Abstract
In migratory insects, increasing evidence has demonstrated juvenile hormone (JH) is involved in regulating adult reproduction and flight. Our previous study demonstrated that the switch from migrants to residents in Mythimna separata could be induced by adverse environmental conditions during a sensitive period in adulthood (the first day post-emergence), but the role of JH in this switch is not clear. Here, we found a significantly different pattern of JH titers between migrants and residents, with migrants showing a slower release of JH during adulthood than residents. Application of JH analogue (JHA) in the 1-day-old adults, significantly accelerated adult reproduction and suppressed flight capacity. The pre-oviposition period and period of first oviposition of migrants treated with JHA were significantly shorter, while the total lifetime fecundity and mating percentage increased. The flight capacity and dorso-longitudinal muscle size of the migrants were decreased significantly when treated with JHA. The effect of JHA on reproduction and flight capacity indicate that JH titers during the sensitive period (first day post-emergence) regulates the shift from migrants to residents in M. separata.
Highlights
Insect migration is an important behavioral strategy, which allows species to adapt to environmental variations and seek new habitats[1]
Because most previous studies have focused on the sensitive period during larval development, here we investigated the role of juvenile hormone (JH) in determining migratory potential in the adult stage of M. separata[31,32]
The highest JH I peak appeared on day 1 after adult emergence and decreased significantly on day 2 (F5,12 = 47.19, P < 0.05, Fig. 1A); it steadily increased from day 3 and reached a significantly higher peak on day 5 after emergence (F5,12 = 47.19, P < 0.05)
Summary
Insect migration is an important behavioral strategy, which allows species to adapt to environmental variations and seek new habitats[1]. We previously found that M. separata larvae which experienced environmental conditions conducive to develop into migrants, would shift back to residents if the adults encountered a lack of nectar, low temperature or a long photoperiod conditions on the first day post-emergence[30,31,32]. Such a switch from migrants to residents leads to a significantly curtailed POP and flight capacity. We hypothesized that JH titers in a specific sensitive period regulated the shifting of migrants to residents, and higher JH level accelerated ovarian development and oviposition, and induced the degradation of flight muscle and decline of flight capacity. Differences in JH titers between migrants and residents, and the direct influence of JHA on flight parameters, were studied
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