Journal of Aquatic Animal Health

Appuhami, Ishini A; Bajracharya, Shrijan; Davis, D Allen; Bruce, Timothy J

doi: 10.1093/jahafs/vsag001pmid: 42085326

ObjectiveThis study evaluated the effect of commercial Bacillus spp. probiotics on growth performance, immunity, gut microbiota composition, and disease resistance to Vibrio parahaemolyticus in Pacific white shrimp Litopenaeus vannamei that were reared under biofloc conditions.MethodsA 56-d feeding trial was conducted in a static biofloc system with postlarval shrimp (1.00 ± 0.03 g). A total of 1,080 shrimp were randomly assigned to three groups: two treatment levels (recommended dose [PRO × 1] and a doubled dose [PRO × 2]) of a commercial probiotic blend, PRO4000X, alongside a control group (CTL; no probiotics). At the trial end point, hepatopancreas and gut samples were collected for gene expression. Gut samples were also obtained for gut microbiota analysis via 16S ribosomal RNA sequencing, and hemolymph samples were withdrawn to measure the total hemocyte count.ResultsProbiotic applications did not significantly affect growth performance, including final biomass, mean weight, survival, and feed conversion ratio under the experimental conditions. The probiotic-treated shrimp exhibited enhanced survival during a V. parahaemolyticus (strain A3) challenge, with significantly lower mortality rates (P < 0.001; 42.5 ± 4.3% for PRO × 1 and 60 ± 6.5% for PRO × 2) relative to the CTL (100 ± 0.00%). Immune parameters, such as total hemocyte count, did not differ. Interestingly, the expression of the antioxidant gene sod (superoxide dismutase) in the shrimp gut was significantly downregulated in the PRO × 1 group relative to the control (P = 0.030), which suggests reduced oxidative stress under probiotic supplementation. The analysis of the gut microbiota revealed differences in alpha diversity, specifically in evenness and Shannon index, which were significantly higher in the PRO × 1 group. The analysis of the bacterial composition also revealed minor shifts in the dominant genera. Notably, Lysobacter was more abundant in the PRO × 1 group, which potentially reflects positive modulation of gut microbial communities in response to probiotic supplementation.ConclusionsOverall, the application of PRO4000X probiotics significantly reduced the V. parahaemolyticus infection in the shrimp that were reared in biofloc water and supported the regulation of immunity and microbial communities in the gut. These findings indicate that probiotics potentially help to improve shrimp health when shrimp are cultured in biofloc systems.

van Eijk, Nadiah M H A; Vogt, Nina; Stidworthy, Mark F; Northrup, Emily; Rich, Andrew F

doi: 10.1093/jahafs/vsag003pmid: 42223582

ObjectivesGiven the limited ocular pathology data for common cuttlefish Sepia officinalis and hummingbird bobtail squid Euprymna berryi despite their high visual dependency, the purpose of this study was to investigate and describe the ophthalmic lesions in a cohort of laboratory-housed common cuttlefish and hummingbird bobtail squid.MethodsCases were retrospectively selected from the International Zoo Veterinary Group Pathology database that reported confirmed clinical ophthalmic lesions or histopathological lesions. Twenty-five cases were identified that included clinical records and gross and histopathological examination of whole specimens. The cases included 19 common cuttlefish and six hummingbird bobtail squid, thus providing a sample of 50 eyes and orbital cavities.ResultsThirty-two of 50 individual eyes (64%) and 30 of 50 white bodies (60%) were affected. The most frequent lesion that was observed was inflammation (n = 29/32, 91%), primarily manifesting as uveitis (n = 23/32, 72%) and phakitis (n = 10/32, 31%). Cataracts were also common (n = 14/32, 44%), often with cataract-associated inflammation (n = 9/14, 64%). Leukopoietic hyperplasia of the white body was bilaterally observed in 15 of 25 animals (60%) and was thought to be associated with exophthalmos. In the absence of notable intraocular or infraorbital lesions in some animals, this change was considered reactive, likely in response to nonocular lesions, such as ulcerative dermatitis and branchitis. Notable additional findings included hypopyon-like lesions (n = 3/32, 9%), a single case of congenital ocular malformation, and one case with mesenchymal proliferations that were reminiscent of florid fibroplasia.ConclusionsThis study contributes to the expanding knowledge of cephalopod ocular pathology, with previously unreported findings in these cephalopods including congenital ocular malformation and cases of ­hypopyon-like lesions with proteinaceous material exudation and hemocytes in the anterior chamber. Additionally, it offers specific insights into the ocular pathology of the hummingbird bobtail squid.