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I just read that one of the differences between sexes in H. acipenserinus is that the males have a spoon-shaped crow and the females' crow is pointed. Can someone explain to me what a crow is in this context?

I suspect that's supposed to be "crown" instead of "crow." See this article, Figure 13a-b show spoon-shaped male teeth, Figure 13c-d show pointed female teeth.

The citation is:
Isbrücker, I. J. H., & Nijssen, H. (1974). On Hemiodontichthys acipenserinus and Reganella depressa, two remarkable mailed catfishes from South America (Pisces, Siluriformes, Loricariidae). Beaufortia, 22(294), 193-222.

If crow is intentional, I have no idea, but I've never heard of the tips of teeth being called crows before.

Cheers, Eric

Just found another article (http://www.academia.edu/download/332137 ... 62p040.pdf) that says crown. Note, this latter paper mentions tooth crowns in , not , but the point is simply that the paper says the tooth "crowns" (not tooth crows) are sexually dimorphic in the group; apparently Loricaria also have similar differences - more rounded teeth in males vs. more pointed teeth in females.

Here is the citation: Covain, R., & Fisch-Muller, S. (2007). The genera of the Neotropical armored catfish subfamily Loricariinae (Siluriformes: Loricariidae): a practical key and synopsis. Zootaxa, 1462, 1-40.

Thanks Bekateen

I can think of a couple of evolutionary reasons for this type of differentiation, but hadn't seen this before now. I'm curious if there has been any work done intentionally comparing gut analysis of the sexes of any of the species in this group.

There are more species where males and females are adapted not to outcompete each others, but this is rather extreme.

Cheetah, for instance see males living with a few intead of solitary resulting in the ability to take larger prey. Birds of prey have larger females, again aiming for larger prey than males do.

But a complete different set of teeth - it does help, basically it enables 1 species to life in 2 nices, making it possible to have twice the amount of fishes than living in 1 nice, but how would something like this have evolved?

I'm thinking this may very well be more specific than just diet, but wanted to see more information before making assumptions. I don't want to make any statements which may be misconstrued or provide false basis, but I find it VERY interesting that the species/genera mentioned in the articles posted so far "happen" to be lip brooders. I'm thinking this may have something to do with the method of caring for the developing eggs, potentially regarding carrying the brood, but would like to see something more concrete than my own conjecture based off nothing more than a simple observation.