Variations in lateral band and caudal spot

[Ttw]

I have been trying to identify some of the fish I collected in Bolivia. The confusion started in trying to differentiate A. inconspicua from A. linkei. They are closely related. One of the main identifiers to differentiate between the two is the relationship of the lateral band to the caudal spot. Inconspicua's lateral band does not extend into the caudal spot where as linkei's does. The problem I have seen is that on my F1 juveniles in the same batch some of the lateral bands connect to the caudal spot and some do not. Unless this does not remain in the adults, this throws into question the validity of this as an identifier.

 

[gerald]

That problem happens a LOT with species descriptions when the authors don't have a large enough sample size to make a good comparison. They end up describing particular differences between individual fish (which may or may not be different species), rather than consistent differences between populations. A related problem is when the authors are working only from preserved specimens and aren't familiar with the variability in living fish. The break between the lateral band and caudal spot might "work" as a distinguishing feature in formalin-preserved fish but not in live ones. GOOD species descriptions rely on LARGE sample sizes of the new species AND its close relatives, preferably using specimens from different sites across the species' ranges, and both live and preserved specimens.

 

[Mike Wise]

Tom, I think the problem might be that you are viewing different specimens in different moods. Live apistos can change their color pattern depending on mood. Dead fish can't. Color also depends on how the fish were preserved. If I remember correctly, fish 'fixed' in formalin and then preserved in ethanol (old method) tends to preserve more color, while preserving in ethanol without fixing (modern method to preserve DNA) tends to bleach out colors. For your purpose, I think the use of dorsal spine count would work better - 15 for A. linkei & 16 for A. inconspicua. A. linkei is a deeper-bodied fish compared to A. inconspicua and has more prominent abdominal stripes:

(from Koslowski, 1985)

Gerald, I agree this happened often, mostly in older description, but not in this case. When Koslowski described A. linkei he had access to 28 preserved specimens plus a number of live fish. He used museum specimens of A. inconspicua and live imports for comparison material.

 

[Ttw]

I keep reading about the distinct vertical abdominal stripes in linkei but have not seen any pictures of these in any of my apisto books (Koslowski, Romer Staeck and Linke, Mayland, Bork). Perhaps these are in preserved specimans.

 

[Mike Wise]

I think that you expect a solid vertical abdominal stripe, but it's not. It's a series of black borders on rows of scales that form a more vertical than diagonal 'streak' that is fairly thin, like what's seen on resticulosa-complex species (they are closely related complexes). In the DATZ book both the male and female A-99 show these.

 

[Ttw]

Ok, looking at the pictures of linkei in the Datz book I see what you are talking about. Not easy to see for "distinct" stripes.