Video: Lake Symphony
"Trrr …" - a thin trill of a toad is heard. "Huu, huu …" - the voice of the yellow-bellied toad is muffled. It cannot be confused with the more sonorous "unk, unk", which is issued by the red-bellied toad. "Knock, knock, knock …" - short gurgling sounds of a garlic. And finally, the deafening polyphony of frogs. "Warr, warr, cru …" - this is how the largest lake ones declare themselves. "Coex, coex …" - the voice of a bright green pond, which is a little smaller. "Roor, roor …" - the grass frog echoes them. The spring migration of frogs has begun.
Garlic tree frog (Hyla pulchella) on water hyacinth
They left the places where they hibernated and gathered in reservoirs to lay eggs.
The clutch of a toad cannot be confused with a frog clutch. It looks like a thin cord in which the eggs are arranged in two regular rows. Its length can be up to 7 meters. Such cords can often be seen in shallow puddles. In a garlic mason, the clutch is also in the form of a cord, but it is short and thick, and the eggs in it are in complete disarray.
Frogs usually lay eggs in small lakes and ores in the form of gelatinous lumps. In a fresh clutch, the eggs are closely adjacent to each other, and after a while the shell swells and the distance between them increases. And only toads spawn single, unconnected eggs, but there are usually several of them in one place, near underwater plants.
There are a lot of eggs in the clutch. But out of all their huge number, only a few will successfully develop. Some clutches will die when the reservoirs dry up, others will become food for fish and ducks.
Finally, the embryo will release a special substance that will dissolve the gelatinous membrane that has been protecting it all the time and will come out. From this moment on, the tadpole enters a difficult period of its development, which will end with metamorphosis, that is, its transformation into a young frog.
Depending on the temperature of the water, the transformation of a tadpole into a frog occurs in toads usually in 45-50 days, in a grass frog - in 50-90 days. The larvae of the marsh frog develop the longest (80-90 days), but these tadpoles grow faster than the others, adding a millimeter per day.
It was noticed that in the same pond, where the number of eggs is the same, the number of tadpoles differs greatly in different years. And they grow every time at a different rate. It turned out that when there are a lot of tadpoles, their growth and development first slows down, and then (and this is clearly visible) some remain small, while others begin to grow rapidly. And what else we managed to find out: large tadpoles secrete special substances that inhibit the growth of their small counterparts. Therefore, the tadpoles of those frogs that a little earlier spawned, for example grass, have more chances to successfully complete the metamorphosis.
These substances inhibit the growth of larvae of another species, but they even more affect their congeners, especially those that hatched from the same clutch. What are the benefits of this for large tadpoles? If all tadpoles developed in the same way, then under unfavorable conditions, for example, all would have an equal chance not to undergo metamorphosis and die. Large tadpoles develop twice as fast, ensuring the continuation of the species. Substances secreted by large tadpoles are regulators of the growth and number of tadpoles in the reservoir.
The grass frog tadpoles keep very closely to each other for the first 20-30 days. They scurry in different directions, but do not swim far, and the whole flock moves at the same time in search of food and warm places in the reservoir. After about a month and a half, these clusters become more rare, but the tadpoles still continue to stick together. The formation of clusters was also noticed in other species, for example, the American toad and the cascade frog, with which they began to experiment. It turned out that their tadpoles are able to distinguish siblings from non-siblings - tadpoles from the same and different clutches. We made such an experience. A special aquarium was made, which had the shape of the letter "y". Tadpoles were planted in its central part and streams of water slowly passed from both sides. One is from siblings and the other is from non-siblings.The tadpoles from the central chamber swam towards the siblings. When their nostrils were sealed with a special paste, they ceased to distinguish streams and did not know where to swim. After removing the blotches from the nostrils, the tadpoles again confidently swam towards the siblings. This means that they recognize each other through their sense of smell.