To the average person, you may not believe it is a true fish at first glance. Maybe you would not understand its peculiar looks and characteristics. The name itself suggests some kind of unusual or perhaps mythological creature, along the likes of things such as the unicorn, loch nest monster, or even big foot. It is in fact, true, a Seahorse is nothing more than a fish in the ocean. Now, it doesnÕt have scales, and it doesnÕt swim on its stomach like most, actually as I go on, there is nothing about it that relates to a regular fish except that it lives in the water. I had always thought of these sea horses to be rather unusual and perhaps not even existing. However, this past spring on a visit to the RipleyÕs Aquarium in Gatlinburg, TN I found a tank full of these creatures and was most amazed. There are so many things about sea horses that make them unique. Sure, every fish in the sea has its own characteristics, habits and lifestyle, but to me it seems as if they all pretty much relate in the same kind of ways. It is the sea horse that is most mysterious.
Characteristics and Physiology
Ò In the sea horse, nature has assembled individual adaptations of parts of several other animals and thus, produced an incredible fish that brings squeals of delight from children and exclamations of astonishment from adultsÓ (Bellomy 19). What make a Sea horse so interesting are all the neat little characteristics that define it. First of all as mentioned before, a Sea horse is a fish, and like all fish it is cold-blooded. It also breathes through gills, which draw oxygen out of the water and send it through the body. However the gills that they have are slightly different by being small and compacted. The Latin genus given is Hippocampus, which fittingly stands for ÒhorseÓ and Òsea-monsterÓ, and is part of the family Syngnathidae, which means Òfused jawsÓ, relating to the long tube shaped snout. The closest relatives are the Pipefish and the Leafy Sea dragon. The life span of a sea horse can range anywhere between a few months to over five or six years depending on the species.
The sea horse has a tail like a monkey, a head like a horse, eyes like a chameleon, a body that is armor plated like an insectÕs, and well supplied with skeletons, having one inside and one outside (Bellomy 19).
First, weÕll talk about the skeletons. The Sea horse has two, as mentioned, one on the inside and one on the outside. The armor on the outside is composed of plates, which interlock with each other and form rings around the Sea horses body. These are made of dermal cirri, which are basically tiny skin covered knobs, flaps and spines (to me they often look like unwanted tumors or growths but in reality are just its physical definition). Different species and ages of sea horses can determine the numbers of rings that form around them. This is very useful it determining the different types of sea horses. At the top of the sea horses head there is a crown-like group of cirri, spines and flaps that form a coronet, which is as unique as a human fingerprint. The rings are ridged and give the sea horse a protective layer from predators. Their exoskeleton makes digestion and swallowing difficult for bigger fish in the sea, often times sea horses are spit out because they are to hard to swallow. On adult sea horses, over 50 of these ridges or rings can be counted from head to tail. The sea horses internal skeleton is connected to a backbone, making it a vertebrate like other fish.
The head of a sea horse is what gives it the name ÒhorseÓ, as its neck and head resemble that of an actual horse. First of all the neck itself is something most fish do not have. The Sea horse has the ability to look around and move its head without moving the rest of its body. The head is position at a right angle, much as a human or a horse head, but not a fish. On the head lays the sea horses two eyes, which as mentioned earlier are just like a chameleonÕs eyes, being that they are independent of each other and can each look in opposite directions. One eye can be looking for food as the other is watching out for a predator. The head extends into an elongated tube for a mouth, which at the end has tiny fused jaws and no teeth. This tube literally sucks small animals and crustaceans out of the waters like drinking through a straw, which it then passes through its odd digestive system. What makes the digestive system odd? It is that they have no stomach like many species. Sea horses suck in tons of food per day because of their poor digestive system. They rely on a series of intestines and an alimentary canal which only process a fraction of the food consumed into energy. This means that they are incapable of storing food, so they feed all day long, sometimes up to 10 hours per day. One sea horse can eat up to 3000 brine shrimp a day (Kalman 26).
The tail of a sea horse has a characteristic very important called ÒprehensileÓ. This tail is very strong and is used as an anchor for sea horses. They are able to use this tail to wrap around corals, plants and other objects to keep them in place. For much of the day, sea horses are very inactive, remaining tied down to one place for hours, constantly sucking in food and staying alert of predators.
The importance of the prehensile tail places a key role in the sea horses lifestyle, because unlike most fish, it is not a very good swimmer. The sea horseÕs have merely one small dorsal fin located on its back, which is used to propel it through the water. The sea horse does not use its tail as most fish do, which give others much power and speed. The sea horse has only this tiny fin that moves them, and it does so very slowly. Around its neck are two more fins called pectoral fins, which are mainly used for directional purposes. All three fins are all virtually transparent, and at first glace you would may not even notice them on the sea horse. There is also an anal fin that is located on the front, but does not contribute much if any at all to the movement. It has been stated by many researchers that sea horses move so slow that it is as if they calculate ever move with extreme diligence and caution. The dorsal fin on the back is of course the most active, and can flutter at a rate of 35 times per second, but they are still slow! Another interesting thing that they are able to do is move vertically like they are in an invisible elevator. To go up, or ascend, the sea horse can get away with almost only unrolling its tail. To descend or go down, it arches its neck, rolls in or curls up its tail. It has also been documented that sometimes they donÕt even use their fins to move around, but rather pull them selves up by their chin, elevating themselves from one height to another, such as grabbing onto coral, sea grass or other objects.
The sea horse with its limited swimming abilities in comparison with other fish, are very good at maneuvering. This is important in their survival as they rely more on camouflage to hide from predators than running away. The sea horse has another familiar chameleon trait, the ability to change colors to adapt to its surroundings. An adult sea horse has millions of tiny cells called chromatophores which are filled with colored chemicals. The sea horseÕs brain sends messages to these cells, causing one of more of them to open or close. When the sea horse is hiding in green seaweed, it can become dark green. If the sea horse moves near orange coral, however, the chromatophores that control orange open and the sea horseÕs body blends in with the orange coral. The shape of the cirri, or flaps that protrude from the sea horses body also help it blend in, making it looks like corals and other plants in the sea. A sea horse can even deceive a human, with its rigid bony body, and strong tail, its able to grab on the pieces of the ocean floor or coral and remain still, often looking just like a piece of sea grass or part of a coral. Sea horses also change color when mating or searching for a mate. (Kalman 20)
There are several differences between the male and female sea horse. The key difference and immediate identifying trait is the presence of the brood pouch which is only on males. This pouch extends from the lower abdomen of the sea horse to its tail, and at the top as a vertical opening for where the female deposits its eggs, and where the newborn exit. The anal fin on a female sea horse is also usually higher and more visible due to the lack of pouch extending from her body.
Mating, Reproduction, and Life Cycle
The sea horses have the most unusual way of reproduction and mating, as if you didnÕt think they were unusual enough. First of all, unlike many animals land or sea, they are monogamous, finding one partner for a season or several seasons, for which they continue to mate with over and over again. Some scientists even claim that they stay with the same partner for life, but others do not think this to be true. Even when they are not mating, the male and female will meet several times and as often as once a day to change color with each other, ÒdanceÓ with one another, or simply wrap there tails together much as humans will hold hands, this being called courtship. The breeding season for sea horses varies among location, water temperature, and species. It is also noted that many times sea horses breed in accordance to lunar patterns, specifically under a full moon. Mating season generally takes place in the spring and summer months, when it is warm enough to harbor the young.
When a male reaches sexual maturity, the formation of his brood pouch will be complete and he will be ready to mate. Smaller sea horse species are ready to mate around three months old, where larger species first mate around six to twelve months. The significance of this brood pouch and of the sea horse mating process is that the male actually gets pregnant, carries the eggs, and gives birth. It is the only species in the animal kingdom where the male gives birth completely and to the fullest. The male takes on the femaleÕs role in every aspect, it maintains the health, well-being, and rearing of the young. It performs the physical carriage and delivery as well. The pregnancy lasts between two and four weeks, where immediately after the male is ready again to mate. The actually mating process itself consists of the male and female intertwining their tails and performing what is referred to as a ÒdanceÓ where the female extends a tube called an ovipositor into the maleÕs brood pouch. She then secretes her eggs into the pouch, where the male fertilizes and then carries until birth. The female leaves immediately after, not sticking around for anything else, and the male usually finds a place to anchor himself where he will remain, moving only when necessary until birth is complete. The entire process is completely opposite from all other species, where the female assumes most of these tasks. The size of a particular brood varies on the different species, and can range from over 200 to a mere 8 per pregnancy.
During the pregnancy, the male becomes very motionless. He must find a good place to hide because he also looses a lot of control over his camouflage during the end of the pregnancy, where he will turn a very dark gray. The pouch, sometimes referred to as a super incubator, provides all the necessary nutrients and oxygen for the young, and disposes of all the waste that is deposited. Another important ability is that over the course of the pregnancy it slowly increases the level of salinity inside the pouch, so that when they are born, the young are able to withstand the high salt content of the ocean water. As the time of birth nears, the males pouch swells with the growing embryos, and becomes almost spherical in shape. To give birth, while anchoring itself, the male sea horse begins to rock its body back and forth, which then releases the babies out of the pouch into the water in groups. This process can take up to two full days to release all of the offspring, and after such the male will be completely exhausted, but will mate once again very shortly.
Once released into the ocean, the baby sea horses, called "fry", are very much like adult sea horses in terms of looks. They are however, virtually transparent upon release, which helps to protect them from predators during there infancy. When the sea horses are born, they are immediately off on their own, with only a small percentage surviving out of an entire brood, close to the likes of about five of every 1000. Many of the sea horses are born premature and not fully developed. Predators such as fish, penguins, crabs, sea turtles, and larger sea horses catch and eat baby and juvenile sea horses.
When a juvenile sea horse becomes a few weeks old it begins to develop colors, which first start on its head and then gradually spread across the entire body. Scientists also cannot tell the gender early on because of the single defining characteristic being the brood pouch, which is only on males and doesnÕt develop until around six to eight months. It generally takes on average up to one year for a sea horse to become an adult. At the end of the maturity, the sea horses body has now become very hard which helps in its protection. Unlike other fish, they do not live in groups but rather by themselves so they are not to easily attract predators. There are not many milestones after a sea horse reaches maturity, for pretty much all it does for the rest of its life is eat, avoid being eaten, and mate.
Species, Habitat & Enemies
There is some variation depending on the source of how many identified species there actually are. The number seems to range between 32 and 35, with most residing in the Western Atlantic Ocean and the Indo Pacific. The largest species is the Pacific Seahorse measured at around 300mm and the smallest known species at around 16mm is the Pygmy Seahorse (Restrepo 2004). The Pygmy sea horse was discovered in 2003, and it was once thought to be the offspring of another sea horse because of the tiny size. It was also hard to find by scientists because it hides deep in the corals. Scientists find sea horses hard to distinguish and often disagree on new species. Certain sea horses of the same type have very different looks and features.
Sea horses are found in temperate and tropical waters, ranging from the latitudes of 50 degrees north and south. They are also found in sub temperate waters and off the coasts of many different countries. There is however an abundance of species off the coast of Australian, as many as 11 different sea horse species can be found around this continent. Around North America and the United states there are four different species that can be sighted in the coastal waters with three residing in the Atlantic Ocean, and one in the Pacific. Sea horses live in shallow waters ranging from around 1 to 15 meters where they can receive sunlight and live in plants that photosynthesize, but certain species can be found at depths of around 60 meters. They live in corals, mangroves, estuaries, sea grass beds and other shallow water habitats that they can find. The male seahorseÕs general territory is usually only about one meter, where the female resides in up to 100 meters of area. The short distance traveled by the male is generally due to pregnancy, for when carrying, he does not travel nearly at all.
The sea horse generally does not have many predators in comparison to many fish. This is in fact due to its great camouflage ability and habitat it lives in. However, with camouflage being its only true force of protection, besides its hard exoskeleton, it is still the prey of some animals as it is not invincible. The sargassum fish dines on sea horses as if they were candy. It has a strong tough stomach and digests fish close to its own size, so sea horses are no disruption to their diet. Many shark feed on sea horses from time to time, but they diet on many different kinds of fish. Other animals that eat sea horses are skates, rays, sea-perch, tuna and some species of cod, which regularly seek out sea horses as food. Perhaps the predators who kill the most sea horses are humans, and it is not just for consumption, but for a variety of uses.
Every year thousands of tons of sea horses are caught and used for many things such as food, decoration, jewelry, key chains, and womenÕs purses just to name a few. They are used for an all most unlimited number of things. Countries such as China and India use them as a source of remedy or medicine. They are also an intriguing display to have as a pet in an aquarium which many people pay top dollar to have. If we as humans are not catching them, we are killing them in other ways. Habitat destruction is the leading cause of death for sea horses, and has placed many on the endangered species list. As mentioned, the main habitat is that of corals, mangroves and sea grass beds. As explained in the Enchanted Braid by Osha Gray Davidson, we have been destroying these habitats in nearly every aspect. If sea horses are not killed by means of dynamite or cyanide fishing, they are killed off by pollutants and sediment deposition. It has been estimated that some species have declined by up to 75% since 1990, while the overall seahorse population has declined somewhere in the neighborhood of 10% to 25%. This is all due to overexploitation and habitat destruction, and is just one of the many different animals and plants we are destroying in todayÕs age.
Sea Dragons
What I find to be possibly the most spectacular looking fish in the ocean is the Leafy or Weedy Sea dragon. It is the closest species to a sea horse and differs only in a few ways. The dorsal fin is placed farther back on its body, the head is set a more oblique angle, and it is larger in size, growing up to 18 inches long. What gives itÕs the name Leafy or Weedy are the spectacular outgrowths or appendages that resemble leafs and weeds. The sea dragonÕs perfect mimicry of a plant keeps it hidden from predators, with its leaf like appendages moving with the waters just as the surrounding seaweed or sea grass. The leafy sea dragon is also more vividly colored that the traditional sea horse. It still has the same kind of prehensile tail to anchor itself, and is a very weak swimmer as well. This species is very rare and is found mainly off the coast of Australia. It is an endangered species and is protected under Australian law. Besides the obvious differences by eye, and few physical characteristics it is almost the exact same as a sea horse.
Conclusion
Sea horses are a fascinating species in our oceans. I feel that they relate to the topic of this course in many ways, and are something that we may very well possibly see, as about three species live in the Gulf of Mexico and Atlantic Ocean waters surrounding the Bahamas. They are an important part of the coral reef ecosystem, and quite possibly another part in the braid that was referenced in the book Enchanted Braid. I feel that if we donÕt take steps to protect the environments that these creatures live in, we will soon loose them. The coastal waters, and the entire ocean for that fact have so much to give to nature, the shear sight alone of the coral reefs, sea grasses and animals that inhabit them are beautiful enough to never want to loose. However the sea horse falls on the list of spectacular things that we are eventually going to destroy if nothing is changed. I look forward to possibly seeing these magnificent fish as should others, but look hard I must for their camouflage is good enough to deceive even the human eye!
Works Cited Bellomy, Mildred D. Encyclopedia of Sea Horses. T.F.H. Publications, 1969. Kalman, Bobbie. The Life Cycle of a Sea Horse. Crabtree, 2004. Micheals, Patricia. "The Amazing Seahorse." Green Nature. 2005. 30 May 2008 . Miriam, Gross J. The Sea Dragon. Rosen, 2006. "Project Seahorse." May-June 2008. University of British Columbia. 28 May 2008 . Restrepo, Carlos. "Seahorses." Jan. 2004. 28 May 2008 . "Seahorse Organization." 17 Jan. 2007. 28 May 2008 . "Seahorse Reproduction." 2008. 29 May 2008 . "Seahorse Reproduction." 2008. 29 May 2008 . Spalding, Tim. "Seahorse and Seadragon Central." 2005. 2 Jan. 2008 . Spalding, Tim. "Seahorse and Seadragon Central." 2005. 2 Jan. 2008 . Stone, Lynn. Seahorses: Science Under the Sea. Vero Beach, FL: Rourke, 2003.
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