Photograph by Martin Oeggerli, National Geographic
Dryas iulia
Perched on the tendril of a Passiflora plant, the egg of the Julia heliconian butterfly may be safe from hungry ants. This species lays its eggs almost exclusively on this plant’s twisted vines.
Eggs released into the water by mussels for fertilisation send out a chemical message that tells sperm they are a compatible mate, say researchers.
Evolutionary biologist Dr Jonathan Evans, from University of Western Australia, and colleagues, report their findings today in the Proceedings of the Royal Society B.
“The business of finding an egg is not as straight forward as you think it would be,” says Evans.
Mussels, like other marine invertebrates that are not mobile, release eggs and sperm into the water and these gametes must then find each other.
“These things are fixed to a rock. Their sperm and eggs go into a turbulent marine environment and they need some kind of clever mechanism to find each other,” says Evans.
It is known that many species release chemical clues to attract sperm to fertilise them - a process known as ‘sperm chemotaxis’.
-anna salleh
Harlequin Bugs Hatching: A mother harlequin bug watches on as her eggs hatch. She has spent the last week perched atop the cluster of eggs watching guard. The young bugs emerge looking like miniature versions of their parents and stay closely packed together for a number of weeks.
A FOSSIL OF A pregnant prehistoric marine reptile provides the first evidence that plesiosaurs gave birth to live offspring rather than laying eggs, a US study said on Thursday.
The 78-million-year-old fossil of the Polycotylus latippinus, a four-flippered swimmer something like a snake-turtle combination, is now on display at the Natural History Museum of Los Angeles County.
Scientists have long suspected that the large creatures, which once were among the top predators in the world’s oceans, were not built for climbing on land and laying eggs, but had no evidence to show otherwise until now.
“This fossil documents live birth in plesiosaurs for the first time, and so finally resolves this mystery,” said co-author Robin O’Keefe of Marshall University in Huntington, West Virginia.
Eggs of high-elevation frogs may be 30 percent larger than those of lowland females, giving tadpoles a head start.
