102
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
Kofoid and Bush (1936), but is associated with all six of the species of
molluscs examined. Furthermore he has pointed out that it is identical
with A . pelseneeri.
Mackin (1 962) has reported the occurrence of Ancistrocoma pelseneeri
in Crassostrea virginica " distributed over the Atlantic and Gulf coasts
of the United States ". According to him, the ciliate reported by
Richardson (1938)) in an unpublished in-house report of the Fisheries
Research Board of Canada, from oysters from Charlottetown, Prince
Edward Island, Canada, and placed in the genus Orchitophrya, is most
probably A . pelseneeri. Relative to parasitization by this ciliate,
Mackin has stated:
This parasite is usually rather rare in healthy oysters, but in diseased
oysters it is often found in large numbers in the stomach or intestine, and
may penetrate the ducts and tubules of the digestive gland. It may become
a complicating factor in Dermocystidium marinum infections but there is
no reason to think that it has much independent effect on the host.
Description. Body 50-83 p (average 62 p ) long x 14-20 p (average
16 p ) wide x 11-16 p (average 12.5 p ) thick, elongate, somewhat
flattened dorsoventrally, anterior terminal more or less attenuated,
banana-shaped, with incurved ventral surface when observed in
lateral view ; fourteen ciliary rows distributed on ventral, lateral and
dorsolateral body surfaces ; usually with five approximately equal
rows of cilia about two-thirds of body length on ventral surface,
bounded on right by three progressively longer and more widely
spaced rows and on left by six similar rows of cilia ; cilia forming outer
row on each side extend to near posterior body terminal ; retractable
suctorial tentacle at anterior end, with canal leading into cytoplasm ;
macronucleua, 11-16 p x 4-7 p, usually sausage-shaped, rarely ovoid,
typically situated dorsally near middle of body ; micronucleus, 1.22.1 p x 3.03-3.2 p, ovoid, fusiform, or sausage-shaped, usually on
right of macronucleus ; cytoplasm with numerous refractile lipoid
granules ; typical food vacuoles in posterior part of body.
Ecology. According to Kofoid and Bush (1936), A . pelsenewi
appears to be a commensal, feeding on bacteria and cellular debris
associated with its host's body surface. On the other hand, Kozloff
(1946~) has stated : " I believe that they are primarily branchial parasites which feed by means of the suctorial tentacle." At a later point
in his paper Kozloff further stated : " In the posterior part of the body
there are in addition t o typical food vacuoles containing ingested
fragments of epithelial cells one or more large vacuoles containing
globular masses usually of a dense, homogeneous character. ') Thus it
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
Kofoid and Bush (1936), but is associated with all six of the species of
molluscs examined. Furthermore he has pointed out that it is identical
with A . pelseneeri.
Mackin (1 962) has reported the occurrence of Ancistrocoma pelseneeri
in Crassostrea virginica " distributed over the Atlantic and Gulf coasts
of the United States ". According to him, the ciliate reported by
Richardson (1938)) in an unpublished in-house report of the Fisheries
Research Board of Canada, from oysters from Charlottetown, Prince
Edward Island, Canada, and placed in the genus Orchitophrya, is most
probably A . pelseneeri. Relative to parasitization by this ciliate,
Mackin has stated:
This parasite is usually rather rare in healthy oysters, but in diseased
oysters it is often found in large numbers in the stomach or intestine, and
may penetrate the ducts and tubules of the digestive gland. It may become
a complicating factor in Dermocystidium marinum infections but there is
no reason to think that it has much independent effect on the host.
Description. Body 50-83 p (average 62 p ) long x 14-20 p (average
16 p ) wide x 11-16 p (average 12.5 p ) thick, elongate, somewhat
flattened dorsoventrally, anterior terminal more or less attenuated,
banana-shaped, with incurved ventral surface when observed in
lateral view ; fourteen ciliary rows distributed on ventral, lateral and
dorsolateral body surfaces ; usually with five approximately equal
rows of cilia about two-thirds of body length on ventral surface,
bounded on right by three progressively longer and more widely
spaced rows and on left by six similar rows of cilia ; cilia forming outer
row on each side extend to near posterior body terminal ; retractable
suctorial tentacle at anterior end, with canal leading into cytoplasm ;
macronucleua, 11-16 p x 4-7 p, usually sausage-shaped, rarely ovoid,
typically situated dorsally near middle of body ; micronucleus, 1.22.1 p x 3.03-3.2 p, ovoid, fusiform, or sausage-shaped, usually on
right of macronucleus ; cytoplasm with numerous refractile lipoid
granules ; typical food vacuoles in posterior part of body.
Ecology. According to Kofoid and Bush (1936), A . pelsenewi
appears to be a commensal, feeding on bacteria and cellular debris
associated with its host's body surface. On the other hand, Kozloff
(1946~) has stated : " I believe that they are primarily branchial parasites which feed by means of the suctorial tentacle." At a later point
in his paper Kozloff further stated : " In the posterior part of the body
there are in addition t o typical food vacuoles containing ingested
fragments of epithelial cells one or more large vacuoles containing
globular masses usually of a dense, homogeneous character. ') Thus it