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What is the primary function of the early teleost gill? Evidence for Na+/NH+4 exchange in developing rainbow trout (Oncorhynchus mykiss).

ABSTRACT: Post-hatch fishes lack a functional gill and use cutaneous surfaces for exchange with the surrounding environment. The ionoregulatory hypothesis posits that ionoregulation is the first physiological process to be limited by cutaneous exchange, necessitating its shift to the gills. We hypothesized that the ontogeny of branchial ammonia excretion (J amm) is coupled to Na(+) uptake (J Na in) in accordance with the current model for Na+/NH4+ in exchange in freshwater. Using divided chambers, branchial and cutaneous J amm, J Na in and oxygen consumption (MO2) by larval rainbow trout were assessed. Following hatch, the skin accounted for 97% and 86% of total J amm and J Na in, respectively. J amm and J Na in shifted to the gills simultaneously at 15 days post-hatch (dph) and were highly correlated (R(2) = 0.951) at the gills, but not the skin, over development. Contrastingly, MO2 shifted significantly later at 27 dph, in agreement with the ionoregulatory hypothesis. Moreover, the mRNA expression and/or enzymatic activity of Rhesus proteins, Na(+)/H(+)-exchanger, H(+)-ATPase, Na(+)/K(+)-ATPase and carbonic anhydrase, all key components of the Na+/NH4+-exchange system, increased in the gills over larval development. We propose that the ontogeny of branchial J Na in occurs as Na+/NH4+ exchange and provide evidence for a novel element to the ionoregulatory hypothesis, the excretion of potentially lethal metabolic ammonia.

SUBMITTER: Zimmer AM

PROVIDER: S-EPMC4213616 | biostudies-literature | 2014 Nov

REPOSITORIES: biostudies-literature

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What is the primary function of the early teleost gill? Evidence for Na+/NH+4 exchange in developing rainbow trout (Oncorhynchus mykiss).

Zimmer Alex M AM Wright Patricia A PA Wood Chris M CM

Proceedings. Biological sciences 20141101 1795

Post-hatch fishes lack a functional gill and use cutaneous surfaces for exchange with the surrounding environment. The ionoregulatory hypothesis posits that ionoregulation is the first physiological process to be limited by cutaneous exchange, necessitating its shift to the gills. We hypothesized that the ontogeny of branchial ammonia excretion (J amm) is coupled to Na(+) uptake (J Na in) in accordance with the current model for Na+/NH4+ in exchange in freshwater. Using divided chambers, branchi ...[more]

PMID: 25274361

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Project description:The generic term "Gill disease" refers to a wide range of disorders that affect the gills and severely impact salmonid aquaculture systems worldwide. In rainbow trout freshwater aquaculture, various etiological agents causing gill diseases have been described, particularly Flavobacterium and Amoeba species, but research studies suggest a more complex and multifactorial aetiology. Here, a cohort of rainbow trout affected by gill disease is monitored both through standard laboratory techniques and 16S rRNA Next-Generation Sequencing (NGS) analysis during a natural disease outbreak and subsequent antibiotic treatment with Oxytetracycline. NGS results show a clear clustering of the samples between pre- and post-treatment based on the microbial community of the gills. Interestingly, the three main pathogenic bacteria species in rainbow trout (Yersinia ruckeri, Flavobacterium psychrophilum, and Flavobacterium branchiophilum) appear to be weak descriptors of the diversity between pre-treatment and post-treatment groups. In this study, the dynamics of the gill microbiome during the outbreak and subsequent treatment are far more complex than previously reported in the literature, and environmental factors seem of the utmost importance in determining gill disease. These findings present a potential novel perspective on the diagnosis and management of gill diseases, showing the limitations of conventional laboratory methodologies in elucidating the complexity of this disease in rainbow trout. To the authors' knowledge, this work is the first to describe the microbiome of rainbow trout gills during a natural outbreak and subsequent antibiotic treatment. The results of this study suggest that NGS can play a critical role in the analysis and comprehension of gill pathology. Using NGS in future research is highly recommended to gain deeper insights into such diseases correlating gill's microbiome with other possible cofactors and establish strong prevention guidelines.

Project description:BackgroundGenetic maps characterizing the inheritance patterns of traits and markers have been developed for a wide range of species and used to study questions in biomedicine, agriculture, ecology and evolutionary biology. The status of rainbow trout genetic maps has progressed significantly over the last decade due to interest in this species in aquaculture and sport fisheries, and as a model research organism for studies related to carcinogenesis, toxicology, comparative immunology, disease ecology, physiology and nutrition. We constructed a second generation genetic map for rainbow trout using microsatellite markers to facilitate the identification of quantitative trait loci for traits affecting aquaculture production efficiency and the extraction of comparative information from the genome sequences of model fish species.ResultsA genetic map ordering 1124 microsatellite loci spanning a sex-averaged distance of 2927.10 cM (Kosambi) and having 2.6 cM resolution was constructed by genotyping 10 parents and 150 offspring from the National Center for Cool and Cold Water Aquaculture (NCCCWA) reference family mapping panel. Microsatellite markers, representing pairs of loci resulting from an evolutionarily recent whole genome duplication event, identified 180 duplicated regions within the rainbow trout genome. Microsatellites associated with genes through expressed sequence tags or bacterial artificial chromosomes produced comparative assignments with tetraodon, zebrafish, fugu, and medaka resulting in assignments of homology for 199 loci.ConclusionThe second generation NCCCWA genetic map provides an increased microsatellite marker density and quantifies differences in recombination rate between the sexes in outbred populations. It has the potential to integrate with cytogenetic and other physical maps, identifying paralogous regions of the rainbow trout genome arising from the evolutionarily recent genome duplication event, and anchoring a comparative map with the zebrafish, medaka, tetraodon, and fugu genomes. This resource will facilitate the identification of genes affecting traits of interest through fine mapping and positional cloning of candidate genes.

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Dataset Information

What is the primary function of the early teleost gill? Evidence for Na+/NH+4 exchange in developing rainbow trout (Oncorhynchus mykiss).

Publications

What is the primary function of the early teleost gill? Evidence for Na+/NH+4 exchange in developing rainbow trout (Oncorhynchus mykiss).

Similar Datasets

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