Study of intestinal morphology and neuropeptide cell density in diploid and triploid of Rhamdia quelen late larvae during fasting and refeeding

Abstract

Despite Rhamdia quelen is an attractive species for farming; its exploitation has not yet reached a satisfactory level in South America. To better understand optimal feeding and culture conditions for R. quelen late larvae, we assessed the effects of ploidy and fasting-refeeding on midgut structure and appetite regulators such as NPY and CCK-8. Regarding intestinal morphology, a short fasting period induced a significant decrease in villus height of fasted diploid (FD) and triploid (FT) groups. Also, a drop in villus width and enterocyte height was observed in FT and FD, respectively. No restoration of the mentioned parameters was accomplished in refed groups. In relation to goblet cells, a significant area decline was registered in diploids after fasting and refeeding, while goblet cell density increased in both diploid and triploid fish during refeeding. In relation to neuropeptides,within diploid fish, CCK-8+ cell density decreased during fasting and increased after 3 h of food ingestion. Surprisingly, NPY+ cell density was not affected by alimentary conditions in this fish group. On the other hand, within triploid larvae, CCK-8 and NPY immunoreactive cells increased only during refeeding. Finally, in relation to ploidy effect, only a few changes were registered in villus width and neuropeptide cell density.