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Hydra (/ ˈ h aɪ d r ə / HY-drə) is a genus of small freshwater hydrozoans of the phylum Cnidaria.They are native to the temperate and tropical regions. [2] [3] The genus was named by Linnaeus in 1758 after the Hydra, which was the many-headed beast of myth defeated by Heracles, as when the animal has a part severed, it will regenerate much like the mythical hydra's heads.
The hydra have four to twelve tentacles 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.
The lophophore surrounds the mouth and is an upstream collecting system for suspension feeding. Its tentacles are hollow, with extensions of a coelomic space thought to be a mesocoel. The gut is U-shaped with the anterior mouth at the center of the lophophore. The anus, where present, is also anterior, but is dorsal to the mouth.
Feeding and digestion [ edit ] Hydroids are usually considered to be carnivorous organisms that feed mainly on zooplankton and, while this is generally accepted for Obelia dichotoma, a study of the O. dichotoma population in the Kongsfjorden (Spitsbergen, Arctic) found that this population was more omnivorous in nature based on their diet. [ 2 ]
The linkages in a food web illustrate the feeding pathways, such as where heterotrophs obtain organic matter by feeding on autotrophs and other heterotrophs. The food web is a simplified illustration of the various methods of feeding that link an ecosystem into a unified system of exchange.
Oxsjön, a lake in Sweden. Freshwater biology focuses on environments like lakes. A pond in the Oconee River Floodplain in Georgia, whose surface is covered in duckweed but still contains fish. Freshwater biology is the scientific biological study of freshwater ecosystems and is a branch of limnology. This field seeks to understand the ...
The water vascular system is a hydraulic system used by echinoderms, such as sea stars and sea urchins, for locomotion, food and waste transportation, and respiration. [1] The system is composed of canals connecting numerous tube feet. Echinoderms move by alternately contracting muscles that force water into the tube feet, causing them to ...
Krill feeding in a high phytoplankton concentration (slowed by a factor of 12). Filter feeders are aquatic animals that acquire nutrients by feeding on organic matters, food particles or smaller organisms (bacteria, microalgae and zooplanktons) suspended in water, typically by having the water pass over or through a specialized filtering organ that sieves out and/or traps solids.