Chinese name: Dugong

Chinese aliases: manatee, "seahorse", mermaid, mermaid, South China Sea cow.

Latin scientific name: dugong? Dugan

Species Nomenclature:? Muller 1776

English name: Dugong

Classification:

Door: Chordata door? (Chordata)

Class: Mammals? (mammal)

Order: Manatee? (Sirius)

Family: Dugong family? (dugong family)

Genus: Dugong? (Dugong)

Appearance characteristics

It is the only herbivorous mammal in the ocean. The biggest difference between it and other manatees is that the tail of manatees is round, while the tail of dugong is similar to that of dolphins. Dugong's head is very big, and the ratio of head to body is the largest among marine animals. The mouth is huge and vertical, and the tongue is big, so it is easier to eat marine benthos and exclude sand. Dugong's stomata are on the top of the head, and it takes air every 15 minutes on average. The skin on the head and back is hard and thick.

Dugong is large and spindle-shaped, with a body length of about 2.4 to 2.7 meters. Individuals over 3 meters are quite rare. Generally speaking, women are a little older than men. Smooth skin, brown to dark gray appearance, lighter abdomen color than back, and sparse hair on body surface. The neck is short, but you can still turn your head or nod in a limited way. The forelimbs are short, fin-shaped, with slightly rounded ends and no toenails; The pectoral fin is the main source of propulsion for young dugong, and it turns into caudal fin in adulthood. There are 1 pairs of breasts, and nipples are located at the base of forelimbs. Dugong has no outer ear shell, only small ear holes and small eyes. The nostrils are located at the top of the snout and are covered with a film when diving. The wide and flat mouth is located below the thick snout, and the short beard of the mouth is an important tool for eating.

There are two pairs of incisors, three pairs of premolars and three pairs of molars in the upper and lower jaws of dugong, but all the teeth do not exist at the same time. As they get older, they will lose the first 1 pair of incisors, all premolars and the first 1 pair of molars, and the remaining two pairs of molars will grow for life. The second pair of male front teeth will penetrate the upper jaw at the age of 12- 15, but will be covered by a thick upper lip when opening the mouth. Women rarely see exposed front teeth, but a few will stay until they are around 30 years old.

Dugong's lungs are very large, extending from the chest to the kidneys and separated from other organs by a horizontal diaphragm. Bronchus penetrates into most areas of the lung, with few branches, and most of them are composed of cartilage. It is not clear whether dugong's lungs will collapse like whales when diving. Compared with other marine mammals, their fat layer is thinner, and there seems to be no heat countercurrent exchange system around their bodies (heat? Countercurrent? Exchange? System, a vascular structure in which arteries and veins at the ends of limbs are close to each other to maintain body temperature, may be related to their living in a warm ocean. The structure of the stomach is simple, and the large intestine is very large (twice as heavy as the stomach), which is supposed to be the main digestion place of cellulose, with a length of more than 25 meters, which is equivalent to twice the length of the small intestine.

Basic information:

Length and weight at birth: 1. 15m, 25-35kg.

Maximum length and weight record: 4. 16m, 1.0 16kg.

Life expectancy: 73 years.