Ptilosarcus gurneyi

Geographic Range

British Columbia to Central California.


Ptilosarcus gurneyi are found anchored in soft or sandy substrates. They live in a range from below the low-tide line to water more than 30 meters (100 ft) deep.

Physical Description

Sea pens grow to be about 46 cm high and 102 mm wide. They consist of 20 pairs of flat, wide side branches with rows of polyps along both edges.


Sea pens reproduce by spawning. Typical egg size is 500-600 micrometers. The peak breeding season occurs from March until April. Fertilized ova develop into planula, which are non-feeding and free-swimming and usually settle quickly. Once settled, the planula larva metamorphose into a polyp, and their base becomes a stem. The secondary polyps grow laterally from this structure. The juveniles grow rapidly; they can survive unfed for weeks.

  • Parental Investment
  • no parental involvement


Sea pens are colonial. Although considered sessile, they can move up to 40 cm by slow creeping on their vertical axes while still attached to their substrates. One behavioral characteristic found in all sea pens is that they have the ability to bury themselves. If disturbed, they contract and withdraw into the muddy bottom by releasing large amounts of water from their canal system.

Food Habits

Ptilosarcus gurneyi is a planktonic feeder. The autozooid branch of the polyp filters minute organisms into the main axis of the sea pen. These organisms are digested by fluid secreted from special filaments. The particles are phagocytized and passed to mesogloeal cells, in which the digestion process is completed.

Conservation Status

Sea pens have inhabited the earth's surface for hundreds of millions of years. Currently, their numbers are not declining or threatened. Because sea pens are vulnerable to dredges used for oyster harvesting, the only threat to their survival arises from humans. Sea pens are found throughout the world, from tropical to Anarctic waters.

  • IUCN Red List [Link]
    Not Evaluated

Other Comments

The orange sea pen is luminescent. It has no light-producing organs, but its color comes from mucous formed in response to touch. Luminosity is inhibited by exposure to direct light. Sea pens also live symbiotically with Pseudoporcellanella (a crab).


Jenny Lambert (author), University of Michigan-Ann Arbor.


Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map


Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.


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

native range

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

radial symmetry

a form of body symmetry in which the parts of an animal are arranged concentrically around a central oral/aboral axis and more than one imaginary plane through this axis results in halves that are mirror-images of each other. Examples are cnidarians (Phylum Cnidaria, jellyfish, anemones, and corals).


George, John David and Jennifer. 1979. Marine Life. John Wiley and Sons, New York. Grzimek. 1972.

Lower Animals. Animal Life Encyclopedia, 1:251.

Hamau, Hans W. 1974. In the Coral Reefs. Doubleday, New York 87-88pp.

Kayemash. 1975. How Invertebrates Live. Phaidon Press, New York 128-130pp.

Meinkoth, Norman August. 1981. The Audubon Society Field Guide to North AmericanSeashore Creatures. Chanticleer Press, New York 370-371pp.

Strathmann, Megumi F. Reproduction and Development of Marine Invertebrates of the Northern Pacific Coast. University of Washington Press, Seattle 87-91pp.

Villee, Claude Alvin. 1978. General Zoology. Saunders College, New York 576pp.