Groups of corals release all of their eggs and sperm once a year, but the timing of their spawning is under threat from climate change.

Funnel-web spiders change the timing of their distinct courtship behavior depending on what microbes they’re carrying.

In a species of freshwater turtle, embryos can move toward warmer or cooler environments within the egg and thus help choose their sexual destiny, but not all experts are convinced.

Worms with the reproduction-related TCER-1 gene deleted could fight off infection for longer and survived better when exposed to heat and radiation.

Insect eggs can take any shape at almost any size, refuting explanations for their dimensions based on geometric scaling laws or on relationships between egg traits and adult traits.

For primates, males’ fancier ornaments are linked with smaller testes, according to a new comparative study.

Asexual female nematodes use their male offsprings’ sperm to fertilize eggs, but cast away their genes.

The extremely rare event, thought to be caused by two sperm cells fertilizing the same egg simultaneously, was last reported in 2007.

Videos reveal how a female squid fertilizes her eggs—one at a time and without spilling much stored sperm.