A male lamprey attaches to a female's head and shakes the lower half of her body to release her eggs. But a new study finds that some female lampreys don’t always release eggs when they mate.CHITOSE YAMAZAKI & ITSURO KOIZUMI
(See C. Yamazaki & I. Koizumi, “High frequency of mating without egg release in highly promiscuous nonparasitic lamprey Lethenteron kessleri,” Journal of Ethology, doi: 10.1007/s10164-017-0505-0 , 2017)