The Evolution Facebook page shared the interesting example of parasite behavior I am quoting in full below. The photo may give you nightmares. The question I want to ask is what young-earth creationists and others who reject evolution say about such organisms. Do they envisage God creating these parasites specifically to do the things that they do? And if so, why? I expect that I am not alone in finding evolution to give not merely the best scientific explanation, but also an account that is theologically preferable to one that envisages God creating creatures directly to survive and reproduce in these specific ways. Read the information below, and then please share your thoughts on this!
Cat got your tongue, or is it Cymothoa exigua?
Parasites often alter their host's behaviour or appearance, but Cymothoa exigua goes one further – it is the only parasite known to replace an entire organ. Its unfortunate host is typically the rose spotted snapper, which it enters through the gills and lodges itself at the back of the mouth. It hooks its claws at the base of the tongue and interrupts the blood flow, consuming it instead. Due to the lack of blood the tongue atrophies and falls off, whereupon the isopod parasite attaches itself to the remaining stub. It then “becomes” a functional tongue for the fish, able to be moved as the fish would have moved its original tongue.
Like most cymothoid isopods, C. exigua is a hermaphrodite. In one study females were only found in the mouth, whereas males could be found in the gills and the mouth (and in the mouth they were clinging to females, suggesting copulation). A small proportion of extremely unlucky fish were found with females as the tongue and males simultaneously occupying the gills. Despite the “organ-replacement” part, it doesn't appear C. exigua has other adverse effects on the fish.In case you were wondering (and we're sure it crossed your mind at some point), C. exigua does not affect humans. That said, don't pick one up – they deliver quite a nip.Photo credit: Dr. Nico Smit.