The dwarf seahorse (Hippocampus zosterae) is a species of seahorse found in the subtidal aquatic beds of the Bahamas and parts of the United States. It is threatened by habitat loss. According to Guinness World Records, it is the slowest-moving fish, with a top speed of about 5 feet (1.5m) per hour.[4]
It is most often white in color but can range from tan, brown, yellow and green. In the wild, it often has small skin growths called cirri that resemble algae.
Description
Like other seahorses, the dwarf seahorse has a head angled at right angles to its body and swims upright using its dorsal fin to propel it and its pectoral fins to steer. It grows to an average length of 2 and 2.5cm (0.8 and 1.0in), with a maximum length of 5.0cm (2.0in).
The dwarf seahorse can live up to 2 years, but most commonly live around 1.[5]
It can be found in colors of beige, yellow, green, and black and may have white speckles, dark spots or protrusions and is well-camouflaged, the coloring usually matching the gorgonian on which it is typically found. It can change color.
It has been observed that this seahorse changes color for various reasons such as camouflage, reaction to an attack, due to an illness, or during mating.[6]
H. zosterae can be distinguished from other western Atlantic species such as H. reidi and H. erectus thanks to its number of fin rays. This species possesses from 10 to 13 dorsal and pectoral fin rays, and 9 to 10 trunk rings. Fully grown H. zosterae adults are usually smaller than these 2 other species.[5][6]
3D computed tomography (CT) scan of dwarf seahorse skeleton
They are restricted almost totally to seagrass microhabitats in shallow water, particularly in association with the seagrass Zostera. They are most common in bays during periods of high salinity, in coral reefs, floating vegetations, and between roots in mangrove swamps.[5][6]
They often live as a pair, sometimes alone. Males are rather sedentary and live in a small home range of about 1 square meter, whereas females roam on other males’ territory, around a hundred times larger than theirs.[6]
Diet
The dwarf seahorse is a lie-in-wait predator, feeding on living prey, including small crustaceans such as amphipods, small shrimps, other small invertebrates, and fish fry. Once their target is fixed, the hunter stretches towards it and sucks it through its snout. Food progresses through the digestive system rapidly, causing the nutrients to be ill-absorbed. This is the reason seahorses require large amounts of food to survive. These creatures can consume up to 3,000 brine-shrimps per day.[6]
Reproduction
Although, as every other seahorse species, it is the male that carries the offspring, they must still compete to access a mate. Males will tail wrestle and snap their heads toward each other and make clicking sounds during competition for access to a female. They display an eloquent courtship dance that begins each morning until copulation takes place.
Females initiate courtship behavior by entering the male's territory. Once she has entered his territory, the male initiates the actual behavior. In the first courtship phase the male and female change color and take turns quivering. This phase lasts for one to two mornings before copulation. The following phases of courtship behavior occur on the day of copulation. During the second phase the female displays a pointing posture with the head pointed upward. In return the male displays quivering and pumping behaviors in response to the females pointing. In the third phase the male assumes the pointing posture in response to the female's pointing. Finally, in the last phase of the courtship behavior, the pair repeatedly rise in the water column. The male pumps his tail toward his body and eventually the pair intertwine their tails. The female inserts her ovipositor and transfers the eggs into the male's brood pouch during the final rise in the water column. After eggs are deposited, the male rocks back and forth to settle the eggs in its pouch.[6][8]
Males carry between 3 and 55 soon-to-be younglings in their brood pouch for around 10 days before releasing them. Just born dwarf seahorses are 7 to 9mm long, while the diameter of the eggs in the pouch was around 1.3mm.[6]
Although females could technically mate with several males, seahorses form strict monogamous pair bonds for an entire season at least, a rare sight in fish species.[9] Female seahorses remain faithful during the pregnancy by returning to the male's territory each day for an early morning greeting. During the greeting, the pair change colors and dance together for about 6 minutes. Adult dwarf seahorses are iteroparous, meaning that they have multiple reproductive cycles in the course of their lifetime, in this case 2 per month.[5][6]
Dwarf seahorses remate within 4 to 20 hours after the young have been released from the brood pouch. This may occur throughout the breeding season. The breeding season starts in mid-February and ends in late October, depending on day length and water temperature.[6][10]
Development
Each larva grows and develops in its own tissue pocket which is surrounded by a network of blood vessels. The brood pouch is comparable to a “pseudoplacenta”: after the eggs are deposited, the walls of the pouch thicken and become more porous. The pouch provides protection, oxygen, nourishment, and waste removal.[6]
During their growth in the brood pouch, dorsal fin rays develop first, followed by anal fins. The mouth apparatus's development follows, but it is not functional until juveniles are released from the brood pouch.
Compared to an adult seahorse, offspring within the brood pouch have a rounded tail instead of tetrahedral tail, a wider and shorter snout, a dorsal fin that is closer to the tail, and pectoral fins that are closer to the back of the head.[6]
Season and water temperature disproportionately influences the sex ratio of developing seahorses.[6][11]
Once the offspring are released in the environment, they are completely independent of their parents. They are able to swim and feed immediately, but their weak swimming ability and high predation diminishes their rate of survival.[6]
The growth of H. zosterae is relatively rapid, especially during the summer season; both male and female are fully grown after 3 to 4 months. Sexual maturity of the male can be determined by the presence of its brood pouch.[6]
Predation
Dwarf seahorses’ predators include tunas, dorados, skates and rays, crabs, and water birds. Although the adults can protect themselves with their camouflage abilities, the young are not capable yet and are thus at a greater risk.
The seahorse's role in the ecosystems is vital, as they regulate populations of their marine preys, but also help their predators by becoming the prey themselves.[6]
In captivity
The dwarf seahorse only reaches up to 2 inches (51mm) in length and is not an aggressive feeder. Therefore, it is typically kept in small aquariums (5 to 10 US gallons (19 to 38L)). The dwarf seahorse can be fed brine shrimpnauplii, although it will also eat copepods and other shrimp larvae. Because of its short digestive tract, food must be available to them all day, making it a difficult species to keep. Unlike most marine fish, it will readily breed in the aquarium. The seahorse fry can be kept in the same aquarium as the adults in a dwarf seahorse dedicated tank. The dwarf seahorse has a gestation period of 10–14 days and can live up to over 2 years in captivity. The water temperature in the aquarium must place between 20 and 28°C, with a pH ranging around 8-8.5.[12] The tank water must be renewed regularly, once, or twice a day. The survival rate of dwarf seahorses in captivity is around 20%.[5]
Interest for humans
This species was particularly popular in the 1960s when mail order companies commonly sold them as the ‘perfect pets’.[5]
Due to its tiny size, the dwarf seahorse remains very popular in the aquarium market. Several Florida located fisheries’ core business lay around dwarf seahorses capture and trade.[6]
Chinese medicine is one of the biggest consumers of seahorses, as an estimated 20 million seahorses are used each year. The supposedly have cholesterol decrease virtues, preventing atherosclerosis.[6]
Humans have considered seahorses valuable and powerful for decades based on the magical myths surrounding these exotic creatures, and because males incubate eggs and give birth to their young.
Seahorses are important in education and research. The unique reproduction and mating system of seahorses, and the fact that they form monogamous pairs, a rare model of pair bonding in fish, makes them important for scientific study.
Conservation
Before 1970, this species was regarded as common. However, numbers have decreased over subsequent years, most likely due to a reduction in the extent of seagrass beds, pollution, oil spills, and ocean acidification.[5][13]
The IUCN Red List of Threatened Animals classified H.zosterae as vulnerable in 2000.[6][5] As of 2016, it is classified as least concern.[14][10] It is also listed in appendix II of CITES, as the whole other hippocampus species.[15]
Related Research Articles
A seahorse is any of 46 species of small marine fish in the genus Hippocampus. "Hippocampus" comes from the Ancient Greek hippókampos (ἱππόκαμπος), itself from híppos (ἵππος) meaning "horse" and kámpos (κάμπος) meaning "sea monster" or "sea animal". Having a head and neck suggestive of a horse, seahorses also feature segmented bony armour, an upright posture and a curled prehensile tail. Along with the pipefishes and seadragons they form the family Syngnathidae.
The Syngnathidae is a family of fish which includes seahorses, pipefishes, and seadragons. The name is derived from Ancient Greek: σύν, meaning "together", and γνάθος, meaning "jaw". The fused jaw is one of the traits that the entire family have in common.
Pipefishes or pipe-fishes (Syngnathinae) are a subfamily of small fishes, which, together with the seahorses and seadragons, form the family Syngnathidae.
The Banggai cardinalfish is a small tropical cardinalfish in the family Apogonidae. It is the only member of its genus. This attractive fish is popular in the aquarium trade. It is among the relatively few marine fish to have been bred regularly in captivity, but significant numbers are still captured in the wild and it is now an endangered species. The detrimental impact of humans on its environment and certain fatal diseases threaten this species' numbers significantly. Iridovirus diseases are known to be significant reason for fish mortality.
The big-belly seahorse or pot-bellied seahorse is one of the largest seahorse species in the world, with a length of up to 35 cm (14 in), and is the largest in Australia. Seahorses are members of the family Syngnathidae, and are teleost fishes. They are found in southeast Australia and New Zealand, and are listed on Appendix II of CITES.
Barbour's seahorse is a species of fish of the family Syngnathidae.
The Pacific seahorse, also known as the giant seahorse, is a species of fish in the family Syngnathidae. Their genus name (Hippocampus) is derived from the Greek word hippos, which means "horse" and campus, which means "sea monster." This species is the only seahorse species found in the eastern Pacific Ocean.
Hippocampus kuda is a species of seahorse, also known as the common seahorse, estuary seahorse, yellow seahorse or spotted seahorse. The common name sea pony has been used for populations formerly treated as the separate species Hippocampus fuscus, now a synonym of H. kuda.
The hedgehog seahorse is a species of fish of the family Syngnathidae. It inhabits coastal waters from India and Sri Lanka to Taiwan and northern Australia. It is threatened by overfishing, as both targeted catch and bycatch. This species is ovoviviparous, with males carrying eggs in a brood pouch before giving birth to live young.
The false-eye seahorse, or flatface seahorse is a species of marine fish of the family Syngnathidae. It is endemic to Australia, from Shark Bay to Broome, where it is found in intertidal rockpools, shallow algae and weedy or rubble reef habitats. It is expected to feed on harpacticoid, calanoid, and cyclopoid copepods, caridean and gammaridean shrimps, and mysids, similar to other seahorses. This species is ovoviviparous, with males brooding eggs in a brood pouch before giving birth to live young.
Hippocampus whitei, commonly known as White's seahorse, New Holland seahorse, or Sydney seahorse, is a species of marine fish of the family Syngnathidae. It is thought to be endemic to the Southwest Pacific, from Sydney, New South Wales and southern Queensland (Australia) to the Solomon Islands. It lives in shallow, inshore habitats, both natural and anthropogenic. This species is ovoviviparous, with males brooding eggs in a brood pouch before giving birth to live young.
The alligator pipefish or double-ended pipefish is a species of fish in the family Syngnathidae and is the only species in the monotypic genus Syngnathoides. It is found in shallow water in the tropical and subtropical Indo-Pacific, its range extending from East Africa to northern Australia. This fish lives in habitats of seagrass and seaweed, and hides by positioning itself vertically with its head down amidst the similar-coloured fronds of vegetation. The elongated, well-camouflaged body can reach 29 cm (11 in) in length. It feeds by sucking up its prey.
The black-striped pipefish is a species of fish in the family Syngnathidae. It is found in the eastern Atlantic from the southern Gulf of Biscay to Gibraltar, also in the Mediterranean and Black Seas. As the introduced species it is mentioned in the Caspian Sea and fresh waters of its basin.
The short-snouted seahorse is a species of seahorse in the family Syngnathidae. It is endemic to the Mediterranean Sea and parts of the North Atlantic, particularly around Italy and the Canary Islands. In 2007, colonies of the species were discovered in the River Thames around London and Southend-on-Sea.
The lined seahorse, northern seahorse or spotted seahorse, is a species of fish that belongs to the family Syngnathidae. H. erectus is a diurnal species with an approximate length of 15 cm and lifespan of one to four years. The H. erectus species can be found in myriad colors, from greys and blacks to reds, greens, and oranges. The lined seahorse lives in the western Atlantic Ocean as far north as Canada and as far south as the Caribbean, Mexico, and Venezuela. It swims in an erect position and uses its dorsal and pectoral fins for guidance while swimming.
The spiny seahorse, also referred to as the thorny seahorse, is a small marine fish in the family Syngnathidae, native to the Indo-Pacific area. It is classified as a Vulnerable species by the IUCN.
The broadnosed pipefish or deepnosed pipefish is a fish of the family Syngnathidae. It is native to the Eastern Atlantic from Vardø in Norway, Baltic Sea and the British Isles at north to Morocco at south. It is also found in the Mediterranean Sea, Black Sea and Sea of Azov. It is common in the coastal shallow waters, usually on reefs with seagrasses. This species is notable for its "broad" snout, which is as deep as its body.
The Gulf pipefish is a species of pipefish in the member of the taxonomic family Sygnathidae. Syngnathus scovelli is native to the region of south Florida, United States, the Atlantic Ocean, etc. S. scovelli is similar to Microphis brachyurus.
Acentronura is a genus of pygmy pipehorse native to the Indian and Pacific oceans. The name is derived from the Greek ακεντρονουρα, or a-kentron-oura, and refers to the lack of a sting on the tail.
The Patagonian seahorse is a species of marine fish of the family Syngnathidae. It inhabits coastal waters from northeastern Brazil to Chubut, Argentina. It generally is found at shallow depths attached to natural or artificial substrates. This species is ovoviviparous, with males brooding eggs in a brood pouch before giving birth to live young.
This page is based on this Wikipedia article Text is available under the CC BY-SA 4.0 license; additional terms may apply. Images, videos and audio are available under their respective licenses.
