Is there external fertilization with live birth in fish?

Yes, there are fish species that exhibit external fertilization with live birth, also known as ovoviviparity. In this reproductive strategy, the eggs are fertilized outside the female's body, but the embryos develop and hatch within the female's reproductive system. The fertilized eggs receive nourishment from the yolk sac and may also obtain additional nutrients from the female through specialized structures.

Examples of fish species with external fertilization and live birth include:

1. Atlantic Poecilia (Poecilia latipinna): This freshwater fish is commonly known as the sailfin molly and belongs to the family Poeciliidae. Male sailfin mollies fertilize the eggs externally, and the fertilized eggs develop inside the female. Females give birth to live fry that are fully formed and capable of swimming and feeding on their own.

2. Sea Horses (Hippocampus species): Seahorses belong to the family Syngnathidae and are renowned for their unique reproductive behavior. Male seahorses have a specialized brood pouch where they receive fertilized eggs from the female. The eggs develop and hatch within the brood pouch, and the male provides parental care until the young seahorses are ready to be released.

3. Livebearer Toothcarps (Goodeidae and Poeciliidae families): Several species within the families Goodeidae and Poeciliidae exhibit live birth after external fertilization. These fish are native to various regions of North and Central America, and they have adapted to diverse aquatic habitats. Livebearer toothcarps, such as the guppy (Poecilia reticulata), display internal fertilization, but the fertilized eggs are retained within the female's body until they hatch.

It's important to note that external fertilization with live birth is not a common reproductive strategy among all fish species. Many fish species practice external fertilization with the release of eggs and sperm into the water, and the fertilized eggs develop externally. Ovoviviparity is observed in specific fish groups that have evolved adaptations to protect and nurture their offspring during the early stages of development.