Respiration rates of herring larvae at different salinities and effects of previous environmental history

Metabolic rates of early life history stages of marine fishes show considerable inter-individual differences and are highly influenced by extrinsic factors like temperature or food availability. Measuring oxygen uptake rates is a proxy for estimating metabolic rates. Still, the relationship between respiration rates and ambient or previous salinity conditions as well as parental and developmental acclimation to changes in salinity is largely unexplored. In the present study, we conducted experiments to investigate salinity effects on the routine metabolic rates (RMR) of euryhaline Atlantic herring (Clupea harengus) larvae at three levels of salinity: low (6 psu), intermediate (16 psu) and high (35 psu) reflecting ecological relevant conditions for its populations in the Atlantic and Baltic Sea. The larvae originated from different genetic backgrounds and salinity adaptations to account for cross-generation effects on metabolic rates. Closed respirometry carried out over 24 h on individual fish larvae generally confirmed near isometric respiration rates at all salinity regimes, with rates being 15.4% higher at 6 psu and 7.5% higher at 35 psu compared to 16 psu conditions. However, transgenerational acclimation to different salinity regimes of parents had no effect on the salinity specific metabolic rates of their offspring. Our study demonstrates the ability of herring to cope with a wide range of salinity conditions, irrespective of parental environmental history and genetic origin. This phenotypic plasticity is considered to be one of the main contributing factors to the success of herring as a widely distributed fish species in the North Atlantic and adjacent waters.acceptedVersio

Experimental Radiosensitization and Molecular Prediction of Chemoradiotherapy Response in Rectal Cancer

In Norway, the annual incidence of rectal cancer exceeds 1000 cases. Although surgery remains the principal treatment modality in this common disease, recent studies have highlighted the central role of chemoradiotherapy (CRT) in conjunction with surgical resection to optimize local control and improve outcome. Nevertheless, in locally advanced rectal cancer (LARC), tumor response to preoperative CRT may vary considerably; in addition, this treatment delays surgery and has substantial acute and long-term adverse effects. Hence, in the contemporary management of LARC, the possibility of improving CRT efficacy and predicting CRT response to enable treatment stratification would be a critical achievement. The study aims were to evaluate new drugs for radiosensitizing efficacy in relevant preclinical models and to identify functional biomarkers predictive of tumor responsiveness to preoperative CRT in LARC. Oxaliplatin is a chemotherapeutic currently under investigation in CRT trials for rectal cancer. In an experimental in vivo model of human colorectal carcinoma, however, this drug did not convincingly improve the radiosensitizing effect of a standard CRT regimen, implying that integration of oxaliplatin into combined modality treatment of rectal cancer should remain controversial when conclusive clinical evidence is lacking. On the contrary, vorinostat, a histone deacetylases inhibitor, enhanced radiation response of experimental colorectal carcinoma models as evaluated by in vitro clonogenicity and in vivo tumor growth delay, suggesting that this class of therapeutics might be a supplement to current CRT strategies in rectal cancer. Finally, recognizing that kinase activity is a predictor of radiation response in tumor models, multiplex kinase activity profiles of diagnostic tumor biopsies from LARC patients were correlated with the individual tumor responses to preoperative CRT, and kinase pathways descriptive of poor-responding tumors were identified

Análisis del ciclo celular en células del cerebro como índice de crecimiento en larvas de bacalao a diferente condiciones de alimento y temperatura

The percentage of cells dividing in a specific tissue of individual larvae can be estimated by analyzing DNA per cell by flow cytometry. An experimental test was carried out with cod (Gadus morhua) larvae, with brain as the target tissue, to validate this technique as an appropriate growth index for larval fish. Standard length (SL), myotome height, and %S-phase (% of cells in the S-phase of the cell-division cycle) variability were analyzed, with temperature (6 and 10°C), food level (high- and no-food) and larval developmental stage (first feeding, pre-metamorphosis and post-metamorphosis) as independent factors. Cod larvae grew faster (in SL) and presented a higher %S-phase under high-food conditions. Larval SL increased with temperature in rearing and experimental tanks. However, there was a significant interaction between temperature and food in the %S-phase. There were no significant differences in the %S-phase between 6 and 10°C at high-food levels. We suggest that this result is a consequence of temperature-dependency of the duration of the cell cycle. In the absence of food, larvae at 10ºC had a lower %S-phase than larvae at 6°C, which may be related to increased metabolic costs with increasing temperature. Considering the effect of temperature, the mean % S-phase explained 74% of the variability in the estimated standard growth rate.El porcentaje de células en divisón en un determinado tejido de una larva de pez se puede estimar analizando la cantidad de ADN por célula mediante citometría de flujo. Se realizó un experimento con larvas de bacalao (Gadus morhua), analizando células de cerebro, para validar esta técnica como índice de crecimiento en larvas de peces. Se analizó la variabilidad de la longitud estándar (SL), la altura del tronco medida en el ano, y el %S (% de células en fase S del ciclo celular), con temperatura (6 y 10ºC), nivel de alimento (alto y sin alimento) y estado de desarrollo larvario (comienzo de la alimentación, pre-metamorfosis y post-metamorfosis) como factores independientes. Las larvas de bacalao crecieron más rápido (en SL) y presentaron mayor %S bajo condiciones de nivel alto de alimento. La SL larvaria incrementó con la temperatura. Sin embargo, se observó una interacción significativa entre temperatura y alimento sobre %S. No hubo diferencias significativas en %S entre 6 y 10ºC en condiciones de nivel alto de alimento. Sugerimos que este resultado es consecuencia de una termo-dependencia en la duración del ciclo celular. En ausencia de alimento, las larvas a 10ºC presentaron %S más bajos que las larvas a 6ºC, lo que puede estar relacionado con un incremento de los costes metabólicos a mayor temperatura. Considerando el efecto de la temperatura, el %S medio explicó el 74% de la variabilidad de la tasa de crecimiento específica estimada.

Development stage distribution as a proxy for feeding success and growth for first feeding Norwegian spring spawning herring larvae

The estimation of growth rates in young herring larvae (Clupea harengus) in the field can be difficult because the primary increments in the otoliths may not be discernible or formed at a daily level. Likewise, the estimation of mortality rates of fish larvae in the field is very difficult to achieve, especially in a rigorous quantitative manner. In this study, the authors suggest the use of a stage‐based proxy of feeding success, growth and potential survival or mortality risk of field‐caught larvae. The stage‐based proxy is derived based on observations from previous laboratory studies where larvae successfully completing start‐feeding on external food sources will advance through the early development stages, whereas those that do not (unsuccessful larvae) remain and accumulate in the development stage preceding first feeding. The relative occurrence of larvae in the early development stages is therefore expected to reflect feeding conditions of the larvae, with higher ratios of unsuccessful larvae indicative of poor feeding success and higher mortality risk. Using field data on Norwegian spring spawning herring, the authors document that the relative occurrence of larvae in the late non‐feeding stage is significantly higher at lower average zooplankton concentrations, in line with the predictions of the authors that this novel approach of using a stage‐based proxy could be a useful indication of feeding success, growth and mortality in the field. Further, there was a significant interaction effect with ambient temperature, with the ratio being higher at low zooplankton concentrations at higher temperatures. This study also suggests that these findings are not population specific as the same accumulation of non‐feeding larvae in the late non‐feeding stage was observed in laboratory‐reared larvae of both autumn and spring spawning herring populations.publishedVersio

Effects of temperature on tissue-diet isotopic spacing of nitrogen and carbon in otolith organic matter

Reconstruction of the trophic position of a fish can be performed by analysing stable nitrogen and carbon isotopes in otolith protein. However, ambient temperature may affect the tissue–diet isotopic spacing of stable isotopes from diet to predator tissue and bias estimates of trophic position. To test this, otolith protein, heart and muscle tissue from a rearing experiment with juvenile cod held at different temperatures (4, 7, 10 and 14°C) were analysed. There was no significant effect of temperature on otolith δ15N, whereas muscle and heart exhibited a slight decrease in δ15N values with increasing temperature corresponding to maximum of 0.6‰ over the 10°C range. By contrast, the otolith protein δ13C values at 4 and 7°C were significantly higher than for 10 and 14°C, suggesting an approximate 1‰ increased tissue–diet enrichment at the lower temperatures. Temperature had no significant effect on muscle and heart δ13C values. Considering the annual mean variation in ocean temperatures, our results indicate that the trophic signals recorded in the otoliths will reflect changes in diet isotope values with little bias from the ambient temperature experienced by the fish.publishedVersio

Hot issue markets and industry effect on IPO underpricing in Norway

In this dissertation, I use a dataset of Norwegian IPOs from 1993 to 2018 to investigate IPO underpricing. I find an average underpricing of 5.47%, this finding is statistically significant at the 1% level. This proves that there is underpricing present in the sample, and the underpricing percentage is a middle value compared to other studies on the Norwegian IPO market. I find evidence of industry and hot issue markets effect in my dataset. Industries help explain 1.01% of the underpricing in the Norwegian market, and 2.98% of the underpricing during hot issue markets. My findings suggest that issuers time their IPOs to coincide with favorable issue periods, this is consistent with the findings of Ibbotson and Jaffe (1975). This is in line with information asymmetry and behavioral explanations for IPO underpricing. However, these effects only explain a small part of the variance in IPO underpricing, therefore there is room for further research on this topic. Especially when it comes to the differences in explanatory variables in hot versus cold issue markets

Comparison of Otolith Microstructure of Herring Larvae and Sibling Adults Reared Under Identical Early Life Conditions

Atlantic herring (Clupea harengus) is a euryhaline species, occupying fully marine habitats (35 psu) in the North Atlantic, as well as brackish waters (<20 psu) such as in the adjacent Baltic Sea. We co-reared Atlantic purebreds and Atlantic/Baltic F1 hybrids in two salinity regimes (16 and 35 psu) in a common garden experiment for 3 years until their first maturity. This setup enabled for the first time a direct comparison between adults and their larval siblings at respective salinity regimes in terms of larval growth indicated by otolith microstructure. We validated that otolith microstructure analysis of adult otoliths is reflecting the experienced otolith growth during the larval stage. No major selection in terms of otolith growth had taken place during the juvenile stage, except for one experimental group. Surviving adult Atlantic purebreds reared at 16 psu had higher otolith growth compared to their larval stages. The validation that otolith microstructure analyses of adult herring can reliably be extracted and used to examine larval growth even after several years adds strong support for further use of such analyses. Among the parental generation, Baltic herring had a faster initial otolith growth than Atlantic herring. The growth of their laboratory-reared F1 progeny was intermediate compared to their parents. In general, larval growth of both Atlantic purebreds and Atlantic/Baltic hybrids reared in 16 psu was significantly larger than for those herring reared at 35 psu. There was no significant difference in larval growth between Atlantic purebreds and Atlantic/Baltic hybrids reared at 35 psu, but hybrid larval growth was significantly higher compared to larval growth of Atlantic purebreds at 16 psu. This was not reflected at the adult stage where purebreds were ultimately larger than hybrids (Berg et al., 2018). This indicates the influence and importance of environmental and genetic factors throughout the life of Atlantic herring, along with genetic contributions to phenotypic variability.publishedVersio