Abstract: Understanding the hatching patterns in the commercial mulberry silkworm, Bombyx mori L., at laboratory level are amply available. Hatching phenomenon at farmers’ level, however, is completely lacking and such knowledge is more crucial for successful commercial cocoon crop of Bombyx silkworm. Present study engendered certain important results, in contrast to the earlier reported hatching patterns under various photoperiodic conditions at laboratory level. Further, it reports strange hatching parameters of bivoltine x bivoltine silkworm hybrid, CSR2 x CSR4, more popular in contemporary Indian sericulture. Disease free layings (DFLs) of CSR2 x CSR4 were introduced into four common photoperiodic conditions; LD 12 : 12 (natural day), DD (continuous dark), LL (continuous light) and Black-Box conditions on the third day of oviposition, at the rearing houses of five selected sericulture farmers of Mudigubba Mandal, Anantapur District, Andhra Pradesh. Other environmental conditions, temperature and relative humidity were not altered, keeping the farmers practice. Dial variations in both temperature and humidity were recorded to examine rhythmicity and their possible implications on the hatching rhythmicity in CSR2 x CSR4. Number of silkworm larvae hatched-out from experimental eggs was recorded on hourly basis from five replications each of five farmers. Experiments were repeated for five times. Recorded macroscopic data were converted into percentage and represented as chronograms for analysis. Results on hatching irrevocably revealed that CSR2 x CSR4 hatching rhythmicity under LD 12 : 12 conditions did not change, occurring for 2 consecutive days, with less hatching on day 1. Hatching rhythmicity under DD/LL also occurred for two consecutive days. Against the hypothesis, hatching phase neither advanced under DD nor delayed with LL conditions imposed. Hatching rhythmicity was circadian, diurnal, taking ‘lights-on’ as signal as synchronizing cue, however without expressing free-running nature under DD/LL. Egg hatching under DD occurred for two consecutive days, hatching peak expressing at 06.00 h of normal day condition, with high hatching on day-1 and less on day-2, as against that with LD 12 : 12. Egg hatching under LL also occurred for two consecutive days, hatching peak expressing at 06.00 h, with less hatching on day-1 and more on day-2. However, the only circadian hatching phenomenon of LL was a clear-cut appearance of broadening/widening of hatching activity, just reminding a near damping-out situation. Notably, hatching with black-box condition was its confinement to a single day. From recorded data on egg hatching patterns at farmers’ level, it is amply evident that dial variations in temperature (thermoperiod) and humidity (hygroperiod), in DD/LL conditions are operating as subtle, but definite cues in maintaining the phenomenon of hatching, just like that under LD 12 : 12 photoperiodic condition. This implies that both thermoperiods and hygroperiods, in the absence of light dark signals, are entraining circadian rhythmicity, at least under DD and LL conditions. The present study is just a beginning of such strange observations and need further detailed probe. Data were discussed on the importance of hatching patterns in commercial silkworm egg hatching at farmers’ level.
Keywords: Silkworm, Bombyx mori, CSR2 x CSR4, photoperiod, thermoperiod, hygroperiod, hatching, farmers’ condition.
Title: ON THE EGG HATCHING IN SILKWORM (BOMBYX MORI L.) HYBRID, CSR2 x CSR4 AT FARMERS’ LEVEL, A CASE OF CIRCADIAN ENTRAINMENT WITH THERMOPERIODIC AND HYGROPERIODIC CONDITIONS
Author: Lakshmi, S., Lavanya Latha, K., Satyanarayana, B., Sankar Naik, S.
International Journal of Life Sciences Research
ISSN 2348-313X (Print), ISSN 2348-3148 (online)
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