The fish gill is a multipurpose organ that, in addition to providing for aquatic gas exchange, plays dominant roles in osmotic and ionic regulation, acid-base regulation, and excretion of nitrogenous wastes Thus, despite the fact that all fish groups have functional kidneys, the gill epithelium is the site of many processes that are mediated by renal epithelia in terrestrial vertebrates Indeed, many of the pathways that mediate these processes in mammalian renal epithelial are expressed in the gill, and many of the extrinsic and intrinsic modulators of these processes are also found in fish endocrine tissues and the gill itself The basic patterns of gill physiology were outlined over a half century ago, but modern immunological and molecular techniques are bringing new insights into this complicated system Nevertheless, substantial questions about the evolution of these mechanisms and control remain

https://people.clas.ufl.edu/devans/files/PRVGill.pdf

The Multifunctional Fish Gill: Dominant Site of Gas Exchange, Osmoregulation, Acid-Base Regulation, and Excretion of Nitrogenous Waste

http://aerg.canberra.edu.au/library/sex_general/2002_Devlin_Nagahama_sex_determination_in_fish_review.pdf

Sex determination and sex differentiation in fish: an overview of genetic, physiological, and environmental influences

Cortisol is the principal corticosteriod in teleost fishes and its plasma concentrations rise dramatically during stress. The relationship between this cortisol increase and its metabolic consequences are subject to extensive debate. Much of this debate arises from the different responses of the many species used, the diversity of approaches to manipulate cortisol levels, and the sampling techniques and duration. Given the extreme differences in experimental approach, it is not surprising that inconsistencies exist within the literature. This review attempts to delineate common themes on the physiological and metabolic roles of cortisol in teleost fishes and to suggest new approaches that might overcome some of the inconsistencies on the role of this multifaceted hormone. We detail the dynamics of cortisol, especially the exogenous and endogenous factors modulating production, clearance and tissue availability of the hormone. We focus on the mechanisms of action, the biochemical and physiological impact, and the interaction with other hormones so as to provide a conceptual framework for cortisol under resting and/or stressed states. Interpretation of interactions between cortisol and other glucoregulatory hormones is hampered by the absence of adequate hormone quantification, resulting in correlative rather than causal relationships.

Cortisol in teleosts: dynamics, mechanisms of action, and metabolic regulation

Marine stickleback fish have colonized and adapted to thousands of streams and lakes formed since the last ice age, providing an exceptional opportunity to characterize genomic mechanisms underlying repeated ecological adaptation in nature. Here we develop a high-quality reference genome assembly for threespine sticklebacks. By sequencing the genomes of twenty additional individuals from a global set of marine and freshwater populations, we identify a genome-wide set of loci that are consistently associated with marine-freshwater divergence. Our results indicate that reuse of globally shared standing genetic variation, including chromosomal inversions, has an important role in repeated evolution of distinct marine and freshwater sticklebacks, and in the maintenance of divergent ecotypes during early stages of reproductive isolation. Both coding and regulatory changes occur in the set of loci underlying marine-freshwater evolution, but regulatory changes appear to predominate in this well known example of repeated adaptive evolution in nature.

/pdf/the-genomic-basis-of-adaptive-evolution-in-threespine-27yq6s7i0b.pdf

The genomic basis of adaptive evolution in threespine sticklebacks

The vertebrate gene repertoire is characterized by “cryptic” genes whose identification has been hampered by their absence from the genomes of well-studied species. One example is the Bmp16 gene, a paralog of the developmental key genes Bmp2 and -4. We focus on the Bmp2/4/16 group of genes to study the evolutionary dynamics following gen(om)e duplications with special emphasis on the poorly studied Bmp16 gene. We reveal the presence of Bmp16 in chondrichthyans in addition to previously reported teleost fishes and reptiles. Using comprehensive, vertebrate-wide gene sampling, our phylogenetic analysis complemented with synteny analyses suggests that Bmp2, -4 and -16 are remnants of a gene quartet that originated during the two rounds of whole-genome duplication (2R-WGD) early in vertebrate evolution. We confirm that Bmp16 genes were lost independently in at least three lineages (mammals, archelosaurs and amphibians) and report that they have elevated rates of sequence evolution. This finding agrees with their more “flexible” deployment during development; while Bmp16 has limited embryonic expression domains in the cloudy catshark, it is broadly expressed in the green anole lizard. Our study illustrates the dynamics of gene family evolution by integrating insights from sequence diversification, gene repertoire changes, and shuffling of expression domains.

/pdf/asymmetric-paralog-evolution-between-the-cryptic-gene-bmp16-25ezgtbm1m.pdf

Asymmetric paralog evolution between the “cryptic” gene Bmp16 and its well-studied sister genes Bmp2 and Bmp4

Extraordinary salmon growth

Two gonadotropins, GTH I and GTH II, were isolated from pituitaries of spawning coho salmon (Oncorhynchus kisutch) using sequential extractions with ammonium acetate (pH 9.0) and 40% ethanol, precipitation with 80% ethanol, gel filtration chromatography (Sephadex G-100), anion-exchange chromatography (Mono-Q Sepharose), and gel filtration chromatography (Sephadex G-75). Coho salmon GTH I and GTH II stimulated steroidogenesis in vitro in a similar dose-dependent manner when incubated with either ovaries or testes of prepubertal coho salmon. An in vivo bioassay using coho salmon parr demonstrated that coho salmon GTH I and GTH II did not contain thyrotropic activity. Molecular weights were estimated by gel filtration chromatography to be 43,000 and 39,000 for GTH I and GTH II, respectively. Analysis of coho salmon GTH I and GTH II on reversed-phase high-performance liquid chromatography (rpHPLC) revealed that they consist of alpha and beta subunits with N-terminal amino acid residues of Tyr, Gly (alpha, beta of GTH I) and Tyr,Ser (alpha, beta of GTH II). Coho salmon GTH I-beta and GTH II-beta differed from each other in amino acid composition, N-terminal amino acids (Gly vs. Ser), and molecular weights in SDS-PAGE (19,000 vs. 20,000) and had a high degree of chemical similarity to chum salmon GTH I-beta and GTH II-beta, respectively. Specific rabbit antisera to the beta subunits of coho salmon GTH I and GTH II were generated. The observation of two GTHs with distinctly different chemical characteristics in coho salmon is similar to what has previously been found in chum salmon.

/pdf/isolation-and-characterization-of-two-coho-salmon-magqsud1hr.pdf

Isolation and characterization of two coho salmon gonadotropins, GTH I and GTH II.

Pituitary gonadotropins, follicle-stimulating hormone (FSH) and luteinizing hormone (LH), play central roles in regulating gametogenesis and the production of gonadal hormones required for the development of sexual behavior and secondary sex characters in all vertebrates. Studies in fish conducted nearly 50 years ago demonstrated that removal of the pituitary caused cessation of gametogenesis in both sexes (Pickford and Atz 1957); however, the exact chemical nature two fish gonadotropins homologous to mammalian LH and FSH was not determined until the mid to late 1980’s. Since that time, a great deal of information has emerged on the structure of FSH and LH from numerous species within Teleostei, one Chondrostean and one Chondricthyan (Querat et al. 2000, 2001; Yaron et al. 2003). In this paper, the present status of our understanding of structure and function of LH and FSH in fish is briefly reviewed. For a comprehensive review of fish gonadotropin regulation and gene structures the reader is referred to Yaron et al. 2003.

Biochemistry and physiology of fish gonadotropins

https://digitalcommons.calpoly.edu/cgi/viewcontent.cgi?article=1341&context=bio_fac

Neural defects and cardiac arrhythmia in fish larvae following embryonic exposure to 2,2′,4,4′-tetrabromodiphenyl ether (PBDE 47)

BACKGROUND: Polybrominated diphenyl ether (PBDE) flame retardants have been implicated as
disruptors of the hypothalamic-pituitary-thyroid axis. Animals exposed to PBDEs may show
reduced plasma thyroid hormone (TH), but it is not known whether PBDEs impact TH-regulated
pathways in target tissues.
OBJECTIVE: We examined the effects of dietary exposure to 2,2´,4,4´-tetrabromodiphenyl ether
(PBDE-47)—commonly the highest concentrated PBDE in human tissues—on plasma TH levels
and on gene transcripts for glycoprotein hormone a-subunit (GPHa) and thyrotropin s-subunit
(TSHs) in the pituitary gland, the autoinduced TH receptors a and s in the brain and liver, and
the TH-responsive transcription factor basic transcription element-binding protein (BTEB) in
the brain.
METHODS: Breeding pairs of adult fathead minnows (Pimephales promelas) were given dietary
PBDE-47 at two doses (2.4 µg/pair/day or 12.3 µg/pair/day) for 21 days.
RESULTS: Minnows exposed to PBDE-47 had depressed plasma thyroxine (T4), but not
3,5,3´-triiodothyronine (T3). This decline in T4 was accompanied by elevated mRNA levels for TSHs
(low dose only) in the pituitary. PBDE-47 intake elevated transcript for TH receptor a in the brain of
females and decreased mRNA for TH receptor s in the brain of both sexes, without altering these
transcripts in the liver. In males, PBDE-47 exposure also reduced brain transcripts for BTEB.
CONCLUSIONS: Our results indicate that dietary exposure to PBDE-47 alters TH signaling at multiple
levels of the hypothalamic-pituitary-thyroid axis and provide evidence that TH-responsive pathways
in the brain may be particularly sensitive to disruption by PBDE flame retardants.
KEY WORDS: basic transcription element-binding protein, brain, endocrine disruption, PBDE-47,
polybrominated diphenyl ethers, thyroid hormone, thyroid hormone receptor, thyroid-stimulating
hormone, thyrotropin. Environ Health Perspect 116:1694–1699 (2008). doi:10.1289/ehp.11570
available via http://dx.doi.org/ [Online 1 August 2008]

/pdf/dietary-exposure-to-2-2-4-4-tetrabromodiphenyl-ether-pbde-47-8hoghyfpzp.pdf

Dietary Exposure to 2,2´,4,4´-Tetrabromodiphenyl Ether (PBDE-47) Alters Thyroid Status and Thyroid Hormone–Regulated Gene Transcription in the Pituitary and Brain

Penny Swanson

Papers

Extraordinary salmon growth

Isolation and characterization of two coho salmon gonadotropins, GTH I and GTH II.

Biochemistry and physiology of fish gonadotropins

Neural defects and cardiac arrhythmia in fish larvae following embryonic exposure to 2,2′,4,4′-tetrabromodiphenyl ether (PBDE 47)

Dietary Exposure to 2,2´,4,4´-Tetrabromodiphenyl Ether (PBDE-47) Alters Thyroid Status and Thyroid Hormone–Regulated Gene Transcription in the Pituitary and Brain