Yolk Absorption, Yolk Sac Constrictions, Mortality, and Growth During First Feeding of Atlantic Salmon (<i>Salmo salar</i>) Incubated on Astro-turf

174

157

SUMMARY The size and structure of an animal's brain is typically assumed to result from either natural or artificial selection pressures over generations. However, because a fish's brain grows continuously throughout life, it may be particularly responsive to the environmental conditions the fish experiences during development. Salmon are an ideal model system for studying these effects because natural habitats differ significantly from the hatchery environments in which these fish are frequently reared. For example, in the wild, salmon alevins (i.e. yolk-sac fry) are buried in the gravel, while hatchery environments lack this structural component. We show that the simple manipulation of adding stones to a standard rearing tank can dramatically alter the growth of specific brain structures in steelhead salmon alevins(Oncorhynchus mykiss). We found that alevins reared with stones grew brains with significantly larger cerebella than genetically similar fish reared in conventional tanks. This shift to a larger cerebellar size was, in turn, accompanied by changes in locomotory behaviors - behaviors that correlate strongly to the function of this brain region. We next show that hatchery fish reared in a more naturalistic setting in the wild had significantly larger brains than their lab-reared counterparts. However,relative cerebellar volumes were similar between wild-reared alevins and those reared in the complex treatment in the laboratory. Together our results indicate that, within the first three weeks of life, variation in rearing environment can result in brain differences that are commonly attributed to generations of selection. These results highlight the need to consider enrichment strategies when designing captive rearing facilities for both conservation and laboratory use.

Section: Discussionmentioning

confidence: 38%

Section: Introductionmentioning

confidence: 99%

Early rearing environment impacts cerebellar growth in juvenile salmon

Kihslinger

Nevitt

2006

174

157

“…It is known that salmon spend much of their time hidden in gravel and are almost completely inactive before the yolk sac is depleted (Bams, 1967;Hansen and Moller, 1985). In this experiment salmon larvae incubated at high temperature continued to remain on the gravel after the yolk was depleted, whereas salmon larvae incubated at 5°C were more often seen Fig.·8.…”

Section: Discussionmentioning

confidence: 79%

Larval programming of post-hatch muscle growth and activity in Atlantic salmon (Salmo salar)

Albokhadaim

Hammond

Ashton

et al. 2007

SUMMARY Larval muscle development in Atlantic salmon is known to be affected by temperature; however, the long term effects and possible mechanisms involved are less well understood. Therefore, the aim of this study was to evaluate the influence of egg incubation temperature on post-hatch muscle growth and fish activity. Salmon eggs were incubated at either 10°C or 5°C from fertilization until hatching, then subsequently both groups were reared at 5°C. Fish from both groups were sampled at the eyed stage, 6 and 21 weeks after first feeding, for muscle cellularity analysis and immunocytochemistry. In addition,to try to establish a mechanism for altered growth, the activity of the fish was measured at 3, 6 and 21 weeks after first feeding. Our results demonstrate that whereas fish incubated at 10°C grow faster, the fish incubated at 5°C show a more sustained period of muscle growth and by 21 weeks are significantly longer, heavier and have more muscle fibres than those fish incubated at a higher temperature. We also demonstrate that fish raised at 5°C show increased food seeking activity throughout development and that this may explain their sustained growth and muscle development. These results taken together, demonstrate that egg incubation temperature up to hatching in salmon is critical for longer term muscle growth, twinned with increased activity. This is of interest to the aquaculture industry in term of the production of good quality fish protein.

“…In contrast, van der Meulen et al reported that muscle development was not grossly affected by decreased muscle activity in immobile zebrafish embryos (van der Meulen et al, 2005). Two studies reported that growth was actually improved in 'immobile' S. salar larvae, compared with 'mobile' larvae (Hansen and Møller, 1985;Peterson and Martin-Robichaud, 1995); however, movement was not quantified. Swim training in larval zebrafish (D. rerio) did not improve growth (Bagatto et al, 2001).…”

Section: Growthmentioning

confidence: 99%

Removal of the chorion before hatching results in increased movement and accelerated growth in rainbow trout (Oncorhynchus mykiss)embryos

Ninness

Stevens

Wright

2006

SUMMARY We investigated the effects of the chorion on movement and growth in rainbow trout (Oncorhynchus mykiss) embryos. To test if the chorion restricts movement and growth before hatching, we manually removed the chorion 3–6 days before the natural time of hatching (dechorionated) and compared movement, growth and oxygen consumption in dechorionated embryos and in embryos whose chorions remained intact until the time of hatching(chorionated). Dechorionated embryos exhibited 36 times more movement before hatching compared with intact embryos. By 10 h post-hatch there was no difference in the number of movements between the two groups. At the time of hatching [30 days post-fertilization (d.p.f.)], dechorionated embryos had a significantly greater embryonic body dry mass compared with chorionated embryos, which persisted up to 45 d.p.f. At first feeding (50 d.p.f.) there was no significant difference in embryonic body dry mass between the two groups. Dechorionated embryos had a significantly greater embryonic body protein content after hatching (32, 33 d.p.f.) compared with chorionated embryos. Despite the differences in movement and growth, there were no significant differences in oxygen consumption between chorionated and dechorionated embryos. Furthermore, there was no correlation between the number of movements and oxygen consumption in rainbow trout embryos(chorionated, dechorionated, and hatched). Taken together, the data indicate that rainbow trout embryos have the capacity to be relatively active before hatching, but that the chorion restricts or inhibits movement. Moreover,precocious activity in pre-hatch embryos is correlated with accelerated growth and higher protein content, suggesting that the exercise training effect observed in adult salmonids is also present in early developmental stages.