Seahorses Everything You Ever Wanted to Know About This Species

Seahorses Everything You Ever Wanted to Know About This Species
Before we delve into all the fine detail – let us first take a quick look at seahorses, just enough to fire up your enthusiasm as you embark on this new and exciting hobby. The seahorse has for a long time been thought of as a mystical or even a mythological creature as they have been swimming in our Oceans for millions of years. Over more recent years there have been many scientific studies carried out, enhancing our understanding of seahorses. So much so, that it is now possible to keep some species in a home aquarium – providing you follow some sensible guidelines. It should be remembered that seahorses are a very delicate creature and do require pristine living conditions – at all times!

The first thing to understand is that a seahorse is actually a fish, despite their very different appearance. Seahorses swim in an upright position and have a head with a long snout, somewhat like a regular 4-legged land horse. They have similar fins to other fish, a dorsal fin, anal fin and pectoral fins, but no caudal fin – the tailfin. Instead of a caudal fin they have a long, square prehensile tail – unlike any other fish! This tail is used by the seahorse for hitching to a convenient plant or other anchorage whilst it scans with its independently moving eyes for prey. Because of the small dorsal fin, they can only swim slowly despite the dorsal fin beating many times per second. Steering is by their pectoral fins on the back of the head. They do not have scales like most fish, but thin skin stretched over bony plates giving them built in armour plating for protection. Seahorses also have a movable neck, unlike most other fish, which also resembles a regular land horse.

There are 54 currently known species of seahorses around the world, although as new species become known that number is likely to change. Their Latin species name, ‘Hippocampus’ comes from the Ancient Greek word, Hippos meaning horse and Kampos meaning Sea Monster. There is a list of the known species and where to find them in the World.

They live mainly in the shallow warm waters, although there are some cooler water species, mostly amongst the sea grass and macros where they change colour to blend in with their surroundings. Seahorses are plentiful around the Australian coast where you can find almost half of the currently known species.

Seahorses range in size from the smallest, the Hippocampus bargibanti or Pigmy Seahorse (left) measuring 1.5 cm (0.6 in) to the largest, the Hippocampus abdominalis or Big-Belly Seahorse (right) measuring 35.5cm (13.75in).

There are no freshwater seahorses anywhere in the World but some are found in estuaries and are able to survive for short periods in the brackish water created by incoming tides flooding up river. Recently there have been sightings of seahorses in cooler, European waters and can even be found in the Thames Estuary in the UK.

There are two species around the British Coastline, the Spiny Seahorse (H. guttulatus) and the Short Snouted Seahorse (H. hippocampus). Both British seahorses range from the Shetland Isles down the West coast of the UK, all around Ireland and along the South coast of England. There have also been a very small number of sightings on the East coast.

All seahorses are carnivores and feed mainly on crustaceans such as small shrimps and amphipods. Their feeding method is by stealth, they will lay in wait hitched to a plant or other convenient point and wait for their prey to come within range. It is then quickly sucked into the long snout; they have a small mouth opening but no teeth. The food is drawn up and crushed in the long thin snout, an audible ‘snick’ sound is caused by the trigger mechanism that creates the suction required to feed.

This action crushes and dismembers their prey to enable them to swallow it. The excess water that gets drawn in during this sucking and crushing process plus any inedible food residue is ejected through the gills which gives the appearance of a puff of smoke from the back of the head.

For many years, it was widely believed they had no stomach but more recent scientific studies involving dissection have proved this to be false. They have a very small rudimentary stomach and consequently a seahorse could not survive more than a day or two without food, unlike most other fish. In the wild they can easily consume several hundred live shrimps daily and in captivity they will spend all their waking hours searching for food.

Lifestyle – Another popular misconception is they mate for life; recent knowledge and understanding has shown they do not. In the wild the female will range much further afield than the male in her search for food and so does not remain in just one safe area. The male tends not to roam very far from his safe hitching post and prefers to wait until food swims close by to him, reminiscent perhaps of some human males! It is thought this behaviour makes it easier for the female to find her mate each morning for their ritual pairing and courtship dance. If the female knows exactly where to find her mate it significantly saves time in performing the regular morning meet and greet dance – without breaking into her feeding time. The male can also release pheromones into the water by flushing his pouch out. This action makes it easier for his mate, or indeed any other female, to find him, especially when he is ready to accept eggs. Despite all appearance of closeness, they are still quite happy to breed with different partners despite appearing to greet each other every morning with their little dance together. Some males have even been known to accept eggs from different females – at the same time! Of course in the aquarium they may well mate for life due to the limitation of any other suitable partner!

The seahorse is the only creature in the animal Kingdom where the male gives birth to live young. During the mating process the female deposits her eggs in the male’s brood pouch, via her ovipositor, where he fertilises them internally. He will then nurture and provide all their nutritional needs as they grow and develop. Depending on the species, it is on average around 14 days from passing the eggs to giving birth. The fry will usually number in several hundreds and birth rates as high as 1,000 and more have been recorded with some species. Once ejected from the male’s pouch the fry have to fend for themselves. In the wild it is estimated only about 1 in 1,000 survive, mainly due to being so easily predated upon, but in the aquarium the fry have a much higher chance of survival -providing they are properly cared for.

Sexing seahorses is easy as the male’s brood pouch alters the body shape when compared to the female. This is clearly shown in this photograph. Note how the male has a smoother, rounder abdominal line, whereas the female’s abdomen has an abrupt, more angular shape, before the tail.

Seahorse Colour Variations – When you start looking round for seahorses to buy you will probably come across many different colour variations. Seahorses, all breeds, can vary in colour from black through to white and and from yellow through to orange or even red.

Naturally you might be tempted to buy the pretty yellow or orange specimen you see at a breeders or at the shop – but you may well be disappointed when you get the seahorse home and in your aquarium! You could find your lovely yellow seahorse has turned brown or even black.

The reason being is that all seahorses are capable of changing colour for various reasons. Stress will often make them go dark, as does illness, but they will also try and match the colours in your aquarium.

You can, to some degree, encourage their display colours by adopting different colours in the aquarium. Avoid all dark colours and backgrounds, a medium blue background has been found to promote brighter colours in seahorses, bringing out the yellow pigment in particular.

If you are using plastic plants you can easily have a wide range of bright colours. They will also change colour frequently and rapidly when displaying to each other in a courtship ritual or even when warning off a rival! The point I am trying to make here is not to necessarily select your seahorses solely on colour. These photographs of the same seahorse, taken only moments apart demonstrate their ability to change colour clearly. This chameleon like ability to change colour is their natural camouflage in the wild, it is their only form of protection from hungry predators.

The ‘spikey’ growths you can see protruding from their bodies, are called cirri and form part of their disguise when amongst the sea grasses and macro algae in the wild. They can absorb (and regrow) cirri at any time and for no apparent reason, although in the wild it is less likely, being a useful part of their camouflage. In the aquarium they do not feel at the same risk and it is thought this may be one of the reasons they absorb it.

Self Defence – As a slow moving fish they do not have any means of defence and cannot accelerate away to avoid a predator. Their only chance of escaping predation is by blending in with their surroundings to help render them almost invisible. The following photographs were taken by accomplished diver and photographer, Jessica Riederer, in the waters of Bermuda where seahorse are also protected. They clearly demonstrate seahorses camouflaging abilities.

When resting, the head is tucked down close against the body, above, lower right, this is also part of the defence mechanism, it reduces his profile making him less visible to would be predators, in this case the photographer! It can also be an early indication of a potential health issue if they rest more than usual with their head tucked in, especially if they seem to have lost interest in food.

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