Usually the first lunch for the tadpoles is the remains of the egg shells. Having eaten the walls of their former home, the children of tailed amphibians go in search of food, which is not difficult to do with its abundance, so the eyes and hearing at this time are not yet developed. Only the organs of the lateral line function. Finding food is helped by the olfactory organ - paired fossae in front of the eyes - and tactile papillae located on the lips.
Pond frogs (Rana lessonae). © Photo by Valeria Milyutina
The larvae of lung-free salamanders, hatched from the testicles, have a rather large yolk sac, providing them with food for the first time. Larvae are very different from each other in the intensity of use of their stocks. Some of them intensively consume yolk, grow rapidly and soon switch to self-nutrition. Others, on the contrary, consume food resources sparingly, grow slowly and begin to hunt late. As a result, siblings soon after hatching from eggs already differ greatly in size, which means they hunt different game and did not interfere with each other. And yet, with great crowding, the growth and development of predatory larvae of salamanders begins to slow down.
The herbivorous tadpoles of frogs and toads are much less likely to fall into a similar situation. With the most significant accumulations, they are not able to destroy more than 10-12 percent of the food resources of the reservoir, while salamander larvae are able to utilize 60 percent of the food reserves available to them and then begin to starve. Therefore, the density of tailless amphibian larvae can be very significant, but certainly not unlimited, when the limit is exceeded, the development of tadpoles begins to slow down and delimitation occurs among the larvae. Some of the nicknames slower their development more than others. Between them, there is a significant, every day increasing difference in size and, most importantly, in the degree of development. And since the age of the tadpoles is determined not by the number of days lived, but by the stage of development that he has reached, larvae of different ages are now in the pond.
Food extraction takes most of the life of amphibian larvae. The larvae of tailed amphibians and their adult parents have a lot in common in hunting methods, therefore, leaving water bodies in the fall, they can already earn their own food. Frogs are worse. They must turn from vegetarians into hunters. Fortunately, the eating behavior of amphibians is innate. Babies have only 2-3 days to practice opening their mouths and turning in the direction of prey. At first they often miss and miss their prey, but gradually things are getting better.
Of course, for the hunters to be full, there must be a lot of small and minute game: midges, mosquitoes, small flies, but most often there is enough food, and the kids grow, and the northerners also accumulate fat, without which they can not survive the long cold winter.
Don't push me on the psyche
Amphibian larvae hatching from eggs laid by one specific frog from the first days grow and develop unevenly. As a result, very soon between siblings there is a significant difference in size and development. Here, one of the basic laws of life of young amphibians enters into force, according to which amphibian larvae of different ages are not supposed to be friends with each other. They are connected by a very strange relationship. In the company of younger sisters and brothers, older tadpoles accelerate their growth, forcing the kids to slow down their development. The resulting disengagement continues to worsen. The situation described above is easy to create in an aquarium populated by the larvae of Russian grass frogs.
The antagonistic relationship between tadpoles is biologically justified. They prevent an excessive increase in the number of amphibians. Feed reserves in Meshchera ponds, for example, allow the larvae of the muzzle frog to grow and develop normally, while there are no more than 25 eggs per 1 cubic meter of water. In this case, 4-5 percent of the larvae safely turn into frogs and go ashore. If the density of eggs in the same area increases to 60-70, only 1 percent of the frogs go ashore.
The process of limiting the number begins to operate even at the calf level. In one of the Norfolk ponds, over the course of different years, 15 to 75 female spotted ambists spawn, laying a total of 3.5 to 15 thousand eggs. With such crowding, part of the eggs die, and only 33 to 10 percent of the larvae survive, respectively. Self-regulation of numbers is necessary for the well-being of any animal species.
In his company
Tadpoles are companionable creatures, which cannot be said about their parents. Ostensibly to feel at ease, they absolutely need a society of their own kind. Larvae of the midwife toad and common toad in peer companies feel more confident, grow faster and turn into toads earlier than those grown in isolation. Favorable - it is the peer company, but the presence of older depresses the development of young larvae, especially the first 2-3 weeks of life.
Tadpoles usually form flocks. In clusters, the larvae either arrange a flea market, randomly swimming in different directions, or, like fish, coordinate their actions. In ordered flocks of tadpoles of a smooth spur frog, all members of the association are kept strictly parallel to each other, although their heads can be directed in exactly opposite directions.
For the occurrence of ordered clusters, the participation of vision is not necessary. Such flocks are preserved at night. Interaction between larvae with the help of vision is possible at a distance equal to the double length of their body. The interaction in the dark, carried out on the basis of the testimony of the lateral line organs, occurs at a distance 2 times smaller.
The tadpoles somehow recognize and remember each other. If the larvae that had just hatched from the eggs were seated in separate test tubes, then connected only a day later in a large common aquarium, they did not show a desire to form clusters. Larvae of the same masonry, divided into two groups, after 24 hours in a common pond keep independent groups and do not mix with each other.