This blog is going to discuss our recommended care for giant isopods. When we say “giant isopods”, we are specifically referring to the giant Porcellio found around Spain, Greece, and nearby areas. Some Porcellio species reach sizes of over 20 cm, widths of over 10cm, and display a variety of vivid colors. These isopods have begun to be cultured with increasing success over the last few years and have been gaining traction and popularity in the hobby.
Although more people are having success than before, keepers are still having issues and we hear about it far too frequently. The number one issue we notice is that these animals are being kept far too dry. It is a common misconception that the giant Porcellio are “dry” species, but all isopods need some access to moisture to thrive. Isopods breathe through pleopodal lungs – the white spots on their undersides are adapted gills. These “lungs”, although external, need to be moist to function correctly. If there is not enough moisture in the environment, the moisture is pulled from the isopod’s body and the animal can dry out very quickly.
Some Porcellio need more access to moisture than others. Magnificus, for example, is one of the isopod species that we keep truly dry. Spatulatus and P. wagneri are the other two species we keep dry. All other species of isopod we offer a minimum of 30% moist setups. For these “dry” species, we have a substantial amount of moss placed in the corner. Rather than misting an entire section of setups, the moss in the damp corner has water added to it directly. This moss must never dry out completely, because if it does, the isopods will die. Low moisture does not mean no moisture. If the deaths are uniformly expressed in males, females, and young, the setup is likely too moist.
For the other giant Porcellio, such as expansus, hoffmannseggi, ornatus, and bolivari, we offer a setup that is 30% to 50% moist. Many of these species are native to cliffsides of Spain – which means they are in an area that both has high airflow and moisture, as these are cliffsides of the sea. Bolivari and nickelsi are natives to caves of Spain which also have high airflow and even higher moisture. Males have been noted to prefer the dry side, but gravid females and juveniles are always deep in the moist dirt. Without adequate moisture, a female will typically perish after birthing, and an incredibly low percent of the brood survives (this may be both due to a difficult birth and not having a mother to care for them.) Juveniles are less likely to thrive in a low moisture environment, so fewer individuals reach adulthood. If gravid females or young juveniles are dying, the issue is most likely inadequate moisture.
Without adequate room to move and grow, giant Porcellio will die from the stress of competing over space. We recommend a minimum setup of a 15L plastic tote, but we prefer to house our cultures in 25L totes. Male Porcellio are often territorial and will chase off competing males and juveniles. The space should also allow for adequate airflow. These Spanish giants are native to high airflow areas, so it is important to not allow the air to grow stagnant. An inch of “dead space” should be provided between the top of the enclosure and the top of the leaf litter to encourage air movement. Mold is not a concern because these are still isopods and detritivores, but the actual flow of the air is important. Large vents are also highly recommended (as opposed to holes either drilled or made with a soldering iron). These vents should be placed on either side of the setup to encourage cross ventilation across the enclosure. If vents are only on one end of the setup, it does not encourage the air to flow through the setup and it becomes stagnant.
Sometimes the husbandry is corrected, but the animals are still dying. There are a few other things that may be causing this. If a large amount of the population died off prior to the correction and no new animals have been introduced, the issue may be a poor ratio between males and females. An ideal ratio is 1 female for every 1 male, but even better is more females than males. Males can be aggressive in their breeding behavior, and constantly being bred by males is stressful, especially if the female is already gravid. This may cause a very gravid female to die of stress. To correct this, the excess males should be removed to a separate “bachelor pad” from the females until the population reaches a more ideal ratio. The males don’t have to be added back either; they can be fed off to reptiles or culled, but returning them to the culture is good for genetic diversity.
The diet of giant Porcellio is a bit unique in comparison to other isopods because they predominantly eat hardwood leaf litter and rotten wood. Rotten wood, or flake soil, seems to make or break what giant Porcellio need to thrive. This may be due to the microorganisms and fungi that eat decaying wood or some other nutritional component. Keepers have had success offering a varied diet to the isopods with a variety of food sources and blends, but the easiest method is to just toss a baked log in there. Giant Porcellio do need a generous calcium source to support their large bodies, and gravid females and juveniles are very protein hungry (protein consumption drastically increases during their birthing season in early spring and fall).