Of Pipes and Steeds in Sea
This Creature Feature aims to introduce you to an inhabitant of the Indian Ocean. Many of these creatures live not far offshore from some of ourfavourite beachside destinations. Let’s find out a little more about them.
May 2015 found me underwater in the Palk Bay documenting the incredible life forms tucked between the fronds of sea grasses that form vast underwater meadows. The scientist I was assisting wanted photographs of everything I could find, but was specifically interested in the number of seahorses I encountered. In 2001, the Government of India imposed a ban on seahorse collection. And yet, on 16 dives over four days, I observed and photographed only five individuals. In the beautifully bizarre underwater world off the Indian coastline,seahorses, pipe fish and their relatives are among the most obscure, outlandish and “un fish-like” residents of the Indian Ocean.
Seahorses have a head and flexible neck somewhat resembling a horse. With an upright posture, a long, tube-like snout ending in a small mouth, and a strong prehensile tail that grabs onto almost anything for support, it is difficult to consider a seahorse as a kind of fish. And yet, the family of Syngn athidae,which includes seahorses, pipe fish and sea dragons, are in fact a family of fish – one that displays some of the most fascinating adaptations and camouflage in the marine world.
Seahorses, in the sub-family Hippocampinae, are a prized sighting for divers and snorkelers. The smallest of the seahorses, the pygmy seahorses, often spend their entire adult lives on one Gorgonian fan coral. They are between 15 and 25 millimeters long from snout to tail and are found east of India, from Indonesia all the way to Australia and Japan. The seahorses in the Indian Ocean are generally larger in size. They prefer calm, sheltered waters and tend to inhabit shallow sea grass beds, estuaries, mangrove edges and near shore coral reefs. Although they are bony fish, they lack scales, and are instead covered in a thin skin stretched over bony, armour-like plates. Seahorses lack a caudal fin, or tail fin, typical of most other fish. And so, in order to swim they rapidly flutter their dorsal fin while using pectoral fins to steer themselves through the water. This is usually done in an awkward, upright position, and needless to say, they are terrible swimmers.
Unlike their seahorse cousins, pipe fish in the subfamily Syngnathinae lack the equine head and neck. They are slender and snake-like in body and tail, and the majority of pipe fish have some form of tail fin that makes them somewhat better swimmers. Pipe fish range from a few centimeters long to over 60 centimeters in length. They are also armored with rings and bony plates instead of scales. Their name is derived from the small, toothless, upward facing mouth located at the end of along tube.
Regardless of swimming ability, seahorses and pipe fish tend to remain close to or constantly in contact with the substrate.Many seahorses wrap their tails around sea grass fronds, algae, weeds, discarded ropes, etc and sit motionless in beautiful camouflage. Water currents flowing across the seabed bring mysid shrimp, cope pods and crustacean larvae past the waiting animal. Others, including most pipe fish, that actively feed on invertebrates off the seabed, swim in a stop-start manner that allows them to sneak up undetected to within striking distance of their prey. These fish then bring their mouths towards their prey with an upward pivoting of the neck joint. In the final moment of the lightning fast, 5-millisecond capture, the prey is sucked out of the water with a distinctive click.
Beyond bizarre appearances and awkward swimming techniques, seahorses and pipe fish are known for their extraordinary courtship and reproductive habits. Many species of seahorse and pipe fish pair bond for the entire breeding season, showing little interest in other individuals. Some species, however, change mates if the opportunity arises and a few of them breed in groups without displaying any mate preferences. Among individuals that do pair bond, courtship may extend for several days and is a complicated display that is thought to synchronize the reproductive states of the two animals. In comparison to their generally secretive lifestyles, the courtship dances of seahorses and pipe fish involve conspicuous shaking and whirling in unison with a lot of tail holding! And after all of this is done, the male gets pregnant!
That’s right – males in many of the species have brood pouches. Instead of the males providing the females with sperm, the females deposit their eggs into the pouch on the male. The male releases sperm into the brood pouch to fertilize the eggs and the pouch is sealed to form an incubator. In some species, the eggs become embedded in a spongy tissue within the pouch and the males actually provide calcium and lipids to the developing embryo. Most young seahorses and pipe fish are born as free-swimming miniatures that assume the behavior of their parents immediately.
Ghost pipe fish of the family Sole nostomidaeare close relatives to the pipe fish and sea horses of Syngnathidae. They differ in body structure with the presence of large,well-developed fins including a ventral and second dorsal fin.And unlike the seahorses and pipe fish, it is the larger female ghost pipe fish that brood the eggs in a pouch formed by their large ventral fins.
The similar morphology between ghost pipe fish, pipe fish and seahorses has led to much confusion in the world of taxonomy.But for divers on a reef, encountering a ghost pipe fish – usually exceptionally well camouflaged against a fan coral or a piece of algae on the sand – is a rare and memorable thing.
In my experience of taking people diving, seahorses, pipe fish and ghost pipe fish always elicit excitement in divers fortunate enough to see them. After all, they are exceptional in their digression from every other fish in the sea. But they are also fast disappearing. Despite the ban on seahorse collection, huge shipments of these animals are smuggled out to Southeast Asia every year for their supposed aphrodisiac qualities in traditional Chinese medicine. Pipe fish are becoming increasingly popular aquarium fish. And beyond this sort of targeted collection the increase in trawling is wiping out the habitats that these fish need. As numbers dwindle, the rare becomes even rarer, and an underwater encounter with these animals in the wild is one to be dearly cherished.
This article first appeared in the March-May 2016 issue of Saevus magazine.