Mitochondrial genome and feeding preference of the bacterivorous nematode Acrobeloides tricornis (Rhabditida: Cephalobidae)

Abstract

Acrobeloides spp. are widespread bacterivorous nematodes that play important roles in soil food webs, yet their biology and genomic characteristics remain poorly understood. In this study, we investigated the biology and mitochondrial genome of Acrobeloides tricornis , a parthenogenetic species widely distributed across different ecosystems. Species identification was confirmed using morphological characters, together with 18S and 28S rRNA gene sequences, which phylogenetically supported its precise placement within the genus Acrobeloides , clearly distinct from Paracephalobus . The complete mitochondrial genome is a circular molecule of 18 756 bp, encoding 12 protein-coding genes, 22 tRNAs and two rRNA genes. A large non-coding region was identified, contributing substantially to genome size variation within the genus; moreover, its conserved gene arrangement provided further evidence for evolutionary divergence from Paracephalobus . Cytogenetic analysis revealed that A. tricornis possesses six chromosomes. Feeding preference and life-history traits were examined under four bacterial diets and two temperature regimes. The results showed that both factors significantly influenced body size, fecundity and lifespan, with nematodes fed on Sphingomonas sp. exhibiting lower reproductive output and shorter longevity than those given other bacterial diets. Overall, this study provides the first integrative characterisation of the biology, karyotype and mitochondrial genome of A. tricornis , offering new insights into the ecological and evolutionary traits of bacterivorous nematodes in the family Cephalobidae.