Mickie L. Powell

Current Knowledge of Hagfish Reproduction: Implications for Fisheries Management

Abstract This review briefly summarizes the latest findings on reproductive endocrinology of Atlantic hagfish (Myxine glutinosa) and implications for fisheries management. In response to a major decline or collapse of the fisheries (groundfish and anadromous species) industry in the Northeast, species that were once considered alternative or underutilized have and are being identified that may be suitable for commercial harvest, one such example is the hagfish. Hagfish in recent years have been sought after as valuable fish not only for their flesh, but also their skin. Currently, there are no regulations governing the harvesting of hagfish along the East Coast. There has been little to no information of the life history of hagfish including growth rate, age determination, reproductive biology, life span, and larval size at hatching. Thus, the level at which a sustainable fisheries for this species can be maintained is unknown. In some parts of the world, hagfish stocks are being depleted due to overfishing. In order for fisheries management to manage its hagfish stocks and develop a sustainable commercial hagfish fishery, critical information is needed to assist in determining the optimal use of this valuable resource. Key elements of the reproductive system have not been elucidated in hagfish. However, there is new evidence from recent reproductive studies that Atlantic hagfish may have a seasonal reproductive cycle. These data include seasonal changes in gonadotropin-releasing hormone (GnRH), gonadal steroids, estradiol and progesterone, corresponding to gonadal reproductive stages along with the putative identity of a functional corpus luteum. This newly acquired data may provide important information to fisheries managers of the East Coast.

Fundamental Approaches to the Study of Zebrafi sh Nutrition

The value of the zebrafish model has been well established. However, culture variability within and among laboratories remains a concern, particularly as it relates to nutrition. Investigators using rodent models addressed this concern several decades ago and have developed strict nutritional regimes to which their models adhere. These investigators decreased the variability associated with nutrition in most studies by developing standardized reference and open formulation diets. Zebrafish investigators have not embraced this approach. In this article, we address the problems associated with the lack of nutritional information and standardization in the zebrafish research community. Based on the knowledge gained from studies of other animals, including traditional research models, other fish species, domesticated and companion animals, and humans, we have proposed an approach that seeks to standardize nutrition research in zebrafish. We have identified a number of factors for consideration in zebrafish nutrition studies and have suggested a number of proposed outcomes. The long term-goal of nutrition research will be to identify the daily nutritional requirements of the zebrafish and to develop appropriate standardized reference and open formulation diets.

Biochemical and Energy Requirements of Gonad Development

The importance of understanding energy allocation to developing gonads in cultured sea urchins can be summarized in a simple question: ‘what is the greatest yield of gonad tissue mass one can obtain with the lowest ration of food?’ In considering the growth and development of gonadal tissue as a harvestable resource, the balance between yield and ration can best be described in terms of the chemical constituents that limit gonad growth, i.e., the biochemical components in the shortest supply (ration) restrict development of the gonad tissues (yield). In this chapter we consider the metabolic activities in the sea urchin gonad in relation to an individual’s diet to identify the tissue constituents that have the highest anabolic costs and are thus the most likely to restrict or limit tissue production. Although whole-animal, energy metabolism (respiration and biochemical pathways) has been well studied in adult urchins, we focus specifically on what little is known about the metabolic activities in sea urchin gonads.

Dietary Protein Source Influence on Body Size and Composition in Growing Zebrafish

The importance of nutritional components on growth and body composition outcomes has been demonstrated in multiple model organisms. Although zebrafish (Danio rerio) have an established role in research laboratories for its utility in understanding developmental biology and genetics, the influence of diet composition on basic growth outcomes is less well demonstrated. In the current study, four protein sources were tested in isolation using isonitrogenous diets or combined using a defined lab diet. Fish (n≈60/group) were group housed (n≤10 fish/1.8 L tank) and fed ad libitum three times daily for 12 weeks. Fish were assessed for effects on length, body weight, and body composition (lean and fat mass). Individuals fed wheat gluten protein were significantly shorter in length, with significantly lower body weight and lean mass in both male and female fish, although percent body fat was high compared with other diets. Casein-fed fish similarly had significantly reduced body length, body weight, and lean and fat mass in both male and female fish, with a low percent body fat compared with other diets (leanest). Fish protein hydrolysate-fed fish had significantly lower lean mass and a high percent body fat, whereas soy protein isolate diet performed similarly to a mixed-protein control diet for all measured outcomes. These results suggest that the protein source, with accompanying amino acid ratios or additional protein source differences, has a significant impact on growth and body composition outcomes in zebrafish when fed in a semipurified, defined diet background.

Heme Oxygenase-1 Protects Corexit 9500A-Induced Respiratory Epithelial Injury across Species

The effects of Corexit 9500A (CE) on respiratory epithelial surfaces of terrestrial mammals and marine animals are largely unknown. This study investigated the role of CE-induced heme oxygenase-1 (HO-1), a cytoprotective enzyme with anti-apoptotic and antioxidant activity, in human bronchial airway epithelium and the gills of exposed aquatic animals. We evaluated CE-mediated alterations in human airway epithelial cells, mice lungs and gills from zebrafish and blue crabs. Our results demonstrated that CE induced an increase in gill epithelial edema and human epithelial monolayer permeability, suggesting an acute injury caused by CE exposure. CE induced the expression of HO-1 as well as C-reactive protein (CRP) and NADPH oxidase 4 (NOX4), which are associated with ROS production. Importantly, CE induced caspase-3 activation and subsequent apoptosis of epithelial cells. The expression of the intercellular junctional proteins, such as tight junction proteins occludin, zonula occludens (ZO-1), ZO-2 and adherens junctional proteins E-cadherin and Focal Adhesion Kinase (FAK), were remarkably inhibited by CE, suggesting that these proteins are involved in CE-induced increased permeability and subsequent apoptosis. The cytoskeletal protein F-actin was also disrupted by CE. Treatment with carbon monoxide releasing molecule-2 (CORM-2) significantly inhibited CE-induced ROS production, while the addition of HO-1 inhibitor, significantly increased CE-induced ROS production and apoptosis, suggesting a protective role of HO-1 or its reaction product, CO, in CE-induced apoptosis. Using HO-1 knockout mice, we further demonstrated that HO-1 protected against CE-induced inflammation and cellular apoptosis and corrected CE-mediated inhibition of E-cadherin and FAK. These observations suggest that CE activates CRP and NOX4-mediated ROS production, alters permeability by inhibition of junctional proteins, and leads to caspase-3 dependent apoptosis of epithelial cells, while HO-1 and its reaction products protect against oxidative stress and apoptosis.

An abundance of Epsilonproteobacteria revealed in the gut microbiome of the laboratory cultured sea urchin, Lytechinus variegatus

In this study, we have examined the bacterial community composition of the laboratory cultured sea urchin Lytechinus variegatus gut microbiome and its culture environment using NextGen amplicon sequencing of the V4 segment of the 16S rRNA gene, and downstream bioinformatics tools. Overall, the gut and tank water was dominated by Proteobacteria, whereas the feed consisted of a co-occurrence of Proteobacteria and Firmicutes at a high abundance. The gut tissue represented Epsilonproteobacteria as dominant, with order Campylobacterales at the highest relative abundance (>95%). However, the pharynx tissue was dominated by class Alphaproteobacteria. The gut digesta and egested fecal pellets had a high abundance of class Gammaproteobacteria, from which Vibrio was found to be the primary genus, and Epsilonproteobacteria, with genus Arcobacter occurring at a moderate level. At the class level, the tank water was dominated by Gammaproteobacteria, and the feed by Alphaproteobacteria. Multi-Dimensional Scaling analysis showed that the microbial community of the gut tissue clustered together, as did the pharynx tissue to the feed. The gut digesta and egested fecal pellets showed a similarity relationship to the tank water. Further analysis of Campylobacterales at a lower taxonomic level using the oligotyping method revealed 37 unique types across the 10 samples, where Oligotype 1 was primarily represented in the gut tissue. BLAST analysis identified Oligotype 1 to be Arcobacter sp., Sulfuricurvum sp., and Arcobacter bivalviorum at an identity level >90%. This study showed that although distinct microbial communities are evident across multiple components of the sea urchin gut ecosystem, there is a noticeable correlation between the overall microbial communities of the gut with the sea urchin L. variegatus culture environment.

The gut microbiome of the sea urchin, Lytechinus variegatus, from its natural habitat demonstrates selective attributes of microbial taxa and predictive metabolic profiles.

In this paper, we describe the microbial composition and their predictive metabolic profile in the sea urchin Lytechinus variegatus gut ecosystem along with samples from its habitat by using NextGen amplicon sequencing and downstream bioinformatics analyses. The microbial communities of the gut tissue revealed a near-exclusive abundance of Campylobacteraceae, whereas the pharynx tissue consisted of Tenericutes, followed by Gamma-, Alpha- and Epsilonproteobacteria at approximately equal capacities. The gut digesta and egested fecal pellets exhibited a microbial profile comprised of Gammaproteobacteria, mainly Vibrio, and Bacteroidetes. Both the seagrass and surrounding sea water revealed Alpha- and Betaproteobacteria. Bray-Curtis distances of microbial communities indicated a clustering profile with low intrasample variation. Predictive metagenomics performed on the microbial communities revealed that the gut tissue had high relative abundances of metabolisms assigned to the KEGG-Level-2 designation of energy metabolisms compared to the gut digesta, which had higher carbohydrate, amino acid and lipid metabolisms. Overall, the results of this study elaborate the spatial distribution of microbial communities in the gut ecosystem of L. variegatus, and specifically a selective attribute for Campylobacteraceae in the gut tissue. Also, the predictive functional significance of bacterial communities in uniquely compartmentalized gut ecosystems of L. variegatus has been described.

Aging and energetics’ ‘Top 40’ future research opportunities 2010-2013

Background: As part of a coordinated effort to expand our research activity at the interface of Aging and Energetics a team of investigators at The University of Alabama at Birmingham systematically assayed and catalogued the top research priorities identified in leading publications in that domain, believing the result would be useful to the scientific community at large. Objective: To identify research priorities and opportunities in the domain of aging and energetics as advocated in the 40 most cited papers related to aging and energetics in the last 4 years. Design: The investigators conducted a search for papers on aging and energetics in Scopus, ranked the resulting papers by number of times they were cited, and selected the ten most-cited papers in each of the four years that include 2010 to 2013, inclusive. Results: Ten research categories were identified from the 40 papers. These included: (1) Calorie restriction (CR) longevity response, (2) role of mTOR (mechanistic target of Rapamycin) and related factors in lifespan extension, (3) nutrient effects beyond energy (especially resveratrol, omega-3 fatty acids, and selected amino acids), 4) autophagy and increased longevity and health, (5) aging-associated predictors of chronic disease, (6) use and effects of mesenchymal stem cells (MSCs), (7) telomeres relative to aging and energetics, (8) accretion and effects of body fat, (9) the aging heart, and (10) mitochondria, reactive oxygen species, and cellular energetics. Conclusion: The field is rich with exciting opportunities to build upon our existing knowledge about the relations among aspects of aging and aspects of energetics and to better understand the mechanisms which connect them.

Effect of Diet Quality on Nutrient Allocation to the Test and Aristotle's Lantern in the Sea Urchin Lytechinus variegatus (LAMARCK, 1816)

ABSTRACT Small, adult (19.50 ± 2.01g wet weight) Lytechinus variegatus (Lamarck, 1816) were fed 8 formulated diets with different protein (12–36% dry weight as fed) and carbohydrate (21–39% dry weight) levels. Each sea urchin (n = 8 per treatment) was fed a daily ration of 1.5% of the average body weight of all individuals for 9 wk. Akaike information criterion (AIC) scores were used to compare 6 different dietary composition hypotheses for 8 growth measurements. For each physical growth response, different mathematical models representing a priori hypotheses were compared using the AIC score. The AIC is one of many information—theoretical approaches that allows for direct comparison of nonnested models with varying numbers of parameters. Dietary protein level and protein:energy ratio were the best models for prediction of test diameter increase. Dietary protein level was the best model of test with spines wet weight gain and test with spines dry matter production. When the Aristotles lantern was corrected for size of the test, there was an inverse relationship with dietary protein level. Log-transformed lantern to test with spines index was also best associated with the dietary protein model. Dietary carbohydrate level was a poor predictor for growth parameters. However, the protein × carbohydrate interaction model was the best model of organic content (percent dry weight) of the test without spines. These data suggest that there is a differential allocation of resources when dietary protein is limiting and the test, but not the Aristotles lantern, is affected by availability of dietary nutrients.

Metagenomics approach to the study of the gut microbiome structure and function in zebrafish Danio rerio fed with gluten formulated diet

In this study, we report the gut microbial composition and predictive functional profiles of zebrafish, Danio rerio, fed with a control formulated diet (CFD), and a gluten formulated diet (GFD) using a metagenomics approach and bioinformatics tools. The microbial communities of the GFD-fed D. rerio displayed heightened abundances of Legionellales, Rhizobiaceae, and Rhodobacter, as compared to the CFD-fed counterparts. Predicted metagenomics of microbial communities (PICRUSt) in GFD-fed D. rerio showed KEGG functional categories corresponding to bile secretion, secondary bile acid biosynthesis, and the metabolism of glycine, serine, and threonine. The CFD-fed D. rerio exhibited KEGG functional categories of bacteria-mediated cobalamin biosynthesis, which was supported by the presence of cobalamin synthesizers such as Bacteroides and Lactobacillus. Though these bacteria were absent in GFD-fed D. rerio, a comparable level of the cobalamin biosynthesis KEGG functional category was observed, which could be contributed by the compensatory enrichment of Cetobacterium. Based on these results, we conclude D. rerio to be a suitable alternative animal model for the use of a targeted metagenomics approach along with bioinformatics tools to further investigate the relationship between the gluten diet and microbiome profile in the gut ecosystem leading to gastrointestinal diseases and other undesired adverse health effects.