This post is the third in a six post series outlining the evolution of mimicry within the ocean realm. These posts detail various ways in which organisms may copy other organisms in appearance and behavior, and the evolutionary context for how these mimic-model pairings have come to be. The first entry in this series goes over some fundamental introductory concepts and definitions regarding mimicry in general.
The previous entry in this series tackled fish that masqueraded as their flippity-floppity boneless distant cousins, generally to keep themselves from getting devoured by one of the endless multitudes of hungry mouths that tirelessly dart back and forth underneath the waves. The entry before that looked at fish that mimic other fish as part of the same evolutionary strategy. It’s worth mentioning that while I really like fish (I study the things, for Christ’s sake), not every bit of mimicry in the ocean involves gills and fins. Plenty of invertebrates (the perhaps less-than-charismatic things like worms and mollusks) in the oceans also engage in mimicry of other species. Sometimes, just like in the last entry, these imitations can jump across to completely different phyla (a major organizational grouping of life right below “kingdom” (like the animal kingdom, Animalia) and above “class” (like Mammalia, which includes mammals within the phylum Chordata)). It’s also important to consider that the phylum to which all vertebrates belong, Chordata, is just one grouping compared to a shitload of so-called “invertebrate” phyla…like thirty of them (the exact number depends on who you talk to…there’s plenty of taxonomic/phylogenetic disagreement to go around). Familiar, cute vertebrate critters like pandas and cats and goldfish and parakeets get a lot of attention, but in reality they make up a tiny sliver of animal diversity. The vast majority of the animal species on planet Earth are “invertebrates”…a commonly thrown out figure is something like 97% of all animals. In light of this, focusing specifically on some gooshy guys for one entry in this series seems only fair. I guess you say I’m…throwing them a bone….or something.
One group of invertebrates that is deserving of focus in the context of marine mimicry are the nudibranchs (pronounced “noo-dee braynks”). Their name means “naked gill”, which refers to their unique respiratory system. While they are regularly referred to as “sea slugs”, nudibranchs represent just one large taxonomic group of marine-living “slug” (the other groups include things like the solar-powered sacoglossans, a member of which is the “sea sheep” that everyone was losing their shit about a month or two ago, or the huge, ink-squirting sea hare, which is part of lineage distinct from nudibranchs). To reduce confusion on what variety of sea slug one is talking about, many folks refer to them by the shorthand “nudis” (pronounced like one would for “nudies”…although taking care to distinguish between things like “nudi photographs” and “nudie photographs” in casual conversation is STRONGLY RECOMMENDED).