Experimental reproduction of White Feces Syndrome in whiteleg shrimp, Penaeus vannamei

White Feces Syndrome (WFS) is an emergent disease of penaeid shrimp (Penaeus monodon and P. vannamei) that is identified by the presence of floating white fecal strings on pond water in grow-out ponds. Although the clinical manifestations of WFS are well defined, the underling etiology remains obscure. WFS has been associated with several enteric pathogens, including Enterocytozoon hepatopenaei (EHP). The association is based on studies that found areas where WFS has been reported, the prevalence and severity of EHP infection are high. In this study, we describe an experimental reproduction of WFS in P. vannamei pre-infected with EHP and challenged with a unique isolate of Vibrio parahaemolyticus isolated from the gastrointestinal tract of a shrimp displaying WFS. Upon laboratory challenge, shrimp displaying white fecal strings and white discoloration of the gastrointestinal tract were analyzed by histopathology, in-situ hybridization and quantitative PCR. Histological analysis confirmed the lesions of EHP and septic hepatopancreatic necrosis in the hepatopancreas of shrimp exposed to both pathogens. Quantitative PCR showed shrimp infected with both EHP and V. parahaemolyticus had a significantly higher load of EHP compared to shrimp infected with EHP alone. This is the first demonstration of experimental reproduction of WFS under laboratory conditions when animals are infected with EHP and V. parahaemolyticus concurrently. The data revealed a synergistic relation between EHP and V. parahaemolyticus isolate that led to the manifestation of WFS. We propose the gross signs of WFS can be used as an indicator of the presence of EHP infection in association with a particular strain of an enteric Vibrio spp. in countries where EHP is endemic.

Dietary Probiotic Pediococcus acidilactici MA18/5M Improves the Growth, Feed Performance and Antioxidant Status of Penaeid Shrimp Litopenaeus stylirostris: A Growth-Ration-Size Approach

Probiotics are increasingly documented to confer health and performance benefits across farmed animals. The aim of this study was to assess the effect of a constant daily intake of the single-strain probiotic Pedicococcus acidilactici MA18/5M (4 × 108 CFU.day−1.kg−1 shrimp) fed over fixed, restricted ration sizes (1% to 6% biomass.day−1) on the nutritional performance and metabolism of adult penaeid shrimp Litopenaeus stylirostris (initial body-weight, BWi = 10.9 ± 1.8 g). The probiotic significantly increased the relative daily growth rate (RGR) across all ration size s tested (Mean-RGR of 0.45 ± 0.08 and 0.61 ± 0.07% BWi.day−1 for the control and probiotic groups, respectively) and decreased the maintenance ration (Rm) and the optimal ration (Ropt) by 18.6% and 11.3%, respectively. Accordingly, the probiotic group exhibited a significantly higher gross (K1) and net (K2) feed conversion efficiency with average improvement of 35% and 30%, respectively. Enhanced nutritional performances in shrimps that were fed the probiotic P. acidilactici was associated with, in particular, significantly higher α-amylase specific activity (+24.8 ± 5.5% across ration sizes) and a concentration of free-glucose and glycogen in the digestive gland at fixed ration sizes of 3% and below. This suggests that the probiotic effect might reside in a better use of dietary carbohydrates. Interestingly, P. acidilactici intake was also associated with a statistically enhanced total antioxidant status of the digestive gland and haemolymph (+24.4 ± 7.8% and +21.9 ± 8.5%, respectively; p < 0.05). As supported by knowledge in other species, enhanced carbohydrate utilization as a result of P. acidilactici intake may fuel the pentose-phosphate pathway, generating NADPH or directly enhancing OH-radicals scavenging by free glucose, in turn resulting in a decreased level of cellular oxidative stress. In conclusion, the growth-ration method documented a clear contribution of P. acidilactici MA18/5M on growth and feed efficiency of on-growing L. stylirostris that were fed fixed restricted rations under ideal laboratory conditions. The effect of the probiotic on α-amylase activity and carbohydrate metabolism and its link to the shrimp’s antioxidant status raises interesting prospects to optimize dietary formulations and helping to sustain the biological and economic efficiency of the penaeid shrimp-farming industry.

When and why direct transmission models can be used for environmentally persistent pathogens

Variants of the susceptible-infected-removed (SIR) model of Kermack & McKendrick (1927) enjoy wide application in epidemiology, offering simple yet powerful inferential and predictive tools in the study of diverse infectious diseases across human, animal and plant populations. Direct transmission models (DTM) are a subset of these that treat the processes of disease transmission as comprising a series of discrete instantaneous events. Infections transmitted indirectly by persistent environmental pathogens, however, are examples where a DTM description might fail and are perhaps better described by models that comprise explicit environmental transmission routes, so-called environmental transmission models (ETM). In this paper we discuss the stochastic susceptible-exposed-infected-removed (SEIR) DTM and susceptible-exposed-infected-removed-pathogen (SEIR-P) ETM and we show that the former is the timescale separation limit of the latter, with ETM host-disease dynamics increasingly resembling those of a DTM when the pathogen’s characteristic timescale is shortened, relative to that of the host population. Using graphical posterior predictive checks (GPPC), we investigate the validity of the SEIR model when fitted to simulated SEIR-P host infection and removal times. Such analyses demonstrate how, in many cases, the SEIR model is robust to departure from direct transmission. Finally, we present a case study of white spot disease (WSD) in penaeid shrimp with rates of environmental transmission and pathogen decay (SEIR-P model parameters) estimated using published results of experiments. Using SEIR and SEIR-P simulations of a hypothetical WSD outbreak management scenario, we demonstrate how relative shortening of the pathogen timescale comes about in practice. With atttempts to remove diseased shrimp from the population every 24h, we see SEIR and SEIR-P model outputs closely conincide. However, when removals are 6-hourly, the two models’ mean outputs diverge, with distinct predictions of outbreak size and duration.

Genome assembly of the Australian black tiger shrimp (Penaeus monodon) reveals a fragmented IHHNV EVE sequence

Shrimp are a valuable aquaculture species globally; however, disease remains a major hindrance to shrimp aquaculture sustainability and growth. Mechanisms mediated by endogenous viral elements (EVEs) have been proposed as a means by which shrimp that encounter a new virus start to accommodate rather than succumb to infection over time. However, evidence on the nature of such EVEs and how they mediate viral accommodation is limited. More extensive genomic data on Penaeid shrimp from different geographical locations should assist in exposing the diversity of EVEs. In this context, reported here is a PacBio Sequel-based draft genome assembly of an Australian black tiger shrimp (Penaeus monodon) inbred for one generation. The 1.89 Gbp draft genome is comprised of 31,922 scaffolds (N50: 496,398 bp) covering 85.9% of the projected genome size. The genome repeat content (61.8% with 30% representing simple sequence repeats) is almost the highest identified for any species. The functional annotation identified 35,517 gene models, of which 25,809 were protein-coding and 17,158 were annotated using interproscan. Scaffold scanning for specific EVEs identified an element comprised of a 9,045 bp stretch of repeated, inverted and jumbled genome fragments of Infectious hypodermal and hematopoietic necrosis virus (IHHNV) bounded by a repeated 591/590 bp host sequence. As only near complete linear ~4 kb IHHNV genomes have been found integrated in the genome of P. monodon previously, its discovery has implications regarding the validity of PCR tests designed to specifically detect such linear EVE types. The existence of conjoined inverted IHHNV genome fragments also provides a means by which hairpin dsRNAs could be expressed and processed by the shrimp RNA interference (RNAi) machinery.

The Northern Gulf of Mexico

This chapter describes the Gulf of Mexico (GOM) region and the major issues facing this marine fisheries ecosystem, and presents some summary statistics related to the 90 indicators of ecosystem-based fisheries management (EBFM) criteria. The region contains high numbers of marine species comprising commercially and recreationally important invertebrate (e.g., penaeid shrimp, blue crab, eastern oyster) and finfish (e.g., red snapper, grouper, red drum, pelagic sportfishes) fisheries, which contribute heavily to national landings and seafood supply. The northern GOM contains one of the nation’s largest marine economies (among the eight U.S. regional marine ecosystems), which is dependent on offshore mineral extractions, tourism, marine transportation, living marine resources (LMRs), and other ocean uses. The GOM provides critical social and economic benefits to the region and the nation, is a region with high numbers of managed species, yet exploitation of these resources and an increasing human population makes the GOM an area subject to significant natural and human stressors, including the highest number of hurricanes in the U.S. Atlantic region, large expanses of hypoxic bottom water, overfishing, and major oil spills like the 2010 DWH event.

Diversity and Ecological Index of Penaeid Shrimp Collected from Mangrove Area of Kuala Langsa, Aceh, Indonesia

Shrimp is a fishery product that has high economic value. However, information of diversity and ecological index of penaeid shrimp Kuala Langsa was not well reported. Thus, this study aims to determine the species, analyze the ecological index and analyze the long relationship in penaeid shrimp caught in the Kuala Langsa mangrove waters. This study used purposive sampling method, for sampling was carried out with three locations and three repetitions. The results of the identification research found three species of the Penaeus genus with a total of 144 individuals consisting of P. monodon, P. indicus and P. merguiensis species with an average abundance value per station of 0.18, 0.09 and 0.21 ind/m2, the diversity index with an average number of 0.98 is categorized as low, the uniformity index 0.9 is categorized as high and the dominance index 0.37 is categorized as low. The length and weight relationship of male and female P. monodon species showed positive and negative allometric patterns, male and female P. indicus showed the same pattern, namely negative allometric and male and female P. merguiensis showed isometric and negative allometric patterns. Shrimp is a fishery product that has high economic value

DNA Barcoding of Penaeidae (Decapoda; Crustacea): Non-Distance-Based Species Delimitation of the Most Economically Important Shrimp Family

The Penaeidae family includes some of the most economic and ecological important marine shrimp, comprising hundreds of species. Despite this importance and diversity, the taxonomic classification for penaeid shrimp has constantly been revised, and issues related to the species identification are common. In this study, we implemented DNA barcoding analyses in addition to single-gene species delimitation analyses in order to identify molecular operational taxonomy units (MOTUs) and to generate robust molecular information for penaeid shrimp based on the cytochrome oxidase subunit I (COI) mitochondrial gene. Our final data set includes COI sequences from 112 taxa distributed in 23 genera of penaeids. We employed the general mixed Yule coalescent (GMYC) model, the Poisson tree processes (PTP), and the Bayesian PTP model (bPTP) for MOTUs delimitation. Intraspecific and interspecific genetic distances were also calculated. Our findings evidenced a high level of hidden diversity, showing 143 MOTUs, with 27 nominal species not agreeing with the genetic delimitation obtained here. These data represent potential new species or highly structured populations, showing the importance of including a non-distance-based species delimitation approach in biodiversity studies. The results raised by this study shed light on the Penaeidae biodiversity, addressing important issues about taxonomy and mislabeling in databases and contributing to a better comprehension of the group, which can certainly help management policies for shrimp fishery activity in addition to conservation programs.

Metagenomic analysis of microbial communities in the sediments of a semi-intensive penaeid shrimp culture system

The present study reports metagenomic sequencing and microbial diversity analysis of the sediment samples of a semi-intensive penaeid shrimp culture system. 16S rRNA gene-based high-throughput sequencing revealed distinct and diverse microbial communities in the analyzed sample. Analysis of the results showed a high abundance of Proteobacteria followed by Verrucomicrobia, Bacteroidetes, Planctomycetes, Firmicutes, Cyanobacteria, and Actinobacteria in the metagenome retrieved from the sediment sample. Unclassified bacteria also contributed a significant portion of the metagenome. Two potential shrimp pathogens viz Vibrio harveyi and Acinetobacter lwoffii detected in the sediment sample show the risk associated with the pond. Microbes that play essential roles in nutrient cycling and mineralization of organic compounds such as Bacteroidetes, Planctomycetes, Gammaproteobacteria, Firmicutes, Cyanobacteria, and Actinobacteria could also be identified. The present study provides preliminary data with respect to the microbial community present in the sediments of a shrimp culture system and emphasizes the application of metagenomics in exploring the microbial diversity of aquaculture systems, which might help in the early detection of pathogens within the system and helps to develop pathogen control strategies in semi-intensive aquaculture systems.