ovipositor, haltere
Functions - Exteroception (hair sensilla)
- tactile hairs - all over body
- air movement detectors - stimulated by flow of air over boy + head during flight
- maintain wingbeat, control yaw
- on cerci - respond to sound - gravitational orientation - also involves proprioreceptors
- modified hair sensillar contribute (some Orthoptera) - pressure receivers - depth perception in aquatic insects
- detect changes in vol of plastron
- responds to increasing pressure (depth)
Functions - Proprioreception
- hair sensilla - groups/rows small hairs
- joints between leg segments, basal antennal segments, cervical sclerites, wing base
- movement of one parts w/ another causes hairs to bend - Campaniform sensilla - detect shearing stress
- produce change in shape -> stimulation
- load sensors (direction = force)
- on wing veins control flight stability (Diptera)
- on halteres control wing stroke kinematics
- on antennae control steering and maintenance
- cuticular mechanoreceptors: in summary
2 classes: hairlike or dome-like for:
a. Exteroception (hair sensilla)
- tactile hairs - all over body
- air movement detectors - stimulated by flow of air
- gravitational orientation - also involves proprioreceptors
- pressure receivers - depth perception in aquatic insects
b. Proprioreception (hair and dome sensilla)
- hair sensilla - groups/rows small hairs
- Campaniform sensillar - detect shearing stress
- sub-cuticular mechanoreceptors
- sub-cuticular receptors found throughout body
- consist of single/groups of scolopidia
- convert vibration to nerve impulse
- functions incl: joint proprioception, substrate vibration detection, hearing, wind + gravity sensation in antenna
Joint proprioception
- femoral chordotonal organ - in femur of insect leg, detects position, speed, acceleration + vibration of tibia relative to femur
- Johnston’s organ = in pedicel of antennae, + detects position + movement of flagellum relative to pedical
- Hymenoptera have Janet’s organ - detects flexion of antennal joints
Substrate vibration detection
- subgenual organ = proximal part of tibia
- detects high-frequency acoustic vibrations transmitted through the substrate
- found in all insects except Diptera and Coleoptera
Hearing
- tympanal organ = membrane (tympanum) stretched across frame of rigid cuticle + backed by air sac, so free to vibrate
- vibrations detected by chordotonal organ attached to inside of tympanum
- found on many parts of many insects (not Hymenoptera)
- Orthoptera suborder Ensifera have crista acoustica of 60-80 cells arranged down leg
- sub-genal organs found in most insects - detect some air-borne vibrations
- Sub-cuticular mechanoreceptors: summary
- one or more scolopidia
- converts vibration to nerve impulse
- function incl:
a. joint proprioception - femoral chordotonal organ
b. substrate vibration detection - subgenual organ
c. hearing - tympanal organ, crista acoustica, subgenual organ
d. wind and gravity sensation in antenna - Johnston’s / Janet’s organ
- stretch and tension receptors
- different in having multi-polar neurons
- may be integral part of muscle fibres or connective tissue or have no specific orientation or associated structures
- monitor abdominal distension during feeding
- respond to movement + position of tibia wrt femur
- monitor movement of food along gut
- control oviposition rate
- play key role in controlling wing movements
Transmission of mechanical signals
- how do insects produce communication signals
- what leads to mechanical vibrations?
- transduction of vibrations?
- insects produce communication signals by stridulation, percussion, vibration, click mechanisms + air expulsion
- neuromuscular activity leads to mechanical vibration of some exoskeletal structure
- transduction of vibrations as cycles of compression or rarefaction (reduction of intensity) to surrounding medium
- mechanisms producing substrate vibration may also generate air-borne sounds - one or both may be detected by receiver
Mechanical signals - vibrations via? acoustic signals? air-borne signals used for?
- flight muscles or usually legs transmit vibrations to substrate
- acoustic signals via water or air incl pressure waves + particle movement
- insects using air-borne signals for long distance communication use sound radiators (e.g. part of wing) or timbal backed by air sac
significance of mechanical signals
- intraspecific communication
- reproductive isolation
- attraction from a distance
- courtship
- signalling physiological or genetic quality
- territorial beh + competition
- communication in social insects
8.interspecific communication
