Morphometric Variations in Gastropod Species: A Comparative Study of Nerita albicilla and Patella nigra

This study aims to compare the morphometric characteristics of Nerita albicilla and Patella nigra and to determine the allometric relationships between the shell weight, shell length, fresh weight, dry weight, tissue weight and shell weight. A total of 200 of Nerita albicilla and Patella nigra were collected along the coasts of Zamboanga City Bay, Western Mindanao, Philippines. Nerita albicilla has the highest mean ± SD in width (1.59 ± 0.19 mm), fresh weight (2.59 ± 0.15 g), tissue weight (1.26 ± 0.83 g), dry weight (2.38 ± 0.55 g) and shell weight (2.19 ± 0.11 g). The fresh weight of Nerita albicilla was strongly related with the shell length. The shell width of Patella nigra was slightly correlated with shell weight. There was slight correlation between the shell width and shell weight and these can be attributed to the developmental, environmental and abiotic factors that highly contribute to the morphology of the gastropods. The calcium carbonate content suspended in the environment has major effect in the shell composition and is directly related with the shell weight. Nutrition is also a major contributory factor in the weight of the shells.