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  • What you're looking at isn't some weird x-ray.

  • It's actually a baby yellow tang surgeonfish at two months old.

  • And you thought your childhood was awkward.

  • But here is the same fish as an adult,

  • a beautiful inhabitant of the Indian and Pacific Oceans' coral reefs

  • and one of the most popular captive fish for salt water aquariums.

  • Of the 27,000 known fish species, over a quarter live on coral reefs

  • that make up less than 1% of the Earth's surface.

  • But prior to settling down in this diverse tropical environment,

  • baby coral reef fish face the difficult process of growing up on their own,

  • undergoing drastic changes, and the journey of a lifetime

  • before they find that reef to call home.

  • The life cycle for most of these fish

  • begins when their parents spew sperm and eggs into the water column.

  • This can happen daily, seasonally, or yearly depending on the species,

  • generally following lunar or seasonal tidal patterns.

  • Left to their fate, the fertilized eggs drift with the currents,

  • and millions of baby larvae hatch into the world.

  • When they first emerge, the larvae are tiny and vulnerable.

  • Some don't even have gills yet and must absorb oxygen

  • directly from the water through their tissue-thin skin.

  • They may float in the water column anywhere from minutes to months,

  • sometimes drifting thousands of miles across vast oceans,

  • far from the reefs where they were born.

  • Along the way, they must successfully avoid predators,

  • obtain food, and ride the right currents to find their way to a suitable adult habitat,

  • which might as well be a needle in vast haystack of ocean.

  • So, how did they accomplish this feat?

  • Until recently, marine biologists thought of larval fish as largely passive drifters,

  • dispersed by ocean currents to distant locales.

  • But in the last 20 years, new research has suggested

  • that larvae may not be as helpless as they seem,

  • and are capable of taking their fate in their own fins

  • to maximize their chances of survival.

  • The larvae of many species are unexpectedly strong swimmers,

  • and can move vertically in the water column to place themselves in different water masses

  • and preferentially ride certain currents.

  • These fish may be choosing the best routes to their eventual homes.

  • When searching for these homes,

  • evidence suggests that larvae navigate via a complex suite of sensory systems,

  • detecting both sound and smell.

  • Odor, in particular, allows larvae to distinguish between different environments,

  • even adjacent reefs,

  • helping guide them toward their preferred adult habitats.

  • Many will head for far-flung locales miles away from their birth place.

  • But some will use smell and other sensory cues

  • to navigate back to the reefs where they were born,

  • even if they remain in the larval stage for months.

  • So, what happens when larvae do find a suitable coral reef?

  • Do they risk it all in one jump from the water column,

  • hoping to land in exactly the right spot to settle down

  • and metamorphose into adults?

  • Not exactly.

  • Instead, larvae appear to have more of a bungee system.

  • Larvae will drop down in the water column to check out a reef below.

  • If conditions aren't right, they can jump back up

  • into higher water masses and ride on,

  • chancing that the next reef they find will be a better fit.

  • But this is the point where our knowledge ends.

  • We don't know the geographic movements of individual larva for most species.

  • Nor do we know which exact environmental cues and behaviors they use

  • to navigate to the reefs they will call home.

  • But we do know that these tiny trekkers

  • are more than the fragile and helpless creatures

  • science once believed them to be.

  • The secret lives of baby fish remain largely mysterious to us,

  • unknown adventures waiting to be told.

What you're looking at isn't some weird x-ray.

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TED-ED】赤ちゃん魚の秘密の生活 - エイミー・マクダーモット (【TED-Ed】The secret lives of baby fish - Amy McDermott)

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    陳少康 に公開 2021 年 01 月 14 日
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