As most of you should have known, male pregnancy is
ubiquitous in the fish family of Syngnathidae, which includes species such as
pipefishes, seahorse and sea dragons. It is also the only family in the animal
kingdom to exhibit such characteristics.
Seahorses have a
unique way of courtship and their display of affection is to me, amazing.
Step 1: Let's Dance!
When both seahorses have mutual interest in each other, they
court for several days. They may change colours, swim side by side holding each
others’ tails and twirl around in unison. They may even cling onto the same sea
grass.
Step 2: C'mon baby..
After a few days of courtship, the male pumps water through
the egg pouch on his trunk. This would balloon and gape open to display its
emptiness. Once the female’s eggs reach maturity, she and her mate abandon
grips on any anchors and drift upward out of the sea grass, often spiralling as
they rise. After the female squirts her egg, her body slims while the male’s
bulges. They both sink to the bottom while the female swims off.
Step 3: Constant Loving Care
The male’s pouch provides oxygen for 21 days by
having prolactin, the hormone that governs milk production in women. Throughout
his pregnancy, his mate visits him daily for about 6 minutes of interaction.
They change colour, hold each others’ tails and wheel around see grass fronds,
just as they did during courtship. The female swims away and they
continue their daily business until the next day.
Step 4: Only You~
Interestingly, the female refuses to mate with other males
during the pregnancy period of her ‘husband’. Such infidelity cannot be
tolerated in a monogamous relationship as the seahorses’.
During lecture, we learnt that some species have sex-role
reversals as the female grew more aggressive and become physically bigger in
size. In the seahorses’ aspect however, the males continue to be the aggressive
ones who engage in tail-wrestling. Interestingly, though the male seahorse is
the nanny of the child, he remains to be a macho dad. Or should I say mum? 
References:
http://www.bio.tamu.edu/USERS/ajones/seahorse.html
http://jhered.oxfordjournals.org/cgi/content/full/92/2/150
http://www.sciencenews.org/articles/20000311/bob9.asp
http://www.spiracanada.com/spiralbound/2004/beltaine/seahorse.jpg