Corticosteroid dynamics in a free-ranging population of olive Ridley sea turtles (Lepidochelys olivacea Eschscholtz, 1829) at Playa Nancite, Costa Rica as a function of their reproductive behavior /
Adrenocortical dynamics of free-ranging, reproductively
| Main Author: | |
|---|---|
| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1996.
|
| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=739364101&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Adrenocortical dynamics of free-ranging, reproductively active olive Ridley (Lepidochelys olivacea) sea turtles were examined during the peak nesting season at Nancite beach, Santa Rosa National Park, Costa Rica. Because the unique mass nesting behavior of the genus Lepidochelys represents a potential stress, the objective of this study was to determine if the activity of the hypothalamo-pituitary- adrenal (BPA) axis is altered during nesting. Initially, basal levels of corticosterone (B) were measured in association with the reproductive steroids progesterone (P4) and testosterone (T) in periovulatory and nesting turtles. B levels were generally low and stable in all untreated turtles. No evidence for a daily cycle of B was observed in animals captured in the water prior to nesting. Nesting animals exhibited B levels significantly elevated over animals basking in the water. B levels were also significantly correlated with P4 but not with T during ovulation, indicating that B may function in both the ovulatory and nesting processes. Functional integrity of the BPA axis in nesting animals was examined by subjecting the animals to both endogenous (an imposed stress, flipping on their backs) and exogenous (injection of adrenocorticotropic hormone [ACTH] and corticotropin-releasing hormone [CRH]) stimuli. In response to flipping, B levels rose slowly over 2 hours. The rate of increase was much slower than observed during stress activation of B secretion in other vertebrates, and was unaffected by CRH. ACTH, however, caused an immediate (less than 15 minutes) increase in B levels. No differences in adrenocorticotropical responsiveness were observed between animals participating in the mass nesting and intemesting or solitary nesters. Additionally, none of the increases in B observed were associated with consistent changes in blood glucose, indicating that B may lack hyperglycemic effects in this species. The olive Ridley sea turtle therefore appears to have a relatively inactive BPA axis, although rapid activation of B release can be stimulated exogenously. It does not appear that the sensitivity of this axis is altered during nesting. |
|---|---|
| Item Description: | Vita. "Major Subject: Zoology". |
| Physical Description: | xiv, 147 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 133-147. |