Don’t be fooled by the name of this blog, there are some delectable candies to be had elsewhere in the vast animal kingdom. It may be of interest for amphibian enthusiasts to briefly consider the precursor to their beloved tetrapods; the fishes. Fishes come in over 25,000 different flavors, uh, I mean species. Given this huge number of species, it is not hard to imagine that the diversity of forms, colors, and behaviors in fishes is staggering. Interestingly, 41% of the 25,000 species of fish live in freshwater habitats. This is particularly impressive when one considers that out of all the water on the planet, only 0.0093% is fresh water. Approximately 150 species are diadromous such as salmon or European eels. The take home message is that no matter where you are in this world, if you peer into a body of water larger than a puddle, chances are good that fishes are peering back……And that’s excluding a whole slew of species that actually live in puddles (e.g., killifishes).
Fishes come in a huge range of sizes. The largest fish is the whale shark, which reaches sizes of up to 20 meters. This monster of a fish ironically eats some of the smallest food in the ocean: plankton. There is little debate that the whale shark is the largest fish in the world. However, a more contentious issue among geeky ichthyological taxonomists has been deciding upon what the smallest fish species is. Some argue that Paedocypris, at a mere 7.9mm is the smallest fish, while others believe it to be the sexually parasitic males of an anglerfish species, which measures in at a whopping 6.2mm. What is undeniable, however, is that the smallest vertebrate in the world is a fish.
Many fish breathe atmospheric air. Some do this with a labyrinth organ, while others do this with actual lungs. Lungfishes, you may be interested to learn, are thought to be the closest living relatives to your most treasured tetrapods. Many species of fish live over a hundred years, while others live less than a few months. Fish eat just about everything. Fishes can be herbivores, piscivores, carnivores, omnivores, detritivores, insectivores, and even parasitic to name a few categories of varying degrees of specificity. If something is alive, or recently alive, chances are good that there is a fish out there that will eat it. With all that eating going on, there is also a lot of reproduction.
Fishes are amazing in that almost every single mating system that is known to occur can be found within at least one species of fish. Fish are oviparous, ovoviviparous, and viviparous. Some viviparous fishes, such as certain species of sharks, even have “placentas”. Fishes can be iteroparous and semelparous. At least one species of fish is parthenogenic. Clearly, fishes are an extremely diverse group of vertebrates, and this article has barely even scratched the surface into their fascinating lives. It is my hope, however, that you will no longer summarily dismiss fish as “just fish”, but will rather appreciate the vast amount of diversity that is the fishes.