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The diet, water and electrolyte balance, and thermoregulation of the geometric tortoise, Psammobates geometricus (Linnaeus, 1758) (Cryptodira: testudinidae)
Thesis (M. Sc.) -- University of Stellenbosch, 1995.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2012
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| _version_ | 1867613913515819008 |
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| access_status_str | Open Access |
| author | Engelbrecht, E |
| author2 | Sadie, D. |
| author_browse | Engelbrecht, E Sadie, D. |
| author_facet | Sadie, D. Engelbrecht, E |
| author_sort | Engelbrecht, E |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (M. Sc.) -- University of Stellenbosch, 1995. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/54875 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:43:41.995Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2012 |
| publishDateRange | 2012 |
| publishDateSort | 2012 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/54875 The diet, water and electrolyte balance, and thermoregulation of the geometric tortoise, Psammobates geometricus (Linnaeus, 1758) (Cryptodira: testudinidae) Engelbrecht, E Sadie, D. Baard, E. H. W. Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology. Turtles -- Physiology Turtles -- Food Turtles -- Effect of temperature on Dissertations -- Zoology Thesis (M. Sc.) -- University of Stellenbosch, 1995. The main objective of the current study was to investigate the water balance of Psammobates geometricus. Key elements relating to the water balance, i.e., aspects of thermoregulation, water and electrolyte content of the food, and the composition of urine and plasma samples, were investigated. The geometric tortoise appears to be primarily thigmothermic in the early morning, gaining heat exclusively from the soil. As the day progresses, air and shell temperatures play an increasingly important role in heat exchange, and the tortoise is mainly heliothermic during midday. The geometric tortoise has the ability to alter its rates of heating and cooling, either physiologically or behaviourally. Activity takes place over a wide range of environmental and body temperatures. Water gain via external routes (drinking, preformed water in the food) varies during the year. Water is available during the wet seasons, but not during the dry seasons. The geometric tortoise has, however, never been observed drinking water during the study period. The moisture content of the winter diet was higher than that of the summer diet, although not statistically significant. Water loss via excreted feces is low, and evaporative water loss, compared to other terrestrial chelonians from similar climates, is low, and compares better to that of the desert tortoise. P. geometricus therefore appears to be adapted to living in arid conditions. Furthermore, urinary sodium levels were low during dry seasons, suggesting that sodium and consequently water were being reabsorbed. This lends to further water conservation. In the rainy seasons urinary sodium levels remained at a constant high level, indicating there was no need to conserve large amounts of water. Nitrogenous waste management shifts seasonally, with urea being the primary component in urine and plasma during the dry summer and autumn, while uric acid dominates in the rainy winter and spring. Masters 2012-08-27T11:36:46Z 2012-08-27T11:36:46Z 1995-12 Thesis http://hdl.handle.net/10019.1/54875 en Stellenbosch University 194 pages : ill. Stellenbosch : Stellenbosch University |
| spellingShingle | Turtles -- Physiology Turtles -- Food Turtles -- Effect of temperature on Dissertations -- Zoology Engelbrecht, E The diet, water and electrolyte balance, and thermoregulation of the geometric tortoise, Psammobates geometricus (Linnaeus, 1758) (Cryptodira: testudinidae) |
| title | The diet, water and electrolyte balance, and thermoregulation of the geometric tortoise, Psammobates geometricus (Linnaeus, 1758) (Cryptodira: testudinidae) |
| title_full | The diet, water and electrolyte balance, and thermoregulation of the geometric tortoise, Psammobates geometricus (Linnaeus, 1758) (Cryptodira: testudinidae) |
| title_fullStr | The diet, water and electrolyte balance, and thermoregulation of the geometric tortoise, Psammobates geometricus (Linnaeus, 1758) (Cryptodira: testudinidae) |
| title_full_unstemmed | The diet, water and electrolyte balance, and thermoregulation of the geometric tortoise, Psammobates geometricus (Linnaeus, 1758) (Cryptodira: testudinidae) |
| title_short | The diet, water and electrolyte balance, and thermoregulation of the geometric tortoise, Psammobates geometricus (Linnaeus, 1758) (Cryptodira: testudinidae) |
| title_sort | diet water and electrolyte balance and thermoregulation of the geometric tortoise psammobates geometricus linnaeus 1758 cryptodira testudinidae |
| topic | Turtles -- Physiology Turtles -- Food Turtles -- Effect of temperature on Dissertations -- Zoology |
| url | http://hdl.handle.net/10019.1/54875 |
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