Skin gland concentrations adapted to different evolutionary pressures in the head and posterior regions of the caecilian Siphonops annulatus

Carlos Jared,Daniel Carvalho Pimenta,Edmund D Brodie,Pedro Luiz Mailho-Fontana,Rafael Marques-Porto,Marta Maria Antoniazzi,Juliana Mozer Sciani

doi:10.1038/s41598-018-22005-5

Carlos Jared, Daniel Carvalho Pimenta + Show 5 more

Open Access

https://doi.org/10.1038/s41598-018-22005-5

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Journal: Scientific Reports	Publication Date: Feb 23, 2018
Citations: 18	License type: open-access

Affiliation: Instituto Butantan, Utah State University

Abstract

Amphibian skin is rich in mucous glands and poison glands, secreting substances important for gas exchange and playing a fundamental role in chemical defense against predators and microorganisms. In the caecilian Siphonops annulatus (Mikan, 1920) we observed a concentration of enlarged mucous glands in the head region. In the posterior region of the body a similar concentration is made up of enlarged poison glands. These accumulations of glands structurally resemble the macroglands previously reported in anurans and salamanders. The skin glands in these regions are each surrounded by collagen walls forming a honeycomb-like structure. The collagen network in the head region firmly attaches to tiny pits in the bones of the skull. The two extremities of the body produce different secretions, containing exclusive molecules. Considering the fossorial lifestyle of caecilians, it seems evident that the secretions of the head and caudal region serve different functions. The anterior macrogland of mucous glands, rich in mucous/lipid secretion, in conjunction with the funnel-shaped head, may act to lubricate the body and penetrate the soil, thus facilitating locomotion underground. The blunt posterior end bearing an internalized macrogland of poison glands in the dermis may act in chemical defense and/or by blocking invasion of tunnels.

Highlights

Caecilians are limbless amphibians comprising the Order Gymnophiona that are distributed in Southeast Asia, Central and South America and Africa[1,2,3]
Caecilian skin is rich in glands which secrete substances that are fundamental to several vital functions, including chemical defense against predators and microorganisms[1,5,8,9]
In the head region the accumulation is comprised of mucous glands, whereas in the posterior region, it is comprised of poison glands

Summary

Introduction

Caecilians are limbless amphibians comprising the Order Gymnophiona that are distributed in Southeast Asia, Central and South America and Africa[1,2,3] They are fossorial animals, with compact skull, reduced visual system and a pair of sensory tentacles[2,3,4,5]. In this study we analyze the skin morphology and the biochemical composition of the cutaneous secretion of different regions of the body of the caecilian Siphonops annulatus (Fig. S1), a species widely distributed in South America[19]. This caecilian has a homogeneous body surface without protuberances, its head and posterior regions exhibit glandular accumulations in the dermis. Head and posterior regions is related, respectively, to locomotion and defense against predators in the fossorial environment

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