Here, a whole testis from D. melanogaster is imaged by a spinning disc confocal microscope (20X objective). The inset shows the sperm individualization process achieved by a cystic bulge that moves along the spermatid bundle. One cystic bulge contains 64 actin cones (green) for each of the 64 spermatids (red).
Flies in the Drosophila genus produce the longest sperm cells on Earth. One species, D. bifurca, has sperm that is 58 mm (2.3 inches) long. Our good friend D. melanogaster generates sperm that are merely ~2 mm long but still ~300X the length of human sperm. Moreover, their sperm seem to navigate a female’s reproductive tract by swimming backward, or tail first.
By Irina Catrina and Diana Bratu, Hunter College