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I've decided to draw another entry for 's All Yesterday contest here: nemo-ramjet.deviantart.com/art…

This is far less elaborate than my previous two All Yesterday pieces (the-episiarch.deviantart.com/a… and the-episiarch.deviantart.com/a… but it does based a theme which is not frequently explored in paleo-reconstruction, but is very commonly found in nature: disease and parasitism.

This was inspired by a recent study published in PLoS One which reported fossils of tapeworms eggs in shark coprolite dating back to the Permain period, showing that tapeworms have been around for a very long time (I posted about it here: plus.google.com/u/0/1114796472… , not to mention that they have also been parasites of sharks for a very long time as well (for more on *living* shark parasites, see these posts on my blog here: dailyparasite.blogspot.com.au/… . Knowing how the life-cycles of shark tapeworms go, the shark is infected by consuming prey animals which are infected with the larval stages of the tapeworm (an organism infected the larval stage of a parasite is also known as an "intermediate host"). It is almost certain that how the shark that left behind those fossilised poop was infected, when it ate an infected prey.

My drawing depict one of those potential prey/intermediate host - a school of conodonts. The focal individual near the centre of the drawing is heavily burden by cysts resulting from being infected by multiple tapeworm larvae. As well as being a burden, the tapeworm also does two things to its host - it induces deformities in the host's spine which cripples it further (making it an easier prey for the parasite's next host), and it also manipulates its body pigment so that it would stand out from the rest of the school. All of the above enhances the parasite's chances of ending up in the gut of a shark.

All this is inspired by actual living examples. On my blog I have written about a parasitic fluke call Telogaster which induces spinal malformation in the little freshwater fish that it infects (dailyparasite.blogspot.com.au/… and make it more susceptible to predators. Other parasites can also interfere with the physiology of their host and induce striking colour changes, such as this nematode which alters the colour of an infected ant's abdomen to make it resemble a berry: www.canopyants.com/2008_AmNat.…

And with these type of host manipulation, the more parasites there are, the stronger the effect, thus there are two condonts in the drawing which only have a few cysts, but have yet to display the symptoms of colour change and spinal deformities in the heavily infected individual. It also reflects the natural pattern of distribution in macroparasite (worms, fleas, lice - multicellular parasites basically) populations, in that there are a few heavily-infected individuals, but most individuals in a population are either not infected or only lightly infected with parasites.

Description
I've decided to draw another entry for 's All Yesterday contest here: nemo-ramjet.deviantart.com/art…

This is far less elaborate than my previous two All Yesterday pieces (the-episiarch.deviantart.com/a… and the-episiarch.deviantart.com/a… but it does based a theme which is not frequently explored in paleo-reconstruction, but is very commonly found in nature: disease and parasitism.

This was inspired by a recent study published in PLoS One which reported fossils of tapeworms eggs in shark coprolite dating back to the Permain period, showing that tapeworms have been around for a very long time (I posted about it here: plus.google.com/u/0/1114796472… , not to mention that they have also been parasites of sharks for a very long time as well (for more on *living* shark parasites, see these posts on my blog here: dailyparasite.blogspot.com.au/… . Knowing how the life-cycles of shark tapeworms go, the shark is infected by consuming prey animals which are infected with the larval stages of the tapeworm (an organism infected the larval stage of a parasite is also known as an "intermediate host"). It is almost certain that how the shark that left behind those fossilised poop was infected, when it ate an infected prey.

My drawing depict one of those potential prey/intermediate host - a school of conodonts. The focal individual near the centre of the drawing is heavily burden by cysts resulting from being infected by multiple tapeworm larvae. As well as being a burden, the tapeworm also does two things to its host - it induces deformities in the host's spine which cripples it further (making it an easier prey for the parasite's next host), and it also manipulates its body pigment so that it would stand out from the rest of the school. All of the above enhances the parasite's chances of ending up in the gut of a shark.

All this is inspired by actual living examples. On my blog I have written about a parasitic fluke call Telogaster which induces spinal malformation in the little freshwater fish that it infects (dailyparasite.blogspot.com.au/… and make it more susceptible to predators. Other parasites can also interfere with the physiology of their host and induce striking colour changes, such as this nematode which alters the colour of an infected ant's abdomen to make it resemble a berry: www.canopyants.com/2008_AmNat.…

And with these type of host manipulation, the more parasites there are, the stronger the effect, thus there are two condonts in the drawing which only have a few cysts, but have yet to display the symptoms of colour change and spinal deformities in the heavily infected individual. It also reflects the natural pattern of distribution in macroparasite (worms, fleas, lice - multicellular parasites basically) populations, in that there are a few heavily-infected individuals, but most individuals in a population are either not infected or only lightly infected with parasites.