%0 Journal Article
%T Discrete Modes of Life Cycle in Velarifictorus micado Species Complex (Orthoptera: Gryllidae)
%A Zhuqing He
%A Makio Takeda
%J ISRN Entomology
%D 2013
%R 10.1155/2013/851581
%X Different modes of climatic adaptation often lead to a split in reproductive cohesion and stimulate speciation between populations with different patterns of life cycle. We here examined egg development and photoperiodic adaptations in the nymphal development of Velarifictorus micado. We defined fast hatching populations as nymphal diapause and slow hatching populations as egg diapause. The nymphs were reared under two photoperiods, LD 16£¿:£¿8 and LD 12£¿:£¿12 at 27.5¡ãC, and the mean days of nymphal development were compared. The results indicate that the nymphal diapause populations showed slower nymphal development under LD 12£¿:£¿12 than under LD 16£¿:£¿8, and this retardation increased with the increase of original latitude. The egg diapause populations showed slower nymphal development under LD 16£¿:£¿8 than under LD 12£¿:£¿12. These features help synchronizing their overwintering stages. Gene flow from the opposite forms may disturb this synchronization mechanism, and therefore natural selection should favor displacement of the two forms. This could be an incipient climatic isolation mechanism of reproductive stage. 1. Introduction Crickets are omnivorous feeders widely distributed in low and wetland habitats between 57¡ã north and south latitudes [1]. Their life cycles can be divided into two basic types£¿:£¿ one without seasonality and the other with it [2]. Crickets of the first type continue producing new generations throughout the year, so they lack synchrony of generations. Crickets of the second type usually have a unique and regular life cycle, where climate exerts synchronizing effects [1, 3]. Crickets in temperate zones with different life cycle show different photoperiod responses. Masaki researched the photoperiodic response of Japanese crickets systematically [4¨C10] and he defined three types of photoperiodic response£¿:£¿ long-day type, short-day type, and intermediate-day type [11] (other complex models also exist [12]). Crickets belonging to long-day type develop fast and emerge synchronously under long photoperiod (LD 16£¿:£¿8, 16 hours day time and 8 hours night time, the same below) and they are bivoltine or multivoltine with nymph diapause, such as Teleogryllus emma (Ohmachi and Matsuura, 1951) and T. infernalis (Saussure, 1877) [10, 13, 14]. Crickets belonging to short-day type develop fast under short photoperiod (LD 12£¿:£¿12) and are univoltine with egg diapause, such as Modicogryllus siamensis Chopard, 1961 [5¨C7]. Intermediate-day type crickets include Dianemobius nigrofasciatus (Matsumura, 1904) and Polionemobius taprobanensis (Walker, 1869)
%U http://www.hindawi.com/journals/isrn.entomology/2013/851581/