Differences in the Development of Internal Reproductive Organs, Feeding Amount and Nutrient Storage between Pre-Diapause and Pre-Reproductive Harmonia axyridis Adults

Abstract

Diapause control is one of the successful methods for long-term cold storage of biological control organisms without decreasing their fitness. Sufficient preparation before diapause is essential for successful diapause initiation and maintenance. Harmonia axyridis, an important biocontrol agent in its native place, can enter reproductive diapause for overwintering. However, the key preparatory events before diapause in H. axyridis, such as specific developmental trajectory, timing, and physiological changes, remain unclear. We compared differences in the development of internal reproductive organs, feeding amount and nutrient storage between pre-diapause and pre-reproductive adult H. axyridis which had been reared at 20 °C under a short-day (10L:14D) and long-day (14L:10D) condition, respectively. The results showed that there were obvious morphological differences in internal reproductive organs of diapause and reproductive H. axyridis. The development of internal reproductive organs was suppressed at early adult stage in pre-diapause beetles compared to pre-reproductive beetles. Feeding amount in both pre-diapause and pre-reproductive beetles increased for more than ten days after eclosion. The feeding amount of pre-diapause beetles sharply decreased from the 15th day after eclosion in females and the 14th day after eclosion in males, which implied the initiation of diapause. During the pre-diapause stage, carbohydrates and lipids were mainly accumulated by females, whereas males mainly accumulated carbohydrates. Our results not only provide basic information about the diapause process of pre-diapause stage, but also give tips to better utilization of diapause strategy during mass production and storage of H. axyridis.

Photoperiodic, thermal and trophic responses of a predatory ladybird Cheilomenes propinqua

“…Second, we conclude that our first (dissection) experiment clearly reveals an adult (reproductive) diapause: most of females with non‐developed or poorly developed ovaries have a well‐developed fat body suggesting that poor development of their reproductive system is not a simple direct effect of a deficient of nutrients. It is well known that poorly developed ovaries and well‐developed fat body are the main signs of reproductive diapause in insects (Danks, 1987; Tauber et al., 1986) and, particularly, in ladybirds (Gao et al., 2019; Hodek, 2012; Sakurai et al., 1992), although neurohormonal mechanisms regulating the development of ovaries and the metabolism of lipids may be different (Denlinger et al., 2012). Herewith, the relative increase in weight of C. propinqua females during the experiment, in contrast to some other coccinellids (e.g.…”

“…Examples of the above listed categories of the states of ovaries and fat body are given in Figure 1. These or very similar scales were used for the description of ovaries (Gao et al., 2019; Kono, 1982; Osawa, 2005; Raak‐van den Berg et al., 2012) and fat body (Esquivel, 2011; Musolin, 2012; Sakurai et al., 1992) in earlier studies. Based on the results of the dissection, all females were attributed to four physiological states (Table 1) which were used for further analysis: females with fully developed ovaries were considered as ‘reproductively active’ (non‐diapause); females with moderately developed ovaries were considered as ‘intermediate’; females with not developed or poorly developed ovaries and moderately or fully developed fat body were considered as ‘diapausing’, and, finally, females in which both ovaries and fat body were not or poorly developed were considered as ‘underfed’.…”

“…Examples of the above listed categories of the states of ovaries and fat body are given in Figure 1. These or very similar scales were used for the description of ovaries (Gao et al, 2019;Kono, 1982;Osawa, 2005;Raak-van den Berg et al, 2012) and fat body (Esquivel, 2011;Musolin, 2012;Sakurai et al, 1992) in earlier studies.…”

PacBio Long-Read Sequencing Transcriptome Dataset of Adult Harmonia axyridis Under Diapause Inducing and Reproductive Inducing Photoperiod

“…Previous studies show that H. axyridis enter adult diapause under short-day photoperiod while go for directly development under long-day photoperiod condition (Ongagna and Iperti, 1994 ; Berkvens et al, 2008 ; Zhang et al, 2014 ; Gao et al, 2019 ). More than 90% of beetles entered diapause when the newly emerged adults reared at 20°C under a short-day (10:14 h light: dark) condition for 20 days, whereas those reared under a long-day (14:10 h light: dark) condition at the same temperature became reproductive (Zhang et al, 2014 ; Gao et al, 2019 ). By utilizing the diapause stage of beetle people could get a good way to storage and increase the shelf-life of this biological control agent and obtain a good stage of choice for shipping of commercially viable biological control organisms (Denlinger, 2008 ; Ruan et al, 2012 ; Gao et al, 2019 ).…”

“…More than 90% of beetles entered diapause when the newly emerged adults reared at 20°C under a short-day (10:14 h light: dark) condition for 20 days, whereas those reared under a long-day (14:10 h light: dark) condition at the same temperature became reproductive (Zhang et al, 2014 ; Gao et al, 2019 ). By utilizing the diapause stage of beetle people could get a good way to storage and increase the shelf-life of this biological control agent and obtain a good stage of choice for shipping of commercially viable biological control organisms (Denlinger, 2008 ; Ruan et al, 2012 ; Gao et al, 2019 ). Understand the molecular mechanism of diapause regulation could help people manipulate the diapause of biological control organisms, however this field of H. axyridis remains largely blank.…”