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Massive Genome Revealed in Brooding Brittle Star Through Chromosome Duplication

Recent research conducted by life scientists at the University of Sydney, in collaboration with an expert from Museums Victoria, has unveiled significant findings regarding the brooding brittle star (Amphipholis squamata). This species has been identified as possessing an exceptionally large genome, attributed to the duplication of its chromosomes.

The team’s study, which was published in the journal Royal Society Open Science, involved genetic analyses conducted by Maria Byrne, Timothy O’Hara, and Andrew Hugall. The brooding brittle star, a member of the echinoderm class Ophiuroidea and closely related to starfish, is characterized by its small body and elongated arms. Previous studies have established their remarkable adaptability, with the organisms inhabiting diverse marine environments across the globe. This research sought to investigate the underlying factors contributing to their environmental adaptability by focusing on their genomic structure.

The findings revealed that the brooding brittle star exhibits such a vast and varied genome that the researchers faced challenges in classifying it as a single species. Notably, these creatures are hermaphroditic and show signs of inbreeding and cloning, alongside a distinct sperm morphology.

One of the key discoveries was the occurrence of polyploidization in these brittle stars, where chromosomes are duplicated multiple times. The research team posits that rather than evolving into separate species when faced with new environments, the brittle star might hybridize between different lineages, which contributes to its remarkable genetic diversity.

Interestingly, the team observed instances in which entire genomes merge, resulting in an even greater number of chromosome copies. They speculate that the origin of this polyploidization is likely allopolyploidy, as evidenced by multiple chromosome sets that appear to derive from distinct species, typically a product of hybridization.

Despite the intriguing findings, the study did not identify the precise mechanisms behind the evolution of such an extensive genome. The researchers suggest that these mechanisms might be linked to the brooding brittle star’s widespread distribution. Future studies could explore additional environmental variables, parasite interactions, and the physical attributes that contribute to this phenomenon.

More information:
Andrew F. Hugall et al, Genetic variation in the brooding brittle-star: a global hybrid polyploid complex? Royal Society Open Science (2024). DOI: 10.1098/rsos.240428

Source
phys.org