CHAPTER 6
PARASITES OF COMMERCIALLY IMPORTANT
MARINE MOLLUSCS
THE PHYLA PORIFERA, CNlDARlA AND PLATYHELMINTHES
I. Phylum PORIFERA
Boring sponges of the genus Cliona were first mentioned in the
scientific literature by Giard (1881) who indicated that they were well
known to French oystermen as the causative agent of “ spice bread
disease ”. This disease has been claimed to cause the mass destruction
of beds of oysters. Since Giard’s original report, over 100 scientific
papers dealing with boring sponges have been published. Among the
more recent, the most useful is that of Old (1941) who has contributed
a taxonomic study of those species found along the Atlantic coast of
North America, and those of Hopkins (1956a,b, 1962) who has demonstrated that the distribution of the species, a t least the common ones,
i.e. C. elata, C. vasti$ca, C. lobata and C. truitti, are governed by the
ambient salinity.
None of the boring sponges are believed to be true parasites. Galtsoff
(1964), in his summary of the biology of boring sponges, has stated :
“ It is not known whether boring sponges use the organic component
(conchiolin) of the shell, but it is obvious that they do not draw their
nutrients from the body of the oyster.” I n most instances boring
sponges inhabit tunnels in the molluscs’ shells. These tunnels are bored
by the sponges by what is believed to be mechanical action, although
the secretion of acids to aid in the fragmentation of the shell may occur
(Galtsoff, 1964). These tunnels do not as a rule perforate the shell,
hence the sponges do not make contact with the oyster’s soft tissues.
It is only in instances of old and heavy infestations that the tunnels
perforate the entire thickness of the shell. Even then, the holes are
rapidly mended by a deposition of conchiolin. If this mending process
is delayed by adverse conditions, the sponges will make direct contact
with the mantle and produce lysis of the epithelium and underlying
connective tissue. Grossly, areas on the mantle in contact with sponges
appear as dark pigmented pustules.
198
PARASITES OF COMMERCIALLY IMPORTANT
MARINE MOLLUSCS
THE PHYLA PORIFERA, CNlDARlA AND PLATYHELMINTHES
I. Phylum PORIFERA
Boring sponges of the genus Cliona were first mentioned in the
scientific literature by Giard (1881) who indicated that they were well
known to French oystermen as the causative agent of “ spice bread
disease ”. This disease has been claimed to cause the mass destruction
of beds of oysters. Since Giard’s original report, over 100 scientific
papers dealing with boring sponges have been published. Among the
more recent, the most useful is that of Old (1941) who has contributed
a taxonomic study of those species found along the Atlantic coast of
North America, and those of Hopkins (1956a,b, 1962) who has demonstrated that the distribution of the species, a t least the common ones,
i.e. C. elata, C. vasti$ca, C. lobata and C. truitti, are governed by the
ambient salinity.
None of the boring sponges are believed to be true parasites. Galtsoff
(1964), in his summary of the biology of boring sponges, has stated :
“ It is not known whether boring sponges use the organic component
(conchiolin) of the shell, but it is obvious that they do not draw their
nutrients from the body of the oyster.” I n most instances boring
sponges inhabit tunnels in the molluscs’ shells. These tunnels are bored
by the sponges by what is believed to be mechanical action, although
the secretion of acids to aid in the fragmentation of the shell may occur
(Galtsoff, 1964). These tunnels do not as a rule perforate the shell,
hence the sponges do not make contact with the oyster’s soft tissues.
It is only in instances of old and heavy infestations that the tunnels
perforate the entire thickness of the shell. Even then, the holes are
rapidly mended by a deposition of conchiolin. If this mending process
is delayed by adverse conditions, the sponges will make direct contact
with the mantle and produce lysis of the epithelium and underlying
connective tissue. Grossly, areas on the mantle in contact with sponges
appear as dark pigmented pustules.
198