Variation of organ position in snakes

Abstract

The complex and successful evolutionary history of snakes produced variation in the position and structure of internal organs. Gravity strongly influences hemodynamics, and the impact on structure and function of the cardiovascular system, including pulmonary circulation, is well established. Therefore, we hypothesized that interspecific variation in the position of the heart and vascular (faveolar) lung should exceed that of other internal organs that are less sensitive to gravity. We examined the position of selected internal organs in 72 snakes representing 5 families and 13 species including fully aquatic and scansorial/arboreal species, representing the extremes of gravitational influence. Tests for differences of variance and coefficients of variation largely confirm that interspecific variation in position of the heart and vascular lung generally exceed those of other organs that we measured, particularly posterior organs. The variance of heart position generally exceeded that of more posterior organs, was similar to that of the anterior margin of the vascular lung, and was exceeded by that of the posterior margin of the vascular lung (variance ratio = 0.23).The gravity-sensitive vascular lung exhibited the greatest variation of any organ. Importantly, these findings corroborate previous research demonstrating the influence of gravity on cardiopulmonary morphology. Snakes offer useful model systems to help understand the adaptation of organs to a spectrum of conditions related to diversity of behavior and habitat across a broad range of related taxa. K E Y W O R D S gravity, heart, vascular lung, visceral organs

Gravitational Influence on Human Living Systems and the Evolution of Species on Earth

“…Perez et al (2019) examined the position of specific internal organs in 72 snakes across 13 species. The results corroborated the influence of gravity on the morphology of the cardiopulmonary system, and indicated that the gravity-sensitive vascular lung varied the most among all organs [ 65 ].…”

“…Thus, he suggested that sea snakes are mainly influenced by gravity, considering that they faint with increased gravity, whilst tree snakes are gravity-tolerant. Perez et al (2019) examined the position of specific internal organs in 72 snakes across 13 species. The results corroborated the influence of gravity on the morphology of the cardiopulmonary system, and indicated that the gravity-sensitive vascular lung varied the most among all organs [65].…”

“…Perez et al (2019) examined the position of specific internal organs in 72 snakes across 13 species. The results corroborated the influence of gravity on the morphology of the cardiopulmonary system, and indicated that the gravity-sensitive vascular lung varied the most among all organs [65]. Wright and Turko (2016) attempted to determine whether the plasticity of extant amphibious fishes could indicate the strategies used during the evolution of terrestriality in tetrapods.…”

Body shape and diet reflect arboreality degree of five congeneric snakes sympatric in the Atlantic forest

“…Body size and shape of reptiles and amphibians often reflect adaptation to microhabitats in which they occur (Citadini et al, 2018; Lillywhite, 1996; Lillywhite & Henderson, 1993; Losos, 1990; Martins et al, 2001; Perez et al, 2019). Our results on the five sympatric Chironiu s species reveal a marked variation in body morphology and a strong relationship with substrate use and diet.…”

Water constraints drive allometric patterns in the body shape of tree frogs

“…Other measurements of shape remain largely unexplored. Body shape also influences the distribution of organs involved in the pumping and distribution of blood (e.g., heart and vascular lung) 29 , and interestingly, blood distribution is an important factor in regulating the temperature of ectothermic animals 30 . Additionally, the shape is associated with the rate at which processes such as the diffusion of matter and thermal conduction occurs 17 .…”