THE I’L1YSIOI,OGY OF ASCIDIANS
81
Rimilar to the vanadium compound of t,he Ascidiidae and probably
serves t i Similar function.
1). Agylutination
According to Hecht ( 1 91 8c), IWton ( 1920) and Vallee (1967a,
1987b, 1968) the blood of ascidians docs not clot but in drawn blood
tfie cdls aggregate anti if left standing for some time separate again.
Vullee (tfK8) hiw shown that! the vcmrdocytm have free SH groups
which bind to OIK! another in ugglotinirt~ioil hut! can alternatively bind
to a free 8H group in cysttine whicbh Imv(?nts agglutination. Anderson
( 1 97 1) also found that vanadocytes aggregated around foreign bodies
impltmtcd in the tissues and were capable of secreting a protective
layer of test material over such bodies. In addition Fuke and Sugai
(1972) report that the body fluid of two species of ascidian (8tyela
p2icatn and Halocynthia h(i2gendorf i (Oka) ) contains haemagglutinins
which cause aggregation of mammalian erythrocytes but does not
aggregate blood cells of other ascidian species. Unlike other haemagglutinins the substance in ascidian fluids is a polysaccharide and not a
protein.
E. Blood function
It is possihle now to consider the role anti function of various types
of cell in asoidian blood. ‘I’ht. Z?pphocylc wems to be a transient multipotent cell type which can give rise to a11 other blood cells as required.
Vacuolar amoehocytca, signet-ring oc4s und compartment c:olls arc dcvclopmental phases in the formation of morula c-c4ls which are ooncc*rrit:d with
test formation. Morula cells contaiii organic. compounds of h w v y
metals notably vanadium or iron, but there is no evidence to suggwt
that these play a role in oxygen transport (Webb, 1939). The metabolic
level of ascidians is low anti Goodbody and Youriq (unpublished data)
have shown that oxygen consumption in Ascidia nigra ranges from
806 to 1630 pl/h/g ; t t specific oxygen carrier in the blood seems unnecessary. The precise role of the morula cell in test formation is still
unclear, but is most likely concerned with the deposition of microfibrils
of cellulose-like polysaccharides within the ground substance secreted
by epithelial cells of the mantle (p. 15). The metal chromogen of the
cell is a powerful reducing agent and since the morula cell disintegrates
in the test substance it is logical to assume that its prime role is to
function in a reducing capacity. In view of the necessity to produce the
fibrils in d i i it may be that the reaction is in some way concerned with
81
Rimilar to the vanadium compound of t,he Ascidiidae and probably
serves t i Similar function.
1). Agylutination
According to Hecht ( 1 91 8c), IWton ( 1920) and Vallee (1967a,
1987b, 1968) the blood of ascidians docs not clot but in drawn blood
tfie cdls aggregate anti if left standing for some time separate again.
Vullee (tfK8) hiw shown that! the vcmrdocytm have free SH groups
which bind to OIK! another in ugglotinirt~ioil hut! can alternatively bind
to a free 8H group in cysttine whicbh Imv(?nts agglutination. Anderson
( 1 97 1) also found that vanadocytes aggregated around foreign bodies
impltmtcd in the tissues and were capable of secreting a protective
layer of test material over such bodies. In addition Fuke and Sugai
(1972) report that the body fluid of two species of ascidian (8tyela
p2icatn and Halocynthia h(i2gendorf i (Oka) ) contains haemagglutinins
which cause aggregation of mammalian erythrocytes but does not
aggregate blood cells of other ascidian species. Unlike other haemagglutinins the substance in ascidian fluids is a polysaccharide and not a
protein.
E. Blood function
It is possihle now to consider the role anti function of various types
of cell in asoidian blood. ‘I’ht. Z?pphocylc wems to be a transient multipotent cell type which can give rise to a11 other blood cells as required.
Vacuolar amoehocytca, signet-ring oc4s und compartment c:olls arc dcvclopmental phases in the formation of morula c-c4ls which are ooncc*rrit:d with
test formation. Morula cells contaiii organic. compounds of h w v y
metals notably vanadium or iron, but there is no evidence to suggwt
that these play a role in oxygen transport (Webb, 1939). The metabolic
level of ascidians is low anti Goodbody and Youriq (unpublished data)
have shown that oxygen consumption in Ascidia nigra ranges from
806 to 1630 pl/h/g ; t t specific oxygen carrier in the blood seems unnecessary. The precise role of the morula cell in test formation is still
unclear, but is most likely concerned with the deposition of microfibrils
of cellulose-like polysaccharides within the ground substance secreted
by epithelial cells of the mantle (p. 15). The metal chromogen of the
cell is a powerful reducing agent and since the morula cell disintegrates
in the test substance it is logical to assume that its prime role is to
function in a reducing capacity. In view of the necessity to produce the
fibrils in d i i it may be that the reaction is in some way concerned with