What are limiting factors for intron length? For predicting genes from a sequenced genome, you need to set a maximum intron length. How long can introns get in animals? Is there some limit?

I think the above values (500-750 kb) are wrong. < shows that most introns are less than about 10 kb (and personal experience in Drosophila confirms that - I've _rarely_ seen an intron bigger than about 5 kb). There are some very large ones, but since it's nearly impossible to detect the splicing reaction, particularly if they're very large, it's not clear whether they are spliced as one BIG intron or are instead recursively spliced (in little steps, as in < I think its safe to say that we don't know how long the biggest introns can be.