New phylum found residing on lobsters.
On the mouths of Norwegian lobsters lives a tiny invertebrate that fits into none of the animal kingdom's 35 or so broad taxonomic groups called phyla, claim Peter Funch and Reinhardt Mbjerg Kristensen of the University of Copenhagen. They have named the creature Symbion pandora and have assigned it to an entirely new phylum, which they call Cycliophora.
Their discovery of "what appears to be a new phylum of metazoans has to be the zoological highlight of the decade," asserts Simon Conway Morris of the University of Cambridge in England in a commentary accompanying the report in the Dec. 14 Nature.
"I think that there will be a lot of response, both positive and negative" to the report, acknowledges Funch. Scientists often argue over phylum designations.
For example, Funch and Kristensen state that the new creature most nearly resembles the phyla Ectoprocta and Entoprocta. Yet scientists fail to agree that Ectoprocta and Entoprocta are closely related, Morris notes.
Tom Fenchel of the Marine Biological Laboratory in Elsinore, Denmark, first observed the creature in the 1960s. Three decades later, using a state-of-the-art electron microscope that can peer deep into cell parts, Funch and Kristensen described the creature's unique body structure and behavior. They find that it reproduces both sexually and asexually and performs some odd stunts in the process. It also has several types of larvae, only some of which feed.
While attached to a lobster, a feeding-stage S. pandora uses tiny hairs, called cilia, around its mouth to capture food intended for the lobster. Periodically, its entire feeding apparatus, including the stomach, deteriorates. But S. pandora remains stuck to the lobster and grows new feeding structures.
After several cycles, so-called pandora larvae develop inside the feeding-stage animal. Before they emerge, each pandora produces a feeding-stage larva inside itself. When a pandora larva emerges, it settles on the lobster and soon dies. Its feeding-stage larva remains attached to the lobster.
Before the lobster molts, something-perhaps the hormones that tell it to molt-triggers S. pandora to produce either a female or a dwarf male, which has only a nervous system, reproductive organs, and cilia for swimming. Then sexual reproduction begins.
The dwarf male seeks out an S. pandora that is carrying a female and fertilizes her eggs-exactly when remains unclear, Funch says. The fertilized female quickly dies. Yet another type of larva, a chordoid, emerges from the eggs, swims to another lobster, and dies, leaving a few bud cells that develop into a feeding-stage larva.
When their lobster hosts finally molt, all the S. pandora disperse and find a new lobster or return to their original one after it finishes molting.
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|Title Annotation:||Danish researchers discovered a new phylum of metazoans called Symbion pandora on the lips of Norwegian lobsters|
|Article Type:||Brief Article|
|Date:||Dec 16, 1995|
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