Journal of the American Mosquito Control Association, 16(l):36_37.2OOO Copyright O 2000 by the American Mosquito Control Association, Inc.

ISOBUTYRIC ACID FROM THE BRINDLEY'S GLANDS OF LECTICUIARIA

DAVID S. SEIGLER' e,No RICHARD L. LAMPMAN,

ABSTRACT. The contents of the Brindley's gland of Triatoma lecticularia (Stil) (Heteroptera: : ) have been identified by gas chromatography-mass spectrometry as isobutyric acid. This compound is found in similar secretions from certain other members of the Triatominae, and is suggested to play a role as a defensive pheromone and for intraspecies communication.

KEY WORDS Triatoma lecticularia, Triatominae, Reduviidae, Brindley's glands, isobutyric acid

INTRODUCTION the needle of a lo-pl syringe and the liberated liq- uid was taken up and injected directly onto a cou- Almost all Heteroptera are known to possess pled Hewlett Packard (HP) 5995 gas chromatograph- scent glands (Carayon 1971, Staddon 1986). The mass spectrometer (GC-MS) Qlewlett Packard, Roll- most prominent scent glands in members of the or- ing Meadows, IL) (electron impact, 70 eV) interfaced der of true bugs include lateral metathoracic glands with an HP 599704 GC-MS computer system with and ventral abdominal glands (especially in adults) a National Bureau of Standards mass spectral li- and dorsal abdominal glands (particularly in im- brary containing spectra of more than 38,0O0 com- matures, but also active in some adults) that pro- pounds. The column was a fused silica capillary duce a wide variety of compounds with allomonal column (10 m X 0.3 mm) with a cross-linked meth- and pheromonal properties (Blum 1981, Pasteels et yl silicone phase (Hewlett Packard) and helium car- al. 1983, Staddon 1986, Aldrich 1988). Individuals rier gas. The temperature program was 35'C to of Triatoma lecticularia (Stel), as well as other tria- 160'C at l0"C/min with a 2-min hold at the starting tomine bugs, produce a pronounced rancid odor temperature. The injection port, transfer line, and when disturbed, or when reared in (Zim- colonies ion source were set at 23O"C, ZOO"C, and 22O"C, mennan 1948; KAlin and Barrett 1975; Ryckman, respectively. Authentic isobutyric acid was pur- personal communication). The most of conspicuous chased from Aldrich Chemical Co. (Milwaukee, the scent glands in many Reduviidae (assassin WI) and injected under the same conditions on the are Brindley's glands (Brindley 1930, bugs) Cara- GC-MS. yon et al. 1958, Kiilin and Barrett 1975, Schofield and Upton 1978, Staddon 1979). Because of the distinctive odor produced by both individuals and RESULTS AND DISCUSSION colonies of T. lecticularia, a species widespread in The mass spectrum of the only low molecular Texas and the southeastern USA. and the fact that weight peak observed in gas chromatographic sep- this species sometimes harbors Trypanosoma cruzii arations of the gland contents had major ion peaks (Chagas) (Usinger 1944, Lent and Wygodzinsky at the mass-to-charge rutios Qnle) 88, 73, 57, 55, 1979), the trypanosome responsible for Chagas dis- 45, 43, 42, 41, and 39, which are consistent with ease, we investigated the Brindley's gland secretion those of isobutyric acid. A standard of this com- of this species. pound exhibited the same retention time, peak shape, and fragmentation pattern. Based on the total MATERIALS AND METHODS ion current chromatogram, isobutyric acid compris- es more than 99Vo of the volatile components of the Specimens of T. lecticularia were collected in Brindley's glands. wood rat (Neotoma spp.) nests, 33.5 km northeast Isobutyric acid seems to be the typical secretion of Alpine, Brewster County, TX, on the Strauss identified from the Brindley's glands of Tfiatominae Ranch, January 14, 1987, by D. S. Seigler, J. Rich- (Schofield and Upton 1978). In addition to T. lec- erson, and J. Ztbia. Adults and various nymphal ticularia, this compound also has been isolated stages were maintained in cages by feeding once from the Brindley's glands of Rhodnius prolixus weekly on mice until study was feasible. (Stil) (Pattenden and Staddon 1972, Games et al. Brindley's glands were removed from adult in- 1974), Panstrongylus megistus (Burmeister), Tri- sects by dissection in O.9% saline solution. The atoma phyllosoma (Burmeister) (Games et al. glands were ruptured under a dissecting scope with 1974), T. infestans (Klug), T. maculata (Erichson), T. brasiliensi,s Neiva, ^nd T. vitticeps (Stel) (Scho- field 1979). Isobutyric acid previously also has rDepartment of Plant Biology, University of Illinois, been isolated from the secretions of larvae of Pap- 505 S Goodwin, Urbana. IL 61801. 2 Medical Entomology Laboratory, Center for Econom- ilio machaon, the European swallowtail butterfly ic Entomology, Illinois Natural History Survey, 6O7 E (Eisner and Meinwald 1965, Seligman and Doy Peabody Drive, Champaign, IL 61821. 1973). as well as other swallowtail butterflies (Eis-

36 Mancn 20O0 Tn uro ul, LECTI c ur^A.RIA JI ner et al. 1970), carabid beetles (Schildknecht et al. Eisner T, Meinwald YC. 1965. Defensive secretion of a 1968), and male noctuid moths (Aplin and Birch caterpillar (Papilio). Science l5O:17 33-17 35. D[ Y{zquezL,P€rez 1970). Both butyric and isobutyric acids are present Eisner t Pliske TE, Ikeda M, Owen H, Franclemont JG, Meinwald J. 1970. Defense mech- in the metathoracic scent of broadheaded bugs (Al- anisms of . XXVIL Osmeterial secretions of (Aldrich ydidae) 1988). papilionid caterpillars (Baronia, Papilio, Eurytides). This unpleasant-smelling substance probably Ann Entomol Soc Am 63:914-915. serves as a predator repellent, but also has intra- Games DE. Schofield CJ. Staddon BW. 1974. The secre- specific function. Isobutyric acid is liberated by ag- tion of Brindley's scent glands in Tfiatominae. Ann En- itated live adults of Triatoma infestans, as well as tomol Soc Arn 67:82O. other species (Lopez et al. 1995). When tested in Kiilin M, Barrett FM. 1975. Observations on the anatomy, an olfactometer, bugs avoided the presence of iso- histology, release site, and function of Brindley's glands butyric acid with a response that involved both kli- in the blood-sucking bug, Rhodnius prolixus (Heterop- Reduviidae). Entomol Soc Am 68:.126-134. notactic and orthokinetic components (Ward 1981). tera: Ann Lent H, Wygodzinsky P. 1979. Revision of the Tiiatomi- However, the avoidance response showed a marked nae (, Reduviidae), and their significance as dimunition at high concentrations, suggesting sat- vectors of Chagas disease. Bull Am Mus Nat Hist 163:. uration of receptors. Whether isobutyric acid has 123-520. defensive or pheromonal activity is presently under Lopez LC, Morgan ED, Ondarza RN. 1995. Brindley's investigation. The involvement of exocrine secre- gland exocrine products of Triatoma infestans. Med Vet tions in triatomine behavior could play a role in the Entomol 9:4O3-4O6. biological control of this important group of in- Pasteels JM, Gr6goire J, Rowell-Rahier M. 1983. The sects. chemical ecology of defense in arthropods. Annu Rev Entomol 28:263-289. Pattenden G, Staddon BW. 1972. Identification of iso-bu- ACKNO\vLEDGMENTS tyric acid in secretions from Brindley's scent glands in Rhodnius prolixus (Heteroptera: Reduviidae). Ann En- This research was supported by funds from a Na- tomol Soc Am 65:124O-1241. tional Institutes of Health Biomedical Research Schildknecht H, Winkler H, Maschwitz U. 1968. Verglei- Support Grant (NIH-RR-7030) and a grant from the chend chemische Untersuchungen der Inhaltsstoffe der National Science Foundation (NSF PCM 83-12778) Pygidialwehrblasen von Carabiden. Z Naturforsch 236: for purchase of a GC-MS instrument. We would 637-644. like to thank Jim Richerson, Department of Biolo- Schofield CJ. 1979. Demonstration of isobutyric acid in some triatomine bugs. Acta Trop 36:lO3-1O5. gy, Sul Ross State University, Alpine, TX, for as- Schofield CJ, Upton CP 1978. Brindley's scent-glandsand sistance in collecting specimens of T. lecticularia. the metasternal scent-glands of Panstrongylus megistus (Hemiptera, Reduviidae, Tiriatominae). Rev Bras Biol REFERENCES CITED 38:665-678. Seligman IM, Doy FA. 1973. Biosynthesis of defensive Aldrich JR. 1988. Chemical ecology of the Heteroptera. secretions in Papilio aegeus. Biochem 3;205- Annu Rev Entomol33:2ll-238. 215. Aplin Rl Birch MC. 1970.Identification of odorouscom- Staddon BW. 1979. The scent glands of Heteroptera. Ady pounds from male Lepidoptera. Experientia 26..1193- Insect Physiol 14:351-477. 1t94. Staddon BW. 1986. Biology of scent glands in the He- Blum MS. 1981. Chemical defensesof arthropods Neut miptera-Heteroptera. Ann Soc Entomol Fr (N S) 22: York: Academic Press. 183-190. Brindley MDH. 1930. On the metasternalscent-glands of Usinger RL. 1944. The Triatominae of North and Central certain Heteroptera.Trans Entomol SocLond 78:199- America and the West Indies and their public health 208. significance USPHS Public Health Bulletin 288. Wash- Carayon J. 1971. Notes et documentssur I'appareil odor- ington, DC: U.S. Government Printing Office. ant metathoraciquedes hemiptbres.Ann Soc Ent Fr 7: Ward JP 198 l. A comparison of the behavioural responses 737-770. of the haematophagous brug, Triatoma infestans, to syn- Carayon J, Usinger RL, Wygodzinsky P 1958. Notes on thetic homologues of two naturally occuning chemicals the higher classificationof the Reduviidae,with the de- (n- and iso-butyric acid). Physiol Entomol 6:325-329. scription of a new tribe of the Pymatinae.Rev Zool Bot Zimmerman EC. 1948. of Hawaii Yolume 3 Het- Afr 57:256-281. eroptera Honolulu: Univ Hawaii Press.