4. ANALYSIS O F FACTORS INVOLVED I N SYMBIOSIS
97
‘‘ epifauna ” or “ epizoites.” However, as Korringa (1951a) and others
have pointed out, the habitats of certain populations of marine molluscs, such as oyster beds, are particularly rich in invertebrates, many
of which are actually attached to the shells of oysters. Korringa has
expressed the opinion that ‘‘ shelter ” is a major factor which accounts
for the densities of the large number of species of organisms found
associated with oyster beds. Relative to the possibility that these
associated invertebrates also derive nutrients from the oysters, Korringa
has stated :
We wonder whether or not the oyster itself contributes to the food of its
epifauna. Though I investigated this possibility very carefully, I found no
evidence that any of the epibionts can be considered as true parasites feeding
on the living tissues of the oyster itself. The possibility remains, however,
that faeces and pseudo-faeces (dejecta and rejecta) produced by the oyster
may contribute to the fertility of the habitat.
However, after studying the ‘‘ epifauna ” of dummy oysters, Korringa
has concluded that both the feces and pseudo-feces are not of great
importance in the ecology of these associated animals.
Another possible source of nutrients which Korringa has failed to
consider is the “shell liquor” or mantle fluid of oysters which is
continuously being exuded to the exterior during active pumping. This
protein- and amino acid-rich fluid may well serve as a nutrient source.
Needless to say, a great deal remains to be studied relative to the
associations between oysters and associated organisms.
I n addition to Korringa’s (1951a) extensive study, the ‘‘ epifauna ”,
or preferably the epiphoronts, of oysters have been studied by Mdbius
(1893) in German oyster beds. These investigations had led Mdbius,
who also recognized the richness of such communities, to formulate
the concept of “ biocoenosis ”. In addition, Zernov (1913) has studied
the fauna of the natural oyster beds of the Black Sea, Verrill (1873) has
included a list of animals found on oyster beds in Vineyard Sound,
Massachusetts, and Miyazaki (1938) has studied the organisms fouling
the shell-strings hung from rafts in some Japanese oyster farms.
Similarly, Schodduyn (1927, 1931) and FerroniAres (1901) have studied
the fauna associated with oysters in France, Leloup (1940) has studied
the flora and fauna in oyster beds at Ostend, Belgium, and BytinskiSalz (1935) has included notes on the epiphoronts of oysters in Rovigno
d’Istria, Italy.
Although undoubtedly the majority of these animals are epiphoronts, some may be commensals while others may become facultative parasites. An example of the last category is in the form of the
flagellate Hexamita, probably H . in$ata. This protozoan is commonly
A.M.B.-6
8
97
‘‘ epifauna ” or “ epizoites.” However, as Korringa (1951a) and others
have pointed out, the habitats of certain populations of marine molluscs, such as oyster beds, are particularly rich in invertebrates, many
of which are actually attached to the shells of oysters. Korringa has
expressed the opinion that ‘‘ shelter ” is a major factor which accounts
for the densities of the large number of species of organisms found
associated with oyster beds. Relative to the possibility that these
associated invertebrates also derive nutrients from the oysters, Korringa
has stated :
We wonder whether or not the oyster itself contributes to the food of its
epifauna. Though I investigated this possibility very carefully, I found no
evidence that any of the epibionts can be considered as true parasites feeding
on the living tissues of the oyster itself. The possibility remains, however,
that faeces and pseudo-faeces (dejecta and rejecta) produced by the oyster
may contribute to the fertility of the habitat.
However, after studying the ‘‘ epifauna ” of dummy oysters, Korringa
has concluded that both the feces and pseudo-feces are not of great
importance in the ecology of these associated animals.
Another possible source of nutrients which Korringa has failed to
consider is the “shell liquor” or mantle fluid of oysters which is
continuously being exuded to the exterior during active pumping. This
protein- and amino acid-rich fluid may well serve as a nutrient source.
Needless to say, a great deal remains to be studied relative to the
associations between oysters and associated organisms.
I n addition to Korringa’s (1951a) extensive study, the ‘‘ epifauna ”,
or preferably the epiphoronts, of oysters have been studied by Mdbius
(1893) in German oyster beds. These investigations had led Mdbius,
who also recognized the richness of such communities, to formulate
the concept of “ biocoenosis ”. In addition, Zernov (1913) has studied
the fauna of the natural oyster beds of the Black Sea, Verrill (1873) has
included a list of animals found on oyster beds in Vineyard Sound,
Massachusetts, and Miyazaki (1938) has studied the organisms fouling
the shell-strings hung from rafts in some Japanese oyster farms.
Similarly, Schodduyn (1927, 1931) and FerroniAres (1901) have studied
the fauna associated with oysters in France, Leloup (1940) has studied
the flora and fauna in oyster beds at Ostend, Belgium, and BytinskiSalz (1935) has included notes on the epiphoronts of oysters in Rovigno
d’Istria, Italy.
Although undoubtedly the majority of these animals are epiphoronts, some may be commensals while others may become facultative parasites. An example of the last category is in the form of the
flagellate Hexamita, probably H . in$ata. This protozoan is commonly
A.M.B.-6
8