Modulation of genotoxicity and endocrine disruptive effects of malathion by dietary honeybee pollen and propolis in Nile tilapia (Oreochromis niloticus)

Abstract

The present study aimed at verifying the usefulness of dietary 2.5% bee-pollen (BP) or propolis (PROP) to overcome the genotoxic and endocrine disruptive effects of malathion polluted water in Oreochromis niloticus (O. niloticus). The acute toxicity test was conducted in O. niloticus in various concentrations (0-8 ppm); mortality rate was assessed daily for 96 h. The 96 h-LC50 was 5 ppm and therefore 1/5 of the median lethal concentration (1 ppm) was used for chronic toxicity assessment. In experiment (1), fish (n = 8/group) were kept on a diet (BP/PROP or without additive (control)) and exposed daily to malathion in water at concentration of 5 ppm for 96 h "acute toxicity experiment". Protective efficiency against the malathion was verified through chromosomal aberrations (CA), micronucleus (MN) and DNA-fragmentation assessment. Survival rate in control, BP and PROP groups was 37.5%, 50.0% and 100.0%, respectively. Fish in BP and PROP groups showed a significant (P < 0.05) reduction in the frequency of CA (57.14% and 40.66%), MN (53.13% and 40.63%) and DNA-fragmentation (53.08% and 30.00%). In experiment (2), fish (10 males and 5 females/group) were kept on a diet with/without BP for 21 days before malathion-exposure in water at concentration of 0 ppm (control) or 1 ppm (Exposed) for further 10 days "chronic toxicity experiment". BP significantly (P < 0.05) reduced CA (86.33%), MN (82.22%) and DNA-fragmentation (93.11%), prolonged the sperm motility when exposed to 0.01 ppm of pollutant in vitro and increased the estradiol level in females comparing to control. In conclusion, BP can be used as a feed additive for fish prone to be raised in integrated fish farms or cage culture due to its potency to chemo-protect against genotoxicity and sperm-teratogenicity persuaded by malathion-exposure.

Keywords: Genotoxicity; Malathion; Nile tilapia; Pollen; Propolis.

Fig. 1

Semen characteristics in male Nile tilapia (O. niloticus) after exposure to 1 mg/l (1 ppm) of malathion for 10 days. T1 (□) was negative control (unexposed, fed basal diet). T3 ($■$) was positive control (exposed, fed basal diet). T4 ($■$) and T5 ($■$) were pollen fed, but the later was returned to diet during toxin treatment. Values (mean ± SE; n = 5 per group) with different letters were significantly different at P < 0.05.

Fig. 2

Effect of in vitro malathion exposure on motility rate (A–C) and duration (D–F) of male Nile tilapia (O. niloticus) semen fed control (○) or pollen (•) diet. Seminal fluid (2 μl) was diluted in distilled water (498 μl) contained malathion of selected concentration (1.00, 0.10 and 0.01 ppm). Initial motility (0 s.) and motility after 20 s. of exposure as well as the duration of motility (sec.) at 0, 30 and 60 s. were scored. Motility score was assessed as a percentage of the total number of spermatozoa following 10 s period of activation. Data were expressed as mean ± SE (n = 5) with different letters at the same time point were significantly different at P < 0.05 as compared with control.

Fig. 3

Changes in serum gonadotrophic and steroid hormones in male and female Nile tilapia (O. niloticus) fed basal diet (T1, T3), pollen (T4) or retrieved to basal diet after pre-feeding with pollen (T5). Fish in T3 ($■$), T4 ($■$) and T5 ($■$) were exposed to 1 mg/l (1 ppm) of malathion for 10 days while T1 (□) was left as non-exposed control. Data were expressed as mean ± SE (n = 5 per group) with different letters were significantly different at P < 0.05.