Thermal reaction norms in sperm performance of Atlantic cod (Gadus morhua)

13 páginas, 6 figuras, 2 tablas[EN] Phenotypic plasticity occurs when a genotype produces variable phenotypes under different environments; the shapes of such responses are known as norms of reaction. The genetic scale at which reaction norms can be determined is restricted by the experimental unit that can be exposed to variable environments. This has limited their description beyond the family level in higher organisms, thus hindering our understanding of differences in plasticity at the scale of the individual. Using a three-year common-garden experiment, we quantify reaction norms in sperm performance of individual genotypes within different families of Atlantic cod (Gadus morhua). Cod sperm showed phenotypic plasticity in swimming performance across temperatures (3, 6, 11, and 21 °C), but the pattern of the response depended upon how long sperm had been swimming (30, 60, 120, or 180 s), i.e., plasticity in plasticity. Sperm generally swam fastest at intermediate temperatures when first assessed at 30 s after activation. However, a significant genotype × environment interaction was present, indicating inter-individual differences in phenotypic plasticity. To our knowledge, this is the first study to describe variable sperm performance across environmental conditions as a reaction norm. The results have potential theoretical, conservation, and aquaculture implications[FR] Il se produit une plasticité phénotypique lorsqu’un génotype détermine des phénotypes qui varient en fonction des différents environnements; les formes de telles réactions sont connues sous le nom de normes de réaction. L’échelle génétique à laquelle les normes de réaction peuvent être déterminées est restreinte par l’unité expérimentale qui peut être exposée à des environnements variables. Cela a limité leur description au-delà du niveau de la famille chez les organismes supérieurs, ce qui a entravé notre compréhension des différences de plasticité à l’échelle des individus. Dans une expérience de trois ans en jardin commun, nous avons mesuré les normes de réaction dans la performance des spermatozoïdes de génotypes individuels dans différentes familles de morues franches (Gadus morhua) de l’Atlantique. Les spermatozoïdes de morues font montre de plasticité phénotypique dans leur performance de nage sur une gamme de températures (3, 6, 11, et 21 8C), mais le patron de la réaction dépend du temps que le spermatozoïde a déjà consacré à la nage (30, 60, 120, ou 180 s), c’est donc une plasticité dans la plasticité. Les spermatozoïdes nagent généralement le plus vite aux températures intermédiaires lorsqu’ils sont évalués 30 s après leur activation. Cependant, il existe une interaction significative génotype environnement, ce qui indique qu’il y a des différences de plasticité phénotypique entre les individus. À notre connaissance, notre étude est la premiére à décrire une performance variable des spermatozoïdes comme des normes de réaction sur une gamme de conditions du milieu. Nos résultats ont des incidences théoriques potentielles, mais aussi des conséquences sur la conservation et l’aquacultureFunding was provided by a faculty startup award from Memorial University of Newfoundland to C.F.P., the Atlantic Cod Genomics and Broodstock Development Program and the Fisheries and Oceans Canada Aquaculture Collaborative Research Development Program to E.A.T., a scholarship from the Natural Sciences and Engineering Research Council of Canada to I.A.E.B, and a grant from Xunta de Galicia, inside de INCITE program, to A.A.- F. All animals were handled according to guidelines set by the Canadian Council on Animal CarePeer reviewe

Impact of crude oil and the dispersant CorexitTM EC9500A on capelin (Mallotus villosus) embryo development

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Frequency-dependent viscosity of salmon ovarian fluid has biophysical implications for sperm–egg interactions

Gamete-level sexual selection of externally fertilising species is usually achieved by modifying sperm behaviour with mechanisms that alter the chemical environment in which gametes perform. In fish, this can be accomplished through the ovarian fluid, a substance released with the eggs at spawning. While the biochemical effects of ovarian fluid in relation to sperm energetics have been investigated, the influence of the physical environment in which sperm compete remains poorly explored. Our objective was therefore to gain insights on the physical structure of this fluid and potential impacts on reproduction. Using soft-matter physics approaches of steady-state and oscillatory viscosity measurements, we subjected wild Atlantic salmon ovarian fluids to variable shear stresses and frequencies resembling those exerted by sperm swimming through the fluid near eggs. We show that this fluid, which in its relaxed state is a gel-like substance, displays a non-Newtonian viscoelastic and shear-thinning profile, where the viscosity decreases with increasing shear rates. We concurrently find that this fluid obeys the Cox–Merz rule below 7.6 Hz and infringes it above this level, thus indicating a shear-thickening phase where viscosity increases provided it is probed gently enough. This suggests the presence of a unique frequency-dependent structural network with relevant implications for sperm energetics and fertilisation dynamics

First Report of Dealfish, Trachipterus arcticus (lampriformes: Trachipteridae), from Canadian Waters

In November 2014, a recently dead specimen of the meso-pelagic Dealfish, Trachipterus arcticus, was found on a fjord beach in northern Newfoundland. This represents the first record of the species in Canadian waters

Inter-population differences in growth and energy allocation of northwest Atlantic cod (Gadus morhua L.) revealed by common environment experiments

Geographic variation in life history traits is frequently observed among fishes. Although much of this variation has been shown to be based on environmental variability, genetic differences among populations have been found Atlantic cod (Gadus morhua L) occur throughout much of the north Atlantic Ocean. Factors such as growth rates vary tremendously among stocks, generally with faster growth occurring in warmer water. The relative contributions of temperature and genotype towards growth in cod however, is not known. Knowledge of this information could be useful in the management of cod stocks and in selecting populations for aquaculture. -- This thesis examined growth and energy allocation of cod from different populations, using common environment experiments. In the first experiment, larval cod from the Grand Banks (GB), and the Gulf of Maine (GOM) were reared under identical laboratory conditions to determine the effect of two temperatures on growth. Grand Banks larvae grew faster than GOM larvae at both temperatures tested. This supports the countergradient variation hypothesis, which states that higher latitude populations have greater capacities for growth rates than those at lower latitudes. -- The second and third experiments compared the effects of temperature on growth and energy allocation in juvenile cod from the GB and GOM, and juveniles from two inshore bays on the island of Newfoundland. Temperature significantly affected growth rates, food conversion efficiency, and % liver water content, but did not significantly affect condition factor, hepatosomatic index, or % muscle water content In contrast to larvae, no differences in growth rates were observed between juvenile GB-GOM cod, or between juveniles from the two inshore sites. This rejects the countergradient variation hypothesis in juvenile cod However, population differences in other traits (food conversion efficiencies, energy allocation) were found, suggesting genetic differences between the stocks

Can cryptic female choice prevent invasive hybridization in external fertilizing fish?

Abstract Polyandrous mating systems result in females mating with multiple males, generating opportunities for strong pre‐mating and post‐mating sexual selection. Polyandry also creates the potential for unintended matings and subsequent sperm competition with hybridizing species. Cryptic female choice allows females to bias paternity towards preferred males under sperm competition and may include conspecific sperm preference when under hybridization risk. The potential for hybridization becomes particularly important in context of invasive species that can novelly hybridize with natives, and by definition, have evolved allopatrically. We provide the first examination of conspecific sperm preference in a system of three species with the potential to hybridize: North American native Atlantic salmon (Salmo salar) and brook char (Salvelinus fontinalis), and invasive brown trout (Salmo trutta) from Europe. Using naturalized populations on the island of Newfoundland, we measured changes in sperm swimming performance, a known predictor of paternity, to determine the degree of modification in sperm swimming to female cues related to conspecific sperm preference. Compared to water alone, female ovarian fluid in general had a pronounced effect and changed sperm motility (by a mean of 53%) and swimming velocity (mean 30%), but not linearity (mean 6%). However, patterns in the degree of modification suggest there is no conspecific sperm preference in the North American populations. Furthermore, female cues from both native species tended to boost the sperm of invasive males more than their own. We conclude that cryptic female choice via ovarian fluid mediated sperm swimming modification is too weak in this system to prevent invasive hybridization and is likely insufficient to promote or maintain reproductive isolation between the native North American species

A synthesis of senescence predictions for indeterminate growth, and support from multiple tests in wild lake trout

Senescence—the deterioration of functionality with age—varies widely across taxa in pattern and rate. Insights into why and how this variation occurs are hindered by the predominance of laboratory-focused research on short-lived model species with determinate growth. We synthesize evolutionary theories of senescence, highlight key information gaps and clarify predictions for species with low mortality and variable degrees of indeterminate growth. Lake trout are an ideal species to evaluate predictions in the wild. We monitored individual males from two populations (1976–2017) longitudinally for changes in adult mortality (actuarial senescence) and body condition (proxy for energy balance). A cross-sectional approach (2017) compared young (ages 4–10 years) and old (18–37 years) adults for (i) phenotypic performance in body condition, and semen quality—which is related to fertility under sperm competition (reproductive senescence)—and (ii) relative telomere length (potential proxy for cellular senescence). Adult growth in these particular populations is constrained by a simplified foodweb, and our data support predictions of negligible senescence when maximum size is only slightly larger than maturation size. Negative senescence (aka reverse senescence) may occur in other lake trout populations where diet shifts allow maximum sizes to greatly exceed maturation size

Mortality of Atlantic salmon after catch and release angling: assessment of a recreational Atlantic salmon fishery in a changing climate

Human activities have the potential to accelerate population-level decline by contributing to climate warming and decreasing the capacity of species to survive warming temperatures. Here we build a predictive model to test interactions between river warming and catch and release mortality in recreational fisheries for Atlantic salmon (Salmo salar) by compiling and analyzing published data. We then test whether warming has occurred in rivers where angling occurs and whether angling opportunities have been restricted through increased river closures due to high water temperatures. We find that catch and release mortalities are low (<0.05) at cool river temperatures (<12 °C). At river temperatures often leading to fishery closures (between 18 and 20 °C), mortalities range from 0.07 to 0.33 (mean = 0.16). River temperatures on the east and southeast coasts of Newfoundland have warmed, leading to an increase in fishery closures in recent years. By contrast, river temperatures in southern Labrador have warmed slightly, with only one documented river closure. Accordingly, increasing temperatures will increase the frequency of river closures and likely result in higher mortality in caught and released Atlantic salmon in rivers that remain open to catch and release angling at warm water temperatures.publishedVersio