Abstract
Activity rhythms in 24 h light-dark cycles, constant darkness, and constant light conditions were analyzed in four different Nasonia species for each sex separately. Besides similarities, clear differences are evident among and within Nasonia species as well as between sexes. In all species, activity in a light-dark cycle is concentrated in the photophase, typical for diurnal organisms. Contrary to most diurnal insect species so far studied, Nasonia follows Aschoff's rule by displaying long (>24 h) internal rhythms in constant darkness but short (<24 h) in constant light. In constant light, N. vitripennis males display robust circadian activity rhythms, whereas females are usually arrhythmic. In contrast to other Nasonia species, N. longicornis males display anticipatory activity, i.e. activity shortly before light-on in a light-dark cycle. As expected, N. oneida shows activity patterns similar to those of N. giraulti but with important differences in key circadian parameters. Differences in circadian activity patterns and parameters between species may reflect synchronization of specific life-history traits to environmental conditions. Scheduling mating or dispersion to a specific time of the day could be a strategy to avoid interspecific hybridization in Nasonia species that live in sympatry.
Highlights
IntroductionExamples are locomotor activity [1], hatching [2], eclosion [3], emergence from host puparia [4,5], and mating [6,7]
Many traits in insects are subject to circadian oscillation
The following Nasonia strains were used: Nasonia giraulti RV2x(u) (Virginia, USA, 1987), NGDS, VA2TET (Virginia, USA, 2007, Tetracycline treated), PA233F (Pennsylvania, USA, 1989), VA1TET (Virginia, USA, 2007, Tetracycline treated); Nasonia longicornis IV7 (Utah, USA), IDB418(u) (Idaho, USA), MN8510 (Minnesota, USA), UTB316.16 (Utah, USA, 1990); N. oneida NY1136 (NY, USA, 2005); Nasonia vitripennis AsymC (Leiden, NL, 1971, cured from Wolbachia bacteria), HV3 (Hoge Veluwe, NL, 2006), Ita2 (Piedmont, Italy, 2006), LabII (Leiden, NL), Sal29 (New York, USA, 2007)
Summary
Examples are locomotor activity [1], hatching [2], eclosion [3], emergence from host puparia [4,5], and mating [6,7] Many of these circadian traits are expected to have an adaptive significance [8]. Woelfle et al [9] found that cyanobacteria strains with a functioning biological clock defeat strains with non-functioning clocks This advantage is stronger when the internal rhythm is similar to the external light-dark cycle. Considering this potential selective advantage, differences in circadian traits are expected within species, between sexes or among populations of the same species. Differences observed in circadian locomotor activity between Eupelmus species are thought to reduce competition for the same resources [11]
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