THE AMAZING WORLD OF SEAHORSES
Text and photos by Roger Grace
Seahorses are the stuff of which fantasies are made. Whole kids books are designed around seahorses, like the delightful âSign of the Seahorseâ by Graeme Base. My kids and I have spent many enraptured hours reading the gripping story verse and exploring the wonderful, rich paintings of Gropmund Groper and his henchmen, of the Seahorse Cafe, and Bert the soldier crab, Finneus and Pearl, other heroes and villains, and two barely noticeable shrimps.
An intriguing story of mystery, environmental stress, love, dastardly villains, and heroes. At the beginning of the story all the seahorses depart as a poisonous chemical cloud descends on the reef. They reappear at the end as the heroes find a new reef, free from the ravages of pollution and evil.
If you have seen a seahorse in real life, it is not surprising that they are the focus of so many fantasy stories, paintings, toys, and even company logos. The animal itself is so amazing that it almost defies belief.
Yet there are relatives of the seahorse that are even more unbelievable. Other members of the family Sygnathidae (sing – nath – id – ee) include the stunningly wierd leafy seadragon of southern Australia. It is so special that it is nationally protected through government legislation. In places it is a major drawcard for dive tourism. Dive tour operators can take groups of divers to spots where leafy seadragons are known, many of them individually, as they tend not to move very far.
Seahorses and their allies are actually fishes, with gills and fins and a swim-bladder. They have changed their shape through a long period of evolution and adaptation to a specialised existence. They have no teeth and no scales, but a series of bony plates under the skin provide considerable rigidity to the seahorse body.
Most members of the seahorse family have lost the tail fin, although there is the very small short-snouted pipefish which still has a tiny fin right on the tip of the almost thread-like tail. The pelvic fins have gone, and the anal fin occurs only on the female seahorse.
Propulsion is provided by the dorsal fin, which ripples on the back, and the pectoral fins, which flap furiously on the sides of the head. But even flat out a seahorse moves very slowly, relying on camouflage amongst the weed, rather than speed, for protection. The seahorse tends to swim upright when in the open, and may keep its tail curled, but more often trails it out at full length, ready to grab hold of any suitable perch it encounters.
The long-snouted pipefish is long and thin, and swims horizontally rather than upright like a seahorse. Although normally using its dorsal and pectoral fins for swimming, the long-snouted pipefish can put on a sudden burst of speed by snaking rapidly through the water and diving amongst the weed.
Most of the time seahorses and their relatives remain absolutely still, hiding amongst seaweed or sponges and sea-tulips, waiting for their prey of tiny shrimps, amphipods and copepods to come within striking distance. A special arrangement of bones in the jaw allows the seahorse to snap-open the tube-like mouth and quickly suck in the little animal that ventured too close. Seahorses also catch tiny amphipods crawling on the surface of the weed.
Most species have a prehensile tail, capable of curling around the stem of seaweed or sea-tulips for support. Pipefish generally donât hang on very tightly, in contrast to the seahorse which has a very strong grip, probably helping the animal to hold on in current-swept areas where food is in good supply. Being very poor swimmers it is important that they retain a good contact with something solid when currents are running.
Pipefishes are usually seen over dense beds of brown seaweed, their colour matching that of stands of Ecklonia or Carpophyllum. It is only their movement which gives them away, and they quickly snake into the weed as a snorkeller or diver approaches.
Seahorses are more rarely seen, as they spend very little time out in the open, preferring to remain motionless amongst the weed where they are very hard to find. I have also seen them in beds of giant sea-tulips in Otago, where they hang on to the stalks of these large seasquirts and pick-off tiny crustaceans drifting by in the currents. They are fascinating to watch while feeding. Their individually swivelling eyes are constantly on the move, scanning the passing waters for the tastiest looking gourmet crustaceans!
If you think seahorses look wierd, what do you think about their breeding!?
Seahorses pair for life, which is very unusual in fishes. They undergo complex daily ritual ceremonies to maintain the pair bond. But even more strange is the fact that the male seahorse becomes pregnant! The female transfers sticky egg strings into a pouch on the front of the âbellyâ of the male seahorse where they are fertilised. The eggs hatch in the pouch, and eventually up to a couple of hundred tiny thread-like miniature seahorses, each like a slightly crinkled strand of black cotton, are pumped and squeezed out of the maleâs pouch. The mini-seahorses are then on their own, their parents taking no further part in their care.
The weedy seadragon of south-east Australia carries its eggs externally, where they look like a bunch of crimson grapes, each about four millimetres in diameter, lying along the belly of the seadragon. The rich reddish browns, reds, and yellow speckles, even tinges of blue, of the weedy seadragon are supplemented by a few stalked red flaps of skin on the back and on the top of the head.
The leafy seadragon has far more extravagant flaps of skin, the crinkled body bedecked with flamboyant appendages which obscure the outline of the animal to help it blend in with its seaweed habitat. There are some wierd animals in this wonderful world of ours, but this must be one of the most wierd!
Seahorses and their relatives have for many years been used in a number of alternative medicines. The use of dried and powdered seahorse extracts has a particularly strong following in parts of S.E Asia, and they are even used as aphrodisiacs. They are sought in great numbers for these uses, and as aquarium fishes and dried curiosities. Consequently they are under pressure worldwide and are becoming scarce.
Attempts at aquaculture of seahorses are popping up in various places around the world. It is proving to be a difficult task, however, to farm seahorses. So far some of the ventures have merely resulted in the taking of large numbers of adult seahorses from the wild to use as breeding stock, with little success and little or no benefit to the dwindling wild stocks.
Mike Percy from the Western Underwater Research Team in Auckland has long been concerned about the plight of seahorses. He has established âSurvey Seahorse 2000â to foster interest in the welfare of seahorses in New Zealand and to promote a survey protocol for investigating their distribution and abundance around the country.
For more information on âSurvey Seahorse 2000â phone Mike Percy on (09) 827 7008, or check their website www.seahorse2000.org.nz