Abstract

Terrestrial isopods are a successful group of terrestrial crustaceans. Their exoskeletal cuticle has been studied in several species. However, it is not known whether the cuticle of these animals becomes thicker or how its structure changes as the animals grow. We aimed to determine the principles of upscaling of the exoskeletal cuticle during growth in the terrestrial isopods Armadillidium vulgare (Latreille, 1804) and Porcellio scaber Latreille, 1804 with scanning electron microscopy. The tergal cuticle becomes thicker with increasing body length. In A. vulgare, which rolls into a ball in defense against predators, the rate of increase of tergite thickness was greater than in P. scaber, which clings to the substrate when threatened. As the cuticles of both species become thicker, the proportion of the endocuticle in the cuticle increases. There is a strong correlation between cuticle thickness and the thickness of endocuticular lamellae. This indicates that in thicker cuticles, chitin-protein fibers in sequential layers change their orientation by a smaller angle. We found no significant differences in morphometric parameters between the cuticles of A. vulgare and P. scaber when controlling for cuticle thickness. This suggests that known differences in cuticle structure and composition between these two species may result from differences in cuticle thickness.

Highlights

  • The cuticle covers the bodies of arthropods and forms their exoskeleton

  • We found no significant differences in morphometric parameters between the cuticles of A. vulgare and P. scaber when controlling for cuticle thickness

  • Their tergal cuticles grow thicker with successive molts

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Summary

Introduction

The cuticle covers the bodies of arthropods and forms their exoskeleton. In crustaceans, it is often sclerotized and mineralized with calcium carbonates and calcium phosphates. It is often sclerotized and mineralized with calcium carbonates and calcium phosphates This makes it a natural composite material with chitin-protein fibers embedded in a mineralized matrix. Several layers are distinguishable in the crustacean cuticle (Roer et al, 2015). The epicuticle is a thin surface layer consisting predominantly of proteins and forming various scales and other surface ornaments (Schmalfuss, 1978; Price and Holdich, 1980) and containing only minute amounts of mineral (Seidl and Ziegler, 2012). The remainder of the cuticle is divided into the exocuticle, located immediately beneath the epicuticle, and the underlying endocuticle

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