Question

Suppose your mentor wanted to create a hybrid sea urchin species to study whether acutely introducing large-scale genetic diversity increases life span. To make the hybrid species, she decided to mix sperm from Arbacia luxila and eggs from Lytechinus variegatus in a very small petri dish in an in vitro fertilization assay with hopes to raise the progeny from this process. Since you're taking Developmental Biology, you know this will never work! Why won't this work? What could you suggest to improve on her assay to make the in vitro fertilization assay work?

Answer 1

The fertilisation in sea urchins takes place in the external environment. The sperms fuse with the ova in water resulting in the formation of egg. Each species secretes sperm with specific bindin molecules on its surface which gets attracted to specific binding receptors on the surface of ova. These are species specific reactions. The ova of one species will not allow sperms of other species to fertilise them. So, if sperms and ova of two species of sea urchins are placed together, fertilisation will not occur.