Mitochondrial Genomics and Phylogenetics of Sea Cucumbers

Sea cucumbers (Holothuroidea) represent a diverse clade of echinoderms with significant ecological and economic importance. Mitochondrial genomes, typically circular molecules of 15–18 kb encoding 13 protein-coding genes (PCGs), 22 transfer RNAs and two ribosomal RNAs, serve as powerful markers for examining molecular evolution, species delimitation and phylogenetic relationships. Variations in gene order, nucleotide composition (for example AT-skew) and non-coding regions provide insights into deep-sea adaptations, lineage divergence and cryptic speciation. Comparative mitogenomic studies have refined taxonomic boundaries within major holothurian orders such as Aspidochirotida and Elasipodida, resolved interfamily relationships and revealed patterns of historical biogeography. Integrating mitochondrial data with nuclear markers and morphological traits has led to a more robust framework for understanding sea cucumber evolution, aiding conservation and sustainable exploitation of these benthic invertebrates.

Research from Nature Portfolio

Recent work has applied mitochondrial cytochrome oxidase subunit I (COI) sequences alongside microsatellite genotyping to unravel pseudo-cryptic diversity within a widely collected Stichopus species complex. Two distinct COI lineages diverged approximately 1.4–2.5 million years ago and correspond to morphological groupings historically attributed to separate species. Concordant microsatellite clusters confirm limited gene flow and reinforce species boundaries, while detection of later-generation hybrids highlights occasional inter-lineage mating. Morphological distinctions in papillae distribution were documented, though certain spicule features proved unreliable for diagnosis. This integrative approach emphasises the importance of combined mitochondrial and nuclear data in clarifying species limits and uncovering hidden diversity in holothurians.

Mitochondrial Genomics and Phylogenetics of Sea Cucumbers publication trend

The graph below shows the total number of articles in mitochondrial genomics and phylogenetics of sea cucumbers across all publications each year (not limited to Nature Index journals).

Technical terms

mitochondrial genome (mitogenome): The circular DNA molecule within mitochondria encoding genes for oxidative phosphorylation and RNA components.

cytochrome oxidase subunit I (COI): A mitochondrial protein-coding gene commonly used as a barcode marker for species identification and phylogeography.

microsatellite marker: Short, tandemly repeated DNA sequences used to assess genetic diversity, population structure and gene flow.

phylogenetic inference: Analytical methods (such as Bayesian inference or maximum likelihood) for reconstructing evolutionary relationships among taxa.

AT-skew: A measure of the relative proportions of adenine versus thymine nucleotides, indicative of strand-specific mutational biases.

References

1. Pseudocryptic diversity and species boundaries in the sea cucumber Stichopus cf. horrens (Echinodermata: Stichopodidae) revealed by mitochondrial and microsatellite markers. Scientific Reports (2024).
2. A novel deep-benthic sea cucumber species of Benthodytes (Holothuroidea, Elasipodida, Psychropotidae) and its comprehensive mitochondrial genome sequencing and evolutionary analysis. BMC Genomics (2024).
3. The Complete Mitochondrial Genome of Stichopus naso (Aspidochirotida: Stichopodidae: Stichopus) and Its Phylogenetic Position. Genes (2022).
4. Analysis of Complete Mitochondrial Genome of Bohadschia argus (Jaeger, 1833) (Aspidochirotida, Holothuriidae). Animals (2022).