Peptides 23 (2002) 1907–1914 Search for peptidic molecular markers in hemolymph of crowd-(gregarious) and isolated-reared (solitary) desert locusts, Schistocerca gregaria M.M. Rahman ∗,1 , L. Vanden Bosch, G. Baggerman, E. Clynen, K. Hens, B. Hoste, K. Meylaers, T. Vercammen, L. Schoofs, A. De Loof, M. Breuer Zoological Institute, Katholieke Universiteit Leuven, Naamsestraat 59, B-3000 Leuven, Belgium Received 12 April 2002; accepted 17 June 2002 Abstract An HPLC analysis of hemolymph extracts was undertaken to uncover differences between desert locusts, Schistocerca gregaria, reared under either crowded or isolated conditions. Some differences in the chromatographic pattern could be detected. One of the major peaks in the hemolymph of crowd-reared adults was found to be a minor one in isolated-reared individuals, whereas other peaks increased after solitarization. The differences became even more pronounced after several generations of isolated rearing. The dominant chromatographic peak in hemolymph extracts of the crowd-reared animals was identified as a novel peptide with a molecular mass of 6080 Da. Edman degradation in combination with enzymatic fragmentation and quadrupole-time of flight (Q-Tof) mass spectrometry revealed the full sequence: DNADEDTICVAADNKFYLYANSLKLYTCYNQLPKVYVVKPKSQCRSSLSDCPTS. This 54 aa-peptide is very abundant in hemolymph of crowd-reared adults. Its concentration in hemolymph amounts to 0.1 mM. To uncover the function, its effects were investigated in several bioassays, so far without positive results. One of the other peaks differentially expressed in the individuals of the two phases was identified as SGPI-2 (MW = 3794 Da), which is a serine protease inhibitor in locusts. © 2002 Elsevier Science Inc. All rights reserved. Keywords: Locusts; Schistocerca gregaria; Locust phases; Locust phase polymorphism; Locust phase transition; Insect neuropeptides; Hemolymph peptides 1. Introduction According to the phase theory suggested by Uvarov [17], the development of locusts may follow either a solitary or a gregarious pathway, with a range of intermediate forms. The solitary and gregarious locustsdifferin many fea- tures, collectively called phase characteristics, which show marked variations in morphology, coloration, reproduction, development, physiology, biochemistry, molecular biology, cytology, behavior and ecology [9,10,18,19]. The changes of the phase characteristics depend on environmental fac- tors and population density whose effects are mediated by the nervous and endocrine systems [4]. Many studies aiming at unraveling the control of phase transition have been undertaken in the course of the 20th ∗ Corresponding author. Tel.: +32-16-324260; fax: +32-16-323902. E-mailaddress: mazibur.rahman@bio.kuleuven.ac.be (M.M. Rahman). 1 Permanent address: Institute of Food and Radiation Biology (IFRB), Atomic Energy Research Establishment (AERE),GPO Box No.3787, Dhaka 1000, Bangladesh. century. Specialattention has been paid to the roles of adipokinetic hormones, juvenile hormones, ecdysteroids and brain neuropeptides (see review by Pener [9]). The relatively recent discovery that the neuropeptide [His 7 ]-corazonin is responsible for both the dark coloration of the cuticle [16] as wellas fora shiftin morphometrics towards the gre- garious phase (unpublished observations) elicits a renewed interest in the physiology of phase transition. However, it is notpossible to fully explain the control of phase transition solely on the basis of the action of the above-mentioned hormones. Eitherit is an interaction of each or some of these hormones, which would be exceed- ingly difficult to investigate, or some controlling agents are still missing. Therefore, further search for as yet overlooked molecular markers of phase transition is necessary. Lenz et al. [7] found some interesting differences in the concen- tration of several low molecular weight metabolites present in the hemolymph of crowd- and solitary-reared locusts. In addition, we recently discovered that the chromatographic profile of acidic methanolic hemolymph extracts revealed some differences betweendesertlocusts,rearedunder 0196-9781/02/$ – see front matter © 2002 Elsevier Science Inc. All rights reserved. PII: S 0 1 9 6 - 9 7 8 1 ( 0 2 ) 0 0 1 7 5 - 4