The physiology of lizards from arid regions in Central Otago.
MacAvoy, Elizabeth S.
The seasonal cycles in fat bodies, liver and gonads of Leiolopisma zelandica and Hoplodactylus pacificus have been established and the pattern of lipid storage and utilization in these organs, the tail and remaining carcass was also investigated. Each month skinks and geckos were collected in Central Otago. After dissection each organ was weighed and the lipid extracted. Liver glycogen was estimated. Four times during the year lipid was analysed by thin layer and gas liquid chromatography. Microscopic examination of reproductive organs was undertaken each month. Ultrastructure of the liver and enzymatic activity in the liver and tail and leg muscle was compared in winter and summer. Skinks have large fat bodies which act as a major lipid depot. Utilization of stored lipid occurs during yolk production and hibernation in females and during breeding and hibernation in males. Gecko fat bodies show only slight seasonal variations and cannot be regarded as important depot organs. Liver weights reached a maximum prior to hibernation in females and during hibernation in males and decreased in spring in females and during spring and the breeding season in males. Peaks in liver glycogen occurred in January, March and September (females) or November (males). Liver glycogen decreased to a minimum at the end of hibernation. Liver lipid increased during hibernation due to mobilization from depot organs but decreased to a minimum in spring. The liver cannot be regarded as a lipid depot organ. An increase in melanin pigment, autophagic vacuoles and residual bodies was evident in winter liver. Oxidation of fatty acids meets the energy requirements during winter. Enzymatic activity in the skink liver is decreased in midwinter compared to midsummer but in gecko liver, enzymatic activity is higher in midwinter. Males emerge from hibernation with small testes, testicular recrudescence occurs in spring and maximum testes size is reached in January. Mating occurs in February and March and coincides with the initiation of vitellogenesis in females. The period of yolk deposition extends from February to September in geckos and from March to September in skinks. Ovulation occurs in September and delayed fertilization is achieved by spermatozoa which have been stored in the female reproductive tract over winter. Geckos produce two young and skinks an average of three in January and February after a gestation period of three to four months. Structurally female and male reproductive tracts resemble those of other lizards. The tail acts as an important lipid depot organ in skinks and geckos. In geckos the carcass stores large amounts of lipid but the skinks carcass shows little variation throughout the year. Fatty acid oxidation provides energy for muscular contraction during winter. The periods of maximum lipid storage occur in November and December in males, during March in female skinks and from September to December in female geckos. The majority of this lipid is utilized for yolk deposition in females and during the breeding period in males. Lipid is also utilized during hibernation.
Advisor: Pilkington, John B.
Degree Name: Doctor of Philosophy
Degree Discipline: Zoology
Publisher: University of Otago
Research Type: Thesis