Viability of Lizard Eggs Exposed to Sea Water

Abstract

THE manner of dispersal of reptiles occurring in such island areas as those of the Pacific Ocean has frequently been a matter of speculation. One method, presumably open to oviparous species, is that of waif dispersal of the eggs by means of logs or other flotsam. Certainly the laying habits of many lizards, including those species with which the present study is concerned, make this means highly plausible and fragmentary observations have at times lent support to the hypothesis. Dammerman (1948) comments on the finding of eggs of Hemidactylus frenatus in hollows of a decayed tree trunk on the beach of Karakatau Island in February, 1928. These eggs were viable and he succeeded in hatching them. Since the origin of the log was not known, however, the extent to which the eggs had been exposed to sea water was also unknown. One aspect of this problem, viability under simulated conditions of exposure to salt water, as in the case of certain plants (Martins, 1857; Edmondson, 1941; Whitaker and Carter, 1954), is subject to experimental attack. Preliminary experiments, using the eggs of four species of Philippine lizards, were carried out by the authors at the Biological Laboratories, Silliman University, during the period from January to May, 1955. MATERIALS AND METHODS.-Eggs of Cosymbotus platyurus, Gehyra mutilata, Hemidactylus frenatus and Dasia smaragdina philippinica were used in the experiment. Those of the first three species were found in the bamboo poles or nipa palm shingles of native houses and also beneath the bark of trees both near and far removed from human habitation (These latter sites probably did not include eggs of Cosymbotus). The eggs of the scincoid lizard, Dasia smaragdina, were obtained from the pulpy wood of decaying stumps of both coconut and dicotyledonous trees. A total of 66 eggs was collected on seven different occasions between January 6 and March 30, 1955. Of these 31 were exposed to sea water under conditions that may simulate the degree of exposure to which such eggs might normally be subjected under rafting conditions 39