Marine Teleost Research Articles

Evaluation of an Acute Osmotic Stress in European Sea Bass via Skin Mucus Biomarkers

Simple SummarySkin mucus biomarkers have become relevant indicators for studying fish physiological status and welfare. Here, we evaluated them in terms of the acute osmotic response of the sea bass. Change of mucus volume exuded and main stress-related metabolites explain the putative energy loss implied in a hyper/hypo-osmotic response. We demonstrated that skin mucus is a valuable tool, comparable to classical blood markers, for evaluating sea bass response to acute salinity challenges as well as some other potentially stressful situations. This technique will allow ecologists, physiologists, and aquafarmers to monitor fish welfare and to analyse endangered migrating species without affecting their vulnerable populations.European sea bass is a marine teleost which can inhabit a broad range of environmental salinities. So far, no research has studied the physiological response of this fish to salinity challenges using modifications in skin mucus as a potential biological matrix. Here, we used a skin mucus sampling technique to evaluate the response of sea bass to several acute osmotic challenges (for 3 h) from seawater (35‰) to two hypoosmotic environments, diluted brackish water (3‰) and estuarine waters (12‰), and to one hyperosmotic condition (50‰). For this, we recorded the volume of mucus exuded and compared the main stress-related biomarkers and osmosis-related parameters in skin mucus and plasma. Sea bass exuded the greatest volume of skin mucus with the highest total contents of cortisol, glucose, and protein under hypersalinity. This indicates an exacerbated acute stress response with possible energy losses if the condition is sustained over time. Under hyposalinity, the response depended on the magnitude of the osmotic change: shifting to 3‰ was an extreme salinity change, which affected fish aerobic metabolism by acutely modifying lactate exudation. All these data enhance the current scarce knowledge of skin mucus as a target through which to study environmental changes and fish status.

Molecular and morphological sex differentiation in sablefish (Anoplopoma fimbria), a marine teleost with XX/XY sex determination.

Phenotypic sex of an organism is determined by molecular changes in the gonads, so-called molecular sex differentiation, which should precede the rise of cellular or anatomical sex-distinguishing features. This study characterized molecular and morphological sex differentiation in sablefish (Anoplopoma fimbria), a marine teleost with established XX/XY genotypic sex determination. Next generation sequencing was conducted on sablefish ovarian and testicular mRNAs to obtain sequences for transcripts associated with vertebrate sex determination and differentiation and early reproductive development. Gene-specific PCRs were developed to determine the distribution and ontogenetic gonadal expression of transcription, growth, steroidogenic and germline factors, as well as gonadotropin and steroid receptors. Molecular changes associated with sex differentiation were first apparent in both XY- and XX-genotype sablefish at~60mm in body length and prior to histological signs of sex differentiation. The earliest and most robust markers of testicular differentiation were gsdf, amh, dmrt1, cyp11b, star, sox9a, and fshr. Markedly elevated mRNA levels of several steroidogenesis-related genes and ar2 in differentiating testes suggested that androgens play a role in sablefish testicular differentiation. The earliest markers of ovarian differentiation were cyp19a1a, lhcgr, foxl2, nr0b1, and igf3. Other transcripts such as figla, zp3, and pou5f3 were expressed predominantly in XX-genotype fish and significantly increased with the first appearance and subsequent development of primary oocytes. This study provides valuable insight to the developmental sequence of events associated with gonadal sex differentiation in marine teleosts with XX/XY sex determination. It also implicates particular genes in processes of male and female development and establishes robust molecular markers for phenotypic sex in sablefish, useful for ongoing work related to sex control and reproductive sterilization.

Whole brain transcriptomics of intermittently fed individuals of the marine teleost Sparus aurata

A major challenge in fish physiology is to understand the mechanisms underlying the transcriptomic responses of fish brain to food deprivation. Differential gene expression analysis identified in total 2240 transcripts that presented >2-fold change (adjusted p < 0.01) between each treatment and the control group (C). The identity of the transcripts was obtained with annotation against multiple public databases and they were grouped according to their expression patterns. The gene ontology terms that were substantially affected were identified by functional annotation analysis. Genes related to ion transport, cell cycle and cell adhesion were mainly regulated during fasting and refeeding. These findings contribute to identify key indicators for the molecular basis of brain functions during periods of starvation in gilthead seabream.

Dolphinfish movements in the Eastern Pacific Ocean of Mexico using conventional and electronic tags

BackgroundThe dolphinfish, Coryphaena hippurus, is a fast-swimming, predatory fish exhibiting relatively fast growth and early maturation among marine teleosts. It is an important, potentially renewable resource throughout its global subtropical-to-tropical range. Understanding the ecology of this wide-ranging fish is critical to proper fisheries management, but studies have historically depended heavily upon aggregated catch data reported by fisheries. This study uses tagging data to explore finer scale dolphinfish movements in two subregions of the Eastern Pacific Ocean (EPO)—the west coasts of Baja California Peninsula (WBC) and Oaxaca (OAX), Mexico.ResultsAdult dolphinfish (fork length 66–129 cm) were tagged with conventional (n = 132 tags) and electronic tags (n = 30 tags, miniPAT) between 2010 and 2014. Recapture rate of conventional tags was 4.5% with a maximum days of liberty of 141 days (mean = 56 d); 20 electronic tags reported but all did so prior to programmed release dates, with days at liberty ranging from 4 to 62 (mean = 24 d). Fish remained within the region they were tagged except for six fish tagged in WBC and one in OAX. Latitudinal (WBC) and longitudinal (OAX) extensions of observed fish movements (determined via a novel analytical approach) increased with days at liberty. Despite occasional deep dives (max 262 m), fish remained surface oriented with short excursions below the isothermal layer but larger OAX fish (fork length [103 cm, 120 cm]) inhabiting warmer waters (sea surface temperatures (SST) > ~ 26 °C) spent more time below the isothermal layer than smaller fish (fork length [90 cm, 112 cm]) inhabiting colder WBC surface waters (SST > ~ 22 °C).ConclusionsThis study reveals movements of dolphinfish that infer regional differences in thermal habitat utilization and displacement over time. This inference evokes questions important to fisheries management regarding the three-dimensional extent of the dolphinfish’s realized thermal niche, its population structure, and the spatiotemporal connectivity of its habitats within the multinational EPO. With improved tag retention, longer deployments should capture increasing displacements along observed axes (N/S vs. E/W); the orientation of seasonal displacement axes suggest longer-distance movements would provide opportunities for reproductive mixing via trans-national migrations.

Multiparametric monitoring of fish activity rhythms in an Atlantic coastal cabled observatory

Cabled video-observatories offer new opportunities to monitor fish species at frequencies and durations never attained before, quantifying the behavioural activities of their individuals, and providing ancillary data to inform stock assessment (in a fishery-independent manner). In this context, our objective was to improve the ecological monitoring capability of SmartBay observatory (20 m depth, Galway Bay, Ireland), through a pilot study dedicated to tracking of fish counts (as a proxy of populations activity rhythms), in a context where species behaviour and consequent community turnover may occur at different temporal cycles (i.e. tidal versus day-night). In order to understand how animals can regulate their behavioural activity upon those cycles, we enforced a time-lapse (1 h interval) image collection and concomitant multiparametric oceanographic plus acoustic data acquisition continuously during 24 h, over 30 days in August 2018 (when turbidity is at minimum). For each image, we classified and then counted all visible fish and derived count time series. Periodogram and waveform analyses were used to calculate their fluctuations' periodicity (i.e. the ruling cycle) and phase (i.e. peak timing in relation to the cycle). A total of 12 marine teleost species were pictured with Trisopterus minutus , Trachurus trachurus and Chelidonichthys lucerna characterized by day-night related rhythms, while others, such as Trisopterus luscus and Gadus morhua , were influenced by the tidal cycle. 24 h count patterns were compared together and investigated for time-based ecological niche-partitioning in a wave and current-affected soundscape. These findings were discussed in relation to the ecology of species and the feasibility of promising observatory-based monitoring applications in fishery assessment practices, when targeted species have commercial value. • Cabled video-observatories allow new opportunities for fish communities monitoring. • SmartBay coastal platform (Galway, Ireland) was used to survey fish activity rhythms. • 1-h time-lapse image and oceanographic data acquisition occurred over 30 days. • Most of fishes showed day-night but not tidal activity patterns. • A time-based ecological niche-partitioning was found in nocturnal and diurnal species.

Daily rhythms in endocrine factors of the somatotropic axis and their receptors in gilthead sea bream (Sparus aurata) larvae

Living organisms have adapted to environmental oscillations in light and temperature through evolving biological clocks. Biological rhythms are pervasive at all levels of the endocrine system, including the somatotropic (growth) axis. The objective of the present research was to study the existence of daily rhythms on the somatotropic axis of a marine teleost species, specifically, the gilthead sea bream (Sparus aurata). Larvae of S. aurata at 30 dph (days post hatching), kept under a 9 L:15D (light-dark) photoperiod, were collected every 3 h throughout a 36 h cycle. The expression of the following somatotropic axis genes was analyzed by quantitative PCR: pituitary adenylate cyclase-activating polypeptide 1 (adcyap1), prepro-somatostatin-1 (pss1), growth hormone (gh), growth hormone receptor types 1 and 2 (ghr1 and ghr2, respectively), insulin-like growth factor 1 (igf1) and igf1 receptor a (igf1ra). All genes displayed significant differences among time points and, with the exception of adcyap1, all showed statistically significant daily rhythms. The acrophases of gh, ghr1, ghr2, igf1 and igf1ra were located around the end of the dark phase, between ZT19:44 and ZT0:48 h, whereas the highest expression levels of adcyap1 occurred at ZT18 h. On the other hand, the acrophase of pss1, an inhibitor of Gh secretion, was located at ZT10:16 h, hence it was shifted by several hours with respect to the other genes. The present results provide the first thorough description of somatotropic axis rhythms in gilthead sea bream. Such knowledge provides insights into the role of rhythmic regulation of the Gh/Igf1 axis system in larval growth and metabolism, and it can also improve the implementation of more species-specific feeding regimes.

Reef-associated fishes have more maneuverable body shapes at a macroevolutionary scale

Marine habitats vary widely in structure, from incredibly complex coral reefs to simpler deep water and open ocean habitats. Hydromechanical models of swimming kinematics and microevolutionary studies suggest that these habitats select for different body shape characteristics. Fishes living in simple habitats are predicted to experience selection for energy-efficient sustained swimming, which can be achieved by fusiform body shapes. In contrast, fishes living in complex habitats are predicted to be under selection for maneuverability, which can be enhanced by deep-bodied and laterally compressed forms. To look for a signature of these processes at a broad macroevolutionary scale, we quantified the body shapes of 3322 species of marine teleostean fishes using a series of linear measurements. We scored each species for whether they were reef-associated or not and tested for morphological differences using a phylogenetic framework. Our results confirmed significant overall shape differences between reef-associated teleosts and those occupying structurally simpler marine habitats. Reef-associated species have, on average, deeper bodies and higher depth-to-width ratios, while non-reef species are more streamlined with narrower and shallower caudal peduncles. Despite the numerous evolutionary forces that may influence body shapes on a broad macroevolutionary scale, our results reveal differences in body shapes between reef-associated and non-reef species that are consistent with hydromechanical models of swimming kinematics as well as with microevolutionary patterns.

Body shape diversification along the benthic-pelagic axis in marine fishes.

Colonization of novel habitats can result in marked phenotypic responses to the new environment that include changes in body shape and opportunities for further morphological diversification. Fishes have repeatedly transitioned along the benthic-pelagic axis, with varying degrees of association with the substrate. Previous work focusing on individual lineages shows that these transitions are accompanied by highly predictable changes in body form. Here, we generalize expectations drawn from this literature to study the effects of habitat on body shape diversification across 3344 marine teleost fishes. We compare rates and patterns of evolution in eight linear measurements of body shape among fishes that live in pelagic, demersal and benthic habitats. While average body shape differs between habitats, these differences are subtle compared with the high diversity of shapes found within each habitat. Benthic living increases the rate of body shape evolution and has led to numerous lineages evolving extreme body shapes, including both exceptionally wide bodies and highly elongate, eel-like forms. By contrast, we find that benthic living is associated with the slowest diversification of structures associated with feeding. Though we find that habitat can serve as an impetus for predictable trait changes, we also highlight the diversity of responses in marine teleosts to opportunities presented by major habitats.

Characteristics delineation of piscidin 5 like from Larimichthys crocea with evidence for the potent antiparasitic activity

Several researches reported that piscidin members of teleosts owned strong antiparasitic activity. Cryptocaryon irritans, a type of ectoparasite, could infect most of the marine teleosts. Larimichthys crocea could severely suffer from marine white spot disease caused by C. irritans, and their mortality rate was significantly high. Concentrating on this problem, we have done many related works. Piscidin 5 like (termed Lc-P5L) was another piscidin member isolated from a comparative transcriptome of C. irritans-immuned L. crocea. In the paper, quantitative Real-time PCR (qRT-PCR) showed Lc-P5L was upregulated in examined tissues, including gill, head kidney, muscle, liver, spleen and intestine after challenged by C. irritans, the significant upregulation time was in accordance to key developmental stages of C. irritans, which implied different infection stages could result in host immune response. Furthermore, using microscope techniques, we observed theronts or trophonts became weakly motile, cilia became detached, cells were out of shape, membranes eventually lysed in different cell positions and cytoplasmic contents leaked. Laser confocal scanning microscope (LCSM) observed theronts macronucleus grew swell and depolymerized after treated by recombinant Lc-P5L (rLc-P5L). Data suggested rLc-P5L was significantly lethal to C. irritans, and the death state of the parasite incubated with rLc-P5L was remarkably similar to other piscidin members or other antiparasitic peptides (APPs). Thus, these data provided new insights into L. crocea immunity against C. irritans and potential of rLc-P5L as a therapeutic agent against pathogen invasion.

DNA degradation in fish: Practical solutions and guidelines to improve DNA preservation for genomic research.

The more demanding requirements of DNA preservation for genomic research can be difficult to meet when field conditions limit the methodological approaches that can be used or cause samples to be stored in suboptimal conditions. Such limitations may increase rates of DNA degradation, potentially rendering samples unusable for applications such as genome‐wide sequencing. Nonetheless, little is known about the impact of suboptimal sampling conditions. We evaluated the performance of two widely used preservation solutions (1. DESS: 20% DMSO, 0.25 M EDTA, NaCl saturated solution, and 2. Ethanol >99.5%) under a range of storage conditions over a three‐month period (sampling at 1 day, 1 week, 2 weeks, 1 month, and 3 months) to provide practical guidelines for DNA preservation. DNA degradation was quantified as the reduction in average DNA fragment size over time (DNA fragmentation) because the size distribution of DNA segments plays a key role in generating genomic datasets. Tissues were collected from a marine teleost species, the Australasian snapper, Chrysophrys auratus. We found that the storage solution has a strong effect on DNA preservation. In DESS, DNA was only moderately degraded after three months of storage while DNA stored in ethanol showed high levels of DNA degradation already within 24 hr, making samples unsuitable for next‐generation sequencing. Here, we conclude that DESS was the most promising solution when storing samples for genomic applications. We recognize that the best preservation protocol is highly dependent on the organism, tissue type, and study design. We highly recommend performing similar experiments before beginning a study. This study highlights the importance of testing sample preservation protocols and provides both practical and economical advice to improve DNA preservation when sampling for genome‐wide applications.

Predicting egg size across temperatures in marine teleost fishes

AbstractMarine teleost fish species in colder environments generally produce larger eggs than those in warmer environments. This pattern is thought to reflect changes in the optimal strategy of allocation to offspring size and number across temperatures, yet quantitative assessments of this hypothesis are lacking. Here, we model optimal offspring size across temperatures in marine teleost fishes based on the trade‐off between offspring survivorship and number. In doing so, we derive quantitative predictions for the relationship of optimal egg size to temperature based on the size and temperature dependences of the growth and mortality, and hence survivorship, of eggs and larvae. Our model shows that smaller eggs are favoured at warmer temperatures largely because egg survivorship declines with both egg size and temperature. The predictions of our model (egg mass in grams = 0.013*e−0.11*T ºC) were comparable to the observed interspecific relationship (0.0029*e−0.09*T ºC; N = 221 spp.). Thus, our results provide insights into how temperature shapes the evolution of egg size in marine teleost fishes.

First elucidation of the life cycle in the family Brachycladiidae (Digenea), parasites of marine mammals

Digeneans of the family Brachycladiidae are cosmopolitan parasites restricted to marine mammals. Their life cycles are unknown. Phylogenetically, Brachycladiidae are closely related to Acanthocolpidae, parasites of marine teleost fishes. Acanthocolpida typically possess three-host life cycles with gastropods of the superfamily Buccinoidea acting as the first intermediate hosts for most species, and either fishes or bivalves acting as the second intermediate hosts. A few species previously identified as Neophasis differ from other Acanthocolpidae in having naticid gastropods as first intermediate hosts, and both fishes and bivalves as second ones. We assumed that this may indicate an incorrect life cycle description and revised previous data on rediae and cercariae of Neophasis spp. from Cryptonatica affinis (Naticidae) and metacercariae from cardiid bivalves at the White Sea using molecular and morphological approaches. Sequence comparison showed that rediae and cercariae from C. affinis resembling some representatives of the genus Neophasis and metacercariae from bivalves resembling Neophasis oculata belong to the brachycladiid species Orthosplanchnus arcticus. Thus, the life cycle of O. arcticus proceeds as follows: seals serve as the definitive host, C. affinis as the first intermediate host and cardiid bivalves as the second. We found one more type of redia and cercaria in C. affinis which, by molecular evidence, also belongs to Brachycladiidae and is closely related to O. arcticus. Here we refer to them as Brachycladiidae gen. sp. 1 WS. We suggest that Brachycladiidae gen. sp. 1 WS may belong to either Orthosplanchnus or Odhneriella, with beluga whales possibly being the definitive host. Morphological features of O. arcticus and Brachycladiidae gen. sp. 1 WS cercariae are summarised and matched with published data on putatively brachycladiid cercariae. We compare and discuss the diversity of life cycle patterns among Brachycladiidae and Acanthocolpidae, and show that they differ not only in the type of definitive host, but also in both intermediate hosts.

Tissue distribution of triphenyltin compounds in marine teleost fishes

Continuous release of the highly toxic triphenyltin compounds (TPT) from antifouling paints and fungicides has caused serious pollution to urbanized coastal marine environments worldwide since the 1960s. Using gas-chromatography mass-spectrometry (GC–MS), this study investigated the distribution profile of TPT in 15 types of tissues of four marine teleost fish species collected from Hong Kong waters. Concentrations of TPT in various tissues had a significant positive correlation with protein contents in the tissues (r = 0.346, p < 0.001) and, to a lesser extent with lipid contents (r = 0.169, p = 0.020). Highest concentrations of TPT were consistently found in liver, ranging from 1074.9 to 3443.7 ng/g wet weight; whereas fish scales always contained the least concentration of TPT in all species, ranging from 10.4 to 48.5 ng/g wet weight. Through mass balance models and regression analyses, muscle tissues were found to contribute most to the total TPT body burden, and the average TPT concentration of both dorsal and ventral muscles was identified as the best predictor for estimating TPT burden in the entire fish. Hence, further investigations of bioaccumulation and biomagnification of TPT in fishes should adopt this modelling approach in estimating its total body burden in individual fish.

The complete mitochondrial genome of Inimicus japonicus and its phylogenetic analysis

The complete mitochondrial genome was sequenced from the marine teleost fish Inimicus japonicus. The genome sequence is 16,830 bp in size and has a base composition of A (29.25%), T (29.01%), C (20.7%), and G (21.03%). Moreover, 13 protein-coding genes (PCGs) encoded 3210 amino acids in total. The phylogenetic analysis showed that I. japonicus belongs to Synancejidae family. The complete mitochondrial genome sequences provided here would be useful for further understanding the evolution and conservation genetics of I. japonicus.

Short term cold storage and sperm concentration assessment of lumpfish (Cyclopterus lumpus. L) Milt

There is increased commercial interest in the production of lumpfish (Cyclopterus lumpus) as a biological control against sea lice infections in Atlantic salmon farming. To ensure a sustainable supply of lumpfish, reliable captive reproduction is required however, optimal husbandry and conditions for captive broodstock performance remain unknown. Artificial fertilisation of gametes remains the preferred management strategy for lumpfish, but this requires an effective milt management protocol. The present study tested several milt extender solutions for short term cold storage and validated sperm concentration assessment of lumpfish milt. Results demonstrated lumpfish sperm has a long motility survival time (motile for up to 3 h) when compared to other marine teleosts. Importantly, all extenders used in the study were non-activating on dilution of the milt. Lumpfish milt was successfully stored at 4 °C in Modified Turbot Extender (MTE), Herring Ringers Solution and Aquaboost SpermCoat (Cryogenetics, Norway) for up to 14 days post stripping. MTE performed more effectively with regards to maintenance of sperm activation time in comparison to the other tested extenders. There was a significant positive correlation between sperm concentration identified through cell counts using a haemocytometer and both packed cell volume (spermatocrit) and measured optical density at 640 nm (r2 = 97.42 ± 2.14). This suggests both packed cell volume and spectrophotometric measurements can be effective methods for rapidly assessing sperm concentration in lumpfish. This study validated several options for quantifying sperm concentration and short-term cold storage of lumpfish milt that can be used for hatchery management in lumpfish aquaculture.

Response to the comments regarding "The marine teleost fishes of the Sea of Marmara; an updated and annotated checklist" by Artüz amp; Fricke (2019).

Our recent paper Artüz Fricke (2019) provided an updated list of marine teleost fishes of the Sea of Marmara. Bilecenoglu argues that our paper includes mistranslations of some previous research, misinterpretation and incomplete examination of certain published biodiversity data related to the Sea of Marmara (Bilecenoglu 2020). We answer his comments below.

RNA-seq analysis reveals divergent adaptive response to hyper- and hypo-salinity in cobia, Rachycentron canadum.

Salinity is an important abiotic stress that affects metabolic and physiological activities, breed, development, and growth of marine fish. Studies have shown that cobia (Rachycentron canadum), a euryhaline marine teleost fish, possesses the ability of rapid and effective hyper/hypo iono- and osmoregulation. However, genomic studies on this species are lacking and it has not been studied at the transcriptome level to identify the genes responsible for salinity regulation, which affects the understanding of the fundamental mechanism underlying adaptation to fluctuations in salinity. To describe the molecular response of cobia to different salinity levels, we used RNA-seq analysis to identify genes and biological processes involved in response to salinity changes. In the present study, 395,080,114 clean reads were generated and then assembled into 65,318 unigenes with an N50 size of 2758bp. There were 20,671 significantly differentially expressed genes (DEGs) including 8805 genes adapted to hypo-salinity and 11,866 genes adapted to hyper-salinity. These DEGs were highly represented in steroid biosynthesis, unsaturated fatty acid metabolism, glutathione metabolism, energy metabolism, osmoregulation, and immune response. The candidate genes identified in cobia provide valuable information for studying the molecular mechanism of salinity adaptation in marine fish. Furthermore, the transcriptomic sequencing data acts not only as an important resource for the identification of novel genes but also for further investigations regarding cobia biology.

Dietary Saccharina japonica is a natural and effective tool to fortify marine teleost black sea bream fillets with iodine: effects on growth, flesh quality, and serum thyroid hormones

In the present study the effects of dietary Saccharina japonica on growth performance, flesh quality traits, and serum thyroid hormones (tetraiodothyronine (T4) and triiodothyronine (T3)) of juvenile black sea bream, Acanthopagrus schlegelii, were investigated. Seven diets containing graded levels of S. japonica (0, 0.1, 0.2, 1.2, 2.5, 5, and 10%) were formulated. Each diet was randomly assigned to sex replicate groups of 40 fish. After a 90-day feeding trial, the best growth performance was achieved in fish fed with the 2.5% S. japonica diet, with significantly higher weight gain rate (WGR) and lower feed coefficient (FC) than those fed with the other diets (P 0.05) on proximate composition of the whole body and the muscle. However, the content of n-6PUFA, n-3PUFA, and LC-PUFA in the muscle was significantly increased with the increasing level of dietary S. japonica. No differences in the flesh texture, cooked meat rate and water holding capacity were found among fish fed with different diets. It was further demonstrated that dietary S. japonica significantly fortify fillets with iodine (from 0.11 to 1.05 mg kg−1DM) and increased serum T4 and T3 levels. These results showed that the inclusion of up to 2.5% of S. japonica meal in diets could be beneficial to aquaculture of juvenile black sea bream, while higher inclusion levels resulted in significantly smaller fish. Moreover, the content of flesh iodine content quintupled in fish fed 2.5% up to 2.5%, confirming S. japonica as a natural and effective tool to increase the nutritional value of juvenile black sea bream.

Tissue distribution of transcription for 29 lipid metabolism-related genes in Takifugu rubripes, a marine teleost storing lipid predominantly in liver.

The tissue distribution pattern of lipid is highly diverse among different fish species. Tiger puffer has a special lipid storage pattern, storing lipid predominantly in liver. In order to better understand the lipid physiology in fish storing lipid in liver, the present study preliminarily investigated the tissue distribution of transcription for 29 lipid metabolism-related genes in tiger puffer, which are involved in lipogenesis, fatty acid oxidation, biosynthesis and hydrolysis of glycerides, lipid transport, and relevant transcription regulation. Samples of eight tissues, brain, eye, heart, spleen, liver, intestine, skin, and muscle, from fifteen juvenile tiger puffer were used in the qRT-PCR analysis. The intestine and brain had high transcription of lipogenic genes, whereas the liver and muscle had low expression levels. The intestine also had the highest transcription level of most apolipoproteins and lipid metabolism-related transcription factors. The transcription of fatty acid β-oxidation-related genes was low in the muscle. The peroxisomal fatty acid oxidation may dominate over mitochondrial β-oxidation in the liver and intestine of tiger puffer, and the MAG pathway probably predominates over the G3P pathway in re-acylation of absorbed lipids in the intestine. The intracellular glyceridases were highly transcribed in the brain, eye, and heart. In conclusion, in tiger puffer, the intestine could be a center of lipid metabolism whereas the liver is more likely a pure storage organ for lipid. The lipid metabolism in the muscle could also be inactive, possibly due to the very low level of intramuscular lipid.

Development and characterization of genomic resources for a non-model marine teleost, the red snapper (Lutjanus campechanus, Lutjanidae): Construction of a high-density linkage map, anchoring of genome contigs and comparative genomic analysis.

The red snapper Lutjanus campechanus is an exploited reef fish of major economic importance in the Gulf of Mexico region. Studies of genome wide genetic variation are needed to understand the structure of wild populations and develop breeding programs for aquaculture but interpretation of these genome scans is limited by the absence of reference genome. In this work, the first draft of a reference genome was developed and characterized for the red snapper. P-454 and Illumina sequencing were conducted to produce paired-end reads that were assembled into reference contigs and scaffolds. The current assembly spans over 770 Mb, representing an estimated 69% of the red snapper genome in 67,254 scaffolds (N50 = 16,803 bp). The genome contigs were applied to map double digest Restriction-Site Associated DNA Tags and characterize Single Nucleotide Polymorphisms (SNPs) in five outbred full-sib families. The identified SNPs and 97 microsatellite loci were used to generate a high-density linkage map that includes 7,420 markers distributed across 24 linkage groups and spans 1,346.64 cM with an average inter–marker distance of 0.18 cM. Sex-specific maps revealed a 1.10:1 female to male map length ratio. A total of 4,422 genome contigs (10.5% of the assembly) were anchored to the map and used in a comparative genomic analysis of the red snapper and two model teleosts. Red snapper showed a high degree of chromosome level syntenic conservation with both medaka and spotted green puffer and a near one to one correspondence between the 24 red snapper linkage groups and corresponding medaka chromosomes was observed. This work established the first draft of a reference genome for a lutjanid fish. The obtained genomic resources will serve as a framework for the interpretation of genome scans during studies of wild populations and captive breeding programs.