scholarly journals A novel accessory respiratory muscle in the American alligator ( Alligator mississippiensis )

2019 ◽  
Vol 15 (7) ◽  
pp. 20190354 ◽  
Author(s):  
Jonathan R. Codd ◽  
Kayleigh A. R. Rose ◽  
Peter G. Tickle ◽  
William I. Sellers ◽  
Robert J. Brocklehurst ◽  
...  
Keyword(s):  
Respiratory Function ◽  
Respiratory Activity ◽  
Lung Ventilation ◽  
Alligator Mississippiensis ◽  
Evolutionary Constraints ◽  
Breathing Frequency ◽  
American Alligator ◽  
Form And Function ◽  
Distress Vocalizations ◽  
And Function

The muscles that effect lung ventilation are key to understanding the evolutionary constraints on animal form and function. Here, through electromyography, we demonstrate a newly discovered respiratory function for the iliocostalis muscle in the American alligator ( Alligator mississippiensis ). The iliocostalis is active during expiration when breathing on land at 28°C and this activity is mediated through the uncinate processes on the vertebral ribs. There was also an increase in muscle activity during the forced expirations of alarm distress vocalizations. Interestingly, we did not find any respiratory activity in the iliocostalis when the alligators were breathing with their body submerged in water at 18°C, which resulted in a reduced breathing frequency. The iliocostalis is an accessory breathing muscle that alligators are able to recruit in to assist expiration under certain conditions.

scholarly journals Rib kinematics during lung ventilation in the American alligator (Alligator mississippiensis): an XROMM analysis

2017 ◽  
Vol 220 (17) ◽  
pp. 3181-3190 ◽  
Author(s):  
Robert J. Brocklehurst ◽  
Sabine Moritz ◽  
Jonathan Codd ◽  
William I. Sellers ◽  
Elizabeth L. Brainerd
Keyword(s):  
Lung Ventilation ◽  
Alligator Mississippiensis ◽  
American Alligator

Pelvic aspiration in the American alligator (Alligator mississippiensis)

2000 ◽  
Vol 203 (11) ◽  
pp. 1679-1687 ◽  
Author(s):  
C.G. Farmer ◽  
D.R. Carrier
Keyword(s):  
Electrical Activity ◽  
Lung Ventilation ◽  
Rectus Abdominis ◽  
Transversus Abdominis ◽  
Alligator Mississippiensis ◽  
Abdominal Pressure ◽  
American Alligator ◽  
Diaphragmatic Breathing ◽  
Pelvic Muscles

The pelvis of crocodilians is highly derived in that the pubic bones are isolated from the acetabulum and are attached to the ischia via moveable joints. We examined the possible role of this unusual morphology in lung ventilation by measuring ventilation, abdominal pressure and the electrical activity of several abdominal and pelvic muscles in the American alligator (Alligator mississippiensis). We found that the activity of two pelvic muscles, the ischiopubis and ischiotruncus muscles, was correlated with inspiration; these muscles rotate the pubes ventrally and thereby increase abdominal volume. During expiration, contraction of the rectus abdominis and transversus abdominis rotates the pubes dorsally. We suggest that this mechanism facilitates diaphragmatic breathing by creating space for caudal displacement of the viscera during inspiration. Because birds also use a dorso-ventral movement of the pelvis to effect ventilation, some form of pelvic aspiration may be plesiomorphic for archosaurs.

scholarly journals Respiratory evolution in archosaurs

2020 ◽  
Vol 375 (1793) ◽  
pp. 20190140 ◽  
Author(s):  
Robert J. Brocklehurst ◽  
Emma R. Schachner ◽  
Jonathan R. Codd ◽  
William I. Sellers
Keyword(s):  
Respiratory Function ◽  
Respiratory Physiology ◽  
Theme Issue ◽  
Form And Function ◽  
Lung Structure ◽  
Successful Group ◽  
Avian Lung ◽  
And Function ◽  
Key Events ◽  
Metabolic Strategies

The Archosauria are a highly successful group of vertebrates, and their evolution is marked by the appearance of diverse respiratory and metabolic strategies. This review examines respiratory function in living and fossil archosaurs, focusing on the anatomy and biomechanics of the respiratory system, and their physiological consequences. The first archosaurs shared a heterogeneously partitioned parabronchial lung with unidirectional air flow; from this common ancestral lung morphology, we trace the diverging respiratory designs of bird- and crocodilian-line archosaurs. We review the latest evidence of osteological correlates for lung structure and the presence and distribution of accessory air sacs, with a focus on the evolution of the avian lung-air sac system and the functional separation of gas exchange and ventilation. In addition, we discuss the evolution of ventilation mechanics across archosaurs, citing new biomechanical data from extant taxa and how this informs our reconstructions of fossils. This improved understanding of respiratory form and function should help to reconstruct key physiological parameters in fossil taxa. We highlight key events in archosaur evolution where respiratory physiology likely played a major role, such as their radiation at a time of relative hypoxia following the Permo-Triassic mass extinction, and their evolution of elevated metabolic rates. This article is part of the theme issue ‘Vertebrate palaeophysiology’.

scholarly journals Does morphological convergence imply functional similarity? A test using the evolution of quadrupedalism in ornithischian dinosaurs

2012 ◽  
Vol 279 (1743) ◽  
pp. 3765-3771 ◽  
Author(s):  
Susannah C. R. Maidment ◽  
Paul M. Barrett
Keyword(s):  
Fossil Record ◽  
Soft Tissues ◽  
Functional Similarity ◽  
Developmental Pathways ◽  
Evolutionary Constraints ◽  
Skeletal Morphology ◽  
Functional Studies ◽  
Form And Function ◽  
Morphological Convergence ◽  
And Function

Convergent morphologies are thought to indicate functional similarity, arising because of a limited number of evolutionary or developmental pathways. Extant taxa displaying convergent morphologies are used as analogues to assess function in extinct taxa with similar characteristics. However, functional studies of extant taxa have shown that functional similarity can arise from differing morphologies, calling into question the paradigm that form and function are closely related. We test the hypothesis that convergent skeletal morphology indicates functional similarity in the fossil record using ornithischian dinosaurs. The rare transition from bipedality to quadrupedality occurred at least three times independently in this clade, resulting in a suite of convergent osteological characteristics. We use homology rather than analogy to provide an independent line of evidence about function, reconstructing soft tissues using the extant phylogenetic bracket and applying biomechanical concepts to produce qualitative assessments of muscle leverage. We also optimize character changes to investigate the sequence of character acquisition. Different lineages of quadrupedal ornithischian dinosaur stood and walked differently from each other, falsifying the hypothesis that osteological convergence indicates functional similarity. The acquisition of features correlated with quadrupedalism generally occurs in the same order in each clade, suggesting underlying developmental mechanisms that act as evolutionary constraints.

Scanning tunneling microscopy (STM) of DNA and RNA

1989 ◽  
Vol 47 ◽  
pp. 34-35
Author(s):  
Patricia G. Arscott ◽  
Gil Lee ◽  
Victor A. Bloomfield ◽  
D. Fennell Evans
Keyword(s):  
Molecular Structures ◽  
Inorganic Materials ◽  
Resolving Power ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Form And Function ◽  
Dna And Rna ◽  
Calf Thymus ◽  
And Function ◽  
The Relationship

STM is one of the most promising techniques available for visualizing the fine details of biomolecular structure. It has been used to map the surface topography of inorganic materials in atomic dimensions, and thus has the resolving power not only to determine the conformation of small molecules but to distinguish site-specific features within a molecule. That level of detail is of critical importance in understanding the relationship between form and function in biological systems. The size, shape, and accessibility of molecular structures can be determined much more accurately by STM than by electron microscopy since no staining, shadowing or labeling with heavy metals is required, and there is no exposure to damaging radiation by electrons. Crystallography and most other physical techniques do not give information about individual molecules.We have obtained striking images of DNA and RNA, using calf thymus DNA and two synthetic polynucleotides, poly(dG-me5dC)·poly(dG-me5dC) and poly(rA)·poly(rU).

Sign in / Sign up

Export Citation Format

Share Document