Sea creature throws evolutionary view on digestive anatomy off balance

Scientists have long believed that comb jellies, otherwise known as ctenophores, ingest food and excrete waste through the same body opening. Through DNA analyses, they also know that these transparent marine creatures evolved earlier than jellyfish, sea anemones, and other animals that lack an anus, and much earlier than creatures with through-guts. However, they were stunned by a new discovery that comb jellies excrete waste through openings not their mouths.

This discovery somehow throws off balance the concept of ladder evolution in digestive anatomy, in which animals evolved from having one hole to having two.

"Looks like I've been wrong for 30 years," said marine biologist George Matsumoto to Science Magazine. "If people don't see this video, they won't believe it."

Matsumoto works at Monterey Bay Aquarium Research Institute in Moss Landing, California, and he was referring to the video presented by University of Miami's William Browne during the Ctenopolooza meeting in St. Augustine, Florida on March 15.

According the report by Science Mag, the evolutionary biologist showed a video of two species of comb jellies that he keeps in captivity, and he fed these trasluscent animals with genetically engineered zebrafish and crustaceans. These prey glow red with flouresent protein; thus, the scientist was able to observe as the food traveled through his subjects' bodies. This was captured using a sophisticated video setup, and what he discovered is that food particles that were not digested were excreted through pores in the comb jellies' rear and not through their mouths.

"This is a sphincterlike hole," he explained during the presentation, showing muscles that surround each ring.

There are theories regarding this new discovery, one of which is that, independent of other animals, comb jellies evolved these pores over millions of years on their own. Another one that Browne is looking into is, this may have evolved in an ancient ancestor but was lost in other animals that maintain one hole. If comb jellies do not activate the same genes for developing pores that other animals use in growing anuses, then this will indicate that the evolution of this body part is not a singular event.