We all know that the largest surviving animal in the world is the blue whale. But the reproductive organs of the blue whale are not the largest. The largest animal in the world with eggs is actually a right whale, with an average weight of up to 500 kilograms, equivalent to the weight of a scalper, and 20 times heavier than the eggs of a blue whale. So why do right whales have eggs of such a weight? So big, why use it?
To know the origin of giant eggs, you must first understand the life habits and breeding methods of right whales. Right whales are mainly distributed in the Pacific Ocean, the Atlantic Ocean and other waters. Right whales are a species of baleen whale that has no teeth but dense comb-toothed whiskers and feeds on a large number of small fish and shrimp by filtering seawater.
Adult individuals can reach 18 meters long and weigh 50-90 tons, because of their large size and large food, they can eat up to 2 tons of crustaceans in a day, which makes them unsuitable for group life in the sea, so most of the time right whales will live alone, and only female whales will accompany their cubs.
In terms of reproductive behavior, right whales reach sexual maturity at about 6 to 12 years old, females only reproduce once every three to five years, and after nearly 1 year of pregnancy, females can usually only give birth to one baby whale at a time.
Other cetaceans, in order to obtain mating rights, will engage in fierce courtship battles between males, such as seeing who is strong and powerful, watching who swims faster, watching who sprays water farther, and so on. But this is not the case for right whales, whose mating process is devoid of courtship battles. All male right whales do not need to compete in the same sex to have a chance to mate, and there is no fixed sexual connection between males and females in this species, and female right whales also take turns mating with multiple males. What's more, they mate with five or six males. However, females only conceive one child at a time. This means that although many males have mated with females, they may not be able to successfully retain their own offspring, and in order to leave offspring, sperm of different males also need to compete extremely fiercely in the female's body, which is called in vivo reproductive competition.
In this way, female right whales transfer reproductive competition between males from the outside of their bodies to the inside of their bodies — sperm competition. Only males who produce more sperm have a better chance of leaving offspring. Sperm are produced from the testicles, and larger male right whales can have larger sperm production with larger testicles and penises. More sperm, on the one hand, can improve the hit rate of fertilization, on the other hand, when mating, the semen released by themselves can wash away the sperm left in the female body of the "ex".
Therefore, only males with high sperm production can conceive females. Under this pressure to survive, in order to reproduce, right whales gradually evolved huge eggs: testicles weighing about 500 kilograms, accounting for 1% of their body weight, and a 3-meter-long penis. Right whales are also a "shy" animal, and their reproductive organs are usually hidden inside the body, generally invisible, and only revealed during mating.
Reproductive competition also takes the form of sperm competition in the body of animals, such as chimpanzees. Chimpanzees also reproduce in a mixed manner, giving rise to heat all year round, during which females generally mate with multiple males in the group. Therefore, some physiological structures and characteristics of male chimpanzees reflect that the level of sperm production is very high, such as eggs are also relatively large, the outer wall of the vas deferens is strong, the seminal vesicles and prostate capacity are large, and the sperm production rate is fast. These physiological structures are designed to accommodate sperm competition. Organisms that use purely in vitro reproductive competition are generally smaller.