Endocrine Disruptors & Ecology

"Exposure to endocrine-disrupting chemicals in the environment has been associated with abnormal thyroid function in birds and fish; decreased fertility in birds, fish, shellfish, and mammals; decreased hatching success in fish, birds, and turtles; demasculinization and feminization of male fish, birds, and turtles; defeminization and masculinization of female fish, gastropods, and birds; and alteration of immune function in birds and mammals." (Colborn et al, 1993)

The release of both man-made and natural substances into the environment is increasingly affecting wildlife and humans and has been a growing concern over the last decade (Guillette et al 2001). Substantial evidence shows the effects of certain environmental chemicals on development and functioning of endocrine organs, cells, and tissues, in addition to the changes in reproductive activity, morphology and physiology in organisms (Guillette et al 2001). Guillette et al (2001), Jenssen (2006), and Colborn et al.(1993) are only a few of the scientists that study the effects of endocrine disrupting chemicals on wildlife. The lists and table below highlight their findings.

Hormones Affected by Endocrine Disrupting Chemicals in Wildlife

Thyroid hormones: they regulate metabolic processes and growth and differentiation of tissues.
Sex steroid hormones: they are essential for reproduction and influence sexual behavior.
Glucocorticosteroids: they are involved in a range of physiological processes including reproduction, behavior, adaptation to stress, and regulation of immune function.

Endocrine distruption can occur at several sites in the reproductive system: hypothalamo-pituitary function, gonadal hormone synthesis, hepatic biotransformation or serum binding can be altered. (Guillette et al. 2001)

Effects of Endocrine Disrupting Chemicals in Wildlife

Developmental alterations
Alterations in sex determination
Disruption of organ differentiation
Decrease reproductive success

Endocrine Disrupting Chemical Effects on Particular Species

Alteration	Species Effected
Interference with steroid hormones	Mammals, reptiles, amphibians, and fish
Sexual dimorphism	Rodents, fish, reptiles, birds, marine mammals
Thyroid enlargement Precocious sexual maturation Poor egg survival Low egg thyroid hormone content	Salmon (in the Great Lakes)
Behaviorial changes Reproductive loss Early mortality in offspring	Bird species (in the Great Lakes that feed on Salmon)
Decline in adult yearly survival rate Asymmetrical wing development Altered parental behaviour	Gulls
Decreased thyroid hormone levels	Seals, polar bears
Negative effects on plasma progesterone levels and plasma cortisone levels.	Polar bears

Image Sources
Bird: www.newmanveterinary.com
Shellfish:www.thegutsygourmet.net
Hatching turtle: www.dnr.state.wi.us
Gastropod:www.dnr.sc.gov
Alligator: www.sciencenetlinks.com