Induction of gynogenetic diploids and cytological studies in the zhikong scallop,Chlamys farreri

Abstract

The induction of gynogenetic diploids during meiosis II in the scallop Chlamys farreri was attempted using the treatments of cytochalasin B (0.5 µg ml −1 ; CB) and 6-dimethylaminopurine (60 µg ml −1 ; 6-DMAP). The effects of CB and 6-DMAP treatments on meiosis and fertilization of eggs were also examined. Haploid gynogenesis was induced by sperm which were ultraviolet-irradiated for 30 s at an intensity of 2561 µW cm −2 s −1 . CB and 6-DMAP treatments were highly effective in suppressing meiosis II, yielding 19% and 28% gynogenetic diploids, respectively. Compared with the CB treatment, the 6-DMAP treatment produced more expected D-shaped larvae. Cytological observations revealed that 6-DMAP inhibited pronuclear movements and the segregation of chromosomes, resulting in the formation of one big diploid female pronucleus with strong fluorescence, while CB inhibited cytokinesis, resulting in two female pronuclei formations. The UV-irradiated sperm nucleus developed into a male pronucleus, but did not participate in karyokinesis at mitotic anaphase, suggesting that gynogenetic diploids were induced in the scallop.

Cytological studies on induced meiogynogenesis in Japanese flounderParalichthys olivaceus(Temminck et Schlegel)

“…As demonstrated by the present cytological study, the UV‐irradiated sperm nucleus remained condensed even in the stages of early cleavage. Such a condensed sperm nucleus is known as a dense chromatin body (DCB), which was generally reported for other artificially induced or spontaneous gynogenetic species (Oshiro 1987; Fujioka 1993; Kobayashi 1997; Li, Osada, Kashihara, Hirohashi & Kijima 2000; Pan, Li, Yu & Wang 2004; Itono, Okabayashi, Morishima, Fujimoto, Yosikawa, Yamaha & Arai 2007). Kobayashi (1997) reported that in amago salmon Oncorhynchus rhodurus , the dropping out of the paternal genome in the gynogenetic eggs did not occur just after insemination or before the conjugation with the female pronucleus, but in the anaphase to the telophase of the first cleavage.…”

Induction of Gynogenetic Diploids the Tropical Oyster, Crassostrea belcheri 1873 (Ostreids: Ostreoidea)

“…Note: ns= not significant difference (P>0.05) Previous reports have documented the induction of diploid gynogenesis. For example, [10] investigated gynogenesis induction in the C. farreri using a UV intensity of 256 µW cm −2 s −1 for 30 seconds. They found that the egg development rate in the control group was 73.3%, but this rate gradually decreased to 33.5% after 30 seconds of exposure.…”

“…Males also have a higher mortality rate than females, which could be related to changes in the sea [7]. It has been reported that diploid gynogenesis can be achieved in mollusk species such as Haliotis diversicolor, H. discus hannai, C. farreri, M. edulis, M. galloprovincialis, and M. lateralis through cold shock treatment, cytochalasin B, and 6-dimethylaminopurine [8][9][10][11][12][13]. However, the application of this technique in the economically important C. belcheri species in Thailand have not yet been reported.…”

Triploid induction by hyperosmotic shock in the Yesso scallop, Patinopecten yessoensis

“…The superfluous sperms were removed through a 25‐μm sieve 5 min postfertilization (PF). The zygotes were washed with phosphate buffer (0.1 M, pH = 7.4, with 8% sucrose), stained with 4,6‐diamidina‐2‐phenylindole (10 μg/mL), and observed under a fluorescence microscope (Olympus BX51, Olympus Corporation, Tokyo, Japan) to determine the cleavage speed (Pan, Li, Yu, & Wang, ). Samples were taken every 10 min in the first hour, every 20 min for 1–3 hr PF, and every hour for 3–6 hr PF and were fixed with 4% formaldehyde in seawater.…”

“…Corporation, Tokyo, Japan) to determine the cleavage speed (Pan, Li, Yu, & Wang, 2004 induction, and incubation was maintained at 13 AE 0.5 C. The cleavage ratio (CR; percentage of two-celled embryo to oocytes in at least 50 random embryos), hatching ratio (HR; percentage of D-shaped larvae to zygotes before PB1 s were released), and triploid ratio (TR) were estimated, and the general evaluation index I e (HR*TR) was calculated to determine the overall induction effect. Each parameter was tested in triplicate.…”