Cyanea capillata Linnaeus, 1758, North Sea.
OTHER COMMON NAMES None known.
Medusae are reported to grow to 80 in (2 m) in diameter but are usually less than an eighth that size. The edge of the swimming bell is divided into eight lobes, giving it the appearance of a flower viewed from above. As many as 150 long tentacles are present in groups beneath each of the eight lobes. The oral arms form a diaphanous mass beneath the bell that is a little longer than it is wide. The bell often is brownish orange, and the oral arms are maroon, but color varies from pale yellow to dark red.
Medusae are present during summertime in boreal latitudes, but in wintertime they occur in temperate zones. Reported from Arctic, northern European, North American Atlantic and Pacific, southern Australian, and Antarctic waters.
The medusae prefer cool temperatures below 70°F (20°C). They often are found in surface waters of estuaries or coastal bays.
The swimming bell of the medusa orients upward toward the water surface. The swimming beat is slow, just maintaining the position of the medusa in the water column. The tentacles may spread out several meters around the bell. They do not form aggregations.
The diet includes planktonic crustaceans, such as copepods and cladocerans, and fish eggs and larvae. It also contains large proportions of pelagic tunicates (larvaceans = appendicularians), ctenophores (comb jellies), hydromedusae, and scyphomedusae. The long tentacles snare such relatively large prey and bring them to the oral arms, where they are enveloped and digested. Predation effects have been studied in Australia, Norway, and Alaska, where populations of medusae remove only a small percentage of the zooplankton daily.
The life cycle is typical of semaeostome scyphomedusae. Sperm are shed into the water and fertilize eggs in the female. Larvae are brooded along the edges of the oral arms. Sexual reproduction takes place near the end of the life of the medusa, in early spring in warm climates and during the summer at high latitudes. Larvae attach to the undersides of hard surfaces and form polyps, which asexually produce medusae and other polyps.
CONSERVATION STATUS Not listed by the IUCN.
SIGNIFICANCE TO HUMANS
Medusae have a painful sting that annoys swimmers and fishermen retrieving fishing nets. ♦
Was this article helpful?
This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.