Lizard Development

From Embryology

Introduction

Australian water skink embryo

Lizards and snakes represent scaled reptiles (squamata).

Some Recent Findings

  • Patterns of interspecific variation in the heart rates of embryonic reptiles[1] "New non-invasive technologies allow direct measurement of heart rates (and thus, developmental rates) of embryos. We applied these methods to a diverse array of oviparous reptiles (24 species of lizards, 18 snakes, 11 turtles, 1 crocodilian), to identify general influences on cardiac rates during embryogenesis. Heart rates increased with ambient temperature in all lineages, but (at the same temperature) were faster in lizards and turtles than in snakes and crocodilians. We analysed these data within a phylogenetic framework. Embryonic heart rates were faster in species with smaller adult sizes, smaller egg sizes, and shorter incubation periods. Phylogenetic changes in heart rates were negatively correlated with concurrent changes in adult body mass and residual incubation period among the lizards, snakes (especially within pythons) and crocodilians. The total number of embryonic heart beats between oviposition and hatching was lower in squamates than in turtles or the crocodilian. Within squamates, embryonic iguanians and gekkonids required more heartbeats to complete development than did embryos of the other squamate families that we tested. These differences plausibly reflect phylogenetic divergence in the proportion of embryogenesis completed before versus after laying."
  • Reptilian spermatogenesis: A histological and ultrastructural perspective[2] "Until recently, the histology and ultrastructural events of spermatogenesis in reptiles were relatively unknown. Most of the available morphological information focuses on specific stages of spermatogenesis, spermiogenesis, and/or of the mature spermatozoa. No study to date has provided complete ultrastructural information on the early events of spermatogenesis, proliferation and meiosis in class Reptilia. Furthermore, no comprehensive data set exists that describes the ultrastructure of the entire ontogenic progression of germ cells through the phases of reptilian spermatogenesis (mitosis, meiosis and spermiogenesis). The purpose of this review is to provide an ultrastructural and histological atlas of spermatogenesis in reptiles. The morphological details provided here are the first of their kind and can hopefully provide histological information on spermatogenesis that can be compared to that already known for anamniotes (fish and amphibians), birds and mammals. The data supplied in this review will provide a basic model that can be utilized for the study of sperm development in other reptiles. The use of such an atlas will hopefully stimulate more interest in collecting histological and ultrastructural data sets on spermatogenesis that may play important roles in future nontraditional phylogenetic analyses and histopathological studies in reptiles."

Taxon

root; cellular organisms; Eukaryota; Opisthokonta; Metazoa; Eumetazoa; Bilateria; Coelomata; Deuterostomia; Chordata; Craniata; Vertebrata; Gnathostomata; Teleostomi; Euteleostomi; Sarcopterygii; Tetrapoda; Amniota; Sauropsida; Sauria; Lepidosauria

Links: Taxonomy Browser Lizards

Development Overview

Genome

Historic

Fig. 343. Head of a Lizard Embryo (Sphenodon punctatum Hatteria)

Schwalbe (1891), discusses the Darwin tubercle (i. e., the true ear-tip) as it occurs in adult man. He describes six degrees of its occurrence, varying from the most pronounced type, resembling the Macacus form, to the least marked, where no trace of the ear-tip can be recognized. He explains the increase in ear dimensions, occurring with advancing age, as due to the flattening out of the various folds of the auricle. This he regards as connected with the loss of elasticity of the elastic fibers of the skin and cartilage, and as related to the wrinkling of the skin which accompanies loss of elasticity in the aged.

(From Contributions to Embryology No.69)

References

  1. <pubmed>22174948</pubmed>
  2. <pubmed>22319673</pubmed>

Reviews

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Articles

<pubmed>19645023</pubmed> <pubmed>19097047</pubmed> <pubmed>17415759</pubmed> <pubmed>15521466</pubmed> <pubmed>5437480</pubmed> <pubmed>6429113</pubmed>

Books

Search PubMed

Search PubMed: Lizard development

External Links

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Cite this page: Hill, M.A. (2021, July 27) Embryology Lizard Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Lizard_Development

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© Dr Mark Hill 2021, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G