Effect of 20-OH ecdysone and methyl farnesoate on histomorphology of the Y-organ during late intermoult and postmoult stages in the freshwater crab Travancoriana schirnerae Bott, 1969 (Crustacea: Gecarcinucidae)

Abstract

This study investigated the effects of 20-OH ecdysone (20E) and methyl farnesoate (MF) administration on histomorphology of the Y-organ (YO) during late intermoult (C3 and C4) and early postmoult stages in the edible freshwater crab Travancoriana schirnerae Bott, 1969, widely distributed in the wetlands of Wayanad, Kerala, India. Histomorphological analyses of the 20E and MF administered crabs revealed that both 20E and MF were effective in inducing significant changes in YO during the late intermoult (P < 0.001) and early postmoult (P < 0.05) stages, as evidenced from a significant rise in the YO index (YO index = wet weight of YO/body weight of crab × 100), size of the gland and lobules, height of the lobular epithelium, cellular hypertrophy, presence of secretory vesicles and abundance of hemocytes. The results also indicated that the effects were more pronounced during the late intermoult stages than the postmoult stage and in the 20E administered crabs than the MF administered individuals. The percent increments in YO index, length and width of the gland and lobules and thickness of the lobular epithelium in 20E and MF injected crabs during the late intermoult stages were 25.95, 20.04, 27.22, 52.15, 67.24, 114.50 % and 16.19, 9.09, 14.45, 21.87, 23.97, 65.25 %, respectively while those of early postmoult were 13.63, 24.04, 25.73, 23.86, 26.13, 38.01 % and 9.09, 15.27, 19.85, 14.95, 19.65, 26.54 %, respectively. In conclusion, 20E and MF administration provide an excellent option for stimulation of YO, thereby inducing ecdysis and growth during the inactive stages (intermoult and postmoult) of the moult cycle.

Keywords
20-OH ecdysone; histomorphology; intermoult; methyl farnesoate; postmoult