Amazing reef fishes

July 11, 2012 • 8:28 am

The Evolution meetings are over, and I’m heading home tomorrow, spending today in Ottawa to visit friends. Because of that, and other exigent tasks, posting will be light.

But thanks to pinch-blogger Matthew Cobb, who directed me to these pictures of stupendous reef fish. Those fish comprise some of the world’s most beautiful and bizarre animals.

Have a look at some of these spectacular fish from a new book, Reef Fishes of the East Indies by Gerald Allen and Mark Erdman (University of Hawaii Press); the book’s photos are excerpted in The Guardian, which adds:

A new book, Reef Fishes of the East Indies, is the culmination of a combined 60 years’ work to document the biodiversity of the hugely diverse coastal waters of the region. The three-volume publication features the 2,631 known reef fishes of the Coral Triangle, including 25 species new to science.

Non-new species: Pteroidichthys amboinensis – an unusually coloured specimen of the Ambon scorpionfish. Photograph: Roger Steene/Conservation International.

I wonder what the eyespots in the photo below are for. Could they be mimicking an octopus to ward off predators? And what about those strangely colored and shaped fins?

Some male cichlid fish have spots on their anal fins that mimic the female’s eggs. Female cichlids are often mouth-brooders, who lay eggs and then gather the unfertilized eggs into their mouths to protect them. When they see the spots on the male’s anal fin, they think they’ve lost an egg, and swim up to the male’s posterior end, opening their mouth to retrieve the supposedly stray egg. When they do that, the male squirts sperm into the female’s mouth, fertilizing her eggs. This is one example of mimicry in which members of one sex fool members of another.

Non-new species: Signigobius biocellatus. Photograph: Gerald Allen/Conservation International.
Non-new species: Synchiropus splendidus. Mandarinfish of the dragonet family mate just before sunset. The pair meets and swims slow spirals off the substrate. At the apex of their ascent they release sperm and eggs then dash back to the protection of the bottom. Photograph: Jones/Shimlock. Secret Sea Visions /Conservation International.
Non-new species: Antennarius commersoni – a frogfish spawning and then releasing a floating egg raft. Photograph: Roger Steene/Conservation International.

In contrast to many freshwater fish or open-water marine fish, reef fish are often arrayed in dazzling colors and patterns. Why is that?
Well, we don’t really know, but, as a piece by Greg Laslo emphasizes, what we see when we look at these fish may be very different from what the fish see, since their color sense may be very different from ours and they also see in the ultraviolet.

Since the fish are not sexually dimorphic in pattern and color (males and females usually look alike), it probably isn’t a result of sexual selection. I suspect, as does Laslo, that it facilitates interspecific communication.  But this is simply one of those ubiquitous phenomena that we don’t understand. Laslo gives a quote from biologist Gil Rosenthal, an acquaintance of mine and an avid diver:

“The conventional explanations for why they are colorful don’t really work,” Rosenthal says. Bright colors are useful to advertise that the species is dangerous or bad-tasting — for example, poison dart frogs in the Amazon and coral snakes or monarch butterflies in North America. So, too, in some fish — the butterflyfish has spines, and the scorpionfish will display colorful pectoral fins when they’re frightened. And while that’s all well and good, most brightly colored reef fish are actually pretty tasty. At least to humans. Bright colors could also help fish attract mates. For instance, in birds, brightly colored male peacocks are perhaps the best example, but that doesn’t work with most fish. For example, in Picasso triggerfish and Queen angelfish, the males and females are equally colorful, and you can’t tell them apart by looking at them.

“There isn’t going to be just one explanation, that’s the bottom line,” [George] Losey says. “There are going to be a lot of contributing factors.”

New species: Ptereleotris rubristigma – a blue dart fish named for the prominent red spot on the gill cover. Widespread throughout the East Indies region and found on soft bottoms exposed to currents. Photo by Gerald Allen/Conservation International.
New species: Lepidichthys akiko – a candy-striped clingfish known only from deep reefs of Cendrawasih Bay in West Papua. Photo by Gerald Allen/Conservation International.
New species: Pterapsaron longipinnis – A deep reef species (below 60m depth) discovered in Cendrawasih Bay in West Papua. The name refers to the unusually long pelvic fins which this fish uses to rest on the bottom in tripod-like fashion. Photo by Gerald Allen/Conservation International.

16 thoughts on “Amazing reef fishes

  1. They are really fabulous. What a wonderful puzzle, trying to work out the reason(s) for the coloration. Presumably there are piscine biologists working on fish vision?

    Yes – there is this recent textbook article; Marshall, N.J. and Cheney, K. (2011). Color vision and color communication in reef fish. In A. P. Farrell (Ed.), Encyclopedia of fish physiology: From genome to environment (pp. 150-158) San Diego, CA, United States: Academic Press
    http://espace.library.uq.edu.au/view/UQ:268505

  2. what we see when we look at these fish may be very different from what the fish see, since their color sense may be very different from ours and they also see in the ultraviolet.

    I’d also be curious to know the color sense of their predators (which may be each other, for all I know). Maybe bright colors are a fairly neutral mutation for that ecosystem.

  3. I’d guess that reef fish wear bright colors for much the same reason that sports teams do: so that from a distance, you can easily pick out your teammates from the crowd.

  4. “Some male cichlid fish have spots on their anal fins that mimic the female’s eggs. Female cichlids are often mouth-brooders, who lay eggs and then gather the unfertilized eggs into their mouths to protect them. When they see the spots on the male’s anal fin, they think they’ve lost an egg, and swim up to the male’s posterior end, opening their mouth to retrieve the supposedly stray egg. When they do that, the male squirts sperm into the female’s mouth, fertilizing her eggs. This is one example of mimicry in which members of one sex fool members of another.”

    Love it.

    A designer deity came up w/ this gene spreading method, huh? Oh yea, a designer deity was responsible all right.

    Stenger makes comparable observations about the cosmos. Each, he says, is nearly iron-clad proof that there never was a deity in charge. Either that, or it’s proof positive that the deity is the stupidest engineer in the history of designer deities.

  5. Hang on a minute, Jerry, how can Matthew be a ‘pinch-blogger’, if this website ain’t a blog? 😉
    But cool photos, though!

  6. When an already dead mandarinfish is put into formaldehyde, the formaldehyde turns blue. I have always understood that blue colors in aminals was the result of refraction. Has anyone looked intp the mandarinfish blue pigment?

    1. I don’t know about mandarinfish, but a number of sea snails produce blue pigments (chemically related to indigo) that have been used as dyes since ancient times.

      1. Indeed, mainly 6,6′ dibromoindigo. I was surprised to learn from Wikipedia just now that while Adolf von Baeyer won the Nobel Prize in Chemistry in 1905 for the chemical synthesis of indigo (which historically had come from plants), the Tyrian purple of shellfish fame has never been synthesized commercially.

  7. 1) It would be interesting to know if the genetic machinery involved in producing the eyespots on Signigobius biocellatus is at all related to that in any of the numerous moths/butterflies with similar-appearing spots.

    2) The Antennarius commersoni shot ought to be popular among tropical fish fans in Sweden.

    3)

    When they see the spots on the male’s anal fin, they think they’ve lost an egg, and swim up to the male’s posterior end, opening their mouth…

    Oral sex in lower vertebrates!!

    1. You beat me to it on the Signigobius. 🙂
      I was immediately reminded of the Automeris silk moths. I was taught that the eyespots on the hindwings of these moths might have a “startle” effect on a predator when the resting moth suddenly exposes the hindwings.

      When the moth is flying, the spots may deflect the predator’s attention away from the vulnerable head and abdomen and toward the wing which would be less critically injured in an attack. I’ve seen several moths with slivers missing from the eyespotted part of the wing. I think this idea might work for the fish’s dorsal fins, too. Anyway it’s a lovely creature – they all are. I love the red and white striped clingfish.

  8. Beautiful. Show sum luv to the coral reefs hoomins, save their colourful snacks for future generations of kitties. Yours sincerely, Ceiling Cat.

  9. “Since the fish are not sexually dimorphic in pattern and color (males and females usually look alike), it probably isn’t a result of sexual selection. I suspect, as does Laslo, that it facilitates interspecific communication.”

    If reef fish rarely encounter one another, this could just be sensory bias. If two reef fish can more easily spot one another from a distance, instead of wondering around aimlessly, 50% of the time one may encounter a member of the opposite sex.

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