Isaac Wirgin

Mechanistic Basis of Resistance to PCBs in Atlantic Tomcod from the Hudson River

Chronic pollution of the Hudson River, New York, results in rapid evolution of resistance to the pollutants. The mechanistic basis of resistance of vertebrate populations to contaminants, including Atlantic tomcod from the Hudson River (HR) to polychlorinated biphenyls (PCBs), is unknown. HR tomcod exhibited variants in the aryl hydrocarbon receptor 2 (AHR2) that were nearly absent elsewhere. In ligand-binding assays, AHR2-1 protein (common in the HR) was impaired as compared to widespread AHR2-2 in binding TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) and in driving expression in reporter gene assays in AHR-deficient cells treated with TCDD or PCB126. We identified a six-base deletion in AHR2 as the basis of resistance and suggest that the HR population has undergone rapid evolution, probably due to contaminant exposure. This mechanistic basis of resistance in a vertebrate population provides evidence of evolutionary change due to selective pressure at a single locus.

When the American sea sturgeon swam east

The two species of Atlantic sea sturgeon on either shore of the North Atlantic, Acipenser sturio in Europe and A. oxyrinchus in North America, probably diverged with the closure of the Tethys Sea and the onset of the North Atlantic Gyre 15–20 million years ago, and contact between them was then presumably precluded by geographic distance. Here we present genetic, morphological and archaeological evidence indicating that the North American sturgeon colonized the Baltic during the Middle Ages and replaced the native sturgeon there, before recently becoming extinct itself in Europe as a result of human activities. In addition to representing a unique transatlantic colonization event by a fish that swims upriver to spawn, our findings have important implications for projects aimed at restocking Baltic waters with the European sturgeon.

Fish populations: When the American sea sturgeon swam east

The two species of Atlantic sea sturgeon on either shore of the North Atlantic, Acipenser sturio in Europe and A. oxyrinchus in North America, probably diverged with the closure of the Tethys Sea and the onset of the North Atlantic Gyre 15–20 million years ago, and contact between them was then presumably precluded by geographic distance. Here we present genetic, morphological and archaeological evidence indicating that the North American sturgeon colonized the Baltic during the Middle Ages and replaced the native sturgeon there, before recently becoming extinct itself in Europe as a result of human activities. In addition to representing a unique transatlantic colonization event by a fish that swims upriver to spawn, our findings have important implications for projects aimed at restocking Baltic waters with the European sturgeon.

Altered gene expression and genetic damage in North American fish populations

Populations of marine, estuarine, and freshwater fish from highly urban and industrialized sites in North America often exhibit elevated prevalences of neoplastic, preneoplastic, and nonneoplastic hepatic lesions, and sometimes epidermal neoplasms compared to conspecifics from more pristine reference locales. Positive statistical associations with environmental concentrations of PAHs and other xenobiotics and experimental laboratory studies suggest a chemical etiology to these epizootics. Studies have investigated the expression of carcinogenically relevant genes, the extent of overall DNA damage, somatic cell mutations, germ line polymorphisms, and overall levels of genetic diversity in fish from these populations and other polluted sites. In general, elevated levels of cytochrome P4501A expression have been found in fish from contaminated locales; however, inhibition of gene induction has been seen in hepatic lesions and in normal tissue in fish from the most contaminated sites, perhaps due to genetic adaptation or physiological acclimation. Levels of bulky hepatic DNA adducts, as detected by 32P-postlabeling, are almost always elevated in fish from populations that are exposed to highly contaminated environments. However, levels of DNA adducts were not always predictive of the vulnerability to neoplasia of populations and species from polluted sites. Elevated levels of oxygen radical-induced DNA damage have been observed in hepatic tumors, preneoplastic lesions, and normal livers in a single species of flatfish from contaminated sites; however, the prevalences of these alterations in other species and at other polluted sites has yet to be evaluated. Frequent alterations in the K-ras oncogene have been reported in hepatic neoplasms in several species from highly contaminated sites and also in embryos that were experimentally exposed to oil-contaminated sediments. Studies also suggest that heritable germ line polymorphisms, altered allelic frequencies, and reductions in overall genetic diversity may have occurred in some highly impacted populations; however, the origin and functional significance of altered allelic frequencies have largely yet to be evaluated. In summary, feral fish appear particularly sensitive to DNA alterations from xenobiotics, perhaps due to their unusually high levels of exposure, relatively inefficient DNA repair, and the high frequency of polyploidy in some taxa and provide excellent models to explore the relationships between xenobiotic exposure and altered gene structure and expression.

Stock Composition of the New York Bight Atlantic Sturgeon Fishery Based on Analysis of Mitochondrial DNA

Abstract One of the few remaining fisheries for Atlantic sturgeon Acipenser oxyrinchus takes place during spring and fall in the New York Bight, but no information on the stock composition of this fishery is available. We used data from mitochondrial DNA (mtDNA) restriction fragment length polymorphism analysis to estimate the relative contributions of source stocks of Atlantic sturgeon to a New York Bight fishery sample (N = 112) collected in 1993 and 1994. Composite mtDNA haplotype frequencies of source populations were first characterized with five informative restriction enzymes: Bgl I, Msp I, EcoR V, Hinf I, and Hinc II. All St. Lawrence River, Quebec, and St. John River, New Brunswick, specimens had an identical haplotype (genotypic diversity = 0.0); for the purposes of mixed-stock analysis, both populations were pooled as the “Canadian stock.” Genotypic diversity ranged between 0.483 and 0.750 among samples from the Hudson River in New York, the Edisto River in South Carolina, and the Ogeechee, Alt...

Sea lamprey Petromyzon marinus: an exception to the rule of homing in anadromous fishes

Anadromous fishes are believed to make regular circuits of migration in the sea before homing to their natal rivers. Sea lamprey Petromyzon marinus is an anadromous fish that is an exception to this life-history pattern. It also differs from other anadromous fishes in that its adult phase is parasitic, a feeding strategy that should make homing problematic for lamprey cohorts that become widely dispersed through transport by the diverse hosts they parasitize. We sequenced a portion of the mitochondrial DNA control region from sea lampreys collected from 11 North American east coast rivers to test for genetic evidence of homing. There were no significant differences (Χ2=235.1, p=0.401) in haplotype frequencies among them, with almost 99 per cent of haplotypic diversity occurring within populations. These findings, together with concordant genetic results from other geographical regions and ancillary information on pheromonal communication, suggest that sea lamprey does not home but rather exhibits regional panmixia while using a novel ‘suitable river’ strategy to complete its life cycle.

Review of Stock Discrimination Techniques for Striped Bass

Abstract Attempts to discriminate stocks of striped bass Morone saxatilis have spanned five decades. We review and evaluate the approaches used, outline research trends, and suggest research needs and potential future applications of stock discrimination techniques. There have been moderate gains over the years in the ability to discriminate among stocks, primarily due to the use of biochemical techniques. An important mixed-stock fishery for striped bass off the northeastern USA has focused the majority of stock discrimination efforts on identification of Atlantic coast populations. Many techniques have been applied alone or in combination. Phenotypic studies have involved the presence of specific parasites, meristic and morphometric characters, trace element composition of scales, scale morphology, and densitometric analysis of isoelectrically focused eye lens proteins. Genotypic techniques have included cytogenetics, protein electrophoresis, isoelectric focusing, restriction endonuclease analysis of mi...

Genetic structure of Atlantic sturgeon populations based on mitochondrial DNA control region sequences

Abstract The Atlantic sturgeon Acipenser oxyrinchus oxyrinchus has a latitudinally broad distribution along the east coast of North America, with extant populations occurring from the Saint Lawrence River to rivers in southern Georgia. This species once supported intensive caviar-based fisheries that resulted in overharvest and sharply reduced population abundances; presently, directed commercial fishing for Atlantic sturgeon is banned in U.S. waters. We sequenced a 203-base-pair section of the mitochondrial DNA (mtDNA) control region of 322 Atlantic sturgeon specimens from 11 river systems across their range to elucidate their stock structure. We found a pronounced latitudinal cline in the number of composite mtDNA haplotypes and in haplotypic diversity, which increased from north to south, from previously glaciated and subsequently recolonized systems to the portion of their range unglaciated during the Pleistocene. The observed number of haplotypes per population ranged from 1 haplotype in each of the ...

Genetic Divergence between Acipenser oxyrinchus oxyrinchus and A. o. desotoi as Assessed by Mitochondrial DNA Sequencing Analysis

COHEN, J. 1971. The comparative physiology of gamete populations. Adv. Phys. Biochem. 4:267-381. CREWS, D. 1975. Effects of different components of male courtship behavior on environmentally induced ovarian recrudescence and mating preferences. Anim. Behav. 23:339-346. DARWIN, C. 1871. The descent of man and selection in relation to sex. John Murray, London. GUNNARSSON, B., ANDJ. JOHNSSON. 1990. Protandry and moulting to maturity in the spider Pityophantes phrygianus. Oikos 59:205-212. LACK, D. 1968. Ecological adaptations for breeding in birds. Methuen, London. MAGNHAGEN, C. 1991. Predation risk as a cost of reproduction. Trends Ecol Evol. 6:183-186. OLSSON, M. 1993. Male preference for large females and assortative mating for body size in the sand lizard (Lacerta agilis). Behav. Ecol. Sociobiol. 32: 337-341. , A. GULLBERG, H. TEGELSTR6M, T. MADSEN, AND R. SHINE. 1994a. Can adders multiply? Scientific Correspondence. Nature 369:528. , T. MADSEN, R. SHINE, A. GULLBERG, AND H. TEGELSTR6M. 1994b. Rewards of promiscuity. Ibid. 372:230.

An Empirical Comparison of Stock Identification Techniques Applied to Striped Bass

Abstract Managers of migratory striped bass stocks that mix along the Atlantic coast of the USA require periodic estimates of the relative contributions of the individual stocks to coastal mixed-stock fisheries; however, to date, a standard approach has not been adopted. We compared the performances of alternative stock identification approaches, using samples taken from the same sets of fish. Reference (known) samples were collected from three Atlantic coast spawning systems: the Hudson River, Chesapeake Bay, and the Roanoke River. Striped bass of mixed-stock origin were collected from eastern Long Island, New York, and were used as test (unknown) samples. The approaches applied were discriminant analysis of morphometric data and of meristic data, logistic regression analysis of combined meristic and morphometric data, discriminant analysis of scale-shape features, discriminant analysis of immunoassay data, and mixed-stock analysis of mitochondrial DNA (mtDNA) data. Overall correct classification rates o...