文 | 海生館出版中心 王玠文 圖 | 海生館展示組提供
英文翻譯 | 謝佳珊 英文審稿 | Mark J. Grygier
你是否還記得，2020年的過年，你在做什麼呢？是待在沙發上一整天？又或者是把握難得的時間出去走走呢？對於臺灣研究鯨豚的學者來說，2020年的過年，有著印象深刻的回憶。
2020年大年初一，當多數國人慶祝農曆新年到來之時，臺東長濱海灘卻發現一具擱淺藍鯨的屍體，這個消息引起了國內鯨豚專家與保育人員的注意。全世界有90多種鯨豚，在臺灣約莫可以看到33種，為世界鯨豚種類的1/3，雖然可以看到的物種頗為豐富，但在此之前，臺灣從未有過藍鯨擱淺的紀錄。
藍鯨，是目前世界上最大的生物，這頭在臺東擱淺的個體體長有20公尺，看起來雖然巨大，但牠其實還只是個寶寶。成年藍鯨的個體體長可超過30公尺，然而其龐大的個體卻阻止不了牠們面臨瀕臨絕種的命運，隨著捕鯨漁船的追趕與人們對環境的破壞，學者估計目前全球藍鯨總族群數量約莫在1萬至2萬5,000頭，屬於瀕危物種。
由於族群的數量稀少，因此關於藍鯨的各項研究資料也十分珍貴，目前全世界公開展示的藍鯨標本僅有25件。為了揭開藍鯨的神秘面紗，國立海洋生物博物館（下稱海生館）與海洋保育署以及國立成功大學為這頭擱淺藍鯨，共同簽署了「藍鯨骨骼標本合作備忘錄」，期望能將牠的骨骼重建並公開展示，透過訴說這頭藍鯨的遭遇，以喚起參觀民眾的保育意識，並加深國內外的藍鯨研究與學術交流和連結。
在擱淺臺東海岸之前，這頭藍鯨就已在海上漂流一段時間，其骨骼碎裂嚴重，因此海生館除了邀請國內鯨豚相關的學者們擔任委員外，也從國外邀請相關領域的學者一同參與，而其中也包含了山田格（Tadasu K. Yamada）老師。山田格老師是國際知名的比較解剖學大師，非常熟悉鯨豚骨骼，然而在正式投入鯨豚研究以前，令山田老師感興趣的，其實是人體解剖學。在研究的過程中，為了想更了解人類手臂肌肉的構造，他便開始轉向比較解剖學領域，從靈長類如狐猴和懒猴、到肉食動物如貓狗、還有麝鼠等生物，隨著研究漸漸深入，老師也將目光投向比較肌肉學，並開始研究爬蟲類與兩棲生物，如鱷魚和蠑螈。
陸生脊椎動物的祖先四億多年前從海洋來到陸地，雖然這些生物一直努力地適應陸地生活，不過在6,000多萬年前，有一群哺乳類生物，也就是我們熟知的鯨目動物決定重返海洋生活，從而發展出與陸地生物不同的構造。「我想知道，在生物的演化過程中，牠們為了適應海洋生活改變了哪些部分？又保留了哪些與陸地哺乳類的特徵？我對這種結構的比較很有興趣，特別是牠們肌肉與神經的演化，因此便開啟了我對於海洋哺乳類的研究。」山田老師對我們說。
哺乳類生物間擁有許多共性，比如用肺呼吸、以母乳餵養子代等等，但數千萬年以來，海洋哺乳類為了更好的適應水下生活，因此進化出與在陸地時期不同的特徵，而老師研究的熱情與動力，則來自於持續發現其中的差異。山田老師說：「許多人都以為解剖學只是拿著手術刀與鑷子剖開動物，但觀察與歸納才是最重要的。如果我們仔細觀察，並思考造成生物彼此間差異的原因，就會發現我們還有很多研究要做。」「直到今天，人類對於生物的認識還是很少，我在研究過程中，仍然時常有新發現，這也是讓我持續研究的熱情和動力。」
2020年，當人們在臺東沙灘上發現擱淺藍鯨時，牠的頭部還纏繞著尼龍繩，整體脂肪也偏少。當時研究者們就推測，這條尼龍繩可能限制其生前嘴部的開合，並影響牠覓食的能力，進而使牠比正常健康個體更為瘦弱。而在山田老師來訪期間，透過觀察發現，藍鯨的頭顱骨骼有一個寬約5公分，溝深約10公分的對稱凹陷，並有骨痂現象，這個凹陷並不來自於生物本身，而是小藍鯨在生前長時間被繩子勒著所造成的，這個發現也說明了擱淺生物在更小的時候，就被尼龍繩所困了。隨著藍鯨長大，繩索所造成的傷痕也變得越深，我們可以說這頭鯨魚長時間以來被這條繩索所折磨，最終導致牠的死亡。山田老師在採訪中也提到：「很多時候，人類為了更好的生活所製造出的物品，都對其他動物帶來一些傷害⋯⋯或許我們可以開始思考，我們的行為會產生哪些後果，並將對環境的傷害降到最低。」
最後我們問山田老師，展示藍鯨骨骼標本的困難之處為何？他回答：「要知道身體如何組成的確切知識是非常非常困難的。」「許多人可能以為骨骼展示就是把骨頭都拼在一起就完成了，但並不是這樣的⋯⋯，有些展示中的藍鯨骨骼標本加上皮膚後變得一點都不像藍鯨，在骨骼架構之外，我們也必須將外貌呈現的整體性考慮進去。因此我們花了非常多的時間討論細節，例如肋骨的角度應該是多少⋯⋯，希望能製作出全世界最好的藍鯨骨骼標本。」
採訪當天，酷熱的標本工廠中，一眾學者與工作人員圍繞著幾百公斤重的藍鯨頭骨，汗流浹背地在工作檯爬上爬下，無懼悶到令人窒息的空氣，在機械的幫助下，將頭骨以不同方向移動，試著找出最適合的角度。山田老師說：「世界上99%的人可能都不在意藍鯨的骨骼長怎樣，但那些在意的1%可能都在這個空間裡了。」
就讓我們一起期待在海生館裡看到全世界最好的藍鯨骨骼標本吧！
Do you remember what you did during the
Chinese New Year holidays in 2020? Did you stay on the couch all day, or did
you perhaps go out for a walk? For cetacean scholars in Taiwan, that was a
special holiday full of profound memories.
While most Taiwanese were celebrating the
very first day of the lunar New Year, a Blue Whale carcass was found on
Chang-bin beach in Taitung County. The news soon caught the attention of
cetacean experts and conservationists throughout the country. There are more
than 90 species of cetaceans (whales, dolphins, and porpoises) in the world,
and about 33 of them, a little more than one-third of the total, have been seen
in waters around Taiwan. Although cetaceans are quite diverse around this
island, no stranded Blue Whale had ever been recorded from Taiwan before.
The Blue Whale is welknown as the largest
living organism in the world today, and the individual found stranded in
Taitung was 20 meters long. That might seem to be a tremendous size, but in
fact it was just a calf. Adult Blue Whales can exceed 30 meters in length, but
their enormous size doesn’t protect them from the imminent threat of
extinction. Having been hunted by whaling ships and having suffered the
ill-effects of other damage to the environment at the hands of humans, Blue
Whales are currently considered an endangered species. Their global population
is estimated to be just 10,000 to 25,000.
Due to their small population, research
data about Blue Whales is very valuable, and hard to obtain. Currently, only
about 25 specimens are on exhibit around the world. To unveil the secrets of
Blue Whales, the National Museum of Marine Biology and Aquarium (NMMBA), the
Ocean Conservation Administration (OCA), and National Cheng Kung University
(NCKU) signed a Memorandum of Understanding (MOU) concerning the handling of
the skeleton of the stranded Blue Whale in Taitung. By re-assembling and
exhibiting its skeleton, people can learn what this Blue Whale calf had been
through during its brief life; their conservation awareness can also be raised.
Moreover, academic studies and exchanges about Blue Whales can be deepened,
both at home and abroad.
Because the Blue Whale calf had drifted on
the ocean for some time before stranding on the coast in Taitung, some of its
bones were severely damaged. Therefore, NMMBA invited cetacean experts from
Taiwan and abroad to take part in this project. The team includes Dr. Tadasu K.
Yamada, who is a well-known expert on comparative anatomy and extremely
familiar with cetacean skeletal structure. In fact, he was more interested in
human anatomy before becoming devoted to cetacean research. As his studies
progressed, he began to move into comparative anatomy in order to learn more
about the musculature of human arms. Since then, his studies of mammals have
covered primates like lemurs and lorises, carnivores like dogs and cats, and
even eulipotyphlas such as muskrats. As Dr. Yamada expanded his research to
make comparative myology (the study of muscles) one of his main fields of
study, he also started to work on reptiles like crocodiles and amphibians such
as salamanders.
Since terrestrial vertebrates first came
from the sea onto land 400 million years ago, their descendants continuously
tried to adjust to life ashore. However, around 60 million years ago the
forerunners of the group of mammals now known as cetaceans returned to the sea
and developed anatomical structures that are very different from those of land
mammals. “I would love to know what evolutionary changes they’ve made to adapt
to life in the oceans and which features of land mammals they have retained. I
became really curious about structural comparisons, especially concerning the
evolution of muscles and nerves, and that’s what led me to start my research on
marine mammals”, said Dr. Yamada in an interview.
All mammals have a lot in common, including
breathing with lungs and breast-feeding their young, but after millions of
years marine mammals have evolved other traits as adaptations to life
underwater. The continuous discovery of such differences provides the
motivation that drives Dr. Yamada further on in his research. “Many people
think that anatomy is just dissecting animals with scalpels and tweezers, but
in fact, observations and induction are the most important factors. If we look
closely and try to figure out how the animals differ from each other, we will
discover that there is still much work to do. Even today, we human beings know
very little about living things in the world. The fact that I often make new
discoveries while pursuing my research is what pushes me on and keeps me
motivated.”
When the young Blue Whale was found on the
beach in Taitung in 2020, a nylon rope was wrapped around its head, and its
supply of body fat was relatively low. Researchers speculated that the rope
might have constrained its mouth’s ability to open and close, affecting its
ability to feed and thus causing it to become thinner and weaker. Dr. Yamada
found a symmetrical groove in its skull that was 5 cm wide, 10 cm deep, and
covered with bony callus. Such a groove is not typical for this species; instead,
it is evidence that the stranded whale calf had been entangled since it was
much younger. As the whale grew, the scar made by the rope became deeper. One
could say that the whale was slowly tortured to death by this loop of rope over
a fairly long time. “Things we create for a better and more convenient life
mostly have negative impacts on other animals. Maybe it’s about time for us to
evaluate the consequences of our behavior and try to minimize damage to the
environment”, said Dr. Yamada during the interview.
The final question for Dr. Yamada was
“What’s the hardest thing about displaying a Blue Whale skeleton?” He told us
that it is extremely difficult to know how the body should look. “Many people
might think it’s just a matter of putting all the bones together, but that’s
not the case at all. Some of the Blue Whale skeletons on display just doesn’t
look like a living Blue Whale at all, if you put the skin on. Besides the bony
structure, we also need to take the overall appearance into consideration. That
is why this time we’ve spent a lot of time on details, such as the angle of the
ribs, in order to produce the best skeletal specimen of a Blue Whale in the
world.”
This interview took place in a heated
specimen workshop where a group of experts and staff were surrounding a giant
Blue Whale skull that weighed several kilograms. Regardless of the suffocating
air, they climbed up and down around the worksite and moved the skull in
different direction with help of machinery to find the most appropriate angle.
“99% of the people in the world might not care how Blue Whale skeleton looks,
but the 1% who do care might all be here right now,” Dr. Yamada joked.
Let’s look forward to seeing the best Blue
Whale skeleton exhibit ever, in NMMBA!
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