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All you need to know about mold

Discussion in 'Tarantula Questions & Discussions' started by boina, Nov 9, 2018.

  1. boina

    boina Lady of the mites Arachnosupporter

    Well, I made a similar post about mites and it seemed quite popular, and since questions about mold pop up again and again I thought maybe I can shed some light on this topic, too.

    The thing is: with mites it was easy. They are harmless, period. With mold it’s not that easy, because there are definitely some not so harmless varieties out there… but before anyone panics: they are rare, very rare and not easy to come by.

    First, let’s sort out the terminology:

    1. Fungi: These pose a separate kingdom, besides animals and plants. Mushrooms, mold, yeast, microsporidia etc, etc, are all fungi.

    2. Mold: this is a subtype of fungus made up of filamentous hyphens. It is not a biological classification but simply describes a morphological form.

    3. Yeast: another subtype of fungus, appearing as single cells.

    4. Dimorphic fungi: those are interesting because they can be either mold or yeast, depending on external factors, like temperature. A lot of human pathogens belong here.

    5. Mushrooms: Those are the fruiting bodies of some fungi, not a group of fungi by themselves.

    6. Microsporidia: These are obligate parasites. They cannot survive by themselves but always live inside other cells, usually animal's.

    The overwhelming majority of fungi, mold and yeast alike, are saprophytic, meaning they live off decaying organic matter. If it shows up as a fuzzy carpet in your enclosure or even as a mushroom it’s saprophytic and therefore harmless. Just ignore it. As a general rule: if it can live on decaying organic matter it’s a saprophyte and nearly always completely harmless for the tarantula, or any other invert for that matter. Tarantulas do not get infections from saprophytic fungus, not in their book lungs or elsewhere, at least not as long as they are healthy. First of all, saprophytes as a rule cannot get into living cells and second, healthy tarantulas have an immune system, consisting of specialized cells called hemocytes, and antimicrobial peptides, that are extremely efficient against mold. How else would they survive in a natural environment full of mold spores, especially those tropical species?

    There are, however, a couple of opportunistic parasites among the saprophytes. If a tarantula is weakened by bad environmental parameters (too moist, not enough ventilation, bacterial infection, etc, etc…) these opportunistic parasites may attack. G. Lewbart mentions opportunistic infections on the cuticles in his book about invertebrate medicine. Again: you need to weaken your tarantula by keeping her very poorly for this opportunistic pathogens to get a chance.

    Then there are the true entomopathogenic fungi. Quite a few of those don’t differentiate between insects and arachnids, but are quite happy to use arachnids as a host, too. The notorious and spectacular Cordyceps fungus and its relatives belong here, but there are quite a few more. The thing with any of these obligate parasites is: they need to come from somewhere. They don’t just ride in on wind currents from the Amazon. The spores don’t go that far, and even if they do: a single spore has no chance in a healthy tarantula. Remember the immune system? There needs to be a certain load of spores for them to succeed. Entomoparasitc fungus comes in on infected WC tarantulas, or, very rarely, in infected crickets (not Cordyceps, but other parasites). Since the crickets will die in masses from the fungal infections a cricket breeder who gets his breeding stock infected will be out of said breeding stock very soon, so the chances that infected crickets will make it to you are slim. And even if the tarantula eats an infected cricket – the fungus on the inside of the cricked will just get digested, like anything else inside that cricket.

    The symptoms of a systemic infection with parasitic fungus in a tarantula are hard to see. It will most certainly NOT get fuzzy growth on the outside of its body – real entomoparasites grow on the inside. When they break through the exoskeleton to release the spores from the fruiting bodies the tarantula is already dead. All you will see is the tarantula getting weaker and weaker – and remember, we are talking about WC tarantulas here.

    The last group to be concerned with are the Microsporidia, the obligatory intracellular parasites. Their ability to infect arachnids is not well documented, but I know of at least one case of a proven infection in a group of tarantulas. The tarantulas in question actually showed DKS like symptoms and the keeper in question lost a large part of his collection. A pathological analysis of the dead spiders demonstrated Microsporidia in the gut cells. Again, this is a fungus that doesn’t look like a fungus at all and presents with unexpected symptoms.


    1. Fuzzy mold in your enclosure is saprophytic and harmless. Ignore it, but make sure your tarantula is in good shape and your keeping parameters are spot on.

    2. True entomoparasites kill quickly and without much notice – and without any fuzzy growth on the outside - but they need to come from somewhere. You can only reasonably expect them in WC spiders.

    3. Microsporidia are the silent, invisible killers. If your tarantula shows signs of DKS, consider these.

    Further reading:



    • Informative x 20
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  2. Teal

    Teal Arachnoemperor Old Timer

    Can this be made a sticky? Love it!
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  3. Killertut

    Killertut Arachnosquire

    bravo :D
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  4. FrDoc

    FrDoc Arachnolord Active Member

    @boina - she knows things and stuff.
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  5. Thank you!
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  6. Chris LXXIX

    Chris LXXIX ArachnoGod Active Member

    Lady of Mites and Mold: sounds amazing and so unique :kiss:
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  7. antinous

    antinous Pamphopharaoh

    Open your eyes guys, she’s just doing it for the likes

    Kidding, but thanks for the useful information! This is be a great help as many new hobbyists will be asking about mites and molds and it’ll be easy to just share this link with them!
  8. AngelDeVille

    AngelDeVille Fuk Da Meme Police

    The fuzzy stuff helps me find the emboli....
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  9. boina

    boina Lady of the mites Arachnosupporter

    You're not getting any more likes from me... :shifty::punch:

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  10. antinous

    antinous Pamphopharaoh

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