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Amazonian manatee
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Amazonian manatee
The Amazonian manatee (Trichechus inunguis), commonly referred to as cowfish (Portuguese: peixe-boi) in Brazil, is a species of manatee that lives in the Amazon Basin in Brazil, Peru, Colombia and Ecuador. It has thin, wrinkled brownish or gray colored skin, with fine hairs scattered over its body and a white chest patch. It is the smallest of the three extant species of manatee.
The specific name, inunguis is Latin for "nailless". The genus name Trichechus, comes from Latin meaning "hair", referencing the whiskers around the manatee's mouth.
The Amazonian manatee is the smallest member of the manatee family and can be distinguished by its smoother rubbery skin and lack of vestigial nails on its flippers. Ranges of body weight and size observed are 7.5–346 kg (17–763 lb) and 76.0–225 cm (2 ft 5.9 in – 7 ft 4.6 in) for captive males, 8.1–379 kg (18–836 lb) and 71.0–266 cm (2 ft 4.0 in – 8 ft 8.7 in) for captive females, and 120.0–270 kg (264.6–595.2 lb) and 162.0–230 cm (5 ft 3.8 in – 7 ft 6.6 in) for free-ranging manatees, respectively. The maximum actual Amazonian manatee weight reported is 379 kilograms (836 lb). Calves of the species are born weighing 10–15 kg (22–33 lb) and 85–105 cm (33–41 in) long. The Amazonian Manatees increase in length approximately 1.6-2.0 mm per day. This length is measured along the curvature of the body so absolute length can differ between individuals. As calves, they gain an average of 1 kilogram per week.
Amazonian manatees are large, cylindrically shaped mammals, with forelimbs modified into flippers, no free hind-limbs, and the rear of the body in the form of a flat, rounded, horizontal paddle. The flexible flippers are used for aiding motion over the bottom, scratching, touching, and even embracing other manatees, and moving food into and cleaning the mouth. The manatee's upper lip is modified into a large bristly surface, which is deeply divided. It can move each side of the lips independently while feeding. The general coloration is grey, and most Amazonian manatees have a distinct white or bright pink patch on the breast.
Amazonian manatees, similar to all living manatee species in the family Trichechidae, have polyphyodont teeth. Their teeth are continuously replaced horizontally from the caudal portion of the jaw to the rostral portion throughout the manatee's life, a unique trait among mammals. Only the closest living relative of order Sirenia, elephants, show a similar characteristic of teeth replacement, but elephants have a limited set of these replacement teeth. As the teeth migrate rostrally in the manatee, the roots will be resorbed and the thin enamel will wear down until the tooth is eventually shed. Referred to as cheek teeth, differentiation of manatee teeth into molars and premolars has not occurred, and manatees additionally do not have incisors or canine teeth. These teeth migrate at a rate of about 1–2 mm/month, based on wear and chewing rates.
The Amazonian manatee lacks nails on its flippers, setting it apart from other manatees. Additionally, Amazonian manatees have a very small degree of rostral deflection (30.4°), which can be used as an indication of where in the water column the animal feeds. A small degree of deflection means that the end of the snout is straighter with regard to the caudal portion of the jaw. Animals with a greater degree of deflection, such as D. dugong at about 70° of deflection, are more of a benthic species, feed on the seafloor, and have snouts that point almost completely ventrally. Only T. senegalensis has a smaller rostral deflection of about 25.8°. This is believed to maximize the efficiency of feeding. A small degree of rostral deflection allows Amazonian manatees to feed more effectively at the surface of the water, where much of their food is found.
The Amazonian manatee is the only sirenian that lives exclusively in freshwater habitat. The species relies on changes in the peripheral circulation for its primary mechanism for thermoregulation by using sphincters to deflect blood flow from areas of the body in close contact with water. They also rely on subcutaneous fat to reduce heat loss.
Manatees have nostrils, not blowholes like cetaceans, which close when underwater to keep water out and open when above water to breathe. Although manatees can remain under water for extended periods, surfacing for air about every five minutes is common. The longest documented submergence of an Amazonian manatee in captivity is 14 minutes.
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Amazonian manatee
The Amazonian manatee (Trichechus inunguis), commonly referred to as cowfish (Portuguese: peixe-boi) in Brazil, is a species of manatee that lives in the Amazon Basin in Brazil, Peru, Colombia and Ecuador. It has thin, wrinkled brownish or gray colored skin, with fine hairs scattered over its body and a white chest patch. It is the smallest of the three extant species of manatee.
The specific name, inunguis is Latin for "nailless". The genus name Trichechus, comes from Latin meaning "hair", referencing the whiskers around the manatee's mouth.
The Amazonian manatee is the smallest member of the manatee family and can be distinguished by its smoother rubbery skin and lack of vestigial nails on its flippers. Ranges of body weight and size observed are 7.5–346 kg (17–763 lb) and 76.0–225 cm (2 ft 5.9 in – 7 ft 4.6 in) for captive males, 8.1–379 kg (18–836 lb) and 71.0–266 cm (2 ft 4.0 in – 8 ft 8.7 in) for captive females, and 120.0–270 kg (264.6–595.2 lb) and 162.0–230 cm (5 ft 3.8 in – 7 ft 6.6 in) for free-ranging manatees, respectively. The maximum actual Amazonian manatee weight reported is 379 kilograms (836 lb). Calves of the species are born weighing 10–15 kg (22–33 lb) and 85–105 cm (33–41 in) long. The Amazonian Manatees increase in length approximately 1.6-2.0 mm per day. This length is measured along the curvature of the body so absolute length can differ between individuals. As calves, they gain an average of 1 kilogram per week.
Amazonian manatees are large, cylindrically shaped mammals, with forelimbs modified into flippers, no free hind-limbs, and the rear of the body in the form of a flat, rounded, horizontal paddle. The flexible flippers are used for aiding motion over the bottom, scratching, touching, and even embracing other manatees, and moving food into and cleaning the mouth. The manatee's upper lip is modified into a large bristly surface, which is deeply divided. It can move each side of the lips independently while feeding. The general coloration is grey, and most Amazonian manatees have a distinct white or bright pink patch on the breast.
Amazonian manatees, similar to all living manatee species in the family Trichechidae, have polyphyodont teeth. Their teeth are continuously replaced horizontally from the caudal portion of the jaw to the rostral portion throughout the manatee's life, a unique trait among mammals. Only the closest living relative of order Sirenia, elephants, show a similar characteristic of teeth replacement, but elephants have a limited set of these replacement teeth. As the teeth migrate rostrally in the manatee, the roots will be resorbed and the thin enamel will wear down until the tooth is eventually shed. Referred to as cheek teeth, differentiation of manatee teeth into molars and premolars has not occurred, and manatees additionally do not have incisors or canine teeth. These teeth migrate at a rate of about 1–2 mm/month, based on wear and chewing rates.
The Amazonian manatee lacks nails on its flippers, setting it apart from other manatees. Additionally, Amazonian manatees have a very small degree of rostral deflection (30.4°), which can be used as an indication of where in the water column the animal feeds. A small degree of deflection means that the end of the snout is straighter with regard to the caudal portion of the jaw. Animals with a greater degree of deflection, such as D. dugong at about 70° of deflection, are more of a benthic species, feed on the seafloor, and have snouts that point almost completely ventrally. Only T. senegalensis has a smaller rostral deflection of about 25.8°. This is believed to maximize the efficiency of feeding. A small degree of rostral deflection allows Amazonian manatees to feed more effectively at the surface of the water, where much of their food is found.
The Amazonian manatee is the only sirenian that lives exclusively in freshwater habitat. The species relies on changes in the peripheral circulation for its primary mechanism for thermoregulation by using sphincters to deflect blood flow from areas of the body in close contact with water. They also rely on subcutaneous fat to reduce heat loss.
Manatees have nostrils, not blowholes like cetaceans, which close when underwater to keep water out and open when above water to breathe. Although manatees can remain under water for extended periods, surfacing for air about every five minutes is common. The longest documented submergence of an Amazonian manatee in captivity is 14 minutes.
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