| Abstract: | 鰓及觸角腺為螃蟹的離子組調節器官。前人研究指出，沙蟹與方蟹的鰓部功能及輔助呼吸器官型態有所不同，此現象可能與兩者的親緣關係及入侵陸生棲地方式間存在差異有關。另一方面，在沙蟹與方蟹觸角腺的離子調節能力的研究中發現，沙蟹總科(Ocypodoidea)沙蟹科(Ocypodidae)沙蟹屬(Ocypode)中大西洋幽靈蟹(Ocypode quadrata)的觸角腺具有高鈉鉀幫浦活性，並能由尿液中回收鈉離子及增加尿液中含氮廢物的濃度；但在方蟹總科(Grapsoidea)陸蟹科(Gecarcinidae)地蟹屬(Gecarcinus)中側身地蟹(Gecarcinus lateralis)的觸角腺鈉鉀幫浦活性並沒有增加的情形，亦無法增加尿液中的含氮廢物濃度。由於僅有少數研究進行螃蟹觸角腺鈉鉀幫浦活性及離子調節功能的比較，因此本研究的目的是想檢視沙蟹及方蟹觸角腺鈉鉀幫浦活性及離子調節功能是否有所不同。另外，先前研究指出，不同螃蟹觸角腺濾囊覆蓋度存在差異，本實驗中亦會進一步觀察物種間觸角腺結構。實驗挑選五科八種臺灣西海岸常見的螃蟹，包含：沙蟹總科內沙蟹科的弧邊招潮蟹(Uca arcuata)、凹指招潮蟹(Uca borealis)及清白招潮蟹(Uca lactea)，和尚蟹科的短指和尚蟹(Mictyris brevidactylus)，大眼蟹科的萬歲大眼蟹(Macrophthalmus banzai)，與方蟹總科內弓蟹科的臺灣厚蟹(Helice formosensis)、秀麗長方蟹(Metaplax elegans)及相手蟹科的無齒螳臂蟹(Chiromantes dehaani)。所有物種轉移至千分之五(5 g/L)人工海水進行處理一、四及七天，以千分之三十五(35 g/L)人工海水組別作為控制組，觀察螃蟹離子調節鰓(第六對鰓)及觸角腺的鈉鉀幫浦活性變化。另外，觀察螃蟹轉移至千分之五人工海水四及七天後，血液與尿液滲透壓、鈉及氯離子濃度的變化情形。結合前人研究與本實驗結果發現，在鈉鉀幫浦活性變化部份：除了沙蟹科沙蟹屬物種外，兩種招潮蟹屬亦具有較高觸角腺鈉鉀幫浦活性。在血液及尿液離子與滲透壓組成部份發現：(1)螃蟹只能排出與血淋巴等滲的尿液；(2)部分沙蟹科及Ucididae物種能在低張環境中由尿液吸收鈉離子；(3)部分招潮蟹及沙蟹會由尿液排除氯離子。在觸角腺結構部份：短指和尚蟹觸角腺迷路型態與本實驗其他物種有明顯差異，但與親緣關係較遠的紅點黎明蟹(Matuta lunaris)及拉氏明溪蟹(Candidiopotamon rathbunae)相似，此現象還需要進一步研究。總結前人研究及本實驗結果發現，離子調節鰓(第六對鰓)鈉鉀幫浦活性值變化情形、觸角腺鈉鉀幫浦活性值高低及由尿液中吸收鈉離子的能力，可能與沙蟹總科及方蟹總科物種間的親緣關係有關。
The gills and antennal gland are known as ion-regulatory organs in crabs. From previous studies, the function of gills and the morphology of accessory respiration organs are known to be different between ocypodid and grasid crabs, which may be related to their phylogeny and their routes of terrestrial adaptation. In contrast, in studies of the ion regulation of the antennal gland, Ocypode quadrata (Ocypodidae, Ocypodoidea) were found to have high Na+, K+-ATPase (NKA) activity in the antennal gland and absorbed Na+ and had an increase of the concentration of NH4+ in urine. However, this change in NKA activity was not seen in Gecarcinus lateralis (Gecarcinidae, Grapsoidea). The aim of this study was to investigate whether the NKA activity and ion regulation of the antennal gland were different between ocypodid and grapsid crabs by including more species. In addition, a previous study demonstrated that the percent coverage of the coelomosac in the antennal gland differed among crabs; thus, the structure of the antennal gland in crabs was also examined. Eight species were examined in this study, including Uca arcuata, Uca borealis and Uca lactea (Ocypodoidae, Ocypodoidea), Macrophthalmus banzai (Ocypodoidae, Macrophthalmidae), Mictyris brevidactylus (Ocypodoidae, Mictyridae), Helice formosensis, Metaplax elegans (Grapsoidea, Varunidae) and Chiromantes dehaani (Grapsoidea, Sesarmidae). The crabs were transferred to 5 parts per thousand (ppt) for 1, 4 and 7 days and 35 ppt seawater was assigned as the control group, and the NKA activity in the antennal gland and gill 6th was examined. The osmolality and, concentration of Na+ and Cl- in the urine and hemolymph were examined in 35 ppt and at 4 and 7 days after transfer to 5 ppt. In addition to the findings of previous studies with regards to the difference in the NKA activity among treatments, I was the first to find that crabs with relatively high antennal gland NKA activity are not only in the Ocypode but also in two Uca species. Second, with regards to ion concentration and osmolality, crabs can produce only iso-osmotic urine compared to hemolymph. The Na+ absorption ability of urine in the Ocypodidae and Ucididae species may be greater than that in species of other families. Some Uca and Ocypode species excrete Cl- from urine. Third, with regards to the part of the structure of antennal gland, the morphology of the labyrinth in Mictyris brevidactylus is different compared with that of the other species in this study, but it is similar to Matuta lunaris and Candidiopotamon rathbunae which are phylogenetically distinct from Mictyris brevidactylus. This observation requires further investigation. In conclusion, the changing pattern in the 6th gill NKA activity, the NKA activity of the antennal gland, and the Na+ reabsorption ability of urine may be correlated with phylogeny among Ocypodoidea and Grapsoidea. |
