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Ichthyology,

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the study of fishes.

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It looks like a big, boring word,

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but it's actually quite exciting,

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because ichthyology is the only "ology"

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with "YOLO" in it.

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(Laughter)

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Now, to the cool kids in the audience,

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you already know, YOLO stands for[br]"you only live once,"

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and because I only have one life,

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I'm going to spend it doing[br]what I always dreamt of doing:

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seeing the hidden wonders of the world[br]and discovering new species.

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And that's what I get to do.

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Now, in recent years, I really focused[br]on caves for finding new species.

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And it turns out, there's lots of new[br]cavefish species out there.

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You just have to know where to look,

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and to maybe be a little thin.

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(Laughter)

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Now, cavefishes can tell me[br]a lot about biology and geology.

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They can tell me how the landmasses[br]around them have changed and moved

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by being stuck in these little holes,

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and they can tell me about[br]the evolution of sight, by being blind.

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Now, fish have eyes[br]that are essentially the same as ours.

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All vertebrates do, and each time[br]a fish species starts to adapt

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to this dark, cold, cave environment,

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over many, many generations,[br]they lose their eyes and their eyesight

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until the end up like an eyeless[br]cavefish like this one here.

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Now, each cavefish species[br]has evolved in a slightly different way,

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and each one has a unique geological[br]and biological story to tell us,

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and that's why it's so exciting[br]when we find a new species.

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So this is a new species[br]we described, from southern Indiana.

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We named it Amblyopsis hoosieri,[br]the Hoosier cavefish.

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(Laughter)

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Its closest relatives[br]are cavefishes in Kentucky,

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in the Mammoth Cave system.

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And they start to diverge[br]when the Ohio River split them

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a few million years ago.

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And in that time they developed[br]these subtle differences

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in the genetic architecture[br]behind their blindness.

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There's this gene called rhodopsin[br]that's super-critical for sight.

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We have it, and these species have it too,

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except one species has lost[br]all function in that gene,

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and the other one maintains it.

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So this sets up this beautiful[br]natural experiment

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where we can look at the genes[br]behind our vision,

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and at the very roots of how we can see.

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But the genes in these cavefishes

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can also tell us[br]about deep geological time,

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maybe no more so[br]than in this species here.

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This is a new species[br]we described from Madagascar

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that we named Typhleotris mararybe.

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That means "big sickness" in Malagasy,

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for how sick we got trying[br]to collect this species.

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Now, believe it or not,

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swimming around sinkholes[br]full of dead things

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and cave full of bat poop

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isn't the smartest thing you could[br]be doing with your life,

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but YOLO.

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(Laughter)

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Now, I love this species despite the fact[br]that it tried to kill us,

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and that's because[br]this species in Madagascar,

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its closest relatives[br]are 6,000 kilometers away,

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cavefishes in Australia.

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Now, there's no way a three-inch-long[br]freshwater cavefish

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can swim across the Indian Ocean,

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so what we found when we compared[br]the DNA of these species

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is that they've been separated[br]for more than 100 million years,

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or about the time that the southern[br]continents were last together.

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So in fact, these species[br]didn't move at all.

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It's the continents that moved them.

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And so they give us, through their DNA,

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this precise model and measure

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of how to date and time[br]these ancient geological events.

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Now, this species here is so new

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I'm not even allowed[br]to tell you its name yet,

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but I can tell you[br]it's a new species from Mexico,

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and it's probably already extinct.

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It's probably extinct because[br]the only known cave system it's from

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was destroyed when a dam was built nearby.

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Unfortunately for cavefishes,

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their groundwater habitat

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is also our main source of drinking water.

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Now, we actually don't know[br]this species' closest relative, yet.

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It doesn't appear to be[br]anything else in Mexico,

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so maybe it's something in Cuba,

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or Florida, or India.

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But whatever it is, it might tell us[br]something new about the geology

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of the Caribbean, or the biology[br]of how to better diagnose

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certain types of blindness.

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But I hope we discover this species[br]before it goes extinct too.

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And I'm going to spend my one life

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as an ichthyologist[br]trying to discover and save

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these humble little blind cavefishes

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that can tell us so much[br]about the geology of the planet

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and the biology of how we see.

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Thank you.

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(Applause)