全 文 ：Effect of Different Proportions ofWolffia on
Growth of Procambarus clarkia in Two
Community Scales
Pengfei JI1, Xingyun YAN2, Cheng HUANG1, Jianqing TANG3*
1. School of Life Science, Nanjing University, Nanjing 210093, China;
2. Nanjing University Jinling College, Nanjing 210089, China;
3. Freshwater Fisheries Research Institute of Jiangsu Province, Nanjing 210017, China
Supported by the Special Fund Project for the Scientific Research of the Public Welfare
Industry (201003070); the National Natural Science Foundation of China (NSFC
J0730641).
*Corresponding author. E-mail: jstjq@163.com
Received: September 6, 2011 Accepted: May 21, 2012A
Agricultural Science & Technology, 2012, 13(7): 1583-1586
Copyright訫 2012, Information Institute of HAAS. All rights reserved Animal Science
Abstract [Objective] This study aimed to examine the effect of different proportions
of Wolffia on the growth of Procambarus clarkia in 2 kinds of community scales.
[Method] Six proportions of baits mixed by watermeal and commercial feed (0, 20%,
40%, 60%, 80%, and 100%) were designed to feed the Procambarus clarkia juve-
niles in 2 community scales to research the growth situation of the crayfish in dif-
ferent mixed baits. The growth differences between the minimal community and the
larger community of crayfish in the same proportion of Wolffia were compared. [Re-
sult] The growth situations of crayfish in the 2 community scales at different propor-
tions of watermeal were as follows: the body length was the longest in 60% water-
meal group, and shortest in the pure watermeal group; the regularity was the best in
the 20% watermeal group; no matter the minimal community or the larger communi-
ty, there was no significant difference in the survival rate between different water-
meal proportions. The growth situations of crayfish in the 2 community scales at
specific proportion of watermeal were: the average body length of the minimal com-
munity was significantly greater than the larger community, and the survival rate also
greater than the latter one, but the difference was not significant. [Conclusion] Con-
sidering all kinds of index such as growth, survival rate, regularity, the appropriate
proportion of the baits mixed by watermeal and commercial feed is 40% to 60%; big
community scale has significant inhibition on growth of crayfish, thus, there should
be barriers when cultivating Procambarus clarkia juvenile.
Key words Wolffia; Minimal community; Larger community; Mixed feed; Optimum
proportion
W atermeal, also known asAsian water meal, a perenni-al floating plant, is a member
of family Lemna minor[1]. It is in round
shape with a diameter of no more than
1 cm. Watermeal is the smallest flow-
ering plant in the world, and it is also
the plant with the smallest flowers and
fruits in the world. Krachang et al. first
proposed to use watermeal as a cheap
source of protein, and investigated the
relevant circumstances of watermeal
production[2]. The study of Skillicorn et
al. has shown that the watermeal con-
tains high quality protein, which has
the similar characteristics to animal
protein and soy protein[3]. Rusoff et al.
found that watermeal is an excellent
source of protein and amino acid, and
worked out a way to extract and purity
the protein amino acid in watermeal,
through which they determined the
amino acid composition [4], discovering
that watermeal has extremely high
content of crude protein (29.9% -
36.5% DM)[4-5]. The study of Masanori
et al. suggests that planting watermeal
can remove the eutrophication from
water body, and the cultivation of wa-
termeal can provide a lot of starch [6].
The research of Gastanares et al. indi-
cates that watermeal can partially re-
place the legumes in the feed ratio,
which can reduce the use of legumes
in the feed [ 7 ] . In this paper , we dis -
cussed the possibility of partially re-
placing the Cargill refined crab feed
with watermeal in crayfish cultivation.
Materials and Methods
Materials
The brooding crayfishes were se-
lected out from the Manjianghong Red
Swamp Crayfish Cultivation Base in
Xuyi County, Jiangsu Province; wa-
termeal was collected from the suburb
of Nanjing City, and preserved in the
refrigerator; commercial feed: Cargill
refined crab feed (SC/T 1078-2004).
Experimental design
Several healthy brooding cray-
fishes were selected to cultivate by us-
ing the mixed feed for 1 week. One
week later, 720 post larveas which had
just separated from the mother bodies
were randomly selected to measure
their body weight and body length to
ensure that there was no significant dif-
ference in the body weights between
different groups. Six proportions of
baits mixed by watermeal and com-
mercial feed (0, 20%, 40%, 60%, 80%,
and 100%) were designed to feed the
crayfishes.
Minimal community: 60 small
lunch boxes (size of 33.2 cm2, water
depth of 3-4 cm) were selected with 2
juvenile crayfishes in each box; differ-
ent proportions of feed were added in
the boxes to feed the crayfishes with
10 replicates for each treatment.
The larger community: 24 water
tanks (area of 0.062 m2, water deep of
3-4 cm) were selected with 25 juvenile
DOI:10.16175/j.cnki.1009-4229.2012.07.047
Agricultural Science & Technology
Agricultural Science & Technology Vol.13, No.7, 2012
2012
Table 4 The results of significance in grouping test
20% 40% 60% 80% 100%
0 0.004** 0.854 0.755 0. 015* 0.000***
20% 0.005** 0.001** 0.643 0.000***
40% 0.605 0.020* 0.000***
60% 0.005** 0.000***
80% 0.000***
*, P < 0.05；***, P < 0.01；***, P < 0.001.
Table 3 Descriptive data of the effects of different proportion of watermeal on the growth of
crayfishes in minimal community
Watermeal
content∥%
Survival
number
Average body
length∥mm
Minimal
value∥mm
Maximal
value∥mm Range
Variation
coefficient
0 74 12.58±1.71 8.59 16.33 7.74 0.137
20 89 11.79±1.48 7.60 15.73 8.13 0.126
40 85 12.53±1.90 8.99 18.38 9.39 0.152
60 82 12.67±1.81 7.87 17.60 9.73 0.143
80 83 11.91±1.81 8.05 16.03 7.98 0.152
100 81 10.33±1.54 7.31 15.62 8.31 0.149
Table 2 The results of significance in grouping test
20% 40% 60% 80% 100%
0 0.531 0.866 0.197 0.051* 0.097
20% 0.419 0.497 0.009** 0.020*
40% 0.138 0.070 0.130
60% 0.001** 0.003**
80% 0.763
*, P < 0.05; **, P < 0.01.
Table 1 Descriptive data of the effects of different proportion of watermeal on the growth of
crayfishes in minimal community
Watermeal
content∥%
Survival
number
Average body
length∥mm
Minimal
value∥mm
Maximal
value∥mm Range
Variation
coefficient
0 17 14.70±1.88 10.92 17.56 6.65 0.128
20 19 15.02±0.85 14.05 17.43 3.39 0.057
40 18 14.62±1.26 11.63 17.50 5.87 0.100
60 20 15.34±1.22 13.35 17.35 4.00 0.079
80 18 13.71±1.60 10.37 16.45 6.08 0.117
100 18 13.85±1.77 10.00 17.27 7.27 0.128
crayfishes in each tank; different pro-
portions of feed were added in the
tanks to feed the crayfishes with 4
replicates for each treatment.
In order to prevent the juvenile
crayfishes from fighting, butterfly-
shaped shelter was put in the aquari-
um for the crayfishes to hide and
rest. The test water was aerated tap
water. The water change and feed
delivery were once in 2 d. The water
temperature was room temperature
at 15 -20 ℃ . The experiment lasted
35 days, and the survival number
calculation and body length mea-
surement were conducted at the end
of the experiment.
Data statistics
The data was analyzed by
SPSS18.0. The data was expressed
as the mean ± standard error (SEM).
Single factor analysis of variance and
Post Hoc test (LSD method) were
used to compare the statistical differ-
ences between the experimental
groups, and P < 0.05 was considered
as significant difference.
Results and Analysis
Minimal community test
As shown in Table 1, when the
watermeal pr oportion reached 60% ,
the average body length of crayfish
was the longest; from the perspective
of coefficient of variation, it was the
lowest when the watermeal proportion
was 20%, followed by 60% group, indi-
cating that the growth of crayfishes in
these 2 groups was the most regular.
The significance test for the body
length variation showed that F = 3.461,
P =0.006 <0.01. Therefore, six groups
of different watermeal proportions
showed significant differentiation in
feeding crayfishes, and there were
significant differences between the
experimental groups. The grouping
test results were shown in Table 2.
The test results showed that there was
no significant difference between the
experimental groups with the water-
meal proportions of 0% , 20% , 40%
and 60%; when the watermeal propor-
tions reached 80% or 100% , both
groups showed significant differences
with the 60% group.
Larger community test
As shown in Table 3, in the larger
community, the average body length of
crayfish was still the longest when the
watermeal proportion reached 60% ;
from the perspective of variation coeffi-
cient, it was the lowest when the wa-
termeal proportion was 20%, when the
growth of crayfish was the most regu-
lar, followed by the 0% group. The sig-
nificant test on the body length varia-
tion showed F = 21.431, P = 0.000 <
0.001. Therefore, six groups of differ-
ent watermeal proportions showed
significant differentiation in feeding
crayfishes, and there were significant
differences between the experimental
groups. The grouping test results were
shown in Table 4. As shown in Table
4, there was no significant difference
between the experimental groups with
the watermeal proportions of 0, 40% ,
60%; the experimental group with the
watermeal proportion of 80% showed
extremely significant difference with
the groups of less than 60%; the group
with 100% watermeal showed ex-
tremely significant difference with the
groups with watermeal proportions of
less than 80% ; in addition, the 20%
group showed extremely significant
difference with the groups of 0, 40% ,
60%, 100%.
Comparison between the minimal
community and the larger commu-
nity
As shown in Table 5, in each cor-
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Agricultural Science & Technology
Vol.13, No.7, 2012 Agricultural Science & Technology
2012
Table 5 The comparisons on the growth of crayfishes between the larger community and
the minimal community
Watermeal
content//%
Larger community Minimal community
Significance
(Sig.)Number of
samples
Average body
length
Number of
samples
Average body
length
0 74 12.58 17 14.70 0.000***
20 89 11.79 19 15.02 0.000***
40 85 12.53 18 14.62 0.000***
60 82 12.67 20 15.34 0.000***
80 83 11.91 18 13.71 0.000***
100 81 10.33 18 13.86 0.000***
*, P < 0.05；**, P < 0.01；***, P < 0.001.
responding watermeal group, the body
lengths of crayfishes in the minimal
community were significantly longer
than those in the larger community. In
addition, the variation coefficient test
between communities showed that as
for the regularity, the minimal commu-
nity showed better regularity than the
larger community, and the difference
reached significant level.
Discussion
The chemical composition analy-
sis of watermeal shows that its crude
fiber content is moderate, around
9.02% -11.06% , in line with the re-
quirements of the feed for fish and
shrimp[8]. Chareonteprasit et al. [8] tried
to replace traditional soy with water-
meal to feed tilapia, found that the ef-
fect is the best when the watermeal ac-
count for 15% of the total feed, and
there is statistical significance between
total production and survival variation
trend; but if the watermeal content ex-
ceeds 15%, the production reduced. In
the 2 communities of this experiment,
increasing watermeal content has sig-
nificant effect on promoting the growth
of Procambarus clarkia, and all the ef-
fects are the best with the watermeal
content of 60%. However, in the mini-
mal community, there is no significant
difference between the experimental
groups with the watermeal contents of
0% , 20% , 40% , 60% ; in the larger
community, there is no significant dif-
ference between the 60% and 0% ,
40% groups. Therefore, no matter for
minimal community or larger communi-
ty, the watermeal can replace the ex-
pensive commercial feed to feed the
crayfish, and the highest mixed pro-
portion can reach up to 60%.
In the 2 kinds of community
scales, when the watermeal proportion
reaches 80% , it significantly inhibits
the growth of crayfish, and the body
length of crayfish is not only signifi-
cantly shorter than the 60% group, but
also shorter than the 0% group. Poo-
ponpan et al. evaluated the nutritional
value of watermeal in feeding the
chicken for table purpose, found that it
has good effect on the replacement,
but pointed out that the lack of certain
essential amino acids and high content
of crude fiber are important limiting fac-
tors [9]. There is also similar phenom-
enon in algae applications that if the
fiber content of the algae is too high
(over 12%), it will reduce the contents
of useful nutrients, resulting in low food
conversion efficiency, ultimately, lead-
ing to slow growth and other issues [10].
60% is a suitable proportion of water-
meal in the Cargill refined crab feed,
and for other feed brands, further ex-
perimental analysis is required to de-
termine the suitable proportion.
Procambarus clarkia is an ex-
tremely aggressive species [11-12], and
there is always intensive intraspecific
competition for shelter and fool in the
cultivation [13]. When cultivate in large
community, the intensive internal ex-
pense would slow down the speed of
growth and development, while small-
scale cultivation can reduce the strug-
gle intensity to the minimum, providing
sufficient food and space for the
growth of crayfish. It is also the reason
why the body lengths of crayfishes cul-
tivated in minimal community are
longer than those in larger community
scale.
In this experiment, although the
20% group is significantly greater than
the 100% group, it also significantly
smaller than the 0, 40%, 60% groups.
Thus, compared with the pure feed
group, the 20% watermeal group
seems more unfavorable for the
growth of crayfish; if takes the number
of survival crayfish into account, that
is, using the relative total biomass (the
total number of survival crayfish* the
body length of crayfish) to measure,
then the 20% group is higher than the
pure feed group, which is due to the
asymmetry of density that the density
of 20% group is much greater than the
pure feed group, and the individual
fighting intensity is also much larger
than the pure feed group, thus the con-
sumption from the intraspecific strug-
gle inhibit the growth of crayfish, which
explains why the body lengths of cray-
fishes in the 20% group are shorter
than the pure feed group.
Regularity is very important for
large-scale production, and the coeffi-
cient of variation is an effective param-
eter to reflect the regularity [14]. In our
experiment, among the groups in the
minimal community, the variation coef-
ficient is the minimum when the water-
meal proportion is 20% , followed by
the 60% group, indicating that the
growth of these two groups is the most
regular; among the groups in the larger
community, the variation coefficient is
the minimum when the watermeal pro-
portion is 20%, showing the most reg-
ular growth, followed by the pure feed
group. The test for variation coefficient
shows that the minimal community is
more regular than the larger commu-
nity, and the difference between the 2
reaches significant level.
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About Agricultural Science & Technology
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不同芜萍饵料组分对两种社群规模的螯虾生长影响
季鹏飞 1，严幸云 2，黄 成 1，唐建清 3* （1.南京大学生命科学学院，江苏南京 210093；2.南京大学金陵学院，江苏南京 210089；3.江苏省淡水水产研
究所，江苏南京 210017）
摘 要 [目的]研究不同比例的芜萍饵料组分对 2种社群规模下螯虾生长的影响。[方法]试验设置了芜萍与商品饲料 6种比例的混合饵料（0、
20%、40%、60%、80%、100%）分别饲喂最小社群与较大社群下的克氏原螯虾幼体，以研究不同芜萍组分下螯虾的生长状况，并对相同芜萍组分下
最小社群和较大社群螯虾的生长差异。[结果] 2种社群规模的不同芜萍组分螯虾生长结果为：体长最大的均为 60%芜萍组，最小的均为纯芜萍
组；整齐性最好的均为 20%芜萍组；无论是最小社群还是较大社群，各自不同芜萍组分的存活率差异均不显著。相同芜萍组分下 2个社群间的同
期比较结果为：最小社群的平均体长显著大于较大社群，而存活率前者也大于后者，但差异并未达到显著水平。[结论]综合生长、存活及整齐等
指标，认为芜萍与商品饲料合适的混合比例为 40%~60%；社群规模较大对鳌虾生长有显著抑制作用，因此应在克氏原螯虾苗种培养环境中设
置隔离障碍。
关键词 芜萍；最小社群；较大社群；混合饲料；最优配比
基金项目 国家公益性行业科研专项（201003070）；国家自然科学基金委项目（NSFC J0730641）。
作者简介 季鹏飞 (1989-)，男，江苏泰兴人，硕士研究生，研究方向：水生生物学，E-mail:jpf115220@yahoo.com.cn。*通讯作者，研究员，从事水产
科学方面的研究，E-mail: jstjq@163.com。
收稿日期 2011-09-06 修回日期 2012-05-21
*******************************************************
Responsible editor: Na LI Responsible proofreader: Xiaoyan WU
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