Wild hitchhikers

 

Wild hitchhikers

Wild hitchhikers, is the name I have given to a group of organisms that hitchhike on other organisms to serve themselves. These group of organisms are called parasites. Technically speaking, parasites are helminths (flatworms), arthropods (insects), and protists. Broadly speaking, you can include pathogens (bacteria, viruses), and parasitoids (organisms that kill their hosts, e.g. wasps) as well. A major distinction between parasites and other disease causing agents is that Parasites don't usually kill their hosts, but do harm them in some ways (e.g. make them weaker compared to their counterparts).


The natural world is swamped with these hitchhikers. Isn’t that scary! While it’s not exactly clear how many parasite species there are in total, some believe that upto 40% of all species could be parasitic. What is clear though that parasitic life style is adopted by creatures in over 15 phyla and over 4 of the 7 kingdoms of life. These include kingdoms plantae, animalia, protozoa and fungi. In the animal kingdom, the major recognized parasite groups are the helminths (like round and flat worms), and arthropods (like ticks and insects). 

Hosts 

Parasites need hosts. There are intermediate hosts where the parasite may grow but doesn't reproduce, then there are definitive hosts where the parasite reproduces and completes its life-cycle. There are also reservoir hosts. These are species of hosts that don't get severely unwell from the parasitic infection, and may even be asymptomatic (does not show symptoms), but the parasite can survive and even grow on this host species.For instance, bats are a reservoir host of the novel corona virus.

 
Image by Rebecca Senft
 
One can argue that the same logic can apply to populations within a definitive or intermediate host as not every individual shows symptoms of infection or gets severely ill by a pathogen or a parasite, but may still facilitate the survival and existence of the parasite in the population by acting like a reservoir. These organism are like bridges that connect the parasite to a vulnerable host.


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