User:Zionix 13/sandbox

Article Evaluation
South Asian river dolphin: Everything in the article is relevant to the article topic. The article does appear to be neutral, however, many sentences are lacking citations. The article seems to be up to date on the information presented. There was recently talk to either keep two articles, the ganges river dolphin or the indus river dolphin, as separate or envelop them into the article South Asian river dolphin. Eventually they decided to redirect the two subspecies' articles to the South Asian river dolphin page. The South Asian river dolphin article was given a c-rating and is not a part of any wiki-projects.

Vision
The Platanista gangetica lacks crystalline eye lens and has evolved a flat cornea, the combination of these traits makes the eye incapable of forming clear images on the retina and renders the dolphin effectively blind. However, an anatomical study has shown that eye may serve as a light receptor. The retina contains a densely packed receptor layer, a very thin bipolar and ganglion cell layer, and a tiny optic nerve (with only a few hundred optic fibers) that are sufficient enough for the retina to act as a light-gathering component.

The dense pigmentation in the skin overlying the eye, prevents light from reaching the retina from any entrance except for a pinhole sphincter-like structure. This structure is controlled by a cone-shaped muscle layer that extends from the posterior eye orbit to the overlying eye skin layer. The sphincter-like structure is capable of sensing light, and there is some belief that it might be able to sense the direction in which the light was emitted. However, the muddy waters, or low light conditions, that the Platanista gangetica inhabit negates the use of the little vision that remains.

Vocalization[edit]
During experiments and obsrvations, Platanista gangetica has shown object-avoidance behavior in both the consistently heavily murky waters of its habitat and the clear waters of its captivity. This has suggested that the dolphin is capable of using echolocation effectively to navigate and forage for prey. However, there is limited information on how extensively vocalization is utilized between individuals. This species of river dolphin is capable of performing whistles but rarely does so, suggesting that the whistle is a spontaneous sound and not a form of communication. The Ganges river dolphin most typically makes echolocation sounds such as clicks, bursts, and twitters. Overall, the Platanista gangetica produce pulse trains that are similar in wave form and frequency to the echolocation pattern of Inia geoffrensis. Both species regularly produce frequencies lower than 15kHz and the maximum frequency is thought to fall somewhere between 15 to 60kHz.

Echolocation is also utilized for population counts by using acoustic surveying. This method is still being developed and is not heavily utilized due to cost and technical skill requirement.