Brown hydra (Hydra oligactis)
Facts
| Kingdom | Animalia |
|---|---|
| Phylum | Cnidaria |
| Class | Hydrozoa |
| Order | Capitata |
| Family | Hydridae |
| Genus | Hydra (1) |
| Size |
Length of tentacles: up to 25 cm (2) Body length: 20-30 mm (2) |
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Status
Common and widespread in Britain (2).
Description
Range
The brown hydra is a widespread species, found throughout the northern hemisphere and parts of Australia (3).
Habitat
This hydra is found in freshwater ponds, brooks, rivers, and streams as well as at the edges of lakes, and typically attaches to aquatic plants, stones, twigs and debris (3).
Biology
The brown hydra, although largely a sessile species is capable of moving by gliding along on the 'basal disc', the part of the body that attaches to the substrate. They may also move by bending the body around, attaching to the substrate with the tentacles, and then 'somersaulting' or 'looping' forwards (3). This species is carnivorous; it feeds on small aquatic invertebrates that are paralysed by the stinging cells when the prey comes into contact with the tentacles. The prey item is then brought to the mouth by the tentacles and taken into the body of the hydra (3).
Reproduction in hydras typically takes place asexually by a process known as 'budding', in which a bud-like growth on the body of the 'parent' hydra eventually grows into a new individual that becomes separated from the parent. When conditions are harsh, or there is a shortage of food, hydras can reproduce sexually; a single individual may produce both male and female sex cells, which are released into the water where fertilisation occurs. The egg develops into a larva, which is covered in tiny hair-like structures known as cilia. The larva may either settle immediately and develop into a hydra, or become surrounded in a tough outer layer that allows it to survive harsh conditions (4).
Threats
This species is not threatened.
Conservation
The brown hydra is not listed under any conservation legislation.
Further Information
For more on this species see the Animal Diversity Web brown hydra fact sheet:
http://animaldiversity.ummz.umich.edu/accounts/hydra/h._oligactis.html
Authentication
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Asexually: of asexual reproduction: reproduction that does not involve the formation of sex cells ('gametes'). In many species, asexual reproduction can occur by fission (or in plants 'vegetative reproduction'); part of the organism breaks away and develops into a separate individual. Some animals, including vertebrates can develop from unfertilised eggs, this process, known as parthenogenesis gives rise to offspring that are genetically identical to the parent.
Larva: stage in an animal's lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
References
- National Biodiversity Network Species Dictionary (Jan 2003):
http://www.nhm.ac.uk/nbn - Olsen, L., Sunesen, J., & Pedersen, B. V. (1999) Small freshwater creatures. Oxford University Press, Oxford.
- Animal Diversity Web: Brown Hydra (March 2003):
http://animaldiversity.ummz.umich.edu/accounts/hydra/h._oligactis.html - Nichols, D., Cooke, J. & Whiteley, D. (1971) The Oxford Book of Invertebrates. Oxford University Press, Oxford.
