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The investigation of species boundaries in strictly endogeic animals is challenging because they are prone to fine-scale genetic and phenotypic geographical differentiation owing to low dispersal ability. An integrative approach exploiting different sources of information has seldom been adopted in these animals and even more rarely by treating all data sources equally. We investigated species boundaries in the endogeic centipede Clinopodes carinthiacus across the south-eastern Alps by studying genetic and morphological differentiation in a sample of 66 specimens from 27 sites, complemented by the morphological examination of more than 1100 specimens from other sites. Hypotheses of species delimitation were obtained independently from the molecular sequences of three markers (mitochondrial 16S and COI and nuclear 28S) by means of different species discovery methods (automatic barcode gap discovery, assemble species by automatic partitioning, general mixed Yule coalescent and the Poisson tree process) and from ten morphological characters by means of a model-based cluster analysis and Bayesian model selection. We found strong support for the existence of at least two species: C. carinthiacus s.s. and Clinopodes strasseri , which was formerly described as a subspecies of another species, and later placed in synonymy with C. carinthiacus. The two species coexist in syntopy in at least one site. [ABSTRACT FROM AUTHOR]

Abstract Trophic niche partitioning between potentially competing species within the same coenosis has been little explored for most of the major groups of arthropod soil predators, among which are the geophilomorph centipedes. We performed a comparative study in nature on the diet of three species of Geophilomorpha living in the same site in Southern Europe. Through PCR-based molecular gut content analysis, we estimated trophic niche width and overlap with respect to three common prey groups: lumbricids, collembolans and dipteran larvae. Results show that apparently similar geophilomorph species differ significantly in prey spectrum, with quite different niche widths. Estimates of predator diet overlap gave moderate values, non-significantly different from null expectations. Within-species diet composition does not vary significantly with sex. This work, while providing the first evidence of trophic niche partitioning among coexisting geophilomorph species, contributes to recent progresses in the understanding of intra-guild interactions between predators in the soil food webs. Highlights • Three species of geophilomorphs living in the same coenosis differ in prey spectrum. • They differ in trophic niche width and exhibit modest niche overlap. • There is no evidence of intra-specific diet variation with sex. [ABSTRACT FROM AUTHOR]

Plutonium zwierleini is one of the largest scolopendromorph centipedes in Europe and is known for debates on the evolution of segmental body pattern in arthropods. However, only 24 records have so far been reported and probably only a dozen specimens still exist in collections. Based on 19 new data from professionals and amateur recorders, we confirmed that populations are present today in four disjunct areas: southern Iberian Peninsula, Sardinia, southern Italian Peninsula and Sicily. A phylogenetic analysis of the first molecular data obtained for Plutonium (16S, COI, 18S, 28S) provided strong evidence that it is closely related to Theatops, either sister to the latter or nested within it, with an estimated separation since the Mesozoic. By examining specimens of Plutonium from all the four inhabited areas and specimens of most of the species of Theatops, we also documented many synapomorphies uniting Plutonium and Theatops (brown-orange colour, whitish patches replacing the ocelli, a particular denticulation on the forcipules, conspicuously swollen and piercing ultimate legs) and some derived characters unique to Plutonium, including the blade-edged claws of the ultimate legs and the previously overlooked presence of long, dense setae on most other legs, in both sexes and in the entire species range. [ABSTRACT FROM AUTHOR]

Geophilomorph centipedes are common arthropod soil predators, but very little is known about their preying behaviour and their diet. Here we develop an exploratory morpho-functional approach to better understand their feeding habits, based on the morphology of feeding-related structures. Through geometric morphometrics, in a sample of five geophilomorph species, we investigated morphological variation in the three most conspicuous component structures of their prey-catching apparatus. At intra-specific level, we found no strong evidence for sexual dimorphism, left-right directional asymmetries and allometry across adult stages. At inter-specific level, shape differences in the feeding apparatus among the sample species were highly significant and large, even between two congeneric species. We also found a significant covariation between the shapes of the three structures, including those that do not directly articulate with each other, suggesting some degree of morphological integration between the different structures of the prey-catching apparatus. This study suggests the effectiveness and power of geometric morphometrics for the quantitative study of centipede functional morphology and provides a basis for wider comparative investigations on their phenotypic evolution. [ABSTRACT FROM AUTHOR]

Does a modular body organization present a challenge for developmental control? We investigate the idea of a possible developmental cost of modularity by examining the relationship between modularity and developmental stability in a multi-segmented arthropod taxon: the geophilomorph centipedes. In a sample of eight species, we tested the correlation between developmental stability, estimated from measures of translational fluctuating asymmetry, and the number of trunk segments and some other morphological traits, both at the species and individual levels. We found sizeable differences in size and shape patterns of variation at the level of species. However, we did not find any clear evidence of correlation between fluctuating asymmetry and the number of trunk segments or the other morphological traits considered. Thus, our results provide no support to the idea of a possible trade-off between the cardinality of a modular system and the level of developmental precision in the phenotypic expression of its modules. The results of this exploratory study invite further investigations of patterns of translational fluctuating asymmetry in segmented animals and other modular organisms, as these have the potential to reveal features of developmental stability that cannot be captured by the study of bilateral asymmetry alone. [ABSTRACT FROM AUTHOR]

European populations of the geophilomorph centipede Haplophilus subterraneus show a high proportion of individuals with morphological anomalies, suggesting high levels of developmental instability. The broad geographic distribution of this phenomenon seems to exclude local environmental causes, but the source of instability is still to be identified. The goal of the present study was to collect quantitative data on the occurrence of phenodeviants in different populations, along with data on the patterns of genetic variation within and between populations, in order to investigate possible association between developmental instability and genetic features. In a sample of 11 populations of H. subterraneus, distributed in western and central Europe, we looked for phenodeviants, in particular with respect to trunk morphology, and studied genetic variation through the genotyping of microsatellite loci. Overall, no support was found to the idea that developmental instability in H. subterraneus is related to a specific patterns of genetic variation, including inbreeding estimates. We identified a major genetic partition that subdivides French populations from the others, and a low divergence among northwestern areas, which are possibly related to the post-glacial recolonization from southern refugia and/or to recent anthropogenic soil displacements. A weak correlation between individual number of leg bearing segments and the occurrence of trunk anomalies seems to support a trade-off between these two developmental traits. These results, complemented by preliminary data on developmental stability in two related species, suggest that the phenomenon has not a simple taxonomic distribution, while it exhibits an apparent localization in central and eastern Europe. [ABSTRACT FROM AUTHOR]

Postembryonic segmentation (anamorphosis) is widespread among arthropods, but only partially known as for its developmental mechanics and control. Studies on developmental genetics of segmentation in anamorphic arthropods are mostly limited to the germ band stage, during early phases of embryonic development. This work presents the first data on the postembryonic expression of a segmentation gene in a myriapod. Using real-time PCR, we analyzed engrailed expression patterns during the anamorphic stages of the centipede Lithobius peregrinus. A variation pattern in en RNA level during anamorphosis suggests that gene expression is precisely modulated during this period of development and that engrailed is mainly expressed in the posterior part of the body, in the newly differentiating segments of each stage. As anamorphosis is possibly the primitive segmentation mode in arthropods, the postembryonic en expression pattern documented here provides evidence for a conservation of en role in ontogeny, across the embryonic/postembryonic boundary, as well as in phylogeny, across the same boundary, but in the opposite direction, from primitive postembryonic expression to the more derived expression in clades with exclusively embryonic segmentation. [ABSTRACT FROM AUTHOR]

Using the centipede model species Strigamia maritima as a subject of study, we illustrate the potential of geometric morphometrics for investigating the development and evolution of segmentation, with a specific focus on post-embryonic segmental patterning. We show how these techniques can contribute detailed descriptive data for comparative purposes, but also precious information on some features of the developmental system that are considered relevant for the evolvability of a segmented body architecture, such as developmental stability and canalization. Morphometric analyses allow to separately investigate several sources of phenotypic variation along a segmented body axis, like constitutive and random segment heteronomy, both within and among individuals. Specifically, in S. maritima , the segmental pattern of ventral sclerite shapes mirrors that of their bilateral fluctuating asymmetry and among-individual variation in associating the most anterior and most posterior segments in diverging from the central ones. Also, among segments, there seems to be a correlation between fluctuating asymmetry and shape variation among individuals, suggesting that canalization and developmental stability are somehow associated. Overall, these associations might stem from a joint influence of the segmental position on the two processes of developmental buffering. [ABSTRACT FROM AUTHOR]

Abstract: In arthropods, molting events are mediated by the binding of the ecdysone hormone to a heterodimer of two nuclear receptors: the ecdysone receptor (EcR) and the retinoid X receptor (RXR), a homolog of ultraspiracle (USP). We have cloned partial sequences of several isoforms for EcR and RXR genes from the centipede Lithobius peregrinus, and studied their expression profile during the second post-embryonic stage. LpEcR and LpRXR inferred amino acid sequences are very similar to other arthropod orthologs, especially to those of chelicerates and hemimetabolous insects, and their expression levels are significantly higher during the 48h that precede the molt. Results obtained in this study represent the first data on the genetic basis of the ecdysone signal pathway for a myriapod, and in particular for an animal that, through a stereotyped developmental schedule paced by the molt cycle, completes trunk segmentation during post-embryonic life. [Copyright &y& Elsevier]

Abstract: We describe and analyze naturally occurring anomalies in the segmental structures of the trunk in an isolated population of the geophilomorph centipede Stigmatogaster subterranea. Recorded anomalies include mispaired tergites, shrunk segments, variously deformed sclerites, bifurcated trunk, and defects of spiracles and sternal pore areas. One specimen has a perfect segmentally patterned trunk, but with an even number of leg-bearing segments, representing the first record of such a phenotype in adult centipedes. We interpret these anomalies as the effects of perturbation of specific morphogenetic processes in trunk segmentation, occurring at different embryonic stages. The variety of segmental anomalies found in this population provides insights into the developmental process of segmentation and its evolution in geophilomorph centipedes. Variation in dorsal mispairing anomalies demonstrates that segments, as traditionally defined in arthropod morphology, are not the effective developmental units throughout embryogenesis. [Copyright &y& Elsevier]