Pregnant male seahorses fed germ

Australian biologists have found the first experimental evidence of matrotrophy (the transfer of nutrients to the embryos hatched from them male) have seahorses. Dry weight and lipid content of embryos during embryogenesis has not changed — it could only happen if the nutrients got from the outside. Article published in the journal Journal of Comparative Physiology B.

Live birth appeared during the evolution of vertebrates over 150 times, but only in the family of a needle fish (Syngnathidae, these include fish-needle and seahorses), the offspring hatching males. This group is particularly interesting for scientists because it is possible to explore the evolution of mechanisms of bearing offspring without reference to the reproductive system of females.

For the development of the germ requires a large amount of energy and nutrients. To their developing bodies are two ways: either from the yolk, where all the necessary substances stored in advance, or with the help of matrotrophy when the embryo comes from the mother for more food.

In the case of the needle matrotrophy turns into matrotrophy, however, the mechanisms of transfer of nutrients from the male hatched offspring is practically unknown. Scientists have proved that matrotrophy have three kinds of fish-eagle — with the help of labeled molecules were able to trace the transport of amino acids from male embryos. For seahorses is known only indirect evidence of matrotrophy: in their brood bags is a lot lipid droplets and secretory cells, and associated with the transport of substances from the genes of these fish are activated during pregnancy. Directly to prove the transfer of substances from the male to the offspring while no one could.

A group of scientists under the leadership of Camilla Whittington (Camilla Whittington) from the University of Sydney tested whether embryos seahorses (Hippocampus abdominalis) additional substances from the bearing of their males. The researchers compared dry mass and lipid content of eggs immediately after fertilization and newborn fry. If the embryos grew only at the expense of the supply of nutrients eggs, their weight decreased, and additional reinforcement from the father would retain the dry weight constant or even increased it.

Dry mass of newborn sea horses did not differ from the dry weight of eggs after fertilization; the lipid content in these two stages also were equal (p > 0.05). During development, the embryo needs to lose some mass due to catabolic processes: for example, the eggs of viviparous bony fish during pregnancy lose 30-40 percent of its mass. It turns out, at least a small amount of nutrients must reach the embryo seahorses from males.

The authors note that there is an alternative explanation for why the dry mass of embryos have not changed, they could absorb matter from the other, undeveloped, embryos, their brothers and sisters. Therefore, in order to speak confidently about the existence of matrotrophy, it is necessary to conduct additional studies, for example, isotopic labels.

Scientists have also described some features of the structure Zeigler bags of seahorses, because of their anatomy and physiology very little is known. In the first three days of development the embryos are deeply immersed in the epithelium of the bags, holes with separate eggs separated epithelial “walls” or completely closed to them. May transport substances between the male and the embryo is very much similar with the placenta way — in close contact tissue, but this hypothesis should be tested in future work. In the later stages of pregnancy (15-20 days), the embryos hatch, but continue to absorb substances from the yolk.

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