Insects are generally negligent parents: a female lays dozens or hundreds of eggs and flies off, leaving the young to fend for themselves. Most will die but a few will survive to lay hundreds more eggs and keep playing the numbers game. Tsetse flies, not unlike mammals, have taken the opposite tack, investing a whole lot of energy in each offspring. She keeps her eggs and larvae in the safest place possible for the longest time: inside her uterus. That’s the evolutionary explanation for live birth.
With a hungry larva to feed in her uterus, the tsetse fly makes a liquid rich in fats that scientists dubbed “intrauterine milk.” This new study found tsetse fly milk contains an enzyme called SMase that is activated in the acidic conditions of the larva’s stomach. SMase makes the fat molecules that form critical parts of cell membranes. This enzyme has a similar function in mammals—tsetse fly and mammal lactation probably evolved independently given the evolutionary distance between us and an insect, so SMase seems like a curious case of convergent evolution.
29 April 2012
Tsetse flies lactate ! And give live birth.
Are you kidding me? No. I read it in Discover Magazine's 80 Beats column: