Band-legged Ground Cricket Research Articles

No evidence for the involvement of juvenile hormone III and 20-hydroxyecdysone in maternal decisions for embryonic diapause and diapause entry in the band-legged ground cricket Dianemobius nigrofasciatus (Orthoptera: Trigonidiidae)

No evidence for the involvement of juvenile hormone III and 20-hydroxyecdysone in maternal decisions for embryonic diapause and diapause entry in the band-legged ground cricket Dianemobius nigrofasciatus (Orthoptera: Trigonidiidae)

Complete mitochondrial genome sequences of two ground crickets, Dianemobius fascipes nigrofasciatus and Polionemobius taprobanensis (Orthoptera: Grylloidea: trigonidiidae)

The authors sequenced the complete mitochondrial (mt) genomes of the band-legged ground cricket (Dianemobius fascipes nigrofasciatus Matsumura, 1904) and a temperate form of the lawn ground cricket (Polionemobius taprobanensis Walker, 1869), collected in Japan. The length of the mt genome sequences was 15,354 bp in D. fascipes nigrofasciatus and 16,063 bp in P. taprobanensis. Annotation of the mt genome sequences revealed 13 protein-coding genes, two rRNA genes, and 22 tRNA genes. The orientation of the genes was the same as in other Grylloidea species, and the order was the same as in other Trigonidiidae species. In our phylogenetic analysis, D. fascipes nigrofasciatus formed a clade with D. fascipes collected in China, and the temperate form of P. taprobanensis formed a clade with P. taprobanensis collected in China. Comparison of the numbers of positions with different amino acid residues encoded by the protein-coding genes implied the separate species status of each member of each of the two pairs of ground crickets. The mt genome sequences of D. fascipes nigrofasciatus and P. taprobanensis will contribute to phylogenetic and taxonomic studies of the Trigonidiidae.

The circadian clock gene (Clock) regulates photoperiodic time measurement and its downstream process determining maternal induction of embryonic diapause in a cricket

In response to short days in autumn, most temperate multivoltine insects enter diapause, a state in which development or reproduction is suppressed or arrested, which serves to coordinate their development and physiology (or that of offspring) with annual changes in the environment (i.e. photoperiodism). This response is mediated by a measurement of time based on photoperiod (photoperiodic time measurement), which is thought to be regulated by a circadian clock. However, some studies also demonstrate the involvement of the circadian clock in an output process that generates phenotypes associated with diapause. To gain further insight into this, we silenced the Clock (Clk) gene, the main regulator of the circadian clock, in the band-legged ground cricket Dianemobius nigrofasciatus (Orthoptera: Trigonidiidae). Silencing the Clk gene using RNA interference (Clk RNAi) in female crickets resulted in abnormal circadian rhythms under constant darkness and light-dark conditions, thereby indicating the central role of this gene in the circadian clock mechanism. Clk RNAi females exhibited long-day oviposition behaviour, even when reared under short-day conditions, thereby indicating the involvement of Clk in photoperiodic time measurement. In addition, Clk RNAi females immediately laid non-diapause-type eggs, which was not recorded in control females under either short-day or long-day conditions and cannot be explained in terms of dysfunction of photoperiodic time measurement. Accordingly, we speculate that Clk could also be involved in a downstream process that results in the laying of diapause-type eggs.

Cell cycle regulator, small silencing RNA, and segmentation patterning gene expression in relation to embryonic diapause in the band-legged ground cricket

Insects enter diapause to synchronize their life cycle with biotic and abiotic conditions favorable for their development, reproduction, and survival. Adult females of the band-legged ground cricket Dianemobius nigrofasciatus (Orthoptera, Glyllidae) respond to environmental factors in autumn and lay diapause-destined eggs. The eggs arrest their development and enter diapause at a very early embryonic stage, specifically the cellular blastoderm. To elucidate the physiological mechanisms underlying this very early stage programmed developmental arrest, we investigated the cell division cycle as well as the expression of cell cycle regulators, small silencing RNAs, and segment patterning genes. The diapause embryo arrests its cell cycle predominantly at the G0/G1 phase. The proportion of cells in the S phase of the cell cycle abruptly decreased at the time of developmental arrest, but further changes of the G0/G1 and G2/M were later observed. Thus, cell cycle arrest in the diapause embryo is not an immediate event, but it takes longer to reach the steady state. We further elucidated molecular events possibly involved in diapause preparation and entry. Downregulation of Proliferating cellular antigen (PCNA; a cell cycle regulator), caudal and pumilio (cad and pum; early segmentation genes) as well as P-element induced wimpy testis (piwi) (a small silencing RNA) prior to the onset of developmental arrest was notable. The downregulation of PCNA, cad and pum continued even after entry into developmental arrest. In contrast to upregulation in non-diapause eggs, Cyclin D (another cell cycle regulator) and hunchback, Krüppel, and runt (gap and pair-rule genes) were downregulated in diapause eggs. These molecular events may contribute to embryonic diapause of D. nigrofasciatus.

Effect of hind-limb autotomy on calling and hiding behavior in the band-legged ground cricket, Dianemobius nigrofasciatus

Crickets can escape death by autotomizing a limb when attacked by predators. In contrast with this benefit, autotomized individuals pay an immediate cost of escape speed and mating ability. Therefore, an adaptive response compensating for the cost of autotomy might be advantageous in autotomized individuals. In this study, we examined whether autotomy induced behavioral plasticity compensating for future cost in the band-legged ground cricket Dianemobius nigrofasciatus. Behavioral traits of D. nigrofasciatus were compared between autotomized and intact individuals. Frequency of calling behavior was higher for autotomized males. This behavior might be advantageous because females prefer actively calling males. In contrast with calling behavior, the frequencies of hiding behavior did not vary between autotomized and intact crickets, irrespective of sex. It might be disadvantageous for both sexes to hide, because females could not find hiding males and hiding females could not find males. These results indicated autotomy-induced behavioral plasticity that might reduce the cost of autotomy.

Autotomy-induced life history plasticity in band-legged ground cricketDianemobius nigrofasciatus

Crickets can autotomize their limbs when attacked by predators. This enables them to escape death, but imposes a short-term cost on their escape speed and a long-term cost on their future mating ability. Therefore, adaptive response compensated for the cost of autotomy might be advantageous for autotomized individuals. In the present study, we examined whether autotomy induced life history plasticities compensating for the future cost in the band-legged ground cricket Dianemobius nigrofasciatus. Life history traits of D. nigrofasciatus were compared between autotomized and intact individuals. The developmental time and head width of the individuals that were autotomized as fourth instar nymphs were significantly shorter and smaller, respectively, than those of intact individuals. However, the adult longevity, number of eggs laid and oviposition schedule did not vary between autotomized and intact individuals. In addition, there was no difference between individuals autotomized at the fourth instar and adult stages in these three traits. Early maturation in the autotomized individuals might be advantageous through reducing the risk of predation owing to the shorter period in nymphal stages. The cost of small body size in the autotomized females might not be so great because of no significant difference in fecundity between autotomized and intact individuals. However, the cost of small body size was unclear in the autotomized males because in general larger males were preferred by females. These results indicated autotomy-induced life history that might reduce the cost of autotomy.

Early embryonic development and diapause stage in the band-legged ground cricket Dianemobius nigrofasciatus

The band-legged ground cricket Dianemobius nigrofasciatus enters diapause at an early embryonic stage when adults are reared under short-day conditions or the eggs are exposed to a low temperature. We examined the morphological features of the embryo during early development and determined the exact stage of entry into diapause. In non-diapause eggs, no periplasmic space was observed in the surface region and a small number of nuclei surrounded by cytoplasm (energids) were found among the yolk granules and lipid droplets 12 h after egg laying (AEL) at 25 degrees C. The energids sparsely but evenly populated the surface region at 40 h AEL, but there were some gaps between these energids. A continuous thin layer of nuclei with cytoplasm had completely covered the egg surface at 56 h AEL, suggesting that the blastoderm is formed between 40 and 56 h AEL. At 72 h AEL, we found a germ band at the posterior pole. Electron microscopy revealed clear cell membranes at 40 h AEL. Staining with rhodamine-dextran dye demonstrated that the cell membrane is formed when the nuclei appear on the egg surface at 12-24 h AEL. These results indicate that cellularization occurs before blastoderm formation. In diapause eggs, neither the embryonic rudiment nor germ band was formed, but a continuous layer of cells covered the egg surface. It is concluded that D. nigrofasciatus enters diapause at the cellular blastoderm.

Localization of the Photoreceptor and Pacemaker for the Circadian Activity Rhythm in the Band-Legged Ground Cricket, Dianemobius nigrofasciatus

Anatomical locations of the photoreceptor and circadian pacemaker for the locomotor activity rhythm were investigated by removal of the external photoreceptors, the compound eyes and ocelli, or the optic lobes in the adult cricket, Dianemobius nigrofasciatus (Orthoptera: Gryllidae). The activity rhythm of intact crickets freeran under DD with a freerunning period (τ) of 24.6 ± 1.0 h (mean ± SD) and entrained to light-dark cycles of LD 13:13 and LD 12:12. When both compound eyes were removed, some crickets entrained both to LD 13:13 and LD 12:12. Some of the others entrained only to LD 12:12 or showed a complex pattern of the activity. When both compound eyes and all ocelli were removed, some crickets still entrained both to LD 13:13 and LD 12:12. The activity pattern of the crickets receiving a sham operation or unilateral removal of the compound eye was not different from that in the intact crickets. Bilateral removal of the optic lobes caused arrhythmicity both under LD 13:13 and DD, although the activity rhythm in crickets of which the optic lobe was unilaterally removed entrained to LD 13:13 and freeran under DD. These results suggest that D. nigrofasciatus possesses its circadian pacemaker in the optic lobe, and uses both extraretinal photoreceptors and compound eyes for its entrainment.

Seasonal Changes in the Incidence of Embryonic Diapause in the Band-Legged Ground Cricket, Dianemobius nigrofasciatus

Abstract The incidence of embryonic diapause in the band-legged ground cricket, Dianemobius nigrofasciatus was examined in regard to egg production by individual females both in the laboratory and in the field in Osaka, Japan. (1) Females were classified into three types: diapause egg-producers (laid only diapause eggs), nondiapause egg-producers (laid only nondiapause eggs) and mixed egg-producers (laid both diapause and nondiapause eggs). (2) The longer the photophase, the smaller was the incidence of diapause egg-producers, and the larger was that of the nondiapause egg- and mixed egg-producers. The critical day-length was between 13 and 14 hr. (3) The longer the photophase, the smaller was the incidence of diapause eggs laid by mixed egg-producers. (4) In the field, both nondiapause egg-producers and mixed egg-producers were observed from June to August. In September and October, most of the females were diapause egg-producers. The present findings revealed that adults of the overwintered generation o...

Effects of compound eye-removal on the photoperiodic response of the band-legged ground cricket, Pteronemobius nigrofasciatus

The band-legged ground cricket Pteronemobius nigrofasciatus shows a clear photoperiodic response at 25°C with respect to the control of the induction of embryonic diapause. When crickets were reared under a short-day (LD 12 ∶ 12) photoperiod and then transferred to a long-day (LD 16 ∶ 8) photoperiod upon adult emergence, the adults mainly laid nondiapause eggs. However, adults maintained continuously under short-day conditions laid dispause eggs. When compound eyes were bilaterally removed after adult emergence, the crickets mainly laid nondiapause eggs, irrespective of the photoperiod. Thus, the adults completely lost their sensitivity to photoperiod after bilateral removal of their compound eyes. Unilateral removal of the compound eye also affected the crickets under a short-day photoperiod, and the incidence of diapause eggs was intermediate between that laid by intact adults and that laid by adults after the bilateral removal of compound eyes. The incidence of diapause eggs in sham-operated crickets was not significantly different from that in intact crickets under both sets of photoperiodic conditions. These results show that P. nigrofasciatus perceives the photoperiod through its compound eyes.

Tropical, subtropical and temperate life cycles in ground crickets

The band-legged ground cricket group comprises a pair of very closely related species; Dianemobius fascipes occurs widely over tropical and subtropical regions of Southeast Asia, while D. nigrofasciatus is restricted to temperate regions. A similar situation is found in the lawn ground cricket group; the tropical/subtropical species D. taprobanensis is replaced by D. mikado in temperate regions. In both southern species, tropical strains were almost homodynamic, but they produced a few delayed eggs independently of photoperiod and a variable proportion of macropters in response to photoperiod; subtropical strains showed clearer responses. Both northern species controlled egg diapause, nymphal development and wing form by various photoperiodic responses. The two species groups showed parallel geographical profiles of size variation, and the adults and eggs were smaller in the southern than in the northern species. In the absence of strong climatic selection for larger growth rate, size increase in tropical regions would be counteracted by predation pressure. The optimal adult size thus seems to be smaller in tropical than in temperate regions, being determined by the geographically variable balance between counteracting selecting forces.

CLIMATIC ADAPTATION AND PHOTOPERIODIC RESPONSE IN THE BAND-LEGGED GROUND CRICKET.

EvolutionVolume 26, Issue 4 p. 587-600 ArticleFree Access CLIMATIC ADAPTATION AND PHOTOPERIODIC RESPONSE IN THE BAND-LEGGED GROUND CRICKET† Sinzo Masaki, Sinzo Masaki Laboratory of Entomology, Faculty of Agriculture, Hirosaki University, Hirosaki 036, JapanSearch for more papers by this author Sinzo Masaki, Sinzo Masaki Laboratory of Entomology, Faculty of Agriculture, Hirosaki University, Hirosaki 036, JapanSearch for more papers by this author First published: December 1972 https://doi.org/10.1111/j.1558-5646.1972.tb01966.xCitations: 82 †Contribution number 53 from the Laboratory of Entomology, Hirosaki University. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume26, Issue4December 1972Pages 587-600 ReferencesRelatedInformation

Climatic Adaptation and Photoperiodic Response in the Band-Legged Ground Cricket

Climatic Adaptation and Photoperiodic Response in the Band-Legged Ground Cricket