Fig 3 - uploaded by Ryosuke Murata
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Histological images of undifferentiated gonads and testes in Sepia lycidas. The undifferentiated gonad at 28 (a) days after spawning (DAS) and 10 (b) days post hatching (DPH). The immature testis at 20 (c), 60 (d), and 90 (e, low magnification; f, high magnification) DPH. The testis with active spermatogenesis at 150 (g, low magnification; h, high magnification) DPH. The red dotted lines in the figure (c, d, and f) indicates the seminiferous tubule. GC, germ cell; SC, somatic cell; ST, seminiferous tubule; Sg, spermatogonium; Sc, spermatocyte; St, spermatid, Sp, sperm; BV, blood vessel. Scale bars ¼ 20 μm (b, c, d, f, and h), 50 μm (a), and 100 μm (e and g).
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To understand and obtain basic information on sex differentiation in the kisslip cuttlefish (Sepia lycidas), the gonadal sex differentiation process was investigated histologically. An undifferentiated gonad consisting of germ cells and somatic cells was found to form at a caudal site in the space between the internal yolk sacks of cuttlefish embry...
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... other individuals, although the gonad had gradually enlarged from the mitotic proliferation of germ cells, none of the meiotic germ cells were observed in the gonad from 28 DAS to 10 DPH ( Fig. 3a and b). A seminiferous tubule consisting of a surrounding basement membrane and spermatogonia was first observed in the gonad at 20 DPH (Fig. 3c). Although spermatogonia in the seminiferous tubules gradually increased by mitotic division throughout the testes, spermatogenesis had not occurred even at 60 and 90 DPH (Fig. 3d, e, and f). ...
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... other individuals, although the gonad had gradually enlarged from the mitotic proliferation of germ cells, none of the meiotic germ cells were observed in the gonad from 28 DAS to 10 DPH ( Fig. 3a and b). A seminiferous tubule consisting of a surrounding basement membrane and spermatogonia was first observed in the gonad at 20 DPH (Fig. 3c). Although spermatogonia in the seminiferous tubules gradually increased by mitotic division throughout the testes, spermatogenesis had not occurred even at 60 and 90 DPH (Fig. 3d, e, and f). Spermatogenesis, and a large amount of released sperm in the inner cavity of the seminiferous tubule, was first observed at 150 DPH ( Fig. 3g and ...
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... from 28 DAS to 10 DPH ( Fig. 3a and b). A seminiferous tubule consisting of a surrounding basement membrane and spermatogonia was first observed in the gonad at 20 DPH (Fig. 3c). Although spermatogonia in the seminiferous tubules gradually increased by mitotic division throughout the testes, spermatogenesis had not occurred even at 60 and 90 DPH (Fig. 3d, e, and f). Spermatogenesis, and a large amount of released sperm in the inner cavity of the seminiferous tubule, was first observed at 150 DPH ( Fig. 3g and h). Neither the ovary nor the testis showed a duct-like structure during gonadal sex differentiation and development. A schematic diagram of the gonadal sex differentiation process in S. ...
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... at 20 DPH (Fig. 3c). Although spermatogonia in the seminiferous tubules gradually increased by mitotic division throughout the testes, spermatogenesis had not occurred even at 60 and 90 DPH (Fig. 3d, e, and f). Spermatogenesis, and a large amount of released sperm in the inner cavity of the seminiferous tubule, was first observed at 150 DPH ( Fig. 3g and h). Neither the ovary nor the testis showed a duct-like structure during gonadal sex differentiation and development. A schematic diagram of the gonadal sex differentiation process in S. lycidas is shown in Fig. ...
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... Sepiella japonica (Pang et al. 2018), Sepia pharaonis (Minton et al. 2001) and Sepia lycidas (Murata et al. 2019) are the main cephalopod species commonly found on the south coast of China. They exhibit high growth rates and a short life cycle which make them ideal for artificial breeding. ...
A high resolution melting (HRM) curve analysis of single nucleotide polymorphisms (SNPs) was used to identify three Sepia species, commonly found on the south coast of China. The mitochondrial 16S rRNA gene sequences from Sepiella japonica, Sepia pharaonis and Sepia lycidas were amplified and aligned. A total of 19 SNPs and seven deletion sites were identified in 122-base-pair (bp) amplicons. All samples from the three Sepia species were clustered into three curves based on HRM analysis, in line with the sequencing results. This new method thus enables a quick, economical and efficient identification of Sepia species.
Gonadotropin-releasing hormone (GnRH) is one of the most important neuroendocrine regulators for animal reproduction. GnRH-like peptide (GnRH-like) has recently been shown to play a critical reproductive role mainly in gametogenesis or steroidogenesis in the gonads of some molluscs, including cephalopods. However, its involvement in gonadal sex differentiation remains unknown. Here, we show the expression profile of GnRH-like in the brain of the cephalopod kisslip cuttlefish, Sepia lycidas, throughout gonadal sex differentiation, by quantitative real time RT-PCR and immunohistochemistry. We found that GnRH-like could be detected in the brain at a sexually undifferentiated stage, and its expression level significantly increased upon initiation of gonadal sex differentiation. However, no significant difference in GnRH-like expression levels was observed between sexes during gonadal sex differentiation. Additionally, we demonstrated immunoreactivity of GnRH-like in glial cells or immature neurons, which are mainly distributed in the non-reproductive related area of the cephalopod brain, suggesting the immature function of the reproductive endocrine axis during early ontogenesis. Our results demonstrate for the first time, the expression profile of GnRH-like during early ontogenesis in cephalopods.
