Introducing the other species of peacock bass

You may have gathered that our two stars for this black/whitewater project, the butterfly peacock bass, Cichla orinocensis, and yellow peacock bass, Cichla monoculus, are not the only species of peacock bass. In fact, according to taxonomists there are 15 species, although my molecular work has suggested only 8. Anyway, I figured I would introduce them so you would know what you were missing.

There are several other species closely related to the yellow peacock, C. monoculus, which collectively make up what I have called Cichla ocellaris sensu lato. They are C. ocellaris, C. monoculus, C. nigromaculata, C. kelberi, and C. pleiozona. Though they have been described as full species, my work suggests that they are actually intra-specific units, something like sub-species or evolutionarily significant units. But they have not yet been formally sunk, which is why I say C. ocellaris sensu lato. "Sensu lato" is a latin expression that means 'in the broad sense'. As C. ocellaris was the first of these species to be described, that's why we use this name to all of them. Aside from being fairly difficult to identify them just by looking at them without knowing where they came from, they exhibit a couple of other characteristics that make them seem more like just differentiated populations of a single species rather than different species. First, they are all allopatric, meaning that they don't overlap in their geographic distributions. "Good" species will often overlap extensively with little or no hybridization. Second,  where they are found in proximity, that is, where their ranges are contiguous, they generally exchange genes freely, much as subpopulations of any species would. So while these fishes may show some characteristics that make them unique, it does not appear to make them equivalent to separate species. They are distributed over much of northern South America, but are notably absent from the Orinoco River basin in the north except for the very southern end just outside of where the Casiquiare River connects the Orinoco to the Amazonas. They are smaller species that tend to occupy more shallow habitats and prefer slower moving waters like lagoons. You know C. monoculus looks like (see my other lab note). Here's the others:

Cichla ocellaris (which is also called the 'butterfly' peacock bass by some)

 

Cichla nigromaculata

 

Cichla pleiozona

 

Cichla kelberi

 

Unlike the yellow peacock (C. monoculus), the butterfly peacock (Cichla orinocensis) only has one species to which it is closely related (although C. orincensis and its sister C. intermedia are more closely related to the C. ocellaris group than to the other peacocks you'll meet below; you can see that in our latest phylogeny paper, here). Cichla intermedia is only found in the Orinoco basin except for its distribution in the Casiquiare River itself (and its small tributaries); it is otherwise not found in the Amazon. This is probably another species that has not been able to make the transition into the extreme blackwaters that lie in the Negro, between the Orinoco and the broader Amazon. While C. orinocensis likes slow waters much like the C. ocellaris types, C. intermedia is a faster water fish, preferring to live around structure like rocks in moving water. Here's what it looks like:

 

The most famous of all the peacock bass is probably Cichla temensis, the barred (tucunaré açu) or spotted (tucunaré paca) peacock. It is the largest of the peacock bass, and, with reports of over a meter long, the largest cichlid fish in the world. This large and aggressive fish is targeted by a large recreational fishery in the Negro River basin in Brazil. One of the most interesting things about this fish is that fish that are ready to spawn or protecting young have very different color patterns (like I mentioned in the lab note about yellow peacocks). These color patterns are so different that they have been speculated to be different species. However, my collaborator Paul Reiss coordinated a nice study that showed that not only are they the same species, but that it is a seasonal difference that correlates strongly with the fish's readiness to reproduce. Unlike the yellow peacock C. monoculus, though, it appears that individual fish cycle through versions of each color pattern over the course of the year, rather than retaining the "mature" pattern once they reach a certain age. Here's what those two patterns look like:

This is the reproductive barred or "açu" pattern

 

And here is the non-reproductive spotted or "paca" pattern

 

There is a cadre of species closely related to Cichla temensis, most of them confined to various tributaries of the Amazon River. Three species are confined to the southern tributaries, and are easily distinguishable from each other and other species of peacock bass. In the Tapajós, Xingu, and Tocantins Rivers they are:

Cichla mirianae

 

Cichla melaniae

 

Cichla piquiti. This species is often called "tucunaré azul" or 'blue peacock' because adults have bluish fins

 

The remaining 4 described species of peacock bass, Cichla pinima, C. thyrorus, C. vazzoleri, C. jariina, are, like the C. ocellaris group, largely too similar to be easily distinguished. Moreover, I found that they were too closely related genetically to be considered "good" biological species, so I generally refer to these all as Cichla pinima sensu lato. While C. pinima is widespread in the Amazon River downstream of the Negro (and in Brazilian shield tributaries of the Madeira River), the other three species are allegedly resigned to northern tributaries of the Amazon: C. jariina in the Jari River, C. vazzoleri in the lower Trombetas and upper Uatumã, and C. thyrorus in the upper Trombetas. Good luck telling them apart though!

C. pinima

 

C. thyrorus

 

C. jariina

 

C. vazzoleri

 

This is all of the described species of peacock bass, and even though our work has suggested there are perhaps fewer "good" species than what are actually described, there are still many more populations to be discovered and interesting phenomena to be described. Peacock bass show lots of unique patterns that lend themselves well to analyses than can provide insight into adaptation and diversification. For example, the Cichla intermedia on the Caura River that show exaggerated nuchal humps. Perhaps runaway sexual selection? I can't wait!