Meeting Abstract
The tropics are home to some of the most nuanced examples of ecological specialization: from frogs that raise their young in puddles formed on only certain plants (phytotelmata), to fish species that subsist by parasitizing close relatives, some actively mimicking their sister taxa. The tropics are rife with a myriad of animals that parasitize, clean, compete or prey on co-occurring taxa, be they confamilials, conspecifics, or organisms not closely related at all. What, if anything, do these taxa share in common? This is especially clear in Neotropical freshwater fishes, where a notable number of scale-feeding, fin-feeding, and mucus-feeding taxa occur (and some cleaners too). The best examples of these sorts of behaviors occur in the characiform fishes: tetras, payara, tambaqui, and others – otophysan fishes which comprise the vast majority of freshwater fish diversity worldwide. We examined feeding and body shape morphology among diverse Neotropical characiform ectoparasites with micro-computed tomography scanning in order to answer whether there are any traits in particular that are shared among these particularly belligerent fishes. We find that few characters distinguish ectoparasitic fishes from their confamilials – i.e., it appears rather easy to make an ectoparasite in sheep’s clothing. However, robust teeth and elongate lower jaws may be important for feeding performance, perhaps for leveraging scales and mucus from prey. Some manner of ectoparasitism has evolved at the family-level at least eight times in characiforms, and some four times within characoids alone. We discuss whether these strategies constitute evolutionary ‘dead ends’ and why such specialized niches may not beget specialized morphologies.
