I . Ibarrola et al. J. Exp. Mar. Biol. Ecol. 252 2000 199 –219
203
2.4. Statistical procedures Significant effects promoted by food quality ql and quantity qn on histological
measurements and enzyme activities in the acute and acclimated responses of cockles were analyzed by performing two factor analysis of variance Zar, 1984. The arcosin
transformation was used to normalize the data corresponding to histological parameters which are expressed as percentage. The effect promoted by acclimation to the different
diets was analyzed by testing for significant differences t-test between the mean values obtained for the acute and acclimated responses.
Possible functional relationship between enzyme activities and digestive structures was analyzed by calculation of the correlation indexes between specific activities and
volume densities of the different digestive structures.
3. Results
3.1. Stereology of the digestive tubule Table 1 shows the results of the stereological analysis. Digestive and basophilic cells
account, respectively, for 60–70 and 13–17 of the volume of the digestive tubules irrespective of the feeding condition. Cellular fragments represent a minor proportion of
the total volume maximum value of 11.5. Significant differences exerted by food quality and quantity on the histological parameters of cockles fed for 3 and 11 days are
shown in Table 2. In the acute response, the proportion of digestive cells increased with rising rations of low quality food and decreased with increasing rations of high quality
Table 1
a
Volumetric fractions of the main components of the digestive tubules Diet
VF VF
VF VF
D B
L F.S.
S 0.65960.060
0.16860.057 0.13960.088
0.03460.024
3
S 0.67360.078
0.09960.039 0.17960.039
0.04760.086
11
Ll 0.61060.112
0.13560.036 0.14060.037
0.11560.103
3
Ll 0.67260.038
0.14660.023 0.12960.051
0.05360.010
11
Lh 0.68360.042
0.16460.032 0.10860.010
0.04560.019
3
Lh 0.69460.021
0.15860.023 0.10760.034
0.04160.013
11
Hl 0.72360.028
0.16660.026 0.08360.020
0.03060.015
3
Hl 0.63960.125
0.14460.023 0.15660.031
0.06160.094
11
Hh 0.61260.051
0.15060.028 0.14160.034
0.09760.065
3
Hh 0.65260.066
0.19560.032 0.12560.078
0.02960.010
11 a
VF , volumetric fraction of digestive cells; VF , volumetric fraction of basophilic cells; VF , volumetric
D B
L
fraction of the light of the tubules; VF , volumetric fraction of fragmentation spherules. Values are
F.S.
means6S.D. n 5 5. S, starved; Ll, low quality food dosed at low ration; Lh, low quality dosed at high ration; Hl, high quality food dosed at low ration; Hh, high quality food dosed at high ration. The subindex 3 and 11
are used to indicate, respectively, acute 3 days and acclimated 11 days responses. Significant differences Fischer, P , 0.05 between short and long-term responses.
204 I
. Ibarrola et al. J. Exp. Mar. Biol. Ecol. 252 2000 199 –219 Table 2
Summary of the two factor analysis of variance testing the effects of food quality ql and quantity qn on the histological measurements recorded in the acute response
Source of variation df
MS SS
F P
Acute response Stereology of digestive tubules
Digestive cells ql
1 7.7
7.7 0.490
0.4939 qn
1 7.582
7.582 0.479
0.4987 Interaction
1 154.179
154.179 9.814
0.0064 Error
16 251.371
15.711 Basophilic cells
ql 1
3.019 3.019
0.503 0.4885
qn 1
1.507 1.507
0.251 0.6232
Interaction 1
17.391 17.391
2.896 0.1081
Error 16
96.083 6.005
Cellular fragments ql
1 14.013
14.013 0.402
0.5351 qn
1 2.520
2.520 0.072
0.7915 Interaction
1 238.747
238.747 6.846
0.0187 Error
16 658.024
34.876 Morphometry of the digestive tubules
Mean epithelial thickness MET ql
1 31.715
31.715 3.469
0.0810 qn
1 2.930
2.93 0.320
0.5792 Interaction
1 29.890
29.890 3.269
0.0894 Error
16 146.272
9.142 Mean diverticular radium MDR
ql 1
12.845 12.845
0.760 0.3964
qn 1
59.027 59.027
3.490 0.0801
Interaction 1
13.168 13.168
0.779 0.3906
Error 16
270.576 Classification of digestive tubules
Absorptive phase ql
1 1594.077
1594.077 9.368
0.0075 qn
1 247.709
247.709 1.456
0.2452 Interaction
1 339.768
339.768 1.997
0.1768 Error
16 2722.621
170.116 Disintegrating phase
ql 1
1485.398 1485.398
8.429 0.0111
qn 1
258.337 258.337
1.435 0.2485
Interaction 1
344.118 344.118
1.911 0.1768
Error 16
2881.154 180.072
Stereology of lysosomes Volume density VD
26 26
ql 1
3.92 3 10 3.92 3 10
0.767 0.3942
25 25
qn 1
1.20 3 10 1.20 3 10
2.345 0.1452
25 25
Interaction 1
2.38 3 10 2.38 3 10
4.667 0.0462
25 26
Error 16
8.18 3 10 5.12 3 10
Numerical density ND
25 25
ql 1
7.94 3 10 7.94 3 10
12.678 0.0026
27 27
qn 1
1.03 3 10 1.03 3 10
0.016 0.8994
26 26
Interaction 1
3.41 3 10 3.41 3 10
0.545 0.4713
I . Ibarrola et al. J. Exp. Mar. Biol. Ecol. 252 2000 199 –219
205
Table 2. Continued Source of variation
df MS
SS F
P
24 26
Error 16
1.00 3 10 6.23 3 10
Surface to volume ratio S V ql
1 2.771
2.771 6.417
0.0221 qn
1 1.312
1.312 3.038
0.1005 Interaction
1 1.429
1.429 3.309
0.0877 Error
16 6.910
0.432 Surface density SD
25 25
ql 1
2.11 3 10 2.11 3 10
0.547 0.4704
25 25
qn 1
5.72 3 10 5.72 3 10
1.481 0.2412
24 24
Interaction 1
1.55 3 10 1.55 3 10
4.026 0.0620
24 25
Error 16
6.18 3 10 3.86 3 10
Acclimated response Stereology of digestive tubules
Digestive cells ql
1 24.244
24.244 1.254
0.279 qn
1 5.182
5.182 0.268
0.611 Interaction
1 0.606
0.606 0.031
0.862 Error
16 309.347
19.334 Basophilic cells
ql 1
8.141 8.141
2.099 0.169
qn 1
27.990 27.990
7.218 0.016
Interaction 1
10.629 10.629
2.741 0.117
Error 16
62.043 3.878
Cellular fragments ql
1 13.938
13.938 0.560
0.465 qn
1 16.895
16.895 0.679
0.422 Interaction
1 0.244
0.244 0.010
0.922 Error
16 397.925
24.870 Morphometry of the digestive tubules
Mean epithelial thickness MET ql
1 5.222
5.222 0.399
0.537 qn
1 10.909
10.909 0.833
0.375 Interaction
1 7.222
7.222 0.552
0.468 Error
16 209.503
13.094 Mean diverticular radium MDR
ql 1
15.247 15.247
0.753 0.398
qn 1
9.091 9.091
0.445 0.514
Interaction 1
57.570 57.570
2.843 0.111
Error 16
324.039 20.252
Classification of digestive tubules Absorptive tubules
ql 1
505.515 505.515
1.805 0.198
qn 1
111.723 111.723
0.399 0.537
Interaction 1
6.856 6.856
0.024 0.877
Error 16
4481.453 280.091
Disintegrating phase
206 I
. Ibarrola et al. J. Exp. Mar. Biol. Ecol. 252 2000 199 –219 Table 2. Continued
Source of variation df
MS SS
F P
ql 1
483.439 483.439
1.598 0.224
qn 1
104.014 104.014
0.344 0.566
Interaction 1
6.555 6.555
0.022 0.885
Error 16
4841.422 302.589
Stereology of lysosomes Volume density VD
25 25
ql 1
5.3 3 10 5.3 3 10
1.983 0.183
25 25
qn 1
1.8 3 10 1.8 3 10
0.679 0.425
29 29
24
Interaction 1
6.1 3 10 6.1 3 10
2.29 3 10 0.988
25 24
Error 13
2.6 3 10 3.4 3 10
Numerical density ND
27 27
ql 1
8.2 3 10 8.2 3 10
0.069 0.797
25 25
qn 1
2.9 3 10 2.9 3 10
2.476 0.140
26 29
Interaction 1
1.7 3 10 6.1 3 10
0.141 0.713
25 24
Error 13
1.2 3 10 1.5 3 10
Surface to volume ratio S V ql
1 0.162
0.162 0.169
0.688 qn
1 2.166
2.166 2.251
0.157 Interaction
1 0.121
0.121 0.126
0.728 Error
13 0.962
12.507 Surface density SD
24 24
ql 1
1.2 3 10 1.2 3 10
2.528 0.136
26 26
qn 1
9.4 3 10 9.4 3 10
0.205 0.658
27 27
Interaction 1
6.0 3 10 6.0 3 10
0.013 0.910
25
Error 13
4.6 3 10 0.001
food Table 1, and thus, the interaction ql 3 qn appears as a significant factor affecting VF
Table 2. Consistently, the inverse trend is evident for VF . Significant
D CF
modifications of the volumetric fractions of the digestive tubules of cockles after acclimation to diets have been indicated with asterisks in Table 1. The volumetric
fraction of basophilic cells increased significantly in cockles acclimated to Hh diet whereas decreased significantly after prolonged starvation.
3.2. Morphometry of the digestive tubules Results of the planimetric analysis of tubules have been plotted in Fig. 1. Two factor
variance analysis performed for both short- and long-term responses Table 2 indicates no significant differences in mean diverticular radium and mean epithelial thickness of
tubules from cockles fed on different food qualities and rations. In the short-term 3 days response, mean diverticular radius MDR of digestive
tubules of starved cockles were not significantly different to that of cockles fed on Ll
3
diet. However, cockles presenting higher ingestion rates of organic matter i.e. Lh , Hl
3 3
and Hh had significantly bigger tubules and presented larger standard deviations than
3
starved ones. After acclimation, MDR increased in all feeding conditions Fig. 1, however, since standard deviations also rose, this generalized increment was not
statistically significant in the variance analysis shown in Table 2. In consequence, after
I . Ibarrola et al. J. Exp. Mar. Biol. Ecol. 252 2000 199 –219
207
Fig. 1. Mean diverticular radium mm and mean epithelial thickness mm of cockles starved S or fed different food quantities and qualities Ll, Lh, Hl and Hh for 3 days hollow bars and 11 days solid bars.
Values are means6S.D. n 5 5. The asterisks indicate significant differences between mean values from the 3rd and 11th day t-test, P , 0.005.
208 I
. Ibarrola et al. J. Exp. Mar. Biol. Ecol. 252 2000 199 –219
acclimation, cockles were found to have significantly higher MDR than starved ones in all feeding conditions.
Both epithelial thickness and diverticular radius are one-dimensional measurements characterizing a three-dimensional structure. Thus, slight changes in such measurements
are likely to represent large variations in terms of volume. Total volume of a tubule can
3
be considered to be proportional to the cubic of the diverticular radius MDR . In Fig.
3
2, mean dry weight shown in Table 5 is plotted against the estimated mean MDR to analyze to what extent the weight increase of the gland could be attributed to the size
increment of digestive tubules. As previously reported Ibarrola et al., 1996, 1998b, the increment of the dry weight of the gland may play a significant role in the enzymatic
response of the cockles. A good correlation is evident between both parameters with the exception of cockles acclimated to Lh and Hh whose digestive gland weight lay above
the relationship.
3.3. Classification of digestive phases Table 3 shows the percentage of the different tubule types in the digestive gland of
cockles. In all conditions, including starved cockles, disintegrating tubules account for the main proportion of tubules Hl diet being the exception in the sense that absorptive
3
Fig. 2. Dry weight mg of the digestive gland as a function of the estimated volume of a single digestive tubule in cockles fed different diets Ll, triangles; Lh, rhombs; Hl, circles and Hh, squares for 3 days hollow
symbols and 11 days solid symbols. Estimation of a tubule equivalent volume was calculated as its
3 3
corresponding mean MDR . Values are means6S.D.; n 5 10, for the dry weight and 5 for MDR . The line was fitted by eye.
I . Ibarrola et al. J. Exp. Mar. Biol. Ecol. 252 2000 199 –219
209 Table 3
a
Classification of digestive phases Diet
A D
H R
S 33.2618.5
58.0625.3 8.8610.4
3
S 38.0624.8
49.6630.4 12.467.3
11
Ll 16.8614.0
82.0615.2 1.261.8
3
Ll 26.2621.0
71.8622.9 2.062.0
11
Lh 16.8611.4
82.0613.9 1.262.7
3
Lh 30.0614.4
68.0616.3 2.063.5
11
Hl 55.6613.0
44.0612.3 0.460.9
3
Hl 39.6628.9
58.4629.8 2.063.5
11
Hh 31.2631.5
68.8631.5
3
Hh 48.4632.8
50.0633.4 0.460.9
1.262.7
11 a
Results are expressed as percentage. A, absorptive phase; D, disintegrating phase; H, holding phase; R, reconstituting phase. Values are means6S.D. n 5 5. S, starved; Ll, low quality food dosed at low ration;
Lh, low quality dosed at high ration; Hl, high quality food dosed at low ration; Hh, high quality food dosed at high ration. The subindex 3 and 11 are used to indicate, respectively, acute 3 days and acclimated 11 days
responses.
tubules are prevalent over disintegrating. Holding and reconstituting tubules accounted only for a marginal proportion. Cockles fed high quality diets for 3 days had
significantly higher proportions of tubules in absorptive phase and lower proportions in disintegrating phase than those fed low qualities, thus, food quality appears as a
significant factor in variance analysis shown in Table 2. These differences were lost after acclimation Table 2.
3.4. Stereology of lysosomes Results of the stereological analysis of lysosomes are shown in Table 4. The presence
of food affected significantly the characteristics of the lysosomal system in less than 3 days and, thus, the volume density was significantly lower in starved than in fed cockles.
Furthermore, the lysosomal volume density appears to increase with improved feeding condition: cockles fed Ll
diet had significantly higher t-test, P , 0.005 lysosomal
3
density than starved ones but significantly lower than those fed the remaining diets. Accordingly, Table 2 shows that the interaction term ql 3 qn affects significantly
lysosomal volume density. Significant modifications during acclimation have been indicated in Table 4: whereas
starvation brought a slight not significant reduction of the volume density of lysosomes, feeding activity increased the volume density of lysosomes in all feeding
conditions. However, the effect was dependent on food quality: whereas the increase of lysosomal density was intense and significant in cockles fed low quality diets 3 2.5 to
2 times for Ll and Lh respectively, with high qualities, the increase was moderate and statistically not significant. In consequence, the differences between cockles fed different
food qualities was reduced after acclimation Table 2. Since lysosomes are the specific organelles dealing with intracellular digestion within the digestive gland, in Fig. 3 we
210 I
. Ibarrola et al. J. Exp. Mar. Biol. Ecol. 252 2000 199 –219 Table 4
a
Stereological parameters characterizing the lysosomal system from digestive cells of the digestive gland Diet
VD ND
S V SD
23 23
23
S 2.86 3 10
61.11 3 10 0.01060.003
5.63660.707 0.01665.01 3 10
3 23
24 23
23
S 1.65 3 10
66.58 3 10 0.01061.93 3 10
7.32860.561 0.01263.83 3 10
11 23
23 23
23
Ll 5.15 3 10
61.36 3 10 0.01262.87 3 10
4.74460.917 0.02465.54 3 10
3 23
23 23
23
Ll 0.01367.34 3 10
8.26 3 10 63.21 3 10
3.04961.426 0.03469.36 3 10
11 23
24 23
23
Lh 8.88 3 10
69.18 3 10 0.01362.94 3 10
3.69760.299 0.03363.86 3 10
3 23
23 23
23
Lh 0.01663.32 3 10
4.92 3 10 61.41 3 10
2.14660.420 0.03261.24 3 10
11 23
23 23
23 23
Hl 8.22 3 10
63.30 3 10 8.78 3 10
62.34 3 10 3.46560.646
0.02768.80 3 10
3 23
23 23
23
Hl 0.01063.44 3 10
8.07 3 10 63.68 3 10
3.07660.668 0.02965.95 3 10
11 23
23 23
23 23
Hh 7.58 3 10
62.62 3 10 7.81 3 10
61.67 3 10 3.48760.617
0.02565.63 3 10
3 23
23 23
23
Hh 0.01264.55 3 10
6.02 3 10 64.34 3 10
2.51960.865 0.02865.94 3 10
11 a
VD, volume density; ND, numerical density; S V, surface to volume ratio; SD, surface density. Values are means6S.D. n 5 5. S, starved; Ll, low quality food dosed at low ration; Lh, low quality dosed at high ration;
Hl, high quality food dosed at low ration; Hh, high quality food dosed at high ration. The subindex 3 and 11 are used to indicate, respectively, acute 3 days and acclimated 11 days responses.
Indicates significant differences Fischer test for P 5 0.05 between short- and long-term responses.
have analyzed the relationship between lysosomic parameters and ingestion rate of organic matter reported in the preceding publication. The figure shows that: a both
volume and surface density of lysosomes rose to saturation with increasing organic ingestion rate, both in the acute and acclimated responses. b For a given value of
organic ingestion rate, corresponding VD is higher after acclimation to the diet. c Increments in lysosomal volume density with rising ingestion rate occurred as a
consequence of a strong increment of the lysosomal size see S V and in spite of reduction of the numerical density ND.
3.5. Enzyme activities in the digestive gland Dry weight, protein contents and specific enzyme activities mg of end-product per
mg protein per hour of the digestive glands are shown in Table 5. Resulting total activities mg of end-product per digestive gland per hour have been plotted in Fig.
4a–d. Significant modifications after acclimation have been indicated with asterisks. Two-factor variance analysis testing for significant effects of food quality and quantity
in the acute and acclimated responses are shown in Table 6.
In the acute response, both quantity and quality exerted significant positive effects on the dry weight of the digestive gland Table 6. The changes in the soluble protein
content were not statistically significant. Total protease and cellulase activities were significantly higher in cockles fed on high than on low food rations. The increase of
protease activity was especially high in cockles fed Lh diet, due to the simultaneous increment of the dry weight of the digestive gland and the specific protease activity.
Conversely, no significant changes were recorded for total amylase and laminarinase Table 6.
Enzymatic acclimation to the diets could be described as a process involving a
I . Ibarrola et al. J. Exp. Mar. Biol. Ecol. 252 2000 199 –219
211
Fig. 3. Stereological parameters of the lysosomic system of cockles starved 3 days, solid star; 11 days, asterisks and fed different diets Ll, triangles; Lh, rhombs; Hl, squares; Hh, circles for 3 days hollow
symbols and 11 days solid symbols. Values are means6S.D. n 5 5.
generalized increment of dry weight of the gland, especially in cockles fed concentrated rations, that brought about increased activities of cellulase, laminarinase and proteases
but not amylases see the statistical significance of qn on Table 2. Food quality exerted a further differential effect: increment of cellulase and especially laminarinase activities
with increasing food concentrations were more pronounced in cockles acclimated to high quality diets Hh , see Table 5.
11
3.6. Correlation between histological parameters and enzyme activities Should a given enzyme activity be produced by a particular digestive structure, the
relative enrichment or impoverishment of the gland in such structure could be expected to exert modifications in the specific activity of the enzyme. Thus, with the aim to
establish possible functional relationships between enzymatic and histological parame- ters we have performed simple correlation analyses between specific enzyme activities
212 I
. Ibarrola et al. J. Exp. Mar. Biol. Ecol. 252 2000 199 –219 Table 5
Dry weight W ; mg, percentage of soluble protein p and specific enzyme activities of the digestive
DG 21
21 a
gland mg of end product mg prot h
Diet W
p A
C L
P
DG spc
spc spc
spc
S 15.964.6
22.161.1 1.1560.25
0.3160.13 0.3660.26
0.2360.04
3
Ll 17.962.6
23.061.8 0.8660.10
0.2760.07 0.2860.11
0.3060.08
3
Ll 20.664.1
20.661.7 0.8760.18
0.3160.13 0.1760.11
0.3760.06
11
Lh 24.166.6
21.562.2 0.8660.15
0.3560.09 0.2960.11
0.4360.02
3
Lh 35.064.9
21.860.9 0.6960.10
0.3460.08 0.2560.08
0.5160.08
11
Hl 22.864.0
21.561.9 0.8960.17
0.3160.12 0.2860.12
0.4160.09
3
Hl 26.466.1
21.662.9 0.6860.23
0.2960.12 0.3260.13
0.4260.07
11
Hh 25.763.5
21.862.2 0.7760.16
0.3360.09 0.2660.06
0.3260.04
3
Hh 35.766.0
21.861.1 0.4660.11
0.3560.09 0.3860.06
0.4760.04
11 a
Values are means 6S.D. n 5 10. S, starved, S not determined; Ll, low quality food dosed at low
11
ration; Lh, low quality dosed at high ration; Hl, high quality food dosed at low ration; Hh, high quality food dosed at high ration. The subindex 3 and 11 are used to indicate, respectively, acute 3 days and acclimated
11 days responses. Indicates significant differences Fischer test for P 5 0.05 between short- and long-term responses.
Fig. 4. Mean values 6S.D. of total enzyme activities of cockles starved S or fed different food quantities and qualities Ll, Lh, Hl and Hh for 3 days hollow bars and 11 days solid bars; n 5 10. The asterisks
indicate significant differences between mean values from the 3rd and 11th day t-test, P , 0.005.
I . Ibarrola et al. J. Exp. Mar. Biol. Ecol. 252 2000 199 –219
213 Table 6
Summary of ANOVA testing the effects of food quality ql and quantity qn on the dry weight, protein content and total enzyme activities of the digestive gland
Source of variation df
MS SS
F P
Acute response Dry weight
ql 1
104.65 104.65
5.29 0.027
qn 1
208.39 208.39
10.53 0.002
Interaction 1
29.41 29.41
1.49 0.231
Error 36
712.74 19.80
Protein content
24 24
ql 1
3.76 3 10 3.76 3 10
0.92 0.344
24 24
qn 1
3.69 3 10 3.69 3 10
0.90 0.348
24 24
Interaction 1
8.60 3 10 8.60 3 10
2.10 0.156
24
Error 36
0.01 4.09 3 10
Total amylase ql
1 0.62
0.62 0.75
0.392 qn
1 2.16
2.16 2.61
0.116 Interaction
1 2.80
2.80 3.37
0.075 Error
33 27.36
0.83 Total cellulase
ql 1
0.16 0.16
0.51 0.479
qn 1
2.64 2.64
8.18 0.007
Interaction 1
0.56 0.56
1.75 0.195
Error 33
10.64 0.32
Total laminarinase
24 24
23
ql 1
1.94 3 10 1.94 3 10
6.76 3 10 0.935
qn 1
0.67 0.67
2.34 0.136
Interaction 1
0.44 0.44
1.75 0.223
Error 33
9.47 0.28
Total protease ql
1 0.09
0.09 0.48
0.494 qn
1 1.48
1.48 7.94
0.008 Interaction
1 3.75
3.75 20.15
0.000 Error
33 6.5
0.19 Acclimated response
Dry weight ql
1 103.01
103.01 3.55
0.068 qn
1 1334.56
1334.56 45.96
0.000 Interaction
1 62.03
62.03 2.13
0.153 Error
34 987.32
29.04 Protein content
24 24
ql 1
2.67 3 10 2.67 3 10
0.77 0.386
24 24
qn 1
4.53 3 10 4.53 3 10
1.30 0.261
24 24
Interaction 1
2.30 3 10 2.30 3 10
0.66 0.421
24
Error 34
0.01 3.47 3 10
Total amylase ql
1 5.44
5.44 4.89
0.034 qn
1 4.09
4.09 3.68
0.063 Interaction
1 6.97
6.97 6.26
0.017 Error
34 37.80
1.11
214 I
. Ibarrola et al. J. Exp. Mar. Biol. Ecol. 252 2000 199 –219 Table 6. Continued
Source of variation df
MS SS
F P
Total cellulase ql
1 0.41
0.41 0.73
0.399 qn
1 13.63
13.63 24.35
0.000 Interaction
1 0.28
0.28 0.50
0.482 Error
34 19.03
0.56 Total laminarinase
ql 1
10.55 10.55
20.61 0.000
qn 1
13.10 13.10
25.58 0.000
Interaction 1
0.01 0.01
0.03 0.857
Error 34
17.41 0.51
Total protease ql
1 1.17
1.17 1.84
0.184 qn
1 29.77
29.77 46.91
0.000 Interaction
1 2.65
2.65 9.17
0.049 Error
34 21.57
0.63
C , L
and P from Table 5 and lysosomal volume densities VD from Table 4 as
spc spc
spc
well as the relative abundance of cell types in the digestive gland FV , FV , from Table
B D
1. Since individuals used in enzymatic and histological determinations were different, mean values have been used in the analysis. Results are presented in the form of a
correlation matrix in Table 7. Specific protease activity had a high correlation index with lysosome volume density VD, while specific cellulase and laminarinase activities were
correlated with the volume fraction of basophilic cells. A significant negative correlation between specific amylase and lysosomal VD was also found.
4. Discussion
