Anne R. Kapuscinski

Demographic and genetic estimates of effective population size (Ne) reveals genetic compensation in steelhead trout

Estimates of effective population size (Ne) are required to predict the impacts of genetic drift and inbreeding on the evolutionary dynamics of populations. How the ratio of Ne to the number of sexually mature adults (N) varies in natural vertebrate populations has not been addressed. We examined the sensitivity of Ne/N to fluctuations of N and determined the major variables responsible for changing the ratio over a period of 17 years in a population of steelhead trout (Oncorhynchus mykiss) from Washington State. Demographic and genetic methods were used to estimate Ne. Genetic estimates of Ne were gained via temporal and linkage disequilibrium methods using data from eight microsatellite loci. DNA for genetic analysis was amplified from archived smolt scales. The Ne/N from 1977 to 1994, estimated using the temporal method, was 0.73 and the comprehensive demographic estimate of Ne/N over the same time period was 0.53. Demographic estimates of Ne indicated that variance in reproductive success had the most substantial impact on reducing Ne in this population, followed by fluctuations in population size. We found increased Ne/N ratios at low N, which we identified as genetic compensation. Combining the information from the demographic and genetic methods of estimating Ne allowed us to determine that a reduction in variance in reproductive success must be responsible for this compensation effect. Understanding genetic compensation in natural populations will be valuable for predicting the effects of changes in N (i.e. periods of high population density and bottlenecks) on the fitness and genetic variation of natural populations.

Notes: Microsatellite DNA Markers Reveal New Levels of Genetic Variation in Northern Pike

Abstract Using single-locus microsatellite markers, we have resolved higher levels of genetic variation than previously reported for northern pike Esox lucius. We isolated 14 (AC) n ·(TG) n microsatellite loci from a genomic library of northern pike. Primer pairs for the polymerase chain reaction (PCR) were developed for nine of these loci. With PCR, a DNA-amplifying technique, we were able to assess genetic variability using fish scales as our source of DNA. In four populations, we found four polymorphic loci with three or four alleles at each locus. Average heterozygosity at all loci was 0.075. Although this level of genetic variability is the highest reported for this species, it is much lower than that found for many other fish species by using microsatellite markers. Small numbers of founder fish, combined with loss of variation due to genetic drift in the small populations typical of northern pike, may explain the relatively low levels of genetic variation we found.

Isolation and characterization of β-act in gene of carp (Cyprinus carpio)

A beta-actin gene of carp (Cyprinus carpio) was isolated from a genomic EMBL3 library. The nucleotide sequence of the gene indicates six exons spanning 3.6 kb. Southern blot hybridization of restriction endonuclease digests of carp genomic DNA indicate that there are two copies of the beta-actin isotype and several other species of actin genes. The transcriptional start site is 85 bp and 24 bp downstream respectively from consensus CCAAT and TATA promoter elements. The organization of the carp beta-actin gene is identical to that of chicken, human, and rat genes in terms of size, exon/intron locations and junctions and in having a translationally silent first exon. The fish gene is 90% and 99% conserved at the nucleotide and amino acid levels, respectively, with land vertebrate beta-actin genes. Northern blot analysis of beta-actin gene expression indicated that the gene is highly expressed in brain, less so in muscle, and much less so in liver cells. The putative beta-actin proximal promoter of carp, identified by the conservation of known actin regulatory sequences, is transcriptionally active in both mammalian and piscine cells.

Transgenic fish and public policy: anticipating environmental impacts of transgenic fish.

Abstract Transfer of novel genes into fishes introduces a number of contentious issues into public policy debate among fisheries scientists and regulatory authorities. In the context of the technical status of development of transgenic strains of fishes, we discuss anticipated ecological impacts of releasing such fishes into natural environments. The major determinant of ecological impacts of transgenic fishes will be the phenotypic effect of the inserted genes. Three conceptual classes of phenotypic changes are anticipated, including changes in physiological rates, behavior, or tolerance of physical factors. The complex interactions among organisms and abiotic resources in aquatic communities suggest that it will be very difficult to predict ecosystem impacts of transgenic fishes. Based on current understanding of community-level impacts of stocking non-transgenic piscivorous fish, the release of certain transgenic fishes, particularly those exhibiting substantially altered performance, could destabilize...

Endocrine and gonadal changes during the annual reproductive cycle of the freshwater teleost,Stizostedion vitreum.

The annual reproductive cycle of walleye (Stizostedion vitreum) was characterized by documenting changes in gonadal development and serum levels of estradiol-17β (E2), testosterone (T), 17α,20β-dihydroxy-4-pregnen-3-one (17,20-P), and 11-ketotestosterone (11-KT) in wild fish captured from upper midwestern lakes and rivers throughout the year. Fish from the populations used in this study spawn annually in early- to mid-April. Walleye showed group synchronous ovarian development with exogenous vitellogenesis beginning in autumn. Oocyte diameters increased rapidly from ∼ 200 μm in October to ∼ 1,000 μm in November, and reached a maximum of 1,500 μm just prior to spawning. Changes in gonadosomatic indices (GSIs) paralleled changes in oocyte diameters. Serum E2 levels in females increased rapidly from low values in October (< 0.1 ng ml−1) to peak levels of 3.7 ng ml−1 in November, coinciding with the period of the most rapid ovarian growth. Subsequently, E2 levels decreased from December through spawning. Serum T levels exhibited a bimodal pattern, increasing to 1.6 ng ml−1 in November, and peaking again at 3.3 ng ml−1 just prior to spawning. We detected 11-KT in the serum of some females at concentrations up to 5.6 ng ml−1, but no seasonal pattern was apparent. In this study (unlike our results in a related study) 17,20-P was not detected. In males, differentiation of spermatogonia began in late August, and by January the testes were filled (> 95% of germ cells) with spermatozoa. Mature spermatozoa could be expressed from males from January through April. GSIs ranged from 0.2% (post-spawn) to 3.2% (pre-spawn). Serum T levels rose from undetectable levels in post-spawn males to 1.6 ng ml−1 by November, remained elevated throughout the winter, and peaked at 2.8 ng ml−1 I prior to spawning. Levels of 11-KT in males remained low (< 10 ng ml−1, from post-spawning through January, then increased significantly by March and peaked just prior to spawning at 39.7 ng ml−1. Our results indicate that vitellogenesis and spermatogenesis are complete or nearly so, in walleye by early winter, and suggest that it may be possible to induce spawning in this species several months prior to the normal spawning season by subjecting fish to relatively simple environmental and hormonal treatments.

Lower fitness of hatchery and hybrid rainbow trout compared to naturalized populations in Lake Superior tributaries.

We have documented an early life survival advantage by naturalized populations of anadromous rainbow trout Oncorhynchus mykiss over a more recently introduced hatchery population and outbreeding depression resulting from interbreeding between the two strains. We tested the hypothesis that offspring of naturalized and hatchery trout, and reciprocal hybrid crosses, survive equally from fry to age 1+ in isolated reaches of Lake Superior tributary streams in Minnesota. Over the first summer, offspring of naturalized females had significantly greater survival than offspring of hatchery females in three of four comparisons (two streams and 2 years of stocking). Having an entire naturalized genome, not just a naturalized mother, was important for survival over the first winter. Naturalized offspring outperformed all others in survival to age 1+ and hybrids had reduced, but intermediate, survival relative to the two pure crosses. Averaging over years and streams, survival relative to naturalized offspring was 0.59 for hybrids with naturalized females, 0.37 for the reciprocal hybrids, and 0.21 for hatchery offspring. Our results indicate that naturalized rainbow trout are better adapted to the conditions of Minnesotas tributaries to Lake Superior so that they outperform the hatchery‐propagated strain in the same manner that many native populations of salmonids outperform hatchery or transplanted fish. Continued stocking of the hatchery fish may conflict with a management goal of sustaining the naturalized populations.

Spatial genetic structure of northern pike (Esox lucius) in the Baltic Sea.

The genetic relationships among 337 northern pike (Esox lucius) collected from the coastal zone of the central Baltic region and the Finnish islands of Åland were analysed using five microsatellite loci. Spatial structure was delineated using both traditional F‐statistics and individually based approaches including spatial autocorrelation analysis. Our results indicate that the observed genotypic distribution is incompatible with that of a single, panmictic population. Isolation by distance appears important for shaping the genetic structure of pike in this region resulting in a largely continuous genetic change over the study area. Spatial autocorrelation analysis (Morans I) of individual pairwise genotypic data show significant positive genetic correlation among pike collected within geographical distances of less than c. 100–150 km (genetic patch size). We suggest that the genetic patch size may be used as a preliminary basis for identifying management units for pike in the Baltic Sea.

Better Growth in All-Female Diploid and Triploid Rainbow Trout

Abstract We compared growth of all-female triploid (AFT; 87% triploid), all-female diploid (AFD), and mixed-sex diploid (MSD) rainbow trout Oncorhynchus mykiss in a 265-d growth trial. Triploidy was induced by heat-shocking eggs to prevent second polar body exclusion. Three AFT families, three corresponding full-sibling AFD families, and three MSD families that were half-siblings of the AFD and AFT families were used. Mean initial weights (SD) were 94 g (14), 84 g (12), and 112 g (14) for the MSDs, AFDs, and AFTs, respectively, and final weights (SD) were 521 g (22), 568 g (68), and 749 g (30). Growth was linear. Growth was highest for the AFTs (2.38g/d), lowest for the MSDs (1.58 g/d), and intermediate for the AFDs (1.78 g/d). No significant differences (P > 0.05) were found among treatments for survival, food conversion ratio, condition factor, liversomatic index, viceral fat, and dress-out. By day 180, however, the majority of the MSD males were sexually mature, whereas the MSD females and the AFDs wer...

Incorporating risk assessment and risk management into public policies on genetically modified finfish and shellfish

Abstract Genetically modified finfish and shellfish pose economic benefits to aquaculture, but also pose ecological and genetic risks to ecosystems receiving such organisms. Realization of benefits with minimization of risks posed by a new technology can be addressed through the processes of risk assessment and risk management. Public policies adopted by individual countries will reflect differences in the outcome of risk assessment and risk management processes resulting from differences among the receiving ecosystems and sets of human values at issue. A number of countries and international institutions have begun development of policies for oversight of genetically modified aquatic organisms. In the United States, a working group commissioned by the U.S. Department of Agriculture incorporated risk assessment and risk management principles into draft performance standards for safely conducting research with genetically modified finfish and shellfish. The performance standards address research with a broad range of aquatic GMOs, and compliance is intended to be voluntary. In contrast, the Canadian policy mandates adherence to specified guidelines for experiments with transgenic aquatic organisms; establishment as national policy is expected soon. Based upon the recently-adopted Gene Technology Act, Norwegian policy does not preclude use of genetically engineered aquatic organisms in the aquaculture industry, but the Norwegian government seems unlikely to support such use. Policies on aquatic GMOs have been adopted by leading international institutions concerned with fisheries management or aquaculture. The philosophy and technical content of oversight policies have important implications for scientists involved in research with aquatic GMOs.

Molecular analysis and growth evaluation of northern pike (Esox Iucius) microinjected with growth hormone genes

Gross, M.L., Schneider, J.F., Moav, N., Moav, B., Alvarez, C., Myster, S.H., Liu, Z., Hallerman, E.M., Hackett, P.B., Guise, K.S., Faras, A.J. and Kapuscinski, A.R., 1992. Molecular analysis and growth evaluation of northern pike (Esox lucius) microinjected with growth hormone genes. Aquaculture, 103: 253-273. Bovine (bGH) or chinook salmon (Oncorhynchus tshawytscha) growth hormone (csGH) cDNA genes were transferred by microinjection into newly fertilized northern pike (&OX lucks) eggs. Nonlethal screening of fin tissue showed genomic integration of transgenes in 88 of 1398 putative transgenie fish. Expression of bGH transgenes under transcriptional control of the Rous sarcoma virus long terminal repeat was detected in 36 of 1218 putative transgenic fish examined by radioimmunoassay of blood serum, Bovine growth hormone was also detected in mesodermal tissue of fins from microinjected fish using thin slice immunohistochemistry. Southern hybridizations of six tissues from a sample of 40 microinjected individuals revealed a high degree of mosaicism, with 30% of the fish containing detectable transgenic DNA in one or more tissues and only 41% of these containing detectable transgenes in fins. Growth of microinjected fish was quantitatively evaluated in three experiments. Average weight of microinjected fish was greater than that of controls of the same sex in four out of six groups. Significant growth enhancement (PC 0.05) was detected only for microinjected males in one experiment. Comparisons among molecular assays and individual fish growth in the founder generation indicated that the high degree of mosaicism prevented non-lethal indentification of all transgenic individuals and influences detection of growth enhancement.