ORIGINAL PAPER Cell size versus body size in geophilomorph centipedes Marco Moretto 1 & Alessandro Minelli 1 & Giuseppe Fusco 1 Received: 22 December 2014 /Revised: 9 March 2015 /Accepted: 12 March 2015 # Springer-Verlag Berlin Heidelberg 2015 Abstract Variation in animal body size is the result of a com- plex interplay between variation in cell number and cell size, but the latter has seldom been considered in wide-ranging comparative studies, although distinct patterns of variation have been described in the evolution of different lineages. We investigated the correlation between epidermal cell size and body size in a sample of 29 geophilomorph centipede species, representative of a wide range of body sizes, from 6 mm dwarf species to gigantic species more than 200 mm long, exploiting the marks of epidermal cells on the overlying cuticle in the form of micro-sculptures called scutes. We found conspicuous and significant variation in average scute area, both between suprageneric taxa and between genera, while the within-species range of variation is comparatively small. This supports the view that the average epidermal cell size is to some extent taxon specific. However, regression analyses show that neither body size nor the number of leg-bearing segments explain this variation, which suggests that cell size is not an usual target of change for body size evolution in this group of arthropods, although there is evidence of its correla- tion with other morphological variables, like cuticle thickness. Scute sizes of miniaturized geophilomorph species are well within the range of the lineage to which the species belong, suggesting recent evolutionary transitions to smaller body size. Keywords Chilopoda . Cuticle sculpture . Epithelia . Evolution . Miniaturization Introduction Total body size and the relative dimensions of body parts are key attributes that shape most of a species’ functions, behav- iour, and ecological relationships. However, the developmen- tal mechanisms that control size and shape are still unexplored or incompletely understood in most animal taxa (Nijhout and Callier 2015). In the few animal species in which adequate studies have been performed, intraspecific variation in body size is the result of a complex interplay between variation in cell number and variation in cell size (e.g. Robertson 1959; Partridge et al. 1994; De Moed et al. 1997; Azevedo et al. 2002; Nijhout et al. 2014). Cell growth and cell proliferation are regulated by part- ly independent mechanisms that can respond separately to genetic and environmental variation (Schmelzle and Hall 2000; Nijhout 2003; Nijhout and Callier 2015). Overall, within a species, differences in cell size are argu- ably more important, as a determinant of an individual’ s body size (e.g. Stevenson et al. 1995), but this is not necessarily true in interspecific comparisons (Arendt 2007). There are funda- mental differences in the mechanisms by which distantly re- lated groups, e.g. mammals and insects, control body size (Trumpp et al. 2001), despite the existence of an evolutionari- ly conserved signaling cascade that links external nutrient sources to cell size (Stocker and Hafen 2000). Thus, differ- ences in body size between mice and elephants are mainly the result of differences in cell number (Conlon and Raff 1999), whereas cell size contributes significantly to body size varia- tion among Drosophila species (Stevenson et al. 1995). In comparative zoology, cell size is very seldom considered worth investigation, and its variation is seldom seen as a fea- ture characterizing an evolutionary trend. The general view does not go beyond textbook generalizations, e.g. that the enormous variation in adult body size across the Metazoa Communicated by: Sven Thatje * Giuseppe Fusco giuseppe.fusco@unipd.it 1 Department of Biology, University of Padova, Padova, Italy Sci Nat (2015) 102:16 DOI 10.1007/s00114-015-1269-4