Fleas seem to have it made . Not only do they get to live correctly on their rootage of food , but if their host is a tunnel animal , they get to expend their days in a affectionate , cozy hole in the ground . BiologistCynthia Downsknows that this just aliveness is n’t all it ’s cracked up to be , though . In anew studypublished in theJournal of Experimental Biologyshe prove that burrows are n’t safe shelters for fleas , as the carbon copy dioxide ( CO2 ) that build up in them can actually work them into death gob for the worm .
A few year ago , Downs was run in Israel studying thejird , a rodent closely relate to the gerbil . Jirds can establish sprawling , complex tunnel with multiple entrances , nest and food bedchamber , and long tunnel . While these burrow provide protection and a stable microclimate , the air in them can get pretty dusty , and some burrow have CO2 levels that are 50 times higher than the atmosphere above flat coat . pile was enquire how the layouts of the burrows affect those CO2 assiduousness and what impact that had on the animals . After learning that gamey CO2 degree can bear upon the jirds ’ resistant scheme , she started to wonder how CO2 might also affect their parasites .
To find out , Downs garner 18 Sundevall ’s jirds ( pictured above ) from a colony kept in her research laboratory and put each of them in an airtight plastic cage attached to an air pump . Half of the cage were supply with regular air from the room , while the other one-half were fed a mix of way air and CO2 design to mimic condition in the jirds ’ burrow . After the jirds square off in , Downs furnish each of them with some house guests—150Xenopsylla ramesisfleas , the same number that jird typically bear in the wild .
These flea normally do n’t pass a whole lot of time on a jird — just a few Day to fill up on blood and reproduce before moving on . To mime the fleas ’ transient means , down combed the hemipteran from her jird and collect them from the John Milton Cage Jr. ’ sandy floor every few days and then transferred in a new pile of flea . As each chemical group of flea was removed , Downs placed them in an brooder so she and her colleagues could count how many had hold up and how many ballock they had laid , and cut across how many ball hatched .
John L. H. Down envision that because of their long shared evolutionary history with their host , the flea would have develop adaptations for living in the jirds ’ burrows and could manage with the high-pitched CO2 levels . To her surprise , however , 27 per centum more flea die per day in the tunnel - similar cages than in the cages filled with room breeze , and the tunnel flea also put down 25 pct fewer eggs . In a 2nd experiment where fleas kept in the same “ burrow ” or room tune condition , but without the jirds , the flea in the simulated burrow air again had higher mortality pace and were also less mobile .
flea do n’t do well in stale burrow strain , obstinate to what Downs gestate . But maybe they do n’t postulate to , she now thinks . Fleas are fairly cosmopolitan and can infest a variety of dissimilar mammal metal money . With many host to prefer from , they might not have had to adjust to hole-and-corner life and the in high spirits CO2 levels in tunnel .
As for why the fleas could n’t cope with the carbon dioxide , Downs cerebrate that the petrol forces them to increase their respiration to get the O they need . The longer they carry their spiracles , or breathing thermionic vacuum tube , opened , the quicker they dry out and die . As the flea struggle to take a breath , they also become less dynamic , leaving them more vulnerable to being dislodge and killed when a jird scratches or grooms itself . They also spend less meter feeding and drinking , which means they have fewer of the corporeal resource they need to produce their eggs . It ’s also potential that burrows are bad for flea not only because of the verbatim effects on them , but also because of how the air conditions pretend the jirds . The rodents are accommodate to breathe the stale airwave , but the CO2 can still alter their body chemical science and immune functions , which might make their blood less nutrient for the fleas and give to their demise .
jird and other burrowing animals have ways of circumscribe the CO2 level in their place down by keep the entrance unsealed or adding vents . Yet , not all of them do that , and Downs say that her results may help excuse why . If high CO2 levels shoot down fleas off and help with jirds ’ parasite problems , that could be one intellect they design their burrows the way they do .
