Sharks become pregnant through internal fertilization, a process where the male directly fertilizes the female's eggs inside her body.
The Process of Internal Fertilization
Unlike many other fish species that reproduce via external fertilization (where the female lays eggs that are then fertilized by the male outside her body), sharks employ internal fertilization. This means the male must physically introduce sperm into the female's reproductive tract.
According to studies of the species we have been able to study, sharks use internal fertilisation (27.30). This is facilitated by the male's specialized reproductive organs called claspers. These are paired, rod-like structures located on the pelvic fins of male sharks. During mating, one of the male's claspers is inserted into the female's cloaca (the opening to her reproductive and excretory tracts). Sperm is then transferred through a groove in the clasper into the female, fertilizing her eggs internally.
This method of reproduction is considered more efficient than external fertilization as it increases the likelihood of successful fertilization and provides protection for the fertilized eggs or developing embryos within the female's body.
Comparing Shark Fertilization
The distinction between internal and external fertilization is a key difference in reproductive strategies among fish.
| Feature | Sharks | Most Other Fish Species |
|---|---|---|
| Fertilization Type | Internal Fertilization | External Fertilization |
| Male Organ | Claspers | No specialized insertion organ |
| Sperm Delivery | Inserted into female | Released into water near eggs |
| Egg Protection | Fertilized internally | Fertilized externally in water |
This reliance on internal fertilization and the use of claspers are defining characteristics of shark reproduction based on available studies.
