Helge Tveiten

• NOFIMA Norwegian Institute of Food, Fisheries and Aquaculture Research

We tested the photothermal effects on sexual maturation in the broodstock of lumpfish (Cyclopterus lumpus) using short-to-continuous (LDL) and continuous (LL) photoperiods for 24 weeks, with temperature elevation during final maturation in females. The LDL regime advanced and synchronized sexual maturation, while an elevation of temperature enhance...

A successful control of sexual maturation is crucial for year-round production of lumpfish juveniles destined as cleaner fish in Atlantic salmon aquaculture. This study investigated the combined effects of photoperiod and temperature manipulations on sexual maturation and spawning in lumpfish females. Lumpfish juveniles were exposed to simulated na...

Egg quality in fishes is commonly determined by fertilisation success and cleavage patterns as a phenotypic outcome of underlying regulatory mechanisms. Although these phenotypic estimators of egg quality are useful in farming conditions, these “good quality” egg batches do not always translate to good larval growth and survival. The identification...

Stress during early life has potential to program and alter the response to stressful events and metabolism in later life. Repeated short exposure of Atlantic salmon to cold water and air during embryonic (E), post-hatch (PH) or both phases of development (EPH) has been shown to alter the methylome and transcriptome and to affect growth performance...

Mean lengths of newly hatched cod larvae from egg incubation at 4 °C (Low-L) and 9.5 °C (High-H) were similar, and only minor differences were observed in larval histomorphology. However, growth performance of larvae reared at 4 °C (T1-LL) and 9.5 °C (T2-LH) from the 4 °C egg incubation and 4 °C (T3-HL) and 9.5 °C (T4-HH) from the 9.5 °C incubation...

This study provides new and practical information to implement the use of photoperiodic manipulation for the control of the sexual maturation of Canadian 6⁺ Atlantic wolffish (Anarhichas lupus) and 3⁺ first-time spawners spotted wolffish (Anarhichas minor) from Canadian and Norwegian populations. Wolffish reproductive cycle (gametogenesis and oocyt...

Sexual size dimorphism (SSD) in wolffishes has never been unquestionably reported in previous fisheries or aquaculture studies. The sex-related growth patterns of 6+Anarhichas lupus and 3+A. minor (Norway (NW) and Québec (QC) populations) were monitored in replicates in a controlled environment over two successive spawning seasons (21 months). Over...

Egg yolk proteins are mainly derived from vitellogenin (Vtg), and serve as essential nutrients during early development in oviparous organisms. Vertebrate Vtgs are predominantly synthesized in the liver of maturing females, and are internalized by the oocyte after binding to specific surface receptors (VtgR). Here we clarify the evolutionary histor...

Exposure to environmental stressors during early-life stages can change the rate and timing of various developmental processes. Epigenetic marks affecting transcriptional regulation can be altered by such environmental stimuli. To assess how stress might affect the methylome and transcriptome in salmon, fish were treated using cold-shock and air-ex...

The delivery of exogenous biomolecules into teleost eggs is currently mostly relying on the manual microinjection methods, which, due to their high costs and low throughput, are not economically feasible for large-scale aquaculture applications. The main objective of this study was to develop a convenient, simple immersion delivery model for unfert...

Background The primordial germ cells (PGCs) giving rise to gametes are determined by two different mechanisms in vertebrates. While the germ cell fate in mammals and salamanders is induced by zygotic signals, maternally delivered germ cell determinants specify the PGCs in birds, frogs and teleost fish. Assembly of the germ plasm in the oocyte is or...

Estradiol (E2) can bind to nuclear estrogen receptors (ESR) or membrane estrogen receptors (GPER). While mammals possess two nuclear ESRs and one membrane GPER, the European eel, like most other teleosts, has three nuclear ESRs and two membrane GPERs, as the result of a teleost specific genome duplication. In the current study, the expression of th...

Farmed female eels were fed two experimental diets with similar proximate composition but different n-3 polyunsaturated fatty acid (PUFA) levels. Both diets had similar levels of arachidonic acid (ARA), while levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in one diet were approximately 4.5 and 2.6 times higher compared to the...

This study evaluates the effects of temperature on hCG-induced spermatogenesis in European eel (Anguilla anguilla), subjected to three thermal regimes: T10: 10°C (first 4weeks), 15°C (next 3weeks) and 20°C (last 6weeks); T15: 15°C (first 4weeks) and 20°C (last 9weeks); and T20: constant 20°C for the duration of the experiment. At 10°C, maturation s...

Interpretation of plasma cortisol levels in wild-caught fish is confounded by the stress of capture. Measurement of cortisol metabolites in fish bile could provide a method for assessing the stress level of wild fish because the time-lag for metabolism, conjugation and excretion into bile avoids the effects of sampling stress. To determine which bi...

Physiological indicators such as lipid peroxidation and enzymes involved in aerobic/anaerobic energy metabo-lism were measured in pure and hybrid lines of wolffish juveniles (Anarhichas minor, ♀ A. minor ! ♂ A. lupus). Inter-specific hybridization was introduced as a powerful tool to promote augmentation of phenotypic variability and conse-quently...

The importance of the aquaculture production is increasing with the declining global fish stocks, but early sexual maturation in several farmed species reduces muscle growth and quality, and escapees could have a negative impact on wild populations. A possible solution to these problems is the production of sterile fish by ablation of the embryonic...

The factors of the Sox9-Amh-Cyp19a1 cascade play a crucial role in the complex process of sex differentiation in mammals. The involvement of Sox9 and Cyp19a1 paralogs and the single Amh ortholog in sex differentiation and development of the gonads and the brain in Atlantic cod was examined by analyzing bimodal and sex-dimorphic gene expression patt...

We carried out an experiment to determine how rapidly the early incubation temperature of Atlantic cod eggs can be increased without affecting normal embryonic development and hatching. Atlantic cod eggs were incubated at a constant low temperature (4.5 ± 0.5°C; T5 – control) and four temperature increment treatments where the temperatures were inc...

The RNA binding protein Dead end (DnD) is essential for maintaining viable germ cells in vertebrates and silencing of the gene has been demonstrated to cause sterility in several mammalian and fish species. Here we investigated transcriptome changes in hatched larvae of Atlantic cod induced by DnD knockdown using morpholino oligonucleotides (MO) in...

The aim of the present study was to investigate the validity of measuring circulatory lactate levels in plasma from Atlantic cod using Lactate Pro TM , a portable meter described for measuring whole blood lactate in this species. Atlantic cod were either unstressed or subjected to short-or long-term crowding stress. Whole blood was analyzed on site...

Atlantic cod Gadus morhua ovaries were incubated in vitro with tritiated 17-hydroxypregn-4-ene-3,20-dione (17-P) to determine whether 17,20beta-dihydroxypregn-4-en-3-one (17,20beta-P) or 17,20beta, 21-trihydroxypregn-4-en-3-one (17,20beta,21-P), or both, were more likely to be the steroid responsible for inducing oocyte final maturation (i.e. resum...

Groups of mature (5+ year old) Arctic charr Salvelinus alpinus held in sea water were exposed for 34 days to either a high (mean ±s.e. 0·15 ± 0·01 sea lice Lepeophtheirus salmonis g−1 fish mass) (HI), medium (0·07 ± 0·00 sea lice g−1 fish mass) (MI) or no [control (C)] sea-lice infection during early stages of gonad development (June to July). Infe...

This book contains 27 chapters on finfish aquaculture. The chapters were designated into four main topics: I. Aquaculture diversification an introduction (contains the first seven chapters namely: fish culture: achievements and challenges, fish culture: the rearing environment, fish culture: feeds and feeding, farmed species and their characteristi...

European eel males can be artificially matured (1.5 IU hCG/g fish), but the regulatory mechanisms of their reproductive development are practically unknown. Spermatogenic stages (S1–S6), biometric characters [eye index (EI), gonadosomatic index (GSI), hepatosomatic index (HSI)] and sperm quality parameters (motility, viability and head spermatozoa...

The immune system in teleosts is not completely developed during embryonic and larval stages and immune competence is assumed to be restricted. This study is the first to address whether immune transcripts are maternally transferred to offspring and when immune genes are transcriptionally active in Atlantic cod (Gadus morhua). In unfertilised eggs,...

This is the first report of early-life developmental characteristics (coloration pattern, growth and survival) and genetic identification of the wolffish interspecific hybrid between Anarhichas minor and A. lupus, both endangered species in Canadian coastal water and of interest for cold-water aquaculture diversification. A first growth trial at 8...

Sperm production and characteristics of male spotted wolffish (Anarhichas minor) treated with cortisol, 11-KT, or a combination of both steroids, were compared with sham treated controls. Cortisol treatment significantly reduced proportions of sperm producing males and tended to reduce seminal fluid pH. 11-KT significantly increased proportions of...

The catabolic and energy metabolism capacities during spotted wolffish (Anarhichas minor) embryogenesis were investigated. We assessed the embryo's ability to catabolize proteins (trypsin-like proteases) and lipids (triglyceride lipase) and examined the development of metabolic capacities using enzymatic assays: ability to use carbohydrates (pyruva...

This study contributes to the identification of an adequate cryopreservation medium for wolffishes sperm (Anarhichas minor and A. lupus). Our results also confirm the presence of antifreeze proteins in the seminal fluid of the Atlantic wolffish (Anarhichas lupus) that could facilitate the process of cryoconservation in association with increased po...

Sperm competition models predict that males typically mating in disfavoured roles should be selected to compensate for their disadvantage by investing more into sperm. We studied the effect of rapid changes in social status on ejaculate investments during experimental trials with an externally fertilizing teleost--the Arctic charr (Salvelinus alpin...

Unlike the sperm of most teleosts, that of the spotted wolffish Anarhichas minor is motile on stripping, remains motile for at least 2 days and loses motility when exposed to sea water. Computer assisted sperm analysis (CASA) was used to quantitatively examine the motility characteristics of spotted wolffish sperm. Straight line velocity (VSL), bea...

Mature common wolffish, Anarhichas lupus L., previously held at 8°C for several months, were exposed to 4, 8 or 12°C throughout the breeding season (November-January). Regardless of temperature, some females ovulated in early-November, but thereafter ovulation was delayed in the 8 and 12°C groups compared with the 4°C group. Temperature experienced...

Temporal changes in feeding and growth of immature (1 +), maturing male (1 +), and mature male and female (3+) Arctic charr were studied by monitoring feed intake and growth of individually-marked fish for over 1 year. The fish were held at a constant temperature (4°C) under conditions of liberal feed supply. Feed intake and growth remained low in...

Temperature treatment of common wolffish Anarhichas lupus during vitellogenesis affected the time of final maturation; ovulation in fish held at 8 and 12° C from mid-April to October was about four and five weeks delayed, compared with a 4° C group. Fish in the 8° C group had significantly larger eggs than those in the 4° C and the 12° C groups, an...

Four groups of Arctic charr (age 3+), previously exposed to natural photoperiod, were subjected to different photoperiod regimes from February 20: Simulated natural photoperiod (SNP; Tromsø 70°N), continuous light (LD 24:0) followed by short day (LD 6:18) from either May 1 (LFeb–May) or June 25 (LFeb–June), or continuous light (LD 24:0) throughout...

Proportions of maturing fish and reproductive output [egg size, relative fecundity, spermatocrit and gonado-somatic index (IG)] were studied in repeat-spawning (+4 year old) male and female Arctic charr Salvelinus alpinus, subjected to periods of fasting. Groups of individually tagged Arctic charr were fasted for c. 3, 6, 7 and 9 months, from Novem...

The changes in egg lipids and fatty acid compositions that occur during embryonic development of spotted wolf-fish, Anarhichas minor, were examined by monitoring individual egg batches from the time of spawning (egg stripping) until hatching. The lipids, present as 3.7±0.1% of the wet mass of the freshly stripped eggs, contained high percentages of...

Incubation of follicular cells from postvitellogenic spotted wolffish ovaries with tritiated steroid precursors revealed that granulosa cells were able to convert 17-hydroxyprogesterone (17-P) to 17,20ß-dihydroxy-4-pregnen-3-one (17,20ß-P) and androstenedione. Theca cells had limited ability to synthesise additional steroids from 17-P but converted...

Temperature treatment during ovarian recrudescence influenced temporal changes in plasma testosterone (T) and oestradiol-17β (E2). In fish exposed to 8 and 12° C early in the cycle the peaks of both T and E2 were delayed by 4 weeks in comparison with those of fish held at 4° C throughout the experiment. These differences were accompanied by corresp...

Plasma concentrations of steroids during the periovulatory period were measured in female common wolffish reared at three different temperatures. Steroids were quantified by radioimmunoassay (RIA). Two "broad-spectrum specificity" RIAs-one which detects C21-steroids with a 17,20beta-dihydroxyl configuration (17,20beta-steroids) and the other which...

Vitellogenin (Vtg) was isolated from plasma of estradiol-17β-treated Arctic charr males by double precipitation with MgCl2-EDTA and distilled water, followed by ion-exchange chromatography. The monomeric form of Vtg, as revealed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was 158 kDa. The purified Vtg was used to raise a polyclona...

Changes in plasma concentrations of sex steroids, growth rate and condition of repeat spawning (3+) male and female Arctic charr were studied throughout an annual reproductive cycle. Individually marked fish (mean weight approx. 500 g) were held under conditions of liberal food supply, constant temperature (4° C) and simulated natural photoperiod (...

There has been interest in farming Arctic charr, Salvelinus alpinus, since the 1970s, but expansion of the industry has not been as rapid as originally predicted due to problems experienced with obtaining supplies of viable eggs and juveniles, variable growth and flesh pigmentation during grow-out, problems with year-round culture in sea water, ear...