Animal families with most diversity also have largest range of body sizes

March 18th, 2009 - 3:19 pm ICT by ANI  

Washington, March 18 (ANI): A new research has found that families of animals grouped together by a similar body plan, with the greatest diversity of species, were also those with the largest range of body sizes.

The research was carried out by the National Evolutionary Synthesis Center (NESCent) researchers in the US, as part of an analysis of body sizes across all orders of animal life.

Researchers Craig McClain and Alison Boyer created a giant database on body sizes across all orders of animal life and found that phyla - families of animals grouped together by a similar body plan - with the greatest diversity of species were also those with the largest range of body sizes.

The sponges, Poriferans, were found to have some of the greatest diversity of both body size and species, ranging from microscopic to the size of an automobile.

Molluscs (snails, squid, clams, chitons), and Arthropods (crabs, insects, lobsters, copepods) also showed great diversity.

So did our family, the Chordates, which ranges from a half-inch fish in the swamps of Borneo to the truly leviathan 100-ton Blue Whale, with all the fishes, birds and mammals in between.

On the one hand, it may seem obvious that diversity in size and diversity in species go together, acknowledged marine biologist McClain, assistant director of science at NESCent.

But, it also says something a little more subtle about how new species arise and adapt to all the available niches in the environment. This really comes down to understanding the diversity of life on Earth, he added.

There are apparently physical limits to the range of sizes that can work for some body plans.

In worms, for example, it is impossible to slither along if the girth and weight become too large. (The largest worm, Riftia pachyptila, from deep-sea vents, doesnt move.)

Within the range of sizes that works for a given body plan, evolution creates new species and new sizes, McClain said.

The finding also points to areas where more species might be waiting to be discovered.

For example, the little-studied priapulid worms have only 16 species on the books, but with a very large range in size.

McClains guess is that there may be more undiscovered species within that range of sizes.

There are groups that definitely dont have a lot of people studying them, he said. Knowing something about a body plans size constraints also might allow for a ballpark estimate of its number of species, he added. (ANI)

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