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,
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). 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
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
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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