"The Motherly Love of Leeches "
Leeches are actually loving parents, according to evolutionary biologist Fred Govedich of Monash University in Australia. His discovery places the Australian leech (Helobdella papillornata) among the few invertebrates to actively care for young into maturity.
Despite their reputation as opportunistic bloodsuckers, these slimy critters show surprising consideration for their offspring, carrying them around and feeding them for up to six weeks after hatching. These pillars of parenthood even go so far as to transport their broods to suitable habitat before saying good-bye for good.
This sophisticated behavior complicates the question of how parental care evolved. Usually found in mammals and birds of a particular sex, this type of attention is unheard of in the invertebrate world, let alone in hermaphrodites like leeches.
"Climate Change Shaped Modern Plant Leaves"
Anyone who's enjoyed the shade of a maple or elm should be thankful for an ancient climate shift. According to new research in the Proceedings of the National Academy of Sciences, climate change triggered the development of broad plant leaves.
Instead of wide solar-collecting blades, plants 400 million years ago sported stick-like projections known as microphylls. Microphylls persisted for 20 million years before more photosynthetically efficient broad leaves appeared. Now researchers in the United Kingdom say they can explain the delay. In the high temperatures and carbon dioxide levels of the Devonian, plants could easily collect enough carbon dioxide for respiration using the few pores on their narrow leaves. The scientists' computer model shows that a larger leaf surface area would have overheated the leaf cells.
Then carbon dioxide levels and global temperatures fell 370 million years ago. Larger leaves with more pores were necessary to gather sufficient carbon dioxide. The model shows the plants would also have to have increased the density of their stomata to promote cooling — a trend supported by the fossil record.
Posted by bluprnt at August 11, 2004 05:31 PM