Photoperiod induced developmental effects on silkmoth,Bombyx mori

Bombyx mori is most common silkmoth used for the commercial production of the silk. The different environmental conditions may affect development of silkmoth and hence the output of silkworm. Present study investigated effects of different photoperiodic conditions on the development of silkmoth. Three experiments were performed on newly hatched larvae. In experiment1, larvae were divided into three groups; group 1, 8L:16D (8 h light and 16 h dark), group 2, 12L:12D (12 h light and 12 h dark) and group 3, 16L:8D (16 h light and 8 h dark). In experiment 2, larvae were exposed to either continuous light or continuous dark. In experiment 3, larvae were divided into three groups. Each group received light of similar duration (16L:8D) and intensity (1.1 ± 0.1 PAR) but of different wavelengths; i.e. long wavelength red light (640 nm), short wavelength blue light (450 nm) and white light. Larvae were fed on young mulberry (Morus alba) leaves. Temperature and humidity were maintained at 26 (±2) °C and 75 (±5)%, respectively, throughout the study. Observations on change in body length of larvae were made on every alternate day. We also calculated the shell ratio, time taken in cocoon formation and emergence. Results from experiment show that the larvae underwent significant change in body length but with faster growth rate under 12L:12D photoperiod in comparison to 8L:16D and 16L:8D. Time taken in cocoon formation and hatching was significantly less, while shell ratio was significantly higher in 12L:12D in comparison to other groups. We did not observe much effect of monochromatic light on the development of silkmoth.     

Effect of urbanization on daily behavior and seasonal functions in vertebrates

Abstract

Most of the organisms are seasonal and live in a periodic environment and rely on external cues to optimally time their annual life history stages. The most predictable environmental cue which organisms use to time reproduction is the photoperiod, but food, temperature, and humidity may play role as a crucial factors. Urbanization is greatly increasing phenomenon and leads to change in landscape and habitat destruction for wildlife and brings extra hours of light at night (LAN), altering the natural signal of light and darkness, hence the temperature and availability of food. This artificial LAN has been implemented to affect behavior, endocrinology, and reproductive physiology and to advance seasonal reproduction in birds. Here, we review the literature available on the effects of urbanization on diverse processes of organisms with particular emphasis on avian system. We consider further research with long-term data-sets on phenological and physiological parameters from diverse group of organisms and diverse habitat is essential for better understanding of impact of global climate change on the biodiversity.