I found a setence in one paper
The orthologs and orthogroups between bottlenose catfish and channel catfish were generated using OrthoFinder (42). To obtain the species-specific genes, Protein BLAST (BLASTP) was performed in which genes not included in the orthogroups were queried against the genes in the orthogroups within the same species, with a maximal E-value of 1e-10. A reciprocal BLASTP with a maximal E-value of 1e-5 was used to query genes with no hits from previous steps (9). The genes with no hits to any orthologs were considered as species-specific genes.
But I am not sure what's the meaning of the BLAST part, orthofinder will give us multiple of files, so which files should be used for the BLASP? I will be pretty appreciated if you could give some guidance in detail :)