Avian endocrine responses to environmental pollutants

Abstract

Many environmental contaminants are hazardous to populations of wild birds. Chlorinated hydrocarbon pesticides and industrial pollutants are thought to be responsible for population declines of several species of predatory birds through eggshell thinning. Studies have demonstrated that these contaminants have estrogenic potency and may affect the functioning of the gonadal and thyroidal endocrine subsystems. Petroleum crude oil exerts toxicity externally, by oiling of plumage, and internally, by way of ingestion of oil while feeding or preening. Extensive ultrastructural damage to the inner zone of the adrenal, diminished adrenal responsiveness to adrenocorticotrophic hormone, and reduced corticosterone secretion rate suggest that low levels of plasma corticosterone reflect a direct effect of petroleum on the adrenal gland. Suppressive effects of oil on the ovary and decreases in circulating prolactin have been associated with impaired reproductive function. Large-scale field studies of free-living seabirds have confirmed some of the inhibitory effects of oil on reproduction that have been observed in laboratory studies. Organophosphorus insecticides, representing the most widely used class of pesticides in North America, have been shown to impair reproductive function, possibly by altering secretion of luteinizing hormone and progesterone. Relevant areas of future research on the effects of contaminants on avian endocrine function are discussed.

Several environmental oestrogens are also anti-androgens

“…linked to effects such as a reduction in fertility, reduced hatch rate in fish and bird eggs, as well as alterations in hormone levels, and disrupted adult mating behaviour, all of which could have serious implications for wildlife and human population dynamics (Fry & Toone 1981, Rattner et al 1984, Carlsen et al 1992, Purdom et al 1994, Guillette 1995. Furthermore, numerous morphological effects have been noted in the offspring of rats exposed to sex hormone disrupting substances, including deformities of the reproductive tract, such as undescended testicles and hypospadias , alterations in bone mass (Migliaccio et al 1995), as well as the other effects which are not so immediately apparent, such as reduced sperm counts in males (Sharpe & Skakkebaek 1993).…”

A New Screening Model Using F1(AWE * WE) Japanese Quail Embryo for Evaluating Sex Reversal Effects

“…Using highly conserved primers flanking the intron of the gene, PCR amplification and agarose electrophoresis, 47 out of 50 bird species were successfully sexing 17 , whereas the method did not provide complete results and spent considerable cost and time. On the other hand, in ovo exposure of EDCs is the most important route in the birds [1][2][3]11 and avian eggs have been elucidated to be a good test system for evaluating effects of EDCs 5,[12][13][14][18][19][20][21][22] . Maternal transfer of 17 beta-estradiol benzoate (EB) to egg yolk has been demonstrated in Japanese quail, in which female quails received EB in the routs of i.m.…”

“…Therefore, it has been necessary to develop assessment systems to evaluate any adverse effects of EDCs in a variety of wildlife species. Birds are top predators in both aquatic and terrestrial environments and one of the most important wildlife species exposed by environmental pollutants with endocrine disrupting potential 2,3 . In facts, several species of colonial fish-eating birds, such as herring gulls, nesting in the Great Lakes basin have exhibited chronic impairment of reproduction, in which eggshell thinning is caused by high levels of DDT and its metabolites 4 .…”

A Review and Analysis of Study Endpoints Relevant to the Assessment of “Long Term” Pesticide Toxicity in Avian and Mammalian Wildlife

“…see Rattner et al, 1984 for an early review). It is beyond the scope of this chapter to review all the activity and proposals that have been made in this area.…”