Harpacticoida

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Harpacticoida
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Hexanauplia
Order:	Harpacticoida
Family:	'

Harpacticoida is an order of copepods, a group of small crustaceans found in marine and freshwater environments. They are distinguished by their short, robust bodies and the presence of a reduced number of swimming legs compared to other copepods. Harpacticoids are primarily benthic, meaning they live on or near the bottom of aquatic environments, and they play a crucial role in the aquatic food web as both grazers and prey.

Morphology

Harpacticoid copepods are characterized by their compact body shape, which is typically less than 1 mm in length. They have a segmented body divided into a cephalothorax and an abdomen. The cephalothorax bears a pair of antennae, which are used for locomotion and sensory perception. Unlike other copepods, harpacticoids have a reduced number of swimming legs, usually five pairs, which are adapted for crawling rather than swimming.

Ecology

Harpacticoids are found in a wide range of aquatic habitats, from the deep sea to freshwater lakes and rivers. They are particularly abundant in marine sediments, where they feed on detritus, algae, and microorganisms. Their role as detritivores and grazers makes them important in nutrient cycling and energy transfer within aquatic ecosystems. Harpacticoids are also a key food source for many fish and invertebrates.

Reproduction

Harpacticoid copepods reproduce sexually, with separate male and female individuals. Females carry eggs in external sacs until they hatch into nauplius larvae. The larvae undergo several molts before reaching adulthood. The life cycle of harpacticoids is relatively short, allowing them to rapidly colonize new habitats and respond to changes in environmental conditions.

Taxonomy

The order Harpacticoida is divided into several families, including Ameiridae, Canthocamptidae, and Tisbidae. Each family contains numerous genera and species, reflecting the diversity and adaptability of harpacticoids to different ecological niches.

Research and Importance

Harpacticoid copepods are used as model organisms in ecological and environmental research due to their sensitivity to pollutants and changes in habitat conditions. They are also studied for their role in sediment bioturbation and their interactions with other benthic organisms.

Also see

• Copepoda
• Crustacea
• Benthic zone
• Marine biology
• Aquatic ecosystems