Comparison of Reproductive Methods in
Cartilaginous Fish: Sharks
Cartilaginous fish, which include sharks and rays, exhibit a variety of reproductive strategies
that are essential for their survival and ecological role. This article will focus on the
reproductive methods of two prominent shark species: the great white shark (Carcharodon
carcharias) and the sand tiger shark (Carcharias taurus), as well as the unique phenomenon
of intrauterine cannibalism. Additionally, it will explore how these reproductive strategies
contribute to the life cycle of these species and their greater purpose within marine
ecosystems.
Reproductive Methods of Cartilaginous Fish
Cartilaginous fish are primarily classified into three reproductive categories: oviparous,
viviparous, and ovoviviparous.
1.​ Oviparous: Oviparous species lay eggs that develop outside the female's body.
Rays commonly follow this method, producing egg cases known as "mermaid's
purses." These structures protect the developing embryos until they hatch.
2.​ Viviparous: Viviparous species give birth to live young. This method is most
notably seen in some sharks, including the great white shark. In viviparous
reproduction, embryos develop within the mother and are nourished through a
placenta-like structure.
3.​ Ovoviviparous: This method is a combination of the previous two, where
embryos develop inside eggs that hatch within the mother's body. The sand tiger
shark is a well-known example of this reproductive strategy, which includes a
unique twist—embryonic cannibalism.
Case Studies: Great White Shark and Sand Tiger Shark
Great White Shark Reproduction
The great white shark is a viviparous species that can give birth to up to 14 pups after a
gestation period of approximately 11 months. Recent studies indicate that great white sharks
utilize a placental connection to nourish their developing embryos, allowing them to grow
larger and more developed than those of oviparous species. This adaptation increases the
likelihood of survival in a competitive marine environment.
Sand Tiger Shark Reproduction
The sand tiger shark exhibits ovoviviparity, where the embryos develop inside eggs that
hatch within the female’s body. One of the most fascinating aspects of sand tiger shark
reproduction is intrauterine cannibalism, also known as "adelphophagy." In this process, the
largest embryos consume their smaller siblings, ensuring that only the strongest pups are
born. This strategy not only reduces competition for resources but also provides a higher
chance of survival for the few that do make it to birth.
Comprehension Questions
1. What is the primary characteristic of oviparous reproduction in cartilaginous fish?​
A. Embryos develop within the mother's body​
B. Eggs develop outside the female's body​
C. Live birth without egg cases​
D. Internal egg development with cannibalism
2. Which reproductive strategy is exhibited by the great white shark?​
A. Ovoviviparous​
B. Oviparous​
C. Viviparous​
D. External fertilization
3. What is the term for the unique reproductive phenomenon where embryos consume
their siblings?​
A. Ovoviviparity​
B. Adelphophagy​
C. Viviparity​
D. Oviposition
4. How many pups can a great white shark typically give birth to after gestation?​
A. Up to 14 pups​
B. More than 20 pups​
C. Only 2-3 pups​
D. Between 15-18 pups
5. What structure is commonly known as a "mermaid's purse"?​
A. Placental connection​
B. Embryonic sac​
C. Ray egg case​
D. Shark stomach
6. Which of these is a key advantage of intrauterine cannibalism in sand tiger sharks?​
A. It provides nutrition to the mother​
B. It increases the number of offspring​
C. It ensures only the strongest pups survive​
D. It shortens the gestation period
7. What is the approximate gestation period for great white sharks?​
A. 6 months​
B. 9 months​
C. 11 months​
D. 14 months
8. Which reproductive method combines aspects of both egg-laying and live birth?​
A. Viviparity​
B. Ovoviviparity​
C. Oviparity​
D. Binary fission
9. How do great white shark embryos receive nutrition during development?​
A. Through egg yolk only​
B. Through a placenta-like structure​
C. By consuming siblings​
D. Through external feeding
10. Which shark species exhibits ovoviviparity with intrauterine cannibalism?​
A. Nurse shark​
B. Great white shark​
C. Sand tiger shark​
D. Hammerhead shark