Aquimarina sp. Associated With a Cuticular Disease of Cultured Larval Palinurid and Scyllarid Lobsters

Abstract

Shell (cuticular) disease manifests in various forms and affects many crustaceans, including lobsters. Outbreaks of white leg disease (WLD) with distinct signs of pereiopod tissue whitening and death have been observed in cultured larvae (phyllosomas) of ornate spiny lobster Panulirus ornatus , eastern rock lobster Sagmariasus verreauxi , and slipper lobster Thenus australiensis . This study aimed to characterise and identify the causative agent of WLD through morphological and molecular (16S rRNA gene and whole genome sequencing) analysis, experimental infection of damaged/undamaged P. ornatus and T. australiensis phyllosomas, and bacterial community analysis (16S rRNA gene amplicon sequencing) of P. ornatus phyllosomas presenting with WLD during an outbreak. Bacterial communities of WLD-affected pereiopods showed low bacterial diversity and dominant abundance of Aquimarina spp. compared to healthy pereiopods, which were more diverse and enriched with Sulfitobacter spp. 16S rRNA gene Sanger sequencing of cultures from disease outbreaks identified the dominant bacterial isolate (TRL1) as a Gram-negative, long non-flagellated rod with 100% sequence identity to Aquimarina hainanensis . Aquimarina sp. TRL1 was demonstrated through comparative genome analysis (99.99% OrthoANIu) as the bacterium reisolated from experimentally infected phyllosomas presenting with typical signs of WLD. Pereiopod damage was a major predisposing factor to WLD. Histopathological examination of WLD-affected pereiopods showed masses of internalised bacteria and loss of structural integrity, suggesting that Aquimarina sp. TRL1 could enter the circulatory system and cause death by septicaemia. Aquimarina sp. TRL1 appears to have important genomic traits (e.g., tissue-degrading enzymes, gliding motility, and aggregate-promoting factors) implicated in the pathogenicity of this bacterium. We have shown that Aquimarina sp. TRL1 is the aetiological agent of WLD in cultured Palinurid and Scyllarid phyllosomas and that damaged pereiopods are a predisposing factor to WLD.

Insights into the Antimicrobial Activities and Metabolomes of Aquimarina (Flavobacteriaceae, Bacteroidetes) Species from the Rare Marine Biosphere

“…Several OTUs did not closely affiliate with the known Aquimarina -type strains, pointing towards a wealth of likely unknown Aquimarina species yet to be cultivated. This hypothesis was further supported by the many recent reports of new Aquimarina isolates [ 4 , 16 , 18 , 21 , 38 ] and metagenome-assembled genomes (MAGs) [ 39 , 40 , 41 ], even though this genus was already described in 2005 [ 9 ]. Furthermore, an open pangenome was observed in our previous comparative genomics study, indicating that genomic redundancy was still far from being achieved [ 24 ].…”

“…In the SMP dataset analyzed in this study, Aquimarina was more often identified in sediments than in the sponge samples, pointing towards a lack of preference for host-associated settings. However, it is important to consider reports of Aquimarina species as emerging pathogens of algae [ 13 , 42 ] and crustaceans [ 38 , 43 ]. In a recent metagenomics study of the octocoral microbiome, an Aquimarina OTU was enriched in necrotic octocoral tissue, suggesting it could be an indicator of dysbiosis [ 44 ].…”

Barriers in European spiny lobster (Palinurus elephas) aquaculture: What we know so far?

“…Bacterial infections are commonly reported in farmed operations and can lead to high mortalities 93 . The early stages in lobster development are often the most susceptible to bacterial infections, particularly to Vibrio and Aquimarina pathogen species 92,94 …”

“…The gut microbiome plays a critical role in the overall health of the host organism. This has major implications that include impacts on growth, digestion, immune response and resistance to pathogens 94 . The core gut microbiome of P. ornatus is dominated by Tenericutes and Proteobacteria, with Vibrionaceae also being commonly found in the intestinal tract, which likely plays a role in digestion 151 .…”

“…This has major implications that include impacts on growth, digestion, immune response and resistance to pathogens. 94 The core gut microbiome of P. ornatus is dominated by Tenericutes and Proteobacteria, with Vibrionaceae also being commonly found in the intestinal tract, which likely plays a role in digestion. 151 In-depth studies on P. elephas gut microbiota are however limited, but inferences can be made with other species where data exists from recent investigations.…”