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Antioxidant and immune responses of the Oriental river prawn Macrobrachium nipponense to the isopod parasite Tachaea chinensis

https://doi.org/10.1016/j.fsi.2020.03.039Get rights and content

Highlights

  • We observed prawn host antioxidant defense systems and immune function responses to Tachaea chinensis parasites.

  • Key redox enzyme activities and genes peaked after 6 days of parasite exposure.

  • Expression of key immune-related enzymes and genes also peaked at this point.

  • These results provide valuable insights into characterizing isopod parasite and shrimp host interactions.

Abstract

Tachaea chinensis is a parasitic isopod that negatively affects the production of several commercially important shrimp species in China. To date, there have been no reports on the antioxidant and immune responses of host shrimps to isopod parasite infection or their underlying molecular mechanisms. In this study, we examined the specific activities of the immune and antioxidant enzymes of the shrimp Macrobrachium nipponense during the course of a 15-day isopod infection and evaluated expression of related genes. Acid phosphatase (ACP) and alkaline phosphatase (AKP) activities and malondialdehyde (MDA) levels showed significant peaks over 15 days of exposure in both the hepatopancreas and muscle (P < 0.05), whereas catalase (CAT) activity increased continuously during infection (P < 0.05), and lysozyme (LZM) activity increased only in the hepatopancreas (P < 0.05). After 6 days of exposure, expressions of glutathione S-transferase (GST), ACP, and AKP were significantly higher than at 12 days. Compared with the control group, at 12 days, S-(hydroxymethyl) glutathione dehydrogenase activity and glutathione metabolism pathways were significantly inhibited (P < 0.05). Furthermore, the NOD-like receptor signaling pathway and antigen processing and presentation pathways were also significantly inhibited at 12 days compared with that at 6 days (P < 0.05), indicating that T. chinensis parasitism could perturb the antioxidant and immune systems of shrimp hosts during the latter stages of infection. Additionally, the molting and mortality rates of M. nipponense increased the duration of parasitism. These findings indicate that M. nipponense can activate antioxidant and immune defense systems during the early period during isopod parasitism, whereas the parasite can negatively affect these host defense systems during the latter period. Our findings accordingly provide valuable insights into the antioxidant defense systems and immune function characterizing parasite–host interactions.

Introduction

Parasitic isopods are widely distributed across a diverse range of habitats, including freshwater, brackish water, and marine environments [[1], [2], [3]]. They are unique in using fish and crustaceans as both intermediate and definitive hosts, and feed on the blood, mucus, and tissue of hosts using specialized mouthparts [[4], [5], [6]]. As vectors of other disease, they can predispose hosts to opportunistic pathogens, including viruses, bacteria, fungi, and other parasites [7,8]. Parasitic isopod infections in commercial aquacultured fish and crustaceans can result considerable economic losses [[9], [10], [11]]. Isopod parasites can stunt growth, or injure and kill their hosts due to nutrient deprivation and destruction of the defense system, but aspects of crustacean host defense remain poorly understood.

Tachaea chinensis, a common isopod ectoparasite of economically important shrimp species, is widely distributed in Asia [11,12], and parasitizes various cultured shrimps, including Palaemonetes sinensis, Exopalaemon carinicauda, Litopenaeus vannamei, and Macrobrachium nipponense [11]. We previously found that T. chinensis secretes antihemostatic, anti-inflammatory, and immunomodulatory molecules to facilitate blood meal acquisition and inhibit the shrimp immune system during parasitism [6]. However, immune-related genes and proteins in shrimp hosts are not significantly affected after a 14-day exposure to parasitism (midterm infection) [6,13,14]. It has been widely established that immune responses in fish hosts are markedly influenced by ectoparasite exposure duration, and that the ability to suppress and reject parasites shortly after infection can be associated with innate immunity. This is particularly important as it can substantially influence subsequent immune progress [[15], [16], [17], [18]]. However, the early immune responses of crustaceans against isopod ectoparasite infection have yet to be clarified.

The Oriental river prawn M. nipponense is an economically and nutritionally important species, and is considered one of the most important freshwater prawns for aquaculture in China, Korea, Vietnam, and Japan [19]. As an extensively cultured and popularly consumed species, the annual production of M. nipponense in China has gradually increased in recent years to about 234,358 tons in 2018 with an annual output value of >20 billion RMB (2.8 billion USD). It has become an important means of increasing agricultural efficiency and farmers' incomes [20]. However, recent studies have shown that T. chinensis has parasitized both aquacultured and wild M. nipponense in China and neighboring countries [11,12]. Our knowledge of the immune responses of M. nipponense their roles in protection against parasites is limited. Many studies indicate that antioxidant and immune related enzymes including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), malondialdehyde (MDA), lysozyme (LZM), phenol oxidase (PO), acid phosphatase (ACP), and alkaline phosphatase (AKP) represent the first line of defense in nonspecific immune responses in crustacean [21,22]. In this study, we evaluated these nonspecific immune defense responses during the early infection period by investigating the activity of antioxidant defense enzymes. We also performed transcriptome analysis to determine the integrated molecular mechanisms underlying T. chinensis parasitism of M. nipponense and the resultant host responses.

Section snippets

Animals and sample collection

M. nipponense individuals (weight: 1.86 ± 0.44 g, length: 4.45 ± 0.57 cm) were purchased from a local aquaculture market in Shenyang City, Liaoning Province, China. T. chinensis (weight: 0.04 ± 0.01 g, length: 1.12 ± 0.23 cm) were collected from a rice field in Panjin City, Liaoning Province, China. Both prawns and parasites were acclimatized in an aerated recycling freshwater system. The water temperature was maintained at 22 ± 0.5 °C and with a light:dark cycle of 12:12 h. After acclimation

Survival, molting, total weight loss, and daily weight loss during parasite exposure

The survival rate was observed to decrease with increasing exposure duration (Fig. 1A). After 15 days, survival reached approximately 70%, whereas the molt rate increased continuously throughout exposure to approximately 55%. Total weight loss increased by 8% at day 3 but was not significantly different compared with that at the other assessed time points (Fig. 1B). However, the rate of daily weight loss decreased with an increase in exposure duration and was significantly higher at 3 days than

Discussion

Numerous studies have indicated that ectoparasitic isopods feed on host blood (hemolymph) and exudates, eventually resulting in host death or weight loss [3,[23], [24], [25]]. Here, we found that the mortality rate of M. nipponense increased concomitantly with infection duration, and reached 30% after 15 day of T. chinensis parasitism. We previously observed that T. chinensis parasitism can cause 50% mortality in the Chinese grass shrimp Palaemonetes sinensis after infection for 2 weeks [6,13,26

Conclusions

In this study, we provide the first findings indicating that the isopod parasite T. chinensis can adversely affect the antioxidant and immune systems of its shrimp host M. nipponense. Notably, multiple enzymes and genes associated with the antioxidant and immune systems, including SOD, MDA, AKP, ACP and GST, exhibited patterns characterized by an initial increase and subsequent decrease in response to infection, suggesting that parasitism could perturb these host defense systems during the

CRediT authorship contribution statement

Yingdong Li: Writing - original draft, Writing - review & editing. Zhibin Han: Writing - original draft. Weibin Xu: Formal analysis, Investigation. Xin Li: Formal analysis, Investigation. Yingying Zhao: Data curation. Hua Wei: Data curation. Xiaodong Li: Resources. Qijun Chen: Writing - review & editing, Supervision, Project administration, Funding acquisition.

Declaration of competing interest

The authors declare no conflicts of interest.

Acknowledgments

This work was supported by the earmarked fund for Modern Agro-industry Technology Research System (No. CARS-48), the Liaoning Provincial Natural Science Foundation of China (No. 2019MS274), and the Talent Introduction Program of Shenyang Agricultural University (No. 880417024). We thank Panjin Guanghe Fisheries Co. Ltd for providing shrimps and parasites.

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