Atlantic bluefin tuna spawn early to avoid metabolic meltdown in larvae

To predict shifts in phenology and distribution of organisms we need to understand how survival through early life stages depends on environmental conditions. Here, we present a mechanistic model of development, feeding and bioenergetics of early life stages in bluefin tuna and predict the optimal time of the year for them to be born. We find that the availability of prey, particularly nauplii, is sufficient for fast growth in tuna larvae while temperature is moderate during midsummer, but not when temperatures increase later in summer. High temperatures benefit egg and yolk-sac stages, but the metabolic needs of feeding larvae are hard to sustain during the warmest periods. Heatwaves, such as the one in 2003, increase larval survival potential, but shorten the viable part of the season for the larvae. Atlantic bluefin tuna is a large, highly migratory marine top predator that spawns while temperatures are rising, but before the heat leads to a metabolic meltdown in larvae. This means that food resources modulate how temperature change shifts optimal phenology.En prensa

Date of otolith first increment formation in Baltic sprat Sprattus sprattus and its relation to onset of maturity

This study explores the date of first otolith increment formation in Baltic sprat Sprattus sprattus and relates the onset of maturity at Age 1 to the larval traits that are tied to the formation of the first increment. From the otolith microstructure analyses in larvae we found that regular deposition of increments is closely related to larval length, the first clear increment being identified at 16 mm length. Otolith distance from the centre to the first clear increment was independent of temperature, whereas the width of subsequent regular increments increased with increasing temperatures. These results are interpreted in the context of the interaction of larval length, somatic growth and environmental temperature. The date of first increment formation was further estimated in mature and immature Age 1 sprat caught from 1998 to 2000 using a technique that we developed, based on the effect of temperature on larval-stage otolith microstructure after first increment formation. The overall result was that larvae that reach the length of 16 mm early (late) in the season in warm years are more (less) likely to mature the following year. In cold years, like 1998, the probability of maturating at Age 1 was independent of the date at which larvae became 16 mm long, and other processes such as juvenile growth rates, feeding conditions and year-class abundance are suggested as factors that may influence the onset of maturity

Ephyrae and metaephyrae of Pelagia noctiluca: stage determination, morphometry and shrinkage

Understanding processes occurring in the different life stages of jellyfish is key to advance knowledge on their trophic interactions and population dynamics. We describe four developmental stages of Pelagia noctiluca ephyrae and metaephyrae based on the progress of feeding structures and morphometric measurements on the central disc diameter and total body diameter. Size differs significantly among stages, but it can overlap substantially, suggesting that it is not always coupled with development progress due to different somatic growth. Morphological distinction of stages is biologically important because it implies different levels of food specialization and capture efficiency. We further report a 25% (±13 SD) shrinkage of ephyrae and metaephyrae after storage in 4% formaldehyde solution. This metric can be used in ecological studies focusing on size-related traits of field observed individuals.Postprint1,74

Buoyancy of Atlantic bluefin tuna Thunnus thynnus eggs obtained from captive broodstock spontaneous spawning events

One way to alleviate the pressure on the wild fishery of the Atlantic bluefin tuna (BFT) and aid in its conservation could be its domestication and the development of a self-sustained industry to rear the larvae and produce fingerlings in captive conditions for further grow-out. The Spanish Institute of Oceanography (IEO) is carrying out several research projects on this target for the last 12 years. No one has yet measured the vertical distribution and the in situ buoyancy of bluefin tuna eggs in any of its spawning areas in the world (Mac Kenzie and Mariani, 2012). In the present study the density of bluefin tuna eggs has been measured, comparing it with those of other fish species, particularly Atlantic bonito. We have estimated the speed by which BFT eggs rise to the surface to get a better idea of the potential loss of spawned eggs dragged by the currents out of the cage

Effect of photoperiod and light intensity on larval rearing of bluefin tuna Thunnus thynnus

A couple of trials to test the effects of photoperiod and light intensity on growth and survival of Atlantic bluefin tuna larva were carried out. With regard to light intensity, no significant differences were found between 500, 1000 and 2000 luxes. With regards to photoperiod meanwhile long photoperiods lead to a greater growth, intermediate photoperiods (16hL:8hD and 12hL:12hD ) improve significantly survival rates.Research Project ATAME (CT M2011-29525-C04)

La proteína AOX como terapia génica para enfermedades mitocondriales

La proteína AOX como terapia génica para enfermedades mitocondriales. Las enfermedades mitocondriales constituyen un amplio grupo de patologías que se caracterizan por presentar alteraciones en la cadena de transporte de electrones, con la consiguiente disminución de la producción de energía en forma de ATP. El tratamiento de las enfermedades mitocondriales presenta una serie de dificultades y, de hecho, no existe una terapia efectiva para tratarlas. Actualmente, las medidas terapéuticas se limitan a ser de soporte en la gran mayoría de los pacientes. Una de las terapias que se está investigando en la actualidad consiste en la xenoexpresión de la oxidasa alternativa AOX, enzima procedente del hongo Emericella nidulans. En concreto, en el presente trabajo de fin de máster se ha continuado con la caracterización de dicha proteína, realizando ensayos de inmunodetección de AOX en distintos tejidos de ratón knock-in, y ensayos de viabilidad para estudiar la funcionalidad de la proteína. Los ensayos de inmunodetección revelaron que AOX se expresa en todos los tejidos de ratón analizados y que su expresión es mayor en ratones machos. Sin embargo, no se pudo concluir el origen de las tres bandas correspondientes a AOX. Además, los ensayos de viabilidad demostraron que no ejerce ningún efecto cuando se produce un fallo en la cadena a nivel del complejo I, al contrario de lo que sucedía con los complejos III y IV, validando la relevancia funcional de dicha proteína

Otolith microstructure analyses in cultured Atlantic bluefin tuna larvae as a tool to provide accurate estimates of size selective growth and mortality

Being bigger is not always the best option to survive and mortality rates do not always decline with increasing larval size. Smaller size at a given age could under certain condition and at certain stages of development confer a survival advantage on individual members of a larval cohort. Reference

Size-selective mortality of laboratory-reared Atlantic bluefin tuna larvae: evidence from microstructure analysis of otoliths during the piscivorous phase

Atlantic bluefin tuna (Thunnus thynnus) larvae show strong piscivorous feeding behavior at the very early larval stage and this enables them to grow at high rates. We conducted a laboratory experiment in which Atlantic bluefin tuna larvae were offered larval prey for the first time at different ages to simulate the early onset of piscivory at three treatments: yolk-sac larvae (YSL), delayed onset of piscivory (DYSL) and a solely planktivorous diet (Rotifers). The otolith microstructure was then used to compare the larval size distribution at the onset of the experiment with the estimated previous size-at-age of the survivors at the end of the experiment by back- calculation. Within a cohort, our results show size-selective mortality of the largest larvae independent of the differences in the timing of onset of piscivory and differences in growth patterns. The results also corroborate the rapid response of Atlantic bluefin tuna to piscivory in terms of growth reflected in the otolith increment widths. Being bigger did not infer a survival advantage and mortality rates did not decline with increasing larval size. Smaller size at a given age could under certain conditions and stages of development confer a survival advantage of individual members of a larval cohort when suitable small-sized prey is available.Versión del editor2,26