doi.org
Myoanatomy of Paracentrophyes quadridentatus (Neocentrophyidae, Kinorhyncha) and evolution of major muscle groups across kinorhynchs - Organisms Diversity & Evolution
The latest phylogenetic analysis of Kinorhyncha established the major group Anomoirhaga, which encompasses the greatest morphological diversity within the phylum. Although the myoanatomy of most Anomoirhaga families has been documented, it remains undescribed for Neocentrophyidae which includes the three genera Mixtophyes, Paracentrophyes and Neocentrophyes. To address this gap, we characterised the musculature of Paracentrophyes quadridentatus through F-actin staining, confocal laser scanning microscopy (CLSM), and 3D reconstruction. In addition, we defined, coded, and traced the evolution of twenty-two myoanatomical characters across eight kinorhynch families, reconstructing their ancestral states to gain insights into muscle evolution within the phylum. Seven myoanatomical synapomorphies were found, supporting several kinorhynch clades. Multiple muscles present in P. quadridentatus constitute unique apomorphies within Anomoirhaga. Yet others are similar (through convergence) to muscles in evolutionary distant taxa with similar external morphology. This, and the finding of thirteen homoplastic muscular characters, suggest a high plasticity in the evolution of kinorhynch musculature. The results of this study present a basis for comparative studies of kinorhynch myoanatomy, which can enhance our understanding of muscular functions, and the evolutionary processes underpinning myoanatomical adaptations in invertebrates.
