mechano and chemoreceptors Flashcards
define mechanoreception
the ability for an insect to detect and respond to certain kind of stimuli; notably touch, sound and changes in pressure or posture in its environment
= tactile or proprioceptive cues
what are the 3 broad categories of mechanoreceptors in insects
1) cuticular (bipolar neurons) = 2 classes
2) sub-cuticular (bipolar neurons)= chordontonal organs
3) internal stretch/tension receptors (multi-polar neurons)
what are the two classes of cuticular mechanoreceptors
1) hair sensilla = projections from the cuticle with a basal socket
2) campaniform (dome like) sensilla
outline the structure of hair sensilla which act as cuticular mechanoreceptors
= taper from base-tip –> trichoid sensilla
= shorter, peg-like –> basiconic
outline the structure of campaniform sensilla which are a class of cuticular mechanoreceptors
- structure vary according to position
- occur on mouthparts, tibial spines, basal segments of antennae, veins close to wing base, ovipositor and haltere
what are the function of hair sensilla and list the ways this is performed
EXTEROCEPTION = detecting information from the outside environment
PROPRIORRECEPTION = perception or awareness of the position and movement of the body
how do hair sensilla allow exteroception
- Tactile hairs – all over body
- Air movement detectors – stimulated by flow of air over body
and head during flight
* Maintain wingbeat, control yaw
* On cerci – respond to sound - Gravitational orientation – also involves proprioreceptors
* Modified hair sensilla contribute (some Orthoptera) - Pressure receivers – depth perception in aquatic insects
* Detect changes in volume of plastron
* Responds to increasing pressure (depth)
how do insects allow proprioreception
1) hair sensilla = groups/rows of small hairs
- joints between leg segments, basal antennal segemnts, cervical sclerites, wing base
- movement of one parts which causes the other hairs to bend
2) campaniform sensilla - detect shearing stress
- produce change in shape from stimulation
- load sensors which show direction and force
- ones on wing veins control flight stability
- ones halteres control wing stroke
- on antennae control sterring and maitence
what is shearing stress
a type of stress which acts a s coplanar with cross section of material
what are subcuticular mechanoreceptors
found within the cuticle throughout the body consisting of single or groups of sclopidia and whos function is to convert vibration into nerve impulses
what are some of the other functions of sub-cuticular mechanoreceptors
joint proprioception
substrate vibration detection
hearing
wind and gravity sensation in the antennae
outline how sub-cuticular mechanoreceptors function for joint proprioception
1) the femoral chordtonal organ in the femur of the insect leg detects position, speed, acceleration and vibrayion of of the tibia relative to the femur
2) the johnstons organ is located in the pedicel of the antennae detects position and movement of flagellum relative to the pedicel
3) hymenoptera have a janets organ which detects flexsion at antennal joints
what organ detects substrate vibration
subgenual organ
= proximal part of the tibia
= detects high frequencey acoustic vibrations transmitted through substrate
= found in all insects but diptera and coleoptera
what is the tympanal organ
a membrane (the tympanum) which is stretched across a frame of rigid cuticle and backed by air sacs allowing it to vibrate
outline how hearing occurs in insects
the tympanal organ vibrates and the vibrations are detected by the chorodontal organ attached to the inside of the tymanum
= this organ can be found in many parts of insects but subgeneal organs can also detect some air borne vibrations
in summary the functions of the sub-cuticular mechanoreceptors are a) joint proprioception b) substrate vibration detection c) hearing and d) wind and gravity sensation
name the organs involved in each of these functions
a) femoral chordotonal organ
b) subgenual organ
c) tympanal organ, crista acoustica and subgeneal organ
d) Johnstons/Janet organ
outline stretch and tension receptors
- Different in having multi-polar neurons
- May be integral part of muscle fibre or connective tissue or have no
specific orientation or associated structures - Monitor abdominal distension during feeding
- Respond to movement and position of tibia wrt femur
- Monitor movement of food along gut
- Control oviposition rate
- Play key role in controlling wing movements
outline the transmission of mechanical signals
- insects produce communication signals in many different ways
- neuromuscular activity leads to mechanical vibration of some exoskeletal structure
- the transduction of vibrations as cycle of compression and rarefaction to the surrounding medium
= mechanisms producting this vibration may also generate airborne sounds which can be detected
outline the significance of mechanical signals
1) intraspecific communication
2) reproductive isolation
3) attraction from a distance
4) courtship
5) signalling physiological or genetic quality
6) territorial behaviour and compeititon
7) communication in social insects
8) interspecific communication
what are the different mechanisms to producing sounds and vibrations
1) percussion = impact of part of the body on substrate or another part of the body e.g. death watch beetle
2) stridulation = production of vibration by moving cuticular ridge over tooth ridge e.g. orthoptera
3) tymbal mechanisms = vibrations produced when timbal buckles
4) oscillation of flight muscles = produce throacic and wing vibrations e.g. waggle dance in honey bees
5) air expulsion = expel air through the mouth or enlarged abdominal spiracle
outline chemoreception in insects
- Stimulation by chemicals involves senses of
olfaction and gustation by gustatory receptors - Possess ‘taste’ receptors on many parts of body
- Some used for purposes unrelated to feeding
- Detect chemicals on dry surfaces (= contact
chemoreception) - Range of olfactory receptors (remote
chemoreception) sensitive to odours - Mechanism of detection allows overlap between
olfaction and contact chemoreception (taste) - Processes in CNS different for each mode
outline some examples of chemoreception mediated sense organs
1) Sensilla tichodea = hair like structures on the distal region of the proboscis of moths
2) sensilla basiconica - peg like and can be found on the antennae of mosquitos
3) sensilla coeloconica = peg sunken pits e.g. apical antennae of leaf cutter ants
outline chemosensory sensilla in insects
olfactory sensilla clustered on the antennae, maxillar and labial palps and the genitalia of some insects
- contact of these distributed across the entire body but cluster in specific regions and can be grouped on mouthparts
= none on the manibles
= high density on legs and some antennae
what is the difference between a pheromone and an allelochemical
P= mediates interaction between conspecifics
A= involoved in interactions between different spp
what are the different functions of pheromones
1) aggregation
2) sex
3) alarm calling
4) marking
5) trails
6) social
what is the different types of allelochemicals and what is the difference between them
1) Allomones = benefit only to the emitter e.g. deterrents or repellents
2) Kairomones = benefit only to the receiver e.g. pollinator spp
3) Synomones = benefit to both the emitter and reciever e.g. flower and pollinator
