learn only 3 things about them ...
They are fishes and have bones inside as well as outside
The father gets 'pregnant'. They reproduce slowly.
are globally endangered due to overharvesting for the
traditional medicine trade.
everyone knows what a seahorse looks like. An endearing, unfish-like
fish, it truly captures the imagination.
Seahorses are more common on our shores that most people
might think. They are superbly camouflaged and thus often overlooked.
Some may be as large as 11cm, but there are tiny ones too.
What are seahorses? Seahorses are actually fishes! They
belong to Family Syngnathidae which
Features: To 30cm long, those seen about 5-12cm. The seahorse
doesn't have scales like most other fishes. It is encased in an inflexible
armour of overlapping bony plates that lie just beneath its skin.
Like other fishes, it also has an internal skeleton.
Adapted to calm waters with lots of hiding places, a seahorse cannot
swim fast. Most of the time it swims extremely slowly or remains stationary.
It relies on camouflage to hide from both predators and prey. It lacks
a tail fin and pelvic fins. It has a small dorsal fin and tiny pectoral
fins on its 'cheeks'. These fins are used to stabilise itself.
It uses its flexible, muscular tail to hang on to vegetation and other
supports. It can also change colours to match its surroundings. Some
species have flaps and projections out of their body to match the
vegetation around them.
What do they eat? It may be hard
to imagine of such seemingly harmless creatures, but seahorses are
voracious predators. They sit-and-wait in ambush to capture tiny animals
that drift or wander by. These shrimps, crabs and tiny crustaceans
are sucked up and swallowed whole. The jaws are tube-like ending in
a tiny toothless mouth. 'Syngnathus' means 'fused jaws' in Greek.
A seahorse needs to eat a lot continuously because its digestive system
is simple and it does not have a stomach. Even a baby seahorse can
eat thousands of tiny shrimp in a day! The seahorse has highly mobile
eyes that can move independently of one another to look out for predators
and prey without moving its body. Like other predators, seahorses
are often territorial, and seahorses in a seagrass meadow are often
well spaced apart.
Pregnant fathers: Seahorses reproduce
in a peculiar way. It is male that carries the eggs in his body and
thus becomes 'pregnant'. The female lays her eggs in his pouch using
a tube that looks very much like a penis. Inside his pouch, the eggs
are fertilized and become embedded into the body walls. The blood
vessels in the pouch provide the eggs with oxygen and nutrients. The
production of these nutrients is stimulated by prolactin, one of the
hormones that affect pregnancy in mammals.
Emerging from the eggs, the babies hatch as miniature seahorses and
may remain in the pouch for a while before the father goes into 'labour'
and ejects them out of the pouch.
Once they leave his pouch, he does not look after them. In fact, his
mate is often ready with another batch of eggs. So he is often constantly
'pregnant'! Some seahorses perform elaborate courtship dances, sometimes
changing colours as they move and holding tails as they swim together.
In the wild, some form mated pairs.
Human (ab)uses: Seahorses are
used in traditional Chinese medicine. Many species are also caught
for the live aquarium trade or dried and sold as cheap curious and
souvenirs. See below for some of the issues surrounding the harvesting
of wild seahorses.
Status and threats: Seahorses
are listed as CITES II (which means their international trade is monitored)
and are considered globally vulnerable. Hippocampus kuda is
listed among the threatened animals of Singapore.
Seahorses have few natural predators. Being virtually skin and bones,
they don't make particularly good eating. Humans are the main threat
to seahorses. Seahorse habitats are affected by reclamation, pollution
and activities that increase sedimentation. Over-collection is another
threat. Seahorses are naturally uncommon because they reproduce slowly
and seldom travel far from one spot. Those faithful to their partners
may take some time before taking on a new mate. Usually, in the wild
only a handful of babies survive from each batch of eggs. Being slow
swimmers without a free-swimming larval stage, seahorses don't spread
quickly to new places.
Being slow-moving and defenceless, seahorses are easily collected.
Like other fish and creatures harvested for the live aquarium trade,
most die before they can reach the retailers. Without professional
care, most die soon after they are sold, often from starvation as
their keepers do not provide the correct food in sufficient quantities.
Those that do survive are unlikely to breed successfully.
Efforts to farm seahorses have had limited success and often merely
involves the equally destructive collection of pregnant males.
Often seen in pairs.
Changi, May 05
Flexible tail used to hang onto
Changi, May 05
Mobile eyes can move while the body
remains still. Toothless jaws used like a straw.
Labrador, Jun 05
Tiny anal fin below the belly
Changi, May 05
Changi, May 05
A tiny seahorse less than 1cm long.
St. John's Island, Jun 07
on Singapore shores
Hippocampus recorded for Singapore
Wee Y.C. and Peter K. L. Ng. 1994. A First Look at Biodiversity
in red are those listed among the threatened
animals of Singapore from Davison, G.W. H. and P. K. L. Ng
and Ho Hua Chew, 2008. The Singapore Red Data Book: Threatened
plants and animals of Singapore.
comes (Tiger-tailed seahorse)
(Estuarine seahorse) (VU: Vulnerable)
- Kelvin K. P. Lim. 15 November 2013. New Singapore record of the seahorse, Japanese seahorse, Hippocampus mohnikei. Singapore Biodiversity Records 2013: 68-69.
- Lim, S.,
P. Ng, L. Tan, & W. Y. Chin, 1994. Rhythm of the Sea: The Life
and Times of Labrador Beach. Division of Biology, School of
Science, Nanyang Technological University & Department of Zoology,
the National University of Singapore. 160 pp.
G.W. H. and P. K. L. Ng and Ho Hua Chew, 2008. The Singapore
Red Data Book: Threatened plants and animals of Singapore.
Nature Society (Singapore). 285 pp.
- Allen, Gerry,
Fishes of South-East Asia: A Field Guide for Anglers and Divers.
Periplus Editions. 292 pp.
- Kuiter, Rudie
H. 2002. Guide
to Sea Fishes of Australia: A Comprehensive Reference for Divers
New Holland Publishers. 434pp.
Ewald and Robert Myers. 2001. Coral
Reef Fishes of the World
Periplus Editions. 400pp.
- Kuiter, Rudie
H., 2000 (English edition). Seahorses,
Pipefishes and their Relatives: A Comprehensive Guide to Syngnathiformes
TMC Publishing, UK. 240 pp.
- Sparks, John,
of the Sexes in the Animal World
BBC Worldwide, London. 224 pp.