zoo:logic

blue-shark009:

My favorite animal is the water bear! They can survive extreme heat and cold, radiation levels, they can survive hundreds of years without food or water, and they can survive in space!! I think water bears beat koalas Hands down!

Ah, finally someone with a more unconventional favourite! And what a fabulous choice. There are hundreds of reasons why water bears (Tardigrada) are amazing animals. Tardigrades (meaning “slow walker” in Latin) are a phylum of over 1000 different species that are found everywhere in the world - from Himalayan peaks of over 6000 metres to ocean depths below 4000m, from icy polar regions to the heat of the tropics, in freshwater, saltwater and damp terrestrial habitats. If you’re wondering why such an abundant creature has so far escaped your notice, it’s because they are at their greatest 1.5mm and at their smallest, just 0.1mm long. But don’t dismiss them yet - they are most certainly one of the cutest and most interesting microscopic organisms out there!

Water bears have a body with four segments and four pairs of lobopodial (unjointed) legs each bearing a set of 4-8 little claws. They feed using a stylet, or small tube, with which they pierce plant or animal cells and then suck up the internal fluids. Of the many species of water bear, some are purely carnivorous, consuming bacteria, rotifers or other tardigrades, some are omnivorous, and some are herbivorous, eating only plant materials.

The most famous and interesting characteristic of water bears is that they can enter a state known as cryptobiosis if environmental conditions become insufficient to live in. In cryptobiosis, the tardigrade dries up into a form known as a ‘tun’ (containing less than 1% water) and its metabolic rate drops to a hundredth of a percent of its normal rate or may even be completely undetectable. It can remain like this for up to 100 years and only takes a few minutes to come ‘back to life’ once returned to favourable conditions! Cryptobiosis has a number of different triggers that activate slightly different pathways. These are drastic changes in water solute content such as ion concentration (osmobiosis), drought (anhydrobiosis), extreme temperatures (cryobiosis) or lack of oxygen (anoxybiosis). In their natural environment, the most common form of cryptobiosis is anhydrobiosis, but we’ve conducted all sorts of crazy experiments to see what else they can survive. They have sailed through several minutes at 151ºC, and several days below -200ºC. They can withstand extreme radiation at levels that would be lethal to almost all other animals. And tardigrades have even ventured into space, surviving 10 days of vacuum and cosmic radiation with 68% still retaining the ability to live and reproduce (the project is called TARDIS which just makes it all the better). Not only can they survive very low pressures as in the vacuum of space but also very high pressures, more than 1200 times greater than atmospheric pressure!

Finally, as with any great character the water bear even has its own cuddly toy. What more could you want from a favourite animal?!

Ref: Shifflett B. M., 2008. Tardigrades. University of Wisconsin Organismal Biology [link]
Lindahl K. & Balser S., 1999. Tardigrade Facts. Illinois Wesleyan University [link]
Goldstein B. & Blaxter M., 2002. Tardigrades. Current Biology 12(14):475. [link]
Wikipedia

skaterboytae:

When a honeybee dies it releases a death pheromone, a characteristic odor that signals the survivors to remove it from the hive. This might seem a supreme final act of social responsibility. The corpse is promptly pushed and tugged out of the hive. The death pheromone is oleic acid [a fairly complex molecule, CH3(CH2)7CH=CH(CH2)7COOH, where = stands for a double chemical bond]. 

What happens if a live bee is dabbed with a drop of oleic acid?

Then, no matter how strapping and vigorous it might be, it is carried “kicking and screaming” out of the hive. Even the Queen bee, if she’s painted with invisible amounts of oleic acid, will be subjected to this indignity.

Do the bees understand the danger of corpses decomposing in the hive? Are they aware of the connection between death and oleic acid? Do they have any idea what death is? Do they think to check the oleic acid signal against other information, such as healty spontaneous movement? The answer to all these questions is, almost certainly, No. In the life of the hive there’s no way that a bee can give off detectable whiff of oleic acid other than by dying. Elaborate contemplative machinery is unnecessary. Their perceptions are adequate for their needs.

Ann Druyan & Carl Sagan, Shadows Of Forgotten Ancestors: Who Are We?, What Thin Partitions 

When we think of parental care, the most obvious aspects that spring to mind are the provision of food and the protection of offspring from predators. However, parental care is widely varied across species and can encompass protection from a broad range of other environmental threats including competition, parasitism and disease. The burying beetle Nicrophorus vespilloides is one such species that has recently been found to display a particularly interesting method of parental care. Larvae of this species are reared on the carcasses of small vertebrates, which are lovingly prepared for them by their parents who bury the carcass, roll it into a ball and remove any fur or feathers before finally covering it in a combination of oral and anal secretions. These substances are assumed to protect the carcass from microbial decomposers that would compete with the beetle’s offspring for food. However, the exact mechanism of how the secretions work has previously been poorly understood. Recent research has now revealed the nature of an anal secretion that is regularly secreted from the parent to the carcass: it is a highly bactericidal lysozyme, meaning it acts to break down peptidoglycan, a polymer that makes up the bacterial cell wall. This then leads to cell lysis - breakdown of the cell as a whole, resulting in cell death, specifically of gram-positive bacteria. Production of the lysozyme secretion corresponds with when it will be needed, increasing rapidly in adult females after discovery of a carcass, before peaking during the period of parental care and dropping again after the offspring have dispersed. The lysozyme secretion increases offspring survival by almost double, making it an essential part of parental care for Nicrophorus vespilloides.

Ref: Arce A. N., Johnston P. R., Smiseth P. T. & Rozen D. E., 2012. Mechanisms and fitness effects of antibacterial defences in a carrion beetle. Journal of Evolutionary Biology 25(5): 930-937. [link]