Did I Have a Daddy? A Parthenogenic Problem
Animals have some interesting ways in which to produce offspring. Though most animals can produce sexually, some can also produce asexually, without a mate. This is known as parthenogenesis. This ability can present potential population management problems in zoos and aquaria where maintaining a genetically diverse population is a major goal. In this activity, you will compare genotypes for several different sharks and determine whether they were produced via sexual reproduction or parthenogenesis.
A note about this species…
Zebra sharks are long and sleek, allowing them to wriggle into reef crevices and caves to hunt for their food. Barbels (fleshy feelers) on their snouts help them search for their prey. Zebra sharks hunt at night; in the daytime they usually rest quietly on the bottom, “standing” on their pectoral (side) fins. To reproduce, male sharks use claspers (modifications of the pelvic fins) to transfer sperm into the female’s reproductive tract. The zebra female lays fertilized eggs in tough capsules covered with tufts of filaments, which attach the eggs to the seafloor. But these eggs are certainly not like the eggs most recognize! These are opaque and in a tough casing that protects the shark embryo and its yolk during development. In environments where males may not be present, females have a “back-up” plan: they can produce offspring without the input from a male. However, this results in a reduction in the alleles that are available to the next generation so sexual reproduction is preferred.
ACTIVITY 12 - The Big Question: How do we determine parentage? (pdf file)