SalmonellaandVibriospecies were isolated and identified fromLitopenaeus vannameicultured in shrimp farms. Shrimp samples showed occurrence of 3.3% ofSalmonellaand 48.3% ofVibrio. The isolates were also screened for antibiotic resistance to oxolinic acid, sulphonamides, tetracycline, sulfamethoxazole/trimethoprim, norfloxacin, ampicillin, doxycycline hydrochloride, erythromycin, chloramphenicol, and nitrofurantoin.Salmonella entericaserovar Corvallis isolated from shrimp showed individual and multiple antibiotic resistance patterns. FiveVibriospecies having individual and multiple antibiotic resistance were also identified. They wereVibrio cholerae(18.3%),V. mimicus(16.7%),V. parahaemolyticus(10%),V. vulnificus(6.7%), andV. alginolyticus(1.7%). Farm owners should be concerned about the presence of these pathogenic bacteria which also contributes to human health risk and should adopt best management practices for responsible aquaculture to ensure the quality of shrimp.

With recent technologies making it possible for commercial scale closed life-cycle aquaculture production of spiny lobster (Panulirus ornatus) comes a strong impetus to further understand aspects of lobster health. The gut microbiome plays a crucial role in host health, affecting growth, digestion, immune responses and pathogen resistance. Herein we characterise and compare gut microbiomes across different developmental stages (6–7 days post-emergence [dpe], 52 dpe and 13 months post-emergence [mpe]) and gut regions (foregut, midgut and hindgut) of cultured P. ornatus juveniles. Gut samples were analysed using 16S rRNA next-generation sequencing. Core gut microbiomes of P. ornatus comprised the phyla Tenericutes and Proteobacteria. Within class Gammaproteobacteria, families Pseudoalteromonadaceae and Vibrionaceae were dominant members across the majority of the gut microbiomes. Characterisation of bacterial communities from 13 mpe lobsters indicated that the hindgut microbiome was more diverse and compositionally dissimilar to the foregut and midgut. The bacterial composition of the hindgut was more similar among younger juveniles (6–7 dpe and 52 dpe) compared to 13 mpe lobsters. This is the first study to explore gut microbiomes of spiny lobster juveniles. We demonstrate that the composition of the gut microbiome was shaped by gut region, whereas the structure of the hindgut microbiome was influenced by developmental stage.

Lobsters have an open circulatory system with haemolymph that contains microorganisms even in the healthy individuals. Understanding the role of these microorganisms becomes increasingly important particularly for the diagnosis of disease as the closed life-cycle aquaculture of the spiny lobsterPanulirus ornatusnears commercial reality. This study aimed to characterise haemolymph responses of healthy culturedP.ornatusjuveniles at control (28 °C) and elevated (34 °C) temperatures. This was assessed by measuring immune parameters (total granulocyte counts, total haemocyte counts, clotting times), and culture-independent (pyrosequencing of haemolymph DNA) and culture-dependent (isolation using nonselective growth medium) techniques to analyse bacterial communities from lobster haemolymph sampled on days 0, 4 and 6 post-exposure to the temperature regimes. Elevated temperature (34 °C) affected lobster survival, total granulocyte counts, and diversity, load and functional potential of the haemolymph bacterial community. Pyrosequencing analyses showed that the core haemolymph microbiome consisted of phyla Proteobacteria and Bacteriodetes. Overall, culture-independent methods captured a higher bacterial diversity and load when compared to culture-dependent methods, however members of theRhodobacteraceaewere strongly represented in both analyses. This is the first comprehensive study providing comparisons of haemolymph bacterial communities from healthy and thermally stressed cultured juvenileP.ornatusand has the potential to be used in health monitoring programs.

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.

Bdellovibrio and like organisms (BALOs) are Gram-negative obligate predators of other bacteria in a range of environments. The recent discovery of BALOs in the circulatory system of cultured spiny lobster P. ornatus warrants more investigation. We used a combination of co-culture agar and broth assays and transmission electron microscopy to show a Halobacteriovorax sp. strain Hbv preyed upon the model prey bacterium Vibrio sp. strain Vib. The haemolymph microbiome of juvenile P. ornatus was characterised following injection of phosphate buffered saline (control) or prey and/or predator bacteria for 3 d. The predator Hbv had no effect on survival compared to the control after 3 d. However, when compared to the prey only treatment group, lobsters injected with both prey and predator showed significantly lower abundance of genus Vibrio in the haemolymph bacterial community composition. This study indicates that predatory bacteria are not pathogenic and may assist in controlling microbial population growth in the haemolymph of lobsters.

The commercial onshore aquaculture of the spiny lobster Panulirus ornatus, while in its infancy, has progressed rapidly from the enabling research that continues at the University of Tasmania. The development of lobster feeds, both fresh and manufactured, has been critical to the success of this emerging aquaculture sector. Fresh feeds derived from mussel represent the gold standard in terms of the growth performance of juvenile lobsters. Nonetheless, concerns regarding availability, sustainability, and potential biosecurity issues of fresh feeds highlight the importance of developing manufactured feeds for lobster aquaculture. Wild lobsters are assumed to have a balanced natural diet that allows for standard growth and development, and as such natural diets are often used as a reference for feed development. Similarly, the gut microbiota associated with a natural diet is assumed to reflect a healthy microbial assemblage. The aim of this study was to compare the microbiota of the hindgut and hepatopancreas of cultured P. ornatus fed with a commercial prawn pellet or mussel to that of wild spiny lobster juveniles. Gut samples were analysed using Oxford Nanopore 16S rRNA gene sequencing. Based on principal coordinate analysis, the gut bacteria of cultured lobsters were different from the wild juveniles. The core microbiota of the hindgut and hepatopancreas libraries were phyla Proteobacteria (Gamma, Alpha) and Bacteroidetes. Vibrio was the most dominant genus in both organs. The differences in bacterial relative abundance were mainly between cultured (pellet-, mussel-fed) and wild lobsters. In conclusion, bacteria in the cultured lobsters had significantly different profiles to that of the wild juveniles, indicating that current onshore aquaculture practices alter the gut microbiota. A number of different feeding and culture practices may be required if the aim of closed culture practices is to attain a gut microbiota in cultured animals that is representative of that found in wild spiny lobsters.