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Biological Synopsis of the Long Snouted Seahorse, Hippocampus reidi Figure 1: Devaney, J (2011). A breeding pair of seahorses. [Photo]. By Thomas Wetherill, FdSc Marine Science Falmouth Marine School Contents University of Plymouth Page Number 1.1 Taxonomy 3 2.1 Identifying Features 4-5 3.1 Internal and External Anatomy 6-7 4.1 Natural Geographic Distribution 8 5.1 Life Cycle and Reproduction 9-10 6.1 Biotic and Abiotic Requirements 11-12 7.1 Nutritional Requirements 13-14 8.1 Life Support Requirements 15 9.1 Key Pathogen 16 10.1 Conservation Issues 17 11.1 Legislative Requirements 18 12.1 Extraordinary Issues 19 13.1 Bibliography 20-26 2|Page Falmouth Marine School University of Plymouth 1.1 Taxonomy Common Names: Longsnout seahorse, Brazilian seahorse, Slender Seahorse Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata Superclass: Osteichthyes Class: Actinopterygiio Subclass: Neopterygii Infraclass: Teleostei Superorder: Acanthopterygii Order: Syngnathiformes Suborder: Syngathoidei Family: Syngnathidae Subfamily: Hippocampinae Genus: Hippocampus Species: reidi Seahorses, sea dragons and pipefish are all part of the family Syngnathidae which means fused jaw. 3|Page Falmouth Marine School University of Plymouth 2.1 Identifying features Seahorses are part of the genus Hippocampus, derived from the Greek words for horse and sea monster. During the Oligocene period around twenty million years the seahorses are thought to have diverged from the other syngnathids when they developed their upright position (Casey, S.P et al. 2004). Due to environmental changes at the time the global amounts of sea grasses in coastal habitats was greatly increased which led to a mass migration into these new habitats. The syngnathids that dwelled here evolved the upright position which would have been favoured in the new habitat without affecting speed or the ability to remain camouflaged. The pipefish, however never entered this new habitat so there was no evolutionary need to evolve into an upright position meaning they maintained their horizontal body shape like the majority of fish found in the ocean. The longsnout seahorse, Hippocampus reidi, when fully matured can reach an adult height of between 4” to 7” /9.5-17.5cm measured from the top of the coronet to the tip of the extended tail (Koldeway, H et al. 2005; Lourie, S.A et al. 2004; Lourie, S.A et al. 1999). A massively exploited species referred to as the Brazilian or longsnout seahorse in the fishing trade. It is a key ingredient in many oriental medicines as well as being exported for ornamental purposes or live for aquaria (Koldeway, H et al. 2005). Their coronet on the top of the head (see Figure 4) is a low to medium height and is rounded rather than pointed but can be quite large in size and convoluted in appearance giving it the look of a crumpled up sheet of paper, they also hold their head at a right angle to their body. They usually do not have pronounced nose or eye spines (see Figure 4) but can have rounded tubercles instead but can just as often have none (see Figure 2) (Lourie, S.A et al. 1999). Like all seahorses, Hippocampus reidi have two eyes that can move independently of each other. Their colour varies greatly from brown, black, yellow, orange and red with white and dark spots dotted over the body, mainly the tail (Koldeway, H et al. 2005; Lourie, S.A et al. 1999). Their colour changes with stress, light and other changes to their environment, they are known to darken when removed from light and stressed and lighten when they are preparing to breed or are comfortable. 4|Page Falmouth Marine School University of Plymouth The species may be found with bands across the central body and the males are often a more mottled colour compared to the females. They also have other distinctive characteristics including broad, almost double cheek and eye spines; a long, thick snout of around 2cm; usually no skin appendages and a narrow body. Another good indicator of the species is the gestation period. Hippocampus reidi have a fourteen day gestation period at 24-28°C with a potential brood size of up to 1600. The eggs are generally oval in shape and have a faint orange colour tinge. Once born the juveniles tend to be around 8-11mm in length and research suggests that this initial juvenile stage may be pelagic rather than benthic which would help this species feed on their desired planktonic food (Koldeway, H et al. 2005). Figure 2: Devaney, J (2011). A longsnout seahorse. [Photo]. 5|Page Falmouth Marine School University of Plymouth 3.1 Internal and external anatomy External Anatomy Syngnathids are not like other teleosts (bony fish) as instead of having an internal bone structure they have a semi-flexible stiff body that is elongated and layered with bony plates and rings. Bony plates join together and create ridged rings or ‘dermal cirri’ on the body, tail and trunk, the number of these rings vary with each species of seahorse. These plates give the syngnathids a rigid body meaning that they can only move by rapidly beating their fins, this means they are quite slow in comparison to other fish but Figure 3: Driscoll, C (2004). Parts of the Body. [Photo]. have increased control over their movements allowing them to move with precision and also hover for extended periods of time in the same place. Seahorses are easily identifiable by the external features found on the head and body, features including the variations of the coronet, the length of the nose spine and Figure 4: Driscoll, C (2004). Parts of the Head. [Photo]. snout, the number of tail and body rings found and also the size, shape and number of pectoral and dorsal fins (see Figures 3 and 4). All species of seahorse have two eyes that are able to move independently of one another giving them the ability to look forward and backwards at the same time. The males and females tend to be slightly morphologically different as well (see Figure 5) with the Figure 5: Driscoll, C (2004). Sexual characteristics. [Photo]. males being slightly more slender, having fewer or smaller spines and having a brooding pouch on its’ abdomen. Colours can vary massively between the two genders as well with changes occurring when the body reacts to environmental changes, breeding, mating and brooding. Size can vary greatly between species, height is measured from the top of the snout to the tip of the fully extended tail and is measured using a metal straightening device not suitable for live specimens. 6|Page Falmouth Marine School University of Plymouth Circulatory system Seahorses are part of the bony fish class, Osteichtyes and have a two-part closed circulatory system. They have a single atrium and ventricle which make up the heart organ and pumps blood around the body with the outflow from the ventricle going to the gills. The liver of the seahorse plays an important role in the detoxification of the blood as well as the kidneys that help filter it and are positioned along the vertebral column. Digestive System Seahorses have a severely reduced stomach so absorb food as soon as they eat it meaning they have to eat most of the time to be able to survive. The intestines start at the snout where food enters, passes through the body and gut of the seahorse before exiting at the anal vent. Seahorses do not have a true pancreas but rather pancreatic tissue dispersed in the liver that helps produce bile to aid in digestion. This pancreatic tissue is termed ‘hepatopancreas’ in most fish. Respiratory System The gills make up the majority of the respiratory system of seahorses like with most other fish. The gills of a seahorse are known as tufted due to their irregular crumpled shape which appears to be attached to stems. Oxygen that is dissolved in the water is absorbed through the cell thin structure known as the gills when water is passed over the gill opening/ ‘the operculum’, and captured by the finger like primary and secondary lamellae which help give the gills a very large surface area and aid in the absorption of oxygen. The gills are made up of very delicate tissues so teleosts have 4 gill arches on either side of the head which have forward facing interlocking spines known as gill rakers that protect the gill tissue behind them. Because the gills are so cell thin the blood pumps very close to the surface allowing rapid gas exchange of oxygen into the body and waste gases like carbon dioxide out into the surrounding waters. 7|Page Falmouth Marine School University of Plymouth 4.1 Natural geographic distribution The long snout seahorse is found across a variety of waters that they are native too spanning across the Bahamas, Barbados, Belize, Bermuda, Brazil, Columbia, Cuba, Grenada, Haiti, Jamaica, Panama, United States (Florida, North Carolina), and Venezuela (IUCN. 2008; Kuiter, R.H. 2003; Lourie et al. 1999) (see Figure 6). They can be found at depths between 15-55m around coastal areas as their preferred habitats; sea grasses, gorgonian corals and sargassum are found in these regions with smaller specimens more common in shallower waters (Aquatic Community. 2008). Hippocampus reidi can be found in small groups of up to 4 individuals (Koldeway, H et al. 2005) Figure 6: IUCN (2008). Natural distribution of Hippocampus reidi. [Photo]. 8|Page Falmouth Marine School University of Plymouth 5.1 Life cycle and reproduction Male Pregnancy All members of the syngnathids all share common evolutionary traits: male pregnancy and monogamy. The female carries the eggs until courtship and mating occurs, in which time the eggs are transferred by the females ovipositor to specialised brooding pouches located on the abdomen of the male seahorse where they are fertilised (see Figure 5). The courtship dance and mating can last for several days. All post fertilisation care such as nourishment and osmoregulation is taken care of by the male which has evolved morphological traits to do this (Wilson, A.B. 2004). Monogamy During a mating cycle males are completely monogamous only accepting eggs from one female though they can switch partners between cycles. Some pair bonded seahorses have been observed to conduct in daily greetings (see Figure 1) that extend to courtship once the male has given birth (Lourie, S.A et al. 2004). Gestation and Birth Once H.reidi reach sexual maturity at around sixty days they are able to successfully breed and their growth rate slows down (da Hora, M.D.C & Joyeux, J.C. 2001). Recorded examples of mating shows that the actual process of egg transfer and fertilisation lasts around twenty five minutes and that like all species of the Syngnathid family, the young are born as miniature replicas of the adult and increase in size when they mature rather than change appearance (Rosa, I.L et al. 2007; Garrick-Maidment, N. 1998). Once males become pregnant they become less mobile and less social and conserve their energy and remain out of sight for protection, they have been observed to occasionally stop feeding meaning that some ‘treat’ foods like mysis should be provided to encourage feeding again. Once birth begins the pouch takes on a black or pinkish hue and the seahorse positions itself before the new borns are expelled by approximately one hundred for every tail beat against the body with the heights of the new born juveniles being around 8mm each (Rosa, I.L et al. 2007). H.reidi can give birth to 400-1600 juveniles per pregnancy cycle with the 9|Page Falmouth Marine School University of Plymouth gestation period being approximately fourteen days. The dispersal of the juveniles begins shortly after. Figure 7: Steene, R.C (2003). H.reidi. Female yellow, male dark red. [Photo]. 10 | P a g e Falmouth Marine School University of Plymouth 6.1 Biotic and abiotic requirements Generally the larger and more common species are kept due to their relative easiness to keep for the more experienced aquarists and that they have all have been found to be easily encouraged to breed in a healthy system. They must be given large tanks based on their size in order for them to be kept happy as well as making any sudden spikes of ammonia or others to be less immediately effective. Hippocampus reidi can be kept in relatively shallow tanks (60cm height or less) unlike most similarly sized seahorses but it should be at least wider then it is high to avoid additional stress in the future and also to allow for increased breeding, tanks with several paired seahorses are generally much more successful than a tank with few (Kuiter, R.H. 2003). Light plays an important role in the quality of the lives of the seahorses, especially with breeding pairs and should ideally come from the natural light provided by the sun. If artificial light is used the sunrise and sunset should be compensated for with a slow addition and subtraction of light intensity with a dimmer switch with the ratio of dark and light being 12 hours on and 12 hours off (Koldeway, H et al. 2005). This ensures that natural reactions to these light changes such as greetings, courting and mating still occur as close to normal as possible. Species that live at deeper depths are more sensitive to changes in light compared to shallower species but as H.reidi can be found as deep as 60 metres it is important to be very careful and slow with changes in light intensity throughout the day to ensure the continual wellbeing of the species (Kuiter, R.H. 2003). The base of the tank should be covered in live sand or be bare bottomed, no stones or pebbles to encourage excess algal growth. It is important to remember to add additional substrate such as rocks, artificial or live plants, netting or other potential grabbing items to allow the subjects to fasten their tails and rest, I have found that the best artificial fast holds are pieces of netting attached or weighed down at the bottom of the tank but using live rock works as well. In the wild H.reidi usually cling to small sponges or gorgonians that match their colouring to aid in their camouflage (Kuiter, R.H. 2003). The temperature of the tanks should be kept around 24°C but a little difference isn’t a problem as long as there are no rapid fluctuations 11 | P a g e Falmouth Marine School University of Plymouth in temperature as that could cause additional stress. At least a 75 watt heater should be used but any higher wattage should be fine. Water quality is important to maintain as many factors can affect it drastically. The water in the tank should be kept between 30-35‰ but no higher, as long as you try to keep the seahorses in as consistent a salinity as possible they should be fine. Important factors to be monitored in the tank are levels of ammonia, nitrite, nitrate and pH. Ammonia is very damaging to marine life so optimum levels would be zero but as long as levels remain lower than 0.25 parts per million (ppm) and there is regular siphoning of decomposing organic matter such as faeces or uneaten food the species should not be affected by this low level. Nitrite can be a serious problem and usually can spike after a large ammonia amount in the tank: it causes various health problems even in small amounts and typical symptoms include seahorses gasping for breath at the surface of the tank, seahorses remaining near water outlets continuously, rapid gill movements and the gills turning a tan or brown colour. It can cause nitrite poisoning which causes mass replication of methemoglobin which causes the blood to turn brown and limits ability to carry oxygen, the common name for this is ‘brown blood disease’ and to avoid this levels of nitrites should be kept below 0.25 ppm (Sharpe, S. Unknown). The effects of nitrates are far less understood and they are not thought to damage marine life until reaching around 100 ppm when they can start causing stress and affecting reproduction as well as stunting growth of fry and juveniles. Levels should be kept lower than 30 ppm to avoid any problems. For all of these issues the main preventer is simply frequent water tests and siphoning out additional organic matter but if spikes in these chemicals do become a problem then large daily water changes up to 60% over a period of a few days should sort the problem out quickly as well as reducing the level of feed, adding aeration to tanks and increasing salinity. 12 | P a g e Falmouth Marine School University of Plymouth 7.1 Nutritional requirements Roos et al, 2009 stated that Hippocampus reidi, like all Syngnathid fish, have a very morphologically different method of feeding compared to other fish. Whilst other fish feed by creating an anterior to posterior flow of water in their expandable head to create suction in a uni-directional direction, seahorses utilize their mouths to make rapid sucking movements close to the prey in order to feed. The maximum flow velocity is not found in the mouth channel, like with most teleosts, but rather in the narrow channel in the buccal cavity. They have specialised features such as elongated snouts and an immobile pectoral girdle which allows for this to occur (Leysen, H. 2011). They are visual feeders in that they have to see their prey before they hunt it rather than relying on scent or chemical indicators like some fish (Lee, H.R & O’Brien, K.M.D. 2011). Hippocampus reidi, when studied in the wild, have been found to be rather sedentary predators waiting for their prey to come to them most of the time rather than stalk them (Felicio, A.K.C. 2006). In captivity adults are normally fed 2-3 times a day over a period of about 6 hours. In nature H.reidi would feed on a variety of copepeds, rotifers and newly hatched brine shrimp (Leadsom, S. 2008). Chang, M.C (2000), stated that most of the strains of artemia found in the aquatic sense are deficient in Highly Unsaturated Fatty Acids (HUFAs) making them a poor long term food source for many fish species. In order to combat this a variety of foods should be used including mysid shrimp and artemia enriched with slurred fish meal or phytoplankton. All this excess HUFAs increases the fry’s’ and adults chance of survival and the increased nutrition also helps boosts immune responses to stressful factors affecting them or their environment. Juveniles When preparing the feed for H.reidi a high standard of hygiene should be maintained to prevent any bacteria or infiltrating algae to get into the seahorse system, this is extremely important to regulate for the seahorses continual growth and survival. Using a nutritious food that provides all the essential components of the seahorses diet increases the size of the offspring produced making it easier to keep 13 | P a g e Falmouth Marine School University of Plymouth juveniles as they can be fed larger foods like brine shrimp/ artemia nauplii as their first foods. It is crucial to ensure a variety in diet for the first few weeks of life as H.reidi normally remain so small in their juvenile stage that they often die of malnutrition due to not being able to take larger more nutritional foods (Leadsom, S. 2008). In the wild H.reidi have a vast amount of potential foods made up of a planktonic soup of lipid rich zooplankton. They do not often take any frozen foods so a diet of live feed is often required consisting of artemia, copepods and rotifers that are small enough to be fed on easily with rotifers being mainly used as they are small enough to be eaten by even the smallest seahorse After the first few weeks when the babies have reached juvenile size they can begin being fed a more varied diet consisting of mysid shrimp and different enriched artemia (Koldeway, H et al. 2005). 14 | P a g e Falmouth Marine School University of Plymouth 8.1 Life support requirements When setting up a suitable system for these fragile creatures there are many factors to take into account. Being such a slow moving and gentle creature seahorses would be better suited to being placed in seahorse specific tanks with no fast aggressive fish that could out compete them. Try and avoid adding any clams as they may close on a seahorse and species of crabs that could be detrimental to their health and survival in a tank. Adding fast holds in the tank is also an important step, artificial or live reed like plants similar to sea grasses would be best but these creatures will hold on to most anything. The more fast holds added though the less chance that they will attach to any of the filtration or heating devices within the system and risk damaging themselves. From personal experience I have found that this species can be successfully kept with a turnover rate of 3 times an hour with 50 litre tanks but it is recommended by other sources that 6 litres/ minute is required but as long as water quality is regularly monitored and you remember that ‘fish don’t pollute, feed and feeding pollute’ (Chen & Cho) and don’t overfeed them there should be no problem. These creatures come from tropical/ subtropical waters so are used to a warm temperature of between 20-28ºC so an average maintenance temperature of around 24ºC is ideal. As long as temperature is not changed rapidly but by a degree every few hours they should adapt quickly enough to avoid excess stress. Levels of nitrites, nitrates and ammonia should be kept as low as possible without regular water monitoring, maintenance and changes if anything spikes to reduce the risk of damage to the species. 15 | P a g e Falmouth Marine School University of Plymouth 9.1 Key pathogen Seahorses, like many cultured fish species, do not respond well to stress caused by high stock densities or environmental changes which make them more vulnerable to infection. In lab observations a number of infectious organisms affecting seahorse species were discovered including; cestodes, microsporidians, fungi, ciliates, trematodes and marine leaches (Koldeway, H & Martin-Smith, K.M. 2010). The main diseases that these species bring that are of a major concern for seahorses are vibriosis and mycobacteriosis (Koldeway, H. 2005). Vibriosis is easier to deal with as it can be treated with antibiotics though it affects various bacterial strains with varying levels of success and there have been limited testing on species due to regulatory and ethical implications. Vibriosis can come from live food such as artemia which has led to feed being treated with antibiotics before being fed to a species in order to reduce the chance of infection. Mycobacteriosis is not treatable and is considered a disease of special concern for seahorses (Koldeway, H. 2005). In aquatic systems another major concern for seahorses is gas entrapment issues or ‘gas bubble disease’ which causes problems in the brood pouch on the male, the emphysema on the tail and can cause over inflation of the swim bladder. Treatments used to help solve this issue include aspiration of air bubbles and/ or the use of antibiotics (Koldeway, H. 2005). Due to a seahorses unique anatomy there are many challenges related to their health care if there are any difficulties. The hard plated body makes injections difficult and the two part bronchial chambers make any attempts to clear or make biopsies to the gills difficult. This means that the best methods of managing disease is prevention by initialling quarantining any new species arriving in the aquatic facility before they are introduced to a system. Also maintaining a good in tank environment as well as maintaining a good diet for the species will help reduce any possible health problems that could occur. 16 | P a g e Falmouth Marine School University of Plymouth 10.1 Conservation issues Hippocampus reidi are one of two species of seahorse found around Brazil, a massively fishing orientated country, and due to lack of conservation effort they are heavily exploited. In a price declining market for fish, seahorses provide a highly economical and marketable product that can be exported worldwide for high cost and relatively small effort. The trade of seahorses has the potential to be a great alternative to fishing if managed sustainably however the declining populations of seahorses worldwide are still being massively exploited and mostly unchecked. Not many protocols have been initiated in the main Indo-Pacific countries responsible for the majority of exporting seahorses further decreasing global numbers of every species (Job, S.D et al. 2002). Conservation efforts have been made that work on the principles of discussion rather than outright banning. The main issues with the decline of the seahorses is the high demand for them in Asian countries with long legacies in the exploitation of these species. Ornamental and medical uses that date back thousands of years and are not fully understood make it difficult to make compromises for the use of seahorses. The apparent medical benefits of seahorse based ointments and powders have not been scientifically discovered so no alternative will be accepted as they can be claimed not to provide the same effects. The use of seahorses for ornaments and good luck charms are based mainly on beliefs and superstition so yet again no adequate substitute can be provided. In order to combat this there have been attempts to encourage the main consumers to try and preserve and sustain global populations allowing their continual exploitation without causing the extinction of the species which is nobody’s best interests. A village in the Philippines, Handumon, has been encouraged to craft and sell handicrafts to replace the profits that would have been made from seahorse exploitation and organisations such as Project Seahorse has aided in the set up of protective areas in these places and also helping make programs in these areas to teach local farmers in the conservation and preservation of seahorse species. When prevention of exploitation is not possible other attempts are used such as the use of special mesh cages that capture adult males but allow the young and newborns to escape thus allowing the chance for future reproduction (Becker, J. 2001). 17 | P a g e Falmouth Marine School University of Plymouth 11.1 Legislative requirements Seahorse populations are a cause for concern due to the vast market for various uses for them. All seahorses are listed on CITEs as vulnerable on the red list of endangered species in the International Union for the Conservation of Nature. This puts severe restrictions on the export and import of all seahorses, alive or dead which dramatically helps in seahorse conservation as global fishing will reduce as the available market decreases as well as helping to eliminate the wild seahorse trade in the aquarium trade. (IUCN, 2008; Olivotto, I et al. 2008). They are a popular ornamental species as well as being traded to be used in various traditional medicines, remedies and other product forms in various cultures around the world in high volumes (Zhang, D. 2010; Oliveira, T.P.R et al. 2007; Woods, C.M.C. 2007; McPherson, J.M & Vincent, A.C.J. 2004; Payne, M.F & Rippingale, R.J. 2000). They are targeted by divers that visit areas high in sea grasses and corals and are commonly poached along with sea cucumbers and a number of different gastropods (Salin, K.R et al. 2005). This overlong unsustainable exploitation of the seahorse species has caused vast gaps in our knowledge of their biology and ecology due to them becoming increasingly difficult to find (Woods, C.M.C. 2002). This is not helped by the gradual degradation and destruction of their habitats in coastal areas including coral reefs, sea grasses and mangroves (Olivotto, I et al. 2008). In 175 countries the export of seahorses has been limited to sustainable levels now in place to help protect them and also allow their numbers to replenish (Vincent, A.C.J et al. 2011). 18 | P a g e Falmouth Marine School University of Plymouth 12.1 Extraordinary issues In the trade of seahorses it is estimated that for every one million seahorses taken from the wild, less than 1000 survive for longer than six weeks (The Seahorse Trust. 2010). Though seahorses beat their fins around 50 times a minute they are actually very poor swimmers. 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