Sri Lanka is an island close to the southern end of India with a tropical environment. The freshwater fauna is as large as it is common to other regions of the world. There are about two million species of arthropods found in the world, and still it is counting with many new species still being discovered. It is very complicated and difficult to summarize the exact number of species found within a certain region.
Freshwater habitats Freshwater animals are important to the economy of a country. The animal life in freshwater comprises a great diversity. The organisms ranging from tiny protozoa to large mammals in size. Sri Lanka is a hydraulic civilization. First civilizations in Sri Lanka were originated closer to main rivers in Sri Lanka such as Mahaweli, Kelani, Malwathu and Gin Ganga. Rivers in Sri Lanka flow in a radial pattern, from central hills where there are numerous waterfalls, the rivers flowing to the west, east and south being shorter than thoe flowing to north., north west and north east. Several streams join these rivers. Some of the streams in the hill country and mid country are quick flowing streams known as torrential streams.
Sri Lankan freshwater habitats can be divided into 6 major types - river, stream, lake, pond, villu and paddy field - according to size, depth, rate of flow and type of bottom. Medium-sized rivers are called Oya and fast flowing streams torrential streams are called Dola in Sinhalese. The following list provide the freshwater fauna of Sri Lanka.
Adaptations of freshwater fauna The life history of any animal is divisible into 3 phases, initially a period of slow development, followed by a rapid growth with a voracious appetite and finally to an adult which breeds at regular intervals and continue to grow slowly. Most freshwater animals breed during or after monsoon rains where water is available for the young to spread over a wide area where crowding is less and there is a plentiful supply of food in the form of minute plants and animals.
During dry season, conditions in temporary habitats become less and less favourable for aquatic animals. Those cut off in small habitats are quickly killed off, others in larger habitats survive longer. During this period, food become scarce and water level reduces. Animals become weakened or diseased and die or are eaten by birds and terrestrial animals. Many freshwater animals show adaptations to drought conditions. Fish with air breathing ability, utilize atmospheric oxygen to moisten gills, mud burrowing ability are some of them. Smaller crustaceans, produce eggs with hard resistant covering capable of surviving even a severe drought. These cysts are blown by wind and the species is dispersed. Freshwater crabs and prawns carry their eggs until they hatch out, while leeches carry the young in a pouch.
Researches on Sri Lankan freshwater fauna Knowledge of Sri Lankan freshwater fauna has been considerably enhanced in the last twenty years or so in two ways. One is through the publication of monographs. The other way is through Swedish Expedition and Smithsonian Institution. Several animals groups were identified extensively from Sri Lanka, such as fish, amphibians, odonates and arthropods. Other freshwater fauna of Sri Lanka need more detailed work, which are currently based on the notes of way back in British period. According to the National Red Data List in 2012, many freshwater habitats are degraded at an alarming rate due to rapid human interference. Habitat destruction, fragmentation and loss of forest cover has increased in past decade rapidly. The result becomes severe, where many amphibians have been not recorded after their discovery, which led the scientists to categorize Sri Lanka as a biodiversity hotspot.
Protozoa
Family: Amoebidae Phylum: Amoebozoa Class: Tubulinea Order: Tubulinida Amoeba verrucosa
Family: Actinophryidae Phylum: Ochrophyta Order: Actinochrysophyceae
Actinophrys sol
Family: Arcellidae Phylum: Amoebozoa Class: Tubulinea Order: Arcellinida Arcella discoides Arcella vulgaris Sphenoderia lenta
Family: Centropyxidae Phylum: Amoebozoa Class: Tubulinea Order: Arcellinida Centropyxis aculeata
Family: Ceratiaceae Phylum: Dinoflagellata Class: Dinophyceae Order: Gonyaulacales Ceratium hirudinella
Family: Clathrulinidae Phylum: Cercozoa Class: Granofilosea Order: Desmothoracida Clathrulina elegans
Family: Codonellidae Phylum: Ciliophora Class: Oligotrichea Order: Choreotrichida Codonella lacustris Tintinnopsis ovalis
Family: Difflugiidae Phylum: Amoebozoa Class: Tubulinea Order: Arcellinida Difflugia acuminata Difflugia arcula Difflugia constricta Difflugia corona Difflugia globulosa Difflugia lobostoma Difflugia pyriformis Difflugia urceolata Lesquereusia spiralis
Family: Epistylididae Phylum: Ciliophora Class: Ciliatea Order: Sessilida Epistylis anastatica
Family: Euglenaceae Phylum: Euglenozoa Class: Euglenoidea Order: Euglenales Euglena sp.
Family: Euglyphidae Phylum: Cercozoa Class: Imbricatea Order: Euglyphida Euglypha alveolata Euglypha ciliata Trinema enchelys
Family: Glaucomidae Phylum: Ciliophora Class: Oligohymenophorea Order: Tetrahymenida Colpoda cucullus
Family: Hyalospheniidae Phylum: Amoebozoa Class: Tubulinea Order: Arcellinida Hyalosphenia elegans Hyalosphenia papilio
Family: Ichthyophthiriidae Phylum: Ciliophora Class: Oligohymenophorea Order: Hymenostomatida Ichthyophthirius multifiliis
Family: Oxytrichidae Phylum: Ciliophora Class: Spirotrichea Oxytricha mystacea Stylonychia pustulata
Family: Parameciidae Phylum: Ciliophora Class: Oligohymenophorea Order: Peniculida Paramecium sp.
Family: Pelomyxidae Phylum: Amoebozoa Class: Archamoebae Order: Pelobiontida Pelomyxa quarta
Family: Peridiniaceae Phylum: Myzozoa Class: Dinophyceae Order: Peridiniales Peridinium tabulatum
Family: Trichodinidae Phylum: Ciliophora Class: Oligohymenophorea Order: Peritrichida Cyclochaeta domerguei
Family: Volvocaceae Phylum: Chlorophyta Class: Chlorophyceae Order: Chlamydomonadales Volvox aureus
Family: Vorticellidae Phylum: Ciliophora Class: Oligohymenophorea Order: Sessilida Vorticella sp.
Moss animals Phylum: Bryozoa Class: Phylactolaemata Order: Plumatellida
Family: Pectinatellidae Pectinatella burmanica
Family: Plumatellidae Plumatella emarginata Plumatella longigemmis
Hairybacks Phylum: Gastrotricha Order: Chaetonotida
Family: Chaetonotidae Chaetonotus (Chaetonotus) larus Ichthydium (Ichthydium) podura
Sponges Phylum: Porifera Class: Demospongiae Order: Spongillida
Family: Spongillidae Eunapius carteri Radiospongilla cerebellata
Cnidarians Phylum: Cnidaria Class: Hydrozoa Order: Anthoathecata
Family: Hydridae Hydra Vulgaris Hydra zeylandica
Wheel animals Phylum: Rotifera
Sri Lankan freshwaters are home for 124 species of wheel animals.
Flatworms Phylum: Xenacoelomorpha Order: Acoela
Family: Convolutidae Convoluta anotica
Phylum: Platyhelminthes Order: Rhabdocoela
Family: Scutariellidae Caridinicola platei Monodiscus macbridei Monodiscus parvus
Family: Typhloplanidae Mesostoma ehrenbergii Strongylostoma radiatum
Phylum: Platyhelminthes Class: Trematoda Order: Plagiorchiida
Family: Pleurogenidae Pleurogenoides sitapuri
Phylum: Platyhelminthes Class: Cestoda Order: Bothriocephalidea
Family: Bothriocephalidae Senga lucknowensis
Roundworms Phylum: Nematoda Class: Enoplea Order: Dorylaimida
Family: Dorylaimidae Dorylaimus sp.
Class: Chromadorea Order: Rhabditida
Family: Camallanidae Zeylanema anabantis Zeylanema fernandoi Zeylanema kulasirii Zeylanema mastacembeli Zeylanema pearsi Zeylanema sweeti Procammallanus spiculogubernaculus Procammallanus planoratus
Gordian worms Phylum: Nematomorpha Class: Gordioida Order: Chordodea
Family: Chordodidae Chordodes skorikowi Chordodes verrucosus Paragordius tricuspidatus
Segmented worms Phylum: Annelida
Family: Aeolosomatidae Aeolosoma ternarium
Class: Clitellata Order: Haplotaxida
Family: Naididae Allonais paraguayensis Aulophorus michaelseni Aulophorus tonkinensis Bothrioneurum iris Chaetogaster sp. Dero digitata Dero zeylanica Limnodrilus hoffmeisteri Pristina (Pristina) breviseta Pristina (Pristina) proboscidea
Family: Almidae Glyphidrilus sp.
Order: Rhynchobdellida
Family: Ozobranchidae Ozobranchus shipleyi
Family: Galeommatidae Hirudinaria manillensis
Family: Glossiphoniidae Paraclepsis vulnifera Placobdella ceylanica Placobdella emydae Placobdella undulata Limnatus paluda Dinobdella ferox
Order: Arhynchobdellida
Family: Hirudinidae Hirudo birmanica Hirudinaria manillensis
Molluscs Phylum: Mollusca Class: Gastropoda Order: Cycloneritida
Family: Neritidae Septaria livesayi Septaria reticulata Septaria squamata Theodoxus perotetiana
Order: Caenogastropoda
Family: Pachychilidae Faunus ater Melanoides broti Melanoides crenulata Melanoides lineata Melanoides tuberculata
Family: Thiaridae Thiara datura Thiara rudia Thiara scabra
References