Hydras have well developed powers of regeneration and grafting. Very little is known about the length of life under normal conditions. In the lab, hydras have been known to live for three to twelve months or more. Males outnumer females, an unusual situtation in most fresh water invertebrates.
Hydra oligactis is a hatchery nuisance because it may kill fish fry.
Hydra oligactis, as in all Cnidaria, are strictly carnivorous and eat many different kinds of small metazoans, including annelids, copepods, cladocerans, and insects. Hydra capture their food by paralyzing and killing the food organism by means of nematocysts, which are discharged into the prey. The prey is brought to the mouth (proctostome) by the tentacles, a response that is induced glutathione. This is considered the key mechanism in digestion. The organism is then taken in through the mouth, which is star-shaped or circular. Hydras have been known to feed on the organic material of the substrate when the food supply is insufficient. This behavior, however, is not considered normal. Digestion is both extra and intracellular.
The brown hydra is commonly found in the Northern Hemisphere and parts of Australia.
Biogeographic Regions: nearctic (Native ); australian (Native )
Hydras are are well known as the faunas of ponds, spring brooks, unpolluted streams, rivers, and the littoral zone of lakes.
Aquatic Biomes: lakes and ponds; rivers and streams
Other Physical Features: ectothermic ; radial symmetry
The common asexual method of reproduction by hydras is budding. Buds originate at the junction of the stalk and gastric regions. The bud begins as a hemispherical outpouching that eventually elongates, becomes cylindrical, and develops tentacles. The bud then pinches off and a new individual becomes independent. Buds are produced every two to three days under favorable conditions. Following unfavorable conditions, such as injuries or periods of scarce resources, hydras occasionally reproduce through transverse and longitudinal fission.
Parental Investment: no parental involvement
Hydra oligactis, also known as the brown hydra, is a species of hydra found widely dispersed in the northern temperate zone. It is a common organism found in still waters from early Spring to late Autumn.
It is commonly found attached to the stems of water plants, the undersides of leaves, submerged twigs and on the surface of stones. When disturbed it retracts to a small brown blob which is easily overlooked. Gently sweeping through a clean weedy pond and allowing the collected water and leaves to stand in a jar will often reveal Hydra emerging after only a few minutes.
When in feeding mode, the fully extended tentacles are very long and may exceed 1 inch (25 mm) in length. In this condition the tentacles are very difficult to see with the naked eye and are often only revealed when a prey animal such as Daphnia is caught. The relative length of the tentacles compared to the body is characteristic of the species and serves to differentiate it from any other brown Hydra of cool temperate waters.
When a cold sensitive strain of H. oligactis is subjected to temperature stress, it undergoes a shift from asexual budding to sexual reproduction.[2] This shift involves an upregulation of genes involved in gametogenesis, cellular senescence, apoptosis and DNA repair, and a downregulation of genes involved in stem cell maintenance.
Hydra oligactis is preyed upon by the flatworm Microstomum lineare, which incorporates Hydra stenoteles into its own epidermis.[3][4]
Hydra oligactis, also known as the brown hydra, is a species of hydra found widely dispersed in the northern temperate zone. It is a common organism found in still waters from early Spring to late Autumn.
It is commonly found attached to the stems of water plants, the undersides of leaves, submerged twigs and on the surface of stones. When disturbed it retracts to a small brown blob which is easily overlooked. Gently sweeping through a clean weedy pond and allowing the collected water and leaves to stand in a jar will often reveal Hydra emerging after only a few minutes.
When in feeding mode, the fully extended tentacles are very long and may exceed 1 inch (25 mm) in length. In this condition the tentacles are very difficult to see with the naked eye and are often only revealed when a prey animal such as Daphnia is caught. The relative length of the tentacles compared to the body is characteristic of the species and serves to differentiate it from any other brown Hydra of cool temperate waters.
When a cold sensitive strain of H. oligactis is subjected to temperature stress, it undergoes a shift from asexual budding to sexual reproduction. This shift involves an upregulation of genes involved in gametogenesis, cellular senescence, apoptosis and DNA repair, and a downregulation of genes involved in stem cell maintenance.
Hydra oligactis is preyed upon by the flatworm Microstomum lineare, which incorporates Hydra stenoteles into its own epidermis.