水生型呼吸空氣魚類–珍珠馬甲(Trichogasterleeri)鰓部形態變異與功能分化

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Title:	水生型呼吸空氣魚類–珍珠馬甲(Trichogasterleeri)鰓部形態變異與功能分化
Other Titles:	Morphological Plasticity and Functional Differentiation in the Gills of the Aquatic Air-Breathing Fish, Trichogaster leeri
Authors:	黃俊諺 Huang, Chun-Yen
Contributors:	林惠真 Lin, Hui-Chen 東海大學生命科學系
Keywords:	珍珠馬甲;呼吸空氣魚類;酵素活性值;形態;分化 Air-breathing fish;Na+;Morphology;Gill;Differentiation;Trichogaster leeri;K+-ATPase ESA
Date:	2005
Issue Date:	2011-05-19T08:01:47Z (UTC)
Abstract:	魚類呼吸具非呼吸空氣與呼吸空氣兩種模式，其中呼吸空氣魚類中，可區分成兩棲型與水生型。水生型呼吸空氣魚類具有特化的輔助呼吸器官來輔助鰓部進行氣體交換。魚鰓是一個多功能的器官，主要是進行氣體交換及離子調節。藉由鰓部形態與功能的變化，魚隻可以適應不同環境壓力的改變。對於水生型呼吸空氣魚類進行的研究，大多著重於鰓部血管的形態敘述；目前尚無證據指出，形態變異是否與功能分化有相關性。另外，對於離子調節酵素的相關研究，都以某一對鰓來代表魚隻鰓部，無個別觀察四對鰓來討論鰓部功能的分化。因此，此實驗假說是具迷器類型的水生型呼吸空氣魚類，鰓部有形態變異與功能分化情形。第一、二對鰓具適應離子調節壓力的能力，有形態與功能的可塑性。第三、四對鰓特化成輸送充氧血的血管通道，面對環境壓力時則不具可塑性。實驗物種為水生型呼吸空氣魚類中的珍珠馬甲（Trichogaster leeri），藉由量化鰓部型值與組織染色來檢視形態的變化；測量鰓部Na+, K+-ATPase ESA（酵素活性值）來檢視功能的分化。形態變異結果發現，魚隻四對鰓在外觀形態、鰓絲密度、鰓弓長度、鰓絲長度與鰓薄板長度皆具有不同程度的變化，加上組織染色發現第四對鰓具有膨大腔室的現象，皆支持第四對鰓已特化成輸送充氧血的血管通道。此外，富含粒線體細胞數量，第一與第二對鰓在具離子調節壓力的環境下，有數量上的增加；相對地，在第三與第四對鰓則無此現象出現。推測此結果與前後鰓所假設的功能不同有關係。功能分化的結果中，檢視Na+, K+-ATPase ESA，顯示前後對鰓的離子調節能力在時間點上有所不同。此外，魚隻轉移至5 g/L半淡鹹水與一次去離子水環境中4天，第一與第二對鰓的Na+, K+-ATPase ESA，顯著大於第三與第四對鰓，暗示著水生型呼吸空氣魚類四對鰓在功能上有分化的現象。總結而言，水生型呼吸空氣魚類的珍珠馬甲（T. leeri），四對鰓形態與功能具有變異與分化的情形，而且各對鰓在面臨離子調節壓力時的可塑性不同。 Non-air-breathing and air-breathing are two respiratory modes in fishes. The air-breathing fish can be further divided into the amphibious and the aquatic air-breathing fish. The aquatic air-breathing fish has specialized accessory air-breathing organ. Fish gill is a multifunctional organ and is responsible for at least gas exchange and ionic regulation. By modifying their gill morphologies and functions, fishes are adaptive to various environmental stresses. For the aquatic air-breathing fish, most studies focused on the morphology of the gill vascular system. There was no evidence whether the morphological plasticity directly relates to their functional differentiation. Nevertheless, most studies on the enzyme activity for the ionic regulation focused only on a particular pair of gills. No study was conducted to examine the four pairs of gills simultaneously. The experiment hypothesis is that aquatic air-breathing fish with labyrinthine organ has both morphological plasticity and functional differentiation in the gills. The first and the second gills have the morphological and functional plasticity and were responsible for ionic regulation stress; the third and the fourth gills become specialized for the transport of oxygenated blood, and are less plastic to environmental stress. The experimental species was the aquatic air-breathing fish, Trichogaster leeri. I investigated several morphmetric parameters and the histological examination to test the morphological plasticity of the gills, and used the Na+, K+-ATPase ESA to test the functional differentiation of the gills. The morphological plasticity were found in various aspects, including the gross anatomy of gills, the filament density, the length of the gill arch, the length of the filaments and the length of the lamellae of the each gill arch in fish. There were swelling chambers, presumably blood vessels, in the fourth gill arch and this implied that the morphology of the fourth gill could be specialized for the transport of oxygenated blood. Further, the number of mitochondria-rich cells in the first and the second gills increased upon an ionic stress, whereas no difference was found in the third and the forth gills. This phenomenon suggested that there were functional difference between the anterior and the posterior gills. The variation in the Na+, K+-ATPase ESA demonstrated that the anterior and the posterior gills differ in their abilities to ionic stress. The Na+, K+-ATPase ESA was higher in the first and the second gills upon transferred to 5 g/L and deionized water, respectively, for 4 days. These imply that the gills of the aquatic air-breathng fish have the functional differentiation. These results support the hypothesis that both morphological plasticity and functional differentiation can be found in the gills of the aquatic air-breathing fish, Trichogaster leeri. And, the plasticity of each gill was different in ionic stress.
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