14 DAY TRIAL // Experts have just discovered the first placental mammal capable of detecting electrical fields, the common Guiana dolphin. Instances of electrical field detection abilities are well documented in lesser species, but this is the first time such a sixth sense was discovered in a mammal as advanced as this.
According to researchers, the trait must be an evolutionary adaptation to the murky coastal waters this species usually inhabits. This ability could be making it easier for the dolphins to find their prey.
A placental mammal, researchers explain, is an animal that gives birth to live offspring, which it then nourishes. Until now, no creature in this group has ever been demonstrated to be capable of sensing electrical fields.
In order to conduct the new investigation, researchers at the Rostock University, in Rostock, Germany, turned to assistance from the Dolphinariumin Münster. A Guiana dolphin had recently died here, and the researchers carried out their investigation on the carcass.
What experts were especially interested in were specialized pores called vibrissal crypts. Other species have them as well, but the difference is that all other animals have whiskers too. These structures have evolved in the common ancestor of many species, and are usually found at the base of whiskers.
Over millions of years of divergent evolution, Guiana dolphins lost their whiskers, but retained these specialized structures, which are extremely useful for detecting movement in surrounding waters.
“Most of the animals which [can sense electrical fields] do this to find prey. All of the dolphins' prey items, like crayfish, all of them generate electric fields to some degree,” RU investigator and study researcher Wolf Hanke explains, quoted by LiveScience.
A common dolphin's snout carries between 2 and 10 vibrissal crypts. In the specimen the team analyzed, experts found that the structures were surrounded by nerve endings, as well as very simplified blood vessels.
Additionally, the pores were filled with an interesting matrix of proteins and cells, that enabled them to produce a gel-like chemical. In order to test whether the structures enabled dolphins to actually detect electrical fields, the team trained a live dolphin to detect the fields.
The animals was given a treat every time it sensed such a field correctly. Interestingly, dolphins were able to detect even low-level electrical fields of about 5 microvolts per centimeter. This is way lower than what typical electric fish produce.
Details of the new investigation appear in the July 26 issue of the esteemed scientific journal Proceedings of the Royal Society B: Biological Sciences.