Fig. 7

An evolutionary hypothesis regarding the sequence in which developmental variation evolved in ceratophryid lineage with consequences in the suppression of metamorphosis of the gastrointestinal tract in Lepidobatrachus studied herein. The phylogenetic relationships were based on molecular data for the whole clade [43]. In comparisons with other frogs, development in extant ceratophryids have accelerated rates of differentiation and growth as larvae which may be influenced by TH signals [13, 15]. Data from the thyroid gland’s histomorphology during larval development indicate however that ceratophryids have low secretory activity at early larval stages suggesting that maternal nutrients and/or diet are possible sources for TH precursors for precocious development [31]. Developmental plasticity led to three larval eco-morphotypes that may breeding simultaneously in the same pond. There is a distinct metamorphosis from the larval to adult gastrointestinal tract in the carnivore tadpole of Ceratophrys and the omnivore tadpole of Chacophrys similar to what occurs in most anurans. In Lepidobatrachus, in contrast, the larval gastrointestinal tract is quite similar to that of the adult without abrupt stomach differentiation and intestine shortening at metamorphosis. Furthermore, diet and feeding behavior in larval and adult stages are similar