HIP! HIP! HIPPOCAMPUS: LET’S CELEBRATE SEAHORSES

Melinda Riger, doyenne of the deep and photographer to the stars (brittle stars, basket stars, starfish etc), undertook her 5000th dive a few days ago. She swims with sharks almost daily, and points her lens at the varied reef life she encounters along the way. Her gold prize for the dive turned out to be one of the smallest creatures she encountered: the seahorse. Hippocampus (Ancient Greek: Ἵππος, horse and Κάμπος, sea monster) is a unique fish, deriving from the pipefish, with more than 50 species known worldwide. I can feel a Rolling Harbour fact list coming on…

10 SEAHORSE FACTS TO DAZZLE YOUR FRIENDS WITH

• Only seahorses and razorfish swim upright / vertically all the time
• Their tails are prehensile and enable them to moor on coral, seagrass etc
• They have no scales, but skin stretched over bony plates arranged in rings
• The ‘coronet’ on a seahorse’s head is unique to the individual
• Seahorses are pathetic swimmers: the slowest have a top speed of 5′ per hour
• They feed by ambush, rotating the head and sucking prey in with their snout
• A seahorse’s eyes can move independently of each other, like a chameleon 
• The Bahamas is home to H. erectus and the dwarf seahorse H. zosterae
• Despite rumours, they don’t mate for life. Some may stay together for a season
• The smallest seahorse in the world – the pygmy – is a maximum of 15mm long

MAKING BABY SEAHORSES: A MOST UNUSUAL ARRANGEMENT

There’s no getting round it: seahorse courtship and reproduction is highly unusual. Here is a summary of how it goes (there’s a lot more to it, but life is short):

1. COURTING This may last for many days. They may change colour; they swim together; they entwine tails; they attach themselves to the same strand of coral or seagrass and turn slowly round it in unison (a so-called ‘pre-dawn’ dance). The final courtship dance may last several hours while the male & female prepare for the next stage.
2. EGG TRANSFER When the time is right the female transfers her eggs – hundreds of them – via her ovipositor  to the male, in the process of which they are fertilised. Handily, he has inflated a special egg pouch located on his abdomen. She then buggers off.
3. GESTATION The fertilised eggs grow inside the egg pouch of the male and develop into baby seahorses. This process may take from 10 days to a few weeks. During this time, the female will visit for a short ‘morning greeting’ and some intertwining action.
4. ‘BIRTH’ In due course the male ejects the baby seahorses from his pouch using muscular contractions. These may number from five to (get this!) 2,500 at a time; on average 100–1000. Job done. Then the tiny seahorse babies are on on their own…

THREATS TO SEAHORSES

The attrition rate of baby seahorses through predation is high (as for most fish species), but the prolific breeding rate reduces the effect on the overall populations.  As so often, there are human-related threats, not least habitat destruction, overfishing and pollution. There’s a less expected problem: the importance of seahorses in Chinese medicine.  Their presumed healing qualities are used to treat impotence, wheezing, enuresis, pain and to assist labour. For these purposes, some 20 million seahorses a year are caught and sold. Increasingly they are reduced to pill or capsule form. 

Seahorse values depend on the species, but weight for weight dried seahorses retail for *unbelieving face* more than the price of silver and almost that of gold in Asia, from US$600 to $3000 per kilogram. Ours not to reason why.

USELESS SEAHORSE FACTS

• Seahorse is an anagram of seashore
• The Seahorses were an English rock band, formed in 1996 by guitarist John  Squire following his departure from The Stone Roses. They split in 1999
• Devendra Banhart’s song ‘Seahorse’ contains these inspiring lyrics:
  I wanna be a little seahorse
  I wanna be a little seahorse
  A little seahorse
  I wanna be a little seahorse
  I wanna be a little seahorse
  I wanna be a little seahorse
  I wanna be a little seahorse
• I’m losing the will to live. Let’s meet Otis.

Introducing Otis, Melinda’s seahorse that lives under her dock

SEAHORSE MATING DANCE (4 MINS)

MALE SEAHORSE GIVING BIRTH

All photos: many thanks to Melinda Riger of Grand Bahama Scuba; sources, many and manifold including Wiki which is pretty good on this kind of thing! Fab seahorse gif by Alex Konahin