Monthly Archives: January 2012

The life cycle of a seahorse

COURTSHIP: Seahorses court for several days at a time. The courting ritual involves dancing, changing colour and entwining tails. Sometimes, more than one male seahorse will compete to win the affections of a female, or vice versa. Males can inflate their pouch by pumping water through it to display its emptiness. This is to entice the female to deposit her eggs in it.

Typical seahorse courting rituals involve dance routines which last hours. Image via weheartit.com

EGG TRANSFER: The female deposits her egg in the water in order to transfer to the males pouch. The male releases his sperm directly into seawater to fertilize the eggs. They are then embedded in the pouch wall and become surrounded by a spongy tissue. The number of eggs varies between species.

PREGNANCY: Although the male carries the baby, the initial conditions in the pouch are determined by the nutrients provided by the female, but when the eggs are in the pouch conditions are controlled by the male. He provides oxygen and nutrients through a network of capillaries. The embryos will remain in the pouch for two to six weeks, depending on species and temperature, as they develop into fully formed juveniles.

It is the male seahorse that becomes pregnant. Image via weheartit.com

BIRTH: When the male seahorse is ready to give birth he has muscular contractions to expel the young, which are known as fry, from the pouch.

YOUNG: Newborns measure between two and twelve millimetres, depending on species. The number of young produced ranges between 100 and 200 for most species, but can be as low as 5 for the smaller species, or more than 1,500 for larger species. The fry will often grasp floating or still objects, and even each other, with their tails. 

Baby seahorse, known as fry, are born fully functioning. Image via weheartit.com

JUVENILES: Newly released young undergo only small changes after emerging from the father. During growth some body proportions may change but they don’t experience major body changes. Some newborns emerge with a small fin which is lost over time.

ADULT: Mature male seahorses have the ability to become pregnant any time during the breeding season, which varies with species. This is thought to be influenced by environmental conditions such as water temperature.

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Pygmy Seahorse (Hippocampus Bargibanti)

All images via Wikimedia Commons

Seahorse found washed-up at Dorset nature reserve

An unusual discovery has been made at Purbeck’s Arne Nature Reserve. What was originally thought to be a small toy was found to be the remains of a real seahorse. Short-snouted and Spiny seahorse  are known to be inhabitants of Poole Harbour and the surrounding areas, but it isn’t often they appear on the shores of Shipstall Beach. A short-snouted seahorse, the less common of the two species relative to the British Isles, was spotted by a walker before being passed onto RSPB volunteer and wildlife enthusiast, Graham Tarrant.

The short-snouted seahorse had only minor damage to it's snout and it's skin had started to degrade. Image via Graham Tarrant

His son and fiancé, both marine biologists, were visiting for Christmas and suggested doing something with the seahorse rather than bury it. The inital plan to contact the Dorset Wildlife Trust, for which Graham is a member of, failed as they had closed for Christmas. It was then that Neil Garrick-Maidment of The Seahorse Trust was contacted.

“Polly, my future daughter-in-law emailed Neil to find out what we could do with it. There was a great debate whether to freeze it or pickle it”, Graham said. “I still remember from my A Level in Zoology that we put everything in Formalin to preserve it. Surgical spirit was the purest alcohol we could think of that we could easily get hold of, apart from vodka but that seemed a waste.”

Less than 1% of young seahorses make it to adulthood. Image via Graham Tarrant

Before it was stored in the alcohol, Graham took photographs of the creature to send to The Seahorse Trust, in advance. The images show it was a small, male seahorse just under 8cm. Although it was not pregnant at the time it is thought that it may have previously been.

Graham travelled, just after New Year, from Wareham to Ottery St Mary, where The Seahorse Trust is based. Putting it in the spirit, as opposed to freezing it, meant it is possible to still retrieve its DNA. Research can be carried out and DNA testing on enough samples could indicate some idea of population size for a certain area.

Although a rare occasion, this isn’t the first seahorse to be washed up in Dorset. In 2010 a number of spiny seahorse appeared on the shores of Hamworthy.

If you spot a seahorse washed ashore on any beach in the UK contact The Seahorse Trust on 01404 822373 or email them at info@theseahorsetrust.org