Etymology: From the Greek Cyclos for round, and Phoros to bear. This relates to the circle of feeding cilia around the mouth.
Characteristics of Cycliophora:
- Bilaterally symetrical.
- Body has more than two cell layers and includes tissues and organs.
- Has a body cavity, and a U-shaped through gut.
- Body has a distinct head and trunk.
- Reproduction is both sexual and asexual.
- Has a well developed nervous system with a brain and nerve ganglia.
- Has several distinct larval stages.
- Lives attached to the hairs on the lips of Lobsters.
- One species only is currently known.
The discovery of an animal that was – not only a new species – but of a whole new phylum of organisms, in 1994 by Reinhardt Kristensen and Peter Funch was perhaps the most exciting happening in the biological world in the last decade of the 20th century.
The single known species of Cycliophora, Symbion pandora lives on the bristles surrounding the mouth of the Norway lobster Nephrops norvegicus. This is a relatively common species of crustacean which can be caught in the Kattegat Straits, a busy shipping lane between Sweden and Denmark – as well as around the Faroes.
Symbion pandora has a very complex life cycle, with a number of well-defined sessile and free swimming stages with different morphologies.
None of the free-swimming stages feed and all are short-lived. The largest stage is the sessile feeding stage. The adult feeding stage Symbion pandora is typically 350 μm long and lives attached by an adhesive disc to the lips of the lobster. It filter feeds using a mouth surrounded by a ring of cilia.
Symbion pandora has a complicated sex life that is related to the moult cycle of the lobster. Sexual reproduction is initiated when the lobster is near the end of its moult cycle. This is when sexually mature feeding stages are found attached to the lobster’s lips. Asexual reproduction occurs during the rest of the lobster’s moult cycle.
The reproductive cycle of Symbion pandora also involves asexual budding, dwarf males that settle on and attach to the adult females, other females which degenerate into larvae after settling, and a free swimming larvae which contains a new feeding stage.
Class Eucycliophora Funch et Kristensen, 1995
Order Symbiida Funch et Kristensen, 1995
Family Symbiidae Funch et Kristensen, 1995
Genus Symbium Funch et Kristensen, 1995
Species Symbion pandora Funch et Kristensen, 1995
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