Everything You Want to Know About Seahorses
Everything You Want to Know About Seahorses
They are considerably smaller, far more cryptic, and in many cases considerably less colorful than many of the creatures that so often command our attention. But by the time we are school-age kids, the fish we commonly know as seahorses capture our admiring hearts.
Types of bony fish, seahorses are members of the family Syngnathidae, a name derived from the Greek syn meaning together, or fused, and gnathus meaning jaw. Including pipefish ,pipehorses and sea dragons in addition to seahorses, the family includes approximately 215 species described in 52 genera. But with the taxonomy of this family is undergoing a revision these numbers are likely to change in the coming years.
Fossil records for sygnathids (seahorses and their close relatives) date back to somewhere between 66 million and 38 million years ago. Most of the currently living family members occur in saltwater ecosystems, but a few species inhabit brackish and fresh water environs. Although there are some notable exceptions, the majority of seahorses and their kin live in relatively shallow sectors of warm temperate to tropical seas.
Worldwide there are at least 35, and perhaps as many as 50, species of seahorses. All are described in the genus Hippocampus, a word derived from the Greek words hippos meaning horse and kampus meaning sea monster. Given the equine profile of seahorses it’s easy to understand the reference to horses, but with regard to sea monsters, I’ll leave that up to your ability to stretch your imagination.
While seahorses and all other members of their family are types of bony fish, their skin lacks the scales found on many other species. However, seahorses are equipped with a series of rigid, bony plates that are arranged in rings located throughout the body. Various species have a distinct number of rings. That said, for most sport divers it is their horse-like profile and upright swimming position that allows us to so quickly identify a fish as some type of seahorse. Pipefish and sea dragons typically have a horizontal orientation when they swim.
Another noteworthy characteristic is the coronet, a bony projection located on the top of a seahorse’s head. Occurring in a wide variety of shapes and sizes, the coronet of an individual seahorse is as unique to these fish as thumbprints are to our species. While ichthyologists are not absolutely certain about the purpose of the coronet, many believe the coronet serves in making a potential mate look bigger, a feature that equates to being a more fit mate. A larger coronet also enables seahorses to amplify sounds they produce when they feed. The sounds are thought to help seahorses advertise their presence and the availability of food to other members of their species.
Seahorses lack teeth. Ambush predators, they feed by remaining motionless until their tiny prey swims into their attack zone at which time a seahorse extends its head and sucks its prey into its long tube-like mouth. The majority of their prey consists of small shrimps, fish and other planktonic creatures.
As a rule, when we see a seahorse it is at rest with their muscular prehensile tail wrapped around a stationary object such as a blade of sea grass or a branch of a gorgonian coral. Even at their best, seahorses are poor swimmers, as their equine profile does not translate into the ability to swim like horses run, or even like horses swim. When on the go seahorses rapidly flutter their dorsal fin in order to “propel” themselves through the water while using their tiny pectoral and anal fins for steering. The pectoral fins are located behind the eyes. Seahorses lack the caudal (tail) and pelvic fins found in most fish.
When measured from their coronet to the tip of their outstretched tail most seahorses range in size from 1.5 to 12 inches long. Seahorses occur in a wide range of colors from near black and drab browns to vivid hues of orange, red and yellow. Color and skin patterns are not reliable characteristics when trying to identify species during a dive as individual animals can greatly alter both characteristics. As a result, distinguishing various species in the water is a difficult task even for highly qualified specialists.
Reproduction in seahorses is a fascinating topic. Before breeding, seahorses court for several days in an effort to entice and convince their potential partner of their worthiness. During courtship, a male and female swim side-by-side, sometimes interlocking their tails and sometimes attaching to the same object so they can swirl around in synchronized fashion. If sparks fly the duo eventually ends up in a courtship dance that can last as long as 8 hours. During this dance, the male pumps water through the pocket-like brood pouch located toward the middle of the front side of his body causing the pouch to open and show that it is empty. When the female’s eggs are ready she inserts her ovipositor into the male’s brood pouch where she deposits as many as 1,500 eggs. Not long afterward the female departs leaving the male to protect the eggs. However, in some species, the female will visit the male during the gestation period.
Mr. Mom, as the pregnant male is often called, carries the eggs for as few as nine to as many as 45 days before expelling well-developed, miniature seahorses into the water when the eggs hatch. From that point on the hatchlings are on their own. Less than 1 percent of the hatchlings survive to adulthood. While this percentage might sound small, it is actually quite high when compared to many other fish. The high survival rate is likely due to the fact that the young are so well developed at birth.