178
MARINE MOLLTJSCS AS HOSTS FOR SYMBIOSES
Some of these ciliates have been reported to be true parasites while
others are believed to be commensals ; however, in no instance has the
physiological relationship between the host and symbiont been studied
except that some have been reported to feed on their hosts’ cytoplasm.
Considered below are those thigmotrichous ciliates which are known
to be associated with the more economically important molluscs. For
a listing of the known species of the Thigmotrichida, the reader is
referred to the extensive studies of Issel (1903)) Jarocki and Raabe
(1932)) Chatton and Lwoff (1922a,b, 1923, 1924, 1926, 1939, 1949, 1950),
Kidder (1933a-d, 1934)) Uyemura (1937) and Corliss (1961).
1. Ancistrum mytili (Quennerstedt, 1867). (Figs. 77-79)
(Subclass Holotrichia; order Thigmotrichida; family Hemispeiridae)
Ancistrum mytili was originally described by Quennerstedt ( 1867)
from the mantle cavity of Mytilus in Sweden and named Opalina
mytili. Kent (1882) transferred it to the genus Anoplophrya. Maupas
(1883) in redescribing this ciliate called attention to the fact that a
cytostome is present. He established the genus Ancistrum with A.
mytili as the genotype. Strand (1928) erroneously believed that
Ancistrum was preoccupied and as the consequence proposed Ancistruma
as a replacement, but as Corliss (1961) has pointed out, this was not
necessary.
According to Kidder (1933c), A. mytili is found in abundance in
the mantle cavity of the mussel Mytilus edulis a t Woods Hole,
Massachusetts, and at Brighton Beach, Manhattan Beach, and Port
Washington, Long Island, New York. According to Issel (1903), it
occurs on the gills of Modiola ba,rbata in the Gulf of Naples. More
recently, Pauley et al. (1966), in an abstract, have reported the occurrence of ciliates which closely resemble A. mytili and a related species,
A . caudatum, free in the branchial chambers of the gills and attached
to the ciliated epithelium of the gills of Mytilus edulis in Humboldt
Bay, California.
Description. Body oval, 52-74 p (average 67 p ) x 20-38 p (average
31 p), dorsoventrally flattened ; dorsal surface convex, ventral surface
concave ; cilia on both surfaces ; dorsal edge of peristome curves around
cytostome which is located near posterior extremity ; peristomal floor
folded and protruding ; three rows of cilia on peristomal edges ; macronucleus elongate, kidney-shaped ; compact micronucleus anterior to
or a t same level as anterior portion of macronucleus; many food
vacuoles, filled with bacteria and small particles, in posterior portion
of body ; one contractile vacuole on left of body near posterior terminal.
MARINE MOLLTJSCS AS HOSTS FOR SYMBIOSES
Some of these ciliates have been reported to be true parasites while
others are believed to be commensals ; however, in no instance has the
physiological relationship between the host and symbiont been studied
except that some have been reported to feed on their hosts’ cytoplasm.
Considered below are those thigmotrichous ciliates which are known
to be associated with the more economically important molluscs. For
a listing of the known species of the Thigmotrichida, the reader is
referred to the extensive studies of Issel (1903)) Jarocki and Raabe
(1932)) Chatton and Lwoff (1922a,b, 1923, 1924, 1926, 1939, 1949, 1950),
Kidder (1933a-d, 1934)) Uyemura (1937) and Corliss (1961).
1. Ancistrum mytili (Quennerstedt, 1867). (Figs. 77-79)
(Subclass Holotrichia; order Thigmotrichida; family Hemispeiridae)
Ancistrum mytili was originally described by Quennerstedt ( 1867)
from the mantle cavity of Mytilus in Sweden and named Opalina
mytili. Kent (1882) transferred it to the genus Anoplophrya. Maupas
(1883) in redescribing this ciliate called attention to the fact that a
cytostome is present. He established the genus Ancistrum with A.
mytili as the genotype. Strand (1928) erroneously believed that
Ancistrum was preoccupied and as the consequence proposed Ancistruma
as a replacement, but as Corliss (1961) has pointed out, this was not
necessary.
According to Kidder (1933c), A. mytili is found in abundance in
the mantle cavity of the mussel Mytilus edulis a t Woods Hole,
Massachusetts, and at Brighton Beach, Manhattan Beach, and Port
Washington, Long Island, New York. According to Issel (1903), it
occurs on the gills of Modiola ba,rbata in the Gulf of Naples. More
recently, Pauley et al. (1966), in an abstract, have reported the occurrence of ciliates which closely resemble A. mytili and a related species,
A . caudatum, free in the branchial chambers of the gills and attached
to the ciliated epithelium of the gills of Mytilus edulis in Humboldt
Bay, California.
Description. Body oval, 52-74 p (average 67 p ) x 20-38 p (average
31 p), dorsoventrally flattened ; dorsal surface convex, ventral surface
concave ; cilia on both surfaces ; dorsal edge of peristome curves around
cytostome which is located near posterior extremity ; peristomal floor
folded and protruding ; three rows of cilia on peristomal edges ; macronucleus elongate, kidney-shaped ; compact micronucleus anterior to
or a t same level as anterior portion of macronucleus; many food
vacuoles, filled with bacteria and small particles, in posterior portion
of body ; one contractile vacuole on left of body near posterior terminal.