Things we do for love: the seahorse

I wouldn't be wrong if I should say some pregnant women wished their husbands were the ones who are pregnant while they go back to live their normal lives. I wouldn't blame them for that. Who wouldn't want to save themselves from some stress and pain that comes with childbirth? I can imagine the stress they would be going through. Pains and discomfort in their body and also a need to find new clothes because of their bulging belly.

Well, their wishes may not come through but for some particular animals, this is their reality. Where the males get pregnant and the females go back to their daily lives. I am talking about the seahorses. In one of my previous posts, I explained that seahorses are fish and not horses that live inside water. Although their head and their neck appear to be like that of the horse's they are as equal to a fish as the tilapia, Salmon, catfish etc.

They are not horses that live inside water

The seahorses are saltwater fish so named for their unique appearance. They have a head and neck that resembles the horse. They also have a body shape that makes them seems to be standing upright with a curling tail which they use to hold on to grasses and other materials in water. They do not take after the speed of hoses on land as they are slow swimmers so you may not likely find them doing long voyage but rather you'll find them attached to objects underwater with their tail. In the process of doing so, they try to feed on smaller crustaceans swimming along their path.

They belong to the class of animals known as Actinopterygii. You'll find all the other bony fishes in this same class too. The males are differentiated by the presence of a pouch on their ventral side. What got me interested in this animal is their unique reproductive characteristics. The males get pregnant which is not what you may likely come across in most other animals.

How do the males get pregnant?

You really don't get to see pregnant daddies every day but not with the seahorse. Let's talk about the How before we talk about the why of the seahorses' male pregnancy.

A study conducted on a species of seahorse, the dwarf seahorse, to find out how the male pregnancy takes place. It was found out that the process starts with a courtship which lasts through about four phases. During the period, the fish displays distinct behaviors such as attaching their tails in the same branch of leaves, vibrations and also assume bright coloration. The first phase which marks the start of the process starts some days before the male gets pregnant while the last phase occour on the last day of the courtship.

The first phase which the called "reciprocal quiver" initiates the process. The prospective pairs start very early in the morning. They whisper love in a way different from humans. They communicate love by standing adjacent to each other and the male quiver while the female responds by doing the same. The female changes the position of her grip on the branch to create a movement. A colour change is also accompanied by this process. A bright colour to mark their friendship. Maybe something similar in humans will be blushing. This courtship behavior continues every morning until the last day of the courtship when they move to another courtship phase.

Phase 2 is called "pointing-pumping". Courtship starts earlier this day as the 2 other phases will also take place the same day. The female is seen in a pointing position toward the male. The male reacts to this by bending away and then vibrating. The female does not become brightly coloured in this phase.

Phase 3 is called "pointing-pointing". Just as the name, this phase is different from phase 2 because the male responds by pointing back instead of leaning away. In this phase, both fish assume a bright colouration and the end of this phase is usually marked by the departure of the male.

Phase 4 is the last stage of the courtship process and it is called "rising and copulation". The brightly coloured pairs from phase 3 stay close together and can be seen swimming upright in the water column together. The female is very active at this phase and after rising the middle of the water column, the female use her specialized organ called ovipositor to deposit its eggs into the male's pouch. The two fish swim away to find food to eat. The pregnancy of the male seahorse, therefore, the deposition of the female eggs in its own brooding pouch.

What happens in the male's pouch?

The male fertilizes the eggs in its pouch by releasing the sperm. During the courtship, when the male fish open its pouch for the female to deposit the eggs it also takes on seawater. This allows for a suitable environment for the development of the embryo. The male releases nutrients into the pouch which the embryo uses for their development. Also, the male pouch helps to excrete the waste product of the embryo and supply oxygen too. The pouch acts like a womb or, more precisely, an incubator for the survival of the embryo.

The number of days the eggs spend in the pouch varies between a week to 4 weeks depending on the species, which according to project-seahorse there are 44 Species of seahorses. The male seahorse goes into labour, usually, at night birthing the young live from its pouch. It does this by contrasting its muscles and "sneezing" the young life fish out. Sneezing may not be the right word to use but the process looks similar. I've got a video from National Geographic YouTube channel showing how a male seahorse gives birth.

After giving birth to the young, the daddy seahorse does not take any other parental responsibility neither does the mother. The young are born independent and they have to start feeding for themselves. The seahorse is ready to get pregnant again few hours after that or few days depending on the females.

Why would a male want to get pregnant?

Could this be one of the things males do for love? Or because "daddy" seahorses so much love their darling females they don't want them to experience the stress of pregnancy? This question has been a topic of interest for various researchers but from their various results, one can't conclusively give a reason.

Some researchers suggested that the male seahorse carries the egg during the period of fertilization to reduce the total cost of energy demand on the female. Saving that energy from the female will probably give more chance to more production. Also, another hypothesis is that the male gets pregnant to speed up the whole process. Getting pregnant will give the female more time to recover and produce more eggs.

There was a popular belief that the seahorses are faithful partners with a male and female staying together for better for worse. But contrary to that opinion that all mating pairs stick together for life, this article show that to be false.
Thanks for reading to the end, I hope to bring you another interesting read very soon.

Reference

• Romance of the Seas: Strange Mating Habits of the Seahorse
• https://en.m.wikipedia.org/wiki/Seahorse
• The biology of seahorses: reproduction
• Courtship Behavior in the Dwarf Seahorse, Hippocampus zosterae
• iseahorse | frequently asked questions
• Seahorse Fathers Take Reins in Childbirth