鰓及鰓外器官（肺及觸角腺）在半陸生斯氏沙蟹滲透壓調節機制扮演的角色

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Title:	鰓及鰓外器官（肺及觸角腺）在半陸生斯氏沙蟹滲透壓調節機制扮演的角色
Other Titles:	The Roles of the Gills and Extra-branchial Organs (Lung and Antennal Gland) in the Ion Regulatory Mechanisms in the Semi-terrestrial Ghost Crab, Ocypode stimpsoni
Authors:	蔡鵑如 Tsai, Jyuan-Ru
Contributors:	林惠真 Lin, Hui-Chen 東海大學生命科學系
Keywords:	滲透壓調節;斯氏沙蟹;呼吸空氣螃蟹;陸生適應;肺;離子調節;觸角腺;電子顯微鏡;鈉鉀幫浦;氫離子幫浦 Osmoregulation;Ocypode stimpsoni;Air-breathing Crab;terrestrial adaptation;lung;ion regulation;antennal gland;electron microscope;Na+, K+-ATPase;H+-ATPase
Date:	2012
Issue Date:	2013-01-02T09:02:03Z (UTC)
Abstract:	甲殼綱十足目短尾類的螃蟹對不同的棲地類型，擁有多樣化的生理適應。當面臨淡水或是陸域棲地衍生出的血液滲透壓變化以及脫水的問題，短尾類的螃蟹針對體液離子及水分的保存演化出不同的策略。斯氏沙蟹（Ocypode stimpsoni）是高度陸生特化的沙蟹科螃蟹物種，並廣泛分佈在台灣的西部海岸。本研究的目的是探討斯氏沙蟹鰓部及鰓外器官的出現對整體滲透壓調節與氣體交換功能間所產生的變化。首先，針對斯氏沙蟹的陸生特化構造進行研究，觀察結果發現在鰓（gill）及鰓甲（branchiostegite）有特化構造出現，並且在鰓腔中也有發現肺。利用Na+, K+-ATPase活性變化作為偵測離子調節器官的指標，結果發現除了鰓之外，觸角腺（antennal gland）也有很高的活性表現，推測可能為重要離子調節器官之一。以電子顯微鏡觀察觸角腺結構，結果發現觸角腺大致上可以分為三個區域：近端管狀區域（PT）、遠端管狀區域（DT）以及末端管狀區域（ET）。PT及DT由濾囊細胞（coelomic cell, COE）及迷路細胞（labyrinthine cell, LBR）所組成，而ET則由與LBR、COE以及末端迷路細胞（end-labyrinthine cell, ELBR）所組成。其中迷路細胞（LBR）及末端迷路細胞（ELBR）在超微結構觀察中，發現在細胞型態、頂膜的結構以及細胞內粒線體的分佈情形上有明顯的差異。由組織化學及螢光染色法結果發現迷路細胞（LBR）與末端迷路細胞（ELBR）都具有底膜的Na+, K+-ATPase，V-type H+-ATPase與Na+/H+ exchanger位於頂膜，Na-K-2Cl cotransporter則在迷路細胞（LBR）與末端迷路細胞（ELBR）有不同的分佈位置：分別是位在底膜及頂膜。濾囊細胞在足部的延伸部份有輕微Na+, K+-ATPase表現，其餘的V-type H+-ATPase、Na+/H+ exchanger與Na-K-2Cl cotransporter則是都聚集在細胞質中，推測是位在濾囊細胞細胞質中的內膜（endosome）或小泡（vesicle）上。迷路細胞（LBR）和末端迷路細胞（ELBR）與鰓部上皮細胞的離子調節機制類似，而COE則是與哺乳類動物腎臟的足細胞相似。在螃蟹觸角腺上會利用濾囊細胞（COE）進行初級尿液的過濾，再藉由迷路細胞（LBR）及末端迷路細胞（ELBR）進行濾液中離子的再吸收，以達到調節體液離子平衡的目的。綜合以上結論，本研究釐清斯氏沙蟹特化的鰓外器官對其整體的離子調節機制及適應陸域生活扮演的角色：肺彌補了退化的鰓對數，以幫助進行氣體交換；前鰓則由氣體交換鰓轉型為中間型鰓，可幫助短期鹽度改變下的離子調節；而觸角腺則建立了螃蟹可經由尿液進行離子再吸收的可能性。 Brachyuran crabs (Decapod, Crustacea) have diverse physiological adaptations for each biotope. To solve the problems of hemo-dilution and dehydration during freshwater and terrestrial invasion, brachyuran crabs have evolved strategies for water and ion conservation. Ocypode stimpsoni is a highly terrestrial species in Ocypodidae and widely distributes in the central coast of Taiwan. The first part of this study investigated how the extra-branchial organs affect the functional differentiation in the gas exchange and ion regulatory systems in this semi-terrestrial crab. The results showed the modifications of gill and branchiostegite were found in the branchial chamber and the lung structure was discovered. Na+, K+-ATPase (NKA) activity was monitored as indicators for detecting ion regulatory organs. In addition to the gills, the antennal glands also had a high NKA activity and it may be a potential candidate in ion regulatory process. The ultrastructural examination shows the divisions of the antennal gland, including the proximal tubular region (PT), the distal tubular region (DT) and the end tubular region (ET). PT and DT are composed of labyrinthine cells (LBRs) and coelomic cells (COEs) while ET is composed of LBRs, COEs and end-labyrinthine cells (ELBRs). The LBR and ELBR are different in the types of the apical membrane and the density of the mitochondria. According to the immunohistochemical and immunofluorescent staining, basolateral NKA, apical V-type H+-ATPase (VHA) and Na+/H+ exchanger (NHE) in both LBR and ELBR are found. However, the location of the Na-K-2Cl cotransporter (NKCC) is on the basal membrane and apical membrane of the LBR and ELBR, respectively. COE has NKA distributed in the foot process and aggregated VHA, NHE and NKCC in the centre of the cell which suggested the location of the endosomes and vesicles. Comparing the ion regulatory mechanism to the gills, LBR and ELBR had the similar pattern. COE is similar to the podocyte of the kidney. The hemolymph enters the antennal gland and is filtrated into the coelom by passing through COEs. The filtrates are reprocessed by LBRs and transported to the bladder. In summary, this study provides the evidence of the role of extra-branchial organs in the ion regulatory mechanisms and terrestrial invasion in O. stimpsoni. The lungs compensate the reduction of gill pairs for gas exchange. The anterior gills are for ion regulation in short term salinity acclimation and the antennal glands are suggested for ion re-absorption from urine.
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