Opsins are involved in nymphal photoperiodic responses in the cricket Modicogryllus siamensis

The cricket Modicogryllus siamensis Chopard shows photoperiod‐dependent changes in the duration of nymphal development: nymphs become adult within 60 days after hatching, undergoing seven moults under long‐day conditions, whereas, under short‐day conditions, nymphal development takes much longer (approximately 180 days) with an increased number of moults. Because removal of the compound eyes alters this photoperiodic response, the eyes may be involved in light detection during the photoperiodic response. The role of opsins, expressed in the compound eye, is examined in the present study with reference to the photoperiodic response. Molecular cloning identifies cDNAs of three opsins, opsin‐Ultra Violet (Ms'op‐UV), opsin‐Blue (Ms'op‐B) and opsin‐Long Wave (Ms'op‐LW), and in situ hybridization reveals that the opsin genes are expressed in specific regions of the compound eye in a gene‐specific manner. RNA interference (RNAi) technology using the opsin genes results in a partial disruption in the long‐day responses; most of the treated crickets showed eight or more moults and up to 23.5% show a prolonged nymphal period that is typical of short‐day responses. Under short‐day conditions, op‐UV RNAi crickets show earlier adult development, whereas no distinct alterations are observed in op‐B and op‐LW RNAi insects. The results suggest that the opsin genes may play differential roles in the photoperiodic response in the cricket and that the results can be at least partially explained in terms of the external coincidence model of photoperiodic time measurement.     

Photoperiodic response in the subtropical and warm‐temperate zone populations of the southern green stink bug Nezara viridula: why does it not fit the common latitudinal trend?

The photoperiodic response of diapause induction is studied in females of five subtropical and warm‐temperate zone populations of Nezara viridula (L.) (Heteroptera: Pentatomidae) in Japan (26.4–34.7°N; 127.4–135.7°E). Laboratory tests at 25 °C demonstrate that both warm‐temperate and subtropical populations have pronounced photoperiodic responses of adult diapause induction. Under short‐day conditions (LD 10 : 14 h), 73–100% of females enter diapause, whereas, under long‐day conditions (LD 15 : 9 h), 87–100% of females are nondiapause and reproduce. When the critical photoperiod for diapause induction is plotted against the latitude of origin of each population, the data points do not show the expected tendency of increasing critical photoperiod northwards but, instead, vary between 12 h 15 min and 13 h 30 min. It is suggested that adults from different populations of such a highly migratory species move often among subtropical islands (by themselves or being assisted by typhoons), thus constantly destabilizing the photoperiodic responses. Although important for general synchronization of seasonal development in the tropics and subtropics, winter diapause might not be so critical for survival in mild winters in these zones. Such circumstances might make the selective pressure over the photoperiodic response less severe in the tropics and subtropics than in the temperate zone. It is suggested that the current climate warming might contribute to this situation as well by promoting polewards migrations and lessening the selective pressure of overwintering conditions.     

Effect of high temperature pre-treatment on elongation of the mesocotyl of rice seedlings I. Cell multiplication in the mesocotyl

Mesocotyl elongation in paddy rice seedlings of the japonicatype was markedly stimulated by high temperature pre-treatmentof seeds. Examination of the number of parenchyma cells perone cell layer in longitudinal sections of mesocotyl revealedthat stimulation may be mainly caused by cell multiplication. (Received February 24, 1970; )     

MOUSE MUSCLE CELL DIFFERENTIATION IN CLONAL CULTURE

Clonal culture of muscle cells from thigh muscles of the term fetus of the mouse was undertaken. Myoblasts were spherical or spindle-shaped, and proliferated exponentially until day 4 in culture. The generation time of the muscle cells from 2 to 4 days' culture was 9.1 to 13.4 hr. The fusion of myoblasts began on day 4 in culture; many myotubes had been formed by day 6 and spontaneous contraction was observed on day 7. Clonal efficiency was 30%, and the proportion of muscle colonies in all the colonies was 72%.     

Dissecting insect responses to climate warming: overwintering and post‐diapause performance in the southern green stink bug,Nezara viridula,under simulated climate‐change conditions

The effect of simulated climate change on overwintering and post‐diapause reproductive performance is studied in Nezara viridula (L.) (Heteroptera: Pentatomidae) close to the species' northern range limit in Japan. Insects are reared from October to June under quasi‐natural (i.e. ambient outdoor) conditions and in a transparent incubator, in which climate warming is simulated by adding 2.5°C to the ambient temperatures. Despite the earlier assumption that females of N. viridula overwinter in diapause, whereas males do so in quiescence, regular dissections show that the two sexes overwinter in a state of true diapause. During winter, both sexes are dark‐coloured and have undeveloped reproductive organs. Resumption of development does not start until late March. During winter, the effect of simulated warming on the dynamics and timing of physiological processes appears to be limited. However, the warming significantly enhances winter survival (from 27–31% to 47–70%), which is a key factor in range expansion of N. viridula. In spring, the effect of simulated warming is complex. It advances the post‐diapause colour change and transition from dormancy to reproduction. The earlier resumption of development is more pronounced in females: in April, significantly more females are already in a reproductive state under the simulated warming than under quasi‐natural conditions. In males, the tendency is similar, although the difference is not significant. Warming significantly enhances spring survival and percentage of copulating adults, although not the percentage of ovipositing females and fecundity. The results suggest that, under the expected climate‐warming conditions, N. viridula will likely benefit mostly as a result of increased winter and spring survival and advanced post‐diapause reproduction. Further warming is likely to allow more adults to survive the critical cold season and contribute (both numerically and by increasing heterogeneity) to the post‐overwintering population growth, thus promoting the establishment of this species in newly‐colonized areas.     

Effect of Extracellular Ions on Motility and Cell Entry in Toxoplasma gondii

Toxoplasma gondii tachyzoites were quiescent in mouse peritoneal fluid or in K₂SO₄ buffer at pH 8.2. They became consistently motile when K⁺ was replaced by other monovalent or divalent cations at a constant pH (pH = 8.2). They also became motile when Cl^? was substituted for SO₄^2-. Nitrate or SCN^?, can also be substituted for Cl^? to a certain extent. Tachyzoites showed independent movement for more than 15 min in KCl, and for about 5 min in the other buffers at pH 8.2 after which they were exhausted and stopped. These tachyzoites could not then be further stimulated to motility by renewal of the suspension buffer. Infection of monolayer cells was demonstrated only with parasites which were motile during inoculation. The highest infectivity was thus obtained either with freshly collected tachyzoites or with those preincubated in K₂SO₄ buffer for 30 min at 37° C at alkaline pH and thus not yet exhausted for motility. Approximately 34 to 38% of these latter organisms were seen to enter cells when they were inoculated into cultures immediately after being resuspended in MEM for 30 min at 37° C. Conversely, those whose motility had been exhausted by the preincubation in buffers other than K₂SO₄, pH 8.2 could not enter monolayer cells. Additionally, parasites were unable to enter cells when inoculated into cultures in K₂SO₄ buffer at alkaline pH; instead they remained quiescent on the surface of the monolayer cells, suggesting that Toxoplasma enters the host cells by active invasion.     

IMMUNOCHEMICAL STUDY ON THE SPECIES SPECIFICITY OF SPERM-BINDING PROTEIN FROM THE SURFACE OF THE SEA URCHIN EGG*

Immunological species specificity of sperm-binding protein from eggs of the 4 sea urchin species, Hemicentrotus pulcherrimus, Pseudocentrotus depressus, Anthocidaris crassispina and Temnopleurus toreumaticus, was examined by means of double immuno-diffusion technique in agar. Ca-soluble fraction of sperm-binding protein which is considered to be responsible for initial sperm-egg bonding at fertilization, has species-specific antigenic component. Correlations in antigenic constituents among the 4 species are described.