Fig. 5

The evolution and development of danionine feeding mechanics. A. Tracings of two danionine species taken from high-speed videos at ∼80–85% maximum jaw protrusion. They typify two feeding strategies that employ alternative jaw-protrusion techniques and different premaxilla shapes: Devario aequipinnatus (typical of Devario and Microdevario species); Danio erythromicron (typical of Danio species). B. Chronogram showing the relationships and divergence times of the 9 species examined here. Body sizes are relative. The emergence of three feeding strategies associated with differences in jaw protrusion are marked. C. Variation in premaxilla shape among the Danioninae. There is limited variation in ascending arm length (all very short) in the DM clade. Ascending arms are longer in the Danio clade and there is greater length variation. D. Premaxilla development in the Danioninae. The ascending arm elongates during post-metamorphic development in wild-type zebrafish when thyroid hormone (TH) is present. Ascending arms do not elongate in hypothyroid zebrafish (-TH; Galindo et al. 2019). Post-metamorphic ascending arm elongation does not occur in Devario aequipinnatus. E. Mandible elongation in zebrafish mutants with congenitally elevated (+TH) levels. F. Changes in the ratio of premaxilla ascending arm length to dentigerous arm length evolved significantly faster among fishes that use jaw protrusion for suction production (Danio) than among those that use it for prey retention (DM). Changes in the relative timing of maximum jaw protrusion and maximum gape evolved significantly faster among fishes that use jaw protrusion for suction production (Danio) than among those that use it for prey retention (DM).