Quinone-aggregation pheromone interaction in the red flour beetle

Short Communications on bird orientation (e.g. Griffin 1982), and some negative results have surely not been reported. F o r example, a recent large series o f rigorously controlled h o m i n g pigeon releases by M c l s a a c & Kreithen (unpublished data) failed to find any indication of the magnetic storm effect reported by K e e t o n et al. (1974) a n d L a r k i n & Keeton (1976). These kinds of results suggest t h a t we should devote more effort to replicating past studies lest we risk erecting o u r syntheses a t o p a house o f cards. It seems clear that we have a good deal more to learn a b o u t the role o f terrestrial magnetism in bird orientation. D u r i n g the period of collection of these data, I was supported at various times by the Air Force Office of Scientific Research, Research F o u n d a t i o n of S U N Y , and the N a t i o n a l Science F o u n d a t i o n . F r a n k M o o r e a n d Becky H o l b e r t o n kindly commented on a draft of the manuscript. KENNETH P. ABLE Department o f Biology, State University o f New York, Albany, N Y 12222, U.S.A.

References Able, K. P. 1974. Environmental influences on the orientation of nocturnal bird migrants. Anita. Behav., 22, 225 239. Able, K. P. 1982. The effects of overcast skies on the orientation of free-flying nocturnal migrants, ln: Aeian Navigation (Ed. by F. Papi & H. G. Wallraff), pp. 38 49. Berlin: Springer-Ve~ag. Able, K. P. & Cherry, J. D. 1986. Laboratory and field studies of avian migratory orientation. In: Migration: Mechanisms and Adaptive Signoqeanee (Ed. by M. A. Rankin), pp. 51(~525. Contrib. Mar. Sci., Suppl. Vol. 27. Port Aransas: University of Texas Marine Science Insitute. Batschelet, E. 1981. Circular Statistics in Biology. London: Academic Press. Gauthreaux, S. A., Jr. 1980. Direct Visual and Radar Methods for the Detection, Quantification, and Prediction of Bird Migration. Clemson, South Carolina: Clemson University. Griffin, D. R. 1982. Ecology of migration: is magnetic orientation a reality. Q. Rev. Biol., 57, 293 295. Keeton, W. T., Larkin, T. S. & Windsor, D. M. 1974. Normal fluctuations in the earth's magnetic field influence pigeon orientation. J. comp. Physiol., 95, 95 103. Kirschvink, J. L., Jones, D. S. & Macfadden, B. J. (Eds). 1985. Magnetite Biomineralization and Magnetoreception in Organisms. New York: Plenum Press. Larkin, R. P. & Sutherland, P. J. 1977. Migrating birds respond to Project Seafarer's electromagnetic field. Science, N.Y., 195, 777-779. Larkin, T. S. & Keeton, W. T. 1976. Bar magnets mask the effect of normal magnetic disturbances on pigeon orientation. J. comp. Physiol., 110, 227 231.

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Moore, F. R. 1977. Geomagnetic disturbance and the orientation of nocturnally migrating birds. Science, N.Y., 196, 682-684. Ossenkopp, K.-P. & Barbeito, R. 1978. Bird orientation and the geomagnetic field: a review. Neurosci. Biobehay. Rev., 2, 255-270. Richardson, W. J. 1974. Spring migration over Puerto Rico and the western Atlantic, a radar study. Ibis, 116, 172 193. Richardson, W. J. 1976. Autumn migration over Puerto Rico and the western Atlantic: a radar study. Ibis, 118, 309 332. Southern, W. E. 1978. Orientation responses of ringhilled gull chicks: a re-evaluation. In: Animal Migration, Navigation, and Homing (Ed. by K. SchmidtKoenig & W. T. Keeton), pp. 311 317. Berlin: Springer-Verlag. Wiltschko, W. 1983. Compasses used by birds. Cornp. Biochem. Physiol., 76, 709 717. (Reeeiced 5 June 1986; revised 14 August 1986," MS. number." AS-404)

Quinone-aggregation Pheromone Interaction in the Red Flour Beetle Tribolium are colonizing species whose adults a n d larvae utilize a b r o a d spectrum of foods which c o n t r i b u t e to their success as stored p r o d u c t pests. W h e n disturbed, glands present on the thorax a n d a b d o m e n o f T. castaneum secrete b e n z o q u i n o n e s which provide protection against predators. W e b b (1966) showed that quinones inhibit lipid synthesis and induce lipid desaturation. Sonenshine et al. (1982) observed that p - b e n z o q u i n o n e s affected the neutral lipid c o m p o n e n t in the p h e r o m o n e of Dermacentor variabilis and suggested that quinones m a y inhibit p h e r o m o n e activity by inhibiting the secretion of the oil droplets in which the sex p h e r o m o n e is dissolved. We suspected that the aggregation p h e r o m o n e produced on the male femora (Faustini et al. 1981) was dissolved by benzoquinones. If this is true, then a chemicallymediated system for controlling p o p u l a t i o n density could be postulated. W h e n Tribolium are overcrowded, b e n z o q u i n o n e s are released which m a y dissolve the aggregation p h e r o m o n e , causing the insects to disperse or to suppress aggregation behaviour. Therefore, an a t t e m p t was m a d e to evaluate the relationship between the p h e r o m o n e a n d the q u i n o n e s as part o f a chemical c o m m u n i c a tion system. Tribolium with large globules on b o t h p r o t h o r a cic femorae were selected for testing in petri dishes. T r e a t m e n t beetle populations consisted of 25, 50, 100 a n d 500 individuals. Each p o p u l a t i o n contained 10 m a r k e d male beetles (150 days old) used four times each for a total of 40 m a r k e d males for each density. The t r e a t m e n t p o p u l a t i o n s were not

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fed during the experiment. Control populations of the same densities as the treatment populations received 2 g of fresh whole-wheat flour daily. All populations were monitored daily for 5 days. All marked males were removed and the presence or absence of the pheromone globule was recorded. Fifty pheromone globules were placed in 1 l~l of crude benzoquinones and tested to determine whether they could be dissolved by the defence secretions. Globules were also compared to synthetic quinone standards for solubility data. Quinone secretions were collected by two methods. (1) The beetle was immobilized with forceps, and the secretion was taken from the thorax and abdomen using a minuten pin. It was then placed in a glass tube and stored at - 4 0 ~ (2) A glass aeration chamber holding 400 adult Tribolium was used to collect insect volatiles. Air was drawn over the insects by vacuum applied down-stream of a holder filled with Tenax. After aeration, the Tenax was extracted in hexane. Quinone secretions were analysed for 2-methyl- and 2-ethyl-l,4-benzoquinone by gas liquid chromatography (GLC). Synthetic quinone standards were chromatographed before and after G L C analysis to ensure integrity. For populations of 25 and 50 adults, globule dissolution did not differ significantly from the control until day 3. For densities of 100 adults, dissolution occurred on day 2 (Table I). However, a significant reduction in the number of male globules occurred during the first day in the treatment that consisted of 500 adults. In all of the experimental populations, the groups deprived of food showed a significantly greater loss of globules than did the groups that were fed. Therefore, the absence of food affected globule dissolution. As seen in Table I, there was a positive correlation between the rate of globule dissolution and population density (r = 0.796).

When a globule ( N = 50) was placed in contact with 1/~1o f the crude secretion, a 100% dissolution occurred within 1 min in all replicates. Furthermore, when synthetic benzoquinones were placed in contact with the globular material, the globules dissolved within 1 min. When we attempted to remove the pheromone globule from the insect with a minuten pin, we observed that the benzoquinones secreted from the thoracic gland diffused over the prothorax and up the leg and dissolved the wax containing the aggregation pheromone. The presence of at least two quinones was established by partitioning the secretion on thin layer chromatography (TLC) plates. G L C analysis of the crude abdominal and thoracic gland secretion and aeration collection revealed seven peaks, with the first two compounds in relatively large amounts. Peaks I and II had G L C retention times that were identical to the synthetic 2-methyl- and 2ethyl- 1,4-benzoquinones. Secretions from the abdominal and thoracic glands in T. castaneum can dissolve the waxy globules containing the aggregation pheromone. Chemical evidence suggests that two components of the gland secretions are benzoquinones. Under stressful conditions of overcrowding and lack of sufficient food, the globules disappeared. We propose that this disappearance was due to the action of benzoquinones. Thus, the quinones could regulate population density in T. castaneum by counteracting the effect of the aggregation pheromone. Attraction to males by either sex depends upon the presence of the aggregation pheromone. Faustini et al. (1981) showed that neither sex was attracted to 90-day-old males without globules obtained from overcrowded cultures. Peters & Barbosa (1977) stated the mortality response of most species is generally exhibited as density reaches a certain species-specific, environmentally

Table 1. Daily and overall comparison of globule dissolution between treatment (without food) and control (with food) at various population densities expressed in percentagest Days Population density 25 50 100 500

1

2

3

0"0 4.0 8"0 0.0 5.0 12"0" 5.0 15.0" 25-0* 1.0" 19"0" 47.0*

4

5

12-0" 25.0* 33.0* 51"0"

16.0" 35.0* 46.0* 68.0*

Rate (slope of globule dissolution x 100)+ Standard error 4.87 a 9.00 b 9.75 b.c 12.35~

0.65 0.65 1.30 1.30

f Differences between treatment and controls were tested at 99% confidence level (Wilcoxon's rank sum; *P < 0.001). Four replicates were performed at each density for both controls and treatments. ++Differences between multiple linear regression lines for the four densities tested. Percentages flanked by the same letter are not significantly different (Student's t-test, t=0.05).

Short Communications

modulated level. There would be no selective advantage to producing aggregation pheromone when the population exceeds the carrying capacity for the unit of food source. At low densities where a surplus of food is available, aggregation pheromone is produced, and henzoquinones are not released. We propose that the quinones are the triggering device that causes enhanced emigration due to increased population levels. In previous observations on the behaviour of flour beetles it was noted that T. castaneum and T. confusum differed in their aggregation and dispersal behaviour. Males of both species aggregated, but females tended to disperse evenly. Overcrowding is a factor that will influence the speed of exit, and beetles tend to aggregate especially during the evening period, when flying activities would normally take place (see Sokoloff 1974 for a review). Conditioning of the medium affects the aggregation or dispersal behaviour in Tribolium. T. castaneum is repelled by flour that has been occupied previously by other beetles, resulting in the insect emigrating as the nutritive value falls. Although in the present study we did not demonstrate an interaction with dispersal, previous investigators have shown that behaviour is influenced by the biological environment. Mondal (1985) reported that medium may be conditioned by the aggregation pheromone and quinones depending upon the number and sex of insects, and the duration of occupation. Dependence upon certain conditions would dictate whether the medium was either an attractant or a repellent to T. castaneum larvae. The evidence suggests that the quinones can be multifunctional, and are thus an example of pheromone parsimony (Blum 1970). They may act as epideictic pheromones at high population densities by dissolving aggregation pheromone globules. The significance of the quinone pheromone interaction can be explained in terms of individual selection. Prokopy (1981) suggested that where there is an exhaustable food resource, there is a range of optimal population density. He suggested that selection favours individual fitness and full exploitation of the resources, but not to the point of overcrowding. We believe that a high population density has detrimental effects at the individual level for both sexes. D. L. FAUSTINI* W. E. BURKHOLI)ERt *Philip Morris U.S.A. Research Center, P.O. Box 26583, Richmond, Virginia 23261, U.S.A. tStored-Product and Household Insects Laboratot3', A R S , U.S.D.A.,

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Unieersity q f Wisconsin, Madison, Wisconsin 53706, U.S.A.

References Blum, M. S. 1970. The chemical basis of insect sociality. In: Chemicals Controlling Insect Behavior (Ed. by M. Beroza), pp. 61 94. New York: Academic Press. Faustini, D. L., Burkholder, W. E. & Laub, R. J. 1981. Sexually dimorphic setiferous sex patch in the male red flour beetle, Tribolium castaneum (Herbst) (Coleoptera:Tenebrionidae): site of aggregation pheromone production. J. Chem. Ecol., 7, 465480. Mondal, K.A.M.S.H. 1985. Response of T. castaneum larvae to aggregation pheromone and quinones produced by adult conspecifics. Int. Pest Control, 27, 6466. Peters, T. M. & Barbosa, P. 1977. Influence of population density on size, fecundity, and developmental rate of insects in culture. A. Rev. Entomol., 22, 431~,50. Prokopy, R. J. 1981. Epideictic pheromones influencing spacing patterns of phytophagous insects. In: Semiochemicals." Their Roh" in Pest Management (Ed. by D. A. Nordlund, R. J. Jones & W. J. Lewis), pp. 181 213. New York: Wiley Press. Sokoloff, A. 1974. The Biology of Tribolium with Special Emphasis on Genetic Aspects, pp. 198-255. Oxford: Clarendon Press. Sonenshine, D. E., Gainsburg, D. M. & Homsher, P. J. 1982. Quinone inhibition of sex pheromone activity in the ticks Dermacentor andersoni Stiles and D. variabilis (Say). J. Parasitol., 68, 921 929. Webb, J. L. 1966. Enzyme and Metabolic lnhibitors. Vol. H. New York: Academic Press. (Received 26 June 1986; reeised 14 July 1986," MS. number: AS-409)

Social Preferences by Pigtailed Macaques: Familiarity Versus Degree and Type of Kinship Behaving preferentially to close kin is central to the concept of inclusive fitness, i.e. maximizing the probability of propagating one's own genes (Hamilton 1964). Preferential behaviour toward kin is reported for species ranging from insects through primates (Holmes & Sherman 1983). Major evidence comes from studies showing that close kin maintain proximity with one another rather than with unrelated or distantly related individuals (Sherman & Holmes 1985). The strongest evidence concerns related individuals that have no postnatal familiarity but still exhibit mutual preferences (Rushton et al. 1984). Sherman & Holmes (1985) propose learning through rearing association, spatial distribution, or phenotypic matching as the proximate basis for kin recognition. According to the latter concept, an individual learns about its genotypic traits through observing aspects of its own phenotype or pheno-