1
Effects of food quality and starvation on the optimal
2
foraging behavior of Daphnia magna (Cladocera)
3
Xu Wang Yin*, Sha Sha Zhu, Jian Huang, Peng Fei Liu
4
Liaoning Provincial Key Laboratory for Hydrobiology, College of Life Science and Technology,
5
Dalian Ocean University, Dalian 116023, China
6
*
Author for corresponding: [email protected]
7
8
9
Abstract: In the present work we evaluated the feeding selectivity of starved Daphnia magna on
10
two freshwater green algae Chlamydomonas sajao and Chlorella pyrenoidosa. Compared to C.
11
pyrenoidosa, food quality of C. sajao are better in food palatability (cell size and digestibility), but
12
poor in nutritional content (total carbon content). D. magna was starved for 0 and 8 d, and then
13
was allowed to graze on a mixture of C. sajao and C. pyrenoidosa with following proportion: 5 ×
14
104 : 35 × 104 cells ml-1, 20 × 104 : 20 × 104 cells ml-1 and 35 × 104 : 5 × 104 cells ml-1. The results
15
indicated that the ingestion rate and filtration rate of starved D. magna, comparing with satiated
16
groups, on C. pyrenoidosa increased significantly, while, inverse trends was observed in C. sajao.
17
Base on selectivity coefficient of D. magna, we observed that when D. magna was in satiation C.
18
sajao will be preferred, while, C. pyrenoidosa will be selected when D. magna was in starvation,
19
and moreover, these foraging behaviors were not influenced by the relative food abundance of
20
each green alga. Therefore, a tradeoff between food palatability (physical makeup) and food
21
nutritional content (chemical composition) can be hypothesized in the foraging behavior of D.
22
magna, which is modified by the starvation of feeder. High valuable food is always selected by D.
23
magna as predicted by optimal foraging theory. However, when D. magna is in satiation food diets
24
with adequate size and easy digestibility will be preferred, while, those foods with relatively
25
higher lipid or total carbon content will be selected when D. magna is in starvation.
26
Key Words: ingestion rate；filtration rate；selectivity coefficient；Chlamydomonas sajao；
27
Chlorella pyrenoidosa
28
29
30
Introduction
31
In freshwater ecosystems, filter zooplankton faced a variety of food resources, varying greatly
32
in size, digestibility, nutritional values and abundance[1]. According to the optimal foraging theory,
33
diet selection by feeders depend on food size, searching time, handling time, nutrition content and
34
assimilation efficiency, all of which is to maximize net energy gains by feeders[2]. The ability of
-1-
35
zooplankton to select optimal food items in the face of a mixture food resources comprising of
36
high and low quality food will maximize the fitness of grazers, and help them persist the
37
populations in competing with other aquatic organisms[3].
38
Phytoplankton is the major food diet for filter zooplankton, and food quality of algae usually
39
lies on the palatability and nutritional value. Food palatability can also be defined as physical
40
makeup, involving digestibility and particle size, and moreover, food nutritional value is also
41
regarded as chemical composition, including lipid composition, total carbon content and
42
stoichiometric concentration of carbon and phosphorous[4~7]. On one hand, numerous data
43
documented the capability of filter zooplankton (e.g. copepods and cladocera) to discriminate food
44
value based on physical makeup of algal particles, which revealed that copepods and cladocera
45
grazed more efficiently on naked and relative large but with intermediated size algae, e.g.
46
Cryptomonas and Chlamydomonas, since energy expenditure of feeders to collect and digest these
47
algae was lower than that of small sized and thick cell wall packaged algae, e.g. Chlorella[8]；On
48
the other hand, some studies also verified the ability of filter zooplankton (e.g. cladocera) to feed
49
preferentially on algal foods with higher total carbon content , because algal foods, superior in
50
chemical composition (e.g. eicosapentaenoic acid, docosahexaenoic acid and total organic carbon),
51
could afford more metabolic energy and would support higher survival and reproduction for
52
feeders[5]. Obviously, it should be advantageous for feeder to select good food particles valuable in
53
both physical makeup and chemical composition. However, when paired of food algae vary in
54
terms of physical makeup and chemical composition, with one being good quality in cell size and
55
digestibility and another being high value in lipid composition and total carbon content, which
56
food alga will be selected by the feeder. In this condition the feeder may indulge in a dilemma.
57
Several laboratory works showed that filter zooplankton usually discriminated food quality
58
based on physical makeup and often selected naked and intermediated size food algae. In these
59
studies, animals were often well fed and did not experience starvation. [6 8 9]. In some circumstance,
60
e.g. peak animal density, vertical migration or clear water phase, food availability became
61
extremely low that filter zooplankton was starved for hours to weeks[10]. During the starvation,
62
zooplankton would utilize additional energy reserves in the body, e.g. lipid, protein and
63
carbohydrate [11~13]. When the food emerged again in the environment, algal species with relatively
64
higher total carbon content might become high quality food and should be preferred by starved
65
zooplankton, because this foraging behavior could increase the rate of carbon storage in the body
66
of zooplankton. Selection would favor this foraging strategy, because it allowed a faster recover in
67
metabolic process and reproduction of starved animals when the hunger ceased, which might
68
improve the competitive ability of these animals to some extend. Therefore, a tradeoff between
69
food palatability (physical makeup) and food nutritional content (chemical composition) can be
、、
-2-
70
hypothesized in the foraging behavior of filter feeder, which is modified by the starvation of feeder.
71
High valuable food is always selected by filter feeder as predicted by optimal foraging theory.
72
However, when the feeder is in satiation food diets with adequate size and easy digestibility will
73
be preferred, while, those foods with relatively higher lipid or total carbon content will be selected
74
when the feeder is in starvation. To test this hypothesis we used two freshwater algae Chlorella
75
pyrenoidosa and Chlamydomonas sajao, and Daphnia magna, a common herbivorous zooplankton
76
in freshwater lakes and ponds, to establish grazing experiments.
77
Chlorella and Chlamydomonas are two common freshwater green algae, which are potential
78
dietary food for Daphnia. Previous studies showed that small sized Chlorella (usually 2-5 µm) had
79
heavy cell wall, and compared to Chlorella, Chlamydomonas have relatively larger size (usually
80
6-10 µm) and often do not have sturdy cell walls [14
81
with intersetular of limbs, distance of which often ranged from 3—9 µm in adult Daphnia[3
82
indicating that small-sized Chlorella may approaches the lower limits of filter ability of D. magna
83
and is more difficult to collect than large-sized Chlamydomonas. Therefore, the food quality of
84
Chlamydomonas is higher than Chlorella in terms of food palatability. However, some works also
85
revealed that lipid content of Chlorella was higher than Chlamydomonas[7
86
reproduction of D. magna fed with Chlorella was significant higher than that of
87
Chlamydomonas[18], which could be indirect evidence to measure the nutritional content of algal
88
foods. Thus, the food quality of Chlorella is higher than Chlamydomonas in terms of food
89
nutritional content.
、15]
. Daphnia usually collect planktonic algae
、16、17]
,
、14]
, and moreover, the
90
91
Materials and Methods
92
Culture of algae and Daphnia
93
The freshwater green algae Chlamydomonas sajao (307.5 µm3, n=50) and Chlorella
94
pyrenoidosa (26.5 µm3, n=50) were purchased from the Institute of Hydrobiology, Chinese
95
Academy of Sciences and cultured in SE medium[8]. A clone of D. magna was collected from an
96
artificial freshwater pond located in Jilin Agriculture University, China and also cultured in SE
97
medium. Everyday Daphnia were fed with a mixture of C. sajao and C. pyrenoidosa at a
98
concentration of approximately 1 mg C l-1. The culture medium was renewed every week. All
99
Daphnia and algal cultures in experiments were kept at 20 ± 1.0 ℃ in a 14:10 (L:D) photoperiod
100
(illuminance ≈ 50 µEin m-2 s-1) in a growth chamber.
101
Feeding selectivity of Daphnia in relation to starvation
102
The grazing experiments were carried out with adult female Daphnia (2.9 mm in body length,
103
n=50) from the third or later clutches of offspring. To eliminate the influence of intra-specific
104
interaction of filter feeder on the algae grazing[9], D. magna was individually introduced into the
-3-
105
experimental culture plate, containing 10 ml SE medium. Prior to the grazing experiments, adult
106
females were placed into fiber filtered (0.45 µm filter) SE medium and starved for 8 d (medium
107
was renewed every day). Adult females that were not starved were treated as control groups.
108
To test the ability of Daphnia to select food from mixtures of algae particles, a mixture of C.
109
sajao and C. pyrenoidosa with following proportion: 5 × 104 : 35 × 104 cells ml-1, 20 × 104 : 20 ×
110
104 cells ml-1 and 35 × 104 : 5 × 104 cells ml-1 was added to the experimental environments. A
111
single control plate, containing algae but no Daphnia, was always used. All experiments were run
112
at 20 ℃ in continuous dark. To minimize any potential influences with differential sinking of
113
Chlamydomonas and Chlorella cells in the experimental environments, every 30 min, the algae in
114
the mixtures was equally mixed by slightly blowing the medium with pipette.
115
The animals were allowed to graze for 3 h before they were removed from the container, and
116
then the algae were preserved with Logol’s solution. Two aliquot samples of 0.1 ml were obtained
117
from the preserved medium and pipetted into Palmer-Maloney counting chamber, respectively.
118
Mean particle counts of each aliquot sample were based upon the random counting of 100 fields at
119
400 × magnification. At least 100-200 cells were counted under microscope for each green algal
120
species. Each grazing and control experiment was run in 10 and 3 replicates, respectively.
121
The algal-specific filtration rate (FR), defined as the volume of water from which a Daphnia
122
individual removed all algal cells per unit time (ml ind.-1 hr-1), was calculated following the
123
equation: FR= IR/[algal cell], where IR is the ingestion rate of algal cells in cells ind.-1 hr-1 and in
124
which algal concentration is expressed as cells ml-1[19]. Food selectivity of D. magna was
125
quantified by the selectivity coefficient (α), where α was the ratio of the filtration rate on Chlorella
126
to the sum of filtration rates on both algae and the value of which ranged from 0 to 1[20]. A
127
preferential foraging behavior on Chlamydomonas would result in an α value < 0.5, and an α
128
value > 0.5 indicated a preference for Chlorella.
129
Nutritional evaluation of two freshwater algae
130
We used total carbon content of algal cell to quantify the nutritional content of C. pyrenoidosa
131
and C. sajao[5], which was analyzed with a total organic carbon analyzer (SHIMADZU, TOC-V
132
CPH). For each algal species, carbon contents of eight samples were tested. In order to determine
133
the overall nutritional quality of C. pyrenoidosa and C. sajao, life history characteristics of D.
134
magna fed each algal food were evaluated. Two sets of 12 neonate Daphnia (old < 12 h) from the
135
third or later clutches of offspring were placed individually in 6-well tissue culture plates,
136
containing 10 ml SE medium, and fed with one of the two algal foods. The concentration of C.
137
pyrenoidosa and C. sajao in each set was equal, being 3.1 × 107 μm3 ml-1 (equivalent to 1.0 × 105
138
cells ml-1 C. sajao). Each set was run in three replicates. Each day, the surviving females together
139
with eggs were transferred to fresh medium as described above, and the number of surviving
-4-
140
females and neonates was counted. The experiments ended when all individuals died.
141
142
The net reproductive rate (R0) and intrinsic population growth rate (rm) of Daphnia population
were calculated following the formulae[21]: R0 
n
n
x 0
x 0
 lx mx , rm   e rm xlx mx  1 , where lx
143
(cumulative survivorship) and mx (per capita fecundity) were taken directly from the life table
144
data.
145
Statistical analysis
146
Influences of starvation and food abundance on the algal-specific ingestion rate, filtration rate
147
and selectivity coefficient (α) of D. magna were analyzed with factorial ANOVA. Algal-specific
148
ingestion rate and filtration rate of C. sajao and C. pyrenoidosa within and between each algal
149
abundance level were compared with Student Independent T-test. The difference of total carbon
150
content of two algae and life table parameters of Daphnia fed two algae were also detected with
151
Student Independent t-test. All statistical analyses were carried out using the statistical package
152
SPSS version 12.0.
153
5
4
Chlamydomonas sajao
Chlorella pyrenoidosa
35 Cs: 5 Cp
B
-1
-1
Ingestion rate ( 10 cells ind. hr )
4
Chlamydomonas sajao
Chlorella pyrenoidosa
20 Cs: 20 Cp
A
-1
-1
Ingestion rate ( 10 cells ind. hr )
5
3
4
4
3
2
1
2
1
0
0
Control
Control
Starvation
Starvation
5
4
Fig. 1 Algal-specific ingestion rate of
Daphnia magna with mixtures of
Chlamydomonas sajao and Chlorella
pyrenoidosa varied in algal abundance under
starvation. 20Cs: 20Cp (A), 35Cs: 5Cp (B)
and 5Cs: 35Cp (C) = a mixture of C. sajao
and C. pyrenoidosa with following
proportion: 20 × 104 : 20 × 104 cells ml-1, 35
× 104 : 5 × 104 cells ml-1 and 5 × 104 : 35 ×
104 cells ml-1.
Chlamydomonas sajao
Chlorella pyrenoidosa
5 Cs: 35 Cp
C
-1
-1
Ingestion rate ( 10 cells ind. hr )
3
4
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
2
1
0
Control
Starvation
173
174
Results
175
The algal-specific ingestion rate, filtration rate and selectivity coefficient (α) of D. magna fed
176
two algal foods, varying in relative abundance, under starvation are shown in Fig. 1 and 2. The
177
starvation and food abundance produce significant difference on algal-specific ingestion rate,
-5-
178
filtration rate and α of D. magna (Table 1). The grazing efficiency of Daphnia on C. sajao
179
(Chlamydomonas) is significantly higher than C. pyrenoidosa (Chlorella) (Fig. 2, Independent
180
sample t-test, P<0.05) when Daphnia is not starved, resulting in relatively low selectivity
181
coefficients (Fig. 2), and this foraging behavior of D. magna is almost not affected by algal food
182
abundance. However when Daphnia is starved, grazing efficiency of Daphnia on Chlamydomonas
183
is obviously lower than Chlorella (Independent sample t-test, P<0.05) no matter what initial cell
184
density the two algae are, resulting in higher selectivity coefficients (Fig. 2).
185
186
0.3
0.3
1.0
0.1
0.0
1.0
-1
-1
0.5
0.1
0.0
Selectivity coefficient ( α)
Filtration rate ( ml ind. hr )
Chlamydomonas sajao
Chlorella pyrenoidosa
5 Cs: 35 Cp
C
0.2
0.0
Control
-1
-1
0.1
0.0
Control
Starvation
0.3
0.5
0.0
0.0
Control
Filtration rate ( ml ind. hr )
-1
-1
Filtration rate ( ml ind. hr )
0.5
0.2
Starvation
Starvation
Fig. 2 Algal-specific filtration rate
(striped bar and open bar) and food
selectivity coefficient α (solid circle) of
Daphnia magna with mixtures of
Chlamydomonas sajao and Chlorella
pyrenoidosa varied in algal abundance
under starvation. 20Cs: 20Cp (A), 35Cs:
5Cp (B) and 5Cs: 35Cp (C) = a mixture
of C. sajao and C. pyrenoidosa with
following proportion: 20 × 104 : 20 × 104
cells ml-1, 35 × 104 : 5 × 104 cells ml-1
and 5 × 104 : 35 × 104 cells ml-1.
209
The total carbon content of Chlamydomonas is 3.59±0.12 × 10-8 μg C μm-3, which is
210
significantly lower than that of Chlorella (5.24±0.39 × 10-8 μg C μm-3) (Table 2), indicating that
211
the food quality of Chlorella is better than Chlamydomonas in terms of total carbon content. This
212
idea is verified in life history studies, showing Daphnia population fed with Chlorella had
213
obviously an earlier reproduction, more clutches per female, more offspring per clutch, a longer
214
mean life span, higher net reproductive rate and higher intrinsic population growth rate than those
215
fed on Chlamydomonas (Table 2). Therefore, the results of grazing experiments suggest that
216
Daphnia use nutritional content as the criterion to discriminate food quality when they are in
217
starvation.
-6-
Selectivity coefficient ( α)
0.2
1.0
Chlamydomonas sajao
Chlorella pyrenoidosa
35 Cs: 5 Cp
B
Chlamydomonas sajao
Chlorella pyrenoidosa
20 Cs: 20 Cp
A
Selectivity coefficient ( α)
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
218
219
Table 1. ANOVA on different variables of food selectivity obtained in the study. SS, Sum of
squares; df, degrees of freedom; MS, mean square; F, F-ratio; P, probability of F exceeded.
Source
220
221
222
223
SS
df
MS
F
P
Ingestion rate on Chlamydomonas
Starvation (A)
Abundance of algae (B)
Interaction A × B
4.27
14.88
0.43
1
2
2
4.27
7.44
0.21
31.32
54.53
1.57
< 0.001
< 0.001
0.219
Ingestion rate on Chlorella
Starvation (A)
Abundance of algae (B)
Interaction A × B
56.24
91.32
29.22
1
2
2
56.24
45.66
14.61
259.07
210.32
67.29
< 0.001
< 0.001
< 0.001
Filtration rate on Chlamydomonas
Starvation (A)
Abundance of algae (B)
Interaction A × B
0.024
0.036
0.005
1
2
2
0.024
0.018
0.003
79.01
59.52
8.38
< 0.001
< 0.001
0.001
Filtration rate on Chlorella
Starvation (A)
Abundance of algae (B)
Interaction A × B
0.215
0.021
0.061
1
2
2
0.215
0.01
0.03
692.29
33.63
97.42
< 0.001
< 0.001
< 0.001
Selectivity coefficient (α)
Starvation (A)
Abundance of algae (B)
Interaction A × B
3.969
0.103
0.278
1
2
2
3.969
0.052
0.139
188.95
2.46
6.61
< 0.001
0.096
0.003
Table 2. Results of the food quality and life history analysis of Daphnia magna fed with
Chlamydomonas sajao (Cs) or Chlorella pyrenoidosa (Cp)
Food type
Parameter
P-value
Total carbon content (10-8 μg C μm-3)
Cs
3.59 ± 0.12
Cp
5.24 ± 0.39
0.001
Age to produce first clutch (days)
18.8 ± 0.8
12.9 ± 0.1
< 0.001
Mean clutches per female
1.5 ± 0.3
4.8 ± 0.5
< 0.001
Mean clutch size
1.8 ± 0.4
8.1 ± 0.5
< 0.001
Mean life span (days)
27.9 ± 2.5
47.8 ± 3.5
< 0.001
Net reproductive rate (R0, offspring female-1)
6.40 ± 1.19
24.55 ± 2.91
< 0.001
Intrinsic population growth rate (rm, day-1)
0.09 ± 0.02
0.21 ± 0.01
< 0.001
224
-7-
225
Discussion
226
In the present work we found that high valuable food was always selected by D. magna as
227
predicted by optimal foraging theory. However, when D. magna was in satiation, C. sajao with
228
adequate size and easy digestibility was preferred, while, C. pyrenoidosa with relatively higher
229
total carbon content was selected when D. magna was in starvation. Moreover, these foraging
230
behaviors were not influenced by the relative food abundance. Thus, there may be a tradeoff
231
between food palatability (physical makeup) and food nutritional content (chemical composition)
232
in the foraging behavior of D. magna, which is modified by the starvation of D. magna.
233
The importance of starvation in diet selection was predicted by theoretical model and tested by
234
empirical experiments with aquatic animals. The general rule of foraging strategy of feeders
235
obtained from these studies was feeding selectively on high-quality food when satiated and
236
discriminating less against low-quality food when starved[3
237
by hunger, the costs of discriminating against unwanted low valuable food would be more
238
obviously for feeders. In this circumstance the optimal foraging strategy was to decrease energy
239
expenditure spending on food handling and feed “non-selectively” on all type food as predicted by
240
‘handling costs’ hypothesis[24].
241
digestibility[3
242
preferred than small sized and sturdy cell wall packaged C. pyrenoidosa when D. magna was in
243
satiation. The grazing efficiency on C. pyrenoidosa increased greatly when D. magna was in
244
starvation, and simultaneously feeding selectively against C. sajao (Fig. 2, Table 2). These results
245
can not be explained simply with ‘handling costs’ hypothesis, because it seemed that the D. magna
246
was feeding selectively on C. pyrenoidosa after starvation, and moreover this foraging behavior
247
was not affected by relative food abundance of pairs of C. pyrenoidosa and C. sajao (Fig. 1 and 2).
248
Weakened D. magna caused by starvation should be less selectively on different food types
249
because it could decrease energy expenditure spending on food handling[24]. However, even when
250
the relative food abundance of pairs of C. pyrenoidosa was extremely low (7 Chlamydomonas : 1
251
Chlorella and 94 Chlamydomonas : 1 Chlorella in units of cell density and volume, respectively),
252
feeding selectively on C. pyrenoidosa was also the foraging strategy of D. magna (Fig. 2 B).
253
When the quality of food diet was viewed in a context of nutritional content (e.g. total carbon
254
content), we found that D. magna was also foraging optimally after starvation. Starved D. magna
255
grazed more efficiently on C. pyrenoidosa, a more valuable food in nutritional content, and
256
selected against low valuable C. sajao. When Daphnia was in starvation, additional energy
257
reserves in the body, e.g. lipid and carbohydrate, was utilized to maintain survival and
258
reproduction[3
259
contained more energy materials (e.g. total organic carbon) because such foraging behavior could
、22、23]
. In a weakened condition caused
The quality of food diet was usually defined as particle size and
、8、16]
. In the present work C. sajao with adequate size and easy digestibility was more
、11]
. In this condition the optimal foraging behavior was to select food diet that
-8-
260
increase the rate of energy storage in the body of Daphnia. Selection might favor this foraging
261
strategy, because it allowed a faster recover in metabolic process and reproduction of starved
262
animals when the starvation ceased, and this would eventually improve the competitive ability of
263
Daphnia in competing with other filter feeders, e.g. copepod and rotifer.
264
Some previous studies showed that starvation might lead to morphological changes in limbs and
、
265
increases in screen area, which would allow Daphnia to feed more efficient also on small algae[25
266
27]
267
feeding appendages of Daphnia. However, we think that this is not the case in the present work.
268
On one hand, Lampert observed that the filter-screen area did not change obviously in D.
269
magna[25]. On the other hand, if the filter-screen area increased when the D. magna was in
270
starvation in our experiments, an increasing trend of feeding efficiency would be observed in both
271
Chlamydomonas and Chlorella. However, we find inverse changing trends in the feeding
272
efficiency of D. magna on Chlamydomonas and Chlorella under starvation (Fig. 1 and 2), and
273
moreover, these changing trends were not influenced by relative algal abundance. Therefore, we
274
suggested that feeding selectivity on small sized Chlorella was the optimal foraging behavior of D.
275
magna under starvation conditions.
, implying that preference on small sized algae was possibly due to phenotypic plasticity of
276
The mechanisms used by Daphnia in feeding selectivity lied on two processes: gathering
277
information and collecting food particle, involving analysis of optical or chemical cues and
278
rejecting unwanted food particles, respectively[1
279
food based on the exudates of food algae, e.g. toxins of cyanobacteria[29], which could be regulated
280
by the pre-feeding conditions of Daphnia. Algae with adequate size and easy digestibility will be
281
treated as high quality foods when Daphnia was in satiation, while, algae with higher lipid or total
282
carbon content will be considered as high valuable diet when Daphnia was in starvation. The
283
second process was to reject low quality food. Unlike some copepods, foraging behavior of which
284
was always to select high quality food by ‘capture-taste-ingest’ process, Daphnia collected food
285
particles with filter combs[3
286
the carapace gape and filtering screens distance and clearance of accumulated low quality algae by
287
postabdomen seemed to be more feasible for Daphnia[16
288
Daphnia could be regulated by lengthening carapace gape and filtering screens distance to allow
289
small sized Chlorella passing through filtering apparatus. When Daphnia was in starvation,
290
selection on small sized Chlorella could be achieved by narrowing the carapace gape and filtering
291
screens distance to restrict the passage of the large and intermediate algae, and moreover
292
preventing the Chlorella slipping through feeding limbs.
、8、28]
. The first process was to discriminate optimal
、30]
. Therefore, rejection of unwanted food particles by modification of
、26]
. In conditions of satiation, selection of
293
Foraging behavior of filter zooplankton was always evaluated in the conditions that the animals
294
were fed with diets differed in food palatability. However, food nutritional content was also an
-9-
295
important criterion to evaluate food quality. Optimal foraging theory suggests that when animal is
296
in starvation, food diets valuable in nutritional content will be selected preferentially because this
297
foraging behavior can increase the rate of carbon storage in the body and allow a faster recover of
298
starved animal. Further foraging experiments should be designed to test this hypothesis with
299
different filter zooplankton taxa (e.g. copepod, rotifer), results of which may also be useful to
300
explain the possible mechanisms of community succession of different zooplankton taxa in varied
301
natural water bodies.
302
303
References
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