Effects of sublethal doses of chlorfluazuron on insemination and number of inseminated sperm in the common cutworm, Spodoptera litura (F.) (Lepidoptera: Noctuidae)

Abstract

Sublethal doses (LD10: 1.00 ng larva -1 ; or LD30: 3.75 ng larva -1 ) of chlorfluazuron were applied topically to the cuticles of newly moulted fifth instars of the common cutworm, Spodoptera litura (F.) (Lepidoptera, Noctuidae). During mating, the treated males transferred spermatophores of a significantly lower weight into females. The weight of spermatophores transferred by LD30-treated males was significantly lower than the weight of spermatophores transferred by LD10-treated males, which was in turn significantly lower than the weight of spermatophores transferred by untreated males. The transfer of spermatophores was delayed by 5-15 min in LD10-and LD30-treated males. However, mating duration was not affected by chlorfluazuron treatment. The transfer of spermatozoa was also delayed by 5-10 min in LD10-and LD30-treated females. Polygynous male adults mated an average of ten times during their lifespan of 11-13 days when paired every day with a new virgin female of the same age. The number of matings per polygynous male was not affected by chlorfluazuron treatment, but the first mating was delayed by 1 day. The number of inseminated sperm found in the spermatophore averaged 10.3 (Ϯ 2.1) ¥ 10 5 over the lifespan of a male, in which the number of eupyrene sperm was 5.4 (Ϯ 1.1) ¥ 10 5 . The number of inseminated eupyrene sperm decreased by 66% and 88%, respectively, in LD10-and LD30-treated males. No significant reduction in the number of inseminated eupyrene sperm was observed when females were treated with LD10 or LD30 doses, nor was there a significant reduction when both sexes were treated with the LD10 or LD30 doses relative to treatment of males with the same doses. The ratio of inseminated eupyrene to apyrene sperm was not affected by chlorfluazuron treatment.

Biochemical Analyses of Action of Chlorfluazuron as Reproductive Inhibitor in Spodoptera litura

“…The reason was that DNA content is directly proportional to the number of sperm present in the testis. The number of sperm transferred to female during 1 st and 2 nd mating, in LD 10 -treated S. litura significantly reduced and in LD 30 -treated insects more significantly reduced (Perveen, 2008). Therefore, DNA content was also affected by sublethal doses (Table 3.5).…”

“…Effects of sublethal doses (LD 10 : 1.00 ng larva -1 ; LD 30 : 3.75 ng larva -1 ) of chlorfluazuron on biochemical were analysed to observe the causes of effects of chlorfluazuron on oÖgenesis and ovarian development (Perveen and Miyata, 2000;Perveen, 2009a); spermatogenesis and testicular development (Perveen, 2000b(Perveen, , 2009a; insemination (Perveen, 2008(Perveen, , 2009a, oviposition stimulating factors (Perveen, 2009b); and embryogenesis (Perveen, 2009c); and also ultimate effects on the fecundity, fertility and hatchability. In the present research, a significant decrease in ovarian protein content in chlorfluazurontreated females was observed (Table 3.1).…”

“…However, there were no significant differences observed between larval and pupal treatment in the reduction of these biological parameters (Perveen, 2009a). Effects of chlorfluazuron on ovarian development and oögenesis (Perveen and Miyata, 2000), testicular development and spermatogenesis (Perveen, 2000b), insemination and number of inseminated sperm (Perveen, 2008) and haemolymph-borne ovipositionstimulating factors (Perveen, 2009b) in S. litura had been reported. The effect of sublethal doses of chlorfluazuron on embryogenesis of S. litura has also been reported during the eight embryonic developmental stages (0-84 hours after oviposition) (Perveen, 2009c).…”

Effects of sublethal doses of chlorfluazuron on the testicular biochemical constituents of Spodoptera litura (Lepidoptera: Noctuidae)

“…Previous work (Perveen, 2000a) demonstrated that sublethal doses of chlorfluazuron (LD 10 and LD 30 ) applied topically to fifth instars of S. litura reduced the fecundity and fertility of the subsequent adult females and the hatchability of their eggs. Other effects of similar sublethal doses were decreases in the weight of ovaries, number of mature ova and size of basal oöcytes (Perveen and Miyata, 2000), decreased in the amount of ovarian biochemical constituents including protein, carbohydrates, lipid, nucleic acids and ecdysteroid titires (Perveen, submitted), delayed initiation of mating (Perveen, 2008) and reduced activity of oviposition stimulation factors (Perveen, 2009). Moreover, LD 10 and LD 30 treatment of males significantly (p < 0.01) reduced (65.8 and 88.6%) the number of inseminated eupyrene sperm (Perveen, 2008).…”

“…Other effects of similar sublethal doses were decreases in the weight of ovaries, number of mature ova and size of basal oöcytes (Perveen and Miyata, 2000), decreased in the amount of ovarian biochemical constituents including protein, carbohydrates, lipid, nucleic acids and ecdysteroid titires (Perveen, submitted), delayed initiation of mating (Perveen, 2008) and reduced activity of oviposition stimulation factors (Perveen, 2009). Moreover, LD 10 and LD 30 treatment of males significantly (p < 0.01) reduced (65.8 and 88.6%) the number of inseminated eupyrene sperm (Perveen, 2008). Subsequently, Perveen (2006) demonstrated that eggs laid by treated females were up to 66% smaller and more likely to be infertile than those laid by untreated females.…”