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Tommy Leung

Parasitologist, Evolutionary Biologist, Researcher, Lecturer

Parasitologist and evolutionary biologist who also happen to write for a blog about parasites, and likes to draw things sometimes.
I am a biologist who conduct studies on various ecological and evolutionary biology aspects of parasitism/symbiosis. I also write for the Parasite of the Day blog, which I co-administrate with its founder, Susan Perkins of the American Natural History Museum.
Outside of my professional field, my favourite thing to do is drawing - some of which (but not all) are inspired by my scientific work. My drawings can be found on my dA account.

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Date Following Followers Gained
Recent Popular Posts
About 13 weeks ago Of Pigs, Chimps, And Dinosaurs
[Brace yourself, this is a long read]
It seems like ever since mid-2013, not a month goes by without hearing about what I would call "PigChimpMan theory" of human evolution. This "theory" has been lurking around for a while in its own obscure corner of the internet, but it initially came to the attention of a wider online audience via PhysOrg back in July 2013. However, the idea was well and truly launched like a dysfunctional bottle rocket in November 2013 into the mainstream when it was publicised by that bastion of rigorous science journalism, the Daily Mail. Subsequently, it had spread like a pandemic swine flu across other media outlets.

(BTW, I'm not going to link to those pages directly and give them the hits, but if you wish to see them, they can easily be found via a quick Google search)

But we're not here to talk about that, as the ridiculousness of that theory has been thoroughly addressed by +PZ Myers 
About 8 weeks ago Teenage Ninja Turtle Worms
Earlier this week, one of my colleague came across a long-necked turtle ( that had died at one of his field sites. I decided to make the most of the turtle's death by investigating what kind of parasites it might have harboured. After I opened up the body cavity, I found myself staring at a leaf-shaped, mango-coloured worm - it was Gigantolina elongata - and I found 3 of such worms living in the turtle's body cavity, sliding sluggishly between its organs, each measuring about 3-4 centimetres in length

Gigantolina elongata is a species of parasitic flatworm in a group call Amphilinidea ( There are only 8 known species of amphilinids (see this post and they belong to a larger group of peculiar "no-quite-tapeworms" call the Cestodaria.

The Cestodaria is a sister group t
About 7 weeks ago The Kitty's Fiery Serpent
Last year, there was news that the Guinea worm (Dracunculus medinensis) is set to become the second human infectious disease to be eradicated (, and is believed to be the "fiery serpent" described in the Bible, Numbers 21:6-8.
The disease caused by the parasite is agonising and results from drinking water which has been contaminated with copepods (tiny, microscopic crustaceans) infected with the larval stage of the parasite. The adult worm causes intensely painful blisters on the skin which can be alleviated by immersing the afflicted part in water - which is exactly what the worm wants. When one of these blisters burst, larval worms come pouring out of the wound and the fiery inflammation cause by the worm's presence causes the host to immerse the inflicted part in water for relief, which in turn releases the larval worm into the water to infect copepod hosts.

About 12 weeks ago Such Transmissible Cancer. Much Old. So Doge. Wow.
As far as sexually-transmitted diseases goes, Canine Transmissible Venereal Tumour (CTVT) is one hell of a weird one. It is one of only two known lines of cancer cells which actually acts as an infectious agent (the other being the Devil Facial Tumour Disease DFTD see: (For a review of these two clonally transmissible cancers, see:
Whereas there are various other pathogens/infectious agents such as the Human papillomavirus (HPV) which can trigger the growth of cancer, in the case of CTVT, it is the cancer cell itself which is the infectious agent.
Essentially, CTVT is a line of dog cells which have evolved into something that acts like a clonally-reproducing pathogen. Genetic analyses indicates that this cell line originated about 11000 years ago and that this CTVT contains traces of DNA which links it back to th
About 6 weeks ago Hold The Line
So yesterday, David Cameron tweeted a photo of himself talking to Barack Obama on the phone. Next thing you know, this happened.
Storify by +Andrew David Thaler 

About 1 week ago Blue Dragons
Earlier today, I recorded a segment on the local radio about the blue sea slug (listen here: - apologies for the audio quality, there was a technical problem with the recording studio and we had to do it over the phone).
Despite its fantasy-like appearance, the blue sea slug (in the genus Glaucus) is an actual real-life animal. They spend their lives drifting in the open waters of the world's ocean, eating jellyfishes (and sometimes each other). So how do they manage to eat jellyfish without being stung and how does a small, seemingly vulnerable creature like Glaucus protect itself against other hungry animals of the sea? To find out, simply follow this link
#scienceeveryday   #biology   #marinelife   #marinebiology   #seaslug  

About 10 weeks ago Darwin's Frog Rhinoderm darwinii
Rhinoderma darwinii, commonly known as Darwin's Frog is an amphibian from the forest streams of Chile and Argentina. It was originally discovered by Charles Darwin in Chile during his voyage on the HMS Beagle, and was described by French Zoologist André Marie Constant Duméril and his assistant Gabriel Bibron, who named it after Darwin.
This frog is has a unique way of rearing its offspring - the male Darwin's Frog standby and guard the eggs until they hatch, at which point he swallows them and carry them around in his vocal sac until they develop into little froglets, at which point the male basically vomits them out as you can see below.
Earlier this year, I talked about this frog in a lecture as an example of the diversity found in amphibian reproductive strategies. So I was very, very sadden to find out yesterday that Darwin's Frog is now most likely extinct:
About 11 weeks ago The Xenomorph Of The Sea
As previously seen on the Parasite of the Day (, the post written by Katie O'Dwyer - PhD student from University of Otago (katieodwyer00) was selected for republishing at +The Conversation. Follow the link below to read about the crustacean that hollows out its gelatinous host so it can ride the waves in a barrel of semi-living jelly.
#scienceeveryday   #biology   #parasitology   #marinelife   #parasitismeveryday  

About 14 weeks ago I Have A Gut Feeling About This
Locust are well-known for their propensity to swarm. About a month ago, I shared a post about the cues that transform them from subdued, solitary insects into a ravenous horde ( Now, a new study published in Proceedings of the National Academy of Sciences indicates that a microsporidian gut parasite, Paranosema locustae, may also be playing a role in mediating that behaviour ( To find out more, follow the link below. See also this Parasite of the Day post from October 2011 on a fungal parasite of locusts (
#scienceeveryday   #biology   #parasitology   #entomology   #bugseveryday   #parasitismeveryday  

About 10 weeks ago Instincts Make The Dog
This a wonderful post by Professor Malcolm Campbell on what makes a dog different to a wolf.
Among other things, dogs have genes that allow them to digest more starch more easily. While wolves also have genes that encode for starch-digesting enzymes, dogs have more of them, particular those that encode for the enzyme alpha-amylase. As a result, dogs can digest starch far more effectively than wolves. 
At first this seems to support the idea that dogs originated from wolves that hung around and scavenged from farming communities during the time when humans took up agriculture - having those extra starch-digesting genes would have allowed the ancestors of dogs to digest any scraps they found around those settlements more effectively than their relatives which lacked those extra genes.
But while dogs can digest starch far more effectively than wolves, that seems to be something that had only evolved after they were domesticated. Different breeds of dogs vary in the numb