THE BIOLOGY OF WOOD-BORIXO TEREDINID MOLLUSCS
44 1
XVI. FOOD AND DIGESTION
All wood fragments scraped off during drilling pass through the
alimentary canal which has been greatly specialized with special
pouches like the caecum (appendix) for the reception of wood and the
specialized region of the digestive diverticula for the intracellular
digestion of cellulose. Potts (1923) observing the ingestion of wood
fragments by the " liver " cells of Teredo suggested the possible direct
utilization of wood in the nutrition of the animal. Various authors have
suggested that the excavated wood is used as food. Harrington (1921)
was perhaps the first to present experimental proof that the extracts
of the digestive diverticula of Teredo norvegica could break down
cellulose. Dore and Miller (1923) and later Miller (1925) demonstrated
that about 80% of cellulose and 1 5 4 6 % of hemi-celluloses disappear
from the wood during its passage through the digestive tract of T.
navalis. Lazier (1924) gave some evidence on digestion of wood particles by scrutinizing the staining reaction with haematoxylin of cellulose in different regions of the digestive tract. Hashimoto and Onoma
(1949) showed the presence of cellulase, alginase and xylanase activity
in the " liver " of Teredo while Mawatari (1950) identified amylase,
cellulase, cellobiase, saccharase and maltase in the midgut. Miller and
Boynton (1926) analysed samples of wood particles taken from the
caecum of Bankia setacea, and found the percentage of reducing sugars
to be as high as 3.86 while in the wood it was only 0.92. Boynton and
Miller (1927) analysed various parts of the digestive tract and demonstrated the presence of cellulase in the digestive diverticula and its
absence in the crystalline style. Miller and Norris (1940) later confirmed that extracts of the digestive diverticula contain cellulase and
further showed the presence of amylase, phosphatase, lipase, catalase,
peroxidase urease and a tryptic-type proteolytic enzyme. The style
contained only amylase according to these authors. Lane and Greenfield (1952) have reported the presence of a cellulase enzyme system
located in the general gut wall " in the anterior third of the gut " of
Teredo. Greenfield ( 1955) separated and concentrated this cellulase
from tissue homogenates by adsorbing it on cellulose gum and later
recovering the enzyme by ammonium sulphate precipitation. Greenfield andLane (1953) also demonstrated that cellulase activity in that part
of the alimentary canal which includes the caecum, the intestine and
the rectum is approximately double that in the region anterior to the
caecum. Nevertheless, Zobell (1946) pointed out that the question is
still open whether the cellulases and lignases present in the digestive
tract of Teredo are produced by the animal itself or by commensal
44 1
XVI. FOOD AND DIGESTION
All wood fragments scraped off during drilling pass through the
alimentary canal which has been greatly specialized with special
pouches like the caecum (appendix) for the reception of wood and the
specialized region of the digestive diverticula for the intracellular
digestion of cellulose. Potts (1923) observing the ingestion of wood
fragments by the " liver " cells of Teredo suggested the possible direct
utilization of wood in the nutrition of the animal. Various authors have
suggested that the excavated wood is used as food. Harrington (1921)
was perhaps the first to present experimental proof that the extracts
of the digestive diverticula of Teredo norvegica could break down
cellulose. Dore and Miller (1923) and later Miller (1925) demonstrated
that about 80% of cellulose and 1 5 4 6 % of hemi-celluloses disappear
from the wood during its passage through the digestive tract of T.
navalis. Lazier (1924) gave some evidence on digestion of wood particles by scrutinizing the staining reaction with haematoxylin of cellulose in different regions of the digestive tract. Hashimoto and Onoma
(1949) showed the presence of cellulase, alginase and xylanase activity
in the " liver " of Teredo while Mawatari (1950) identified amylase,
cellulase, cellobiase, saccharase and maltase in the midgut. Miller and
Boynton (1926) analysed samples of wood particles taken from the
caecum of Bankia setacea, and found the percentage of reducing sugars
to be as high as 3.86 while in the wood it was only 0.92. Boynton and
Miller (1927) analysed various parts of the digestive tract and demonstrated the presence of cellulase in the digestive diverticula and its
absence in the crystalline style. Miller and Norris (1940) later confirmed that extracts of the digestive diverticula contain cellulase and
further showed the presence of amylase, phosphatase, lipase, catalase,
peroxidase urease and a tryptic-type proteolytic enzyme. The style
contained only amylase according to these authors. Lane and Greenfield (1952) have reported the presence of a cellulase enzyme system
located in the general gut wall " in the anterior third of the gut " of
Teredo. Greenfield ( 1955) separated and concentrated this cellulase
from tissue homogenates by adsorbing it on cellulose gum and later
recovering the enzyme by ammonium sulphate precipitation. Greenfield andLane (1953) also demonstrated that cellulase activity in that part
of the alimentary canal which includes the caecum, the intestine and
the rectum is approximately double that in the region anterior to the
caecum. Nevertheless, Zobell (1946) pointed out that the question is
still open whether the cellulases and lignases present in the digestive
tract of Teredo are produced by the animal itself or by commensal