How Cold is Too Cold for Isopods?

 Isopods come from almost every environment you can imagine. This means that different species may have different needs. Including their temperature range.

Isopods are ectothermic, so they can not generate their own body heat, unlike you or I. Meaning they have to practise behavioural thermoregulation. In general, this means they will move to warmer or colder areas to regulate their body temperature. Isopods are one of few if not the only crustaceans to make the jump permanently from the sea to the land. In the oceans, and any large water body temperatures are consistent, meaning that for land-based isopods they haven't evolved to be able to maintain their own temperature, or to be able to survive extremes of temperature.

How long is too long?

 There is an important distinction to make here. By too cold are we talking one night when the heating failed, or regular temperatures? They are very different things. Add humidity to the mix and you’ve got a complex interaction. Cold air is drier than warm air, even if the percentages look the same.

 Ideally, you want to mimic the microhabitat of your isopod's natural range. It's fine to look at the range of temperatures in say Thailand, but those aren't the same temperatures as an isopod would experience in a small rainforest type environment in the mouth of a cave.

How do they keep warm?

 A primary way of staying warm is conduction between themselves and the surface they're standing on. For reptiles, we tend to discuss the heat transfer from infrared radiation, but this relies on them being out in the open and basking. Many species of isopods don't spend a lot of time out in the open, instead, they will be under cork bark or in the leaves.

Air temperature is important, if it is too cold they will lose heat faster than it can transfer from the substrate. So it’s important to consider all aspects of the temperature. Including the fact that if it’s too cold they will burrow into the substrate to help preserve some heat.

 Studies on isopods and temperature

Studies on Porcellio scaber show that the growth of mancae, young isopods, at 15ºC was slower than at 22ºC but that their adult size was larger. At intermediate temperatures some toxins were safer, or at least less fatal. However at extremes of temperature there were more issues with bioaccumulation of toxins such as heavy metals.

 As the temperatures drop isopods are shown to be slower when running, which makes sense given that their systems rely on external heat to keep things moving.

 An interesting study showed that isopods that were exposed to fluctuating temperatures were more resilient than those maintained at a constant temperature. The temperature didn't fluctuate more than a few degrees in each direction, but it shows there is no harm in a degree or two drop each night.




Cold vs. Temperate vs. Tropical


 In a fair number of animal-keeping hobbies, we lump everything into three categories, cold, temperate and tropical, and isopods are no different. But the latter two only refer to locations on Earth. Not to temperatures. Peru is most definitely in the tropics, but parts see temperatures dip close to freezing of a night for a good portion of the year. Meanwhile temperate Australia can see temperatures that make the tropics look chilly.

 In isopod keeping we only tend to worry about tropical and temperate. In general tropical species need higher, and more stable temperatures, temperate species will see a greater variation in temperature in the wild, and true cold species will see less variation, and yes cooler temperatures.


What is the best temperature for isopods?

  There are too many isopods to mention here, but most species will thrive somewhere in the range of 20-27º, check out our shop for details on the best temperature for each species.

Some species can survive much lower temperatures, as low as 10ºC, and some even lower. So if the heating goes off for a night in your house your colony may survive unscathed depending on the species. However the activity of the colony will slow down, and breeding may stop. This excess stress may cause other issues down the line, so keep a careful eye on things.


Temperature Requirements of Common Isopod Species

Tropical Isopods (Heat-Loving, Cold-Sensitive)

Temperate Isopods (More Adaptable, but Prefer Warmth)

  • Porcellionides pruinosus (Powder Blue, Powder Orange, etc.)

    • Optimal: 70-80°F (21-27°C).

    • Too Cold: Can survive down to 50°F (10°C).

  • Armadillidium vulgare (Magic Potion Isopods)

    • Optimal: 65-75°F (18-24°C).

    • Too Cold: Can tolerate down to 40°F (4°C)

  • Porcellio scaber (Dalmatian, Orange Koi, etc.)

    • Optimal: 65-75°F (18-24°C).

    • Too Cold: Can survive brief drops to 35°F (2°C).

Cold-Tolerant Isopods (Can Survive in Cooler Conditions)

  • Armadillidium nasatum

    • Optimal: 60-75°F (16-24°C).

    • Too Cold: Can survive 35-40°F (2-4°C)

  • Armadillidium gestroi

    • Optimal: 65-75°F (18-24°C).

    • Too Cold: Below 40°F (4°C) l

  • Armadillidium klugii ("Clown Isopod")

    • Optimal: 65-75°F (18-24°C).

    • Too Cold: Can tolerate down to 40°F (4°C)  

How to Protect Isopods from Cold Temperatures

Keeping an unheated isopod enclosure warm enough


 You might be relying on the general room temperature to keep your isopods warm enough. But what happens if the heating goes out?

As soon as you realise put something over the enclosure to keep any remaining warmth in. A few towels or similar are a great option. If you have access to warm water fill a container with hot water and put that under the towels etc. to add some warmth to the enclosure.


Keeping a heated isopod enclosure warm enough


 If you have a heated enclosure and the heat source fails you can do the same, if the house heating is still on consider moving them to a warmer room. I find the shower room in my house is always a few degrees warmer than the rest of the house. There may be a similar space in your home.


Avoid keeping your isopods in drafts, or at the other extreme in direct sunshine. Extreme heat is as bad as extreme cold. Try and mimic what they would have in the wild, but avoid the extremes at either end and don't forget that the climate has changed in the past century.



Further Reading

Abdel‐Lateif, H M, et al. “Interaction between Temperature and Cadmium Toxicity in the Isopod Porcellio Scaber.” Functional Ecology, vol. 12, no. 4, 1 Aug. 1998, pp. 521–527, besjournals.onlinelibrary.wiley.com/doi/10.1046/j.1365-2435.1998.00227.x, https://doi.org/10.1046/j.1365-2435.1998.00227.x. Accessed 5 Feb. 2025.

Dailey, Tara M, et al. “The Effects of Temperature, Desiccation, and Body Mass on the Locomotion of the Terrestrial Isopod, Porcellio Laevis.” Comparative Biochemistry and Physiology Part a Molecular & Integrative Physiology, vol. 153, no. 2, 12 Feb. 2009, pp. 162–166, pubmed.ncbi.nlm.nih.gov/19535030/, https://doi.org/10.1016/j.cbpa.2009.02.005. Accessed 5 Feb. 2025.

Schuler, Matthew S., et al. “Isopods Failed to Acclimate Their Thermal Sensitivity of Locomotor Performance during Predictable or Stochastic Cooling.” PLoS ONE, vol. 6, no. 6, 17 June 2011, p. e20905, pmc.ncbi.nlm.nih.gov/articles/PMC3117853/, https://doi.org/10.1371/journal.pone.0020905. Accessed 5 Feb. 2025.

Terézia Horváthová, et al. “Does Temperature and Oxygen Affect Duration of Intramarsupial Development and Juvenile Growth in the Terrestrial Isopod Porcellio Scaber (Crustacea, Malacostraca)?” ZooKeys, vol. 515, 30 July 2015, pp. 67–79, zookeys.pensoft.net/article/5768/, https://doi.org/10.3897/zookeys.515.9353. Accessed 5 Feb. 2025.

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