Juszczyk et al. (1966) studied the seasonal fluctuation in gut mass and histology (the anatomy of the stomach and intestinal mucosa) in five age groups and both sexes of Rana temporaria. The study's main findings are as follows: a) individuals have marked seasonal variation in gut development, which is correlated to the annual feeding cycle; b) female gut attains a much greater mass than male gut during the period of high feeding activity; c) the beginning of gut regression in the middle of terrestrial life (i.e. the active period) suggests endogenous control of gut changes. Naya et al. (2003b) assessed seasonal variation in the intestine length of the South American common frog based on this previous work (Leptodactylus ocellatus). Their findings not only confirmed the occurrence of seasonal variations in eating and reproductive activities but also revealed a considerable sex influence. Indeed, in men, intestinal length flexibility appears to be linked to the yearly eating cycle, but in females, it appears to be primarily linked to the reproductive cycle. Furthermore, females' seasonal fluctuations in stomach length were more noticeable than men's.

The tongue has been employed as a "taxonomic trait" in the categorization of frogs since the 19th century and continues to be used today (d. Lynch, 1973). Amphibians are notable for having a tongue that is propelled from the mouth to impact on, adhere to, and pull prey into the buccal cavity. Although this is sometimes listed as a defining feature of the class, the tongue appears to be flipped out rather than moved incrementally only in certain salamanders and frogs. Its movement is therefore similar to that of chameleons' projectile tongue, rather than anteaters', birds', and snakes' just extendable tongue. Frog tongues are propelled anteriorly by a forward shift of the hyobranchial skeleton, whereas salamander tongues are propelled anteriorly by rotation of "soft" tissues around the mandibular symphysis (Regal, 1966; Ozeti and Wake, 1969; Lombard and Wake, 1976; Larson and Guthrie, 1976).

Plethodontid salamanders catch their prey by extending their tongue from their mouth. To construct a working theory for tongue motions, researchers looked at the theoretical mechanics of the hyobranchial skeleton. Salamanders protrude their tongue when beheaded in a certain way, and it does not retract. Examining these heads after they've been repaired and sectioned verifies the predictions. These findings are then utilized to fine-tune the working hypothesis and develop a generic model of plethodontid tongue dynamics. The primary projection (subarcualis rectus I) and retraction (rectus cervicis profundus) muscles have been found. The skeleton is folded inactively along a tractrix-shaped morphological pathway. The geometry of the track and the precise layout of the folded skeleton are validated by sectioned material analysis. During retraction, the skeleton unfolds along the track and spreads into the resting condition. The model established here will be utilized as a foundation for making predictions about family selection patterns and for analyzing comparative and evolutionary research.

Soares D, Adams R, Hammond S, Slay ME, Fenolio DB, Niemiller ML (2017) Evolution of Coprophagy and Nutrient Absorption in a Cave Salamander. Subterranean Biology 24: 1-9. https://doi.org/10.3897/subtbiol.24.15013

Lombard, R. E., & Wake, D. B. (1976). Tongue evolution in the lungless salamanders, family plethodontidae I. Introduction, theory and a general model of dynamics. Journal of Morphology, 148(3), 265–286. doi:10.1002/jmor.1051480302

Rebouças, R., & Solé, M. (2015). Diet ofAdenomera thomei(Almeida and Angulo, 2006) (Anura: Leptodactylidae) from a rubber tree plantation in southern Bahia, Brazil. Studies on Neotropical Fauna and Environment, 50(2), 73–79. https://doi.org/10.1080/01650521.2015.1048613

Secor, S. M. (2005). Evolutionary and Cellular Mechanisms Regulating Intestinal Performance of Amphibians and Reptiles. Integrative and Comparative Biology, 45(2), 282–294. https://doi.org/10.1093/icb/45.2.282

NAYA, D. E., & BOZINOVIC, F. (2004). Digestive Phenotypic Flexibility in Post-Metamorphic Amphibians: Studies on a Model Organism. Biological Research, 37(3). https://doi.org/10.4067/s0716-97602004000300002

Regal, P. J., & Gans, C. (1976). Functional Aspects of the Evolution of Frog Tongues. Evolution, 30(4), 718. https://doi.org/10.2307/2407812