In recent years, because of human activities and the changes of natural environment, the severity, frequency of occurrence, and duration of hypoxia are increasing, resulting in high mortality of valuable living resources [
Previous researches had shown that juvenile
Marine invertebrates, including mussels (e.g.,
Hemocyanin is an important respiratory protein and a major plasmatic protein in crustaceans and plays an important role in binding and transporting oxygen and CO2 [
Most of previous studies focused on measuring the LC50 values in the special life stage and HC and THC in the condition of hypoxia, but there was very little information about the LC50 values in the whole life stages in the condition of hypoxia and the changes of HC and THC in the phase of reoxygenation. So, we performed studies to determine the LC50 values in whole life stages and investigated the changes of HC and THC in the condition of hypoxia and reoxygenation. These results can better understand the physiological mechanism of shrimp in the condition of hypoxia. Furthermore, it can provide fundamental data for shrimp farming and seedling.
Experiment conditions to determine the LC50 for dissolved oxygen of white shrimp
Life stage | Mean total length (mm) | Temperature (°C) | pH | Salinity ( |
---|---|---|---|---|
Zygote | — |
|
7.96 | 30 |
Nauplius | — |
|
7.98 | 30 |
Zoea I | — |
|
7.96 | 30 |
Zoea II | — |
|
7.98 | 31 |
Zoea III | — |
|
7.95 | 31 |
Mysis I | — |
|
7.96 | 30 |
Mysis II | — |
|
7.91 | 30 |
Mysis III | — |
|
7.91 | 30 |
Postlarvae I | — |
|
7.93 | 30 |
Postlarvae II | — |
|
7.89 | 30 |
Postlarvae III | — |
|
7.92 | 30 |
Postlarvae IV | — |
|
7.88 | 30 |
Postlarvae V | — |
|
7.88 | 30 |
Postlarvae VI | — |
|
7.82 | 30 |
Adult |
|
|
7.92 | 31 |
Adult |
|
|
7.91 | 31 |
Adult |
|
|
7.93 | 31 |
Adult |
|
|
7.92 | 31 |
Adult |
|
|
7.95 | 31 |
Adult |
|
|
7.96 | 31 |
Adult |
|
|
7.79 | 31 |
The first experiment was conducted to determine the LC50 values at different life stages of
The second experiment was conducted to determine the changes of HC and THC in the phase of hypoxia and reoxygenation. The average body lengths of shrimp were
The desired dissolved oxygen levels were established by bubbling nitrogen gas and air into the seawater, and the dissolved oxygen levels were monitored with a DO meter (HI 9146, HANNA) every half an hour. The pH and salinity values were measured by pH meter (HI 8424, HANNA) and salinity meter (RSH-28), respectively.
Hemolymph was collected randomly from each replicate at 0, 3, 6, 12, 18, and 24 h during the period of hypoxia and reoxygenation. Hemolymph was withdrawn individually from the cardiocoelom of shrimp with a 1.0 mL syringe filled with an equal volume of anticoagulant solution (30 mM trisodium citrate, 0.34 M sodium chloride, 10 mM EDTA, and 0.115 M glucose pH 7.55) and stored, respectively, in 1.5 mL Eppendorf centrifuge tubes. 30
Anticoagulant hemolymph was centrifuged at 800 g for 10 min under 4°C for HC assay. Then 100
All data were tackled using SPSS 19.0. Suppose that
The estimated LC50, LC90, and LC10 were shown in Table
Estimated 12 h LC50, 95% confidence intervals (CI), 90% lethal concentration, and 10% lethal concentration of the test white shrimp
Life stage | LC50 | CI | 90% lethal concentration | 10% lethal concentration |
---|---|---|---|---|
Zygote | 1.288 | 0.546 | 3.042 | |
Nauplius | 1.335 | 0.899–1.737 | 0.868 | 2.054 |
Zoea I | 1.404 | 1.257–1.525 | 1.057 | 1.866 |
Zoea II | 1.387 | 1.055–1.611 | 1.046 | 1.838 |
Zoea III | 1.722 | 1.569–1.856 | 1.230 | 2.413 |
Mysis I | 1.722 | 1.569–1.856 | 1.230 | 2.413 |
Mysis II | 1.762 | 1.600–1.910 | 1.178 | 2.637 |
Mysis III | 2.113 | 1.967–2.254 | 1.537 | 2.907 |
Postlarvae I | 1.490 | 1.340–1.632 | 0.951 | 2.335 |
Postlarvae II | 1.504 | 1.353–1.651 | 0.920 | 2.460 |
Postlarvae III | 1.349 | 1.197–1.502 | 0.709 | 2.564 |
Postlarvae IV | 1.074 | 0.954–1.197 | 0.607 | 1.900 |
Postlarvae V | 1.135 | 1.006–1.266 | 0.620 | 2.076 |
Postlarvae VI | 1.299 | 1.153–1.446 | 0.696 | 2.424 |
5 cm | 0.577 | 0.463–0.775 | 0.377 | 0.883 |
6 cm | 0.535 | 0.430–0.731 | 0.351 | 0.816 |
7.5 cm | 0.625 | 0.404–1.477 | 0.429 | 0.911 |
8.5 cm | 0.640 | 0.564–0.735 | 0.419 | 0.977 |
10 cm | 0.593 | 0.537–0.762 | 0.463 | 0.759 |
11.5 cm | 0.593 | 0.537–0.762 | 0.463 | 0.759 |
13.5 cm | 0.651 | 0.582–0.740 | 0.482 | 0.878 |
Figures
The change trend of HC in the condition of hypoxia and reoxygenation. The F3, F6, F12, F18, and F24 represented, respectively, the treatment time (3, 6, 12, 18, and 24 h) of reoxygenation (
The change of THC in the condition of hypoxia and reoxygenation. The F3, F6, F12, F18, and F24 represented, respectively, the treatment time (3, 6, 12, 18, and 24 h) of reoxygenation (
Figure
Figure
The estimated LC50 values are different at different life stages of white shrimp, and the larvae stage is more sensitive than adult stage. The range of LC50 in the phase of larvae (1.039 mg L−1) is larger than adult shrimp (0.116 mg L−1). The reasons may be that the growth and development of adult shrimp are more perfect and they can more efficiently resist environmental stresses.
Previous researches indicated that the 24 h LC50 values for 3- and 10-day-old mysids were 1.51 and 1.56 ppm, respectively; these are similar to the 12 h LC50 in this work. The 24 h and 48 h LC50 of pink shrimp were 1.36 and 1.46 mg L−1, respectively [
Mysis III is the most sensitive stage to hypoxia in whole life and the key phase in the process of shrimp culture. The LC50 values in the present study are little different from the values of published literature [
With the increasing experimental time, the change tendency of HC and THC in the present study was similar to published literature [
Shrimp only has innate immune system including hemocyte and diverse active factors existing in hemocyte or released to hemolymph from the hemocyte, so hemocyte plays an important role in immune defense. The results of the present and previous studies showed that THC, bacteriolytic activity, antibacterial activity, phagocytic activity, and phenoloxidase activity decreased significantly and the sensibility to pathogens increased in the condition of hypoxia [
Yuhu Li is the first coauthor.
The authors declare that there is no conflict of interests regarding the publication of this paper.
This work was supported by the China Postdoctoral Science Foundation Funded Project (2013M530332), the Specialized Research Fund for the Midwest Programme of Hainan University (ZXBJH-XK002), the Specialized Research Fund for the Doctoral Programme of Higher Education of China (20114601120001), and the Hainan Province Special Fund of the Integration of Industrialization, Teaching and Research (CXY20130054).