|

Mythical,
marvelous and amazing - no matter what word is used to describe
them, seahorses capture the imagination as some of the sea's most
unusual inhabitants. But one of the most fascinating features
of seahorse behavior is the way they woo and then brood.
It
all begins with a slow, dance-like promenade through the sea grass.
The male, head bowed, performs an elaborate dance around the female,
often wrapping his tail around her or mimicking her movements.
The male often changes color, his body becoming lighter while
his spine area darkens. During this mysterious mating dance, the
male opens his empty pouch to the female. If the female is satisfied,
she raises her head and intertwines her tail with his.
"The
ritual can last up to nine hours and resembles a sort of ballet,"
said Thom Demas, Tennessee Aquarium senior aquarist. "The
seahorse pair travel up the water column as she transfers eggs
to the male seahorse's pouch on his abdomen, where he fertilizes
the eggs and goes through the pregnancy." In all species
in the family Syngnathide - seahorses, seadragons and pipefish
- it is the male who carries and nurtures the eggs. In the case
of seahorses, the male actually becomes pregnant. Each fertilized
egg embeds into the lining of his pouch, where tissue grows around
the eggs and supplies them with oxygen throughout the pregnancy.
This tissue does not supply nutrients to the eggs; the main source
of nutrition is in the yolk of the egg itself.
The
male seahorse carries the eggs for a period of 10 to 30 days,
depending on the species and water temperature. The babies, which
can number between 10 and 500 depending on the species, emerge
as tiny replicas of the adults, ready to begin life on their own.
Most
seahorse pairs are monogamous - once a male and female
form
a pair bond, they mate exclusively during the breeding season.
Seadragons,
however, have a different style of breeding. With the approach
of warmer weather, male and female seadragons form pairs. Once
paired, both seadragons keep close together, never floating too
far away from their mate. The female seadragon develops up to
300 orange eggs within her lower abdominal cavity. During this
period, the male goes through some of his own interesting transformations.
As the eggs are developing in the female, the tail of the male
enlarges and becomes wrinkled and a network of fine blood vessels
develops. Once the tail is fully enlarged, approximately 120 small
pits, or eggcups, appear in preparation to receive the eggs. The
female then deposits the eggs into the cups, and the male fertilizes
them.
It
takes weeks for these transformations to occur, and during that
time the male seadragon can be seen displaying to the female.
He swims alongside her in a distinct head-up-head-down motion.
Sometimes the female returns a similar motion to the male. Occasionally,
the male approaches the female from the front, turning his body
upside down, possibly showing off his readiness to reproduce.
He also becomes extremely aggressive during this period, chasing
away any potential predators from the female. When the egg transfer
occurs, the female floats upward in an exhaustive state.
Pipefish
also have interesting mating characteristics. Like seahorses and
seadragons, the male is the primary carrier of eggs, but in some
species, the female carries them. In contrast to seahorses and
seadragons, pipefish are not "monogamous." The female
leaves her eggs with several different males, and males may carry
the eggs of several females at one time. In most cases, the carrier
pipefish attaches the eggs to the underside of the belly, where
they are fertilized and incubated.
Certain
species, such as the banded pipefish, dance with one another during
this courtship. They snake between one another, often bending
their bodies in the shape of a half circle or a cross. From time
to time, both move their heads simultaneously in a special rhythmic
bob. Once the dance is finished either the male or female swims
off, with eggs attached to its abdomen.
After
the young hatch, their parents play no role in their upbringing.
Very few young seahorses survive to adulthood, falling to predators,
swept away by ocean currents or harvested by humans for a variety
of uses.
|