Are Sponges the World's Most Successful Animals?

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Today at Discovery News you can read about the world's earliest evidence for animal life. These oldest known animal fossils likely belonged to sponges, a group of animals that are still very much with us today.

Are sponges then the world's most successful animals?

(Sponge biodiversity and morphotypes at the lip of our wall site in 60

feet of water. Included are the yellow tube sponge (Aplysina fistularis), the purple vase sponge (Niphates digitalis), the red encrusting sponge (Spiratrella coccinea), and the gray rope sponge (Callyspongia sp.). Images Courtesy of the Twilight Zone Expedition Team 2007, NOAA-OE)

Consider that sponges:

  • are now at the very bottom of the evolutionary tree for animals
  • have lived through at least five major extinction events in Earth's history
  • survived the "Snowball Earth" event 635 million years ago that left much of the globe covered in ice
  • are still going strong today, with some 10,000 or so known species still in existence
  • are worldwide in their distribution, with habitats ranging from the tropics to the polar regions and almost everything in between

Sponges were around at least:

75 million years before land plants

250 million years before insects and seeds

About 300 million years before amphibians

350 million years before reptiles

450 million years before mammals

500 million years before birds

520 million years before flowers

649+ million years before the first anatomically modern humans

These dates are all approximates, but you get the picture. Sponges have been around for a very long time.

Sponges have medicinal properties due to the presence of microbial chemicals that may control viruses, bacteria, tumors and fungi. They even look rather nice, and some species are helpful to humans when dried and put to use in the kitchen and bathtub.

What's not to like?

Nevertheless, Adam Maloof, a Princeton University geosciences professor who led the sponge fossil study, isn't ready just yet to put sponges at the top of the animal list.

"It is amazing to think of sponges as having been on Earth for 650 million years, but I don't think that makes sponges the most successful animal," Maloof told Discovery News.

"To me," he added, "the word 'success' also relates to diversity and abundance."

Which animals could be contenders then?

Insects are often said to be the most diverse and important animals. Up to 99% of the world's animal species are invertebrates. Among insects, beetles are the most diverse group. Plankton, depending on the type and how you define them, are at the top, or close to it, for abundance. In the short term, we humans certainly wield a lot of power, but in the long term, we're still a blip on the timeline of evolution.

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