Interactions: the host and the help

Armadillidium vulgare are omnivorous organisms that have been found to eat a wide variety of matter. They are known to eat dead plant matter, but also will occasionally eat leaves of plants that are clinging to life.  Additionally, the organism consumes carcasses of dead invertebrates, larger organisms in various states of decomposition, and on rare occasions, they even consume individuals of their own species (Paris 1963). Most importantly,Armadillidium vulgare consuming one of their own. Photo by Carlos M. Mancilla C. courtesy of Flickr. Used with permission. however, is that A.vulgare serves as a decomposer that aids in cycling of nutrients (add link to nutrient cycle) within an ecosystem. Decomposers are driving forces in the nutrient cycle because they break down more complicated organisms to basic organic matter to be recycled back into the ecosystem (Lavelle et al. 2013). 

    A.vulgure can also play a different role in the cycling of nutrients in an ecosystem as prey.  It is a common misconception that A.vulgure has extensive amounts of predators, such as spiders, centipedes, lizards, salamanders, and birds.  However, due to tegumental glands that secrete nasty tasting chemicals throughout the body, spiders find A. vulgure distasteful and avoid eating them altogether (Paris 1963).  Centipedes simply appear to have no preference for isopods in general, most likely due to their armor-like covering.  In opposition, certain Carabid beetles, salamanders and lizards commonly prey on A.vulgare and other isopods (Paris 1963).  Due to its relatively low number of predators, A.vulgare thrives in every ecosystem it resides in and the species is nowhere near threatened.

    In addition to the predator/prey relationship formed between A. vulgare and other species, the organism has commonly been found to be a host to parasites known as Plagiorhynchus cylindraceus (Nickol and Dappen 1982).Male American robin with a worm.  Photo by Ryan Rushby courtesy of WikiMedia Commons. [ Creative Commons Attribution 2.5 Generic]  P.cylindraceus also has a parasitic relationship with a variety of different birds, including the robin. The robin or other birds, they make their way into the digestive tract where they mate in the intestine and the resulting eggs leave the bird in its feces. A.vulgare becomes infected when it consumes the birds’ feces with the eggs inside, taking them into itself.  Within two hours, the eggs hatch into larvae and bore into the blood cavity where they remain as they enlarge for the following 60-65 days.  Finally, A. vulgare is consumed by a robin or passing bird and P. cylindraceus begins the cycle over again in that bird’s intestine (Roberts and Janovy Jr 2000; Poulin and Moreand 2000). 

    Another parasitic relationship commonly found in A.vulgare is the infection of Wolbachia endosymbionts.  Approximately 62% of all terrestrial isopod species are infected by the Wolbachia bacterium (Bouchon et al. 2008).  Wolbachia infect the haemocytes, blood cells specific to invertebrates, of A.vulgare, resulting in immunodepression (Chevalier 2011). The infection process begins in hematopoietic organs, which are responsible for the creation of  Transmission electron micrograph of Wolbachia within an insect cell. Photo by Scott O'Neill [Genome Sequence of the Intracellular Bacterium Wolbachia. PLoS Biol 2/3/2004: e76. doi:10.1371/journal.pbio.0020076]haemocytes within the isopod, where Wolbachia accumulate and reproduce rapidly.  More or less, the hematopoietic organs are a Wolbachia factory that effectively packs the bacterium into vacuoles to be sent through the haemolymph throughout the host A.vulgare’s body.  These bacteria colonize, on average, one third of the haemocytes within an individual, which causes reduced prophenoloxidase activity in the haemolymph (Chevalier et al. 2011).  Prophenoloxidase is an enzyme responsible for activating phenoloxidase, another enzyme that is primarily responsible for immune responses in terrestrial isopods (King et al. 2010).  When these enzymes are suppressed by Wolbachia, A.vulgare has suppressed immune responses and therefore, immunodeficiency.  This parasitic relationship is a very common negative symbiotic relationship found in A.vulgare.

    On a positive front, Armadillidium vulgare provide multiple useful services to humans.  They allow for the recycling of precious organic compounds throughout our ecosystem by playing the role of decomposer in nutrient cycling (Lavelle et al. 2013).  Decomposers like this organism digest fecal matter from larger organisms and decaying matter and return the nutrients to the soil for re-use.  This is a great service to humans for anything from small gardens to large farms (although many rely heavily on the use of heavy fertilizers) for thriving crop growth.

    The reproduction of A.vulgare among other soil-dwelling isopods and arthropods such as the horsefly, Deathwatch beetle, and Northeastern Pine Sawyer beetle provide a very important service to humans as well.  Forensic entomology is the study of insects, arthropods, or isopods in criminal investigation (Joseph et al. 2012). This is one way that murder crimes are solved.  By evaluating the larval stages of the insects (or isopods, arthropods, etc) and the insect waves inside the rotting corpse, a forensic scientist can determine the time elapsed since that person died.  However, this process can’t always be used to identify approximate time of death; usually, forensic entomology is most useful and Fly and beetle larvae in a decomposing porcupine.  Taken by Paul Ventor, courtesy of WikiMedia Commons [ Creative Commons Attribution-Share Alike 3.0 Unported license]possibly the only means of determining time of death at least 72 hours after the individual died (Anderson 2013).  One method of identifying time of death, by observing waves of insects, is based off knowledge that certain insects will be attracted to the body at different stages of decomposition and will therefore show up in different patterns.  The second method of identification is through analysis of larvae stages of different insects that have reproduced in the decaying body.  Forensic entomologists know the approximate time for the larval periods of various insects and also approximately which conditions the adults would have reproduced in.  Therefore, using either or both of these analytical methods, the approximate time of death can be determined (Anderson 2013).  A.vulgare is among many terrestrial isopods that find a decaying body appealing, and can potentially be a helpful factor in identifying John or Jane Does in police investigations, bringing peace to families and (if the case calls for it) justice to criminals.

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