Overview

Comprehensive Description

Biology/Natural History: The entire central part (rachis) is said to be one large polyp. Smaller, inconspicuous polyps open into it and pump water in an out as needed for expansion or contraction. Produces a strong greenish luminescence when disturbed. Preyed upon by several nudibranchs, including Hermissenda crassicornis, Armina californica, and Tritonia festiva, and of the seastars Dermasterias imbricata, Pycnopodia helianthoides, Mediaster aequalis, and Crossaster papposus. The sea pens may rapidly burrow into the sediment when contacted by a predator. Although they do not appear to burrow when exposed only to seawater which contained a predatory seastar, they were more likely to burrow after contacting a predatory seastar if they had already been exposed to its smell. This species responds to different predators differently.

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© Rosario Beach Marine Laboratory

Source: Invertebrates of the Salish Sea

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A sea pen with a fleshy lower part of stalk (lower left in the picture above), which is buried in the sediment. Upper part of central stalk (rachis) has a hard central support. Branches are thick and fleshy with small polyps along the edges. Usually yellow or orange, often large (up to 1/2 meter). Has great powers to expand or contract.
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Source: Invertebrates of the Salish Sea

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Distribution

British Columbia to Central California.

Biogeographic Regions: pacific ocean (Native )

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Source: Animal Diversity Web

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Geographical Range: Gulf of Alaska to southern California

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Source: Invertebrates of the Salish Sea

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Physical Description

Morphology

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.

Other Physical Features: ectothermic ; radial symmetry

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Look Alikes

How to Distinguish from Similar Species: There are no similar species near Rosario.
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Source: Invertebrates of the Salish Sea

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Ecology

Habitat

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.

Aquatic Biomes: benthic ; coastal

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shelf
  • UNESCO-IOC Register of Marine Organisms
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Source: World Register of Marine Species

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Depth range based on 120 specimens in 1 taxon.
Water temperature and chemistry ranges based on 8 samples.

Environmental ranges
  Depth range (m): 0 - 512.46
  Temperature range (°C): 4.612 - 28.315
  Nitrate (umol/L): 0.487 - 16.592
  Salinity (PPS): 31.893 - 34.080
  Oxygen (ml/l): 4.518 - 6.561
  Phosphate (umol/l): 0.043 - 1.601
  Silicate (umol/l): 1.449 - 32.136

Graphical representation

Depth range (m): 0 - 512.46

Temperature range (°C): 4.612 - 28.315

Nitrate (umol/L): 0.487 - 16.592

Salinity (PPS): 31.893 - 34.080

Oxygen (ml/l): 4.518 - 6.561

Phosphate (umol/l): 0.043 - 1.601

Silicate (umol/l): 1.449 - 32.136
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

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Depth Range: Shallow subtidal to 70 m

Habitat: Sand and mud bottoms

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Source: Invertebrates of the Salish Sea

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Trophic Strategy

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.

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Life History and Behavior

Reproduction

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

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Ptilosarcus gurneyi

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 2
Species With Barcodes: 1
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Source: Barcode of Life Data Systems (BOLD)

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Conservation

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.

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