Cytological studies on artificially induced gynogenesis in the Pacific abalone

Abstract

SUMMARY: To obtain useful information about the mechanism of the induction of gynogenesis in the Pacific abalone, nuclear behavior in normal and gynogenetic eggs was examined during meiosis and first cleavage. After its incorporation into the egg cytoplasm, the UV‐irradiated sperm nucleus gradually dispersed and eventually developed into the male pronucleus, behaving like a normal sperm until contact with the female pronucleus. At mitotic prophase, the male pronucleus in the gynogenetic eggs did not form chromosomes like the female pronucleus, but became a dense chromatin body, which did not participate in karyokinesis. At completion of cytokinesis of the first cleavage, the UV‐irradiated sperm nucleus was seen in the cytoplasm of one of the two blastomeres near the cleavage furrow. As a clear haploid mode was observed in the frequency distribution of chromosome numbers in gynogenetic larval cells, it is suggested that the paternal genome in the gynogenetic eggs does not contribute to the next generation.

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 gynogenesis and effects of ultraviolet irradiation on ultrastructure of sperm of the Zhikong scallop Chlamys farreri

“…suggested that inactivation of sperm chromosomes was a continuous process 8 . Haploid embryos may have originated from a progressive loss of the paternal set of chromosomes 29,30 . The occurrence of aneuploids seems to result from the embryos’ development, which derived from the zygotes fertilized with partially inactivated sperm.…”

“…8 Haploid embryos may have originated from a progressive loss of the paternal set of chromosomes. 29,30 The occurrence of aneuploids seems to result from the embryos' development, which derived from the zygotes fertilized with partially inactivated sperm. As most aneuploids are inviable, the production of aneuploids is not a major concern.…”

“…The dish was placed on a recipro shaker (Guohua Inc., Changzhou, China) 15 cm below a 15-W UV germicidal light (Toshiba GL15, 254 nm UV wave length; Toshiba Inc. Tokyo, Japan), which provided a UV intensity of 256 erg/mm 2 per s as measured by a digtital radiometer (Model 97503-00; Cole-Parmer Instrument Co, Vernon Hills, IL, USA). The sperm suspension in the Petri dish was exposed to UV light for 0, 5,10,15,20,25,30,35,40,45,50,55 or 60 s. During the UV irradiation, the sperm suspension was shaken at 50 cycles/min. At the completion of irradiation, 10 mL egg suspension was added to each Petri dish, mixed and transferred to a 5-L plastic tank for culture at 20 ∞ C in dark.…”

An AFLP genetic linkage map of pacific abalone (Haliotis discus hannai)

“…Research on the techniques of artificial seed production and culture, diseases, and nutrition supported the development of the Pacific abalone aquaculture industry (Li et al, 1999). To improve the increasing valuable Pacific abalone industry, some genetic studies and breeding have also been carried out, including polyploidy breeding (Zhang et al, 1998), crossbreeding (Zhang et al, 2002), hybridization (Sun et al, 2001), gynogenesis (Li et al, 2000), and molecular-based analysis . However, selective breeding of H. discus hannai is still in its infancy.…”