Stable carbon (tp#pdC) and nitrogen (tp#eN) isotopes as natural indicators of live and dry food in Piaractus mesopotamicus (Holmberg, 1887) larval tissue

摘要

This study proposed the use of the stable isotope technique to track the type of food utilized by pacu Piaractus mesopotamicus larvae during their development, and to identify the moment when the larvae start using nutrients from the dry diet by retaining its carbon and nitrogen atoms in their body tissues. Five-day-old pacu larvae at the onset of exogenous feeding were fed Artemia nauplii or formulated diet exclusively; nauplii+formulated diet during the entire period; or were weaned from nauplii to a dry diet after 3, 6 or 12 days after the first feeding. tp#pdC and tp#eN values for Artemia nauplii were -15.1[per thousand] and 4.7[per thousand], respectively, and -25.0[per thousand] and 7.4[per thousand] for the dry diet. The initial isotopic composition of the larval tissue was -20.2[per thousand] and 9.5[per thousand] for tp#pdC and tp#eN respectively. Later, at the end of a 42-day feeding period, larvae fed Artemia nauplii alone reached values of -12.7[per thousand] and 7.0[per thousand] for tp#pdC and tp#eN respectively. Larvae that received the formulated diet alone showed values of -22.7[per thousand] for tp#pdC and 9.6[per thousand] for tp#eN. The stable isotope technique was precise, and the time at which the larvae utilized Artemia nauplii, and later dry diet as a food source could be clearly defined.