Papayas are seedless!

For some reason, all of the papayas from several of my trees are seedless this year.  They have always had seeds other years.  The fruit appears to develop normally.  One papaya tree still has fruit full of seeds like normal. Usually the lack of seeds in papaya just means that a female tree didn't receive pollination from a male.
Read all about growing papaya here:  http://growerjim.blogspot.com/2012/10/carica-papaya.html