Indus River dolphin - AbsoluteAstronomy.com

The Indus River dolphin (Platanista minor) is a sub-species of freshwater or river dolphin

River dolphin

River dolphins are the four living species of dolphin that reside in freshwater rivers and estuaries. River dolphins inhabit areas of Asia and South America. They are classed in the Platanistoidea superfamily of cetaceans. Three species live in fresh water rivers. The fourth species, the La Plata...

found in the Indus River

Indus River

The Indus River is a major river which flows through Pakistan. It also has courses through China and India.Originating in the Tibetan plateau of western China in the vicinity of Lake Mansarovar in Tibet Autonomous Region, the river runs a course through the Ladakh district of Jammu and Kashmir and...

(and its Beas

Beas River

The Beas River is a river in the northern part of India. The river rises in the Himalayas in central Himachal Pradesh, India, and flows for some 470 km to the Sutlej River in the Indian state of Punjab....

and Sutlej

Sutlej

The Sutlej River is the longest of the five rivers that flow through the historic crossroad region of Punjab in northern India and Pakistan. It is located north of the Vindhya Range, south of the Hindu Kush segment of the Himalayas, and east of the Central Sulaiman Range in Pakistan.The Sutlej...

tributaries) of Pakistan

Pakistan

Pakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...

. From the 1970s until 1998, the Ganges River dolphin and the Indus dolphin were regarded as separate species; however, in 1998, their classification was changed from two separate species to subspecies of a single species (see taxonomy below).

Other names

Both subspecies: South Asian river dolphin, blind river dolphin, side-swimming dolphin
Ganges subspecies: Gangetic dolphin, Ganges Susu, Shushuk
Indus subspecies: Bhulan, Indus dolphin, Indus blind dolphin

Taxonomy

The species was described by two separate authors Lebeck and Roxburgh in the year 1801 and it is unclear to whom the original description should be ascribed. Until the 1970s the Indus and Ganges River dolphins were regarded as a single species. The two populations are geographically separate and have not interbred for many hundreds if not thousands of years. Based on differences in skull structure, vertebrae and lipid composition scientists declared the two populations as separate species in the early 1970s. In 1998 the results of these studies were questioned and the classification reverted to the pre-1970 consensus of a single species containing two subspecies until the taxonomy could be resolved using modern techniques such as molecular sequencing. Thus, at present, there are two subspecies recognized in the genus Platanista, Platanista minor (the Indus dolphin) and Platanista gangetica (the Ganges River dolphin).

Physical description

The Indus dolphin has the long, pointed nose characteristic of all river dolphins. The teeth are visible in both the upper and lower jaws even when the mouth is closed. The teeth of young animals are almost an inch long, thin and curved; however, as animals age the teeth undergo considerable changes and in mature adults become square, bony, flat disks. The snout thickens towards its end. The species does not have a crystalline eye lens, rendering it effectively blind

Blindness

Blindness is the condition of lacking visual perception due to physiological or neurological factors.Various scales have been developed to describe the extent of vision loss and define blindness...

, although it may still be able to detect the intensity and direction of light. Navigation and hunting are carried out using echolocation

Animal echolocation

Echolocation, also called biosonar, is the biological sonar used by several kinds of animals.Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects...

. The body is a brownish colour and stocky at the middle. The species has only a small triangular lump in the place of a dorsal fin

Dorsal fin

A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...

. The flippers and tail are thin and large in relation to the body size, which is about 2-2.2 metres in males and 2.4–2.6 m in females. The oldest recorded animal was a 28 year old male 199 centimetres in length. Mature adult females are larger than males. Sexual dimorphism

Sexual dimorphism

Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...

is expressed after females reach about 150 cm; the female rostrum

Rostrum (anatomy)

The term rostrum is used for a number of unrelated structures in different groups of animals:*In crustaceans, the rostrum is the forward extension of the carapace in front of the eyes....

continues to grow after the male rostrum stops growing, eventually reaching approximately 20 cm longer. Calves have been observed between January and May and do not appear to stay with the mother for more than a few months. Gestation is thought to be approximately 9–10 months.

The species feeds on a variety of shrimp and fish, including carp and catfish. Dolphins are usually encountered on their own or in loose aggregations; they do not form tight, obviously interacting groups.

Human interaction

The Indus river dolphin has been very adversely affected by human use of the river systems in the sub-continent. Entanglement in fishing nets can cause significant damage to local population numbers. Some individuals are still taken each year and their oil and meat used as a liniment, as an aphrodisiac

Aphrodisiac

An aphrodisiac is a substance that increases sexual desire. The name comes from Aphrodite, the Greek goddess of sexuality and love. Throughout history, many foods, drinks, and behaviors have had a reputation for making sex more attainable and/or pleasurable...

and as bait for catfish

Catfish

Catfishes are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the heaviest and longest, the Mekong giant catfish from Southeast Asia and the second longest, the wels catfish of Eurasia, to detritivores...

. Irrigation has lowered water levels throughout their ranges. Poisoning of the water supply from industrial and agricultural chemicals may have also contributed to population decline. Perhaps the most significant issue is the building of dozens of dams along many rivers, causing the segregation of populations and a narrowed gene pool

Gene pool

In population genetics, a gene pool is the complete set of unique alleles in a species or population.- Description :A large gene pool indicates extensive genetic diversity, which is associated with robust populations that can survive bouts of intense selection...

in which dolphins can breed. There are currently three sub-populations of Indus dolphins considered capable of long-term survival if protected.

The Indus river dolphin is listed by the IUCN as endangered on their Red List of Threatened Species and also by the U.S. government National Marine Fisheries Service

National Marine Fisheries Service

The National Marine Fisheries Service is a United States federal agency. A division of the National Oceanic and Atmospheric Administration and the Department of Commerce, NMFS is responsible for the stewardship and management of the nation's living marine resources and their habitat within the...

under the U.S. Endangered Species Act

Endangered Species Act

The Endangered Species Act of 1973 is one of the dozens of United States environmental laws passed in the 1970s. Signed into law by President Richard Nixon on December 28, 1973, it was designed to protect critically imperiled species from extinction as a "consequence of economic growth and...

External links

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