Benthos refers to the benthic invertebrate community, which is a group of animals that live on or in the bottom sediments of different waterbodies. The benthic community includes a wide variety of organisms including clams, oysters, small shrimp-like crustaceans, and the blood and clamworms. These communities very much depended on some abiotic factors such as depth of water, temperature, turbidity, and salt content. Fluctuations of any of those parameters result in changes on species composition and the numbers of individuals. A study was conducted in three ponds and Padma River at Rajshahi city to assess the benthic organism’s diversity and following benthos were recorded:
Tubifex is a fresh water worm, occurs in patches on the muddy bottom in the fresh water pond sand lakes. Ecologically, it is important as a source of food for leeches, crustaceans, insects, and fishes. Tubifex are sold to aquarists as fish-food in both live and freeze dried, pelletised forms. These worms are relatively easy to culture, but it takes a month or more to get a culture going to the point that it is ready to harvest.
Limnodrilus hoffmeisteri is a small, thin worm about 20-35 mm in length. It has a wide ecological range and inhabits cohesive muds in all types of waters including polluted, but it cannot tolerate oxygen deficiency. Although a freshwater species it is found further seaward than any other freshwater aquatic oligochaete species and is found in habitats likely to be exposed to very low salt levels, e.g. upper estuaries where interstitial salinity is less than 5 psu.
Pheretima is commonly known as earthworm. Pheretima is a genus of earthworms found mostly in New Guinea and parts of Southeast Asia. Pheretima posthuma is found in moist soil almost all over the world.
The widely distributed but rare leech Glossiphonia was collected for the first time in a eutrophic ditch. Glossiphonia is small fresh-water leach found feeding on molluses, e.g., Lymnaea, Planorbis and chironomous larvae.
Cancer is commonly known as rock crab or tube-crab. Crabs are mostly active animals with complex behavior patterns.
Pila globosa is commonly known as apple snail. Apple snails inhabit a wide range of ecosystems from swamps, ditches and ponds to lakes and rivers. Not every species has similar preferences. However, most apple snails prefer lentic waters above turbulent water (rivers). Inhabits a large area from North-Central India to Bankok.
Lymnaea is commonly known as pond snail. Lymnaea is a widely distributed inhabitant of freshwater ponds, lakes and rivers rich in vegetation and is found throughout Europe, the Northern United States and parts of Asia. The snails are from 2 to 5 cm in shell length and typically are found in large numbers close to the water surface and feeding on floating pond weed. They also feed on algae, detritus and carrion and so are generalists in their feeding habits.
Unio is commonly known as fresh-water mussel. Unionids are found in various permanent freshwater sources such as lakes, streams, and rivers. Unio occur in North America, Europe, Asia, Africa, and the Indonesian Archipelago. Adult freshwater mussels are filter feeders; they continuously filter food particles out of the water.
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