Correlation between body size and fecundity in fish louse Argulus bengalensis Ramakrishna, 1951 (Crustacea: Branchiura)

The life history traits like fecundity and body size are useful predictors of life history strategies of organisms. The information on these aspects provided necessary input for control measures for ectoparasites. In view of this, the variations in the life history traits of the fish louse Argulus bengalensis Ramakrishna (1951) were assessed using age as an explanatory factor. The analyses revealed that the body weight (BW) is related to age in males as: y (BW) = 0.03 × (Age)–2.58: and in females as: y (BW) = 0.89 + 0.13x (Age). The body length and age relationship in males is observed as: y (BL) = 2.94 + 0.01x (Age) and in females as: y (BL) = 2.89 + 0.06x (Age). The degree of sexual dimorphism (DD) for BL is positively correlated (r = −0.358; df = 43; P < 0.001) with age while DD for BW is negatively correlated (r = −0.525; df = 43; P < 0.001) with age. The eggs/clutch remained between 02 and 43 for the 21st and 38th day old females. The fecundity as a function of age could be represented as: y (Eggs) = 1.62x (Age)–27.92. The increase in BW with age in female A. bengalensis favoured greater resource allocation for egg production, while in males it likely favours dispersal ability. Since body size and fecundity varied with age, the relative abundance and extent of infestation in fish host would vary with age composition of the population and recruitment of juveniles. The impacts of host specific variations on these features need to be tested further.