以放射線學及超音波影像學觀察雌性柴棺龜生殖週期之變化

Abstract

目前諸多因素導致柴棺龜大量減少，且國內外對此物種的生殖生理方面研究均極為缺乏，故本研究結合非侵入性的放射線學與超音波學來進行柴棺龜生殖週期監測，不僅能建立柴棺龜的基本生殖生理資料，且對於往後的野外調查以及復育方面必能有所助益。 2006年4月份至2007年6月份期間，以27隻雌性柴棺龜進行生殖週期之監測，每月進行二次超音波探測，探測最大濾泡成長之變化，同時觀察排卵後蛋生成的過程並收集其影像，並以放射線學輔佐確認每窩蛋的窩卵數。由研究結果得知，濾泡於9月底開始成長，於12月底至隔年的1月初成長至排卵前濾泡大小（18.30 ± 1.44 mm），於3月中至8月初龜群陸續排卵，4月至8月陸續產蛋，自8月初部分龜群濾泡開始進入潛伏期，到9月底平均濾泡大小降至最低（13.22 ± 2.36 mm），而後下一個週期之卵黃生成作用於10月底開始進行，濾泡再度開始成長，如此形成一完整生殖週期。 在2006年的產蛋期間內，27隻雌龜中有24隻懷蛋，總共發現56個產蛋窩數和227顆蛋，平均每隻雌龜產2.33窩蛋（範圍1-4窩），每窩平均有4.05顆蛋（範圍1-8顆）。2007年截至6月份為止，27隻雌龜中有25隻懷蛋，總共發現50個產蛋窩數和213顆蛋，平均每隻雌性柴棺龜產下2窩蛋（範圍1-4窩），每窩平均有4.26顆蛋（範圍1-8顆）。 在排卵時期以X-ray及超音波密集監控，在排卵後6-7天可以從X-ray中發現蛋殼影像，但是窩卵數則要在排卵後7-9天才可完全確定，而後蛋殼密度會越來越大，在放射線下的影像也越來越明顯。在超音波的觀察中，排卵第一天和第二天無回音性構造的蛋白會漸漸覆上卵黃周圍，排卵會在24-48小時內完成，到排卵後第三天可開始看見薄薄的蛋殼影像，而後鈣質漸漸沉積，蛋內容物在排卵後2週後開始漸漸模糊，到排卵3週後即看不見卵黃構造。 在懷蛋時間的觀察結果，第一窩蛋的平均懷蛋時間約6.9週（範圍2-16週），第二窩蛋平均約3.4週（範圍2-8週），第三窩蛋2.75週（範圍2-6週），第四窩蛋約4週（2週和6週）。由此可知通常第一窩蛋所需的懷蛋時間比較長，而隨後的產蛋窩數的懷蛋時間隨著縮短。產蛋間隔若以排卵的時間為基準，則第一到第二窩蛋出現中間間隔的時間平均為6.6週（範圍2-12週），第二到第三窩蛋間隔為4週（2-6週），第三到第四窩蛋間隔為3週（2週及4週）。由此可推得產蛋間隔隨著產蛋窩數越多而跟著越短。 本實驗結合非侵入性的超音波以及放射線的方法來監測柴棺龜之繁殖週期，結合此二方法可以獲得濾泡週期性變化、排卵前後之影像變化、產蛋的出現與消失的概況等等，並可以得知濾泡大小與排卵產蛋之間的關係，以這些寶貴資料來建立柴棺龜正常的完整生殖生理概況，不但可提供野外調查之參考，且此監測模式也可運用於其他物種淡水龜的研究上，對於台灣原生種淡水龜基本資料的建立，及野外復育及保育上有重要的參考價值。

There were reasons that make Mauremys mutica endangered but only few researches about reproductive physiology of them were cited. We combined non-invasive ultrasound and radiology together to monitor reproductive cycle of Mauremys mutica. This study is very important for us to understand reproductive physiology of Mauremys mutica and provide great help in conservation of them. The reproductive cycle of 27 female Mauremys mutica was studied from April 2006 to June 2007. We monitored the change of largest follicle by ultrasonography twice a month to collect a series of images and also used radiology to monitor clutch size. The study comprised the annualised observation of reproductive cycle by radiology and ultrasonography. Radiology is used to monitor clutch size; while ultrasonography is utilized to monitor the change of ovaries and follicles. It reaches a conclusion that the follicles start to enlarge from September to January. Preovulatory follicles are averaged in diameter of 18.30 ± 1.44 mm. Then the ovulation occurred continually between March and August with eggs laid successfully between April and August. After oviposition, female turtles came into latent period in early August with follicles decreased to minimum of 13.22 ± 2.36 mm in late September. Later on, the vitelloginesis of next reproductive cycle proceeded since October. In breeding season of 2006, 24 of 27 adult female turtles were gravid. There were 227 eggs found in 56 clutches, therefore, every turtle had 2.33 clutches (range 1-4) and 4.05 eggs (range 1-8) per clutch in average. In 2007, 25 of 27 adult female turtles were gravid. There were 214 eggs found in 50 clutches, therefore, every turtle had 2 clutches (range 1-4) and 4.26 eggs (range 1-8) per clutch in average By intensive monitoring of radiology after ovulation, we can find egg shell image of the 6th - 7th day after the ovulation, but we accurate know the clutch size until the 7th - 9th day after ovulation. Afterward, shell would get much denser and the images of egg shell under Radiology would get much clear too. According to the intensive observation during ovulation process by ultrasonography, the follicles have ovulated within 24-48 hours. The day that we found ova secret by follicle in ultrasound was defined as Day 1. Ova were not surrounded by rich albumin and shell membrane on Day 1, and it was surrounded by anechoic albumin on Day 2, then covered with shell membrane on Day 3. On Day 3, shell images were found by ultrasonography, and calcification was processing since then. As the deposition of calcium on the shell membrane, inner content of the eggs can’t be seen clearly after 2 weeks of ovulation, and yolk and albumin can’t be observed after 3 weeks of ovulation. Therefore, it is about 17-18 days that it is in vain to observe egg’s inner content since calcium began to deposit on the shell membrane. The average of oviductal period in the first clutch is 6.9 weeks (range 2-16 weeks), 3.4 weeks (range 2-8 weeks) in the second clutch, 2.75 weeks (range 2-6 weeks) in the third clutch and 4 weeks (2 and 6 weeks) in the fourth clutch. It comes to a conclusion that longer clutch retention time was needed in first clutch, and shorter time was needed with the following clutches. The period between two ovulation time was defined as gravid interval, and the interval between the first and the second clutch is 6.6 weeks (range 2-12 weeks), 4 weeks (range 2-6 weeks) between the second and the third clutch and 3 weeks (2 and 4 weeks) between the third and the fourth clutch. As the result it revealed that the gravid interval seemed to be shorter while clutches increasing.