Mating System and Parental Care in the the Cuatro Ciénegas Cichlid, Herichthys minckleyi

The >100 species of North American cichlids are unusual among fishes in that a male and a female form a monogamous pair-bond and cooperate to care for their offspring. Oddly, previous studies suggested that the Cuatro Ciénegas cichlid, Herichthys minckleyi, is polygynous. We performed a phylogenetic analysis and found that H. minckleyi occurs in a clade of sexually monochromatic monogamous species, but that male and female H. minckleyi have different reproductive color patterns, likely due to sexual selection. Additionally, we found that large males guard very large territories and smaller males may attempt alternative mating tactics (sneaking). Furthermore, compared to the monogamous Rio Grande cichlid, H. cyanoguttatus, male H. minckleyi were present at their nests less often and performed lower rates of aggressive offspring defense, and females compensated for the absence of their mates by performing more offspring defense. Finally, in reproductive males we found higher levels of neural V1a2 and PRLR1 mRNA, and plasma 11-ketotestosterone in H. minckleyi than in H. cyanoguttatus. Body color, mating system, parental care, and neuroendocrine mechanisms in H. minckleyi appear to have evolved after it colonized Cuatro Ciénegas, and are likely a result of the isolated, stable environment there.