''Hydra vulgaris'', the fresh-water polyp, is a small animal freshwater hydroid with length from 10 mm to 30 mm and width about 1 mm.

Description

The hydra have four to twelve

tentacle In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work main ...

s that protrude from just outside the mouth. They feed by extending their tentacles and waiting for food to touch the tentacles. They then bring the food to their mouth, ingest and digest the organism. Anything that cannot be digested is egested. Ingestion and egestion occur through the mouth. Like other hydras, ''Hydra vulgaris'' cling to a base object with a "foot" pad, shaped like a disk. The ''Hydra'' moves by releasing its grip on its base and is carried away by the current. ''H. vulgaris'' can also move by bending over, grabbing a surface with its tentacles, releasing its grip with its "foot" and flipping over itself.

Model organism

''H. vulgaris'' is often used, like many hydra, as a

model organism A model organism (often shortened to model) is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workin ...

for morphallactic regeneration because they are easy to care for, requiring minimal direct care, and reproduce relatively quickly. It is reported that they do not undergo

senescence Senescence () or biological aging is the gradual deterioration of functional characteristics in living organisms. The word ''senescence'' can refer to either cellular senescence or to senescence of the whole organism. Organismal senescence inv ...

, making them

biologically immortal Biological immortality (sometimes referred to as bio-indefinite mortality) is a state in which the rate of mortality from senescence is stable or decreasing, thus decoupling it from chronological age. Various unicellular and multicellular species, ...

although this has been disputed.

Neurology

Having the simplest nervous system of any known organism, the neurology of ''H. vulgaris'' is of interest to the neuroscience community, in the hopes that understanding such simple circuitry will be a precedent for understanding the more complex function of brains. The nervous system and resulting behaviors have been extensively studied by

Rafael Yuste Rafael Yuste (born April 25, 1963 in Madrid) is a Spanish-American neurobiologist and one of the initiators of the BRAIN Initiative announced in 2013. He is currently a professor at Columbia University. Biography Yuste's interest in neuroscience ...

et al. , ''H. vulgaris'' is the only animal for which the connection between its neural structure and every single one of its behaviors has been solved, with the exception of the neural code of the neurons themselves.

Reproduction

This species can reproduce in three ways:

sexual reproduction Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote tha ...

budding Budding or blastogenesis is a type of asexual reproduction in which a new organism develops from an outgrowth or bud due to cell division at one particular site. For example, the small bulb-like projection coming out from the yeast cell is know ...

, and indirectly through

regeneration Regeneration may refer to: Science and technology * Regeneration (biology), the ability to recreate lost or damaged cells, tissues, organs and limbs * Regeneration (ecology), the ability of ecosystems to regenerate biomass, using photosynthesis ...

.Working with Hydra
Ward's Science 2002. When hydra reproduce sexually, simple testes, ovaries, or both will develop on the bodies of an individual. Sperm released into the environment by the testes enters the egg within the ovary. The egg forms a

chitin Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chit ...

ous exoskeleton and waits for favorable conditions before the organism will emerge. Budding occurs when conditions are favorable; proper water temperature and enough food are the major factors. A miniature adult hydra will grow out of the body of the parent hydra. Once fully developed, it will separate from the parent and continue the life cycle. Hydras use this kind of reproduction more often because it is easier and will create more hydras than other methods. The third method of reproduction is more of a survival mechanism than a reproduction mechanism. When a hydra is cut into segments, each segment, if large enough, will grow into an individual hydra sized relative to the size of the segment. This happens in other animals, such as the

starfish Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea (). Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or basket stars. Starfish ...

References

{{Taxonbar, from=Q2720227 Hydridae Animals described in 1766 Taxa named by Peter Simon Pallas