Sex-specific compensatory growth in food-deprived Nile tilapia

Abstract

Female Nile tilapia incubate fertilized eggs in their mouth until they are released as alevins. Consequently, the female may not eat during this period. Thus, it would be expected that female Nile tilapia are more adapted to recovering from fasting than males, which do not display this behavior. To test this hypothesis we conducted an experiment with two groups of fish consisting of 7 males and 7 females each, with one fish per aquarium. The experiment was divided into three phases involving adjustment of the animals to experimental aquaria (0-15th day), fasting (16th-27th day), and refeeding (27th-42nd day). Compensatory growth performance was assessed by specific growth rate, weight, food conversion efficiency and food intake. Food conversion efficiency increased after fasting with a similar rate for both sexes. However, specific growth rate, food intake and weight gain (%) were significantly higher in males than in females in the refeeding phase. Thus, we conclude that male Nile tilapia can compensate for a fasting period more efficiently than females, refuting our hypothesis. A possible mechanism involved in the greater male compensation is that they presented greater hyperphagia than females, concomitantly with a similar rate of food conversion efficiency for both sexes during refeeding, which would probably be provoking greater growth in males.

Correlations Between Pre- and Post-Fasting Growth in Nile Tilapia

“…Growth performance increased in response to food deprivation, as previously reported for this species (Takagi, 2001;Barreto et al, 2003).…”

“…In fact, food restriction facilitates learning of available food patches in Nile tilapia (Delicio and Barreto, ZOOS), what is not obserevd in well-fed ones (Delicio et al, 2006). Our data show that SGR increased after food deprivation (Table 11, as previously reported for this species (Takagi, 2001;Barreto et al, 2003). The most striking finding, however, was that the upward shift in mean post-food-deprivation SGR relative to prefasting one was not random; the shifts between SGRs were kept proportionally between individuals.…”

Effects of betaine on the growth of the fish piauçu, Leporinus macrocephalus

“…Thus, the daily food ingestion for each individual was calculated by the difference between the food dry weight before and after this handling. The rate of loss of uneaten food was evaluated by adding a weighed amount of food into the aquarium containing only water for 60 minutes and then collected, dried and re-weighted (Barreto et al, 2003). No loss of uneaten food due to leaching or breaking up was detected.…”

“…Piauçu, Leporinus macrocephalus (a South American Anostomid), is a species that has recently been commercially cultured for human consumption with a growing aquacultural activity in South America (Albrecht et al, 2001). Accordingly, techniques to improve piauçu growth are very interesting goal for aquaculture practices in which growth rate represents an economically important trait (Moreau et al, 2003;Barreto et al, 2003). Betaine could be a possibility for improving piauçu growth rate.…”

Stomach fullness modulates prey size choice in the frillfin goby, Bathygobius soporator

“…Three batches of 5 fish each were killed 24 h, 48 h or 72 h after feeding. Food intake was measured as in Barreto et al (2003b). In addition, the relationship between body size and food intake to satiety was used to estimate the amount of food necessary to achieve half stomach fullness for each fish.…”