Seahorse

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Seahorses
Temporal range: Lower Miocene to present – 23–0  Ma
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Hippocampus.jpg
Hippocampus sp.
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Syngnathiformes
Family: Syngnathidae
Subfamily: Hippocampinae
Genus:Hippocampus
Rafinesque, 1810 [1] [2]
Type species
Hippocampus heptagonus
Rafinesque, 1810
Species

see Species.

Synonyms

Seahorse (also written sea-horse and sea horse) is the name given to 45 species of small marine fish in the genus Hippocampus. "Hippocampus" comes from the Ancient Greek hippokampos (ἱππόκαμποςhippókampos), itself from hippos (ἵπποςhíppos) meaning "horse" and kampos (κάμποςkámpos) meaning "sea monster". [3] [4] Having a head and neck suggestive of a horse, seahorses also feature segmented bony armour, an upright posture and a curled prehensile tail. [5]

Fish vertebrate animal that lives in water and (typically) has gills

Fish are gill-bearing aquatic craniate animals that lack limbs with digits. They form a sister group to the tunicates, together forming the olfactores. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Tetrapods emerged within lobe-finned fishes, so cladistically they are fish as well. However, traditionally fish are rendered paraphyletic by excluding the tetrapods. Because in this manner the term "fish" is defined negatively as a paraphyletic group, it is not considered a formal taxonomic grouping in systematic biology, unless it is used in the cladistic sense, including tetrapods. The traditional term pisces is considered a typological, but not a phylogenetic classification.

A genus is a taxonomic rank used in the biological classification of living and fossil organisms, as well as viruses, in biology. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclature, the genus name forms the first part of the binomial species name for each species within the genus.

Ancient Greek Version of the Greek language used from roughly the 9th century BCE to the 6th century CE

The Ancient Greek language includes the forms of Greek used in Ancient Greece and the ancient world from around the 9th century BCE to the 6th century CE. It is often roughly divided into the Archaic period, Classical period, and Hellenistic period. It is antedated in the second millennium BCE by Mycenaean Greek and succeeded by medieval Greek.

Contents

Habitat

Seahorses are mainly found in shallow tropical and temperate salt water throughout the world, from about 45°S to 45°N. [6] They live in sheltered areas such as seagrass beds, estuaries, coral reefs, and mangroves. Four species are found in Pacific waters from North America to South America. In the Atlantic, Hippocampus erectus ranges from Nova Scotia to Uruguay. H. zosterae , known as the dwarf seahorse, is found in the Bahamas.

Seagrass group of plants, with the same habit

Seagrasses are flowering plants (angiosperms) which grow in marine environments. There are 60 species of fully marine seagrasses which belong to four families, all in the order Alismatales. Seagrasses evolved from terrestrial plants which migrated back into the ocean about 75 to 100 million years ago.

Coral reef Outcrop of rock in the sea formed by the growth and deposit of stony coral skeletons

A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups.

North America Continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere

North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere; it is also considered by some to be a northern subcontinent of the Americas. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, and to the southeast by South America and the Caribbean Sea.

Colonies have been found in European waters such as the Thames Estuary. [7]

Thames Estuary estuary in which the River Thames meets the waters of the North Sea

The Thames Estuary is where the River Thames meets the waters of the North Sea, in the south-east of Great Britain.

Three species live in the Mediterranean Sea: H. guttulatus (the long-snouted seahorse), H. hippocampus (the short-snouted seahorse), and H. fuscus (the sea pony). These species form territories; males stay within 1 m2 (10 sq ft) of habitat, while females range over about one hundred times that.

Mediterranean Sea Sea connected to the Atlantic Ocean between Europe, Africa and Asia

The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Southern Europe and Anatolia, on the south by North Africa and on the east by the Levant. Although the sea is sometimes considered a part of the Atlantic Ocean, it is usually identified as a separate body of water. Geological evidence indicates that around 5.9 million years ago, the Mediterranean was cut off from the Atlantic and was partly or completely desiccated over a period of some 600,000 years, the Messinian salinity crisis, before being refilled by the Zanclean flood about 5.3 million years ago.

Description

Spiny seahorse H. histrix from East Timor holding on to soft coral with its prehensile tail Hippocampus hystrix (Spiny seahorse).jpg
Spiny seahorse H. histrix from East Timor holding on to soft coral with its prehensile tail

Seahorses range in size from 1.5 to 35.5 cm (0.6 to 14.0 in). [8] They are named for their equine appearance, with bent necks and long snouted heads and a distinctive trunk and tail. Although they are bony fish, they do not have scales, but rather thin skin stretched over a series of bony plates, which are arranged in rings throughout their bodies. Each species has a distinct number of rings. [9] The armor of bony plates also protects them against predators, and because of this outer skeleton, they no longer have ribs. [10] Seahorses swim upright, propelling themselves using the dorsal fin, another characteristic not shared by their close pipefish relatives, which swim horizontally. Razorfish are the only other fish that swim vertically. The pectoral fins, located on either side of the head behind their eyes, are used for steering. They lack the caudal fin typical of fishes. Their prehensile tail can only be unlocked in the most extreme conditions. They are adept at camouflage, and can grow and reabsorb spiny appendages depending on their habitat. [11]

Horse Domesticated four-footed mammal from the equine family

The horse is one of two extant subspecies of Equus ferus. It is an odd-toed ungulate mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature, Eohippus, into the large, single-toed animal of today. Humans began domesticating horses around 4000 BC, and their domestication is believed to have been widespread by 3000 BC. Horses in the subspecies caballus are domesticated, although some domesticated populations live in the wild as feral horses. These feral populations are not true wild horses, as this term is used to describe horses that have never been domesticated, such as the endangered Przewalski's horse, a separate subspecies, and the only remaining true wild horse. There is an extensive, specialized vocabulary used to describe equine-related concepts, covering everything from anatomy to life stages, size, colors, markings, breeds, locomotion, and behavior.

Dorsal fin The fin on the dorsal.

A dorsal fin is a fin located on the back of most marine and freshwater vertebrates such as fishes, cetaceans, and the (extinct) ichthyosaur. Most species have only one dorsal fin, but some have two or three.

Pipefish subfamily of fishes

Pipefishes or pipe-fishes (Syngnathinae) are a subfamily of small fishes, which, together with the seahorses and seadragons, form the family Syngnathidae.

Unusually among fish, a seahorse has a flexible, well-defined neck. It also sports a crown-like spine or horn on its head, termed a "coronet", which is distinct for each species. [12]

Seahorses swim very poorly, rapidly fluttering a dorsal fin and using pectoral fins to steer. The slowest-moving fish in the world is H. zosterae (the dwarf seahorse), with a top speed of about 5 ft (1.5 m) per hour. [13] Since they are poor swimmers, they are most likely to be found resting with their prehensile tail wound around a stationary object. They have long snouts, which they use to suck up food, and their eyes can move independently of each other like those of a chameleon. [14]

Evolution and fossil record

Anatomical evidence, supported by molecular, physical, and genetic evidence, demonstrates that seahorses are highly modified pipefish. The fossil record of seahorses, however, is very sparse. The best known and best studied fossils are specimens of Hippocampus guttulatus (though literature more commonly refers to them under the synonym of H. ramulosus), from the Marecchia River formation of Rimini Province, Italy, dating back to the Lower Pliocene, about 3 million years ago. The earliest known seahorse fossils are of two pipefish-like species, H. sarmaticus and H. slovenicus , from the coprolitic horizon of Tunjice Hills, a middle Miocene lagerstätte in Slovenia dating back about 13 million years. [15] Molecular dating finds that pipefish and seahorses diverged during the Late Oligocene. This has led to speculation that seahorses evolved in response to large areas of shallow water, newly created as the result of tectonic events. The shallow water would have allowed the expansion of seagrass habitats that selected for the camouflage offered by the seahorses' upright posture. [16] These tectonic changes occurred in the western Pacific Ocean, pointing to an origin there, with molecular data suggesting two later, separate invasions of the Atlantic Ocean. [17] In 2016, a study published in Nature found the seahorse genome to be the most rapidly evolving fish genome studied so far. [18]

Reproduction

Seahorse life-cycle Seahorse lifecycle.svg
Seahorse life-cycle

The male seahorse is equipped with a pouch on the ventral, or front-facing, side of the tail. When mating, the female seahorse deposits up to 1,500 eggs in the male's pouch. The male carries the eggs for 9 to 45 days until the seahorses emerge fully developed, but very small. The young are then released into the water, and the male often mates again within hours or days during the breeding season. [19]

Courtship

Before breeding, seahorses may court for several days. Scientists believe the courtship behavior synchronizes the animals' movements and reproductive states, so that the male can receive the eggs when the female is ready to deposit them. During this time, they may change color, swim side by side holding tails or grip the same strand of sea grass with their tails, and wheel around in unison in what is known as a "predawn dance". They eventually engage in a "true courtship dance" lasting about 8 hours, during which the male pumps water through the egg pouch on his trunk which expands and opens to display its emptiness. When the female’s eggs reach maturity, she and her mate let go of any anchors and drift upward snout-to-snout, out of the sea grass, often spiraling as they rise. They interact for about 6 minutes, reminiscent of courtship. The female then swims away until the next morning, and the male returns to sucking up food through his snout. [20] The female inserts her ovipositor into the male's brood pouch and deposits dozens to thousands of eggs. As the female releases her eggs, her body slims while his swells. Both animals then sink back into the sea grass and she swims away. [21]

Phases of courtship

Seahorses exhibit four phases of courtship that are indicated by clear behavioral changes and changes in the intensity of the courtship act. Phase 1, the initial courtship phase, typically takes place in the early morning one or two days before physical copulation. During this phase the potential mates brighten in colour, quiver, and display rapid side-to-side body vibrations. These displays are performed alternately by both the male and the female seahorse. The following phases, 2 through 4, happen sequentially on the day of copulation. Phase 2 is marked by the female pointing, a behaviour in which the female will raise her head to form an oblique angle with her body. In phase 3 males will also begin the same pointing behaviour in response to the female. Finally, the male and female will repeatedly rise upward together in a water column and end in mid-water copulation, in which the female will transfer her eggs directly into the male's brood pouch. [22]

Phase 1: Initial courtship

This initial courtship behaviour takes place about 30 minutes after dawn on each courtship day, until the day of copulation. During this phase the males and females will remain apart during the night, but after dawn they will come together in a side-by-side position, brighten, and engage in courtship behaviour for about 2 to 38 minutes. There is repeated reciprocal quivering. This starts when the male approaches the female, brightens and begins to quiver. The female will follow the male with her own display, in which she will also brighten and quiver about 5 seconds later. As the male quivers, he will rotate his body towards the female who will then rotate her body away. During phase 1 the tails of both seahorses are positioned within 1 cm of each other on the same hold-fast and both of their bodies are angled slightly outward from the point of attachment. However, the female will shift her tail attachment site, causing the pair to circle their common hold-fast. [22]

Phase 2: Pointing and pumping

This phase begins with the female beginning her pointing posture, by leaning her body towards the male, who will simultaneously lean away and quiver. This phase can last up to 54 minutes. Following phase 2 is a latency period (typically between 30 minutes and four hours), during which the seahorses display no courtship behaviour and females are not bright; males will usually display a pumping motion with their body. [22]

Phase 3: Pointing – pointing
Seahorses in Phase 2 of courtship Seahorse mating dance.JPG
Seahorses in Phase 2 of courtship

The third phase begins with the females brightening and assuming the pointing position. The males respond with their own brightening and pointing display. This phase ends with the male departing. It usually lasts nine minutes and can occur one to six times during courtship. [22]

Phase 4: Rising and copulation

The final courtship phase includes 5-8 bouts of courtship. Each bout of courtship begins with both the male and female anchored to the same plant about 3 cm apart; usually they are facing each other and are still bright in colour from the previous phase. During the first bout, following the facing behaviour, the seahorses will rise upward together anywhere from 2 to 13 cm in a water column. During the final rise the female will insert her ovipositor and transfer her eggs though an opening into the male's brood pouch. [22]

Fertilization

During fertilization in Hippocampus kuda the brood pouch was found to be open for only six seconds while egg deposition occurred. During this time seawater entered the pouch where the spermatozoa and eggs meet in a seawater milieu. This hyperosmotic environment facilitates sperm activation and motility. The fertilization is therefore regarded as being physiologically ‘external’ within a physically ‘internal’ environment after the closure of the pouch. [23] It is believed that this protected form of fertilization reduces sperm competition among males. Within the Syngnathidae (pipefishes and seahorses) protected fertilization has not been documented in the pipefishes but the lack of any distinct differences in the relation of testes size to body size suggests that pipefishes may also have evolved mechanisms for more efficient fertilization with reduced sperm competition. [24]

Gestation

Seahorses in Phase 4 of courtship Hippocampus haema mating.jpg
Seahorses in Phase 4 of courtship

The fertilized eggs are then embedded in the pouch wall and become surrounded by a spongy tissue. [25] The male supplies the eggs with prolactin, the same hormone responsible for milk production in pregnant mammals. The pouch provides oxygen, as well as a controlled environment incubator. Though the egg yolk contribute nourishment to the developing embryo, the male sea horses contribute additional nutrients such as energy-rich lipids and also calcium to allow them to build their skeletal system, by secreting them into the brood pouch that are absorbed by the embryos. Further they also offer immunological protection, osmoregulation, gas exchange and waste transport [26]

The eggs then hatch in the pouch, where the salinity of the water is regulated; this prepares the newborns for life in the sea. [20] [27] [28] Throughout gestation, which in most species requires two to four weeks, his mate visits him daily for “morning greetings”.

Birth

The number of young released by the male seahorse averages 100–1000 for most species, but may be as low as 5 for the smaller species, or as high as 2,500. When the fry are ready to be born, the male expels them with muscular contractions. He typically gives birth at night and is ready for the next batch of eggs by morning when his mate returns. Like almost all other fish species, seahorses do not nurture their young after birth. Infants are susceptible to predators or ocean currents which wash them away from feeding grounds or into temperatures too extreme for their delicate bodies. Less than 0.5% of infants survive to adulthood, explaining why litters are so large. These survival rates are actually fairly high compared to other fish, because of their protected gestation, making the process worth the great cost to the father. The eggs of most other fish are abandoned immediately after fertilization. [28]

Pregnant male seahorse at the New York Aquarium Tehotny morsky konik.jpg
Pregnant male seahorse at the New York Aquarium

Reproductive roles

Reproduction is energetically costly to the male. This brings into question why the sexual role reversal even takes place. In an environment where one partner incurs more energy costs than the other, Bateman's principle suggests that the lesser contributor takes the role of the aggressor. Male seahorses are more aggressive and sometimes “fight” for female attention. According to Amanda Vincent of Project Seahorse, only males tail-wrestle and snap their heads at each other. This discovery prompted further study of energy costs. To estimate the female’s direct contribution, researchers chemically analyzed the energy stored in each egg. To measure the burden on the males, oxygen consumption was used. By the end of incubation, the male consumed almost 33% more oxygen than before mating. The study concluded that the female's energy expenditure while generating eggs is twice that of males during incubation, confirming the standard hypothesis. [20]

Why the male seahorse (and other members of the Syngnathidae) carries the offspring through gestation is unknown, though some researchers believe it allows for shorter birthing intervals, in turn resulting in more offspring. [29] Given an unlimited number of ready and willing partners, males have the potential to produce 17% more offspring than females in a breeding season. Also, females have “time-outs” from the reproductive cycle 1.2 times longer than those of males. This seems to be based on mate choice, rather than physiology. When the female’s eggs are ready, she must lay them in a few hours or eject them into the water column. Making eggs is a huge cost to her physically, since they amount to about a third of her body weight. To protect against losing a clutch, the female demands a long courtship. The daily greetings help to cement the bond between the pair. [30]

Monogamy

Though seahorses are not known to mate for life, many species form pair bonds that last through at least the breeding season. Some species show a higher level of mate fidelity than others. [31] [32] However, many species readily switch mates when the opportunity arises. H. abdominalis and H. breviceps have been shown to breed in groups, showing no continuous mate preference. Many more species' mating habits have not been studied, so it is unknown how many species are actually monogamous, or how long those bonds actually last. [33]

Although monogamy within fish is not common, it does appear to exist for some. In this case, the mate-guarding hypothesis may be an explanation. This hypothesis states, “males remain with a single female because of ecological factors that make male parental care and protection of offspring especially advantageous.” [34] Because the rates of survival for newborn seahorses are so low, incubation is essential. Though not proven, males could have taken on this role because of the lengthy period the females require to produce their eggs. If males incubate while females prepare the next clutch (amounting to a third of body weight), they can reduce the interval between clutches.[ citation needed ]

Feeding habits

Seahorses rely on stealth to ambush small prey such as copepods. They use pivot feeding to catch the copepod, which involves rotating their snout at high speed and then sucking in the cope pod. Black Sea fauna Seahorse.JPG
Seahorses rely on stealth to ambush small prey such as copepods. They use pivot feeding to catch the copepod, which involves rotating their snout at high speed and then sucking in the cope pod.

Seahorses use their long snout to eat their food with ease. However, they are slow to consume their food and have extremely simple digestive systems that lack a stomach, so they must eat constantly to stay alive. [36] Seahorses are not very good swimmers, and for this reason they need to anchor themselves to seaweed, coral or anything else that will anchor the seahorse in place. They do this by using their prehensile tails to grasp their object of choice. [37] Seahorses feed on small crustaceans floating in the water or crawling on the bottom. With excellent camouflage and patience[ If they must eat constantly, then patience won't work. ], seahorses ambush prey that floats within striking range, merely sitting and waiting until the appearance of an optimal moment. [36] Mysid shrimp and other small crustaceans are favorites, but some seahorses have been observed eating other kinds of invertebrates and even larval fish. In a study of seahorses, the distinctive head morphology was found to give them a hydrodynamic advantage that creates minimal interference while approaching an evasive prey. Thus the seahorse can get very close to the copepods on which it preys. [35] [38] After successfully closing in on the prey without alerting it, the seahorse gives an upward thrust and rapidly rotates the head aided by large tendons that store and release elastic energy, to bring its long snout close to the prey. This step is crucial for prey capture, as oral suction only works at a close range. This two-phase prey capture mechanism is termed pivot-feeding. [38] [39] Seahorses have three distinctive feeding phases: preparatory, expansive, and recovery. During the preparatory phase, the seahorse slowly approaches the prey while in an upright position, after which it slowly flexes its head ventrally. In the expansive phase, the seahorse captures its prey by simultaneously elevating its head, expanding the buccal cavity, and sucking in the prey item. During the recovery phase, the jaws, head, and hyoid apparatus of the seahorse return to their original positions. [40]

The amount of available cover influences the seahorses feeding behaviour. For example, in wild areas with small amounts of vegetation, seahorses will sit and wait, but an environment with extensive vegetation will prompt the seahorse to inspect its environment, feeding while swimming rather than sitting and waiting. Conversely, in an aquarium setting with little vegetation, the seahorse will fully inspect its environment and makes no attempt to sit and wait. [41]

Seahorse hiding using camouflage Pygmy Seahorse - Hippocampus bargibanti.jpg
Seahorse hiding using camouflage
Seahorses (Hippocampus erectus) at the New England Aquarium Seahorse-aquarium.jpg
Seahorses ( Hippocampus erectus ) at the New England Aquarium

Threats of extinction

Because data is lacking on the sizes of the various seahorse populations, as well as other issues including how many seahorses are dying each year, how many are being born, and the number used for souvenirs, there is insufficient information to assess their risk of extinction, and the risk of losing more seahorses remains a concern. Some species, such as the Paradoxical Seahorse, H. paradoxus , [42] may already be extinct. Coral reefs and seagrass beds are deteriorating, reducing viable habitats for seahorses. [43] Additionally, bycatch in many areas causes high cumulative effects on seahorses, with an estimated 37 million individuals being removed annually over 21 countries. [44]

Aquaria

While many aquarium hobbyists keep them as pets, seahorses collected from the wild tend to fare poorly in home aquaria. Many eat only live foods such as brine shrimp and are prone to stress, which damages their immune systems and makes them susceptible to disease.[ citation needed ]

In recent years, however, captive breeding has become more popular. Such seahorses survive better in captivity, and are less likely to carry diseases. They eat frozen mysidacea (crustaceans) that are readily available from aquarium stores, [45] and do not experience the stress of moving out of the wild. Although captive-bred seahorses are more expensive, they take no toll on wild populations.[ citation needed ]

Seahorses should be kept in an aquarium with low flow and placid tank mates. They are slow feeders, so fast, aggressive feeders will leave them without food. [45] Seahorses can coexist with many species of shrimp and other bottom-feeding creatures. Gobies also make good tank-mates. Keepers are generally advised to avoid eels, tangs, triggerfish, squid, octopus, and sea anemones. [46]

Water quality is very important for the survival of seahorses in an aquarium. They are delicate species which should not be added to a new tank. The water parameters are recommended to be as follows although these fish may acclimatise to different water over time:

A water-quality problem will affect fish behaviour and can be shown by clamped fins, reduced feeding, erratic swimming, and gasping at the surface. [47] Seahorses swim up and down, as well as using the length of the aquarium. Therefore, the tanks should ideally be twice as deep as the length of the adult seahorse.[ citation needed ]

Animals sold as "freshwater seahorses" are usually the closely related pipefish, of which a few species live in the lower reaches of rivers. The supposed true "freshwater seahorse" called H. aimei is not a valid species, but a synonym sometimes used for Barbour's and hedgehog seahorses. The latter, which is often confused with the former, can be found in estuarine environments, but is not actually a freshwater fish. [48]

Use in Chinese medicine

Dried seahorse Seahorse Skeleton Macro 8 - edit.jpg
Dried seahorse
Seahorse and scorpion skewers as street food Seahorses scorpions skewer.jpg
Seahorse and scorpion skewers as street food

Seahorse populations are thought to be endangered as a result of overfishing and habitat destruction. Despite a lack of scientific studies or clinical trials, [49] [50] the consumption of seahorses is widespread in traditional Chinese medicine, primarily in connection with impotence, wheezing, nocturnal enuresis, and pain, as well as labor induction. [51] Up to 20 million seahorses may be caught each year to be sold for such uses. [52] Preferred species of seahorses include H. kellogii, H. histrix, H. kuda, H. trimaculatus, and H. mohnikei . [51] Seahorses are also consumed by the Indonesians, the central Filipinos, and many other ethnic groups.

Import and export of seahorses has been controlled under CITES since 15 May 2004. However, Indonesia, Japan, Norway, and South Korea have chosen to opt out of the trade rules set by CITES.

The problem may be exacerbated by the growth of pills and capsules as the preferred method of ingesting seahorses. Pills are cheaper and more available than traditional, individually tailored prescriptions of whole seahorses, but the contents are harder to track. Seahorses once had to be of a certain size and quality before they were accepted by TCM practitioners and consumers. Declining availability of the preferred large, pale, and smooth seahorses has been offset by the shift towards prepackaged preparations, which makes it possible for TCM merchants to sell previously unused, or otherwise undesirable juvenile, spiny, and dark-coloured animals. Today, almost a third of the seahorses sold in China are packaged, adding to the pressure on the species. [53] Dried seahorse retails from US$600 to $3000 per kilogram, with larger, paler, and smoother animals commanding the highest prices. In terms of value based on weight, seahorses retail for more than the price of silver and almost that of gold in Asia. [54]

Species

Based on the newest overall taxonomic review [55] of the genus Hippocampus with further new species and partial taxonomic review, [56] [57] [58] the number of recognized species in this genus is considered to be 45 (retrieved August 2018):

H. kuda, known as the "common seahorse" Hippocampus kuda (Estuary seahorse).jpg
H. kuda , known as the "common seahorse"
H. subelongatus, known as the "West Australian seahorse" Hippocampus elongatus.jpg
H. subelongatus , known as the "West Australian seahorse"
H. whitei, known as "White's seahorse" Hippocampus whitei 1.jpg
H. whitei , known as "White's seahorse"

Pygmy seahorses

Hippocampus satomiae (Satomi's pygmy seahorse) attached to coral HSatomiaeJohnSear.jpg
Hippocampus satomiae (Satomi's pygmy seahorse) attached to coral

Pygmy seahorses are those members of the genus that are less than 15 mm (0.6 in) tall and 17 mm (0.7 in) wide. Previously the term was applied exclusively to the species H. bargibanti but since 1997, discoveries have made this term obsolete. The species H. minotaur , H. denise , H. colemani , H. pontohi , H. severnsi , H. satomiae , H. waleananus , and H. japapigu have been described. Other species that are believed to be unclassified have also been reported in books, dive magazines and on the Internet. They can be distinguished from other species of seahorse by their 12 trunk rings, low number of tail rings (26–29), the location in which young are brooded in the trunk region of males and their extremely small size. [59] Molecular analysis (of ribosomal RNA) of 32 Hippocampus species found that H. bargibanti belongs in a separate clade from other members of the genus and therefore that the species diverged from the other species in the ancient past. [60]

Most pygmy seahorses are well camouflaged and live in close association with other organisms including colonial hydrozoans ( Lytocarpus and Antennellopsis ), coralline algae ( Halimeda ) sea fans ( Muricella , Annella , Acanthogorgia ). This combined with their small size accounts for why most species have only been noticed and classified since 2001. [59] [61]

Related Research Articles

Syngnathidae family of fishes

The Syngnathidae is a family of fish which includes seahorses, pipefishes, and seadragons. The name is derived from Greek, σύν (syn), meaning "together", and γνάθος (gnathos), meaning "jaw". This fused jaw trait is something the entire family has in common.

Big-belly seahorse species of fish

The big-belly seahorse or pot-bellied seahorse, Hippocampus abdominalis, 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.

<i>Hippocampus bargibanti</i> species of fish

Hippocampus bargibanti, also known as Bargibant's seahorse or the pygmy seahorse, is a seahorse of the family Syngnathidae found in the central Indo-Pacific area.

Hippocampus angustus, commonly known as the narrow-bellied seahorse, western Australian seahorse, or western spiny seahorse, is a species of marine fish of the family Syngnathidae. It is found in waters off of Australia, from Perth to Hervey Bay, and the southern portion of Papua New Guinea in the Torres Strait. It lives over soft-bottom substrates, adjacent to coral reefs, and on soft corals at depths of 3–63 metres (9.8–206.7 ft). It is expected to feed on small crustaceans, similar to other seahorses. This species is ovoviviparous, with males carrying eggs in a brood pouch before giving birth to live young. This type of seahorse is monogamous in its mating patterns. The males only fertilize one female’s eggs for the mating season because of the population distribution. While some seahorses can be polygamous because they are denser in population, this type of seahorse is more sparsely distributed and the cost of reproduction is high. Therefore, the risk to reproduce due to predatory and distributary factors limits this breed to one mate, often finding the same mate season after season.

Barbours seahorse species of fish

Barbour's seahorse is a species of fish of the family Syngnathidae.

Knobby seahorse species of fish

The knobby seahorse, also known as the short-headed seahorse or short-snouted seahorse, is a species of marine fish of the family Syngnathidae. It inhabits coastal waters in southwestern and southeastern Australia, from Gregory to Bremer Bay, and from Denial Bay to Newcastle.

Giraffe seahorse species of fish

The giraffe seahorse is a species of fish of the family Syngnathidae. It is found in coastal waters off of the south and east coasts of Africa, from South Africa to Tanzania, and possibly north to Kenya. It lives in estuarine seagrass beds, algae beds, and shallow reefs to depths of 45 metres (148 ft), where it can grow to lengths of 10 centimetres (3.9 in). It is expected to feed on small crustaceans, similar to other seahorses. This species is ovoviviparous, with males carrying eggs in a brood pouch before giving birth to live young. Individuals are sexually mature at around 6.5 centimetres (2.6 in). Major threats to this species could be habitat loss, through coastal development and pollution, and overexploitation through bycatch.

Crowned seahorse species of fish

Hippocampus coronatus, commonly known as the high-crowned seahorse or crowned seahorse, is a species of fish of the family Syngnathidae. It is endemic to the Pacific coastal waters of Japan, where it lives among Zostera seagrasses. It can grow to lengths of 10.8 centimetres (4.3 in), but is more commonly 6 centimetres (2.4 in). Individuals feed mainly on small crustaceans such as gammarid amphipods and copepods, although this can vary by size, with smaller individuals consuming copepods while larger individuals feed on amphipods and mysids. This species is ovoviviparous, with males brooding eggs in a brood pouch before giving birth to live young. Breeding season occurs from June to November, with females and males reaching sexual maturity at 6.9 centimetres (2.7 in) and 7.3 centimetres (2.9 in) respectively. Male brood size ranges from 12-46. The International trade in this species has been monitored through Appendix II of the CITES licensing system since 2004 and a minimum size of 10 centimetres (3.9 in) applies to traded specimens.

Denises pygmy seahorse species of fish

Hippocampus denise, also known as Denise's pygmy seahorse or the yellow pygmy seahorse, is a seahorse of the family Syngnathidae native to the western Pacific.

Hippocampus fisheri, commonly known as Fisher's seahorse, or the Hawaiian seahorse, is a species of fish of the family Syngnathidae. It is known from the Hawaiian Islands, although previous misidentifications indicated species occurrences in Australia and New Caledonia. Habitat preferences are unknown, but it has been found far away from shore and at depths greater than 100 metres (330 ft). Feeding habits are also unknown, but individuals are expected to feed on small crustaceans similar to other seahorses. They are also expected to be ovoviviparous, with males carrying eggs in a brood pouch before giving birth to live young. Individuals can grow to lengths of 8 centimetres (3.1 in). The specific name and the common name honour "Walter V. Fisher" of Stanford University.

Hedgehog seahorse species of fish

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.

Black-striped pipefish species of fish

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.

Short-snouted seahorse species of fish

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.

Hippocampinae subfamily of fishes

The Hippocampinae are a subfamily of small marine fishes in the family Syngnathidae. Depending on the classification system used, it comprises either seahorses and pygmy pipehorses, or only seahorses.

Broadnosed pipefish species of fish

The broadnosed 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.

<i>Acentronura</i> Acentronura es un género de peces de la familia Syngnathidae, en el orden de los Syngnathiformes.

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.

<i>Hippocampus pontohi</i> species of fish

Hippocampus pontohi, also known as Pontoh's pygmy seahorse or the weedy pygmy seahorse, is a seahorse of the family Syngnathidae native to the central Indo-pacific. Named after Hence Pontoh, the Indonesian dive guide from Bunaken (Manado) who first brought these pygmy seahorses to attention.

Hippocampus debelius, commonly known as the softcoral seahorse, is a species of marine fish of the family Syngnathidae. It is known from only two specimens collected from the Gulf of Suez in the Red Sea, at depths of 15–30 metres (49–98 ft). Individuals were found associated with soft corals. Although little is known of this species, it is expected to feed on crustaceans, similar to other seahorses. It is also expected to be ovoviviparous, with males carrying eggs in a brood pouch before giving birth to live young.

Pregnancy in fish

Pregnancy has been traditionally defined as the period during which developing embryos are incubated in the body after egg-sperm union. Although the term often refers to placental mammals, it has also been used in the titles of many international, peer-reviewed, scientific articles on fish, e.g. Consistent with this definition, there are several modes of reproduction in fish, providing different amounts of parental care. In ovoviviparity, there is internal fertilization and the young are born live but there is no placental connection or significant trophic (feeding) interaction; the mother's body maintains gas exchange but the unborn young are nourished by egg yolk. There are two types of viviparity in fish. In histotrophic viviparity, the zygotes develop in the female's oviducts, but she provides no direct nutrition; the embryos survive by eating her eggs or their unborn siblings. In hemotrophic viviparity, the zygotes are retained within the female and are provided with nutrients by her, often through some form of placenta.

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Further reading