Ontogenetic changes in the ventral colouration of post metamorphic Elachistocleis haroi Pereyra, Akmentins, Laufer, Vaira, 2013 (Anura: Microhylidae)

Ontogenetic colour change (OCC) is defined as the
progressive and non-reversible process of changes in colouration of organisms
associated with their development. Among the many vertebrate groups, amphibians
are particularly impressive for their strikingly wide variety of colours, colour
patterns, and signals, whose evolutionary and ecological significance have been
poorly studied. Elachistocleis
comprises 18 species currently separated into two main groups based on their ventral
colour pattern: one immaculate and the other with specks and/or colour patches.
Elachistocleis haroi is a small-sized
species within the immaculate venter group, distributed in the Yungas and Dry
Chaco ecoregions from which little information is known. In a comprehensive
sampling of post-metamorphic individuals of E.
haroi at different stages of development we identified a significant in ventral
colour pattern, which could denote a progressive filling of yellow colour according
to an ontogenetic pattern. To test this hypothesis, we analysed 39 post-metamorphic
individuals of E. haroi at different
stages of development with imaging procedures. We found that yellow spots and
their intensity are significantly related to snout-vent length, as major expansion
of colour on the sides, gular region and male chest, as almost no development on
the belly. We briefly discuss our findings in relation to sexual display and
predation avoidance. To our knowledge, this is the first analysis of
post-metamorphic OCC in ventral colouration in the genus Elachistocleis.