Sea Snake

Sea snakes, or coral reef snakes are also known as ocean snakes. Sea snakes belong to the subfamily Hydrophiinae and live in marine environments for most or their entire lives. Most ocean snakes are widely adapted to fully aquatic organisms and cannot move on land, except for the Laticauda genus, which has limited land movement. They live in warm coastal waters from the Indian Ocean to the Pacific Ocean and are closely related to the venomous land snakes of Australia. All sea snakes have paddle-like tails, and many sea snakes have their bodies compressed laterally, making them look like eels. Unlike sea snake fish, they have no gills and must get on the surface regularly to breathe. Like whales, they are one of the most aquatic-breathing vertebrates. In this group, there are some venomous snakes that are the most venomous of all snakes. Some have a mild personality and only bite when provoked, but some are more aggressive. Currently, there are 17 genera, including 69 species, described as sea snakes or ocean snakes. We will understand more about the types of sea snakes and also see how do sea snakes swim.  

Snake 

Snake is a slender carnivorous reptile, without limbs, belonging to the suborder of Serpentes. Like all other squamates, snakes are amniotic vertebrates with abnormal body temperature, covered with overlapping scales. Many types of snakes have more articulated skulls than their lizard ancestors, which allows them to swallow prey much larger than their heads with highly flexible jaws. In order to adapt to their narrow bodies, snake paired organs such as kidneys appear to face each other rather than side by side, and most have only one functional lung. Some species retain a pair of residual claw pelvic girdles on each side of the cloaca. Lizards independently developed thin bodies without limbs or severely reduced limbs about 25 times through convergent evolution, resulting in many lineages of legless lizards. They are similar to snakes, but some common legless lizards have eyelids and outer ears, whereas snakes do not have all of these. Live snakes are found on all continents except Antarctica and most of the smaller lands, exceptions include some large islands such as Ireland, Iceland, Greenland, the Hawaiian Islands, and the New Zealand Islands, as well as many in the Atlantic and central Pacific. Island. Additionally, sea snakes are found throughout the Indian Ocean and the Pacific Ocean. There are currently more than 20 confirmed families, which include around 520 genera and around 3,900 species. They range in size from the tiny 10.4 centimeter that is the  Barbados thread snake to the seven meter-long reticulated python. The fossil species Titanoboa cerrejonensis is 12.8 meters long. Snakes are believed to have evolved from burrowing lizards or aquatic lizards, probably during the Jurassic period. Most types of snakes are non-venomous. Venomous snakes are mainly used to kill and subdue prey, not for defense. Some possess powerful poisons that can cause painful harm or death to humans. Non-venomous snakes either swallow their prey alive or kill it by shrinking. Snakeskin is covered with scales. Contrary to popular belief that snakes are slimy, snakeskin has a smooth and dry texture. Most snakes use specialized abdominal scales for travel, allowing them to attach to the surface. The body scales can be smooth, basal, or granular. The eyelids of a snake are transparent spectacles scales, also called brille, which are permanently closed. The shedding of scales is called molting. The snake shed the entire outer layer of skin. Snake scales are not discrete, but extensions of the epidermis, therefore, they do not fall off individually but fall off as a complete outer layer during each molt. Snakes have a variety of skin color patterns. These patterns are usually related to behavior, such as the tendency to escape from predators. Snakes with a high risk of predation are often smooth or longitudinally striped, and rarely provide a reference point for predators, allowing the snake to escape without being noticed. Simple snakes usually adopt active hunting strategies because their mode allows them to send very little information about the movement to their prey. Spotted snakes often use ambush-based strategies, probably because this helps them blend into the environment with irregularly shaped objects such as sticks or rocks. The spot pattern can also help the snake blend into the environment. The shape and number of scales on the head, back, and abdomen are usually characteristic and used for classification purposes. The scales are named mainly according to their position on the body. In Caenophidian snakes, the broad abdominal scales and rows of dorsal scales correspond to the vertebrae, so they can be counted without dissection. 

Distribution of Sea Snakes 

Sea snakes live primarily in the warm tropical waters of the Indian Ocean and the Western Pacific. They are underwater snakes. Some species are distributed in Oceania. With the exception of a few species of sea turtles, Pelamis platurus has a wider geographic range than any other species of reptile. It begins on the east coast of Africa, from Djibouti in the north to Cape Town in the south, through the Indian Ocean, the Pacific Ocean, and up the north coast of New Zealand in the south. All the way to the west coast of America, it is found in northern Peru in the south including the Galapagos Islands to the Gulf of California in the north. Isolated specimens were found in San Diego and Oxnard in the northern United States. Sea snakes do not appear in the Atlantic Ocean. Sea snakes are found in the oceanic currents and seas where the salinity in the water is very high. Despite their strong adaptability to the ocean, most sea snakes prefer to be close to land, in shallow waters around islands, especially in some hidden waters, and near estuaries. Some sea snakes inhabit mangroves and similar brackish water habitats, and two forms of inland freshwater have been discovered, Hydrophis semperi on Lake Taal in the Philippines and Laticauda crockery on Rennell Island, Solomon Islands Te Nagano in Lake Te Nagano. 

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Body Structure 

The length of most adult sea snakes is between 120 and 150 centimeters. The largest sea snake can reach a maximum of 3 meters. Their eyes are relatively small, their pupils are round and most of their nostrils are located at the back. Although their dentition is relatively primitive, with short teeth and up to 18 smaller teeth in the maxilla, their skulls are not significantly different from those of elapids on land. Most sea snakes are completely aquatic and adapt to the marine environment in many ways, the most distinctive of which is the paddle-like tail, which enhances their ability to swim. To varying degrees, the bodies of many species are laterally compressed, especially pelagic species. This generally makes the ventral scales smaller and even difficult to distinguish from adjacent scales. Their lack of belly scales means that they become almost defenseless on land, but when they spend their entire life cycle in the sea, they don't need to get out of the water. The only genus that retains enlarged belly scales is Laticauda, ​​which has only five species. These snakes are considered more primitive because they still spend most of their time on land and the scales on their belly provide the necessary grip. The Laticauda species is also the only sea snake with nasal scales. Since a snake's tongue is easier to perform its olfactory function underwater, its effect is shorter than that of a land snake. Only the forked tip protrudes from the mouth through a separate notch in the middle of the bill's scales. There are valves in the nostrils, which are made of a special sponge tissue to remove water. The trachea can be raised to the position where the short nasal passage leads to the top of the mouth. This is an important adaptation for animals that must surface to breathe but can partially submerge their heads in the water while doing so. The lungs become very large, extending almost the entire length of the body, although it is thought that the back has developed to help buoyancy rather than exchange gas. The expanded lung may also be used to store air for diving. Most types of sea snakes can breathe through the upper part of their skin. This is unusual for reptiles because their skin is thick and scaly, but experiments with the black and yellow sea snake Pelamis pleura show that this species can meet approximately 25% of its oxygen requirements. Like other terrestrial animals adapted to live in the marine environment, sea snakes consume much more salt than their land relatives through diet and unintentional intake of seawater. This means that they must develop a more effective method to regulate the salt concentration in the blood. In sea snakes, the posterior sublingual glands located under and around the tongue sheath evolved to allow them to expel salt through the action of the tongue. 

Climbing in the sea snake changes a lot. Unlike land snakes, which have overlapping scales to prevent abrasion, the scales of most pelagic sea snakes do not overlap. Coral reef-dwelling species, such as Aipysurus, have tile scales to protect sharp corals. The scales themselves can be smooth, keel-shaped, spiny, or grainy, with the latter often resembling warts. The scales on the body of Peramis are like nails, and the scales on the tail are hexagonal plates side by side. 

Sensory Abilities of Sea Snakes

Vision, chemical sensation, and hearing are the important senses of land snakes, but these stimuli can be distorted in water. The limitations of low visibility, chemical dilution, and underwater ground vibration indicate that sea snakes and sea ring snakes may have unique sensory abilities to compensate for the relative lack of other sensory cues. Very little is known about the vision of the sea serpent. A study of retinal photoreceptors from the spiny-bellied sea snake, Lapemis curtus, and the horned sea snake Acalyptophis peronii found that all three types of visual pigments come from cone cells. There are no rod-shaped cells in the eyes of sea snakes. The discovery that the rod-shaped cell gene that is rh1 is still expressed indicates that in marine snakes, some cone cells can transform into rod-shaped cells. However, behavioral observations indicate that vision has a limited role in prey capture and mate selection, but sound vibrations and chemical sensations may be important. One study found that the small sensory organs in the head of Lapemis curtus are similar to the mechanoreceptors of the alligator and the water snake Acrochodus, which are used to detect the movement of fish prey. In the same way, the vision seems to be important for the vision of finding friends. The secretion of the skin is known as pheromones. The brightness can be useful in a short vision distance, but it was found that the pheromone is more important when men physically contact the object.  Other unique detection, such as electromagnetic reception and pressure detection, has been proposed for the maritime serpent, but scientific research is carried out to test that these senses are present or not. 

Internal Organs

Snakes and other reptiles have a three-chambered heart that controls the circulatory system through the left and right atria and ventricles. Internally, the ventricle is divided into three interconnected chambers that are the arterial cavity, the pulmonary cavity, and the venous cavity. The venous cavity receives deoxygenated blood from the right atrium, and the arterial cavity receives oxygenated blood from the left atrium. Located below the venous cavity is the pulmonary venous cavity, which pumps blood to the lung trunk. The heart of the snake is wrapped in a sac called the pericardium, located at the bifurcation of the bronchi. Due to the lack of a diaphragm, the heart can move when a large amount of ingested prey passes through the esophagus, this setting can protect the heart from possible damage. The spleen attaches to the gallbladder and pancreas and filters blood. The thymus is located in the fatty tissue above the heart and is responsible for generating immune cells in the blood. The cardiovascular system of snakes is unique in that there is a renal hilar system in which the blood from the snake's tail passes through the kidneys before returning to the heart. The remaining left lung is usually very small, sometimes even absent, because the tubular body of snakes requires all of its organs to be long and slender. In most species, only one lung is functional. This lung contains a vascularized front part and a back part that does not exchange gas. This cystic lung is used hydrostatically to adjust the buoyancy of some aquatic snakes, and its role in terrestrial species is still unknown. Many paired organs, such as the kidneys or reproductive organs, are staggered in the body, facing each other. The snakes does not have lymph nodes. 

Hydrophis Snake 

Hydrophis snake Belcheri is generally known as North-Cand Sea Snake and Bersian Sea Snake. Hydrophis snake has a timid temperament and, usually, it bites when provoked. Belcher's Sea Snake is medium in size in the range of 0.5 to 1 meter with adult length. The slim body generally has a dark green crossed band with yellow. The dorsal pattern has not been extended to Ventura. The head is short and there is a band of the same color. The mouth is very small but suitable for aquatic organisms. The body seems to have a wonderful yellow color when seen from the water. The scale is different from most other snakes, as they overlap each other. Each rear scale has a tuberculosis center. The body is strongly compressed backward. Because the scales on the ventral side are very narrow, they will be slightly wider than the later scale.