Ever wondered what kinds of wildlife dominate the world’s seas and oceans? Now there’s an answer, at least in terms of the number of species in different categories. It’s not fish. It’s not mammals. It’s crustaceans!
A mammoth Census of Marine Life has revealed that nearly one-fifth, or 19 percent, of all the marine species known to humans are crustaceans — crabs, lobsters, crayfish, shrimp, krill, barnacles and others far too numerous to mention here. The census didn’t count the actual numbers of animals beneath the waves — that would have been impossible — but it did count up the number of species in 25 marine areas. The aim is to set down a biodiversity baseline for future use.
It took 360 scientists to figure this out. Their findings were posted on Monday in PLoS ONE, an open-source peer-reviewed online scientific journal. An even more fulsome list will be out in October.
For now, there’s plenty of data to chew on: of the 25 marine areas around the world that were examined, Australian and Japanese waters were the most biodiverse, with nearly 33,000 species in each of these locations. The oceans off China, the Mediterranean Sea and the Gulf of Mexico round out the top five most biodiverse marine regions.
After crustaceans, mollusks (like squid, octopus, clams, snails and slugs) rank second in terms of the number of species found in these regions, with 17 percent. Fish, including sharks, make up 12 percent of species. After that, it’s one-celled micro-organisms at 10 percent; algae and other plant-like organisms at 10 percent; segmented worms at 7 percent; sea anemones, corals and jellyfish, 5 percent; flatworms, 3 percent; starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, 3 percent; sponges, 3 percent; mat or “moss animals,” 2 percent; sea squirts, 1 percent.
The rest are lumped together as “other vertibrates” — including whales, sea lions, seals sea birds, turtles and walruses — at 5 percent, and “other invertibrates” at 2 percent. So some of the best-known of marine creatures make up only a tiny part of the seas’ biodiversity.
The Mediterranean has the most invasive species, creatures that aren’t native, most of which arrived through the Suez Canal from the Red Sea. Most “cosmopolitan” of species — those that appear in more than one marine region — are microscopic plants and animals at the tiny end, and seabirds and marine mammals at the large end of the scale.
One of the most colorfully named animals, the manylight viperfish, is considered the everyman-of-the-deep. It showed up in more than a quarter of the world’s marine waters.
The Census of Marine Life also includes some eye-popping images, some of which are included here. From top to bottom, take a peek at :
— a pelagic amphipod, a crustacean from the Gulf of Mexico;
— an orange sponge brittle star from the Caribbean;
— a ferocious-looking dragonfish (it even has teeth on its tongue, but is only about the size of a banana) from deep waters around Australia;
— zombie worms from Asian waters, so-called because they live in and devour whale bones, and
— a red-lined paper bubble from deep Asian waters.
(photograph by H. Bahena), Felder, D. L. and Camp, D. K. (eds.) 2009. Gulf of Mexico–Origins, Waters, and Biota. Vol. 1. Biodiversity. Texas A&M Press, College Station, Texas (amphipod)
César Herrera (brittle star)
Dr. Julian Finn, Museum Victoria (dragonfish)
Yoshihiro FUJIWARA/JAMSTEC (zombie worms and red-lined paper bubble)