Embryonic development of the pharyngeal region in thamnophis radix

Abstract

Considerable work has been done on the general morphology and derivatives of the pharyngeal pouches in Reptilia. Since, however, such investigators as van Bemmelen ( '86), de Meuron ( '98), Bfauer ( '99), Prenant ( '04), and Saint-Remy ('04) have not agreed upon the embryonic topography of the reptilian pharynx, it has seemed justifiable to review the development of this region in reptiles.This investigation deals with various stages in the development of the pharyngeal region of the garter snake, Thamnophis radix (Baird and Girard), in which special attention has been given to the relative positions of the pharyngeal pouches and their derivatives, the thyroid, and the respiratory anlage.The material used was collected by Theodore Byerly and the senior author at the Fresh Water Biological Laboratory of the State University of Iowa, Lake Okoboji, 1923. Serial sections of one full-term specimen and five different embryonic stages were made. The lengths of the embryos were: 4 mm., crown-rump; 15 mm., 35 mm., 50 mm., and 80 mm. measured from crown to tip of tail.Wax models of the pharynx and its derivatives of the 4-mm.and 15-mm. embryos were constructed according to the method described by Harrison ( '24).

Heterochrony and Early Left-Right Asymmetry in the Development of the Cardiorespiratory System of Snakes

“…[18] – [23] ). Similar findings were found in the Plains garter snake Thamnophis radix Baird and Girard, 1853 (family Colubridae) [24] , which has an adult pulmonary anatomy similar to that of Natrix natrix (see also Ref. [12] for a review).…”

“…13B ) shows that the left lung is shorter than the right lung. Since already at this early stage the two lungs in this species are subequal, our data are most easily explained, in view of previous studies in Thamnophis radix and Natrix natrix [15] , [24] , by assuming that the left lung has a lower growth rate than the right lung, as opposed to truncation at a later stage of development. It is important to note that availability of this rare embryonic material is limited, and so it was not possible to make any quantitative determination of growth rates.…”

Morphology and physiological significance of parathyroid glands in reptilia

“…Harrison and Denning (1929) found four glands in adult Thamnophis radix but ten glands in embryos of this species. Huckel (1932) and Herdson (1956;cited by Clark, 1970) identified two pairs of parathyroid glands in seven species of snakes from three families: Colubridae (Carphophis amoenus uermis, Dryophis prasinus, Natrix natrix, Oligodon octolineatus, Thamnophis sp.…”

“…Epithelial proliferations from all five visceral pouches have been noticed (Greep, 1963;Harrison and Denning, 1929;Saint Remy and Prenant, 1904;Van Bemmelen, 1888). In Thamnophis radix, Harrison and Denning (1929) established that in this species the parathyroids derive from the fourth and fifth pouches (Greep, 1963). The development of the Ophidian parathyroids needs to be worked out.…”