Tag Archives: cats

Cat-handedness: can cats be left- or right-handed?

by Piter Kehoma Boll

In humans, as you may know, there is usually a preference for using one side of the body to perform a task, a thing called laterality. And we have a strong tendency to be right-handed, with about 90% of humans using their right side to perform most unilateral tasks. Several studies revealed that many other animals, at least among vertebrates, display laterality as well.

A recent study investigated laterality in the domestic cat during spontaneous behaviors in contrast with the more common experiments using forced behaviors, such as making the cat try to reach food. They looked for a side preference in cats during the behaviors of lying side, stepping down and stepping over.


Photo by Juan Eduardo de Cristófaro.*

The result indicated that about one third of the cats is left-pawed, one third is right-pawed and one third is ambidextrous while moving up and down, but there is no clear preference for lying on their right or left side. Thus, we can see that, differently from humans, there is no strong bias to use one side of the body in cats, at least not when looking at cats in general.

When we consider sex, though, there was a significant difference: male cats tend to be left-pawed, while female cats are usually right-pawed. That would be very useful if cats danced the waltz.

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McDowell, L. J.; Wells, D. L.; Hepper, P. G. (2018) Lateralization of spontaneous behaviours in the domestic cat, Felis silvestris. Animal Behavior135: 37–43. https://doi.org/10.1016/j.anbehav.2017.11.002

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*Creative Commons License
This work is licensed under a Creative Commons Attribution 2.0 Generic License.


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Filed under Behavior, mammals

Friday Fellow: Toxo

by Piter Kehoma Boll

If I had to bet on a parasite that you who are reading this probably have in your body, I’d go for today’s fellow, the protist Toxoplasma gondii, sometimes simply called toxo.

Found worldwide, the toxo is one of the most common parasites in humans, with estimations that about half of the world’s population is infected. Fortunately, this creature usually occurs in a latent form and does not offer great risks, but eventually it may develop into a more serious condition called toxoplasmosis, especially in people with weakened immunity.

But let’s take a closer look at this tiny fellow.


Oocysts of Toxoplasma gondii. This is the form found in the environment and that can start an infection in your body.

The toxo is a protist belonging to the phylum Apicomplexa, a group of parasitic alveolates that also includes the agent that causes malaria. Although traditionally considered a protozoan, the apicomplexans are closely related to dinoflagellates (which are generally considered as a group of algae). They have a unique organelle called apicoplast, which they use to penetrate a host cell. The apicoplast is derived from a plastid (such as the chloropast), so in a certain way we can say that the apicomplexans are algae that evolved into intracellular parasites!


Tachyzoites of Toxoplasma gondii stained with Giesma from the peritoneal fluid of a mouse.

The life cycle of the toxo is kind of complex. Let’s start with the inactive form called oocyst, which may be found in the environment. If a warm-blooded animal ingests an oocyst, it will “burst” inside the gut of the animal and release several “quick-moving” forms called tachyzoites. The tachyzoites invade almost any cell of the body and multiply asexually inside it until the cell dies and release them, allowing them to infect more and more cells. When invading the brain, liver and muscles, the tachyzoites usually differentiate into cysts that become inactive. In this stage, the only thing that the toxo wants is that a cat (any species of the family Felidae) eats the host. It may even change the host’s behavior in order to make it bolder and more easily accessible to predators.


A cyst of Toxoplasma gondii that forms in the muscles, brain and liver of any warm-blooded anymal. All the cyst wants is to be eaten by a cat!

Now let’s assume that a cat ate the host (that was likely a bird or mouse). Inside the cat’s gut, the cyst burst and releases several “slow-moving” forms called bradyzoites. This form invades the epithelial cells of the cat’s intestine and multiply asexually inside them. Eventually, the bradyzoites differentiate into either tachyzoites or gametocytes (sperm- and egg-like cells). When two gametocytes fuse, they form a zygote that matures into an oocyst and is released into the environment, restarting the cycle.


The complex life cycle of Toxoplasma gondii. Credits to Mariana Ruiz Villarreal.

As always, the lifecycle of parasites is a wonderful adventure!

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Tenter, A., Heckeroth, A., & Weiss, L. (2000). Toxoplasma gondii: from animals to humans International Journal for Parasitology, 30 (12-13), 1217-1258 DOI: 10.1016/S0020-7519(00)00124-7

Wikipedia. Toxoplasma gondii. Available at <https://en.wikipedia.org/wiki/Toxoplasma_gondii&gt;. Access on March 6, 2017.

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Filed under Disease, Friday Fellow, protists