Effectiveness of an immune toolbox to determine the host response to infection and stress in two decapod species, Homarus gammarus (L) and Carcinus maenas (L)

Abstract

Decapod crustaceans are ecologically and economically valuable, yet are vulnerable to a variety of stressors in both natural and farmed environments. Immune biomarkers have been commonly used to assess host transcriptional response to infection and disease in Decapoda. Here, the transcription of various immune genes was quantified to assess the host response of the European lobster, Homarus gammarus (L.) and the shore crab, Carcinus maenas (L.) to a number of stress scenarios. Selected immune genes included carcinin, (C. maenas) and crustin (H. gammarus), antimicrobial peptides, peroxinectin, a cell adhesion molecule and osponin and the zymogen prophenoloxidase.
Prophenoloxidase cleaves to form active phenoloxidase which is involved in the melanisation of many invading pathogens. The immune gene transcription was quantified using real-time PCR. The efficacy of this suite of biomarkers was tested in the context of either pathogen history, as a predictor of viral or bacterial challenge in decapods or in response to non-pathogen related stress (high stocking density).


In H. gammarus, the predictive capacity of this ‘toolbox’ of immune genes was quantified in response to White Spot Syndrome Virus (WSSV) infection, a viral pathogen with a wide host range and known to cause mortality, most notably in penaeid species. For C. maenas, the transcription of the immune genes was quantified to assess the host impact of different pathogen burdens in two distinct, wild populations. Further, the predictive capacity of the biomarkers was quantified in C. maenas in response to two controlled infection studies with either a Gram positive (Planococcus citreus) or Gram negative (Listonella anguillarum) bacteria. Lastly, the wider applicability of this suite of biomarkers was assessed as a general indicator of stress in C. maenas.

Overall, the transcription of carcinin, peroxinectin and prophenoloxidase differed between C. maenas populations in response to pathogen assemblages and site-specific differences. In response to viral (H. gammarus) and bacterial (C. maenas) challenge and the non-pathogenic stress challenge (C. maenas), there was no significant change in peroxinectin and prophenoloxidase transcription. Interestingly, the transcription of crustin (H. gammarus) and carcinin (C. maenas) changed significantly in response to all of these challenges. This suggests a much wider role for these antimicrobial peptides as biomarkers in both viral and bacterial challenges and in response to stress associated with high stocking density. The efficacy of antimicrobial peptides in response to bacterial and viral pathogens and non-pathogen stressors should be assessed in other species to understand its applicability and limitations as a biomarker in the wider decapod community.

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ORCID for Chris Hauton: orcid.org/0000-0002-2313-4226

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