Chordates

What the Fish? Episode 4: Sneaker Males Are My Anemone

For most fishes, reproduction involves eggs and milting, which is like crop-dusting with sex cells (aka gametes). The vast majority of fishes are oviparous, which means they lay eggs that are fertilized and develop outside the mother's body. In these situations, males typically milt, which is the release and spreading of their gametes, onto the eggs that have been deposited in the environment. In ovoviviparous fishes, the eggs develop inside the body of the mother, and male gametes have to be passed into the females’ body through specialized structures, such as claspers (modified pelvic fins) in sharks or gonopodiums (modified anal fins) in guppies. Live birth (viviparity) has also evolved in a number of lineages of fishes, including sharks, guppies, and rockfishes. In viviparous fishes, the young develop within the mothers’ body.

What the Fish? Episode 1: You Are All Fishes!

When most people hear the word fish, they think of Nemo (clownfish), tunas, cichlids, and sharks. Everyone knows what a fish “is”, but why? It turns out that identifying the characteristics that define fishes is a daunting task, and with good reason! Fishes, as we think of them, are actually a paraphyletic or "unnatural" group. When scientists say “fishes”, they are discussing a group of organisms that includes all the descendants from a common ancestor.  So, the correct grouping of fishes includes us, the tetrapods (amphibians, turtles, crocodiles, birds, squamates, mammals, and countless extinct forms).

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