Rev. Biol. Trop., 47(4): 101 5-1020, 1999 www.ucr.ac.cr www.ots.ae.er www.ots.duke.edu Pharmacological properties of the repellent secretion of Zonocerus variegatus (Orthoptera: Prygomorphidae) A. B *Idowu and O. A Idowu Department of Biological Scienees, University of Agriculture, Abeokuta, Nigeria. * Corresponding author Received 10- IX-1998. Corrected 23-II1-1999 Accepted 16-IV-l999. Abstrae!: The odours of the whole body and the secretion of Zonocerus variegatus were easily recognised and perceived by human volunteers. However, the secretion odour is not related to the odour of the food plant con­ sumed by the grasshopper. The repellency of Z. variegalus becomes more pronounced in the 6th. and adult instars whose gland lumens contain an appreciable volume of secretíon. The seeretion odour is so strong that even dilulion does no! affee! its repulsiveness to humans. The secretion had pharmacological properties: it indueed contraction in rat (Rattus rattus)stomach smooth musc1e preparations and guinea pig (Cavia porcellus) ileum, and induced oedema formation in the rat hind paw. The secretion was not lethal to the animals used in this study, effects were temporary and reeovery oecurs after a short time. Key words: Z.variegatus, odour, seeretions, vertebrate, invertebrate, aetions. INTRODUCTION ed in their death. Thesecretion of P. bufonis con­ taíns histanUne which causes the cOiitfaction of When molested, both sexes and an instarsof the smooth muscle of the guinea pig ileum (von the varíegated grasshopper, Zonocerus variega­ Euw et al 1967). The effects of the secretion of Z tus (L.) expel an odorous, milky secretions from variegatus on organisms under laboratory condi­ a gland opening on the dorsal intersegmental tions has not been reported, and there is no data membranebetween thefirst and second abdomi­ on the perception of the secretion's odour by nal tergites (Idowu 1995). Thesecretion contaíns human beings. AH reports on the repellent gland proteins, amino acids, glucose, alkaloids and studied merelystate that the odour is repulsi ve or ions (Idowu & Modder 1998). The penetrating unpleasant to human beings. and unpleasant odour of the secretion caused the grasshopper to be avoided by vertebrate and invertebrate predators (Idowu 1997). MATERIALS AND METHODS Injections of secretions of the grasshopper, Poecilocerus bufonis (Fishelson 1960) and P. Perception oC Odour by human beings hieroglyphics (Abushama 1970) into mice result- For this experiment, human volunteers were 1016 REVISTA DE BIOLOGÍA TROPICAL used. Their perceptions of the odour was by dropping the secretion on the body of ants, recorded as one of the follows: termites, mouth parts of the praying mantids i) Very Strong: The volunteer could perceive and the eyes and skin of mice and rats. The the odour immediately the tube containing response of the animals was recorded and the test sample was presented. compared with control animals. subjected to ii) Strong: when it takes about 5 - 15 seconds the same treatments with distilled water. for the odour to be recognised. iii) Weak: when it takes about 20 - 25 seconds Effects on tbe bind paw of rats (Rattus rat­ for the odour to be perceived. tus): Adult rats (sprague dawley) weighing iv) No effect: The volunteer did not perceive between 150g and 200g were selected divided the odour. into 4 groups based on the treatment below. They were fasted for 12-16 hours before the The intensity of the odour was alloted 3, 2, 1 treatment. The circumference of the hind paw and O scores respectively. The sets of experi­ was measured before and after the experiment. ments performed are: Each paw was measured three times and the Insect Body Odour:- 10 insects of different mean size was obtained. developmental stages were placed separately in The hind paw of the rats in the differentgroups different stoppered conical flask covered with were infected separately with the following: foil papero The flasks were numbered 1-7 to correspond to the number of Zonocerusinstars. a) 0.lmm3 of al% (VN) suspension of car­ The flasks were thoroughly shaken before pre­ rageenin in 0.9% saline solution (a sus­ sentation for odour recognition by the human pension that is known to induce inflam­ volunteers. The order of presentation of flasks mation of the rat paw.) was change from one volunteer to the other. A b) O.lmm3 of the repellent secretion. time lag of 30 minutes was allowed between c) 0.lmm3 of the mixture of carragaenin and presentation of samples. the secretion. Secretion Odour:- Another set of 68 volunteers d) 0.lmm3 of distilled water. chosen randomly was presented with sample bottle containing the pure repellent secretion The effect of the injected fluids on the hind for odour perception. Distilled water was used paw of the rats was observed by measuring its as the control. Effect of dilution on the recog­ circumference limb three hours, 6 , 12 and 24 nition of the secretion odour was also carried hours after injections. out. Undiluted and serial dilutions (0.8, 0.6, 0.5, 0.4, 0.3, 0.2 and 0. 1) of the secretion were Stimulatory action on smooth muscle: Strips presented to another set of volunteers. The vol­ of smooth muscles of guinea pig ileum (Cavia unteers were also asked to compare the odour porcellus), rat stomach and rat colon were emanating from the botde containing the undi­ used. The rats and guinea pig were killed by a luted secretion with that of the body odour of blow on the head dissected for the parts were living adult Z. variegatus. A time interval of 30 placed in dishes containing Tyrode's solution. minutes was allowed between presentation of The mesentric membranes were trimmed off samples. The human volunteers used were along the intestine and stomach parts to free between the age of 20-30 years. the muscles. Tissue threads were attached at each end by inserting a needle through the Effects 01 the Secretion upon animals: This muscle wall. One end of the thread was tied to effectwas tested on different animals by exter­ a fixed pin in the moist chamber and the other nal application and by injection. Different to a lever which has a fine writing point. The dosages were injected subcutaneously into effect of the secretion on the smooth muscles mice and rats. External application was done strips was recorded using a Kymograph and a .'::,< . " :' ;;?,{ ';;,;.:��;{ . /:.,,;;i�'�'< :, ',""<", j,; ... ) ;. )" ;, ',> ·ttRl� ',' , ) smoked drum, with a¿etylcholine as stanClard. .... l\lt��orw: ih t � lt 1 . yvlij�hJghes�t,a�flowe�t � The eX ent �. , . P7rim w� �perfonned'�t 3'?°Ci� " levFt'ofdilJitiplh . � . .',) i./it�Tyrode's·solUtion thto�gh which(�ii-, �'aSi . ,1li�¡�S�Iisp'\)f91e)�(li�te�rSs�9�9�that ' �.i " dose�, �n.· . ':'¡i P�SS�':: e�� ��C���.�lve th7;.li��º4e }[,qr!egat¡lsP!�t,lC�Sln9dof w.ruG�\�J�w .., ...• :s�' solution. w washed. ' .. off :and the muscle fue 1st, 2nd, 3td �d'4thlnstars. lntel'nlediate.In " aU9wed to relaxfo� 4�� min�tes. .. ' .' theSth �dhlgh.in·the6tÍl amIth�i� dult in�hu-s. �� - -� - . ���ReSu1t.obtained,:sho;w�(Ltha��dPlioa�c-7-_� . .. the,b o�Yocl0� óf the 6tll. i��•• iJltb.iMwt by .' , human voJl,lÓte��was no! sÍgruficantIy di1'fcrent' (t"'test, .P>b.OO$�;.�bservatión during the study . PerceRtion ofili�odourof the boc,íy-and also shoW�:mat'�ople in lkare,Owo andOka .i,· the. secretion of Z. vqriegatZf,s by Quman yol;. all in QI1�9;isfáte.of Nigeria wherethe insect unteers. ,:;iiíf.¡' studie�. i$i:)l�� as a·food iteQl (TqHle' 1). They,. There w� instatlt.recognitjon of thefu\p�t' rec9�;Wli fIi�·fasrthat \ �ultz,i.Vo/:fe$dtU$;,l1as .. of the rep�llehrseH��op '¡�y the humáU v�iúp.� J an od,,-urw�h:according to their:>d��tripti�n, is teers uponp¡;es�n�op li.S strong and rep�l� bad,: pungen�'and repulsive. Hqwevér, fooked , . ,;sive. The volunteers wer�.aP1e to perceive the insect donotproduces such OO'our (Tap1e}). Th�,r .. .... '.' 'bdour ofthe,secretion evén when diluted. The volunteer recorded l;h�perc�ptiQ� of the' OAOUf.,;, .�í of of fue whole . gtas ho f>erls 'rep�ll�n1::; ,: pel'cepti�n . tbe: uri4j� , � � anp Q.e " . '.' theQ4Jqrsflo��dd�a� .. "�;1,;�� ,'j" i.( ' J};�;;[)f�¡f 1018 REVISTA DE BIOLOGÍA TROPICAL The subeutaneous injeetion of the seere­ and 0.5mm3 of the seeretion had no effeet on tion into the body of miee (M.musculus)and the rats, however, the injeetion of the same rats (Rattus rattus) resulted only in paralysis. amount of seeretion into miee eaused paralysis Paralysis was manifested as the inability of the (Table 2).The reeovery time was direetly pro­ animals to move their límbs after they were portional to the volume of seeretion injeeted injeeted. The subeutaneous injeetion of 0.1 into the miee and rats (Table 2). TABLE2 Effect of infected repelle/JI secretion of adalt Z. variegatus on rat, Spraque dawley and albÍlIO mice, Mus muscalus Volume of secretion Rats (n=5) Effect Mean recovery time nfection (mm3) (mins+-S.E) 0.1 No effect 0.5 No effect 1 ParaJysis 7 +- 1.07 3 ParaJysis 19 +- 1.40 5 ParaJysis 36 +- 1.59 Mice (n-5) 0.1 ParaJysis 12 +- 1.26 0.5 ParaJysis 17 +- 1.14 l ParaJysis 36 +- 1.40 3 ParaJysis 50 +- 2.14 5 ParaJysis 99 +- 3.28 ParaJysis - inability to move Iimb Recovery time - Time required for resumption of limb movements. The experimentalrats and mice used weighted between 1 00-120g and 35-50g respectively. Effect on the hind paw of rat: The extent of eompared to that elicíted by different dílution's the oedema produeed in the hind paw of rats of the seeretion.