PTTH - A potential growth activator in silkwonm, <i>Bombyx mori L. </i>for enhancing silk production

936-941In silkworm, prothoracicotropic hormone (PTTH), directly or indirectly controls silk production and spinning activity along with juvenile hormone (JH). An effort was made to exploit the potential of PTTH by indirectly activating silk gland for increasing silk productivity using short chain synthetic analogues of PTTH. The analogy in action was also established using PTTH extracted from the silkmoth. Different doses of 42 synthetic PTTH analogues, viz., 2.5, 5, 10 and 20 ppm and 3.3 mg/ml of PTTH extracted from silk moth heads were administered orally to V instar silkworm larvae (Race: KA×NB4D2 and PM× NB4D2) at 0-144 hr at an interval of 24 hr. The analysed data showed an improvement of about 14-23% in KA × NB4D2 and about 10-14% in PM×NB4D2 in respect of cocoon shell weight on administration of some of the synthetic PTTH analogues. The PTTH extracted from the adult brain also showed similar effect. The structural analogy of synthetic PTTHs (which improved the shell weight) with original PTTH and its probable mode of action in silkworm are discussed

Hormetic influence on silkworm, Bombyx mori L., of the Phytojuvenoid ω-Formyl longifolene oxime propargyl ether

The hormetic influence on silkworm, Bombyx mori L. (Lepidoptera: Bombycidae) of the juvenile hormone mimic ω-formyl longifolene oxime propargyl ether (NL13) was assayed. Emulsions containing 2.5, 5.0 and 10.0 ppm of the compound were administered topically as a single dose, to two popular commercial silkworm hybrids, viz. KA x NB 4 D 2 and PM x NB 4 D 2 , at 24, 48, 72 and 96 h into the 5th instar, and economic characters of the larvae and resultant cocoons measured. A medium and absolute control were maintained in parallel. It was found that administration of 5 ppm of NL13 to 48-h-old 5th instars resulted in the maximum improvement in commercial traits. The possible role of exogenous JH-like compounds in eliciting this response in silkworm is discussed. RÉSUMÉ L'influence hormonal du ω-formyl longifene oxime propargyl ether (NL13) imitant l'hormone juvénile a été testée sur le ver à soie, Bombyx mori L. (Lepidoptera: Bombycidae). Des émulsions contenant 2,5, 5,0 et 10,0 ppm du composé ont été administrées au 5ème stade larvaire, en une seule dose, à 24, 48, 72 et 96 h , à deux hybrides couramment commercialisés du ver à soie, viz KA x NB 4 D 2 et PM x NB 4 D 2 . Les caractéristiques économiques des larves et des cocons ont été mesurées. Un témoin moyen et absolu ont été maintenus en parallèle. On a constaté que l'administration de 5 ppm de NL13 à des larves de 5ème stade âgées de 48 h a permis une amélioration maximale des caractéristiques commerciales. Le rôle possible des composés exogènes, homologues de l'hormone juvénile, provoquant cette réponse chez le ver à soie est discuté