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.
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.
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.”