Symbion pandora

Geographic Range

Symbion pandora can be found on the lips of Norwegian lobsters, Nephrops norvegicus. They are found at depths of 20-40 meters (66-131 feet) from coastal Norway south to the coastline of the Mediterranean region. (Burton and Burton, 1989; Morris, 14 December 1995)


Symbion pandora can be found on the mouth bristles of the Norwegian lobster. It attaches to the lobster with an adhesive disk located on its posterior end. Symbion pandora shares a symbiotic relationship with its host. It recieves easy access to food with out harming or helping the Norwegian lobster. This is called commensalism. (Morris, 14 December 1995)

Physical Description

Symbion pandora has a bilateral, sack-like body with no coelom. There are three basic life stages:

Asexual Feeding Stage- At this stage S. pandora is neither male nor female. It has a length of 347 um and a width of 113 um. On the posterior end of the sack-like body is a stalk with an adhesive disk, which attaches itself to the host. On the anterior end is a ciliated funnel (mouth) and an anus.

Male- S. pandora has a length of 84 um and a width of 42 um during this stage. It has no mouth or anus, which signifies the absence of a digestive system. It also has two reproductive organs.

Female- S. pandora is the same size as the male in this stage. It does, however, have a digestive system which collapses and reconstitutes itself as larva. (Funch and Kristensen, 14 December 1995)

  • Sexual Dimorphism
  • sexes alike


Symbion pandora reproduces both sexually and asexually. It reproduces asexually by young budding off from the asexual feeding stage. The sexual cycle begins only during the molting season of the Norwegian lobster, its host. The male attaches itself to a feeding stage that contains a developing female and impregnates her. She escapes from the feeding stage and attaches herself to the host. The larva develops within the female S. pandora She then dies and the larva escapes. (Funch and Kristensen, 14 December 1995)


Symbion pandora is a solitary species. Interaction seems to be limited to mating and feeding. Symbion pandora is sessile most of its life. There are, however, three brief periods of free swimming which occur between feeding stages. (Funch and Kristensen, 14 December 1995)

Food Habits

Symbion pandora attaches itself on the lips of Norwegian lobsters, where it then sweeps food particles into its ciliated, disk-shaped mouth. The digestive system is closely intertwined with the reproductive cycle. A unique feature of the digestive system of S. pandora is that it collapses and becomes larva. (Olsen, 18 December 1995)

Ecosystem Roles

This species is parasitic on Norweigan lobsters.

Species Used as Host

Economic Importance for Humans: Positive

Unknown at this time

Economic Importance for Humans: Negative

Unknown at this time

Conservation Status

Symbion pandora is not on vulnerable, threatened, or endangered status. In fact, large populations can be found on a single lobster. (Funch and Kristensen, 14 December 1995)

Other Comments

Symbion pandora was an important discovery for scientists in 1995. While it is not considered unusual to discover a new species, it is unusual to find a new phylum. Cycliophora, its designated phylum, was created because the digestive system and reproductive cycle are unique to the animal kingdom. There are still many unknowns concerning S. pandora. Most information on its life cycle and sexual habits are hypothetical. (Funch and Kristensen, 14 December 1995; Walker, 1995)


Crystal Parsons (author), Fresno City College, Carl Johansson (editor), Fresno City College.


Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map


reproduction that is not sexual; that is, reproduction that does not include recombining the genotypes of two parents

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


the nearshore aquatic habitats near a coast, or shoreline.


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature


union of egg and spermatozoan


a method of feeding where small food particles are filtered from the surrounding water by various mechanisms. Used mainly by aquatic invertebrates, especially plankton, but also by baleen whales.


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.


an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.


remains in the same area


non-motile; permanently attached at the base.

Attached to substratum and moving little or not at all. Synapomorphy of the Anthozoa


reproduction that includes combining the genetic contribution of two individuals, a male and a female


lives alone


Burton, M., R. Burton. 1989. Lobster. Pp. 1463 in Marshall Cavendish International Wildlife Encyclopedia. Long Island, NY: Marshall Cavendish Corporation.

Funch, P., R. Kristensen. 14 December 1995. Cycliophora is a New Phylum with Affinites to Entoprocta and Ectoprocta. Nature, 378: 711-714.

Morris, S. 14 December 1995. A New Phylum From Lobster's lips. Nature, 378: 661.

Olsen, J. 18 December 1995. Microscopic Creature Ranks as Real Misfit. Detroit News.

Walker, D. 1995. "A Lobster's Microscopic Friend, Symbion pandora - a new life form and a new phylum" (On-line). Accessed 01/10/04 at