SEA SNAKES AND SEA HORSES

SEA SNAKES

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Sea snakes are found throughout the tropical Pacific and Indian oceans, but are most numerous around Australia and Indonesia. Even though some species have some of the world's most toxic venoms, they are not aggressive and rarely present a threat to humans or cause human injuries or fatalities. Generally they do not bite unless they are handled. Often don't even release venom when they bite.

Sea snakes are reptiles. Most sea snakes are able to respire through their skin. This is unusual for reptiles because their skin is thick and scaly. Even so they have to come to the surface to breath. Other adaptions that sea snakes have made for marine life include nostrils that can be closed with a valve arrangement and paddle-shaped tails that improve their swimming ability. They lack the ventral scales that help terrestrial snakes move.

There are about 60 species of sea snake. They tend to have laterally flattened bodies that enable them to swim more efficiently and give them an eel-like appearance. They generally feed on fish, particularly eels. Some feed on fish eggs. Some dive deep to search for prey. Most can not survive on land. Some tie their bodies into slip knots which "they work down their length from head to tail so that one fold, as it pass over another, runs off parasites" attached to the snake's skin.

Websites and Resources: National Oceanic and Atmospheric Administration noaa.gov/ocean ; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems ; Ocean World oceanworld.tamu.edu ; Woods Hole Oceanographic Institute whoi.edu ; Cousteau Society cousteau.org ; Montery Bay Aquarium montereybayaquarium.org

Websites and Resources on Fish and Marine Life: MarineBio marinebio.org/oceans/creatures ; Census of Marine Life coml.org/image-gallery ; Marine Life Images marinelifeimages.com/photostore/index ; Marine Species Gallery scuba-equipment-usa.com/marine

Websites and Resources on Coral Reefs: Coral Reef Information System (NOAA) coris.noaa.gov ; International Coral Reef Initiative icriforum.org ; Wikipedia article Wikipedia ; Coral Reef Alliance coral.org ; Global Coral reef Alliance globalcoral.org ; Coral Reef Pictures squidoo.com/coral-reef-pictures ; The Global Coral Reef Monitoring Network; the International Coral Reef Action Network.

Sea Snake Venom

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Belcher sea snake
Sea snake venom is very toxic but a very small amount of toxin is injected with a bite. Sea snakes have difficulty penetrating wet suits. Their almost painless bites can cause a variety of muscle pains and paralysis. If enough venom is injected the victim’s legs go numb after a couple hours, his eyes and his jaw locks, and later it the worst cases he goes into convulsions and dies of respiratory failure. For many species there is an antivenin.

Powerful toxins (lethal dose): 1) anthrax (0.0002); 2) geographic cone shell (0.004); 3) textrodoxotine in the blue ring octopus and puffer fish (0.008); 4) inland taipan snake (0.025); 5) eastern brown snake (0.036); 6) Dubois’s sea snake (0.044); 7) coastal taipan snake (0.105); 8) beaked sea snake (0.113); 9) western tiger snake (0.194); 10) mainland tiger snake (0.214); 11) common death adder (0.500). Lethal doses is defined as the amount in milligrams needed to kill 50 percent of the animals tested.

In a National Geographic article from the 1960s, the writer spent some time in the Great Barrier Reef catching and studying sea snakes. One time he was bitten by a snake but his quarter inch thick west suit protected him. Another time a member of his group was bitten on his un-gloved hand but snake didn't have a chance to clamp down on him so he too was unhurt.

Seahorses

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Pygmy seahorse
Seahorses are strange-looking fish that resemble knights in a chess game and swims in an upright position. They are found in coral reefs, mangroves and particularly grass beds. There are nearly 50 species of seahorses and they can be found in coastal area in most parts of the world south of Canada and north of Tasmania. The Giant Pacific seahorses is the largest seahorse. It reaches length of 14 inches. The smallest one are the size of an ant. Seahorses belong to the pipefish family which includes about 200 species. [Source: Amanda Vincent, National Geographic, October 1994]

Seahorses have monkey-like tails that can be used to grasp things. Their bodies are encased in bony ringlike plates studded with spines. Their coronets are as unique as finger prints. Their chameleon-like eyes move independently of one another. Sometimes one eye be on the look out for predators while the other is searching for food. Seahorses are generally very well camouflaged. Some turn bright yellow to send a warning to predators. Seahorses produce noise by rubbing their head against the spines on their back.

Seahorses are slow swimmers. Unlike other fish, they tend to swim vertically rather than horizontally and seem avoid swimming as much as possible. Instead they wrap their tails around sea fans or grasses, waiting for small vertebrates to be carried their way by ocean currents. Sometime they cling to small blade of grass for days. When they swim they do so quick, fluttering dorsal fins movements. They don’t have conventional fish tails.

Seahorses have a tiny mouths. They feed on small shrimp, larval crustaceans and other zooplankton they suck in with their powerful tube-like snouts. They are preyed on by mollusks, crabs and some fish and seabirds. Many fish spit them out because they are too knobby and hard.

Seahorse Mating and Young

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Male seahorse carry the eggs of the female in kangaroo-like pouch. Like other animals males carry sperm and females have eggs. The difference is that seahorse female deposits her eggs in a a pouch male's tail, where they mix with sperm, and the male gives "birth" to the baby seahorses.

Seahorses are generally monogamous in the mating season and many are monogamous for life. Seahorses couples greet each other by jointly wrapping their tails around a blade of sea grass, touching their snouts and quivering with pleasure. They go for strolls with their tails. Females often have larger territories than males. The home range of “whitei” seahorse is limited to a square meter. His female partner is about a hundred times that size. The difference reduces competition for food.

Seahorses sometimes mate and give birth several times a year About three or four days before mating, the males develops a pouch. During the mating ritual the male shows he is "receptive" by displaying his empty pouch. If the female is attracted, the couple copulates. The two then change colors and dance around each other for hours. During the five second mating process the male and female entwine their tails and the female squirts several thousand eggs into the pouch of the male, who releases sperm from special ducts that quickly fertilizes the eggs. The pouch lining secretes a nourishing fluid absorbed by the eggs.

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Even though male seahorses play a traditionally feminine role in raising young they generally play conventional sexual roles found in the animal kingdom. Males compete against one another for females rather than visa versa. Males fighting over a female generally bash each other with their snouts,

The male does most of the parenting even though the female visits him every morning until the young are born. The male provides the young in the pouch with most of the nutrients that females in other species provide their young in the uterus. The activity is stimulated by the hormone prolactin, which stimulates milk production in women.

Seahorse eggs take about 21 days to incubate. About two weeks after they hatch from the eggs young seahorses are shot from the male’s pouch in spurts by muscle contractions. This process can go on for 24 hours or more and stops when all the babies — usually a thousand or more — are released. Regardless of species, all newborn seahorses are about a quarter to half inch in length. After they emerge the young curl their tail around the first thing they see. Juvenile seahorses rarely stray far from the home range of the parents.

Endangered Seahorses, Medicine and Trade

The A.D. first century Roman historian Pliny the Elder reported that "ashes of seahorse...mixed with soda and pig's large" cured baldness. "North in ginseng and south is seahorse" is a Chinese adage from the “Divine Pearls Herbal Compendium”. In China medicine seahorses are usually ground and mixed with herbs and other ingredients a made into a tea. They are prescribed from ailments such as asthma, atherosclerosis, dizziness, joint pain, impotence and incontinence.

Seahorse sales took off in China when the country began opening up in the 1990s. An estimated 2 million seahorse were consumed in China in 1992, a tenfold increase from the previous decade. Three million were consumed in Taiwan the same year. In Hong Kong at that time "inferior" seahorses sold for about $100 a pound. Higher quality ones went for around $400 a pound.

About 25 million of seahorses were harvested every year in the 1990s. About 95 percent of them were sold in Asia for medicines and aphrodisiacs. They are also collected alive for salt water aquarium and sold dried at souvenir shops. In the 1990s their price went up to $800 a pound.

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Wild seahorses are caught by hand, with dip nets or as bycatch from shrimp trawlers. Seahorse hunter generally go after their prey at low tide at night, A good hunter can catch 60 a night. Most are dried an so to middlemen for the Chinese medicine for about 60 cents a piece.

Seahorses are difficult to raise in captivity. They are picky eaters susceptible to disease and die easily. Thus they are difficult to raise commercially and have to be harvested in the wild. Their monogamy doesn’t serve them well. If one loses a partner he or she doesn’t chose another. The company Seahorse Ireland raises seahorses from birth and has had success getting them to mates and breed in captivity. The company sells seahorses for for $2.50 a piece over the Internet.

Seahorses have disappeared from sea grass beds and mangroves from Florida to Ecuador, and on coral reefs from India to Vietnam. Reefs in the Philippines that were once teeming with seahorses are now almost void of them. So many seahorses have been caught that many species are regarded threatened or endangered. Seahorse habitats — coral reefs, grass beds and mangroves — are increasingly under stress from dredges, overfishing, coral dynamiting and pollution.

In 2003 seahorses were declared an endangered species by The United Nations Convention on International Trade on Endangered Species (CITES). An international ban on seahorse trade was imposed unless the captive-bred or used for scientific purposes. In no-fishing zones seahorses have rebounded.

Image Source: National Oceanic and Atmospheric Administration (NOAA) Wikimedia Commons

Text Sources: Mostly National Geographic articles. Also the New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Natural History magazine, Discover magazine, Times of London, The New Yorker, Time, Newsweek, Reuters, AP, AFP, Lonely Planet Guides, Compton’s Encyclopedia and various books and other publications.

Last updated March 2011


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