spectrum was represented by parasites which can spend segments of their lives
independently. He mentioned that part time obligation as applying to some of the
entomopathogenic fungi which cause the disease muscardine. The fungal genera
which cause muscardine are Aspergillus, Beauveria, Cordyceps, Hirsutella,
Metarhizium, Penicillium, and Sorosporella. de Bary indicated that parasitic relationships were antagonistic and represented a struggle between host and parasite,
with a diversity of possible outcomes depending upon the individual case. One of the
examples that he included was the disease trichinosis, which is caused by the
metazoan genus Trichinella, whose symptomatology for its host can vary from
very limited to lethality.
14.5.2 Cooperative Relationships, Mutualism
and Commensalism
de Bary defined these as following the appearance of parasitism, but being quite
different.
The examples of cooperative relationships which de Bary gave included when,
based upon my translation “Many smaller animals are settled on larger ones and live
from the waste of the latter: from the desquamated epidermis parts, feathers, hair,
and the like.” de Bary referred to these situations, again based upon my translation,
as “van Beneden’s mutualists; they stand in relation to mutual support for the hosts
who [they] inhabit; by taking their food from the garbage they” take care of the toilet
“of the same.” We now consider these relationships to represent mutualism.
de Bary also mentioned, again by my translation, that “Other small animals settle
on or close to larger ones in order to live their lives from the crumbs that fall from the
large table: from the excess of the food material that the large one brings in for its
own use.” We have come to consider such an interaction as being classically
commensal, with that word derived from medieval Latin and defined as sharing a
table together (the prefix com-, meaning “together,” and the adjective mensalis,
meaning “of a table.”), characterized by a symbiotic relationship in which one
species is benefited while the other is unaffected.
My interpretation of de Bary’s intention becomes difficult at this point because,
by my translation, he mentions “These are van Beneden’s commensuals, blackheads.” I presume de Bary intended that to be a mention of the parasitologist PierreJoseph van Beneden, and reference to the disease which we know as histomoniasis
that is caused by the pleomorphic protozoan Histomonas meleagridis. Histomonas
meleagridis lives in the cecal lumen and liver parenchyma of birds, where it causes
extensive necrosis and one of the symptoms is cyanosis or darkening of the animals
head. That darkening of the birds head has resulted in histomoniasis being given the
name ‘blackhead disease’. Histomonas meleagridis naturally resides in eggs of the
nematode Heterakis gallinarum, which is itself a cecal parasite of birds, and thus
birds acquire Histomonas meleagridis during inadvertent ingestion of Heterakis
14 Discovering the Symbiotic Nature of Microbial Life: Summarizing Milestone. . .
217
independently. He mentioned that part time obligation as applying to some of the
entomopathogenic fungi which cause the disease muscardine. The fungal genera
which cause muscardine are Aspergillus, Beauveria, Cordyceps, Hirsutella,
Metarhizium, Penicillium, and Sorosporella. de Bary indicated that parasitic relationships were antagonistic and represented a struggle between host and parasite,
with a diversity of possible outcomes depending upon the individual case. One of the
examples that he included was the disease trichinosis, which is caused by the
metazoan genus Trichinella, whose symptomatology for its host can vary from
very limited to lethality.
14.5.2 Cooperative Relationships, Mutualism
and Commensalism
de Bary defined these as following the appearance of parasitism, but being quite
different.
The examples of cooperative relationships which de Bary gave included when,
based upon my translation “Many smaller animals are settled on larger ones and live
from the waste of the latter: from the desquamated epidermis parts, feathers, hair,
and the like.” de Bary referred to these situations, again based upon my translation,
as “van Beneden’s mutualists; they stand in relation to mutual support for the hosts
who [they] inhabit; by taking their food from the garbage they” take care of the toilet
“of the same.” We now consider these relationships to represent mutualism.
de Bary also mentioned, again by my translation, that “Other small animals settle
on or close to larger ones in order to live their lives from the crumbs that fall from the
large table: from the excess of the food material that the large one brings in for its
own use.” We have come to consider such an interaction as being classically
commensal, with that word derived from medieval Latin and defined as sharing a
table together (the prefix com-, meaning “together,” and the adjective mensalis,
meaning “of a table.”), characterized by a symbiotic relationship in which one
species is benefited while the other is unaffected.
My interpretation of de Bary’s intention becomes difficult at this point because,
by my translation, he mentions “These are van Beneden’s commensuals, blackheads.” I presume de Bary intended that to be a mention of the parasitologist PierreJoseph van Beneden, and reference to the disease which we know as histomoniasis
that is caused by the pleomorphic protozoan Histomonas meleagridis. Histomonas
meleagridis lives in the cecal lumen and liver parenchyma of birds, where it causes
extensive necrosis and one of the symptoms is cyanosis or darkening of the animals
head. That darkening of the birds head has resulted in histomoniasis being given the
name ‘blackhead disease’. Histomonas meleagridis naturally resides in eggs of the
nematode Heterakis gallinarum, which is itself a cecal parasite of birds, and thus
birds acquire Histomonas meleagridis during inadvertent ingestion of Heterakis
14 Discovering the Symbiotic Nature of Microbial Life: Summarizing Milestone. . .
217