Sep 19, 1995 - methyl parathion (0, O-dimethyl O- (4-nitrophenyl) phosphoro- thioate), an extensively used organophosphate pesticide, in graded sublethal ...
Arch. Environ. Contam. Toxicol. 30, 384-389 (1996)
Environmental Contamination a n d Toxicology © 1996 Springer.Verlag New York Inc,
Influence of Methyl Parathion on Gametogenic and Acetylcholinesterase Activity in the Testis of Whitethroated Munia (Lonchura malabarica) S. K. Maitra, R. Sarkar Reproductive and Endocrine PhysiologyLaboratory, Department of Zoology,University of Burdwan, Golapbag, Burdwan 713 104, India Received: 3 July 1995/Revised: 19 September 1995
Abstract. Adult male whitethroated munias, Lonchura malabarica (Aves; Passeriformes), were orally administered with methyl parathion (0, O-dimethyl O- (4-nitrophenyl) phosphorothioate), an extensively used organophosphate pesticide, in graded sublethal dose (5 p~g-, or 10 txg-, or 20 txg/100 g body wt/day) for variable durations (1-, 5-, or 10 day/s) during their peak reproductive activities in an annual gonadal cycle. No subtle changes in the feeding behavior, mobility, and body weight were noted between the control and different groups of pesticide-fed birds. As a result of the treatment, the paired testicular weight became reduced significantly only after 10 days at 10 Ixg- and 20 Ixg dose levels, but significant decrease in the number of tubules containing healthy germ cells occurred even after single administration of methyl parathion (MP) at the lowest dose (5 ixg/100 g). With the increase in dose and progress of treatment, the number of tubules with healthy germ cells became gradually decreased. The activity of acetylcholinesterase (ACHE) in both the brain and testes of MP-treated birds was inhibited in a dose and duration dependent manner. A significant negative correlation was observed between the number of tubules containing degenerated germ cells in the testis and the AChE activity in both the brain and testes of MP-administered birds. However, no remarkable changes in the cytomorphological features, including the nuclear diameter of Leydig cells, were noted in any testis of the pesticide-treated munias. The results of the present investigation suggest that methyl parathion ingestion is harmful to male gametogenic functions in the studied passeriform bird, and the given pesticide may exert its antigonadal effect by impairing cholinergic functions of the brain and/or testes.
The use of organophosphate pesticides (OP) in agricultural fields has replaced more persistent chlorinated hydrocarbon compounds (Fowler and Mahan 1980). The choice of OPs is
Correspondence to: S. K. Maitra
based on their properties of low bioaccumulation and higher rate of biodegradation. However, several field studies revealed that OPs in higher concentrations may cause the deaths of nontarget wildlife, including birds (Hills et al. 1975; Grue and Shipley 1984; Stone and Gradoni 1985). Reports are also available to show that the OPs in sublethal concentrations induce several physiological disorders in different mammals and birds (Grue et al. 1983; Rattner et al. 1984; Sarkar and Maitra 1990; Anam and Maitra 1995). Nevertheless, the study of reproductive consequences following ingestion of different OPs has not received adequate attention. The effects of OPs on male reproductive organs were studied in laboratory rodents (Krause et al. 1976; Hanna and Kerr 1981; Ray et al. 1987; Bhatnagar and Soni 1990) and also in domestic or semidomestic birds (Rattner et al. 1982; Somkuti et al. 1987). The majority of wild birds are seasonal breeders and on many occasions, the season of their attainment of annual sexual maturity coincides with the time of application of OPs in the agricultural fields (Rattner et al. 1982), but very little is known about the testicular responsiveness to the exposure of OPs in free-living birds. A preliminary study on a wild psittacine bird (Psittacula krameri) has shown that oral administration of phosphamidon (Sarkar and Maitra 1989), quinalphos (Maitra and Sarkar 1991), or methyl parathion (Maitra and Sarkar 1993) may induce testicular dysfunction. The present study examines dose and duration dependent influence of the ingestion of methyl parathion on the gametogenic and cholinergic functions of the testes in a wild passerine bird, the whitethroated munia (Lonchura malabarica). The activity of acetylcholinesterase (ACHE) in brain tissues was estimated to address the question of whether there is any correlation between the responsiveness of the testes and the brain to the given pesticide in concerned birds.
Materials and M e t h o d s
Adult healthy male whitethroated munias (Lonchura malabarica; Ayes; Passeriformes; Ploceidae) were collected from the natural population in and around Burdwan, India (Lat, 23° 14'N, Long. 87° 5I'E), with the help of a professional bird catcher during the months of October and November, when the species attains seasonal gonadal maturation.