ST. LAWRENCE INFO

Chemical Contaminants Disrupt Reproductive Function in Male Fish in the St. Lawrence River

Research results published in 2004 reveal that estrogens present in the St. Lawrence River affect the reproductive systems of male spottail shiner (Notropis hudsonius). This member of the Cyprinidae family of minnows serves as prey for a large number of freshwater predatory fish.

Spottail shiner (Notropis hudsonius)

Earlier studies by St. Lawrence Centre (SLC) researchers had shown that endocrine disruptors, hormone-mimicking substances that enter the river in urban, industrial and agricultural effluents, acted on the sexual differentiation of molluscs. Recently, however, SLC scientists have also observed such disruptions in the male of a freshwater fish species – the spottail shiner.

Widespread Estrogen Contamination

Measurable concentrations of mRNA of hepatic vitellogenin, a protein usually secreted by females during egg formation, were observed in male and in immature specimens of spottail shiner. The production of this protein is stimulated by hormones such as estrogen and normally occurs only in females; exposure to estrogenic contaminants in the St. Lawrence River has had the effect of triggering the production of vitellogenin, even in male or immature specimens. Our results indicate that estrogen contamination is widespread in the river and extends over an area of almost 50 km, both upstream and downstream of the island of Montreal. Similar results were seen in the mussel Elliptio complanata exposed to surface waters of the St. Lawrence River. See Hormonal Disruptions in the Freshwater Mussels.

Spermatogenesis Disrupted

Spermatogenesis, the process of spermatozoa formation, appears disrupted in specimens of spottail shiner captured at sites where estrogen contamination is high.

Four phases of spermatogenesis are observed
in specimens of spottail shiner

Source: Aravindakshan et al. 2004a. A) Stage II: beginning of spermatogenesis, characterized by the formation of cysts containing spermatogonia (sg) and spermatocytes (sc); B) Stage III: cysts containing spermatogonia, spermatocytes and spermatids (sd); C) Stage IV: appearance of spermatozoids (sz); D) Stage V: phase of spermiation during which tubules fill up with spermatozoids (sz).

Source: Aravindakshan et al. 2004a. The results show that 45% of fish caught off the îles de la Paix (control site) present with mature developmental stages (stage 5), whereas not a single specimen captured at the îlet Vert or île Beauregard sites, located within the effluent dispersion plume of the City of Montreal, had reached this developmental stage at the time of their capture in June. It should be noted that these specimens had high concentrations of vitellogenin mRNA in their livers. Vitellogenin is a protein associated with the female reproductive system.

Moreover, the concentration of sperm (number of spermatozoids per given volume) and various parameters of motility were significantly lower in adult spottail shiners from îlet Vert compared to those from îles de la Paix (reference site). Testicular histological analyses revealed that more than one-third of male fish caught at the most estrogen-contaminated sites demonstrated intersexuality, a state in which ovarian follicles, normally characteristic of females, develop in the testicles.

These results indicate that there is major contamination by estrogenic contaminants in the St. Lawrence River and that it is associated with the deterioration of reproductive function in male fish.

What are the Consequences?

Such disruptions are likely to alter wildlife communities considerably, disturb the food chain and, ultimately, reduce the biodiversity of the St. Lawrence. The St. Lawrence Centre continues to work to enhance knowledge of the estrogenic effects of urban effluents on St. Lawrence wildlife and to identify the substances responsible for these effects.

Literature

Aravindakshan, J., V. Paquet, M. Gregory, J. Dufresne, M. Fournier, D.J. Marcogliese, and D.G. Cyr. 2004a. Consequences of xenoestrogen exposure on male reproductive function in spottail shiners (Notropis hudsonius). Toxicological Sciences 78: 156–165.

Aravindakshan, J., M. Gregory, D.J. Marcogliese, M. Fournier, and D.G. Cyr. 2004b. Consumption of xenoestrogen-contaminated fish during lactation alters adult male reproductive function. Toxicological Sciences 81(1): 179–189.

Related Links

St. Lawrence Info
Hormonal Disruptions in the Freshwater Mussels

Projects
Impacts of Urban Effluents on Fish Health

Ecotoxicology of Urban Effluents