Jessica Suzanne Dudley does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment. Supplying oxygen to their growing offspring and removing carbon dioxide is a major challenge for every pregnant animal.
Our new study, published in the journal Placenta , examines how pregnant male seahorses Hippocampus abdominalis provide oxygen supply and carbon dioxide removal to their embryos. We examined male seahorse pouches under the microscope at different stages of pregnancy, and found they develop complex placental structures over time — in similar ways to human pregnancy.
Read more: Curious Kids: Is it true that male seahorses give birth? Male pregnancy is rare, only occurring in a group of fish that includes seahorses, seadragons, pipehorses and pipefishes. Pot-bellied seahorse males have a specialised enclosed structure on their tail. This organ is called the brood pouch, in which the embryos develop. While inside the pouch, the male supplies nutrients to his developing embryos, before giving birth to up to 1, babies.
Embryonic development requires oxygen, and the oxygen demand increases as the embryo grows. The male will then begin the mating and gestation cycle again just days after giving birth. Pipefish get their name for their long, cylindrical, pipe-shaped bodies.
They essentially look like a stretched out Seahorse. They are fairly small fish and grow on average to be Pipefish are unique from their relatives for the fact that some species have a pouch, like Seahorses while others attach the eggs to the underside of their body.
Eggs are transferred from the female to the male following a courtship dance where both the male and female will wiggle and shake, indicating that it is time to mate.
The female will then deposit the eggs into the pouch or underside, during which both male and female will float upwards together. Caring for the offspring requires a lot of nutrients and energy from the male.
In some cases, the male may cannibalize their own offspring and consume the embryos which is referred to as filial cannibalism and is actually fairly common in the fish world.
Sea dragons are an interesting group of fish, closely related to Seahorses. There are only three species, all of which can only be found in the warm coastal waters of Australia. The most notable and well known species is the Leafy Sea Dragon, which has leaf-like fins that helps them to blend in with marine vegetation. Male Sea dragons do not have a pouch as Seahorses and some Pipefish do.
Instead, they carry their offspring on the underside of their tail where they have a brood patch. The brood patch provides oxygen to the young during development. Once the eggs have been attached to the brood patch, the male will then turn his tail upwards and fertilize the eggs. Hatching happens two to four weeks after fertilization in an incredible display like the one shown above.
Anywhere from 50 to over 1, baby seahorses, or fry, will hatch at one time, and the father's contractions can last up to 12 hours! Once born, the fry spend two to three weeks drifting with plankton in the ocean, making them very susceptible to predation.
Only about one in 1, will survive to adulthood. Pipefish, on the other hand, use a slightly different method. These seahorse cousins have similar-looking mouths and tiny bodies, but appear more stretched-out than seahorses. Also like seahorses, female pipefish drop their eggs into the male's brood pouch, which is on their belly, close to their heads.
There, they fertilize the eggs and carry them until the offspring hatch a couple weeks later. Males c an carry between 5 and 40 offspring in their own brood pouch. An interesting quality of pipefish is their ability to use resources differently for broods of offspring.
Males of this species have been known to not take care of offspring that come from a mother they aren't particularly fond of. Males put more resources into broods from larger, more attractive females. They also don't put as much effort into ensuring survival in a brood if it just hatched a successful, healthy brood.
0コメント