Sunday, April 26, 2015

鰻魚恐限制出口

鰻魚恐限制出口 業者剉咧等

Thursday, April 23, 2015

2015鰻苗入池量

根據《日本養殖新聞》報導,截止4月20日,日本、中國大陸、韓國、臺灣共入池鰻苗30.3噸,遠低於去年同期80噸的入池量。

具體入池情況如下:

日本共入池鰻苗17噸,占總量的56.2%;

中國大陸共入池鰻苗8.2噸,占總量的27.1%;

韓國共入池鰻苗4.2噸,占總量的13.9%;

臺灣共入池鰻苗850㎏,占總量的2.8%。

(http://cwin.com/scpnews/view.asp?id=6836#.VTmMH1ulzZw.facebook)

幾點臆測


目前在鰻魚研究上有幾點臆測:

1.      黃鰻變成銀鰻時,下垂體的melanocortin 系統是大量表現 (http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0077396)

2.     Melanocortin 可刺激小鼠性腺(精巢)初期發育 (http://www.reproduction-online.org/content/133/6/1181.short)


4.     基因重組的鰻魚 LH FSH 對鰻魚卵巢的刺激功能遠遠不及腦下垂體研磨液 (http://www.biolreprod.org/content/79/5/938.long) Fig.7
 
故ACTH 系統對鰻魚性腺發育與黃銀轉換是可以期待與試驗的,但不能否認太多的例子與證據顯示cortisol 對生殖的抑制作用。

Monday, April 20, 2015

日研究鰻魚活動模式

日研究揭鰻魚活動模式 白天深水活動 深夜移往較淺水位置(2015/4/19)
(http://www.mingpaocanada.com/realtimenews/VAN/content_international_NEW.cfm?aid=165783&m=0)


日本水產綜合研究中心日前發表一份公報稱,其研究小組首次弄清了日本鰻魚的行動模式,發現日本鰻魚能夠感知太陽光和月光,在深夜游到比較淺的位置,而白天則移動到較深位置。
由於根據這種行動模式可以推測鰻魚的位置,將有助於弄清日本鰻魚前往產卵場的洄游路線之謎。
鰻魚營養豐富,是日本人夏天最愛吃的美食之一,不過近年來,捕獲量卻不斷下降,世界自然保護聯盟(IUCN)去年6月12日宣布,已將日本鰻魚列入瀕危物種紅色名錄,因此,弄清鰻魚的生活方式和洄游路線,對於保護鰻魚非常重要。
日本鰻魚在日本國內的河流和湖泊長大後,會在海中移動數千公里,前往遠洋產卵。研究小組2010年在作為日本鰻魚產卵場的太平洋馬利亞納海溝附近放流了11條帶有超聲波發射器的野生成年日本鰻魚,2012年在日本近海放流了5條帶有超聲波發射器的養殖成年日本鰻魚,然後利用漁業調查船進行了跟蹤調查。
研究小組通過超聲波發射器,調查了鰻魚所在位置的水深和水溫等數據,然後在船上觀測了太陽光的強度,詳細調查了與鰻魚游泳深度的關係。結果發現,野生鰻魚在日出約1小時之前就開始潛向海洋深處,白天在500米至800米深的深海活動,太陽光的強度越高,鰻魚活動的位置越深。此後,隨著太陽落山,鰻魚開始向上浮,到水深150米至300米的較淺位置活動。但是,養殖的鰻魚卻沒有看到這種行動模式。
研究小組認為,鰻魚在白天為了躲避外敵而潛到較深位置,但是深海水溫很低,所以在夜間又游到了比較溫暖的淺層位置。這種每天的活動非常有規律,能夠根據游泳深度數據的變化確定日出和日落的時刻,因此也可以推算游泳地點的經緯度,從而有望幫助弄清鰻魚從日本游到馬利亞納海溝附近產卵的洄游路線之謎。研究小組根據這種行動模式推算鰻魚的位置,發現和實際跟蹤時的位置基本一致。
研究小組認為,鰻魚眼球內應該具有即使在深海也能夠感光的高靈敏度感測器。今後,收集更多的鰻魚游泳深度的數據,就有可能掌握其洄游的線路。這一成果的論文已經刊登在新一期美國線上科學雜誌《公共科學圖書館綜合卷》上。



Light-Sensitive Vertical Migration of the Japanese Eel Anguilla japonica Revealed by Real-Time Tracking and Its Utilization for Geolocation
  • Published: April 15, 2015
  • DOI: 10.1371/journal.pone.0121801
  • (http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0121801)

    PTEN or Cilostazol on artificial-induced ovarian development in the Japanese eel


    PTEN or Cilostazol on artificial-induced ovarian development

    in the Japanese eel,  Anguilla Japonica

     

    Yung-Sen Huang1*, Jin-Chywan Gwo2, and Ching-Fong Chang2

    1 Depart. Life. Sci., National University of Kaohsiung;

    2 Depart. Aquaculture, National Taiwan Ocean University;

    yshuang@nuk.edu.tw

     

    The stimulatory effects of gonaotropins upon ovarian development are mainly provoked by the intracellular cAMP production through GPCR (G-protein-couple receptors); furthermore, PI3K (phosphoinositide-3-kinases) pathway is now recognized as one critical pathways in early follicular development, roles of the PI3K were revealed by deletion of PTEN (Phosphatase and Tensin homolog on chromosome 10). Two forms of PTEN have been cloned from the Japanese eel. Cilostazol (Pletal®) is a selective inhibitor of phosphodiesterase type III (PDE3, mainly located in mammalian ovarian follicle cells) and Cilostazol-induced vasculo-angiogenesis effects have also been shown, but there is no data on its effects in fish. The natural blockage and inducible of ovarian development in the eel was a benefit to study roles of PTEN and Cilostazol on the induced ovarian growth. Our data suggested that two forms of PTEN are existing in the eel, and progress of ovarian development corresponded to the decrease of ovarian PTEN expression, vice versa. A continuing administration of PDE3 inhibitor had inhibitory effects on the induced ovarian development in the Japanese eel, and intracellular cAMP levels seem to be temporal and spatial regulated in the eel ovarian follicles.  The applications of PTEN-inhibitors and/or PDE3-inhibitors might be useful to get a good quality egg from artificial maturation.  

     

    Key words: Anguilla japonica, cAMP, Cilostazol, ovary, PDE3, PI3K, PTEN, T

    Melanocortin and Reproduction

    The Pituitary Gland of the European Eel Reveals Massive Expression of Genes Involved in the Melanocortin System

    • Published: October 10, 2013
    Hormones secreted from the pituitary gland regulate important processes such as development, growth and metabolism, reproduction, water balance, and body pigmentation. Synthesis and secretion of pituitary hormones are regulated by different factors from the hypothalamus, but also through feedback mechanisms from peripheral organs, and from the pituitary itself. In the European eel extensive attention has been directed towards understanding the different components of the brain-pituitary-gonad axis, but little is known about the regulation of upstream processes in the pituitary gland. In order to gain a broader mechanistic understanding of the eel pituitary gland, we have performed RNA-seq transcriptome profiling of the pituitary of prepubertal female silver eels. RNA-seq reads generated on the Illumina platform were mapped to the recently assembled European eel genome. The most abundant transcript in the eel pituitary codes for pro-opiomelanocortin, the precursor for hormones of the melanocortin system. Several genes putatively involved in downstream processing of pro-opiomelanocortin were manually annotated, and were found to be highly expressed, both by RNA-seq and by qPCR. The melanocortin system, which affects skin color, energy homeostasis and in other teleosts interacts with the reproductive system, has so far received limited attention in eels. However, since up to one third of the silver eel pituitary’s mRNA pool encodes pro-opiomelanocortin, our results indicate that control of the melanocortin system is a major function of the eel pituitary.




    Effects of ACTH and expression of the melanocortin-2 receptor in the neonatal mouse                                                   

    Abstract

    ACTH has been shown to stimulate androgen production by the fetal/neonatal mouse testis through the melanocortin type 2 receptor (MC2R). This study was designed to localize the expression of MC2R in the neonatal mouse testis and characterize the effects of ACTH on testicular androgen production. Using immunohistochemistry, MC2R was localized to the fetal-type Leydig cell population of the neonatal testis. ACTH caused a time-dependent increase in cyclic AMP (cAMP) and testosterone production by isolated cells with an increase in cAMP apparent in < 3 min. There was no additive effect of maximally stimulating doses of ACTH and human chorionic gonadotropin (hCG). Androgen production in response to ACTH and hCG was reduced by UO126 and dexamethasone, which are the inhibitors of ERK1/2 and phospholipase A2 respectively. Expression of mRNA encoding StAR was increased fourfold by both ACTH and hCG, although expression of mRNA encoding for steroidogenic enzymes was not markedly affected. The potency of N-terminal fragments of ACTH to stimulate androgen production was similar to that seen previously in the adrenal. Data indicate that both LH and ACTH, acting through their respective receptors, stimulate steroidogenesis by fetal-type Leydig cells via arachidonic acid, protein kinase A, and ERK1/2 activation of StAR.






    Huang YS, Rousseau K, Sbaihi M, Le Belle N, Schmitz M et al. (1999) Cortisol selectively stimulates pituitary gonadotropin beta-subunit in a primitive teleost, Anguilla anguilla. Endocrinology 140: 1228–1235. doi:10.1210/en.140.3.1228. PubMed: 10067848.