Naznin Nahar

Melatonin is a conserved indolamine implicated in circadian and developmental timing, but its role in social-insect task allocation is unclear. Here, we show that melatonergic signaling modulates the nurse → forager transition in the honey bee (Apis mellifera). A single hemocoelic dose of melatonin (100 ng) markedly reduced hive retention and advanced the age at first waggle dance by ≈9 days (median 11.8 vs. 20.9 days; common-language effect size = 0.94). Complementary manipulations—pharmacological antagonism with luzindole and RNA interference (RNAi)-mediated knockdown of a candidate melatonin receptor (AmMTR/AmMT2; transcript reduction ≈65–79% at 24–72 h)—produced reciprocal suppression of foraging, indicating pathway dependence. Transcriptional profiling revealed a forager-age peak in the arylalkylamine N-acetyltransferase ortholog AmNAT2 (≈10-fold increase near day 23), while AmNAT1 remained unchanged; melatonin treatment was associated with a trend toward increased Amα-glucosidase expression. Computational analyses classify AmMTR as a class-A GPCR and identify plausible melatonin-compatible pockets; promoter scans reveal high-confidence circadian motif matches upstream of AmMTR. These in silico results are presented as hypothesis-generating. Together, the behavioral, molecular, pharmacological and computational lines of evidence support melatonin as a circadian-informed modulatory signal that helps align neuroendocrine and metabolic states with the timing of extranidal behavior. Confirmation via receptor functional assays and broader colony replication will be important.

Mustard is one of the most important oilseed crops in Bangladesh. However, its production is severely constrained by aphid infestation. Farmers usually spray conventional insecticides to control aphids that negatively affect beneficial insects and environment. Thus, alternatives to conventional insecticides are required. We tested three biorational insecticides (Nimbicidine @ 1ml/L, Spinosad: Libsen 45SC @ 0.5 ml/L and Lufenuron: Hayron 5EC @ 0.5ml/L of water) against aphid infestation and assessed their effect on ladybird beetle and honey bee and compared these effects with two conventional insecticides (Diazinon: Sabion 60EC @ 2ml/L and Cypermethrin: Cypraplus 10EC @ 1ml/L of water) and with an untreated control. The study was conducted in a randomized complete block design with each treatment replicated thrice in the field of Department of Entomology, Bangladesh Agricultural University. Number of infested plants per plot, aphid per plant and per pod, number of ladybird beetle and honey bee per plot was counted and yield per plot was calculated. All tested insecticides reduced aphid infestation compared to untreated control indicating all of them were effective against aphid. However, Lufenuron and Nimbicidine was most effective to reduce plant infestation and number of aphids per plant and pod. Spinosad and Sabion were found fairly effective whereas Cypraplus was found to be least effective. Lufenuron and Nimbicidine did not reduce the number of ladybird beetle and honey bee visit per plot, however, Spinosad and conventional insecticides reduced their number. Lufenuron treated plots provided highest yield (1.35 t/ha) followed by Nimbicidine (1.15 t/ha), Spinosad (1.10 t/ha) and Sabion (1.00 t/ha) whereas Cypraplus treated plots provided lowest yield (0.9 t/ha). In terms of reducing aphid population thus plant infestation and increasing yield, all biorational insecticides performed better than conventional insecticides, however, concerning effect on ladybirds and honey bees, only Lufenuron and Nimbicidine can be recommended to farmers. J Bangladesh Agril Univ 22(3): 335-341, 2024