We studied the eclosion rhythm of the marine midge Pontomyia oceana in southern Taiwan. The lunar/semilunr rhythm is known to be endogenous since it persists under continous light or dark conditions. In this study, we discovered that the period of the eclosion rhythm is about 15 days, although the midges have to spend an additional 15 days in the beginning of their lives before entering the eclosion rhythm. The period of the semilunrar eclosion rhythm is controlled by counting cycles of endogenous circadian rhythms which in term was entrainable by external light-dark (LD) cycles. We demonstrated this by modifying the period of LD cycles in different parts of their life histories with or without the entraining factor and then observing the ecolsion times in the laboratory. Night light can entrain the semilunar eclosion rhythm; we discovered that the cue and the eclosion are in the same phase of the semilunar rhythm but with a full cycle of shift. Temperature compensation in period control is demonstrated in this species. Q10 values close to 1 is found between 24 to 30¢XC in the laboratory.

Abstract The effects of temperature on daily eclosion time and monthly eclosion days of the marine midge Pontomyia oceana were investigated. We changed temperature at different times on the eclosion day. The results show that P. oceana has started related metabolic processes at sunrise which lead to eclosion after sunset. Daily temperature cycles do not have concentrating effect on daily eclosion time. Two peaks of eclosion dates occurred from the same batch of fertilized eggs in the laboratory without cyclic environmental factors. High culturing temperature results in short interval (duration) between fertilization and eclosion, whereas more days are required at low temperature. The culturing temperature has a significant influence upon the numbers of P. oceana occurring in different eclosion peaks. High first/second peak ratio occurred at high temperatures whereas relatively more eclosed at the second peak at low temperature. The eclosion dates of offspring are not related to their parents with regard to the 2 peaks. There was an corresponding shift in eclosion days in eggs fertilized 2 days apart. It suggested that circasemilunar eclosion times were not caused by cues in the laboratory.

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abstract: The molt from pupae to adult stage, called eclosion, occurs at specific times of the day in many holometabolous insects. These events are not well studied within Lepidopteran species. It was hypothesized that the eclosion timing in a species may be shaped by strong selective pressures, such as sexual selection in the context of male-male competition. The daily timing of eclosion was measured for six species of nymphalid butterflies. This was done by rearing individuals to pupation, placing the pupa in a greenhouse, and video recording eclosion to obtain the time of day at which it occurred. Four species exhibited clustered eclosion distributions that were concentrated to within 201 minutes after sunrise and were significantly different from one another. The other two species exhibited eclosion times that were non-clustered. There were no differences between sexes within species. The data support a relationship between the timing of eclosion each day and the timing of mating activities, but other as of yet undetermined selective pressures may also influence eclosion timing. / Dissertation/Thesis / Masters Thesis Biology 2017

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Circadian rhythms dictate the timing of both once-in-a-lifetime adult emergence (eclosion) and daily locomotor activity rhythms in the flesh fly S. crassipalpis. Light cycles are considered the primary environmental time cue (zeitgeber), but the life history of S. crassipalpis suggests that temperature cycles (thermocycles) may also play a key role. This work evaluates the efficacy of thermocycling as a zeitgeber in S. crassipalpis. We found that shifting both light and temperature cycles of sufficient amplitude affect the phasing of eclosion and locomotor activity, but result in different patterns. Additional experiments suggest greater thermocycle sensitivity during the late metamorphic period and that thermocycling reduces variance in eclosion times. Taken together, these findings suggest that temperature cycles can be used by S. crassipalpis to time eclosion and adult locomotor activity, and that S. crassipalpis may be physiologically primed to use thermocycle information during metamorphosis.