Sperm cytology: Kernechtrot–picroindigocarmine stain and dog semen

Animal sexual abuse cases present as an unusual scenario for forensic investigators. In this study, the kernechtrot–picroindigocarmine (KPIC, aka Christmas tree stain) staining properties of semen from 8 domestic dogs was compared to two samples of human sperm. In the head of the dog sperm, the acrosomal region stained pale red and the postacrosomal region stained dark red. There was a colorless band with a mean length of 0.59 μm within the sperm head between the acrosomal and postacrosomal regions. The colorless band was not identified within the human control samples nor reported in the literature. This data supports the use of KPIC stain for the examination of dog semen and further characterizes a unique staining pattern found in dog sperm that is not present in human sperm.