Category Archives: Herpetology

Catching Anacondas

Some things that are done impulsively, and perhaps recklessly when considered afterward, make for the best memories. I don’t know if I would do this again, if given the opportunity, but I am glad that I did it once. The snake was not harmed, and thankfully neither was I, and after the experience I have a much deeper reverence for species and other large snakes, and their incredible constrictive power. Few animals can match the Green Anaconda; I could barely manage to control this one, which was not yet full grown. This encounter happened in the Llanos of Venezuela in 2007, at Hato Masaguaral, Guarico. My video of an anaconda constricting a Spectacled Caiman was presumably of a different individual snake than the one shown in the videos below. All three were filmed within 0.5 km of each other.

 

On death as the mother of beauty, and frog embryos.

Embryo_Deformities“Objects which in themselves we view with pain, we delight to contemplate when reproduced with minute fidelity: such as the forms of the most ignoble animals and of dead bodies. The cause of this again is, that to learn gives the liveliest pleasure, not only to philosophers but to men in general…” — Aristotle, in Poetics (335 B.C.E.)

In a large egg mass of the Wood Frog (Rana sylvatica),  I observed several deformed embryos, each grotesque, beautiful, and captivating to the eye. Most of the frog spawn contained tiny spherical blastulas, each rapidly dividing according to its unique set of genetic instructions, but the deformed individuals took on many disturbing shapes. Perhaps the bane of their development was a single genetic mutation, an error that occurred during recombination that resulted in a gene that did not function the way it should. One tiny glitch in development, and before long the cumulative effects of the change are manifest in a striking departure from the typical Bauplan of the species.

In many cases, the result of such a gene mutation will be something akin to these deformed embryos, an utterly failed organism that will not survive to adulthood, much less transfer its genes to the next generation. In other cases, the mutation will not preclude adult development, but will nevertheless have some strange detrimental effect on the animal (e.g., infertility or deformed limbs); this animal will be out-competed by its neighbors, and the mutation will not persist very long in the population, even if it survives a generation or two.

But every once in a while, on the most fortuitous of occasions, such a mutation will actually cause a change that improves the fitness of the mutant. Perhaps it causes the frog’s webbing to extend all the way to the end of its toe rather than to the first knuckle. Such a slight adjustment might allow it to be a faster swimmer, thus facilitating its survival and reproduction.

It is a wonderful thought:   That which is most abhorrent in Nature provides the raw material for Its evolutionary transformation, and thus Its beauty.

WoodFrog_COLLAGE

It’s pretty amazing that you and I started our lives as blastulas. In the early days following our conception, we were little more than a ball of cells, rapidly dividing according to the instructions in our genetic code (found in the nucleus of every one of those cells). As a consequence of our shared evolutionary history, all vertebrates begin their lives this way; our genetic code is comprised of thousands of nucleotide sequences, each containing a set of instructions, “build this protein, build that protein, etc.”, and the cells keep replicating and replicating. Eventually, just like building a massive spaceship or castle out of legos, a structure that has simple beginnings gets more and more complex, and the differences that we observe between species start to manifest themselves in development according to each species’ unique DNA blueprints.

Here are some photos that I took of embryogenesis in the Wood Frog (Rana sylvatica). In the first picture you see the blastula, a little ball of cells that is growing and growing as the cells continuously divide.  Eventually, the blastula starts to fold inward (i.e., gastrulation) and we start to see the bilaterally symmetrical body plan take shape. The white stuff at the bottom of the second picture is the part that will eventually turn into the frog’s anus. The embryo keeps growing and begins to elongate. In the third picture in the sequence (center left), we see the head begin to differentiate. The frog’s brain is now beginning to form (upper right of the embryo in the center left pic), and the central nervous system and other vital organs are all developing as per the instructions found in the genetic code. The very same process happened to you and I in the earliest days of our lives.

I went away for a few days, and when I returned the tiny embryo had developed into a healthy tadpole (bottom picture).  Eventually, as per the instructions in its genetic code, the animal grew legs and transitioned into a terrestrial lifeform as an adult Wood Frog (center right). Next year, this frog (if it survives) will find a mate and start the reproductive cycle all over again, just like its ancestors have done for millions of years. We have been doing the same thing, and if you trace our family trees back far enough, they eventually converge. That’s right, this frog and I share a common ancestor. It is one of the most beautiful and profound truths of nature, and for me, a source of deep meaning. The proof is right there in our shared genetic code, and in the highly conserved early stages of embryonic development.