Physiological and molecular mechanisms underlying photoperiodism in the spider mite: comparisons with insects.
Photoperiodism is an adaptive, seasonal timing system that enables organisms to coordinate their development and physiology to annual changes in the environment using day length (photoperiod) as a cue. This review summarizes our knowledge of the physiological mechanisms underlying photoperiodism in spider mites. In particular, the two-spotted spider mite Tetranychus urticae is focussed, which has long been used as a model species for studying photoperiodism. Photoperiodism is established by several physiological modules, such as the photoreceptor, photoperiodic time measurement system, counter system, and endocrine effector. It is now clear that retinal photoreception through the ocelli is indispensable for the function of photoperiodism, at least in T. urticae. Visual pigment, which comprised opsin protein and a vitamin A-based pigment, is involved in photoreception. The physiological basis of the photoperiodic time measurement system is still under debate, and we have controversial evidence for the hourglass-based time measurement and the oscillator-based time measurement. Less attention has been centred on the counter system in insects and mites. Mite reproduction is possibly regulated by the ecdysteroid, ponasterone A. Prior physiological knowledge has laid the foundation for the next steps essential for the elucidation of the molecular mechanisms driving photoperiodism.
['Goto|Shin G|SG|']
D000818:Animals D001683:Biological Clocks D002940:Circadian Rhythm D000074767:Diapause D026461:Ecdysteroids D007313:Insecta D017440:Photoperiod D017956:Photoreceptor Cells, Invertebrate D012098:Reproduction D040102:Tetranychidae
Photoperiodism Spider mite Tetranychus urticae Diapause Photoperiodic response