Autotomy and Regeneration in Squamate Reptiles (Squamata, Reptilia): Defensive Behavior Strategies and Morphological Characteristics (Using Computer Microtomography Methods)

Abstract

It has been noted that caudal autotomy as a way of defending against predators in recent reptiles is characteristic solely of lepidosaurs and is absent in crocodiles and turtles. It was found that, in the order Rhynchocephalia and in representatives of the majority of families of lizards, intravertebral (IntraVB) autotomy is a widespread phenomenon, whereas agamid lizards and some snakes do not have a break plane, and their tails break between adjacent vertebrae (intervertebral (InterVB) autotomy). The frequencies of occurrence of InterVB autotomy and regeneration in six species of agamas of the genus Paralaudakia were analyzed. Six types of regenerate’s characteristic of the studied group and the anatomical structure of the knob -shaped jagged regenerate are described on the basis of the results of computed microtomography (micro-CT). Phenomena of autotomy and regeneration are discussed in the phylogenetic context.

The Review of the Autotomy of Agamid Lizards with Considerations about the Types of Autotomy and Regeneration

“…Laudakia nupta A+R+ [5,20], (Figure A1h and Figure S7h) Laudakia tuberculata A+R+ [5,24], (Figure A1i A+R- [5,6] Thus, the subfamilies Uromastycinae and, probably, Hydrosaurinae, contain nonautotomic species, and Leiolepidinae include lizards capable of pseudoautotomy and regeneration. Agaminae, Draconinae and Amphibolurinae include species with all combinations of pseudoautotomy and regeneration.…”

“…The Agamidae family is remarkable in that it includes species forming the regenerates of unusual shapes. We supplemented the available information on the morphology of regenerates [23] based also on an examination of the museum specimens of Paralaudakia [20] and identified six types of regenerate's characteristic of the studied group: knob-shaped jagged, knob-shaped smooth, conical jagged, conical smooth, club-shaped and narrowed. Some types of Paralaudakia regenerates, complemented by variations in other subfamilies, are presented (Figure 4).…”

“…According to the more new proposed terminology [8,11], the following types of breaks have been distinguished: urotomy (any type, both inter-and intravertebral), autotomy per se (which, according to the authors, include only the intravertebral-type of break with the subsequent regeneration of the lost part) and pseudoautotomy (an intervertebral nonspontaneous type of tail fracture without regeneration). Intervertebral autotomy was reliably noted in a number of the agamid lizards, as well as in some snakes belonging to three families: Colubridae, Lamprophiidae and Natricidae [12,20]. In this classification, agamid lizards are not assigned to any of the above categories; they occupied an indefinite position ("intermediate condition") [11,21].…”

“…Agamidae is a family within Iguania which includes species with or without the ability to autotomy and regenerative development [8]. In some genera of agamid lizards, the formed regenerates can have an unusual shape, which sharply differs from the original tail [20,23].…”

Regeneration in Reptiles Generally and the New Zealand Tuatara in Particular as a Model to Analyse Organ Regrowth in Amniotes: A Review

“…In conjunction with autotomy, lizards also evolved a process of regeneration of the tail as a prominent process of post-embryonic development and differentiation. The ability of lizards to regenerate the tail is present to different degrees among extant lizard families [ 36 , 37 , 38 ], but can vary even within families [ 39 ]. Although an enormous amount of scientific literature exists on tail regeneration in lizards, rather little is known in connection with recoveries of other organs and tissues such as skin, scutes, optical nerve, spinal cord, etc.…”