Evolution
Danionella priapus exemplifies the link between the evolution of morphological novelties and progenetic paedomorphosis via heterochronic change in developmental timing. It combines a developmentally-truncated skeleton with highly-modified anatomical structures.
While males of all Danionella species have their anus and genital opening shifted anteriorly between the pelvic fins, the conical projection of the genital papilla of male D. priapus is unique among cypriniforms. The same can be said for the funnel-like formation of the pelvic fins.
In evolutionary terms this might have been achieved by:
- freeing large parts of the anatomical structures from developmental constraints
- dissociating developmentally linked pathways
- creating a greater potential for more dramatic changes
Danionella priapus was recovered as the sister group of the Myanmar species D. translucida and D. mirifica in a molecular analysis in Britz et al. (2009).