Haliclystus auricula

Geographic Range

Haliclystus auricula is most prevalent in the waters of the northern Pacific. They usually attach themselves to seaweed of various species, and large colonies can be found on eelgrass beds in Puget Sound and northern California. These organisms are usually found in cold seas.

(Nichols, 1979 ; Ricketts,et al 1997)


Haliclystus auricula thrives in the cool, coastal waters of the north Pacific. They attach themselves to various types of vegetation such as: Zostera sea grass, fucoid seaweeds, and eelgrass beds.

(Nichols, 1979 ; Ricketts, et al 1997)

Physical Description

Haliclystus auricula is a Cnidarian that is considered as a "pseudopolyp." It has no free-living medusa stage in its life cycle, thus making it sessile. This stauromedusan jellyfish has an adhesive disk, which is used to attach itself to seaweed. The disk itself is on the opposite side from its mouth so feeding is still convenient. Haliclystus auricula is only a few centimeters in height, and has a square shape to it. There are also 8 lobes which are attached to this square and are equipped with little tentacles. These tentacles have white marginal anchors between them. The body of this organism is split by 4 gastric ridges in the coelenteron and also has 4 ectodermal pits that are indented near the mouth. Many jellyfish are characteristic of a body that is split into 4 parts and Haliclystus auricula follows such a trend. It also follows the trend that Cnidarians are diploblastic and have tissue level organization. Another aspect of this species is that it has a more complex nervous system than other Scyphozoans. Instead of a basic nerve net, Haliclystus has an exumbrellar nerve plexus. Finally, the overall appearance of Haliclystus auricula is a little pale green or pinkish creature with tentacles.

(Nichols, 1979 ; Russel-Hunter, 1979 ; Bayer and Owre, 1968)


Haliclystus auricula is unusual in that it is a Schyphozoan, but it lives in the polyp stage. This impacts the reproductive cycle of this species. First of all, reproduction is sexual in Haliclystus auricula, but it takes place in the polyp phase. The females release eggs and the males release sperm into the water. When these come together and the egg is fertilized; a planula forms. This planula stage is common with the Cnidarian reproductive cycle, but something interesting happens with these little planula. They are often found in large groups so they can feed on animals. Each planula is too small to kill an organism by itself, but together they can feed on rotifers, nematodes, and copepods. The planula can crawl around for a few days using their cilia, but then they change to the adult "polyp". This stage means that the polyp is equipped with gonads and is mature. Finally, these polyp forms release egg or sperm and the cycle begins again.

(Nichols, 1979 ; Russell-Hunter, 1979)

  • Parental Investment
  • no parental involvement


Behaviorally, this species is fairly simple. It has almost lost the ability to move, thus becoming primarily sessile. It spends most of its life attached by pedal secretion to seaweed such as: Zostera, fucoid seaweed, or eelgrass. It is believed that Haliclystus auricula can move by using its mouth covered with tentacles and contracting its adhesive disk. This is only over smooth surfaces and has not really been seen. Another idea of how it may move is by using the marginal anchors within the tentacles as looping mechanisms. The main purpose of the marginal anchors is to produce a sticky mucous that attaches it to the plants. However, Halicystus auricula is not a very mobile organism.

(Nichols, 1979 ; Russell-Hunter, 1979 ; Ricketts, et al 1997 ; Bayer and Owre, 1968)

Food Habits

Haliclystus auricula is a species that spends most of its life attached to seaweed and eelgrass. They use the tentacles around their mouths to capture small prey. Stauromedusans, like Haliclystus auricula, often feed on small bivalves, snails, brittle stars, and crustaceans. Once these organisms have been consumed, the shells are expelled from the mouth. They cannot eat anything very large, because they are only a few centimeters in size. However, when they consume something they undergo both intracellular and extracellular digestion. Haliclystus has filaments inside the gastrovascular cavity so that the enzymes have more surface area on which they can react.

(Ricketts, et al 1997 ; Grzimek, 1972)

Economic Importance for Humans: Positive

Haliclystus auricula does not have a positive impact when it comes to economic importance to humans, because it is not used in human consumption or decoration.

Economic Importance for Humans: Negative

Haliclystus auricula does not negatively affect humans, because they do not consume any organisms that are economically important to humans.

Conservation Status

Other Comments

Haliclystus auricula has an amazing ability to absorb the pigment cells of the plant to which it is attached. Slowly, the color of the plant or algae travels through the basal disc, and is absorbed by Haliclystus auricula. This can help with camouflage and avoiding predation.

(Grzimek, 1972)


Sunil Naik (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.


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


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).


Bayer, F., H. Owre. 1968. The Free-Living Lower Invertebrates. New York: The Macmillan Company.

Grzimek, B. 1972. Grzimek's Animal Life Encyclopedia Volume 1 Lower Animals. New York: Van Nostrand Reinhold Company.

Nichols, .. 1979. The Oxford Book of Invertebrates. Oxford: Oxford University Press.

Ricketts, .., .. Calvin, .. Hedgpeth. 1997. Between Pacific Tides 5th Edition. Stanford,California: Stanford University Press.

Russell-Hunter, .. 1979. A Life of Invertebrates. New York: Macmillan Publishing Co., Inc..