Hydrozoa
Hydrozoa
Hydrozoa (pronounced: hy-dro-zo-a) is a taxonomic class of individually very small, predatory animals, some solitary and some colonial, most living in salt water. The colonies of the colonial species can be large, and in some cases the specialized individual animals cannot survive outside the colony.
Etymology
The term Hydrozoa comes from the Greek words 'hydro' meaning water and 'zoa' meaning animals.
Classification
Hydrozoa is a class within the phylum Cnidaria, which also includes the classes Scyphozoa (jellyfish), Anthozoa (corals and sea anemones), and Cubozoa (box jellies).
Characteristics
Hydrozoans are related to jellyfish and corals and have similar basic anatomy. They are, however, distinguished from their relatives by the fact that they have both a polyp stage and a medusa stage in their life cycle.
Life Cycle
The life cycle of hydrozoans includes both asexual and sexual reproduction. The asexual phase is the polyp phase, which is attached to the substrate. The sexual phase is the medusa phase, which is free-floating.
Habitat
Most hydrozoans are marine and are found in every ocean, from the water surface to the deep sea. Some species, however, are freshwater and are found in river and lake environments.
Related Terms
- Cnidaria: The phylum that includes the class Hydrozoa.
- Polyp: The asexual stage in the life cycle of a hydrozoan.
- Medusa: The sexual stage in the life cycle of a hydrozoan.
- Colony (biology): A group of individuals that live together and are connected, such as in some species of hydrozoans.
External links
- Medical encyclopedia article on Hydrozoa
- Wikipedia's article - Hydrozoa
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