Fertilisation

February 5, 2025

All shark species utilize internal fertilisation and can be divided into two main groups: oviparous (egg-laying) and viviparous (live-bearing). Viviparous species are further divided into aplacental (where the developing young do not form a placental connection, instead having a yolk dependency, some aplacental species will exhibit ‘oophagy’ and ingest unfertilised eggs in the uterus, sand tiger sharks go even further whereby the largest embryo will eat other developing embryos.

Other viviparous species form placental connections (placental viviparity) with the mother and absorb nutrients directly. Incredibly some captive female sharks have been shown to exhibit ‘automictic parthenogenesis’. During which an unfertilised egg merges with another cell from the mother to form a foetus. DNA sequencing in such cases has confirmed that 100% of the pup’s genes are derived solely from the mother.