Urticina crassicornis
| Taxonomy |
|---|
| Kingdom: Animalia |
| Phylum: Cnidaria |
| Class: Anthozoa |
| Subclass: Hexacorallia |
| Superorder: Hexactiniida |
| Order: Actiniaria |
| Family: Actiniidae |
| Genus: Urticina |
| Species: crassicornis (O.F. Mueller, 1776) |
Description
Urticina crassicornis is a large and common intertidal and subtidal sea-anemone, biradially symmetrical and ranging from 2 - 12.7 cm tall with a width of 1 - 7.6 cm. This sea anemone has a solid basal plate which is always flat. Its column can be olive green with or without red spots; solid red; cream; or brown, always with small, inconspicuous tubercles but no acontia. Its tubercles are not white and do not usually accumulate bits of sand, gravel and shell. The tentacles, superior of the column and usually 100 in number, are green to opaque cream with red and white striations and are semi-transparent when extended. The tentacles are conical, thick and blunt and arranged in 3 - 5 circular rings around the oral disc. The oral disc has no white striations and is usually the same color as the tentacles.
Geographical Range and Habitat
In the Pacific Ocean, Urticina crassicornis ranges from intertidal and subtidal zones of the Pribilof Islands, Alaska to Monterey, California. In the Atlantic Ocean, it is found in intertidal and subtidal zones ranging from the Arctic Ocean above Newfoundland, Canada to Cape Cod, Massachusetts and also along the coasts of Western Europe. In the state of Washington this sea anemone more commonly frequents the Puget Sound compared to the Pacific Ocean front. It is found in a lower intertidal, upper subtidal zones - 30 m deep, inhabiting well protected and shaded areas. It is a benthic and sessile organism, firmly attached to only hard substrata. This sea anemone is frequently found on docks, wood pilings, and under large rock outcroppings.
Feeding
A non-selective and opportunistic predator, Urticina crassicornis, may feed on crabs, urchins, mussels, gastropods, chitons, barnacles, fish, and sometimes sea stars and stranded jellies. Food is caught within the tentacles which then move it towards the oral disc.
Predators and Protection
In the Pacific, certain species of both Asteroidea (sea stars) and Gastropoda (sea snails and slugs) are predators of this anemone. Demasterias imbricata (asteroidea) and Aeolidia Papillosa (Gastropoda) are two notably frequent predators. Urticina crassicornis senses predation through a simple nerve net spanning along the column and tentacle walls. For protection, U. crassicornis inverts its tentacles to the inside of its body column and projects nematocysts. Minimal locomotion is possible if the organism senses extreme danger.
Reproduction and Life History
Urticina crassicornis produces by both asexual and sexual reproduction. In the Atlantic populations, eggs and sperm are held and fertilized within the body column. The young are brooded between the mesenteries of the body and are emitted as smallish, well developed, young anemones. Spawning occurs in the spring amongst Puget Sound populations, when eggs (yolky, 0.7 mm in diameter) and sperm are released into the sea for fertilization. After fertilization, a solid and ciliated blastula is created due to superficial cleavage. Six days following fertilization, a cone-shaped and benthic, larval planula develops. These planula then settle onto small rocks or the tubes of some annelid worms and rapidly develop into small anemones. 12 days after settlement, 8 tentacles appear. Further growth is slow – two months after settlement, 12 tentacles appear and the anemone is 0.88 mm in diameter; one year after settlement, the anemone has 35 tentacles and is 10 mm in diameter. Growth is proportional to food intake, not age. When starved, this anemone stays living but does not grow. Urticina crassicornis is sexually mature with a diameter of 10 - 15 mm. The lifespan of Urticina crassicornis is 60 - 80 years. They are a solitary species.
References
1. Nybakken, James W. Diversity of the Invertebrates. Dubuque, IA: Times Mirror Higher Education Group, Inc., 1996.
2. Abbot, Donald P., Hadderlie, Eugene C., Morris, Robbert H. Intertidal Invertebrates of California. Stanford, CA: Stanford Univerisity Press, 1980.
3. Kozloff, Eugene N. Marine Inveretebrates of the Pacific Northwest. Seattle, WA: Univeristy of Washington Press, 1996.
4. Cowles, David. Urticina Crassicornis. Walla-Walla, WA: 2005. <http://www.wallawalla.edu/academics/departments/biology/rosario/inverts/Cnidaria/Class-Anthozoa/Subclass_Zoantharia/Order_Actiniaria/Urticina_crassicornis.html>