The shortest animal introns: insights from parasitic cnidarians.

Ultra-short introns shorter than 30 bp have evolved independently at least twice within animals, with median lengths as short as 22 bp in parasitic cnidarians.

• Why it matters: Understanding the constraints on intron length in animals is limited, and discovering ultra-short introns challenges the assumption that animals lack such features, revealing new aspects of genome evolution.
• What they did: Using long-read sequencing and comparative analysis of 51 metazoan genomes, the study identified exceptionally short introns in myxobolids and Dicyema japonicum, with sequence-logo analyses showing reduced splice-site motifs.
• The result: These findings demonstrate that introns under 30 bp occur in animals and that extreme intron shortening has evolved convergently in at least two parasitic lineages, expanding knowledge of intron diversity.