And I don't know about you, but watching Katmai crunch down on her Olympic gold medal ice treat kind of made my teeth hurt. So I thought that'd be the topic of this week's Deeper

カトマイがオリンピックの金メダルの氷菓子をパクパク食べているのを見て、歯が痛くなった。というわけで、今週のDeeperのテーマはこれだ。

Dive. Teeth. Don't forget to like, subscribe, and head down to the descriptions below for ways that you can help support the channel. It's no secret that animals have special adaptations to allow them to survive in their specific ecological niche. One adaptation is teeth.

ダイブ歯。このチャンネルを支援する方法については、「いいね！」、「チャンネル登録」、下の説明をお忘れなく。動物が特定の生態的ニッチで生き残るために特別な適応を持っていることは周知の事実である。そのひとつが歯だ。

Also, dentition is widely determined by specialized feeding habits. Let's start with sea otters. If you're a fan of this channel, then you probably know that sea otters love to eat. They typically prey on mollusks like oysters or clams, even echinoderms like sea urchins, or invertebrates like shrimp or crabs. And what do all of these animals have in common? An exoskeleton, or a hard shell. I'm going to assume that most of you already know that sea otters use tools like a rock to crack into hard shells, in a motion similar to what Katmai is doing here in this clip. But what if we don't have a rock? Sometimes, sea otters will just use their teeth.

また、歯列は特殊な食習慣によって大きく左右される。ラッコから始めよう。このチャンネルのファンなら、ラッコが食べることが大好きなことはご存知だろう。カキやアサリなどの軟体動物、ウニなどの棘皮動物、エビやカニなどの無脊椎動物を捕食するのが一般的だ。これらの動物に共通するものは何だろう？外骨格、つまり硬い殻である。ラッコが岩のような道具を使って硬い殻を割っていることは、すでにご存知の方も多いと思う。しかし、もし岩がなかったら？ラッコは歯を使うこともある。

That's the kind of stuff that would probably make a dentist cringe. But sea otters have adaptations that make this no big deal. Their molars have six roots instead of four, like ours, and they're flat and rounded, perfect for crushing. Sometimes, wild otters will even eat some of the shells. This not only provides them calcium, but something called roughage. It's very good for the digestive tract. Taken from someone who has cleaned up their fair share of otter poop, it is unique. So unique that it has its own name, Sprite.

歯医者が呆れるような話だ。しかしラッコには、このようなことを平気でできる適応能力がある。ラッコの臼歯は私たちのように4本ではなく6本で、平たく丸みを帯びているため、貝殻を砕くのに最適なのだ。時には、野生のラッコが貝殻を食べることもある。これはカルシウムだけでなく、粗飼料と呼ばれるものも摂取できる。消化管にとても良いのだ。カワウソのフンを掃除したことのある人から聞いた話だが、カワウソのフンは独特だ。スプライトという名前がついているほどだ。

Back to teeth. Let's talk about the most unique tooth in the ocean, narwhals. Also known as the unicorns of the sea because of their most impressive asset, their tusk. These tusks are actually a canine tooth that projects from the left side of the upper jaw through the lip and forms a left-handed helix spiral. Some males, about 1 in 500, actually have two tusks. Scientists are still debating and searching for the biological function of the tusk. And while the answer is still unknown, the leading theory is that it's somehow involved in a mating or breeding display because of the fact that males tend to have them more often than females. However, recent analysis has shown that the tusk is a highly innervated sensory organ with millions of nerve endings. So, it appears that this tusk is some sort of sixth sense that helps the animals feel around their dark, wintery, cold world. There are very few tusked animals in the world and only one other tusked marine mammal. It just so happens to be my favorite animal of all time, the walrus. Just like narwhals, the tusks of the walrus grow throughout their lives. They're basically modified canine teeth. They can reach about a meter in length and the root of that tusk grows very close to the sinuses in the walrus. The depth of these canine roots makes dental health for walruses extremely important because they can easily break or chip tusks. And if those tusks get a break or a chip, an infection, an abscess, that infection can very easily make its way up to the sinus and even into the brain. In the beginning of the video,

歯の話に戻ろう。海の中で最もユニークな歯、イッカクについて話そう。彼らの最も印象的な財産である牙のため、海のユニコーンとしても知られている。この牙は実は犬歯で、上顎の左側から唇を通って突き出し、左巻きのらせんを形成している。500頭に1頭という割合で、2本の牙を持つオスもいる。牙の生物学的機能について、科学者たちはいまだ議論と探求を続けている。その答えはまだ不明だが、オスの方がメスよりも牙を持つことが多いことから、交尾や繁殖のディスプレイに関わっているという説が有力だ。しかし、最近の分析によると、牙は数百

I mentioned that teeth usually have specialized functions. Most people assume that the specialized function of a walrus tusk is for fighting or sparring, but unlike narwhals, all walruses have tusks, even all the females. Walruses use their tusks as levers to basically pull their hulking bodies out of the water. Walruses are the heaviest member of the pinniped family.

歯には通常、特殊な機能があると述べた。ほとんどの人は、セイウチの牙の特殊な機能は戦いやスパーリングのためだと思い込んでいるが、イッカクとは異なり、すべてのセイウチに牙がある。セイウチは牙をレバーとして使い、基本的にその巨体を水から引き上げる。セイウチは鰭脚類の中で最も体重が重い。

This is a family that includes animals like seals and sea lions. Most pinnipeds have a unique bacteria that lives on their teeth that can cause an infection in humans called seal finger. This is something I've covered in a previous video, and if you're interested, you can find it right up here. However, I have gotten a lot of comments here and over on my Twitch channel about how we take care of animals' teeth when they live under human care. Do our animals go to the dentist?

これはアザラシやアシカなどの動物を含む科である。ほとんどの鰭脚類の歯には、アザラシの指と呼ばれる人間に感染症を引き起こす可能性のある独特のバクテリアが生息している。これは以前のビデオで取り上げたもので、もしご興味があればこちらでご覧いただけます。しかし、ここや私のTwitchチャンネルで、動物が人間の世話の下で生活しているときに、私たちが動物の歯をどのようにケアしているかについて、多くのコメントをもらっている。動物たちは歯医者に行くのだろうか？

Dental care is just as important to animals under human care as it is to people. We check their mouths every day to make sure that everything is looking good. In most of our critters, a basic open mouth present is one of the very first things that they learn. Going a step further, we can even train the animals to allow us to brush their teeth or even use a water pick to make sure that they're looking clean and healthy on a daily basis. Every animal typically gets a yearly physical from our veterinarians, and this includes a dental checkup and clean. If necessary, animals can even have a tooth pulled, like my favorite California sea lion, Senor Cinco. You can see here he's missing his bottom left canine. That was an unfortunate, unnecessary, human-caused injury of a gunshot wound. With walruses and their incredible tusks, we'll use caps. If you recall earlier, I talked about how walruses used their tusks to help them pull their enormous bodies out of the water. This, of course, causes a lot of stress on the tusk that could potentially cause injury. Often with walrus under human care, we'll put a cap on the end of their tusk that prevents them from getting damaged in the first place. In this clip, you can see me applying a cap to a very awake, very feisty baby walrus.

デンタルケアは、人間の世話をしている動物にとっても、人間と同じように重要です。私たちは毎日動物たちの口をチェックし、すべてが良好であることを確認する。ほとんどの動物にとって、口を開けるという基本的な動作は、最初に学ぶことのひとつです。さらに一歩進んで、私たちが歯を磨いたり、ウォーターピックを使ったりできるように訓練することもできます。動物たちは通常、年に一度、獣医師による健康診断を受けますが、これには歯のチェックとクリーニングも含まれます。必要であれば、私の大好きなカリフォルニアアシカのセニョール・シンコ

And that brings us back to sea otters. I mentioned that sea otters will often use their teeth to crack into hard shells. This actually helps scrape the plaque away from their teeth, keep their gums healthy as well. And this is one of the reasons that we give them ice treats. To be honest, one of the main reasons we give sea otters ice treats is because they love it. And if you'd like to see more of that, click on the shameless suggested link at the end of the video. But we also do it because ice simulates those hard shells. Crunching through that ice actually helps to remove regular buildup of plaque on sea otter's teeth. Honestly, teeth are so important, I could probably go on forever about them. I definitely didn't cover everything I wanted to. So if you have any questions, definitely drop them in the comments below or head over to my Twitch channel where I can answer them live. But for now, enjoy some clips of otters enjoying their ice treats with their impressive teeth, and I'll catch you next time. Cheers!

そしてラッコの話に戻る。ラッコは歯で硬い貝殻を割ることが多いという話をした。これは歯に付着した歯垢を削り取り、歯茎を健康に保つのに役立つ。これがラッコに氷菓子を与える理由のひとつです。正直なところ、ラッコに氷菓を与える主な理由のひとつは、ラッコが氷菓を好むからである。その様子をもっと見たい方は、ビデオの最後にある恥知らずな提案のリンクをクリックしてください。しかし私たちが氷を与えるのは、ラッコの硬い殻をシミュレートするためでもある。氷を砕くことで、ラッコの歯に蓄積した歯垢を取り除くことができるのだ。正直な

Thank you. Cute. He's like, I got you one clam treat!

ありがとう。かわいい。貝のおやつを1つ持ってきたよ！