Hormonal and Reproductive Effects of Low Levels of Petroleum Fouling in Magellanic Penguins (Spheniscus magellanicus)

Fowler, Gene S.; Wingfield, John C.; Boersma, P. Dee

doi:10.2307/4088725

Cited by 71 publications

(27 citation statements)

References 24 publications

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“…In addition, Dunlap and Schall (18) found no increase in basal CORT levels in Western fence lizards (Sceloporus occidentalis) that were infected with a malarial parasite, although infected animals had significantly higher CORT responses to acute stress. Also, Fowler et al (19) found significantly elevated basal CORT in Magellanic penguins (S. magellanicus) that had been oiled and then washed after a tanker spill. These and other studies consistently suggest that chronic stress is associated with an elevation of CORT at basal and/or stress induced levels.…”

Section: Discussionmentioning

confidence: 99%

“…Examples include studies on the hormonal effects of oiling due to a tanker spill on a breeding colony of Magellanic penguins (Spheniscus magellanicus) and the efficacy of washing oiled birds in reducing stress (19); correlations between fecal steroids and predation threat, food accessibility, and individual social status in female ring-tailed lemurs Lemur catta (9); and measurements of CORT in Galapagos marine iguanas (Amblyrhynchus cristatus) under famine conditions of a severe El Niño (39). To fully understand the field data being collected, it is imperative that the physiology of chronic stress in nonmammalian species be characterized under controlled, laboratory conditions.…”

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confidence: 99%

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Exposure to chronic stress downregulates corticosterone responses to acute stressors

Rich

Romero

2005

American Journal of Physiology-Regulatory, Integrative and Comp

367

285

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(Sturnus vulgaris) to test whether corticosterone responses differed in birds held under normal laboratory conditions or conditions of chronic stress. Surprisingly, both basal corticosterone concentrations and corticosterone responses to acute stress were significantly reduced when birds were chronically stressed. To determine the mechanism underlying this reduced response, animals under both conditions were injected with lactated Ringer's solution (control), adrenocorticotropin (ACTH), arginine vasotocin (AVT), or dexamethasone (DEX). ACTH increased corticosterone concentrations above stress-induced levels in both cases, although maximum responses were lower in chronically stressed birds. AVT did not augment the corticosterone response under nonchronically stressed conditions, but it did under chronically stressed conditions. DEX reduced maximal corticosterone concentrations in both cases. Neither ovine nor rat corticotropin-releasing factor (CRF) altered normal stress responses. These data indicate that changes in responsiveness of the hypothalamic-pituitary-adrenal axis to ACTH and AVT serve to downregulate corticosterone responses during chronic stress. Furthermore, these data lead to the following hypothesis: ACTH output from the pituitary limits maximum corticosterone concentrations under normal conditions, but reduced AVT release from the hypothalamus regulates lower corticosterone concentrations under chronic stress conditions. environmental stress; negative feedback; hypothalamic-pituitary-adrenal axis; conservation GLUCOCORTICOIDS ARE STEROID hormones released from adrenal tissue in response to stressful stimuli. Upon perception of stress, the avian hypothalamus is activated to secrete arginine vasotocin (AVT, a congener of the mammalian arginine vasopressin) and corticotropin-releasing factor (CRF), which stimulate the pituitary to release adrenocorticotropin (ACTH), in turn, causing the release of glucocorticoids from the adrenals (7,8). This pathway constitutes the hypothalamic-pituitaryadrenal (HPA) axis, and its activation is one component of the physiological stress response. This response is believed to be aimed at maintaining or restoring homeostasis, thereby helping the animal to survive a stressful episode (45, 50). The primary avian glucocorticoid is corticosterone (CORT) (22).The presumed benefits of an acute activation of the HPA axis contrast with chronic activation. Various deleterious effects of chronic CORT elevation have been documented in many species, including suppression of reproductive function and behavior, immune system suppression, muscle wasting, growth suppression, and neuronal cell death (45, 49). Chronic stress generally produces chronic elevations in baseline CORT concentrations. However, studies of chronically stressed rats indicate that facilitation of the HPA axis takes place to maintain responsiveness to acute stressors (11,13,25), perhaps by increasing the role of vasopressin over CRF in the release of ACTH (1, 16, 17). Therefore, animals must avoid chronic stress ...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Exposure to chronic stress downregulates corticosterone responses to acute stressors

Rich

Romero

2005

American Journal of Physiology-Regulatory, Integrative and Comp

367

285

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“…The ubiquity of the organism suggests that birds may be carriers of the fungi but do not develop overt disease unless stimulated by a decreased resistance of the host elicited by some stress such as an infectious disease, a toxicant, or malnutrition. Experiments indicated that birds subjected to a handling stress had higher levels of corticosteroids (Fowler et al, 1995;Fowler, 1999;Deem, 2003;Park, 2003;Balseiro et al, 2005), which can affect the immune system in many ways (Griffin, 1989).…”

Section: Discussionmentioning

confidence: 99%

Fungal flora in the trachea of birds from a wildlife rehabilitation centre in Spain

García¹,

Lanzarot²,

Rodas³

et al. 2007

Vet. Med.

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ABSTRACT:In the present work we study the prevalence of fungal flora in the tracheal epithelium of wild birds in a rehabilitation centre. Two hundred and sixteen birds representing 26 species from seven orders were sampled. Yeasts and moulds were isolated from 92 of the birds sampled (42.5%); in 24.5% only yeasts, in 12.5% only moulds and in 5.5% both moulds and yeasts together. The cattle egret was where the greatest number of animals with positive isolation was detected. The prevalence of yeasts shows significant differences between raptors and Ciconiiformes. Within the yeast flora, basically there were strains belonging to the genus Candida, mainly C. albicans. In the moulds, almost a half of them belonged to the genus Aspergillus.

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“…When Magellanic penguins were oiled in Argentina, some were brought into captivity for rehabilitation. However, this approach is questionable given that Fowler et al [54] conclude that oiled penguins held captive for washing had elevated corticosterone levels and appeared to be stressed both by captivity and by the washing process. It is so far unclear what the long-term effects of captive treatment are in these specific instances.…”

Section: Box 1 Physiological Assessment Of Environmental Stressorsmentioning

confidence: 99%

Conservation physiology

Wikelski

Cooke

2006

Trends in Ecology & Evolution

709

623

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Hormonal and Reproductive Effects of Low Levels of Petroleum Fouling in Magellanic Penguins (Spheniscus magellanicus)

Cited by 71 publications

References 24 publications

Exposure to chronic stress downregulates corticosterone responses to acute stressors

Exposure to chronic stress downregulates corticosterone responses to acute stressors

Fungal flora in the trachea of birds from a wildlife rehabilitation centre in Spain

Conservation physiology

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