The Torah speaks about the "frog," in the singular, coming up from the Nile. Previously, I have discussed how many people are oblivious to the pshat in this passuk. But for now, let's discuss the famous derash - that there was one frog, which multiplied to become hordes:
“And the frog came up, and it covered the land of Egypt” …Rabbi Akiva said, there was one frog, which then multiplied all over the land of Egypt. Rabbi Elazar ben Azarya said, Akiva, Why do you involve yourself with aggadata? Finish with your words and go to study nega’im and ohelos. There was one frog, it called to the others, and they came. (Talmud, Sanhedrin 67b; Midrash Shemos Rabbah 10:5; Yalkut Shimoni Shemos 8:183)
Rabbi Akiva states simply that the frog multiplied, without explaining how this took place. It could well be that he means that it procreated in the way that frogs usually do. However, the Midrash cites a more unusual version of Rabbi Akiva’s opinion:
One verse says, “and the river swarmed with frogs,” and another verse says, “and the frog came up.” Rabbi Akiva said, There was one frog, and the Egyptians were beating it, and many frogs showered from it (matezes). (Midrash Tanchuma, va’era 14; Tanna D’Vei Eliyahu Rabbah 7)
There is also a well-known version of this Midrash (I have seen it cited from Midrash Aggada, but I haven't yet been able to track down the original) in which it produced new frogs from its mouth.
Now, the phenomenon of childbirth, as with all other areas of life, takes on remarkably diverse forms in the natural world. However, whether producing eggs or live young, most animals are identical and ordinary in that the young emerge into the world from an orifice located at the rear end of their mother's body. Of the entire animal kingdom, the only exceptions to this rule that I know are seahorses, in which the male takes the eggs into a pouch until they are ready to hatch, and certain species of frogs/ toads (scientifically, there is no distinction between the two names).
The female pipa toad (also known as the Surinam toad) carries her eggs embedded in a spongy layer of skin on her back. After four weeks, the young pop out of her back as perfectly formed toadlets, as you can see in this amazing video:
Then there is the remarkable Darwin's frog, Rhinoderma darwinii. After the female Darwin’s frog lays 20-30 eggs on land, the males gather around and wait for the eggs to begin to hatch into tadpoles, which takes 10-20 days. When the tadpoles move inside the eggs, the males flick several of the eggs into their mouths with their tongues and place them into their vocal sacs. Inside the vocal sacs, the eggs hatch and develop into froglets, whereupon they emerge from the males’ mouths.
A similar but even more extraordinary amphibian is the Australian gastric brooding frog. The species include the Northern gastric brooding frog (Rheobatrachus vitellinus) discovered in 1972, and the Southern gastric brooding frog (Rheobatrachus silus) found in 1984. These frogs are already presumed extinct; the former was last seen in the wild in March 1985 and the latter in September 1981. In the few years that they were known to man, however, they made a remarkable impression.
The female gastric brooding frog actually fully swallows her 18-30 fertilized eggs, which then develop in her stomach. The tadpoles have undeveloped tails, lack teeth and do not feed; they live off their yolk sacs. As the tadpoles grow inside their mother, her stomach expands until it occupies most of the body cavity and she cannot even fully inflate her lungs. Remarkably, the stomach does not produce hydrochloric acid (the digestive juices) during the brooding, period; this prevents the digestion of the young, but it also prevents the female from feeding. The gestation period inside the mother is 6-8 weeks; she then gives birth by opening her mouth. Baby frogs come up to her mouth and then gradually leave, while the mother keeps her mouth wide open. If a baby tadpole does not leave the mother’s mouth, she re-swallows it, to be born later.
Remarkably, then, the same extraordinary birthing procedures that are attributed to the frog of Egypt are actually found in real frogs today. What are we to make of this?
I would not infer that it was those species of frogs that acted in the Egyptian plague. After all, these frogs are not found anywhere near Egypt and were unknown until quite recently; nor are they capable of giving birth to enough young to swarm over the entire country.
When I was more mystically inclined, I used to explain it as follows: that the concept of giving birth through the mouth, or from the skin of the body, must relate to the fundamental spiritual essence of the frog. This therefore has manifestations in both the unusual frog species, and in the unique frog of the Egyptian plague. I related this to how the frog often appears in rabbinic literature as symbolic of a Torah scholar (who studies at night, just as the frog croaks at night), and of a tzaddik who is mosar nefesh (see Perek Shirah for details). The frog that gives birth through its mouth is parallel to the Torah scholar who produces his students – rated as his progeny – through his mouth, the medium of teaching Torah. The other explanation, of the frogs being produced from the frog’s skin, parallels the Torah scholar producing students through his body’s actions and good deeds. The Egyptians, who tried to suppress all this (which is given in the Zohar as the reason for the frog plague), were thereby taught a lesson.
But this whole idea of spiritual essences which are manifest as various creatures in this world, while considered by many to be an absolutely normative understanding of Judaism (as per the Torah being "the blueprint of the world,") is not at all consistent with a rationalist, Maimonidean style understanding. Yet on the other hand, it seems just too extraordinary to dismiss as coincidence - that the two bizarre methods of reproduction described in the Midrash just so happen to actually occur with frogs, of all the different creatures in the world.
I'd be interested to hear readers' thoughts on this.