''Ptilosarcus gurneyi'', the orange sea pen or fleshy sea pen, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

sea pen Sea pens are colonial marine cnidarians belonging to the order Pennatulacea. There are 14 families within the order; 35 extant genera, and it is estimated that of 450 described species, around 200 are valid. Sea pens have a co ...

in the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Pennatulidae Pennatulidae is a family of sea pens, a member of the subclass Octocorallia in the phylum Cnidaria. Genera The World Register of Marine Species The World Register of Marine Species (WoRMS) is a taxonomic database that aims to provide an auth ...

. It is native to the northeastern Pacific Ocean where it lives in deep water anchored by its base in sand or mud. It has received its common name because of its resemblance to a

quill A quill is a writing tool made from a moulted flight feather (preferably a primary wing-feather) of a large bird. Quills were used for writing with ink before the invention of the dip pen, the metal- nibbed pen, the fountain pen, and, eventual ...

in a bottle of ink.

Description

The orange sea pen is a

colonial Colonial or The Colonial may refer to: * Colonial, of, relating to, or characteristic of a colony or colony (biology) Architecture * American colonial architecture * French Colonial * Spanish Colonial architecture Automobiles * Colonial (1920 au ...

cnidaria Cnidaria () is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the latter. Their distinguishing feature is cnidocytes, specialized cells that ...

n, the individual polyps having their own specialised functions. One, the primary polyp, loses its tentacles and forms both the stalk of the colony (known as the rachis), and the bulbous base with which it anchors itself deep into the soft substrate. Other polyps are known as secondary polyps. They include autozooids, which are feeding polyps, being armed with

cnidocyte A cnidocyte (also known as a cnidoblast or nematocyte) is an explosive cell containing one large secretory organelle called a cnidocyst (also known as a cnida () or nematocyst) that can deliver a sting to other organisms. The presence of this c ...

s on the eight branching

tentacle In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work ma ...

s which form the feathery branches of the sea pen. They also contain the gonads. Other secondary polyps are siphonozooids, which can force water into and out of the colony to ventilate it. When the colony is disturbed, it can pump water out and retract into its bulbous base. At this time it emits bioluminescence, perhaps in order to startle a potential

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

. The animal resembles an old-fashioned quill pen. It grows to a height of about and can be white, yellow or orange.

Distribution and habitat

The orange sea pen is found on the western coast of North America, its range extending from Alaska to southern California. It grows on soft sand or mud substrates at depths ranging from .

Biology

The orange sea pen feeds on

plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...

which it catches with the tentacles on its feathery plumes. It orients itself at right angles to the current and can relocate to a new location if it wishes. Breeding takes place when eggs and sperm are produced by the autozooids and expelled through the mouth into the

water column A water column is a conceptual column of water from the surface of a sea, river or lake to the bottom sediment.Munson, B.H., Axler, R., Hagley C., Host G., Merrick G., Richards C. (2004).Glossary. ''Water on the Web''. University of Minnesota-D ...

. The

planula A planula is the free-swimming, flattened, ciliated, bilaterally symmetric larval form of various cnidarian species and also in some species of Ctenophores. Some groups of Nemerteans also produce larvae that are very similar to the planula, which ...

larvae drift as part of the plankton before settling on the seabed and undergoing metamorphosis. The newly formed juveniles are the founding primary polyps of new colonies. Certain starfish

prey Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...

on the orange sea pen. It can distinguish between the threats posed by the specialist predator

leather star The leather star (''Dermasterias imbricata'') is a sea star in the family Asteropseidae found at depths to off the western seaboard of North America. It was first described to science by Adolph Eduard Grube in 1857. Description The leather st ...

(''Dermasterias imbricata''), the generalist predator sunflower seastar (''Pycnopodia helianthoides'') and the

ochre sea star ''Pisaster ochraceus'', generally known as the purple sea star, ochre sea star, or ochre starfish, is a common seastar found among the waters of the Pacific Ocean. Identified as a keystone species, ''P. ochraceus'' is considered an important ind ...

(''Pisaster ochraceus''), which does not feed on sea pens. It reacts by emitting a flash of light and diving into the sand when contact is made by the leather star, sometimes behaves similarly when approached by the sunflower seastar and does not react defensively when touched by the ochre sea star.

References

External links

* {{Taxonbar, from=Q3948945 Pennatulidae Cnidarians of the Pacific Ocean Animals described in 1860 Taxa named by John Edward Gray