Introns in the Lotharella oceanica and Bigelowiella natans nucleomorph genomes . A) Intron size distribution for L. oceanica (left) and B. natans (right). The numbers above each bar show the actual numbers of introns in each size category. B) Intron comparison of two chlorarachniophyte nucleomorph genomes. The Venn diagram shows the number of shared and/ or unique comparable spliceosomal introns in the two genomes. Comparable spliceosomal introns were selected using the criteria proposed by Roy and Penny .