Climate Change and Clownfish Incest: the future could be way weird

We’re about to hit another election, and the media is ablaze with political rhetoric. I’m an avid, maybe rabid, consumer of politics. Ask me anything about who’s running, why they’re running, which spirit animal they follow (this is Berkeley after all), and I can recite it by heart. I watch debates with the Politifact Twitter feed on my phone, I read Gawker for the latest in scandals, and I follow the local political babble like others watch soap operas. I may have a degree in biology, but political gossip is my life. In fact, I often find that the two subjects collide.

This is never clearer than when a politician cites a human sexual behavior as “unnatural”. As a biologist, I am acutely aware of what “natural” is, and it’s probably not what you expect.

A short lesson for you: there are beetles having gay sex right now in your baking flour (1), snails stab each other during sex (2) and male lobsters pee at each other in an attempt to distinguish dominance and get the ladies. And it works (3). Also, dogs eat poop. Of course this isn’t a sexual act, but as a cat lover I had to point this out. Dogs are gross.

Now, I know what you’re thinking. Why would any animal demonstrate these sexual behaviors? Do they really result in offspring (which is the point of all sexual behavior, according to some people with really boring lives)?

To you I say: tiny hats & nerd glasses. You’d think they would deflect human ladies, and yet, at the end of the night, the bar across the street from my house has loads of tiny-hatted, bespectacled gentlemen bursting out with ladies on their arms. So, like, whatever works.

More than working, though, these behaviors are vital to a species’ success. If you are a snail who abstains from stabbing your lover, well then you are just a really crappy lover. There are too many snails in the garden for any snail to waste their time with one who wouldn’t at least have the courtesy to stab them. Selfish jerk.

So behavior is important, for sex, for life, for eating, for sleeping, for fighting off predators, for being a predator, for competing for mates or territory or status or whatever. Behavior, if you’re human, dog or lobster, is central to your survival. But if you are a sea creature, climate change might start to mess with your behavior, and that could be a serious problem.

Over the past couple weeks I’ve been talking about the effect of climate change on oceans, and how it’s predicted that, as people add more carbon dioxide to the atmosphere, more carbon dioxide will accumulate in the ocean. We also discussed how this might be good for some animals, like sea anemones, because of their symbiotic relationship with photosynthesizing algae, and bad for other animals, like snails, because it could weaken their shells. But researchers have started to ask if a change in ocean carbon dioxide concentration (which will also change the ocean pH) could also alter sea animal behavior.

Now this is where we are getting into hypothesis territory, because we know that other pollutants can influence a sea animal’s behavior and sensory abilities, but CO2 is only starting to be investigated in this role (4). Clownfish in particular appear to be sensitive to elevated levels of carbon dioxide when they are “settlement-stage larvae”–little fish floating around looking for a good sea anemone to call home. In a normal environment, these larvae select a home based on odors in the water, much like I did when I first moved to the city. Big fail on my part.

Normally, settlement-stage clownfish larvae avoid places where their parents live, and seek out places where there are few predators. Makes sense right? This strategy helps avoid incest and getting eaten – rules to live by. But, when reared in an elevated CO2 environment, their ability to sense these things becomes all screwy. Rather than avoiding their parent’s scent, they are attracted to it (5) – boomerang kids or is it just Chinatown? Furthermore, they are also attracted to predator scent cues rather than avoiding them (6) – oops!

So, incestuous, suicidal clownfish? Maybe. There isn’t any evidence yet that these clownfish would actually be so confused as to mate with their parents or get swallowed up by a hungry predator. Just because their sensory systems are impacted, doesn’t mean they wouldn’t figure out the mistake and take off ASAP. It’s the early research stage – stay tuned as the story evolves.

What this does demonstrate though is that sometimes it’s not just about the habitat, or the food, or the sun, or the rain: often, an animal’s success is dependent on its behavior, and that is where they might really be screwed.

Pun intended.

Further Reading:
(1) Testing multiple hypotheses for the maintenance of male homosexual copulatory behaviour in flour beetles.
(2) The “love dart” of the snail Helix aspersa injects A pheromone that decreases courtship duration.
(3) Chemical Communication in Lobsters.
(4) High CO2 and marine animal behaviour: Potential mechanisms and ecological consequences.
(5) Ocean acidification impairs olfactory discrimination and homing ability of a marine fish.
(6) Ocean acidification disrupts the innate ability of fish to detect predator olfactory cues.

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