Body and skull morphometric variations between two shovel-headed species of Amphisbaenia (Reptilia: Squamata) with morphofunctional inferences on burrowing.

Leandro Dos Santos Lima Hohl,José Duarte De Barros-Filho,Mariana Fiuza De Castro Loguercio,Fernando Lencastre Sicuro,Oscar Rocha-Barbosa

doi:10.7717/peerj.3581

Leandro Dos Santos Lima Hohl, José Duarte De Barros-Filho + Show 3 more

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https://doi.org/10.7717/peerj.3581

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Abstract

BackgroundMorphological descriptions comparing Leposternon microcephalum and L. scutigerum have been made previously. However, these taxa lack a formal quantitative morphological characterization, and comparative studies suggest that morphology and burrowing performance are be related. The excavatory movements of L. microcephalum have been described in detail. However, there is a lack of studies comparing locomotor patterns and/or performance among different amphisbaenids sharing the same skull shape. This paper presents the first study of comparative morphometric variations between two closely related amphisbaenid species, L. microcephalum and L. scutigerum, with functional inferences on fossorial locomotion efficiency.MethodsInter-specific morphometric variations were verified through statistical analyses of body and cranial measures of L. microcephalum and L. scutigerum specimens. Their burrowing activity was assessed through X-ray videofluoroscopy and then compared. The influence of morphological variation on the speed of digging was tested among Leposternon individuals.ResultsLeposternon microcephalum and L. scutigerum are morphometrically distinct species. The first is shorter and robust with a wider head while the other is more elongated and slim with a narrower head. They share the same excavatory movements. The animals analyzed reached relatively high speeds, but individuals with narrower skulls dug faster. A negative correlation between the speed and the width of skull was determined, but not with total length or diameter of the body.DiscussionThe morphometric differences between L. microcephalum and L. scutigerum are in accord with morphological variations previously described. Since these species performed the same excavation pattern, we may infer that closely related amphisbaenids with the same skull type would exhibit the same excavatory pattern. The negative correlation between head width and excavation speed is also observed in others fossorial squamates. The robustness of the skull is also related to compression force in L. microcephalum. Individuals with wider heads are stronger. Thus, we suggest trade-offs between excavation speed and compression force during burrowing in this species.

Highlights

IntroductionAmphisbaenians are fossorial reptiles with an elongated and cylindrical body shape (Gans, 1969) and, except the three Bipes species, all (nearly 200 species, Uetz, Freed & Hosek, 2016) are limbless
Amphisbaenians are fossorial reptiles with an elongated and cylindrical body shape (Gans, 1969) and, except the three Bipes species, all are limbless
We describe the excavatory pattern and performance of L. scutigerum, comparing its locomotor traits with L. microcephalum; and we verify the relation between the length and robustness of the body and skull with the burrowing speed among Leposternon individuals

Summary

Introduction

Amphisbaenians are fossorial reptiles with an elongated and cylindrical body shape (Gans, 1969) and, except the three Bipes species, all (nearly 200 species, Uetz, Freed & Hosek, 2016) are limbless. The ‘‘shovel’’ type, shared by the genera Rhineura (Rhineuridae, North America), Dalophia and Monopeltis (Amphisbaenidae, Africa), and Leposternon (Amphisbaenidae, South America), is considered the most specialized for digging (Gans, 1974; Gans, 2005; Kearney, 2003; Hohl et al, 2014) This means that these animals are able to penetrate more into highly compacted soils reaching greater depths. Inter-specific morphometric variations were verified through statistical analyses of body and cranial measures of L. microcephalum and L. scutigerum specimens Their burrowing activity was assessed through X-ray videofluoroscopy and compared. The morphometric differences between L. microcephalum and L. scutigerum are in accord with morphological variations previously described Since these species performed the same excavation pattern, we may infer that closely related amphisbaenids with the same skull type would exhibit the same excavatory

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