{"title":"Relative humidity and maintenance of p50 silkworms reared on artificial diet","authors":"Kodai Yuri, K. Sahara","doi":"10.11416/JIBS.86.2_043","DOIUrl":null,"url":null,"abstract":"Silk spinners (e.g. spiders, moths, mites, mayflies) and cocoon makers (e.g. spiders, moths, bees, flies) have repeatedly evolved in arthropods, and human beings have selected some of these moths for use in silk production. Environments sometimes harmfully affect cocoon quality as well as the spinners that inhabit them. For instance, the parasitoid bee, Cotesia glomerata, forms cocoon clusters to protect themselves from hyperparasitism (Tanaka and Ohsaki, 2006). However, high humidity causes individual cocoons to be thinner and the clusters to be loose (Tagawa and Satoh, 2008). The harmful effects of high humidity on the quality of cocoons and silk threads are well known in sericulture (Yamamoto, 1975; Kataoka, 1977). Recent experiments have shown that very high humidity negatively affects successful mounting and results in an increase of naked pupae (Watanabe et al., 2014). These are different from genetic naked-pupa (Nd) (Nakao, 1950) that cannot produce fibroin, which leads either to cocoons being constructed exclusively of sericin or to naked pupae. The frequency of adult eclosion has been found to be 88.7% in the naked pupae of Nd mutants (Nakao, 1950). Another naked pupae can be experimentally induced by blocking the spinneret opening, causing them to be naked and thus not become adults (Akao, 1942). These results suggest that physically induced naked pupae are defective and unable to become moths. Two silkworm genome data were deposited into public databases, one originating in Japan (Kaikobase: http://sgp. dna.affrc.go.jp/KAIKObase/) and the other in China (SilkDB: http://silkworm.genomics.org.cn/). These opensource databases have been widely used by entomologists, especially lepidopteran molecular scientists (The International Silkworm Genome Consortium, 2008; Daimon et al., 2014; Xia et al., 2014). The strains, p50T (Daizo) and Dazao used for the respective genome projects, should be very close relatives. A p50T is a single-paired descendant of individuals of strain p50 (a derivative from Daizo kept in the national bioresource project (NBRP) Silkworm) (see http://shigen.nig.ac.jp/silkwormbase/top.jsp). Since the p50 individuals are available through the NBRP Silkworm project and are possible to rear not only with mulberry leaves but also with artificial diets (e.g. Silk Mate, NOSAN Corporation), these silkworms are one of the most important reference strains for lepidopteran studies (Fujiwara and Nishikawa, 2016). Artificial diet rearing has advantages in keeping the silkworms in an incubator throughout the year. In sericulture adequate temperatures for rearing silkworms with mulberry leaves are considered at 27-29°C for 1st instar larvae. Then, breeders may decrease temperature at 1°C after each molting up to 22-24°C in the last instar larvae (The Japanese Society of Sericultural Science, 1979). Relative humidity (RH) is recommended at 85-90% in the beginning and to decrease at approximately 5% in every ecdysis until last instar stage (Kawaguchi and Yanagawa, 1992). The Japanese Society of Sericultural Science (1979) and, Kawaguchi and Yanagawa (1992) claimed that the last instar stage is the most important for silkworm rearing. Ueda et al. (1988) recognized the general importance of lower humidity for parental silkworms for hybridization reared on artificial diets. Their standard—70-80% RH during the 5th instar for the parental strain rearing—sounds similar to preferable RH for mulberry leaf rearing. Kaneko (personal commutation) has enough experience of artificial diet rearing for a practical hybrid (Kinshu × Showa) with the standard condition but has little occurrence of naked pupae. However, the same rearing proceWe found that artificial diet rearing of the silkworm strain p50 under high humidity was harmful to adult emergence. Specifically, median relative humidity (RH) greater than 74% during the 5th instar induced a high rate of occurrence of naked pupae, which then died without emerging as adults (Experiment 1). To determine the specific stage in which mortality induced, we divided the last instar period into three stages—early, middle, and late— and then subjected the larvae to low (L: 47% median RH) or high (H: 80% median RH) humid conditions. The occurrence of naked pupae decreased not according to the specific stage of the larvae but to the duration of exposure to the “L” condition (Experiment 2). We propose that to maintain p50 strains on an artificial diet, they should be reared in lower humidity more than 2/3 period in the last instar stage.","PeriodicalId":34896,"journal":{"name":"Journal of Insect Biotechnology and Sericology","volume":"86 1","pages":"43-47"},"PeriodicalIF":0.0000,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Insect Biotechnology and Sericology","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.11416/JIBS.86.2_043","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"Business, Management and Accounting","Score":null,"Total":0}
引用次数: 0
Abstract
Silk spinners (e.g. spiders, moths, mites, mayflies) and cocoon makers (e.g. spiders, moths, bees, flies) have repeatedly evolved in arthropods, and human beings have selected some of these moths for use in silk production. Environments sometimes harmfully affect cocoon quality as well as the spinners that inhabit them. For instance, the parasitoid bee, Cotesia glomerata, forms cocoon clusters to protect themselves from hyperparasitism (Tanaka and Ohsaki, 2006). However, high humidity causes individual cocoons to be thinner and the clusters to be loose (Tagawa and Satoh, 2008). The harmful effects of high humidity on the quality of cocoons and silk threads are well known in sericulture (Yamamoto, 1975; Kataoka, 1977). Recent experiments have shown that very high humidity negatively affects successful mounting and results in an increase of naked pupae (Watanabe et al., 2014). These are different from genetic naked-pupa (Nd) (Nakao, 1950) that cannot produce fibroin, which leads either to cocoons being constructed exclusively of sericin or to naked pupae. The frequency of adult eclosion has been found to be 88.7% in the naked pupae of Nd mutants (Nakao, 1950). Another naked pupae can be experimentally induced by blocking the spinneret opening, causing them to be naked and thus not become adults (Akao, 1942). These results suggest that physically induced naked pupae are defective and unable to become moths. Two silkworm genome data were deposited into public databases, one originating in Japan (Kaikobase: http://sgp. dna.affrc.go.jp/KAIKObase/) and the other in China (SilkDB: http://silkworm.genomics.org.cn/). These opensource databases have been widely used by entomologists, especially lepidopteran molecular scientists (The International Silkworm Genome Consortium, 2008; Daimon et al., 2014; Xia et al., 2014). The strains, p50T (Daizo) and Dazao used for the respective genome projects, should be very close relatives. A p50T is a single-paired descendant of individuals of strain p50 (a derivative from Daizo kept in the national bioresource project (NBRP) Silkworm) (see http://shigen.nig.ac.jp/silkwormbase/top.jsp). Since the p50 individuals are available through the NBRP Silkworm project and are possible to rear not only with mulberry leaves but also with artificial diets (e.g. Silk Mate, NOSAN Corporation), these silkworms are one of the most important reference strains for lepidopteran studies (Fujiwara and Nishikawa, 2016). Artificial diet rearing has advantages in keeping the silkworms in an incubator throughout the year. In sericulture adequate temperatures for rearing silkworms with mulberry leaves are considered at 27-29°C for 1st instar larvae. Then, breeders may decrease temperature at 1°C after each molting up to 22-24°C in the last instar larvae (The Japanese Society of Sericultural Science, 1979). Relative humidity (RH) is recommended at 85-90% in the beginning and to decrease at approximately 5% in every ecdysis until last instar stage (Kawaguchi and Yanagawa, 1992). The Japanese Society of Sericultural Science (1979) and, Kawaguchi and Yanagawa (1992) claimed that the last instar stage is the most important for silkworm rearing. Ueda et al. (1988) recognized the general importance of lower humidity for parental silkworms for hybridization reared on artificial diets. Their standard—70-80% RH during the 5th instar for the parental strain rearing—sounds similar to preferable RH for mulberry leaf rearing. Kaneko (personal commutation) has enough experience of artificial diet rearing for a practical hybrid (Kinshu × Showa) with the standard condition but has little occurrence of naked pupae. However, the same rearing proceWe found that artificial diet rearing of the silkworm strain p50 under high humidity was harmful to adult emergence. Specifically, median relative humidity (RH) greater than 74% during the 5th instar induced a high rate of occurrence of naked pupae, which then died without emerging as adults (Experiment 1). To determine the specific stage in which mortality induced, we divided the last instar period into three stages—early, middle, and late— and then subjected the larvae to low (L: 47% median RH) or high (H: 80% median RH) humid conditions. The occurrence of naked pupae decreased not according to the specific stage of the larvae but to the duration of exposure to the “L” condition (Experiment 2). We propose that to maintain p50 strains on an artificial diet, they should be reared in lower humidity more than 2/3 period in the last instar stage.
蛛丝动物(如蜘蛛、飞蛾、螨虫、蜉蝣)和制茧动物(如蜘蛛、飞蛾、蜜蜂、苍蝇)在节肢动物中不断进化,人类选择了其中一些飞蛾用于制丝。环境有时会有害地影响茧的质量以及栖息在其中的纺丝虫。例如,拟寄生蜂,Cotesia glomerata,形成茧簇来保护自己免受过度寄生(Tanaka和Ohsaki, 2006)。然而,高湿度会导致单个茧变薄,茧团变松(Tagawa和Satoh, 2008)。高湿度对蚕茧和丝线质量的有害影响在养蚕业中是众所周知的(Yamamoto, 1975;Kataoka, 1977)。最近的实验表明,非常高的湿度会对成功安装产生负面影响,并导致裸蛹的增加(Watanabe et al., 2014)。这与基因裸蛹(Nd) (Nakao, 1950)不同,后者不能产生丝蛋白,导致蚕茧完全由丝蛋白构成或产生裸蛹。在Nd突变体的裸蛹中发现成虫羽化的频率为88.7% (Nakao, 1950)。另一个裸露的蛹可以通过阻断吐丝器的开口来诱导,使它们裸露,从而不能成为成虫(Akao, 1942)。这些结果表明,物理诱导的裸蛹是有缺陷的,不能成为飞蛾。两份家蚕基因组数据已存入公共数据库,其中一份源自日本(Kaikobase: http://sgp)。dna.affrc.go.jp/KAIKObase/),另一个在中国(SilkDB: http://silkworm.genomics.org.cn/)。这些开源数据库已被昆虫学家,特别是鳞翅目分子科学家广泛使用(The International Silkworm Genome Consortium, 2008;damon et al., 2014;夏等人,2014)。用于各自基因组计划的菌株p50T (Daizo)和大枣应该是非常接近的亲缘关系。p50T是菌株p50(一种保存在国家生物资源计划(NBRP)蚕中Daizo的衍生物)个体的单对后代(见http://shigen.nig.ac.jp/silkwormbase/top.jsp)。由于p50个体可以通过NBRP蚕项目获得,并且不仅可以用桑叶饲养,还可以用人工饲料饲养(例如,NOSAN公司的Silk Mate),因此这些家蚕是鳞翅目研究中最重要的参考菌株之一(Fujiwara和Nishikawa, 2016)。人工饲料饲养的优点是将蚕全年保持在孵化器中。在养蚕中,养桑叶蚕的适宜温度为27-29℃。然后,育种者可在每次蜕皮后将温度降低1°C,至末龄幼虫降低22-24°C (the Japanese Society of Sericultural Science, 1979)。相对湿度(RH)建议在开始时为85-90%,并在每个发酵阶段降低约5%,直到最后阶段(Kawaguchi和Yanagawa, 1992)。日本蚕业科学学会(1979)和Kawaguchi and Yanagawa(1992)认为最后一龄阶段是养蚕最重要的阶段。Ueda等人(1988)认识到用人工饲料饲养杂交亲代蚕时,降低湿度的普遍重要性。他们的标准——亲本品系饲养5龄时70-80%的相对湿度——听起来与桑叶饲养的较好相对湿度相似。Kaneko(个人换位)对实际杂交(金州×昭和)有足够的人工饲粮饲养经验,条件标准,但很少出现裸蛹。然而,同样的饲养方法,我们发现在高湿条件下人工饲料饲养p50家蚕对成虫羽化是有害的。具体来说,5龄期间相对湿度(RH)大于74%时,裸蛹的发生率较高,然后裸蛹不成虫而死亡(实验1)。为了确定导致死亡的具体阶段,我们将幼虫的最后龄期分为早、中、晚三个阶段,然后将幼虫置于低(L: 47%中RH)或高(H: 80%中RH)的湿度条件下。裸蛹的出现与暴露在“L”条件下的时间有关(实验2),而不是幼虫的具体阶段有关。我们建议在人工饲料中维持p50菌株,应在末龄2/3以上的低湿度环境中饲养。