Volume 75, 2023
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ItemThe effect of dietary docosahexaenoic acid (DHA; 22:6n-3) on photoreceptor abundance, rhodopsin expression and growth in developing gilthead sea bream (Sparus aurata) larvae( 2023)This study determined the effect of prey DHA on larval gilthead sea bream (GSB; Sparus aurata) photoreceptor abundance, rhodopsin expression, and growth performance. It was carried out in a twenty-eight 400 l conical tank system that was stocked with 100 viable GSB eggs/l/tank. This allowed the testing of 4 levels of rotifer DHA; 0.99 (Low; L), 1.9 (Intermediate low; I-L), 3.2 (Intermediate high; I-H) and 12.1(High; H) mg DHA/g DW rotifer, which were fed (10 rotifers/ml) to 3-16 DPH larvae. These rotifer diets continued to be offered to 17-34 DPH fish, although these larvae predominantly fed on 4 DHA enriched Artemia nauplii treatments that were offered at a concentration from 0.1 nauplii/ml to 4 nauplii/ml, depending on larval age. This resulted in 4 DHA rotifer-Artemia ranges: 0.99-0.0 (L), 1.9-2.6 (I-L), 3.2-7.2 (I-H), and 12.1-11.77 (H) mg DHA/g DW. The 4 DHA treatments and ranges were tested in replicates of 7 conical tanks per treatment. Increasing rotifer DHA significantly (P<0.0001) improved TL, in an exponential manner, throughout larval rearing. DW in 34 DPH larvae was markedly (P<0.05) enhanced with dietary DHA inclusion in the rotifers and Artemia. There was a significant (P < 0.005) prey DHA dose dependent range effect on the abundance of photoreceptor cells in the retina of 34 DPH larvae. The gene expression of rhodopsin in GSB larvae was significantly (P<0.05) upregulated with dietary DHA dose range and larval age (P<0.0001). This study established a link between dietary DHA level with photoreceptor abundance and rhodopsin expression, which led to improved vision, prey acquisition, and growth in developing GSB larvae.
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ItemMorphological characteristics and genetic diversity of Terapon jarbua (Forrskäl, 1775) in Central, Vietnam( 2023)Many environmental factors affect the morphology of migratory fish species, such as salinity, water flow rate, and temperature. However, studies on changes in fish morphology under environmental variations from salt water to brackish water are still limited in many fish species, especially in *Terapon jarbua*. This study aims to investigate the differences in the morphological parameters of *T. jarbua* between the coastal sea (seawater) and lagoon (brackish water); and between male and female fish based on a landmark morphological approach. Additionally, the genetic diversity of *T. jarbua* populations in Central Vietnam was elucidated using the mitochondrial DNA cytochrome oxidase subunit I (mtDNA COI) sequence as a molecular marker. The analytical results indicated no sexual dimorphism in the *T. jarbua* population, yet conformational differences exist between the two studied aquatic species. The analysis of 42 mtDNA COI sequences collected from Central Vietnam identified 13 haplotypes with medium genetic diversity and low genetic differentiation between the Tam Giang lagoon and Thua Thien Hue coastal (Fst = 0.028) and not significant (p = 0.126). Most haplotypes obtained are present in reference populations, indicating a high genetic exchange between populations. We proposed that the *T. jarbua* population in Central Vietnam has a stable connection with neighboring populations (China, Taiwan, Philippines, Indonesia, Malaysia, Bangladesh, India, and Pakistan).
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ItemTrematodes obtained from snails in giant gourami ponds supplied by well water in Tien Giang province, Vietnam( 2023)A study on trematode obtained from freshwater snails in 30 grow-out giant gourami ponds supplied by well water was conducted in Chau Thanh district, Tien Giang province, Vietnam. The snails were sampled in the flooding season (October 2020), the intermediary season (January 2021) and the non-flooding season (April 2021). Eight snail species belonging to 8 genera, 4 families were found including Sermyla tornatella (48.6%), Sinotaia lithophaga (19.3%), Filopaludina sumatrensis (15.4%), Melanoides tuberculata (6.4%), Pomacea sp. (4.7%), Bithynia siamensis (4.2%), Thiara scabra (0.8%) and Tarebia granifera (0.6%). Cercariae were recovered from only two snail species of Melanoides tuberculata with Xiphidio cercariae and Furcocercous cercariae with a prevalence of 7.4%, and Bithynia siamensis with Xiphidio cercariae and Pleurolophocercous cercariae with the infection rate of 6.9%. The trematodes were found in 8 ponds (26.7%), 7 ponds (23.3%), and 3 ponds (10.0%) in the intermediary season, the non-flooding season, and the flooding season, respectively (P>0.05). More research on the epidemiology of trematodes in snails in fishponds should be done to contribute to food safety and sustainable aquaculture.
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ItemEffects of water temperature on swimming performance of Siniperca knerii Garman under the Yuanshui River cascade development( 2023)We examined the swimming parameters and oxygen consumption rate at four temperature levels (15，20，25 and 30°C) of Siniperca knerii Garman (11.81 ±2.21 cm, 26.4 ± 6.28g) from Yuanshui River for 30 days to analyze the ecological adaptability of the typical fish and the conservation of fishery resources from the Dongting Lake water system. Their relationship was also analyzed, and the results showed an approximately linear increasing trend of the fish's critical swimming speed and preferred swimming speed with the change of temperature (P<0.05). In contrast, the induction velocity of fish decreased with the increase in water temperature. The relative induction velocities of the fish at four temperatures were (1.16±0.07), (0.94±0.06), (0.86±0.07), and (0.70±0.09) BL/s (Body Length/s). The preferred swimming speed was (1.86±0.04), (2.23±0.35), (2.65±0.28), and (2.74±0.33) BL/s. The relative critical speed was (2.58 ±0.32), (3.31±0.41), (4.31±0.52), and (5.22±0.48) BL/s. According to oxygen consumption rate at different temperatures, four nonlinear function models of the relationship between oxygen consumption rate of water temperature and swimming speed behavior parameters were obtained by nonlinear fitting. The model proved that the oxygen consumption rate, tail beating frequency, and respiratory rate increased with the increase in swimming speed. The higher the temperature, the more significant the changes were. The results showed that water temperature significantly affected the swimming characteristics of juvenile Siniperca knerii Garman. The changes were due to physiological and biochemical regulation with temperature and environmental changes. This experiment provided essential data support for the adaptive mechanism of sports physiology and ecology of typical fishes in the Yuanshui River.
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ItemAnalysis of morphological differences among different populations of golden pompano (Trachinotus ovatus)( 2023)To explore the external morphological differences of golden pompano in different geographical populations, eight quantitative traits of 210 samples from seven golden pompano populations were measured. Multivariate statistical methods, such as principal component analysis, discriminant analysis, cluster analysis, and One-way ANOVA, were used to compare morphological differences among the populations. Principal component analysis extracted the top five principal components with a cumulative contribution rate of 85.79%, of which the first three principal components could explain seven morphological features. The principal component scatter plot showed that the NH, CH, and LL populations had similar morphology. Using the stepwise discriminant method to establish the classification and discrimination functions of the seven populations, the discrimination accuracy of the DL population was 93.3% for P1 and 87.5% for P2, which was the highest, and the comprehensive discrimination rate was 71.4%. The clustering relationship diagram showed that the populations were divided into three branches, and the CH and NH populations were closest. In contrast, the DL and HF populations were farthest from the other populations. One-way ANOVA showed significant differences (P<0.05) among all traits of the populations, and the morphological differences between the HX and DL populations were the largest. The results of this study showed specific differences in the external morphology of golden pompano among different populations.
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ItemIdentification and pathogenicity of Aeromonas veronii isolated from sexually mature female Hypophthalmichthys molitrix( 2023)An outbreak of bacterial septicemia in female silver carp *Hypophthalmichthys molitrix*, which caused significant death of the fish in the Yantian Reservoir, was investigated. The pathogen was isolated from diseased fish and identified as *Aeromonas veronii* utilizing biochemical characteristics and molecular methods analyses. An artificial infection experiment indicated that the strain caused 100% mortality of juvenile silver carp and mature female fish with eggs but no death of the mature male fish. Silver carp challenged with *A. veronii* showed similar clinical signs with naturally infected fish. The histopathological study revealed that *A. veronii* infection caused the increment of hemosiderin granules and the vacuole formation in tissues of the spleen and livers, as well as the collapse, deformation, and disintegration of egg cells. The ACP, AKP, and CAT enzyme activities in the serum of both naturally and artificially infected silver carp were decreased significantly with the severe infection. In this study, *A. veronii* was isolated and identified as the primary bacterial pathogen causing the mass death of sexually mature female silver carp with eggs in Yantian Reservoir.
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ItemComparative analysis of phosphoproteomic in the intestine of Sepia lycidas under different salinity environments( 2023)Cuttlefish are sensitive to the breeding environment, and the low-salinity environment significantly impacts their growth and immunity. So far, it is difficult to breed this species artificially. This study was conducted in Sepia lycidas. And the aim was to investigate the differences in protein phosphorylation in the intestine of S. lycidas under different salinity conditions. Firstly, 999 phosphoproteins (specific peptide ≥ 1), 1928 phosphopeptides, and 2727 phosphorylation sites were identified. Among them were 284 down-regulated expression phosphorylation sites (corresponding to 115 phosphoproteins) and 674 up-regulated expression phosphorylation sites (corresponding to 408 phosphoproteins) in the intestine under a low salinity environment compared with that under a natural salinity environment. Next, GO analysis found that more phosphoproteins corresponding to differentially expressed phosphorylation sites were related to anatomical structure development, multicellular organism development, regulation of the cellular process, etc. The molecular functions of these proteins mainly contain protein binding, transferase activity, catalytic activity, and heterocyclic compound binding. And they are mainly involved in the cellular components of intracellular anatomical structure, organelle, and cytoplasm. KEGG enrichment analysis of the differential phosphoproteins suggested that many significantly enriched pathways were related to the phosphatidylinositol signaling system, cell junction (adherens junction and tight junction), and inositol phosphate metabolism. Finally, changes in environmental salinity can affect the intestinal structure, metabolism, and immune homeostasis of S. lycidas.
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ItemEffects of dietary oxidized fish oil on the growth performance, intestinal health, and antioxidant capacity of zebrafish( 2023)This study aimed to investigate the effects of oxidized fish oil (OFO) on growth performance, intestinal health, and antioxidant function and to determine the minimum concentration of oxidized fish oil to cause irreversible damage to the intestinal tissue structure of zebrafish. A 30-day feeding trial on zebrafish (average weight 0.054 g) was conducted in triplicate groups of fish fed four test diets containing different concentrations of OFO: 0% OFO (OFF, blank control), 2% OFO (OF1), 4% OFO (OF2), and 6% OFO (OF3). The body weight gain (WG), specific growth rates (SGR), feed conversion ratio (FCR), survival rate (SR), and antioxidant function {glutathione peroxidase (GSH-PX), total superoxide dismutase (T-SOD), catalase (CAT), and malondialdehyde (MDA)} were recorded. The intestinal structure was observed at the end of the trial. After the 14-day experimental period, Final body weight (FBW), WG, and SGR decreased significantly with the increase in the concentration of feed OFO (P < 0.05), while FCR showed a downward trend. The activity of T-SOD decreased significantly, the activities of GSH-PX and CAT, and the MDA content increased significantly with the increase in the concentration of feed OFO (P < 0.05). The intestinal morphological damage score showed an upward trend with the increase in the concentration of OFO, and it was significantly higher in group OF2 and OF3 than in group OF1 (P < 0.05). After the 28-day test period, the experimental indexes and intestinal antioxidant function trends were the same as those on 14 days. The increased OFO concentration significantly increased the intestinal morphological injury score (P < 0.05). These results demonstrated that adding 4% OFO to the feed for 14 days could induce irreversible damage to the intestinal tissue structure, weaken the antioxidant function, and decrease the growth performance of zebrafish.
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ItemEffect of dietary Ginkgo biloba leaf on the growth performance and nonspecific immunity of red swamp crayfish Procambarus clarkii( 2023)This trial investigated the effect of dietary Ginkgo biloba leaf (GBL) on the growth performance and nonspecific immunity of red swamp crayfish Procambarus clarkii. 180 Crayfishes were randomly divided into three groups. One group was fed with basic diet, whereas the other two groups were fed with diets containing 1% and 3% GBL. After 32 days of feeding, GBL addition tended to increase the body weight gain rate compared with control. In 3% GBL group, the bodyweight gain rate of male crayfish was higher than that of female crayfish. While female crayfish were advantageous in terms of meat yield. Liver-related indexes were influenced by GBL addition and 3% GBL could reduce glutamic pyruvic transaminase and glutamic oxaloacetic transaminase as well as total cholesterol in male crayfish, showing its function in liver protection. Moreover, GBL addition effects on liver protection was better in male crayfish than female crayfish.
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ItemEffects of morphological traits on living body weight of wild Cyclina sinensis in different geographical populations( 2023)Eleven coastal geographical populations of wild Cyclina sinensis in China were collected in February 2020, and the effects of four morphological traits (shell length; shell height; shell width; external ligament length) on one weight trait (living body weight) were studied by correlation analysis, path analysis, determination coefficient analysis, and regression analyses. The statistical results showed that the coefficient of body weight variation was generally greater than morphological traits(P＜0.05). The correlation analysis results showed that the coefficient of correlation between morphological traits (except for external ligament length) and body weight are significantly positive (P＜0.05) in all populations. Based on the results of path analysis and determination coefficient analysis, shell length has the greatest direct effect on body weight in the Yancheng population; shell height has the greatest direct effect on body weight in Dandong, Fuzhou and Tangshan populations; shell width has the greatest direct effect on body weight in Zhanjiang, Wenzhou, Dongtai, Ningbo, Tianjin, Dongying, and Wanning populations. Multiple regression equations were obtained with body weight as the dependent variable, shell length, height, and width and external ligament length as independent variables. The results of systematic clustering showed that there are no apparent geographical differentiation characteristics among eleven geographical populations in morphology. This study provided a scientific basis for selective and genetic breeding and can guide the development and utilization of wild C. sinensis seed resources.