Pheromones and Insect Communication By Jennie Englehart

What are Pheromones? Pheromones are molecules used for communication between organisms. Chemicals involved in communication are known as semiochemical. Pheromones are a subclass of semiochemicals used for intraspecific communication of species.

What are Pheromones? Primer Pheromones have longer term physiological effects on the receiver. Examples of primer pheromones include: Termite Caste determination Locust development rates Any pheromone that has effects on the development of the organism receiving the signal is considered a primer pheromone.

What are Pheromones? Releaser Pheromones illicit an immediate behavioural response in the receiver. Most pheromones are releaser pheromones and are divided into groups based upon function such as: Sexual Aggregation Alarm Recruitment Territorial

What are Pheromones? Chemicals involved in interactions with members of a different species are called allelochemicals and are divided based on the benefits or costs of the signaller or receiver: Effect Allomones Benefit the sender Kairomones Benefit the receiver Synomones Benefit both

Advantages/Disadvantages of Chemical Communication Effective over far distances Effective in environments with reduced visual stimuli Longer lasting than visual or auditory signals Metabolically "inexpensive" because only small quantities are needed   

Advantages/Disadvantages of Chemical Communication Low information content (presence/absence) Difficult to locate sender Long fade time

Specificity In biological signalling systems, selection pressures such as interspecific sexual selection and speciation result in specificity of the signal. Alarm signals may not be species specific. Predator-prey signalling resulting in cross-species evolution of the signal Prey species with shared predators will respond to the same signal Means of gaining specificity: Evolution of large peptide molecules Stereoisomers of phereomone molecule Enantiomers The mosquito, Culex quinquefasciatus, has an oviposition pheromone known as 1-Bombykol Chiral cpd

Coding by olfactory receptors Pheromone molecules strike antennal sensilli and enter a pore system that has tubules leading to the dendritic terminal where transduction of the polarized dendrite occurs. Odour molecules bind to receptor sites on the membrane of the dendrite which give rise to nerve impulses

Coding by olfactory receptors The code of information is passed to the antennal lobe. Terminate in branches on antennal glomeruli. Neurons with cell bodies in antennal lobe synapse with incoming receptor axons and project to lateral lobes of the protocerebrum, sending branches to the mushroom body calyces. Descending neurons with cell bodies in protocerebrum lead from lateral lobes to motor centres in the ventral nerve cord of the insect.

Pheromone Secretary Organs in Insects Exocrine Glands are divided into two types based on their structural organization of secretory cells: Type I Glands with secretory cells of Type I are directly derived from the tegumental epidermis. Secretory cells form a monolayered epithelium either as part of the external body tegument through which they directly discharge their secretory products. Type III More complex The gland is formed by a variable number of bicellular units, each comprising a secretory cell and duct cell. Type I unicellular glands on the antennae of Aleochara bilineata

Primer Pheromones Termite Caste Determination Several primer pheromones affect juvenile hormone levels and other endocrine glands or receivers. Pheromones inhibit differentiation of pseudogates

Primer Pheromones Locust Development Adults and nymphs have separate aggregation pheromone systems Aggregation pheromone produced by gregarious is mediated by primer pheromones, so it acts as a primer that speeds of maturation of females. Nymphal aggregation pheromones have the primer effect of slowing down the development of adults of either sex. Lead to synchronised development of locust.

Sex Pheromones Chemical signalling through pheromones may be an effective means for females to attract males for copulation.

Aggregation and Host-marking pheromones Aggregation pheromones lead to the formation of groups near the pheromone source This may be through attracting organisms or stopping passing conspecifics.

Aggregation and Host-marking pheromones Parasitic insects often mark their hosts using host-marking pheromones Host marking species lay their eggs in hosts of limited size, which can successfully support developping parasitoid larvae

Alarm Pheromones Alarm pheromones are fight or flight responses to stressful environments. Bees release an alarm pheromone soon after stinging a predator.

Alarm Pheromones Slave making ants take advantage of alarm pheromones as well.

Recruitment Pheromones Among social insects, trail following (or recruitment) pheromones are clearly defined. These pheromones are useful in foraging and recruitment to food

Territorial/Home Range Pheromones Pheromones in the form of scent marks have an important role in territorial behaviour in insects. A benefit of scent mark comes from the unique separation of signaller and signal Territorial pheromones have a low energy investment

Queen Recognition Pheromones Pheromones produced by social insect queens perform both primer and releaser functions in controlling colony behaviour. Primer pheromones function by physiologically altering the reproductive systems. The queen also emits a releaser pheromone to attract workers to their queen

Queen Recognition Pheromones Worker produced pheromones Workers do not produce queen pheromone; their main mandibular gland is used in royal jelly. Other worker produced pheromones are often used in alarm and defensive behaviour.

Pheromones and Predator-Prey Interactions Some predators conceal their own ‘odour’ in order to gain acceptance into social insect colonies. This is achieved through the use of cuticular hydrocarbons.

Mutualism Many mutualistic interactions between conspecifics require chemical cues. Interspecific interaction between insects and other species in which both benefit is mutualistic. An excellent example may be the interaction between Ants and lycaenid butterfly caterpillars

Mutualism http://www.youtube.com/watch?v=z3bWqlPL pMg

Evesdropping Pheromonal excretions of insects may be exploited by conspecifics, predators, or parasites through ‘evesdropping’

Pheromone Communication in Social Insects Recognition of kin Recognition of members of the same family in insects may be mediated by chemical cues such as pheromones.

Pheromone Communication in Social Insects Nestmate recognition Nestmate recognition is another common facet of pheromone communication. Recognition of members of the same nest site is vastly important in protection of the nest site.

Application of Pheromones in Pest Management Synthesis of insect pheromones may be exploited industrially by means of synthesizing pheromones of insect pests. These pheromones may be proven useful in protecting crops and residents

Application of Pheromones in Pest Management Pest management may be mediated through: Mass trapping Lure and kill Mating disruption

Conclusion

References P. Howse, I. Stevens, O. Jones,1998 , Insect Pheromones and their Use in Pest Management T. Wyatt, 2003, Pheromones and Animal Behaviour R. Vander Meer, M. Breed, K. Espelie, M. Winston, 1998, Pheromone Communication in Social Insects Happ et al, 1968, Bioassay, Preliminary Purification , and Effect of Age , Crowding, and Mating on the Release of Sex Pheromone by Female Tenebrio molitor Tillman et al, 1999, Insect pheromones—an overview of biosynthesis and endocrine regulation Holldobler et al, 2001, Recruitment pheromone in the harvester ant genus Pogonomyrmex Maclean et al, 2003, Calorimetric investigations on the action of alarm pheromones in the hornet Vespa crabro Wang et al, 2008, Processing of sting pheromone and its components in the antennal lobe of the worker honeybee Branco et al, 2006, Modelling response of insect trap captures to pheromone dose Tschinkel et al, 1967, Sex Pheromone of the Mealworm Beetle Bryning et al, 2005, IDENTIFICATION OF A SEX PHEROMONE FROM MALE YELLOW MEALWORM BEETLES, Tenebrio molitor Tanaka et al, 1985, A Sex Attractant of the Yellow MealWorm , Tenebrio molitor and its Role in mating behaviour http://scienceblogs.com/notrocketscience/2009/04/the_rebellion_of_the_ant_slaves.php http://www.youtube.com/watch?v=z3bWqlPLpMg

Questions.....