Growth of Fungus

A discussion of mold and fungi and hermit crabs

A discussion of mold and fungi and hermit crabs

written by Jennifer Borgesen

The fungi:  how they grow and their effects on human health. (includes related article on documentation of fungal exposure and disease relationship) Date: 07-01-1997; Publication: Heating, Piping, Air Conditioning; Author: Burge, Harriet A.

Shape and structure of fungi

“The fungal cell is similar to that. of plants and animals, containing all of the same organelles (nucleus, mitochondria, ribosomes, membrane systems, etc.). Like plants, the fungal cell is bounded by a rigid cell wall. However, while plant cell walls contain cellulose as the basic structural material, fungal cell walls contain a material that is similar to that in insect exoskeletons (chitin). Most fungal walls also contain substances called glucans that can be toxic to animal cells.”(Burge, Harriet A.. 1997))

Very interesting that fungal cell walls are made up of the same material as our pet’s exoskeleton – chitin – while also containing a material – glucans- that can be toxic to animals.

“Temperature also plays a direct role in the colonization of surfaces with fungi. At relatively low temperatures (50 to 60 F), spores take longer to germinate and growth is slower to become established than at, say, 60 to 70 F. Water activity optima are usually higher at low temperatures than at high. This means that high water activity levels must be maintained for longer periods in cold than in warm environments for growth to occur.”(ibid)

Ok … as anyone who lives in a humid climate knows … as heat and dampness rises, so does the amount of mold you must scrub out of your bathroom! Obviously … a crabitiat is a substrate made in Fungi- heaven, both warm and damp. So is there anything in the latter part that may help us make our hermies home less compatible with fungal growth?

“Carbon, nitrogen, and a variety of mineral elements are also essential for fungal growth. There are fungi that can use most complex carbon-containing compounds, but most favor sugars, with some able to utilize cellulose and lignin. Fungi are unique in their ability to degrade the latter two highly resistant polymers.”(ibid)

Wondering if this is why Don only placed Treat in his tank every few days and only for 24 hours? Alabama is right up there in the fungus rich states!

“Nitrate or ammonia can provide nitrogen to fungi as can amino acids and proteins. A common nitrogen source for dust-borne fungi is keratin, the structural protein from human skin. Again, fungi are among very few organisms that can degrade this highly resistant polymer. The mineral element needs of fungi are met by trace amounts of these necessary nutrients that occur as part of the carbohydrates and proteins used as carbon and nitrogen sources and dissolved in water.”(ibid)

Well .. this is a case for a glass or plexi lid over a screened or aquarium hood. The more airbourne elements, both fungal spores and keratin (from your skin and hair) that you can keep out of the crab tank, the less the chance of fungal infestation, or its growth. Right?

“In the process of degrading complex carbohydrates and proteins to release essential nutrients, fungi produce carbon dioxide, water, and a variety of other compounds that range from volatile aldehydes, alcohols, and ketones to complex secondary metabolites, including antibiotics and mycotoxins. The volatile compounds are responsible for the odors commonly associated with fungal growth, and although their health impact has not been studied, these odiferous compounds are [TABULAR DATA FOR TABLE 1 OMITTED] blamed for a variety of building- related complaints.”(ibid)

And we know what off gassing of the above aldehydes, ketones, and others can do to a crab’s gill system.

“Although most fungi probably produce these secondary metabolites, the conditions under which they do so are not clear, and it is likely that production is highly substrate-dependent.”(ibid)

And for this reason .. it is a good idea for us to continue to watch for more research on fungal growth and development. If they can begin to identify substrate conditions that encourage growth, it may lead us as crabbers to different choices of tank substrates and equipment.

“Fungi in the environment Fungi are responsible for most aerobic (oxidative) decay processes in the environment and play an essential role in the natural ecosystem. For example, fungi turn fallen leaves and dead trees into soil by digesting the complex carbohydrates (cellulose, lignin) into soluble forms. Composting utilizes this natural ability of fungi to process dead organic material. In colonizing building materials, which contain dead organic material, fungi are merely fulfilling their mission within the natural ecosystem.”(ibid)

Hence the reason organic material substrates are often discouraged for use within a crabitat.

“Fungal-related diseases Allergies (hay fever, asthma, allergic pneumonia) are caused by exposure to agents that stimulate a disease-causing immune response.”(ibid)

Hey! They’re talking about me!

“The development of an allergy is a two-step process. The first step is exposure to an allergen that causes sensitization but no symptoms. Allergens are usually proteins that are often derived from living organisms (Table 1). Sensitization means that the immune system has been stimulated to produce antibodies or activated cells that specifically recognize the allergen. The second step is symptom development, which requires exposure to an allergen after sensitization has occurred. Such exposure leads to the release of chemicals such as histamine that are powerful irritants, causing redness, swelling, and, i.n some cases, permanent changes in lung tissue.”(ibid)

Wow …. this is off topic but it is a great and highly factual description of how an allergy develops and how the immune system is effected! The rest of the description is really good too. Conclusion Fungi are unique organisms, many of which can utilize building materials as food sources, provided adequate water is present.

Ok … the conclusion is no surprise here, what was interesting and new to me is that the process by which the fungi convert elements into nutrients results in the off gassing of toxins that we know are trouble for our pets. I’d more or less figured it was by direct tissue infection that crabs were affected. according to this article, the presence of mold could also be a source gill stress. So mold at any time, anywhere within a crabitat can quickly become a health hazard.


Worth mentioning: While hermit crabs do eat rotten, decaying and moldy stuffs in the wild, they are in a confined air space when living in captivity with limited air exchange.