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© by PSP Volume 26 – No. 12/2017 pages 7575-7579 Fresenius Environmental Bulletin
7575
TO WHAT EXTENT DOES TEMPERATURE AFFECT SEX
RATIO IN RED CHERRY SHRIMP, NEOCARIDINA
DAVIDI? THE SCENARIO GLOBAL WARMING TO
OFFSPRING SEX RATIO
Ramazan Serezli1,*, Mehmet Sina Atalar1, Sevim Hamzacebi1, Ilker Zeki Kurtoglu2, Ilhan Yandi3
1Izmir Katip Celebi University, Faculty of Fisheries and Aquaculture, 35620, Izmir, Turkey
2Recep Tayyip Erdogan University, Faculty of Fisheries and Aquaculture, 53100, Rize, Turkey
3Recep Tayyip Erdogan University, Maritime Faculty 53100, Rize, Turkey
ABSTRACT
An invasive freshwater shrimp, Red Cherry
Shrimp (Decapoda: Caridea: Atyidae), is naturally
distributed in fresh water habitats of Asia. This for-
age species has an important role in aquatic ecosys-
tems by transferring planktonic production into
higher trophic levels mainly including fish and
aquatic animals. However, temperature strongly
affects sex ratio and in turn offspring quantity. In or-
der to determine the effect of temperature on incuba-
tion period, egg yield, offspring sex ratio as well as
survival, a comprehensive experiment was con-
ducted at three temperatures (20, 23 and 26ºC). Sig-
nificant differences among temperatures for hatch-
ing period were an expected result. Higher survival
and more eggs were achieved at 26ºC comparing the
lower experimental temperatures. The female/male
ratio, which was 80% at 20°C and approximately
50% at 23ºC, drastically dropped to 18% at 26°C.
This ratio may drop to 0% at higher temperatures,
which are tolerance limits for Red Cherry Shrimp.
Therefore, in sex-dependent selective breeding, the
temperature should be taken into consideration. Con-
sequently, as temperature increases the sex ratio of
the offspring increases in favour of the male. The
continuation of global warming and rising above
26°C may be an important source of stress on the
natural sustainability of Red Cherry Shrimp stocks.
KEYWORDS:
Neocaridina, heterapoda, extinction, global warming, sex
ratio
INTRODUCTION
Meiofauna including shrimps has an important
ecological role in aquatic ecosystems by transferring
planktonic production into higher trophic levels [1,
2]. In addition, shrimps have a potential economic
importance both in aquaculture and in aquarium sec-
tor as an ornamental species [3].
The Atyid shrimp Neocaridina davidi (Bouvier
1904), popularly known as “Red Cherry Shrimp
(RCS)”, is a small size freshwater shrimp distributed
throughout Taiwan, Vietnam, Korea, Japan, Russia
and China [2, 4, 5, 6] and it is able to tolerate much
colder temperature regimes [7].
RCS is also a popular species for fresh water
aquariums in Turkey [8]. It is very adaptable and
easy to culture but the sex ratio is an important factor
to consider because of a certain ratio, as in other
aquatic animals, is necessary for the continuity of the
generation [9].
Sex-determining mechanisms are broadly di-
vided into two major categories: genetic and envi-
ronmental [10]. The most important environmental
sex determining factors are temperature and photo-
period. These environmental parameters stimulate
and maintain gametogenesis and other reproductive
processes in freshwater invertebrates [1].
Aquatic animals adapt to the conditions they
are living in. If they cannot achieve this, growth dis-
turbances, physiological disorders, and stopping of
the ureamia, as well as disorders of egg development
and embryo development, are antagonistic.
According to climate forecasting models, it is
estimated the global mean temperature will increase
3 degree by 2050 and 6 degree by 2100 [11], this
may lead to major changes in biodiversity. In this
process, the tolerance to upper temperature limits of
aquatic animals will be determinant for their sur-
vival. In this study, female/male ratios, survival rates
and embryonic development times of the N. davidi
species, which is an important species for aquatic en-
vironment, were determined at three different (20,
23, 26°C) temperatures.
MATERIALS AND METHODS
Red cherry shrimp (N. davidi), about 1.5-2.0
cm, were supplied from local producers. The
shrimps were selected from 1.5-2.0 cm adult individ-
uals. They were evenly distributed to nine glass
aquaria. Java moss (Vesicularia dubiana) was added
in equal amounts to aquariums which have 5 cm of
basalt sand on the bottom. The study was conducted
© by PSP Volume 26 – No. 12/2017 pages 7575-7579 Fresenius Environmental Bulletin
7576
as three replicates for each experimental tempera-
ture. Water temperatures were provided by aquarium
heaters (Atman-100 W) with ±0.5°C precision. Fe-
males with eggs in the dorsal were taken into 0.8 liter
containers individually after mating and observed
twice a day. After hatching, females are not paired
again. The dead larvae were immediately removed
and noted.
In the study, filtered and UV-treated tap water
was used and half of the rearing water was ex-
changed per week. Brood shrimp and their larvae
were fed ad libitum with commercial shrimp feed
(containing 40% crude protein) twice a day (09:00
and 18:00). Females were removed after the larvae
hatched separately, and number of larvae produced
by each female was recorded. Sex differentiation
was determined approximately after 3 months, males
identified as they are smaller and there are no
longitudinal stripe on dorsal females identified as
they have the formation of curves in the bellies, they
are bigger and have longitudinal stripe on dorsal.
The pH was 7.5-8.0, the conductivity was 200-400
μS, the TDS (total dissolved matter) values were in
the range of 100-200 ppm and oxygen >4 ppm.
Lighting was provided for 12 hours by using auto-
matic timer.
Sex determination of the Red Cherry Shrimp is
quite obvious. Females are larger than the males,
have a much darker red coloration and also have a
curved underbelly. Male shrimp have very little red
coloration and has a straight lateral line with no
curved shape.
Statistical Analysis. All statistical analysis
was performed using SigmaPlot (SigmaPlot 14.0,
Systat Software Inc., San Jose, CA, USA). Differ-
ences were deemed to be significant at P<0.05 and
P<0.01. To assess normality of distributions a Kol-
mogorov-Smirnov test was used and homogeneity of
variances was tested using F test. The data without
equal variance and/or normal distribution was tested
using Kruskal-Wallis whereas data with normal dis-
tribution and equal variance was subjected to a one-
way ANOVA. The significance of the difference be-
tween means was tested using Holm-Sidak and
Tukey All Pairwise Multiple Comparison Proce-
dures. Values are expressed as mean ± mean’s stand-
ard error. The chi-square test (w2) was used to deter-
mine whether the observed sex ratio differed from
the expected 1:1.
RESULTS
Red cherry shrimps were kept for 180 days at
three different temperatures. Egg development and
larval output were monitored at 20, 23 and 26°C dur-
ing the experiment. After egg formation at the dorsal
(also called as saddle), once shell changes and then
mating was observed. It was decided that the eggs
were fertilized by the fact that the eggs on the back
of the mating females passed through the abdomen,
was visually inspected. After three months, the sex
of the offspring can be clearly determined. Thirty
different offspring from each experimental group
were taken at the same temperature. Duration of egg
incubation, the number of offspring, the percentage
of female and male of offspring and survival rates
were determined.
The experiment conducted at three different
temperatures, it was observed that as the temperature
dropped, the number of eggs decreased. At 20, 23,
and 26°C, the fecundity are; 24.21±0.67,
32.31±0.70, and 34.44±0.60, respectively. It has
been seen that female produced a maximum of 45
eggs (Fig. 1).
FIGURE 1
The number of eggs produced by adult N. davidi
at 20, 23 and 26ºC. Vertical bars indicate stand-
ard error of the mean. Significant difference at
20 ºC (**P <0.01).
FIGURE 2
The hatching duration of N. davidi reared at 20,
23 and 26ºC. Kruskal-Wallis One Way Analysis
of Variance and Tukey All Pairwise Multiple
Comparison procedure. Vertical bars indicate
standard error of the mean. Different letters in-
dicate significant difference (P < 0.01).
Egg development is accelerated with increasing
temperature, increasing temperature decreases the
output time of the eggs. Eggs were hatched at
32.47±0.23 days at 20°C, 29.39±0.20 days at 23°C,
© by PSP Volume 26 – No. 12/2017 pages 7575-7579 Fresenius Environmental Bulletin
7577
28.22±0.16 days at 26°C. The incubation period was
determined to be between 25 and 37 days, depending
on the water temperature (Fig. 2).
In three experimental groups (20, 23, 26°C), the
ratios of the females were; 82.76±0.37, 52.15±0.41,
and 20.73±0.33, respectively (Fig. 3).
FIGURE 3
The sex ratio (female/male) of N. davidi reared at
20, 23 and 26ºC. One Way Analysis of Variance
and Holm-Sidak All Pairwise Multiple Compari-
son Procedure. Error bars indicate ±SD. Differ-
ent letters indicate significant difference (P <
0.05).
Survival rates were not related to temperature.
The survival rates in the three groups (20, 23, 26°C)
were; 86.15±0.81, 89.78±0.46, 90.13±0.30 respec-
tively (Fig. 4).
FIGURE 4
The mean survival of N. davidi reared at 20, 23
and 26ºC. Kruskal-Wallis One Way Analysis of
Variance and Tukey All Pairwise Multiple Com-
parison procedure. Vertical bars indicate stand-
ard error of the mean. Significant difference at
20ºC (**P <0.01).
It is also an important finding that cherry
shrimp eggs are fertilized after each pairing, not
paired females throw out the not fertilized eggs, and
that they do not carry eggs from the dorsal (saddle)
part to the abdomen.
DISCUSSION
Temperature and photoperiod are the two most
important factors affecting gametogenesis. The tem-
perature is also effective in the formation of gametes
sex. Studies of different species on the effect of tem-
perature on gender formation exist [12, 13, 14]. In
these studies, the sex ratio changes depending on the
temperature and the effects of different temperatures
on the female/male ratio were investigated. How-
ever, there is very little information available on red
cherry shrimp N. davidi. Tropea et al. [5] determined
growth, development and sex ratios at three different
temperatures (24, 28, 32°C) in their study of red
cherry shrimp. As the temperature increases, the
number of males increases similarly to our study.
However, 28 and 32ºC are risky for the growth and
development of this type. Weber and Traunspurger
[2] conducted experiments with N. davidi at 19-
20ºC. According to our observation, it is appropriate
to grow these shrimps in the range of 20-23ºC.
Many researchers have studied the effect of
temperature on fish sex ratio [12-15]. In these stud-
ies, it is reported that the decrease in the male ratio
is generally caused by the increase in temperature.
Luckenbach et al. [13], conducted a study on
southern flounder (Paralichthys lethostigma) and
found that the female ratio was low (18°C) and high
(28°C) temperatures, so temperature affects the sex
ratio.
When it comes to cultivation, sometimes fe-
male and sometimes male raising may be required.
For example, male guppies are demanding more be-
cause they have attractive colors. On the other hand,
females are preferred for fish breeding, while males
are preferred for tilapia breeding [14].
External differentiation between female and
male takes place during the second month after post
larval transformation as mentioned before [16].
Compos-Ramos et al. [16] studied the Li-
topenaeus vannamei and found that the female/male
ratio did not change and was it was 50% at 18 and
32°C.
It was determined the embryonic development
of N. denticulata sinensis that lasted for 15 days at
27°C water temperature, and each brood produced
21-51 larvae, large brood produced more larvae, and
larvae became an adult after 75 days [3]. We have
determined that the duration of the larvae output is
between 26 and 33 days, depending on the tempera-
ture. This difference may be due to species variation
or from the following phases. In our study, we cal-
culate time length between eggs transferred to fe-
males abdominal to grow as larvae. The female/male
ratio is important to keep the natural balance and
generation. Nowadays, when the global warming
problem is on the rise, it is necessary to continue to
study how this affects the generation of the living
things. As the female/male ratios of natural popula-
© by PSP Volume 26 – No. 12/2017 pages 7575-7579 Fresenius Environmental Bulletin
7578
tions are affected by temperature changes [17], fu-
ture generations can be affected by extinction or ge-
netic disorders. In this study, it was determined that
the female ratio at temperatures of below 23°C and
the male ratio at temperatures between 23 and 26°C
increase. Increase or decrease of temperature affects
female/male ratio in N. davidi.
Sex determination mechanisms produce the sex
ratio, a key demographic parameter crucial for pop-
ulation viability [18]. As a conclusion, red cherry
shrimp (N. davidi) stock f/m ratio rate dramatically
changed in favour of female subjects, and survival
rate in favour of female subjects with increasing wa-
ter temperature from 23 to 26°C. These findings pro-
vide an important clue to the sustainability of natural
ecosystems as well as a result for aquarium hobby-
ists. The radical increase in global warming will also
affect the aquatic ecosystem mean, minimum and
maximum water temperature values. Similar studies
on ecosystem indicator species will allow valuable
information about the sustainability of these species.
By correlating these data with global warming, an
opportunity will be provided for future projections
on ecosystem sustainability.
ACKNOWLEDGEMENTS
This study was supported by the Scientific Re-
search Fundation of Izmir Katip Celebi University,
Project Number: 2014-TYL-SUUF-0023.
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Received: 17.08.2017
Accepted: 18.09.2017
CORRESPONDING AUTHOR
Ramazan Serezli
Izmir Katip Celebi University, Faculty of Fisheries,
Department of Aquaculture, 35620, Cigli, Izmir,
Turkey.
e-mail: rserezli@gmail.com