Abstract
Nuptial flights of Crematogaster teranishii Santschi occur in autumn. Queens and possibly larvae pass the first winter without workers in Okayama, Japan. This study examines and tests the hypothesis that C. teranishii queens regulate not only their own diapause, but also that of their larvae. Some queens collected immediately after their nuptial flight in early October were exposed to a low temperature of 10°C for 3 months before transfer to 25°C; these queens started oviposition approximately 8 days after the transfer. Larvae reared by these previously chilled queens pupated synchronously until day 50. Other field-collected queens reared at 25°C without prior chilling reproduced soon after collection. They started oviposition, but the development of their larvae was arrested and pupation occurred late or not at all within the120 day experimental period. The delay in pupation in colonies in which the queens were not previously exposed to low temperature strongly indicates that many larvae are in diapause. Because eggs and larvae were not exposed to low temperatures, they were unable to determine the developmental pathway providing the best response to environmental factors. Results indicate that queens regulate whether their larvae undergo diapause.
Highlights
Diapause, which plays an important role in the seasonal regulation of insect life cycles (Danks, 1987), is an important adaptation to low temperatures in temperate climates and is induced in species-specific developmental stages
Diapause is a dynamic state of low metabolism that is unlike quiescence, an immediate response to adverse environmental conditions that can occur at any stage in a life cycle
For ants in tropical or subtropical regions, colony development and oviposition by the queen occur throughout the year (Kipyatkov, 2001a)
Summary
Diapause, which plays an important role in the seasonal regulation of insect life cycles (Danks, 1987), is an important adaptation to low temperatures in temperate climates and is induced in species-specific developmental stages. Diapause is a dynamic state of low metabolism that is unlike quiescence, an immediate response to adverse environmental conditions that can occur at any stage in a life cycle. Many insects living in temperate areas enter facultative diapause in response to specific environmental cues, such as short day length and low temperature (Tauber et al, 1986; Danks, 1987; Košťál, 2006). In insects with an obligate diapause, development or reproduction is arrested at the same developmental stage in every generation, irrespective of environmental conditions. For ant species at higher latitudes, winter diapause regulates when queens oviposit and larval development (Kipyatkov, 2001a). Repeated induction of reproductive diapause in queen ants occurs irrespective of environmental stimuli, similar to the obligatory diapause in other insects (Kipyatkov, 1993, 2001a)
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