SCATOLOGICAL STVDIES O F THE BIVALVIA (MOLLVSCA)
379
IV. BIOLOGICAL SIGNIFICANCE OF THE CHARACTERISTIC
FORM OF FAECAL PELLETS
A. Relation of faecal characteristics to the feeding habit und mode of life
As described in the previous section, the nature and form of the
faecal pellets varies widely within the ciliary feeding bivalves. This
variation seems to be related more to feeding habit and mode of life
than to systematic position. Kornicker (1962) in discussing the effect of
feeding and habitat on the nature of pellets suggests “ t h e shape,
composition and consistency of faecal pellets might prove useful in
interpreting the feeding habit and habitat of the animal from which
they were excreted”. With relation to this, Moore (1939) also states,
‘‘ I n general, carnivorous animals tend to produce faeces of loose consistency, vegetable eaters firmer ones, and deposit eaters the most
resistant of all.” Although precise biological information on this matter
is still far from complete, the data collected from various sources suggest that the nature and form of pellets do have some relationship,
both direct and indirect, to the feeding habit and habitat or to the
mode of life of the producer.
The Bivalvia are almost all ciliary feeders, collecting small food
particles from suspensions or from sedimentary deposits by means of
ctenidia and labial palps. Considering the feeding mechanisms in the
lamellibranchs in more detail, the Filibranchia, Pseudolamellibranchia
and Eulamellibranchia possess ctenidia of increasing complexity for the
collection of fine food particles. Particulate matter is sieved from the
inhalant current and, after sorting by the palps, suitable quantities and
grades are passed into the mouth. Unsuitable or over-numerous particles are rejected from the mantle cavity in the form of mucus-laden
masses or pseudofaeces.
The pellets in the attached, i.e. epifaunal, suspeiision feeders with
filibranch ctenidia, belong to Type 111-10 or 10a, whereas those of
burrowing forms such as Oblimopa and Lirnopsis (Limopsidae) belong
to Type 11-4. Within the Pseudolamellibranchia, the pellets of the freeswimming forms such as Arnusiurn and Pecten belong to Type 11-8 and
the sessile forms such as Ostrea, Pinctada, Isognomon and Atrina to the
former Type (111-10 or 10a). Those of the intermediate forms such as
Chlamys belong to Type IIA-9 or 9a. It may be of interest to note in
this connection that there is a striking parallelism in pellet shape (Type
111-10) between byssally attached eulamellibranchs such as Cardita
(Carditacea) and sessile filibranchs and pseudolamellibranchs. The
highest complexity of ctenidial organization is achieved in Eulamelliof the animal
379
IV. BIOLOGICAL SIGNIFICANCE OF THE CHARACTERISTIC
FORM OF FAECAL PELLETS
A. Relation of faecal characteristics to the feeding habit und mode of life
As described in the previous section, the nature and form of the
faecal pellets varies widely within the ciliary feeding bivalves. This
variation seems to be related more to feeding habit and mode of life
than to systematic position. Kornicker (1962) in discussing the effect of
feeding and habitat on the nature of pellets suggests “ t h e shape,
composition and consistency of faecal pellets might prove useful in
interpreting the feeding habit and habitat of the animal from which
they were excreted”. With relation to this, Moore (1939) also states,
‘‘ I n general, carnivorous animals tend to produce faeces of loose consistency, vegetable eaters firmer ones, and deposit eaters the most
resistant of all.” Although precise biological information on this matter
is still far from complete, the data collected from various sources suggest that the nature and form of pellets do have some relationship,
both direct and indirect, to the feeding habit and habitat or to the
mode of life of the producer.
The Bivalvia are almost all ciliary feeders, collecting small food
particles from suspensions or from sedimentary deposits by means of
ctenidia and labial palps. Considering the feeding mechanisms in the
lamellibranchs in more detail, the Filibranchia, Pseudolamellibranchia
and Eulamellibranchia possess ctenidia of increasing complexity for the
collection of fine food particles. Particulate matter is sieved from the
inhalant current and, after sorting by the palps, suitable quantities and
grades are passed into the mouth. Unsuitable or over-numerous particles are rejected from the mantle cavity in the form of mucus-laden
masses or pseudofaeces.
The pellets in the attached, i.e. epifaunal, suspeiision feeders with
filibranch ctenidia, belong to Type 111-10 or 10a, whereas those of
burrowing forms such as Oblimopa and Lirnopsis (Limopsidae) belong
to Type 11-4. Within the Pseudolamellibranchia, the pellets of the freeswimming forms such as Arnusiurn and Pecten belong to Type 11-8 and
the sessile forms such as Ostrea, Pinctada, Isognomon and Atrina to the
former Type (111-10 or 10a). Those of the intermediate forms such as
Chlamys belong to Type IIA-9 or 9a. It may be of interest to note in
this connection that there is a striking parallelism in pellet shape (Type
111-10) between byssally attached eulamellibranchs such as Cardita
(Carditacea) and sessile filibranchs and pseudolamellibranchs. The
highest complexity of ctenidial organization is achieved in Eulamelliof the animal