VARIATION IN ENERGY CONTENT OF SOMATIC AND REPRODUCTIVE, TISSUES RELATED TO THE REPRODUCTIVE CYCLE AND FEEDING OF FEMALE Pimelodus maculatus Lacépède, 1803 (Siluriformes, Pimelodidae) AND Schizodon borellii Boulenger, 1895 (Characiformes, Anostomida

Abstract

The aim of this paper is to test a hypothesis that the variation trends in the energy content of the somatic and reproductive tissues and feeding activity are a function of the reproductive cycle in female S. borellii and P. maculatus under natural conditions and elucidated aspects of the energetic equilibrium of these species. Specimens were caught in the upper Paraná River floodplain (22º40’ - 22º50’S and 53º10’ - 53º40’W) from March 1992 to February 1994. Eighteen female S. borellii and twenty-one P. maculatus in the immature, resting, maturing and mature stages of the reproductive cycle were sampled for muscle, liver and gonad calorimetry. Means of the condition factor, stomach repletion index and visceral-somatic relation were obtained for the same stages from biometric data. Results reveal the patterns in the allocation equilibrium of female S. borellii and P. maculatus during the reproductive period. Since significant variations in the energy content of reproductive components related to vitellogenesis occur even with a decrease in feeding activity in adult and without any detriment to somatic reserves (skeletal muscle and liver) and to the somatic growth, we propose the hypothesis that in this phase of the reproductive process, visceral fat functions as an accessory source of energy which guarantees gonadal development and the maintenance of other components.