3 species correspond to let-7a-1* (mmu, cin and rno), but not human (hsa). For mouse for example, mmu-let-7a-1-3p and both mmu-let-7a* and mmu-let-7a-1* are synonymous (the -3p being the actual used name). The -5p corresponds to the opposite arm of the pre-miRNA. The star corresponds to the less abundant (in general) arm.