Tuataras: The Living Fossil

The Tuatara: The Living Fossil on Prezi

U.N. reports Decrease In New HIV Infections.

Fewer people are being infected with HIV, the virus that causes AIDS, then at the epidemics peak, but progress is still halting and fragile. 2.6 million people were infected in 2009, 20 percent fewer then in the late 1990's. Although about 25 countries are doing better at prevention, including a few in south africa, (high in aids rates) the progress is still spotty.

South Africa, home of the worlds worst AIDS epidemic, benefited from the change in president from Thabo Mbeki, hostile in distribution of AIDS drugs, to Jacob Zuma, who publicly took an AIDS test, urging citizens to do the same. Although south africa still faces 350,000 to 500,000 infections per year, there has been much improved progress to give mother drugs to prevent infection of babies trough breaks milk. Acording to Michael Saibe, executive director of UNaids, there has been a 50% reduction of young deaths in south africa. Some reasons for this are: parents and children are discussing sexuality more, and people are sleeping around less. When 57 countries were surveyed, only 25% said that they had had more then one partner in the last year.

Despite progress being made, some countries, mostly in Western Europe and Central Asia, are becoming worse, where the epidemic on concentrated in heroin- injectors and their sexual partners. The more the heroin spreads the more addictions there are and therefore, resulting in more HIV infections.

There is good and bad news on the treatment front. 5.2 million people are getting antiretroviral drugs, more then there has ever been before; however 10 million people still need immediate treatment. It has been 3o years since the start of the AIDS epidemic and about 33.4 million people are living with HIV. A comparison shows how much progress needs to be done before we can say the world is winning the war on aids: for every 100 people put on treatment, 250 become newly infected. Now it is about 200 become newly infected. It is a small improvement, but an improvement none the less.

Link to Original Article: http://www.nytimes.com/2010/11/24/world/africa/24infect.html?partner=rss&emc=rss

Osmoregulation in Marine Reptiles

Marine Reptiles consist of animals like crocodiles, sea turtles, marine iguanas, marine snakes. Marine Reptiles have inherited or retained the osmotic concentration of bodily fluids of about 300-350 mOsm (milliosmole), therefore they are hyporegulators.

Marine Reptiles differ from fish or amphibians because they only use their lungs. Lungs don't come in contact with water so they have developed a respiratory epithelium. The epithelium is thin and highly permeable to gasses. The skin is thick and reduces permeability to water. Nonetheless, no epithelial is entirely impermeable to water and marine reptiles still lose some water through their integument to the seawater. Thinner epithelia covering the mouth, nasal passages, and eyes are sites of osmotic water loss.

Despite the relative impermeability of skin, reptiles still face a substantial osmotic load. If they feed on fish, they have food source with an osmotic concentration isosmotic to their own blood. It is likely that they will ingest at least small quantities of seawater with he fish as the capture and eat them.  Other food sources in the sea are osmoconformers and eating them is equivalent to drinking salt water. This poses problems for crocodiles, feeding on crabs, turtles, feeding on jellyfish, and marine iguanas, feeding on algae.

Marine Reptiles maintain osmotic homeostasis by excreting a hyperosmotic, sodium chloride-rich fluid from their bodies in the surrounding waters. This is carried out by a epithelia in the head region. Crocodiles have glands in the tongue that can secrete hyperosmotic fluid. In sea turtles, it is carried out by the lacrimal (tear) glands surrounding the eye. In marine iguanas, nasal glands are the site of active salt transport. The situation with marine snakes is a bit more uncertain.