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Distribution, modes of attachment and heat tolerance of Nodilittorina sp. and Littoraria sp. at Labrador beach and Tanjung Chek Jawa
Author
Lee, Su Li
Supervisor
Lim, Shirley S. L.
Abstract
The distribution, certain aspects of morphology, modes of attachment and heat tolerance of three littorinid species: Littoraria sp.,Nodilittorina trochoides and N vidua, at Labrador beach (mainland Singapore) and Taniung Chek Jawa (Pulau Ubin) were studied. Foci of study included distribution patterns, effect of transplantation, comparison of shell morphometrics, effect of removal of shell sculpturing, occurrence of headstand behaviour, effect of substrate inclination on headstand behaviour, comparison of lethal temperatures (LT50) and comparison of the heat stability of the enzyme glutamate oxaloacetate transaminase (GOT).
Littoraria sp. and N. vidua were found below MHWS while N trochoides was generally found above and about MHWS. Transplantation of Littoraria sp. and N. trochoides indicated movement of individuals back to their preferred zones. The proportion of Littoraria sp. and N. trochoides individuals found in crevices decreased in the cooler month of December. There were also less mucous-holdfast attachments by individuals in December. The size gradients and population size structures observed differed between species and among sites, possibly due to various factors, e.g., spawning activity.
The three littorinids were of different shapes that likely enabled them to survive in their respective zones. Shell sculpturing of N. trochoides aided the reflection of heat energy from the shell surface. Headstand behaviour was dependent on species-type, and was likely to also be dependent on substratum characteristics. Of the three littorinids at the collection site, the largest proportion of individuals in the headstand posture was from the N vidua population.
There was no difference in temperature at which individuals of the three species retracted their foot. No relationship between the temperatures of foot retraction and size of the individuals was observed. Nodilittorina trochoides had the highest LTs0 of 50.5OC, followed by N vidua (48.2'C) and Littoraria sp. (47.5OC). The enzyme GOT from N. trochoides was most stable after incubation at 55OC while that of N vidua was most unstable after the same treatment.
Adaptation to the harsh environment high up in the intertidal zone is multifold. It encompasses morphological, behavioural and physiological aspects. Results of this study showed that loss of morphological and behavioural adaptations did not reduce the ability of N trochoides to inhabit its preferred zone. Thus, physiological adaptations were probably of primary importance in the long term survival of littorinids in stressful environments.
Littoraria sp. and N. vidua were found below MHWS while N trochoides was generally found above and about MHWS. Transplantation of Littoraria sp. and N. trochoides indicated movement of individuals back to their preferred zones. The proportion of Littoraria sp. and N. trochoides individuals found in crevices decreased in the cooler month of December. There were also less mucous-holdfast attachments by individuals in December. The size gradients and population size structures observed differed between species and among sites, possibly due to various factors, e.g., spawning activity.
The three littorinids were of different shapes that likely enabled them to survive in their respective zones. Shell sculpturing of N. trochoides aided the reflection of heat energy from the shell surface. Headstand behaviour was dependent on species-type, and was likely to also be dependent on substratum characteristics. Of the three littorinids at the collection site, the largest proportion of individuals in the headstand posture was from the N vidua population.
There was no difference in temperature at which individuals of the three species retracted their foot. No relationship between the temperatures of foot retraction and size of the individuals was observed. Nodilittorina trochoides had the highest LTs0 of 50.5OC, followed by N vidua (48.2'C) and Littoraria sp. (47.5OC). The enzyme GOT from N. trochoides was most stable after incubation at 55OC while that of N vidua was most unstable after the same treatment.
Adaptation to the harsh environment high up in the intertidal zone is multifold. It encompasses morphological, behavioural and physiological aspects. Results of this study showed that loss of morphological and behavioural adaptations did not reduce the ability of N trochoides to inhabit its preferred zone. Thus, physiological adaptations were probably of primary importance in the long term survival of littorinids in stressful environments.
Date Issued
2003
Call Number
QL430.5.L58 Lee
Date Submitted
2003