General Information
Distinct in its appearance and sexual preferences, peculiar in its way of reproduction, the hippocampus certainly impresses.
When flirting, when hiding and when in unusual environmental conditions, the hippocampus changes color.
A further confusing fact is that the hippocampus generates the male. Indeed, they are the only living organisms in the world where the male is pregnant with the embryos.
The earliest evidence of the existence of hippocampus on our planet dates back to 13,000,000 years ago.
Hippocampus (Equus Marinus)
The seahorse belongs to the Teleost fishes of the Sygnathidae family, the class of the bony fishes, despite all the unfortunate classifications of the past which placed them with the amphibians or even insects! Relative species are the seadragon (Phycodurus eques) and the pipe fish. Their size varies from 16 mm (Hippocampus denise) up to 35cm. The body is bilaterally compressed, does not have scales but rather large and tough dermal plates, which appear to divide it into rings and parallel lines. Each species has a certain number of rings. In addition their body appears swollen around the stomach becoming smaller around the tail. Each species has a unique number or rings and their body is inflated towards the stomach and tapering out towards the tail. The tail has a square cross-section and can be bend forward.
The head of the seahorse is almost perpendicular to its torso, ending in a tubular snout with a small mouth and eyes that move independently from each other like in chameleons. The head is decorated by a small “coronet” which is different for every seahorse, ensuring their uniqueness like in our finger prints.
The upper body distribution is similar to that of a horse, which explains the etymology of the first part of the word word “Hippo-campus” and hence the common name, seahorse.
The second part of the word “campus” denotes to the mythological beast “Kampi”. A black, female, winged monster placed in the underworld by Kronos, to guard the Cyclopes and the Ekatoxeires and that could be why the seahorse is commonly depicted as a sea monster. The etymology of the word comes from the verb “kampto” which means to bend, to turn, to arch and could refer to the twisting of their tail and/or the bending of their neck.
There are over 50 species of seahorses which mostly inhabit shallow, temperate and tropical waters worldwide. They prefer sheltered areas, in sea grass meadows, coral reefs or mangroves. Three species of seahorses inhabit the Mediterranean: Hippocampus hippocampus(the short-snouted seahorse), Hippocampus guttulatus(the long-snouted seahorse) and Hippocampus fuscuswho has migrated from the Red Sea. The first two species can be found in Greece.
Hippocampus hippocampus
(antiquorum, antiques, brevirostris, syngnathus hippocampus)
In Greece, the short-snouted seahorse can be found in the Gulph of Thermaikos, in Marathonas and in Kos according to fishbase.org data. The maximum length reaches 15 cm and the snout is shorter than 1/3 of the total head length. 17 dorsal fin rays, 14 pectoral fin rays. The coronet on the head is ridge-like and joined smoothly to nape of neck, or wedge-shaped (front narrow, back high and broad). Color varies from shades of brown to orange, purple or black and in some cases small, white dots can be visible. The white dots in this species do not merge with the vertical dermal stripes of the body as in the case of Hippocampus guttulatus. This is the species we photographed and is present in Stratoni.
Hippocampus guttulatus (Cuvier, 1829)
(rumulosus, longirostris, hippocampus microstephanus)
The long-snouted seahorse (Hippocampus guttulatus) can be found in Thessaloniki, in the Guplh of Evoia, in Kos and in the Strymonic Gulp, according to fishbase.org data. The maximum length reaches 18 cm, with a long snout. 19-20 dorsal fin rays, 16-18 pectoral fin rays. Distinctive characteristics of this species are the prominent rounded eye spines; often with a mane of thick skin fronds like small “thorns” on the neck and head. The coronet is small but distinct, with 5 rounded knobs or blunt points and is not joined smoothly to the neck. In front of the coronet and right above they eyes lies a horizontal plate in front of coronet as high as coronet itself, with a more or less prominent spine at its front edge, which likes the horn of Pegasus. The color varies from greenish yellow to reddish brown, sometimes with prominent white spots (often with a dark ring around them) which tend to coalesce into horizontal wavy lines or may be variously mottled or with pale ‘saddles’ across the dorsolateral surface. This is the species we photographed in Stratoni and in Crete.
Habits and habitats
Seahorses swim in a vertical position, a characteristic not shared by their close relatives, the pipe fish who swim in a horizontal position. Their dorsal fin pushes them forward by fast, palming motions (35 beats per second), while the pectoral fins behind the eyes maneuvers the fish left or right. They manage to move up and down the water column by adding or removing air in their swim bladders. Usually, they inhabit shallow waters, except in the winter time when they move to deeper waters, in rocky areas until 30m. Because of their morphology, they are not very good swimmers, moving slowly and spending most of the day anchored in sheltered areas amongst sea grasses or coral/rock reefs. Some species find shelter in brackish waters, but there are no fresh water seahorses discovered yet. Seahorses are always well covered and can instantaneously change their color and disappear completely from the visual field of their predators, mostly bigger fish, sea turtles or seabirds.
Feeding habits
Seahorses do not have a jaw or teeth. Their mouth is vestigial and so they have developed a specialized mechanism for obtaining food. Below their snout they have a trigger like organ which contracts suddenly, creating a pressure and thus sucking any prey with force. The eyes are also useful for spotting food as they move independently of one another, covering a broader visual field. Their menu mostly consists of small copepods οστρακόδερμα, plankton, small crustaceans and anything small enough to fit through its snout and be swallowed whole.
Married life
1. Prenuptial relations
For most seahorses breeding season lasts between April and October and is related to environmental temperature. During these months both males and females are in search of an appropriate mate. The male seems to make the first move and is more attractive to females if he selects if he possesses a plump brood pouch. He generally shows his interest but has to out win the remaining suitors courting the female. If he succeeds in passing through all the trials and win her over, then they openly court for a few days. Their color changes while they swim side by side holding their tails or on the same sea grass blade and merging their tails and fins in such a way as to become one while dancing their first prenuptial dance.
2. Courting
After the initial meeting comes the period of strengthening the relationship. At that time their prenuptial dance changes into a mating ritual which lasts approximately 8 hours. During this period the male fills and expands his brood pouch by pumping in water. When the female’s eggs are ripe enough, they simultaneously let go of whatever they were attached on, they “wear” their most spectacular colors and tangle their snouts while they rise above the sea grass, spinning in some cases. While they mate, the female inserts 200 -300 eggs in the brood pouch of the male. So, it is the male that holds the fertilized eggs in his body. The eggs were fertilized before their insertion into the brood pouch, when the male had released his sperm into the water.
3. Egg bearing
After mating the female’s body loses weight while the male who is bearing the eggs swells up. They both return to their underwater habitat but the female leaves, while he stays and is responsible for brooding the eggs while attached on seagrass or a rock, as slow as he has ever been. Inside his brood pouch the eggs are nurtured and are developing into embryos. The pouch offers them oxygen and appropriately controlled conditions for their hatching. Inside the pouch the eggs will become acclimatized to salt water since the male can regulate the salinity within the brood pouch. During the entire length of the pregnancy the female visits the male for approximately 6 minutes daily, reliving their mating period, when they were dancing freely for hours. They change their colors and slowly begin to spin around a seagrass or by holding their tails. She then departs and he returns to the monotonous sucking of his food, until the next morning when she returns again.
After the pregnancy which lasts between 2 and 4 weeks the male
begins to twist as if he was taken over by labor pains, and he then begins to expel the microscopically, well-formed seahorses, who are able to tend to themselves immediately.
Like in most fish species the ties with the family are cut immediately upon birth. By having maintained close relationships between the couple, the female is ready to repeat the procedure the next day and for as long as the mating period lasts by inserting her eggs in the male’s brood pouch. Only between 5-100 juveniles, on average, will make it to adulthood each time, a percentage quite high for fish species. This number is assured for two reasons: firstly because of the well maintained hatching conditions inside the brood pouch compared to the most fish species whose eggs hatch in open conditions and secondly by maintaining close ties the couple synchronizes closely, ensuring a successful fertilization of the eggs to a high degree.
4. Monogamy or Polygamy? That is the question…
Monogamy during the breeding season in seahorses ensures the survival of the species and for this reason scientists believed they maintained only one breeding partner. During our scientific literature review the results of experiments performed with many species of seahorses by mostly Australian researchers, revealed that albeit romantic this is not always the case. For instance, between 14 specimens of the Australian seahorse Hippocampus subelongatus studied in their natural habitat, 6 of them maintained extramarital relationships in two instances during the mating period. In a different article published in ETHNOS newspaper on the 1/2/2007 the researchers examined the sexual behavior of 90 individuals of 3 species and found out that they are polyamorous with homophlylic tendencies!
The seahorse in antiquity
The seahorse, was reasonably a popular object in the thematology of poets and artists during antiquity. Artists took care to include seahorses in their storytelling of feats and marine gods and goddesses, in written testimonials of holy dedications which have not survived until today, or depicted in elaborate sculptures, mosaics and coins of the Hellenistic era and Etruscan art. They portrayed a mythical dimension towards them which was mainly driven by their distinctive morphology. They are mostly pictured with a head, a sternum and two front horse legs, while from the waist down they had a forked fish tail. There are also examples with seahorses bearing wings, as in the treasure of Krisos from Lydia, in the famous Fontana di Trevi, 18thcentury in Rome.
Seahorses were also linked with the worship of Poseidon, God of the Sea. Homer, in the Iliad (N’17-31) writes that the copper legged and copper haired horses of Poseidon, flew high dragging the chariot of the God, without making it wet. In his epic poem “Argonautica”, Apollonios Rhodios also refers to the majestic horse coming out of the sea with his golden mane blowing in the wind (book 4. 1363-1369)
The Greek explorer and geographer of the 2ndcentury A.D., Pafsanias, mentioned in his work “Descripion of Greece”, the presence of a beast, amongst the sculptures decorating the temple of Poseidon in Korinth, whose sternum resembled that of a horse (2.1.7-9). In the winter of 373 B.C., a very strong earthquake completely destroyed ancient Eliki. Eratosthenes in the 3rdcentury B.C. states that the sanctuary of Poseidon was brought down and the copper statue of the God holding a seahorse in one hand, stood upright on the sea floor for 150 years after that, tearing the nets of fishermen. (This testimony was given by the ancient poet Stravon in his work “Geography”, 8.7.2)
Generally though, seahorses have been related with all marine gods and goddesses. In the entrance of the mosaic floor in the “house with the mosaics” which was built in 370 B.C. in Eretria, the Niriid Thetis, who was possible Achilles mother, is seen riding a seahorse and holding a shield and a spear. From the Renaissance and after, the seahorse is depicted in heraldic emblems of peoples and countries with a maritime history.
Prehistory
The oldest account of the seahorses’ presence on our planet reaches 13.000.000 years ago. Until today, seahorse fossils found in Rimini, Italy are dated to 3.000.000 years ago. The oldest account comes from Slovenia, where two species that looked more like pipe fish, are thought to be the predecessors of the seahorses, Hippocampus sarmaticusand Hippocampus slovenicushave been dated to 13.000.000 years ago.
The smallest seahorse in the world.
In 2003, scientists from Vancouver Canada, discovered the smallest seahorse in the world and realized that it was not a juvenile of a known species, but a completely new species. The tiny seahorse was approximately 16 mm big, even smaller than a nail, and lives in the tropical waters of the Pacific Ocean, according to Sarah Lourie, biologist from McGill University and head of the research project. This new species of seahorse is very skilled at camouflage and this is probably the reason it has survived the over-exploitation faced by other species of seahorse.
The seahorse as a protected species
The main threat faced by seahorses is, unfortunately, mainly from unintentional fishing. Because they prefer to inhabit areas close to the shore and in shallow depths, they accidentally get caught in the fishing nets and are then forwarded alive to be sold for the aquarium trade or dried to be sold in the curio trade for souvenirs to tourists visiting coastal areas.
A large proportion is used as an ingredient in traditional remedies. Already from Roman times, Plinee the eldest who was a Roman physicist, philosopher and historian, mentioned in his work “The physics of history” the therapeutic qualities of seahorses. Today, it is estimated that 20 million seahorses are sold in the market of traditional Chinese medicine. They are considered to drastically contribute to the balanced function of the circulatory system and aid in curing problems with erectile dysfunction, sterility, asthma, renal failure, some skin conditions and are said to bring down cholesterol. They are also used as a general tonic, a potent aphrodisiac and also in aiding with labor.
Some seahorses were listed as Vulnerable (VU) in the International Union for the Conservation of Nature (IUCN) Red List of Threatened Species in 1996. From 2003 until today they have been listed as Data Deficient (DD), however recently the two Mediterranean species have been re-evaluated and placed under the near threatened category during a Mediterranean assessment. They are also listed under Appendix II of CITES, Appendix II of the Bern Convention, Appendix II of the Barcelona Convention and in Appendix B of the EU Commission Regulation No 1320/2014. The above four European and International Treaties have been signed by Greece, who is obliged to protect this species. Three Hellenic ministries, the Ministry for Agricultural Development and Food, the Ministry of Shipping and the Islands along with the Ministry of Energy and the Environment are responsible for enforcing the aforementioned treaties while ensuring seahorses are not fished while legally enforcing their protection. Seahorses are also listed in the Convention for the Protection of the Marine Environment of the North East Atlantic (OSPAR) which is not signed by Greece.