Mesmerizing Marine Mimics: Wolves in Sheep’s Clothing

This post is the fifth in a six post series outlining the evolution of mimicry within the ocean realm. These posts detail various ways in which organisms may copy other organisms in appearance and behavior, and the evolutionary context for how these mimic-model pairings have come to be. The first entry in this series goes over some fundamental introductory concepts and definitions regarding mimicry in general.

Animals can be real dicks.

Hermit crabs congregate solely to aggressively covet bigger and better shells, eventually leaving at least one or two crabs forcefully foreclosed upon and left to wander the beach, squishy, defenseless, and homeless. Lovable dolphins routinely slaughter porpoises that stray too close to their turf, but not without sexually assaulting and mutilating them first…you know, just because. Male mallard ducks are such a charming combination of unhinged sexual aggressiveness and zero regard for consent that females of the species have evolved vaginal labyrinths to stymie the effectiveness of the penetration of the corkscrew Johnsons of their feathered assailants. The natural world is chock-full of organisms being outright bastards to one another, because life is rough, and sometimes those that are more Shkreli than Gandhi scam and abuse their way to evolutionary success. In the river of Life, the fork that yields survivorship, high fecundity, and a strong genetic legacy is typically navigated by a very special variety of watercraft: the douche-canoe.
The phenomenon of mimicry is certainly not immune from nefarious applications, and many taxa use mimicry to gain the trust of other species, only to con them…potentially out of their lives. This flavor of mimicry, where an organism mimics a species perceived by others as benign (or even beneficial) to gain access to resources (food, mating opportunities, etc.), is called “aggressive mimicry.” I’ve brought it up briefly before in this post series, in particular when talking about fish that use lures to persuade prey to practically swim into their waiting gobs, like with the decoy scorpionfish or the frogfish. However, there are some marine critters that take the cake when it comes to the Machiavellian style of mimicry. The fish that this blog post will explore shamelessly engage in as much sociopathy, brazen laziness, selfishness, and manipulative scheming as you’ll find this side of an episode of “It’s Always Sunny in Philadelphia.”

Take, for example, the hamlet fishes (genus Hypoplectrus), a collection of small, typically brightly-colored groupers found in the tropical West Atlantic and Caribbean. Hamlets are ridiculously tiny by grouper standards, considering the largest members of the family can grow as large as a smart car, but are nonetheless incredibly competent, voracious predators, snapping up small crustaceans as they patrol the maze of the reef. Sneaking up on wary prey, and keeping it wonderfully oblivious until the very last moment, is a difficult task for any predator, so it pays to be able to get close with minimal effort….and it’s thought that a few species of hamlet have managed to do just that.

The living police car beacon light below is the blue hamlet (Hypoplectrus gemma). It, like the other hamlets, grows to a handful of inches and has a face only a mother could love.


I haven’t seen a hamlet this blue since the Prince of Denmark fondled a jester’s skull

Hypoplectrus gemma just so happens to share its Caribbean and Gulf of Mexico geographic range with another fish, the blue chromis (Chromis cyanea). Chromises are damselfish (family Pomacentridae) and have a diet generally consisting of tiny, suspended particles of food in the water column. While they can be cantankerous, bitey little pricks in regards to defending their territory and eggs from other fish, damselfish, with their tiny mouths perfectly suited to pecking at planktonic flakes, aren’t exactly the predatory scourge of the reef. The blue chromis is no exception.


Pictured: Probably not a shark

For this reason, the small crustaceans on the reef (shrimp, crabs, and the lot) don’t have much to fear from the blue chromis. What they do shit their ten-legged pants over are hamlets, which are ever-hungry Bubba Gump addicts with (much like other predatory fish) a mouth that sucks harder than a DVD of “Transformers: Age of Extinction” taped to a Bissell. If they sense the clear presence of a hamlet, wiser crustaceans make sure their exoskeletal asses are well hidden in the smallest grooves and pores in their coral surroundings. So it’s a good thing for the blue hamlet that it, as you may have noticed, looks remarkably similar to the comparatively harmless blue chromis. It’s thought that to the common crustacean on the reef, with simple eyes unable to discern fine details, the blue hamlet is basically indistinguishable from a blue chromis….allowing the hamlet to leisurely approach its crustacean prey without raising any red flags. From the perspective of the shrimp, an inoffensive little damselfish, barely worth considering, is just drifting into its personal space…like a fly casually landing next to you on a park bench. You may not even register that the fly is inches away from your leg. Why would you? Flies aren’t dangerous, incredibly common, and there’s not really any reason to notice them at all. If that fly promptly swallowed you in one tremendous gulp, you wouldn’t be able to say you saw it coming. The same goes for the shrimp and the “damselfish” that floated over to say hi. It’s possible that taking advantage of the reputation of the blue chromis as an inconsequential wallflower allows the blue hamlet to cruise through its predatory life with the difficulty setting on “easy”, feigning innocence long enough to straight up murder meal after meal after meal.

I say it’s “possible” that this is the case, because no one, to my knowledge, has actually confirmed behavioral mimicry in this species of hamlet, and the level of mimicry in blue hamlets (and a number of other hamlet species that are proposed to mimic different types of damselfish) appears to be limited to severely suspicious similarity in color and appearance between the mimic and the model. Well, with the exception of one hamlet species. The butter hamlet (Hypoplectrus unicolor) is an apparent mimic of the four-eyed butterflyfish (Chaetodon capistratus)…a fish that you may remember from the last post in this series as being an automimic, flashing confusing eye spots when confronted with danger (yes, the model for the butter hamlet’s mimicry is in fact another mimic). Butter hamlets not only wear their model’s colors, they also follow the butterflyfish around the reef like a puppy in an attempt to blend in more effectively (possibly appearing to be the butterflyfish’s mate). The hamlet also uses this convenient opportunity tagging alongside the butterflyfish to try and suck up as many crustaceans as possible….in fact, about half of all the hamlet’s predatory strike attempts are made when it is using its model as a unwitting wingman. The butter hamlet apparently hardly goes through the effort of trying to eat unless it is actively mooching off the presence of its model to further dupe its prey. These fish are about as principled as the guy who fakes homelessness to gain access to a food pantry so they can pocket as much grub as possible before dashing out the door.

It’s one thing to fly under the radar as an uninteresting, benign reef fish in order to score your dinner. It’s something entirely different to convince your meal that not only are you harmless, but that you are their friend. That you are there to help.

Really.

Just a big ol’ pot of altruism you are. Honest….

Ocean ecosystems are a cauldron bubbling over with life: fish flitting and spawning everywhere, countless organisms living, pooping, and dying, vast fields of pelagic plankton converting carbon dioxide and nutrients into grand scale blooms. The sea is like a well-used, never cleaned, fraternity hot tub at the end of a long, sweaty, rambunctious summer; crusty, high in biodiversity, and swimming with critters you’d rather pretend aren’t in there. Life, just by existing in this saline soup, tends to have other life invade, infect, and coat it liberally; there is no escape. External parasites are pervasive in the marine realm, and cling to the outside of larger animals with a stubborn, death-grip of permanent stickiness only outmatched by what fucking glitter does whenever it comes in contact with human skin. These irritating stowaways, often times blood-sucking crustaceans like sea lice and roly-polies that live like leeches, aren’t exactly an appreciated gift of the sea by the animals that have to deal with their shit. Parasites drain precious energy and resources along with the blood they sip, and in the unforgiving wild, having an assload of freeloaders drinkin’ up your go-juice is a fine way to have your anemic keister end up deader than it was last week. Simply put, parasites end up weakening their hosts…so it behooves the besmirched, non-consenting smorgasbords to have them removed. Oh if only such a means existed…

Stepping up to the plate is a fish that specializes in making itself incredibly useful to the other fish in its community; the cleaner wrasse (Labroides). Labroides wrasses, of which there are five species, are known as “cleaner fish” (which is a role held by more groups of fish than just these wrasses), meaning that they prune and pick parasites off the scaly outsides of other fish. Cleaner fish don’t do this bit of public service as part of getting their Goody Two-shoes Badge in the Neptune Scouts or something…they get the bulk of their nutrients from the parasites and mucus layer on other fish. The tiny, vibrantly-colored, finger-shaped cleaner wrasses are widespread, common cleaners in tropical Indo-Pacific reef ecosystems, and many species of fish across the region are quite familiar with their grooming-focused diet. Not only do reef fish tolerate the little buggers coming up and nipping at their flanks (oxpecker style), but they will actively seek them out. Cleaner wrasses (along with other cleaner species) will typically hang out in specific areas on the reef that quickly become “cleaner stations” where scores of fish, of all taxonomic stripes, congregate to get all spruced up. The wrasses will bob and dance in a distinctive fashion to get the attention of potential “client” fish, and to advertise that the station is officially open for business. A client fish will usually signal to the resident shopkeep’ that they’re ready to be pampered by making a slow approach, articulating and tilting their fins and body, and opening up their mouth. The wrasse gets the message that this much larger fish is providing a meal, not looking for one, and it (and others) descend, darting around the outside, gills, and in the mouth of the client, clipping off whatever parasites they can find (along with some mucus and dead tissue as a bit of bonus flavoring).


“Is that…a tip jar? Are you serious? I’m literally feeding you two right now.”

Nasty, toothy, predatory fish like eels and needlefish, which can easily snap up the cleaner wrasse in a blink, patiently allow the world’s hungriest dental hygienist to get halfway into their throats to make everything sparkle. But, they trust that the benefits of having these eager exterminators going to town on their afflicted areas greatly outweigh the drawbacks of neglecting to take an easy meal. The clients trust they aren’t being taken advantage of, and the cleaner wrasses are confident they won’t be gobbled up while on the job…and this little symbiotic economy trucks on and on in near-harmony.

Well, kind of. Here’s the part where a third party throws a giant, douchey wrench into the mix.

Take a look at this cleaner wrasse:

This is Labroides dimidiatus, the bluestreak cleaner wrasse. It is common on reefs ranging from East Africa all the way out to French Polynesia in the South Pacific.

Now, look at this next fish, and look closely, because this fucker is the reason we can’t have nice things:

The fellow with the self-satisfied little smirk up there is not a bluestreak cleaner wrasse. It’s not even in the genus Labroides. Hell, it’s not even a wrasse. This fish is a variety of combtooth blenny, and therefore hails from a completely fucking different family from the cleaner wrasses. It’s known as Aspidontus taeniatus, the false cleanerfish, and as you may have figured out by now, is a convincing mimic of the bluestreak cleaner wrasse, just based on physical appearance alone.

‘But why mimic a cleaner wrasse?’, you may be thinking. Are the wrasses poisonous? Does looking like a cleaner wrasse allow them to escape predation? The answer to that is technically yes, but not for the reason proposed in this hypothetical train of thought.

Think of it this way: cleaner wrasses are popular. Among reef fish, they are highly-regarded. Trusted. Their particular set of skills and associated reputation has earned them the distinct privilege of unlimited access to piscine personal space. Surely, if another species were to disguise themselves as one of these pillars of the community, they would be able to get all up in larger fish’s business without issue. They could get as close as they wanted, and do whatever they wanted, all while never being hassled by predators.
While this initially sounds like a typical case of Batesian mimicry (mimicry to save one’s own ass from being eaten), and it mostly is, the false cleanerfish just couldn’t leave it at that. False cleanerfish, on occasion, exploit having the keys to the kingdom and decide to skim a little action off the top…and by that, I mean they tear chunks of skin and flesh out of their “clients” as a small tax for their delightful companionship.

Yes, this blenny capitalizes on the trust of its “clients” by not only being perceived as too damned important to be eaten, but also by periodically nibbling on these same fish like they’re big, living, traveling pantries.

False cleanerfish pull this off by managing to imitate the “wrasse wriggle” of their less bitey model in the middle of the cleaning station. When a client fish poses for some, er, oral service, the cleanerfish glides on over….probably giving itself a disquieting chuckle as it closes in. If the mood suits it (something that occurs perhaps one fifth of the time), the false cleanerfish then uses this golden opportunity to open its dainty little mouth, and drive a pair of hooked fangs up into an exposed sheet of fin from their seat in the lower jaw. This grand display of violent double-crossing apparently works best on juvenile client fish, as the adults have had a lifetime to figure out the subtle differences between the real deal and the filet-o-fraud that has a good chance of doing nothing but leaving behind a bloody, regret-shaped hole in a fin. It’s kind of like how the Internet looks very different to someone using it for the first time, and someone who’s been immersed in it for well over a decade: to a first-time user, sidebars and headers are full of a dizzying array of flashing and total convincing notifications of prize winnings you (somehow) are bound to receive (one click ahead!) and panicked, 5-alarm warnings about computer viruses you need to eradicate RIGHT NOW (…also one click ahead)….but to the Internet veteran, they’re savvy enough to recognize that these are all skeevy, predatory landmines littering a road to nothing but malware hell and digital herpes.
Many adult client fish have been burned by this used car salesman of the sea once or thrice before, and won’t let the little prick get close enough. But wide-eyed youngsters, not yet jaded and suspicious, are more likely to be successfully victimized.

Of course, fish don’t exactly write scathing Yelp reviews of their disappointing, painful encounters with these incompetent, overly-aggressive parasite-removers to tell other fish to beware and take their business elsewhere. Word doesn’t get around. So, if the false cleanerfish isn’t overzealous with the frequency of its biting behavior, there should always be a crop of innocent minors to teach, in a phenomenally direct fashion, that the world exists to completely fuck you over.

Then again, such client fish could have it worse. They could be damselfish. Specifically, damselfish that have to deal with the nightmarish psychological terrorism provided by the dusky dottyback (Pseudochromis fuscus).

Dusky dottybacks are found in the rich, vibrant, hyper-diverse coral reefs of the eastern Indian Ocean and southwestern Pacific and off the northern coasts of Australia. They, like all dottybacks (family Pseudochromidae), are diminutive, active predators that zoom around the reef and make a living fitting whatever they can into their insatiable jaws (usually crustaceans and tiny fish).
They also come in a wide variety of colors. Dottybacks in general exhibit eye-frying levels of super-saturated color (just take a look at the orchid dottyback) and there is great diversity in this coloration….but this tends to be between species of dottyback. Dusky dottybacks have distinct color morphs, ranging from yellow, to brown, to pinkish, to orange, and gray.
Conveniently, different color morphs appear to match up with the coloration of whatever species of damselfish (Pomacentrus) the dottybacks hang out around….which also tends blend in with the color of the coral backdrop in that area. Yellow damsels (like the lemon damselfish, Pomacentrus moluccensis) hanging out in yellow-y reef areas are accompanied by yellow-morph dottybacks. Brown damsels (like the Ambon damselfish, Pomacentrus amboinensis) in duller reef habitats also have brown-morph dottybacks loitering nearby, and so on. While blending in with the coral reef benefits both damselfish and dottybacks by making them less likely to be seen by big, fishy eating-machines and gobbled up like a handful of Skittles, the angle that the dottyback ends up working involves something far more sinister than just staying out of danger.


Really? The thing that looks like Steve Buscemi reincarnated as a betta isn’t trustworthy? You don’t say…

You see, being the same color as the coral around you is dandy and all, but from the dottyback’s perspective, the real magic is in looking like the damselfish that you keep company.

Dusky dottybacks blend in among their dim-witted damselfish schoolmates effortlessly. The damselfish accept their likewise-colored comrade as one of their own, and hardly pay the dottyback any mind. Sure, damselfish are notoriously territorial (towards their own species and others), but when their watery, slack-jawed gaze sees the dottyback in their midst, the damselfish may as well be looking in a mirror. The damselfish sees just another member of its tribe, completely failing to comprehend that a silent agent of Death has infiltrated their ranks.
The dottyback isn’t wearing its finest damselfish suit to conduct an undersea drug sting, or to romance a damsel-lady from the other side of the tracks (which is pointless, son; you come from different worlds! A damsel can’t love a dotty! She’ll eventually find out your secret, and while she can accept you for who you are, she’ll be crushed that you lied the entire time! It’ll end in heartbreak! HEARTBREAK!)….no, none of this.

The dottyback is there to stalk. To hunt. To feed. Not on shrimp, or mollusks, or a crop of sea squirts.
The dusky dottyback is there to kill and eat young damselfish. Yes, like some monster out of one of the more fucked up Grimm fairy tales, this scheming fish passes itself off as the adult neighbors (and, less likely, parents, aunts, uncles, etc.) of clueless damselfish children purely to get close enough to dine on their tender baby-flesh.


A 17th-century depiction of the patron god of dottybacks, Kronos, om-nom-nomming the everloving shit out of a baby

Dusky dottybacks hardly even register in the minute-to-minute perception of juvenile damselfish and their adult counterparts, and certainly aren’t considered a threat…until it’s way, way too late for the Pomacentrus pre-schoolers.

This cunning method that allows remorseless butchering of the small and naive, works out great for the dottyback, stealthily filling its belly, and increasing the average age of its host damselfish collective, in plain sight…but the mind-fuckery experienced by these young damselfish must be beyond compare. When the pedophagous Judas rolls into town, and you can’t trust any local adults to not fucking eat you when you aren’t paying attention, life must be a waking night-terror.

But wait, it gets better. The different color morphs of dusky dottybacks that target specific varieties of damselfish aren’t locked in. The dottybacks can actually change their color, and move back and forth between color morphs….allowing them to mimic and prey upon the kids of multiple species of damselfish. A brown-morph dottyback can turn into a yellow-morph dottyback (and vice versa), for example, in just a couple weeks after moving in next door to some yellow damselfish. Once enough of its brown pigment cells in its skin convert to yellow pigment cells to where it matches the color of its damselfish neighbors, the dottyback’s pride-n-joy predation success rate triples.


Two different species of damselfish on top; dusky dottybacks on the bottom, cosplaying their way up the food chain

The dottyback’s serial, infanticidal deception has been described as a strategy akin to what is employed by the specious lupine in the “wolf in sheep’s clothing” fable. However, given the plastic, color-changing element at play here, the dottyback is more like a wolf in sheep’s clothing that incrementally eats all the lambs in one flock….then takes off its sheep disguise, trading it for “cow’s clothing”….then sneaks into the next field over to switch to eating veal for a while….and so on…each new field with more and more missing babies…

It’s possible that the zeal of the dusky dottyback’s attacks on Pomacentrus pipsqueaks makes ditching the ruse and starting over in a new area dominated by another species of damselfish completely necessary. The dottybacks may be sly, but not all of their strikes are a success, and many juvenile damselfish escape. Considering that dottybacks attempt to nab their nubile prey really damned frequently, there’s a steep learning curve among survivors as to figuring out which grown-up in town is the one to stay the hell away from. It may be that after a certain point, every remaining young damselfish in the bunch has narrowly escaped death enough times that the effectiveness of the dottyback’s disguise goes to shit, and the devious bastard has to shamble out of the community and set up shop in an area nearby that is ignorant of its reprobate plans, like some kind of stereotypically shifty drifter or something.

Life can be shitty, and full of shitty people, but remember that in the ocean, the resident assholes take things to a level you’re (hopefully) never going to experience. Be glad that even though you may have paid far more for that TV you picked up at Best Buy (despite what the sales representative convinced you of) than it was worth, at least he didn’t go false cleanerfish on your ass and bite your arm and steal your wallet as well. Also, be content in knowing that even if your parents are being passive aggressive and manipulative, you’ll never have to worry about your mom actually being some ravenous psychopath in a mom skin-suit who tries to cannibalize you in the kitchen when you visit for Thanksgiving….dottyback style.

This post series will continue: Part 6 will focus on fish that disappear into their surroundings as completely as Gene Hackman did from the entire world…

Image credits: Intro image (blue hamlet), 2nd blue hamlet, blue chromis, cleaner wrasses servicing a rockmover wrasse, bluestreak cleaner wrasse, false cleanerfish, dusky dottyback (brown morph) (Paddy Ryan), Saturn (Kronos) Devouring his Son by Peter Paul Reubens, dottyback/damselfish set (clockwise from top left: Ambon damselfish, lemon damselfish, brown dottyback (John E. Randall), yellow dottyback (John E. Randall))

© Jacob Buehler and “Shit You Didn’t Know About Biology”, 2012-2015. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Jacob Buehler and “Shit You Didn’t Know About Biology” with appropriate and specific direction to the original content.

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2 thoughts on “Mesmerizing Marine Mimics: Wolves in Sheep’s Clothing

  1. Awesome articles, and so many good sentences! 🙂

    “In the river of Life, the fork that yields survivorship, high fecundity, and a strong genetic legacy is typically navigated by a very special variety of watercraft: the douche-canoe.”

    • By the by, I don’t believe I didn’t remember this earlier, but there are some amazing cichlids in the rift valley that have some really great mimicry behaviors, including one that copies a perfectly harmless sand-filtering one (by pretending to eat sand) before zooming in for the kill, another that plays dead, another that buries itself in the ground, and many more (there was a really good Mutant Planet episode that blew my mind a little)

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