Abstract

STUDIES ON THE ENDOCRINE REGULATION OF REPRODUCTION AND ULTRA STRUCTURE OF BRAIN AND REPRODUCTIVE ORGANS OF MUGA SILKWORM ANTHERAEA ASSAMENSIS, HELFER (LEPIDOPTERA: SATURNIIDAE)

*Kartik Neog, Bala G Unni, Sudip Dey, Collin Z. Renthlei, S G Eswara Reddy, Palash Dutta, Porismiti Sonowal and Rama Krishna Rajan

ABSTRACT

In this paper, we for the first time examined the effect of two endocrine hormones, JH-III and 20-hydroxy ecdysone (20-E) on reproductive behaviour and rearing performance parameters of muga silkworm, Antheraea assamensis. Topical application of 20-E at 15μg and JH-III at 10μg concentrations per larva was done on the first day of fifth instar larvae. Application of 20-E resulted into minimum larval duration (6 days), maximum cocoon formation (79%), significantly highest pupal and shell weight (6.61g and 0.58g, respectively) followed by JH-III application. Application of JH-III and 20-E significantly enhanced fecundity from normal 100-115 eggs to 150-166 eggs per moth during different seasons. Retention of eggs by the moths was also minimum under treatment of 20-E (13.44 nos.) followed by that of JH-III. Vitellogenin synthesis in the pupal, pharate adult, normal and retained eggs was significantly higher when the worms were treated with 20-E. The ovary of pupae were significantly longer when insects were treated with 20-E and JH-III (9.63±0.58 and 9.31±0.27 cm, respectively), compared to untreated normal female 8.65±0.22 cm. Ultra structure of brain and ovary of larvae and pupae of the untreated silkworm as well as those under the influence of treatment of JH-III and 20-E was also studied.

Keywords: Muga silkworm, Antheraea assamensis, fecundity, reproduction, egg retention, juvenile hormone, ecdysteroid.