Gastrotricha

Authority:

Gastrotricha
Kingdom:	Animalia
Phylum:	Gastrotricha
Class:
Order:
Family:	'

Gastrotricha is a phylum of microscopic, aquatic animals that are found in both marine and freshwater environments. These organisms are commonly referred to as "hairybacks" due to the presence of cilia on their ventral surface, which they use for locomotion. Gastrotrichs are an important component of the meiofauna, playing a significant role in the aquatic ecosystem.

Morphology

Gastrotrichs are small, typically ranging from 50 to 500 micrometers in length. They have a simple body plan that is bilaterally symmetrical and flattened dorsoventrally. The body is covered with a cuticle that may be smooth or ornamented with scales or spines. The ventral surface is covered with cilia, which are used for movement and feeding.

The head region of gastrotrichs is distinct and often bears sensory bristles or cilia. The mouth is located at the anterior end and leads to a simple gut. Gastrotrichs lack a circulatory and respiratory system, and gas exchange occurs through the body surface.

Reproduction

Gastrotrichs reproduce both sexually and asexually. Most species are hermaphroditic, possessing both male and female reproductive organs. Asexual reproduction occurs through parthenogenesis, where females produce offspring without fertilization. Sexual reproduction involves the exchange of sperm between individuals, followed by internal fertilization.

Ecology

Gastrotrichs are found in a variety of aquatic habitats, including marine, freshwater, and brackish environments. They are an integral part of the benthic community, living in the interstitial spaces between sediment particles. Gastrotrichs feed on bacteria, algae, and detritus, contributing to the decomposition process and nutrient cycling in aquatic ecosystems.

Taxonomy

The phylum Gastrotricha is divided into two main orders:

• Chaetonotida: This order includes mostly freshwater species, although some marine species are also present. Members of this order are characterized by the presence of adhesive tubes at the posterior end.

• Macrodasyida: This order consists primarily of marine species. They are distinguished by their elongated bodies and the presence of multiple adhesive tubes along the body.

Research and Importance

Gastrotrichs are of interest to researchers studying meiofauna and the ecology of aquatic systems. They serve as bioindicators of environmental health and are used in studies of evolutionary biology due to their simple body plan and ancient lineage.

Also see

• Meiofauna
• Cilia
• Benthic zone
• Parthenogenesis
• Hermaphroditism