How do sperm cells and egg meet in cod

External fertilization - Wikipedia

It's the stuff of 3rd-grade sex ed: sperm meets egg to make baby. they've found that outlet: a receptor protein on the surface of the egg cell. If these differ, the two cells are unlikely to meet correctly or induce the acrosome reaction, where the sperm basically burns its way through the. Then, the male releases his sperm to fertilize them. However, a few species of frog use internal fertilization. In this case, the eggs are fertilized.

Most anurans now externally fertilize. Males will congregate near a lake or pond and establish calling stations.

Fish reproduction

Females approach the area and listen to all of the different male calls, and then continue to move towards the mate she chooses. It has been concluded that females prefer a male with a more attractive call, which is also the larger male.

They then move to a spot near water to simultaneously release their sperm and eggs. Other males in the area can also release sperm onto the eggs to also attempt to fertilize the eggs.

  • External fertilization
  • Fertilization
  • The Tadpole or the Egg?

If the female does not want to reproduce with the male that jumps onto her back, she will wait until the male leaves or move to a new location. When the anurans are not close to eggs, they sometimes release their sperm into oocyte containing foam nests, or terrestrial breeders go right to the gel coat of the oocyte to release their sperm.

Females, however, can only release eggs once per breeding season. This has been tested, with good evidence associated with a larger sperm number and testes size. Familiar examples of ovoviviparous fish include guppiesangel sharksand coelacanths. Viviparity There are two types of viviparitydifferentiated by how the offspring gain their nutrients. Histotrophic tissue eating viviparity means embryos develop in the female's oviducts but obtain nutrients by consuming other tissues, such as ova oophagy or zygotes.

This is most commonly found among sharks such as the grey nurse sharkbut has also been reported for Nomorhamphus ebrardtii. Aquarists commonly refer to ovoviviparous and viviparous fish as livebearers.

Hermaphroditism[ edit ] Female groupers change their sex to male if no male is available An anemone fish couple guarding their anemone. If the female dies, a juvenile male moves in, and the resident male changes sex. Female anglerfish, Haplophryne molliswith atrophied males attached Parthenogenesis was first described among vertebrates in the Amazon molly Main article: Hermaphroditism Hermaphroditism occurs when a given individual in a species possesses both male and female reproductive organs, or can alternative between possessing first one, and then the other.

Hermaphroditism is common in invertebrates but rare in vertebrates. It can be contrasted with gonochorismwhere each individual in a species is either male or female, and remains that way throughout their lives.


Most fish are gonochorists, but hermaphroditism is known to occur in 14 families of teleost fishes. This can happen if a dominant male is removed from a group of females. The largest female in the harem can switch sex over a few days and replace the dominant male. It is less common for a male to switch to a female protandry. Wrasses exhibit three different mating systems: The type of spawning that occurs depends on male body size.

Less commonly hermaphrodites can be synchronous, meaning they simultaneously possess both ovaries and testicles and can function as either sex at any one time. Black hamlets "take turns releasing sperm and eggs during spawning. Because such egg trading is advantageous to both individuals, hamlets are typically monogamous for short periods of time—an unusual situation in fishes.

Anemone fishes live together monogamously in a anemoneprotected by the anemone stings. Then, the male releases his sperm to fertilize them. However, a few species of frog use internal fertilization.

A New Way Frogs Reproduce | Ask A Biologist

All mammals, including humans, use this process of fertilization. However, little was known about how this species reproduced. Inside of the female fanged frog, the researchers found developed tadpoles rather than eggs.

Was it through the more common process of external fertilization? Do they lay eggs on leaves or in water, like most frog species? They searched for these fanged frogs, and caught them with their hands. After catching a number of these frogs, they discovered something unexpected. Instead of eggs, they found tadpoles inside the frogs.

The scientists first noticed this while dissecting, or cutting into, the bodies of dead frogs. They did this to better understand the internal structure of the frogs.

A close-up view of the tadpoles found inside a female fanged frog. The scientists also wanted to study the body tissue and DNA from the frogs to map the frogs' genes. This would help scientists to learn the relationship between this frog species and others.

Fish reproduction - Wikipedia

In the bodies of some female frogs, scientists found fully developed tadpoles. In one instance, a pregnant female gave birth to live tadpoles on the hand of a researcher who caught her. These tiny tadpoles were mostly clear in color with spots around their bodies.

This finding is very unusual because scientists only expected to find eggs, which are common in most female frogs. A One of a Kind Frog Why does this difference make the fanged frog so special?