Written 2023–11–05, slightly drunk
I recently read about the sexual behaviour of certain species of anglerfish. In these species, there is a unusual level of sexual dimorphism. That is, the male and female of the species are physically very different. We see sexual dimorphism in many species, including Homo Sapiens. An alien coming to our planet would probably be able to cluster a large portion of our population into two distinct groups based on physiological characteristics, even without seeing genitalia.
However, this is not about humans; it’s about anglerfish. In the aforementioned anglerfish species, the female is vastly larger and more developed than the male. The female comprises what we may typically think of when we think of anglerfish: large teeth, a cavernous mouth and an expandable stomach to match, and a fluorescent “lure” hanging in front of the mouth, used to attract prey. In contrast, the male is little more than olfactory organs and gonads attached to some fins that allow them to follow their sense of smell. The males of these species may not even have a fully-developed digestive system. Their whole existence is geared towards seeking out a female and then reproducing.
You may think it a wonder that these fish still exist. Swimming around in the blackness of the abyss, barely able to survive on their own. If they do happen to find a female, there’s no guarantee that they are ready to mate. Instead, the males of these species latch onto the female and burrow into their skin. In time, the female’s body grows new blood vessels to provide the male with oxygen and nutrients. When it comes time to reproduce, there’s no need to go looking for a mate. The female already has one (or more) attached to her.
This only works because these particular species have their immune response massively suppressed. If, say, a human tried to graft themself to another human, their individual immune systems would each spring to action trying to fight off the other’s cells. This is a pretty extreme feature to be missing in a complex animal. These two fascinating characteristics are thought to have come about as they are advantageous in an environment where locating any mate at all is difficult. Delightful!
I’m not a biologist, but I do spend plenty of time browsing information about interesting organisms. Please do write in and tell me how I’m wrong and give me more interesting things to read.