Wednesday, March 28, 2012

Primate communication in the pure ultrasound

This study published last month sheds new light on ultrasonic communication. Frequencies above 20 kHz, the human boundary for hearing, are classified as ultrasonic. While some primates have been known to emit partially ultrasonic vocalizations, there has been little evidence of purely ultrasonic primate communication. In the study, the auditory brainstem response (ABR) method was used to estimate auditory sensitivity in six Philippine tarsiers (T. syrichta). Additionally, the calls of 35 wild tarsiers were recorded with an ultrasound recording unit. The tarsiers' high frequency auditory limit was estimated to be 91 kHz, shattering the primate record of 65 kHz in the bush baby. Moreover, eight individuals' vocalizations were determined to be purely ultrasound. These results suggest that T. syrichta can communicate purely in the ultrasound, which may allow for private communication undetectable to predators, prey, or competitors.

Taste clustering in humans and primates

Are there relationships between types of human taste thresholds? This study looked at previously recorded impulses on isolated taste fibers during tongue stimulation of primates to see if there was a correlation between electrophysiology in primates and humans. The highest correlations between tastes were for the sugars and quinine hydrochloride/tannins. These two taste classes, which were grouped into “pleasant” and “unpleasant” clusters, are common to humans, chimpanzees, macaques, and marmosets. The various salts and acids cluster found in this study was not found to be shared by previously recorded primate species.
These two broad clusters of pleasant and unpleasant tastes are thought to represent major selective pressure on the primate gustatory system. The low thresholds for sugars and high thresholds for quinine and tannin could indicate the evolution of optimal feeding strategies to maximize nutritional intake and avoid toxic substances.

Flavor trip level: salad

This group of researchers figured out how to express miraculin in transgenic lettuce. Miraculin is the protein produced by Richadella dulcifica, the West African shrub that grows our flavor-tripping berries. They were able to place a synthetic gene coding for miraculin under constitutive promoter control, and then transferred the package to lettuce. This made the transgenic lettuce express miraculin protein in its leaves! They didn't say whether it also made everything else you eat taste sweet also. My bet is yes. Talk about GMOs, can't wait to hear the food co-op's official take on these babies!

Olfactory senescence

Ah, the joys of senility. Apparently, this now includes eating spoiled food and the inhalation of toxic vapors. A study comparing olfactory sensory neurons (OSN) in subjects 45 or younger and 60+ found that OSNs in younger subjects exhibited highly specific responses to two distinct odours, while those in the elderly subjects were more likely to respond to multiple odor stimuli indicating a loss of specificity. Interestingly, OSN density was comparable between the two groups. This means that loss of specificity in OSNs from older subjects may contribute to smell loss and the inability to differentiate between smells. Since smell is so intimately linked to taste, this could also result in decreased tasting abilities.

Using parasites to infer social networks of Microcebus

A fresh article on the use of parasites in studying social structure and behavior in a wild population of mouse lemurs! This study tagged parasitic louse on captive lemurs using colored nail varnish and analysed transferance rates as a proxy for frequency of social interactions. Very cool. Here's the ScienceDaily snack-size version:

Tuesday, March 27, 2012

Major taste loss in carnivorous mammals

This article, which came out today, is a follow-up on work done on the pseudogenization of the Tas1r2 gene in felines. The authors expanded their study to 12 other species in the order Carnivora. The pseudogenization of Tas1r2 gene, which codes for the Tas1r2 receptor, causes organisms to lose the ability to taste sweet compounds. Seven out of the 12 species studies had also independently pseudogenized this gene. All seven of these species are also strict carnivores, including species as diverse as sea lions and otters. The authors conclude that this loss in taste receptor function is an adaptive response to feeding behavior.

Wednesday, March 21, 2012

A relationship between neocortex size and tactical deception in primates

The “Machiavellian intelligence” hypothesis states that intense social living, which is exhibited in certain species of primates, leads to selection for increased social skill, which is a function of neocortical enlargement. Neocortex size has been found to vary with different types of mating systems and social group size, and thus it is hypothesized that there is a social origin for the neocortical enlargement of primates dependent on the degree of social manipulation and inter-group competition.
This study looked at absolute neocortex volume and the ratio of neocortex volume to the remainder of the brain in 18 species of the major primate groups. Social cognition was measured as “tactical deception,” in which primates exhibited manipulative behavior of others within the social group without the use of force. Absolute neocortex volume was found to be a reliable predictor of the use of deception; however, there was no significant correlation between the use of deception and social group size, in contrast to the results of previous studies. The authors concluded that primate tactical deception is generally a function of rapid and extensive learning in monkeys and prosimians, and is only based on understanding of mechanism in a few records of great apes. Thus, the learning ability of primates seems to be dependent on neocortical enlargement, which is subject to the selective pressures of social sophistication.

Genetics of Physical Activity and Physical Inactivity in Humans

Recent studies have suggested that physical activity (PA) and physical inactivity (PI) may not only be affected by psychosocial and environmental factors, but also may be two phenotypes with genetic mechanisms. This review published online just last week in Behavior Genetics compiles such data available to date from 45 previous studies, including twin, family, linkage and association studies as well as one GWA study. In order to be included in the review, the studies needed to provide information on heritability estimates, linkage results, or identified genes and markers. The most significant finding associated Gln223ARrg, MC4R and DRD2 genes with the PA phenotype.

OXTR and Trust

This study looking at 108 adult (human) males found a reliable association between a SNP (G) in the OXTR gene and trust behavior. Individuals homozygous (G/G) for the SNP exhibited greater trust behavior as compared to heterozygous (G/A) or homozygous for A (A/A). It's unclear what functional effect this SNP may have and more research on how OXTR interacts with other genes/environment will be necessary to make this a robust relationship.