Shin-Ichiro Tachibana

Parental and direct effects of photoperiod and temperature on the induction of larval diapause in the blow fly Lucilia sericata

Abstract.  Lucilia sericata (Meigen) (Diptera: Calliphoridae) shows a facultative diapause in the third, and final larval, instar after the cessation of feeding. The effects of photoperiod and temperature on the induction and duration of diapause were examined in parental (G0) and current (G1) generations. Insects of the G0 generation were reared under four combinations of conditions, involving two photoperiods, LD 16 : 8 and LD 12 : 12 h, and two temperatures, 25 and 20 °C. The G1 generation, present in the eggs laid by these insects, were transferred to 10 combinations of conditions, involving the above two photoperiods and five temperatures, 25, 20, 17.5, 15 and 12.5 °C. In the G1 generation, the time from hatching to cessation of feeding was significantly affected by temperature only, whereas the induction of diapause was influenced by both photoperiod and temperature experienced by the G0 as well as the G1 generation. Short‐day and low‐temperature conditions in the G0 and in the G1 generation had diapause‐inducing effects. In this species, it is likely that, for purposes of acquiring reliable seasonal information, induction of diapause is sensitive to environmental factors both in the G0 and G1 generations. The function of high‐intensity diapause, induced by short‐day conditions and high temperature in the parental generation, appeared to be the prevention of accidental pupariation in warm autumn weather.

Effects of Temperature and Photoperiod on the Termination of Larval Diapause in Lucilia sericata (Diptera: Calliphoridae)

Larvae of the blow fly, Lucilia sericata (Meigen), enter diapause in the third instar after cessation of feeding. The effects of temperature and photoperiod on the termination of diapause were examined. The diapause terminated spontaneously under the diapause-inducing condition of 20°C and LD 12:12, although pupariation was not synchronous. Diapause development proceeded under a low temperature of 7.5°C. Transfer to long-day conditions of LD 16:8 or to a high temperature of 25°C induced prompt and synchronous pupariation. Low temperatures in winter probably play a predominant role in the termination of diapause under natural conditions.

Seasonal prevalence of blowflies and flesh flies in Osaka City

Blowflies (Diptera: Calliphoridae) and flesh flies (Sarcophagidae) were collected using a bait trap in Osaka City between April 1998 and June 1999. Seven species from four Calliphoridae genera and three species from one Sarcophagidae genus were captured. Seasonal fluctuations of captured adults for most blowflies showed a bimodal pattern, having peaks in spring and autumn, whereas all flesh flies were captured between spring and autumn. The sex ratios of captured flies were mostly biased toward females.

Plasmodium falciparum kelch 13: a potential molecular marker for tackling artemisinin-resistant malaria parasites

Although artemisinin combination therapies have been deployed as a first-line treatment for uncomplicated malaria in almost all endemic countries, artemisinin-resistant parasites have emerged and have gradually spread across the Greater Mekong subregions. There is growing concern that the resistant parasites may migrate to or emerge indigenously in sub-Saharan Africa, which might provoke a global increase in malaria-associated morbidity and mortality. Therefore, development of molecular markers that enable identification of artemisinin resistance with high sensitivity is urgently required to combat this issue. In 2014, a potential artemisinin-resistance responsible gene, Plasmodium falciparum kelch13, was discovered. Here, we review the genetic features of P. falciparum kelch13 and discuss its related resistant mechanisms and potential as a molecular marker.

Maternal induction of larval diapause and its sensitive stage in the blow fly Lucilia sericata (Meigen) (Diptera: Calliphoridae)

Lucilia sericata has a facultative diapause in the third larval instar after cessation of feeding. Induction of the diapause is influenced by the photoperiod and temperature conditions experienced by insects in the parental generation as well as those experienced by the larvae themselves. The sensitive stage of the parental generation for induction of diapause was examined using diapause‐averting conditions of 16 h light : 8 h darkness (LD 16:8) at 25°C and diapause‐inducing conditions of LD 12:12 at 20°C. The incidence of diapause in the progeny was predominantly determined by the conditions experienced by the parents in the adult stage. Moreover, the results of reciprocal crosses showed that only the mothers experience is involved in the induction of diapause in the progeny.

Regulation of gonad development and respiratory metabolism associated with food availability and reproductive diapause in the rice bug Leptocorisa chinensis.

Food has an influence on many life history traits related to dormancy in insects. In our previous study with the rice bug Leptocorisa chinensis (Dallas) (Hemiptera: Alydidae), diapausing females transferred to conditions physically favorable for promoting the gonad development required food intake to resume gonad development, whereas males did not. These differences in response to food between males and females lead to two questions: (1) Was diapause in the starved females completed? (2) Were the starved males that resumed gonad development at the same physiological status as fed males? We tested these questions with two physiological indicators: gonad status and respiratory rate. Results indicate that starved females are able to complete diapause, but show depressed respiration relative to well-fed insects in diapause. Similar to females, starved males that resumed postdiapause gonad development also had depressed respiratory rate, and hence physiological status is presumed to be different between starved and fed individuals. In this study, it was also found that the photoperiodic signal is storable, whereas the food signal acts directly. The adaptive significance of regulation of gonad development and respiratory metabolism in relation to phenology of suitable host plant and reproductive strategy is discussed in both sexes.

Transcriptome analysis of the brain under diapause and nondiapause conditions in the blowfly Protophormia terraenovae

The blow fly Protophormia terraenovae responds to photoperiod and temperature to control reproductive diapause. Differentially expressed genes (DEGs) in the brain are investigated under diapause‐inducing and diapause‐averting conditions in search of potential genes for diapause induction. Total RNA is extracted from female brains 1–2.5 days after adult emergence under an LD 18 : 6 h photocycle at 25 °C as nondiapause samples and 3, 3.5, 7 and 7.5 days after adult emergence under an LD 12 : 12 h photocycle at 20 °C as diapause samples. From our transcriptome analysis, 626 350 654 reads are assembled into 126 231 contigs, from which 46 844 contigs (37.1% of the total) are annotated as protein‐coding genes. Among them, the expression levels in 549 contigs are specifically up‐regulated under diapause‐inducing (44.1%) or diapause‐averting (55.9%) conditions. Using quantitative real‐time reverse transcriptase‐polymerase chain reaction analysis, higher expression levels under diapause‐inducing conditions are found in a contig encoding angiotensin‐converting enzyme (ACE). Expression levels of the contig significantly increase 3 days after changing the photoperiod to diapause‐inducing short days. Rabbit antisera against 17 amino acid peptides included in P. terraenovae‐ACE stain one pair of cells lateral to the oesophageal foramen. These results suggest that the expression of a small number of genes is associated with the regulation of diapause in response to photoperiod and temperature, and ACE in the immunoreactive cells might respond to short days, which is why it is involved in diapause induction.