Morphological integration of the head capsule in the millipede Megaphyllum unilineatum (C. L. Koch, 1838) (Diplopoda: Julida): can different modules be recognized?

Vukica Vujić; Bojan Ilić; Luka Lučić; Vladimir Tomić; Zvezdana Jovanović; Sofija Pavković-Lučić; Slobodan Makarov

doi:10.1016/j.zool.2021.125970

Morphological integration of the head capsule in the millipede Megaphyllum unilineatum (C. L. Koch, 1838) (Diplopoda: Julida): can different modules be recognized?

Zoology (Jena). 2021 Dec:149:125970. doi: 10.1016/j.zool.2021.125970. Epub 2021 Oct 5.

Authors

Vukica Vujić¹, Bojan Ilić², Luka Lučić³, Vladimir Tomić⁴, Zvezdana Jovanović⁵, Sofija Pavković-Lučić⁶, Slobodan Makarov⁷

Affiliations

¹ University of Belgrade, Faculty of Biology, Studentski Trg 16, 11000, Belgrade, Serbia. Electronic address: vukica.vujic@bio.bg.ac.rs.
² University of Belgrade, Faculty of Biology, Studentski Trg 16, 11000, Belgrade, Serbia. Electronic address: bojan.ilic@bio.bg.ac.rs.
³ University of Belgrade, Faculty of Biology, Studentski Trg 16, 11000, Belgrade, Serbia. Electronic address: luka@bio.bg.ac.rs.
⁴ University of Belgrade, Faculty of Biology, Studentski Trg 16, 11000, Belgrade, Serbia. Electronic address: vlada@bio.bg.ac.rs.
⁵ University of Belgrade, Faculty of Biology, Studentski Trg 16, 11000, Belgrade, Serbia. Electronic address: zjovanovic@bio.bg.ac.rs.
⁶ University of Belgrade, Faculty of Biology, Studentski Trg 16, 11000, Belgrade, Serbia. Electronic address: sofija@bio.bg.ac.rs.
⁷ University of Belgrade, Faculty of Biology, Studentski Trg 16, 11000, Belgrade, Serbia. Electronic address: slobodan@bio.bg.ac.rs.

PMID: 34628210
DOI: 10.1016/j.zool.2021.125970

Abstract

Covariation of multiple morphological traits and modularity have been widely studied in the field of evolutionary developmental biology. Subunits of a morphological structure can evolve separately from each other in a modular fashion. The aims of our study therefore were: i) to test the hypothesis of modularity in the dorsal part of the head capsule and the gnathochilarium separately during late postembryogenesis in the julidan millipede Megaphyllum unilineatum (C. L. Koch, 1838) using geometric morphometrics; and ii) to investigate the influence of allometry on overall morphological integration in the dorsal part of the head capsule and the gnathochilarium in the mentioned species. Individuals from different ontogenetic stadia (stadium VI - stadium XI) were included in the analyses. Significant influence of fluctuating asymmetry on the dorsal part of the head capsule shape was detected by Procrustes ANOVA. Regressions were significant for the symmetric component of both analysed morphological traits, while non-significant regression was detected for the asymmetric component of the head capsule's dorsal part. Hypotheses of modularity for the dorsal part of the head capsule and the gnathochilarium are rejected because our results indicate that a small proportion of alternate partitions has higher covariation between subsets of structure than between the hypothesized modules. Contrary to our expectations, results of the present study show that allometry does not increase the level of morphological integration in the dorsal part of the head capsule and the gnathochilarium in M. unilineatum. Based on the obtained results, we conclude that the dorsal part of the head capsule and the gnathochilarium are not composed of independent modules and that in the case of the capsule's dorsal part, developmental processes affect morphological integration in different ways at different levels of shape variation.

Keywords: allometry; geometric morphometrics; modularity hypotheses; variation of morphological shape.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Arthropods*
Biological Evolution
Head
Morphogenesis
Phenotype