Gene Characterization of Nocturnin Paralogues in Goldfish: Full Coding Sequences, Structure, Phylogeny and Tissue Expression.

The aim of this work is the full characterization of all the nocturnin (noc) paralogues expressed in a teleost, the goldfish. An in silico analysis of the evolutive origin of noc in Osteichthyes is performed, including the splicing variants and new paralogues appearing after teleostean 3R genomic duplication and the cyprinine 4Rc. After sequencing the full-length mRNA of goldfish, we obtained two isoforms for noc-a (noc-aa and noc-ab) with two splice variants (I and II), and only one for noc-b (noc-bb) with two transcripts (II and III). Using the splicing variant II, the prediction of the secondary and tertiary structures renders a well-conserved 3D distribution of four α-helices and nine ß-sheets in the three noc isoforms. A synteny analysis based on the localization of noc genes in the patrilineal or matrilineal subgenomes and a phylogenetic tree of protein sequences were accomplished to stablish a classification and a long-lasting nomenclature of noc in goldfish, and valid to be extrapolated to allotetraploid Cyprininae. Finally, both goldfish and zebrafish showed a broad tissue expression of all the noc paralogues. Moreover, the enriched expression of specific paralogues in some tissues argues in favour of neo- or subfunctionalization.

First evidence of nocturnin in fish: two isoforms in goldfish differentially regulated by feeding.

Nocturnin (NOC) is a unique deadenylase with robust rhythmic expression involved in the regulation of metabolic processes in mammals. Currently, the possible presence of NOC in fish is unknown. This report aimed to identify NOC in a fish model, the goldfish ( Carassius auratus), and to study the possible regulation of its expression by feeding. Two partial-length cDNAs of 293 and 223 bp, named nocturnin-a ( noc-a) and nocturnin-b ( noc-b), were identified and found to be highly conserved among vertebrates. Both mRNAs show a similar widespread distribution in central and peripheral tissues, with higher levels detected for noc-a compared with noc-b. The periprandial expression profile revealed that noc-a mRNAs rise sharply after a meal in hypothalamus, intestinal bulb, and liver, whereas almost no changes were observed for noc-b. Food deprivation was found to exert opposite effects on the expression of both NOCs (generally inhibitory for noc-a, and stimulatory for noc-b) in the three mentioned tissues. A single meal after a 48-h food deprivation period reversed (totally or partially) the fasting-induced decreases in noc-a transcripts in all studied tissues and the increases in noc-b expression in the intestinal bulb. Together, this study offers the first report of NOC in fish and shows a high dependence of its expression on feeding and nutritional status. The differential responses to feeding of the two NOCs raise the possibility that they might be underlying different physiological mechanisms (e.g., food intake, lipid mobilization, energy homeostasis) in fish.

Daily Rhythms in the IGF-1 System in the Liver of Goldfish and Their Synchronization to Light/Dark Cycle and Feeding Time.

The relevance of the insulin-like growth factor-1 (IGF-1) system in several physiological processes is well-known in vertebrates, although little information about their temporal organization is available. This work aims to investigate the possible rhythmicity of the different components of the IGF-1 system (igf-1, the igf1ra and igf1rb receptors and the paralogs of its binding proteins IGFBP1 and IGFBP2) in the liver of goldfish. In addition, we also study the influence of two environmental cues, the light/dark cycle and feeding time, as zeitgebers. The hepatic igf-1 expression showed a significant daily rhythm with the acrophase prior to feeding time, which seems to be strongly dependent on both zeitgebers. Only igfbp1a-b and igfbp1b-b paralogs exhibited a robust daily rhythm of expression in the liver that persists in fish held under constant darkness or randomly fed. The hepatic expression of the two receptor subtypes did not show daily rhythms in any of the experimental conditions. Altogether these results point to the igf-1, igfbp1a-b, and igfbp1b-b as clock-controlled genes, supporting their role as putative rhythmic outputs of the hepatic oscillator, and highlight the relevance of mealtime as an external cue for the 24-h rhythmic expression of the IGF-1 system in fish.

Economic Improvement of Artisanal Fishing by Studying the Survival of Discarded Plectorhinchus mediterraneus.

Europe calls for the end to fisheries discards, which means bringing all caught fish (subject to minimum sizes or quotas) to land. This decision is beneficial to the ecosystem, since it forces the selectivity of the fishing gears to improve. However, artisanal fishermen find themselves in a vulnerable situation where their subsistence depends on catches with small profit margins. An exemption to this landing obligation exists, as it is also ruled that those animals whose survival is scientifically guaranteed may be returned to the sea. Here we study the survival of Plectorhinchus mediterraneus captured by hookline and gillnet, as well as their physiological recovery. Survival exceeds 93% in both cases. The physiological assessment of primary (cortisol) and secondary (energy mobilization, acid-base and hydromineral balance, and immune system) stress responses indicates that surviving animals are able to recover after fishing. Thus, we propose the optimal size of capture of this species to achieve greater economic benefit. For this, we rely on the prices according to size in recent years, as well as on the growth curves of the species. In this way, by releasing fish of less than 1 kg, the current benefits could be multiplied between 2.3 and 9.6 times. This pilot study lays the groundwork for regulating artisanal fisheries through scientific data related to survival of discards along with information on the sale prices.