Estrogenic and anti-androgenic effects of the herbicide tebuthiuron in male Nile tilapia (Oreochromis niloticus)

Abstract

Tebuthiuron is a phenylurea herbicide widely used in agriculture that can reach the aquatic environments, possibly posing negative effects to the aquatic biota. Phenylurea herbicides, such as diuron, are known to cause estrogenic and anti-androgenic effects in fish, but no such effects were yet reported for tebuthiuron exposure. Thus, the aim of this study was to evaluate if tebuthiuron, at environmentally relevant concentrations (100 and 200ng/L) and after 25days of exposure have estrogenic and/or anti-androgenic effects on male of Nile tilapia (Oreochromis niloticus), through the evaluation of plasmatic testosterone (T) and estradiol (E) levels, brain aromatase (CYP19) levels (western-blot), and by evaluating the histology of the testicles. When compared to the control group, plasmatic T levels decreased about 76% in the animals exposed to 200ng/L of tebuthiuron, while E levels increased about 94%, which could be related to a significant increase (77%) in CYP19A1 levels, an enzyme that catalyzes the conversion of androgens into estrogens. Histological analyses of the testicles also demonstrated that tebuthiuron at both tested concentrations caused a decrease in the diameter of the seminiferous tubules and in the diameter of the lumen. Therefore, the gonadosomatic index (GSI) was reduced by 36% % in the animals exposed 200ng/L to tebuthiuron. Indeed, the relative frequency of spermatocytes and spermatids increased respectively 73% (200ng/L) and 61% (100ng/L) in the tebuthiuron exposed animals, possibly due to the impairment of sperm release into the lumen, that was decreased 93% (200ng/L) in the treated animals compared to the control. These results confirm that tebuthiuron causes estrogenic and anti-androgenic effects in Nile tilapias at environmentally relevant concentrations.

Contamination of fee-fishing ponds with agrochemicals used in sugarcane crops

“…Almeida et al [42] observed estrogenic and anti-androgenic effects with altered in spermatogenesis and in the size of the gonads on Oreochromis niloticus exposed to tebuthiuron in concentrations of approximately 1.5 times lower than the highest concentration detected in the searchers of this survey.…”

Reproductive cycle of the Amazonian planktivorous catfish Hypophthalmus marginatus (Siluriformes, Pimelodidae)

“…The frequencies of points on different structures were calculated (no. points × 100/total points) using the same method applied by Alvarenga and França (); Criscuolo‐Urbinati, Kuradomi, Urbinati, and Batlouni (); De Almeida, Pereira, Batlouni, Boscolo, and Almeida (); Pereira, Boscolo, Moreira, and Batlouni ().…”

“…The results of the volume density evaluation were used to define the ovarian maturation stage, following traditional methodology applied for describing the reproductive cycle of tropical migratory (Borella, Chehade, Costa, & Batlouni, ; Rizzo & Bazolli, ) and other fish (Grier, Neidig, & Quagio‐Grassioto, ; Mañanós, Duncan, & Mylonas, ). To determine reproductive classes, we used the data obtained by volume density following methodology applied with some adjustments for the species under study (De Almeida et al, ; Kuradomi, Foresti, & Batlouni, ; Lira, Kuradomi, Souza, Hainfellner, & Batlouni, ; Pereira et al, ). Briefly, ovaries predominantly occupied by PV and lacking VI were considered "resting/immature"; ovaries presenting PV, CA and VI (volume density <10%) were considered "in maturation"; ovaries presenting VI (volume density >20%) and lacking POF were considered "mature"; ovaries with the presence of POF and VI were considered "spawned"; and ovaries that presented AT (>10%) were defined as "atretic.…”

“…The results of the volume density evaluation were used to define the ovarian maturation stage, following traditional methodology applied for describing the reproductive cycle of tropical migratory (Borella, Chehade, Costa, & Batlouni, 2014;Rizzo & Bazolli, 2014) and other fish (Grier, Neidig, & Quagio-Grassioto, 2017;Mañanós, Duncan, & Mylonas, 2008). To determine reproductive classes, we used the data obtained by volume density following methodology applied with some adjustments for the species under study (De Almeida et al, 2018;Kuradomi, Foresti, & Batlouni, 2017;Lira, Kuradomi, Souza, Hainfellner, & Batlouni, 2018;Pereira et al, 2017).…”

Agrochemicals in freshwater systems and their potential as endocrine disrupting chemicals: A South African context

“…Fat samples were also collected from the fish and the following pesticides were quantified: DDT, DDE, DDD, endosulfan, dieldrin, endrin, and lindane. Environmentally relevant concentrations of herbicides have also been found to cause oestrogenic and anti-androgenic effects in tilapia species elsewhere, including Nile tilapias ( O. niloticus ) native to northern Africa ( De Almeida et al , 2018 ).…”