|Laticauda colubrina. JCM|
In a forthcoming article in the Journal of Zoology Wang et al. (2013) report on the variation of characters in three species of Laticauda at Orchid Island, Taiwan. Previous research revealed that the phylogenetic and taxonomic status of the laticaudine sea kraits had been widely discussed in the literature. They found all three species are amphibious, but they differ in their tendency to spend time in marine or terrestrial environments. These sympatric sea kraits are most conspicuous in coastal areas where they tend to be most active at night. Laticauda semifasciata tends to remain submerged in shallow coastal waters; L. laticaudata largely stay above water, but not far from the edge of the sea and L. colubrina exhibit a greater tendency to emerge from water and move farther away from it. Thus, the tendency toward more completely marine habits is highest in L. semifasciata, lowest in L. colubrina and intermediate in L. laticaudata. The authors test the hypothesis that such a species gradient in behavior should be correlated with parallel adjustments in morphological and physiological character states.
All three species move into coastal areas at night. Generally, Laticauda semifasciata remain submerged in sea water, L. laticaudata emerge onto land, but remain not far from the water’s edge, and L. colubrina tend to move farther inland away from the water. They measured parameters of the body shape, vascular lung, saccular lung and hematocrit of sea kraits to investigate possible morphological correlates of their physiology. The most aquatic species, L. semifasciata, had a significantly more laterally flattened body form, larger saccular lung volume and higher hematocrit than the other two species, whereas only few differences were found between the two less aquatic species. L. laticaudata had a significantly higher hematocrit than L. colubrina.
Wang, S., Lillywhite, H. B., Cheng, Y. C. and Tu, M. C. (2013), Variation of traits and habitat use in three species of sea kraits in Taiwan. Journal of Zoology, 290: 19–26. doi: 10.1111/jzo.12012