Post-Hatching Development of the Tongue in Egyptian Fayoumi Chickens (<i>Gallus g. domesticus</i>): New Emphasis on Age-Relational Through Scanning Electron Microscopy, Histological, and Histochemical Techniques

The present study was the first attempt to describe age-related morphological lingual characterizations of Egyptian Fayoumi chickens at three post-hatching stages (1-day-old, 2-month-old, and 6-month-old) using SEM, histological, and histochemical techniques. There were characteristic features for each age. The papillary crest shape changed as the chickens aged: an arc-shaped crest in 1-day-olds, a "V" shape in 2-month-olds, and a serpentine pattern in 6-month-old chickens. The glottis was bordered by a papillary border in 1-day-old and by rostral nonpapillary and papillary portions in 2- and 6-month-olds. The apex and body carried fork-shaped filiform papillae in 1-day-olds; it had long, thick-branched papillae on the lateral tip region; the apex carried thin-branched papillae in 2-month-olds; and it had thick, long papillae in 6-month-old chickens. The rostral apical part was surrounded by membranes, two or three in 1-day-olds, four to five in 2-month-olds, and six to seven in 6-month-old chickens. These glands were located only in the free tongue and the root's second half. Histochemically, all ages had positive PAS and AB reactions, with moderate reactivity in the anterior and strong reactivity in the posterior part. Collagen fibers were seen within the connective tissue core, and glandular acini varied among ages: lower in 1-day-old, moderate in 2-month-old, and abundant in 6-month-old chickens. In conclusion, the tongue evolved to strongly adapt to the food particles available at each age stage.