List of freshwater fauna of Sri Lanka

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.

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: Epistylidae
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