Comparative morphology and ph of the alimentary tract in <i>Archachatina marginata</i> and <i>Achatina achatina</i>

Abstract

A study was carried out to investigate the comparative morphology and pH of the gut in the Giant African Land Snails, in Archachatina marginata and Achatina achatina respectively. The crop is long, distended and less fleshy with reddish brown coloured juice (5.8 ml volume) in A. marginata, while it is short, compact and fleshy with greenish brown coloured juice (3.2 ml volume) in A. achatina. The digestive gland was heavier (17.36 vs. 15.74 g) in the latter than the former. The absolute weight of the crop in A. marginata was significantly (p<0.05) higher than in A. Achatina, however, the absolute and relative weights of the digestive gland in A. achatina was significantly (p<0.05) higher than in A. marginata. There were significant (p<0.05) differences in linear measurements of the salivary gland and crop for absolute values and the salivary gland, crop, stomach and digestive gland for relative values. Archachatina marginata had significantly (p<0.05) longer salivary gland and crop than Achatina achatina for absolute length values and significantly (p<0.05) longer salivary gland, crop and digestive gland for relative length values. However, the relative stomach length in A. achatina was significantly (p<0.05) longer than in A. marginata. The gut pH was more acidic in the crop (5.38 and 4.83) than in the mouth (6.93 and 6.82) where it tended towards neutrality in A. marginata and A. achatina respectively. The pH profiles in the two species, decreased by 1.65 and 1.99 from the mouth to the crop while it increased by 1.46 and 1.97 from the crop to the distal digestive gland in A. marginata and A. achatina respectively. In the herbivorous snails, the pH along the gut regions remained acidic all through (5.38 – 6.93 and 4.83 – 6.82) in A. marginata and A. achatina respectively, confirming the herbivorous habits in these snail species. The longer gut and distended crop with higher volume of crop juice in A. marginata, implies its ability to store, utilize and digest more food materials than A. achatina. These results provide the basis for a better understanding of the physiology of the digestive processes in these snails.