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Urbán-Duarte D, Tomita S, Sakai H, Sezutsu H, De La Torre-Sánchez JF, Kainoh Y, Furukawa S, Uchino K. Effect of chemical dechorionation on silkworm embryo viability. JOURNAL OF INSECT PHYSIOLOGY 2022; 137:104327. [PMID: 34762918 DOI: 10.1016/j.jinsphys.2021.104327] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 10/05/2021] [Accepted: 11/02/2021] [Indexed: 06/13/2023]
Abstract
The chorion covering/protecting insect egg, which has some effective functions such as providing mechanical strength, protecting eggs from external environments, and keeping moisture adjustment, is one of the principal barriers to manipulation, cryopreservation, and study of insect embryos. Here we evaluated the silkworm embryo viability after dechorionation using chemical reagents. We have developed an easy and effective method for chemical dechorionation that enables embryos to develop in culture, so that the larvae could normally grow. Eggs attached to a nylon net were treated with potassium hydroxide (KOH) and sodium hypochlorite (NaClO) to remove the chorion, washed with the Grace's insect medium, and then cultured using a dry-moist method which we created. The most effective treatment with regard to embryonic development, hatching, and production of second instar larvae was 30% KOH for 7 min and 2% NaClO for 5 min at 27 °C. Embryos at later embryonic stages were more tolerant to chemical dechorionation and over 75% of embryos treated at 168 h-old (Stage 25, appearance of taenidium) survived to the second larval instar, moreover, the larvae derived from the dechorionated embryos have developed into the moths which can lay the fertilized eggs. Our method would contribute to the establishment of cryopreservation using embryos and analysis of silkworm embryogenesis and might also be applicable to other insect species.
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Affiliation(s)
- David Urbán-Duarte
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki 305-8572, Japan; Centro Nacional de Recursos Genéticos, Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias, Tepatitlán de Morelos, Jalisco 47600, Mexico
| | - Shuichiro Tomita
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, 1-2 Owashi, Tsukuba, Ibaraki 305-8634, Japan
| | - Hiroki Sakai
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, 1-2 Owashi, Tsukuba, Ibaraki 305-8634, Japan
| | - Hideki Sezutsu
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, 1-2 Owashi, Tsukuba, Ibaraki 305-8634, Japan
| | - José Fernando De La Torre-Sánchez
- Centro Nacional de Recursos Genéticos, Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias, Tepatitlán de Morelos, Jalisco 47600, Mexico
| | - Yooichi Kainoh
- Faculty of Life and Environmental Sciences, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki 305-8572, Japan
| | - Seiichi Furukawa
- Faculty of Life and Environmental Sciences, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki 305-8572, Japan
| | - Keiro Uchino
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, 1-2 Owashi, Tsukuba, Ibaraki 305-8634, Japan.
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DeBardlabon KM, Rajamohan A, Rinehart JP. Vitrification of manually stage-selected embryos of Drosophila have significantly higher survival and emergence - Consequences for insect germplasm storage. Cryobiology 2022; 105:83-87. [PMID: 35032470 DOI: 10.1016/j.cryobiol.2022.01.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 01/02/2022] [Accepted: 01/06/2022] [Indexed: 11/03/2022]
Abstract
Embryonic selection for vitrification and cryostorage in Drosophila and other dipterans is generally carried out by gross observation of the embryonic development at a constant temperature. In this study, the effect of embryo developmental temperature (19, 20 and 21 °C) on the stage specific convergence of the embryonic development to the developmental stages 15-17, that is useful for cryopreservation, was studied in a flightless mutant strain of Drosophila melanogaster and compared with the Ore-R strain. The temperature that allowed for the best convergence to stage 16 was chosen for further selection and treatment of the embryos. The converged embryos (SS) were directly treated or further manually sorted (MS) for the requisite developmental stage to reduce the number of non-convergent embryos. These selected embryos were then permeabilized and cryopreserved. While at all the three incubation temperatures the embryos exhibited convergence peaks, it was only at 20 °C and at hour 22 that a maximum number of stage 16 embryos converged and remained at a much higher proportion than the other developmental stages in both the strains. When permeabilized, MS embryos showed higher mean viability and hatching proportion compared to SS embryos (wingless: ∼0.70 vs. ∼0.58; Ore-R: ∼0.77 versus 0.54). Upon vitrification, the manually selected embryos hatched and survived at significantly higher mean rates than the converged embryos at stage 16 (wingless: 0.32 vs. ∼0.08; Ore-R: 0.47 vs. 0.15) after adjusting for permeabilization mortality. The maximum proportion hatch after vitrified storage that could be obtained by this method was 0.74 for both the wingless and Ore-R strains. More than 55% of the larvae pupated and >72% of the pupae eclosed in MS and vitrified wingless stage 16. In Ore-R, well over 85% of the larvae pupariated and eclosed as flight capable flies.
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Affiliation(s)
- Korie M DeBardlabon
- USDA-ARS Red River Valley Agricultural Research Center, Biosciences Research Laboratory, 1605 Albrecht Boulevard North, Fargo, ND, 58102-2765, USA
| | - Arun Rajamohan
- USDA-ARS Red River Valley Agricultural Research Center, Biosciences Research Laboratory, 1605 Albrecht Boulevard North, Fargo, ND, 58102-2765, USA.
| | - Joseph P Rinehart
- USDA-ARS Red River Valley Agricultural Research Center, Biosciences Research Laboratory, 1605 Albrecht Boulevard North, Fargo, ND, 58102-2765, USA
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