Seahorses and pregnant men: Why do male seahorses give birth? How Did Male Pregnancy Come About In The Evolutionary Process?
The strangest creatures on our planet are undoubtedly those living in the sea. Octopuses that decide each arm individually, dolphins that cross land to sea, terrifying sawfish and saw sharks are just a few of them. In fantastic stories, no one knows the seahorses that ride and ride. The most popular feature of seahorses is undoubtedly the phenomenon known as male pregnancy.
Of course, this is not the only feature of seahorses. Seahorses, which most people are surprised to learn are fish, have tube-shaped fused mouths, exoskeletons covering their bodies, vertical bodies, angular tails, and an evolutionary past in which they return from the brink of elimination in their original way! I mean, in any case, they're an unusual creature.
In fact, most features of seahorses are not a "first" or "unique only to seahorses" in the Animal Kingdom. For example, like seahorses, balloon fish do not have pelvic fins, razor fish have a vertical body, sturgeons have bony structures, and seahorses and pipes give birth to men... But the collection of all these features in one living thing brings out a species of fish that is unlike anything else: seahorses.
Interesting and unusual features of seahorses
First, let's get to know these interesting animals in general: seahorses are a common name given to Animals of the genus Hippocampus, which are in the class of ray-finned fish. It is no coincidence that the name of the genus and the hippocampus region in our brain bear the same name; this region in the brain is given this name because it looks like a seahorse. The hippocampus is derived from the composition of the words "horse" (hippos) and "sea monster" (kampos) in Greek.
Seahorses commonly live in shallow tropical and temperate waters, these creatures swim upright, are relatives of sea needles, and range in height from 1.5 cm to 35 cm. Because of their body shape, seahorses are quite incompetent swimmers, and if they get caught in the current, they can easily die of fatigue. They push themselves forward, flapping the small fin on their backs 35 times a second. They also use even smaller fins on the back of their heads for orientation.
Thanks to the curling, grasping structure of their tails, they cling to seagrasses, corals and inhale plankton and small crustaceans that drift around them. They're very voracious. They can eat 3000 or more saltwater prawns a day by constantly feeding.
Some species are in danger of extinction due to widespread natural coastal extinction worldwide, pollution and widespread collection for traditional Asian medicines.
Let's now take an overview of 3 interesting features of these unusual animals.
Vertical Body
The closest (sister) genus to seahorses today are dwarf pipe horses ("pygmy pipehorse, Hippocampinae"). They look almost exactly the same, but they are separated by a couple of critical differences: body direction and habitat. Seahorses have vertical bodies, while dwarf pipe horses have horizontal bodies. Seahorses live in seagrass meadows, while dwarf pipe horses live on algal reefs.
Fossils of seahorses and other similar creatures are very rare, and the ones found do not show a complete process. In such cases, it is very useful to look at the genetic records. Molecular findings indicate that dwarf pipe horses and seahorses separated during the Oligocene epoch (about 25 million years ago).During the Oligocene period, shallow waters and seagrass are known to have increased due to tectonic movements. Probably, those with vertical body structure from the ancestors of seahorses were able to survive; because they should not have been noticed in the growing seagrass.
This explains why seahorses have vertical and dwarf pipe horses have horizontal bodies: while seahorses should not be noticed in Moss grasslands, there is no such pressure on dwarf pipes. In other words, although we do not have enough fossils, we can understand when and why seahorses and dwarf pipe horses separated from a common ancestor by studying the regions and genetics in which they live today. In fact, from this point of view, we can see how our understanding of the evolutionary process is built together and complementary by fossils and genetic findings.
Square-like tail
Although most fish provide thrust with their tail, the Seahorse's tail is quite blunted in terms of thrust. Seahorses use the dorsal fins almost entirely behind them to swim and give themselves direction, and the pectoral fins on either side of their heads. The tail is mainly used to hold onto a moss or coral, and has also been shaped accordingly in the evolutionary process. The biggest feature that distinguishes the Seahorse tail from all other tails is that it is square-like (4-pointed).
Since he spends almost all of his time in non-straight (forward-curved, back-curved, side-curved, or support-grasping) positions, the structure of the Seahorse's tail should not be damaged by frequent changes in movement. The alignment and structure of the tails of seahorses as they move from one position to another should not be disturbed.
Through the experiments, it is seen how much this 4-pointed tail structure really helps to maintain alignment. This type of tail is not only in alignment; it also does a great job of absorbing impact and increasing the clinging surface area. In fact, the use of this type of mechanics in robotic tentacles and arms is also considered.
Male Pregnancy
Seahorses are not unique just because of their shape, which roughly resembles a horse. Some species are monogamous, unlike most fish (although they can also change mates after breeding). More interesting is that the only group of animals that carry unborn Cubs, along with their close relatives, sea gejders and pipes, is a male rather than a female. The fact that the opposite parental role in this form is seen in 3 separate species instead of 1, and that these 3 species are genetically closest relatives to each other, is one of the most beautiful proofs of evolution. This indicates that male pregnancy evolved in the common ancestor of these 3 species, and then transferred to these 3 descendant species. As these species differed evolutionarily from each other over generations, they became separate species, but retained their "male pregnancy" characteristics.
Our knowledge of the 35 seahorses that exist today is quite limited; but one thing we do know is that male seahorses have a pouch on the abdomen. When mating, the females lay their eggs in this pouch, and the male fertilizes them himself. The male carries the eggs in his pouch until they crack, then releases fully formed, shaped miniature seahorses into the water. You can see this in the video below.
Do men conceive ?
It may seem inconceivable how men take on such a role, but in fact there are not many obstacles in theory for men to conceive. If a baby will be placed in the male's abdominal tissue and a bridge can be established to exchange nutrients/waste by connecting with an organ such as the Liver, Men can also become pregnant.
However, this requires the reorganization of many evolutionary adaptations and leads to the fact that maintaining roles in female-male evolution is a simpler strategy. Pregnancy of men is extremely dangerous for their health at this stage, as it can lead to internal bleeding and death.
Moreover, even if the baby reaches full development after male pregnancy, delivery by caesarean section will be required (or evolutionary rearrangement of the reproductive organs will be required). Bioethicist Glenn McGee sums up the situation this way:
"It's not a question of whether a man can get pregnant. The question is whether a man who becomes pregnant can survive..."
What Is The Evolutionary Advantage Of Male Pregnancy?
Rapid reproduction is undoubtedly a great trump card that can trigger rapid evolution. This trump card is the key to the rapid evolution of living things that reproduce by mitosis, such as microorganisms; but for some reasons, such as sexual reproduction, finding mates, and producing reproductive cells, it reduces this speed. Of course, this does not mean that sexual reproduction is a "bad" mode of reproduction than asexual reproduction. For example, through asexual reproduction, both evolution works faster and diversity is actively created. It's like, " an arm is better than a fin."it's like we can't generalize like; because in different conditions, different characteristics can be advantageous. Seahorses also seem to have found a combination of variety and speed.
No confusion here: in seahorses, males also produce sperm, females produce eggs, so there is no difference in this regard. But what has changed is the location of fertilization. Therefore, for a while in zoology, it has been debated whether what is biologically seen in seahorses is a real "male pregnancy" or a "male offspring carrier". Question marks in these definitions often relate to how terms are defined. For example, it should not be so surprising that men become pregnant, since the concepts of "male" and "female" are not defined in biology in relation to the "side that gives birth to offspring" ; it is related to sex chromosome types and gamete size. Those with larger gametes are called" female", and those with smaller gametes are called" male". Therefore, although the fact that females give birth to offspring in almost every living being gives rise to the idea that offspring have something to do with femininity, such a assumption is not true from the point of view of biological terminology. Seahorses and other male-born species are also a good example of this.
What happens in seahorses is that instead of releasing eggs and sperm into the water or transferring sperm to the female body, the egg is transferred to the male body. In fact, as with most animals, intrasexual selection is largely on male individuals; that is, males struggle for females. But this gives an interesting example from nature: the men of seahorses fight "to get pregnant"!
Genetic studies in seahorses have shown that gene multiplication is behind the emergence of this trait. C6ast genes responsible for producing HCE and HCE2-like enzymes associated with pregnancy and embryo development were copied one after another in seahorses and repeated exactly 6 times. 5 of these 6 copies are activated when the male seahorse is pregnant. In addition, according to molecular findings, the evolution of seahorses is surprisingly dynamic and fast.
Probably the biggest reason why males, rather than females, conceived was to accelerate the reproductive process and evolution of seahorses. So much so that although more than a thousand baby seahorses are born each time, only a few survive. Such a small number may not be enough to protect the population. Increasing the number of zygotes created to increase the number of surviving offspring would be enough to harm the female seahorse. Currently, a third of the bodies of female seahorses are already reserved for egg production, they do not have as many areas to carry offspring as male seahorses. Even when male seahorses conceive, only a few out of a thousand cubs survive. On the other hand, if female seahorses without space to produce even a thousand offspring were conceived, they would probably become extinct.
For this reason, copying pregnancy genes and giving the man a uterine sac may have saved the lineage of seahorses. The reason for this is focused on 2 angles:
- There was more space in the male body. So there was room for more possible offspring.
- Egg production takes longer than sperm production.
Result
As you can see, seahorses are one of the most unusual examples of evolution. In order to continue their lineage, they went through mind-boggling changes such as vertical body, tube mouth, male pregnancy, angular tail, and took on the iconic characters we all know.
In our opinion, seahorses are one of the most beautiful proofs that each species has its own evolutionary adventure and how even the most "simple" creatures have amazing features and backgrounds. In addition, seahorses remind us that everything can be reversed when necessary and appropriate conditions are met in the evolutionary process.