2011年7月23日 星期六

稀有目前還存在的[古代怪異巨型魚類]---[鉅鰩]

反應: 
 
 
分佈於世界熱帶及亞熱帶淺水區,底棲,常出入於港灣、河口,有時可上溯江河相當遠的距離。已知有些生活和產卵於尼加拉瓜湖中。頭、體長而平扁,吻延長,很像鋸鯊那樣呈劍形,兩側緣具強齒。最大的體長可達9公尺。占體全長1/3的吻鋸令人生畏。吻鋸用於攝食活動,或用之發掘底層生物,或用以在魚群中揮舞,殘殺或擊傷群魚。在一些地區可供食用、煉油、制革及生產其他產品,據說小鋸鰩是佳餚。
 
 
鋸鰩 - 簡介
鋸鰩是一種性情兇猛的鯊魚。鋸鰩的生長速度較慢,產下的幼體極易受其他食肉魚類的攻擊,加上人類的過度捕撈以及環境污染,因此數量正急速減少。以前曾廣泛生活在地中海和大西洋東部的鋸鰩如今已在歐洲海域完全消失。
軟骨魚綱板鰓亞綱的鋸鰩目。本目僅有鋸鰩科鋸鰩屬約6種。吻平扁狹長,劍狀突出,邊緣具堅硬吻齒。無鼻口溝。鰓孔5個,腹位,位於胸鰭基底內側。背鰭2個,無硬棘;胸鰭前緣伸達頭側後部;尾粗大,尾鰭發達;奇鰭與偶鰭的輻狀軟骨後端具很多角質鰭條。非常像鋸鯊目的鯊魚,但不同的地方是鋸鰩身體扁平,鰓腹位(在身體的下方),鋸吻上沒有肉質觸鬚。
化石見於上白堊紀至近代。分佈於熱帶、亞熱帶各近岸海區和各大河口,有些進入江、河、湖泊、甚至定居於淡水中並進行繁殖。
 
 
鋸鰩 - 種類劃分
中國產2種,其中尖齒鋸鰩,第一背鰭起點對著腹鰭基底後端上方;尾鰭下葉前部顯著三角形突出;吻齒2135。分佈於南海和東海南部,也見於紅海、印度洋、印尼。行動滯緩,常潛伏泥沙上,用吻鋸掘土覓食,偶爾也上升至水面,露出背鰭。主要攝取泥沙中的甲殼類或其他無脊椎動物,也用吻鋸襲擊成群的魚類而食其受傷的個體。卵胎生,胎兒具大型卵黃囊,吻鋸柔軟,吻齒包于皮膜中。每產約10餘仔。仔魚剛生時,體長約60釐米。成魚最大體長可達9公尺,吻鋸長2~3公尺,寬30公分。尖齒鋸鰩為東海和南海次要經濟魚類、在中國產量不大。肉質鮮美,鰭可制魚翅,皮可制革和刀鞘,肝可制魚肝油。
 
小齒鋸鰩,第一背鰭起點前於腹鰭起點;尾鰭下葉前部三角形突出;吻齒1722對。見於南海,亦見於印度洋、印尼、大洋洲東北部。鋸鰩有的品種相當大,身長可達5米。
 
 
 
鋸鰩 - 分佈繁殖
分佈於南海和東海南部,也見於紅海、印度洋、印尼。
 
鋸鰩 - 物種溯源
鋸鰩屬軟骨魚綱板鰓亞綱的鋸鰩目。軟骨魚綱(Chondrichthyes)全身具軟骨質的骨骼系統,體被楯鱗,口位於頭部腹面,歪尾,腸內有螺旋瓣。終生保留軟骨,常鈣化,但無任何真骨組織;有發達的鰓間隔,鰓裂大多虞接開口於體表,無鰾,雄性有特殊的交接器——鰭腳,卵大,富於卵黃,盤狀分裂,體內受精,卵生或卵胎生,歪尾。外骨骼不發達或退化,腦顱為原顱,上頜由齶方軟骨,下頜由梅氏軟骨組成。鰓孔每側57個,分別開口於體外;或鰓孔1對,被以皮膜。雄魚腹鰭裡側有交配器的鰭腳。腸短,具螺旋瓣。心臟動脈圓錐有數列瓣膜。無大型耳石。泄殖腔或有或無。分佈于低緯度海洋,個別棲息淡水。軟骨魚綱分為兩個亞綱:板鰓亞綱和全頭亞綱。板鰓亞綱(Elasmobranchii);鰓裂5對,鰓間隔寬大,板狀,如各種鯊、鰩。全頭亞綱(Holocephali):頭大而側扁,鰓裂4對,上頜骨與腦顱癒合,故稱全頭類,如我國產的黑線銀鮫(Chimaeraphantasma)。軟骨魚系Chondrichthyes本系是現存魚類中最低級的一個類群,全世界約有200多種,中國有140多種,絕大多數生活在海裡。
 
 
 
 
 
 
 
為什麼會查這個資料,因為在探索頻道看到,聽說鉅鰩會吃人類
傳言有人坐木船遇到鉅鰩,鉅鰩會用鉅鉅開船隻,讓人掉落海中以便吃人...聽起來有點恐怖~不知道真的還假的,不過這種魚看起來真的不面善倒是真的~

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