Stauromedusae
Encyclopedia
Stauromedusae are the stalked jellyfishes, of the class
Staurozoa within the phylum Cnidaria
. They are unique in that they do not have an alternation of polyp and medusa life cycle phases, but are interpreted as an attached medusa
stage, with a life style more resembling that of polypoid forms. They have a generally trumpet-shaped body, positioned upside-down in comparison with other jellyfish, with the tentacles projecting upwards, and the stalk located in the centre of the umbrella.
Members of this class are commonly found in relatively cold waters, close to the shoreline.
Sexually mature stauromedusae free-spawn eggs or sperm, which fertilize in the sea and form a creeping, unciliated planula
larva. The larvae crawl across the sea floor and find a suitable place, attaching themselves typically to rock or algae, where they eventually develop into a new, attached stauromedusa. Unlike most scyphozoan jellyfish
that practice strobilation
, or the process of dividing themselves into body segments, which become new individuals, nearly all stauromedusae develop directly into the adult form.
Although conventionally considered to be an order in the class Scyphozoa
, recent genetic studies suggest that Stauromedusae should be elevated to a taxon
equivalent of Scyphozoa and Cubozoa, and should therefore be known as the class Staurozoa.
Class (biology)
In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...
Staurozoa within the phylum Cnidaria
Cnidaria
Cnidaria is a phylum containing over 9,000 species of animals found exclusively in aquatic and mostly marine environments. Their distinguishing feature is cnidocytes, specialized cells that they use mainly for capturing prey. Their bodies consist of mesoglea, a non-living jelly-like substance,...
. They are unique in that they do not have an alternation of polyp and medusa life cycle phases, but are interpreted as an attached medusa
Medusa (biology)
In biology, a medusa is a form of cnidarian in which the body is shaped like an umbrella, in contrast with polyps. Medusae vary from bell-shaped to the shape of a thin disk, scarcely convex above and only slightly concave below...
stage, with a life style more resembling that of polypoid forms. They have a generally trumpet-shaped body, positioned upside-down in comparison with other jellyfish, with the tentacles projecting upwards, and the stalk located in the centre of the umbrella.
Members of this class are commonly found in relatively cold waters, close to the shoreline.
Sexually mature stauromedusae free-spawn eggs or sperm, which fertilize in the sea and form a creeping, unciliated planula
Planula
A planula is the free-swimming, flattened, ciliated, bilaterally symmetric larval form of various cnidarian species. The planula forms from the fertilized egg of a medusa, as the case in scyphozoans and some hydrozoans, or from a polyp, as in the case of anthozoans...
larva. The larvae crawl across the sea floor and find a suitable place, attaching themselves typically to rock or algae, where they eventually develop into a new, attached stauromedusa. Unlike most scyphozoan jellyfish
Jellyfish
Jellyfish are free-swimming members of the phylum Cnidaria. Medusa is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria...
that practice strobilation
Strobilation
Strobilation or transverse fission is a form of asexual reproduction consisting of the spontaneous transverse segmentation of the body. It is observed in certain cnidarians and helminths...
, or the process of dividing themselves into body segments, which become new individuals, nearly all stauromedusae develop directly into the adult form.
Although conventionally considered to be an order in the class Scyphozoa
Scyphozoa
Scyphozoa is a class within the phylum Cnidaria, sometimes referred to as the "true jellyfish".The class name Scyphozoa comes from the Greek word skyphos , denoting a kind of drinking cup and alluding to the cup shape of the organism....
, recent genetic studies suggest that Stauromedusae should be elevated to a taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
equivalent of Scyphozoa and Cubozoa, and should therefore be known as the class Staurozoa.