Biometrics, gut contents and sexual dimorphism of the west African mud creeper, Tympanotonus fuscatus var radula (Linnaeus, 1758) from the Mangrove swamps of a Coastal Estuary in Nigeria

Abstract

The biometrics, gut contents and sex ratio of the West African Mud Creeper, Tympanotonus fuscatus var radula from Mangrove swamps of the University of Lagos Lagoon Front were studied for 12 months. Tympanotonus fuscatus var radula has an elongated shell with regular increasing whorls, weakly curved ribs and much fine striation with blackish brown stripes on the shell. A total of 1135 samples were collected with highest species occurrence in August (11%). The total length ranged from 1.9 to 5.3 cm and total weight from 1.5 to 7.4g. The gastropod exhibited negative allometric growth with regression coefficient “b” of 1.19 values (b < 3). There was strong significant correlation between whorl number and shell length (Correlation coefficient, r = 0.625, P < 0.01). Monthly condition factor (K) for the combined sex ranged between 6.36 and 7.85 with a mean of 7.07. Out of a total number of 1135 samples collected, 544 (48%) had empty stomachs. The index of relative importance (IRI) showed diatom, plant materials and organic debris as primary food items while bacteria and seaweed were secondary items. Hence, the species can be said to be a deposit feeder. Sex ratio obtained during the study was 1:2.3 which was significantly different from the expected 1: 1 ratio. Availability of more femalespermits continuous laying of eggs, thus making the species available all year round.