Low dispersal and sexual selection are characteristic of the coastal polychaete Nereis acuminata Ehlers 1868 [also known as Nereis arenaceodentata Moore 1903 and Nereis (Neanthes) caudata Delle Chiaje 1841]. We assessed levels of premating isolation between populations of this polychaete. Four North American populations were used, two from the Atlantic and two from the Pacific. Worms from all sites (1) were collected in 1987 and 1988 from the same habitat type, (2) were morphologically similar and keyed out as N. acuminata, and (3) reproduced monogamously and exhibited male parental care, an extremely rare reproductive mode in marine invertebrates. There was no evidence from 10-rain or 36-h trials of premating isolation between the two Pacific populations. Incomplete premating isolation was found between the two Atlantic populations. High aggression and non-pairing occurred in some 10-rain trials between males and females. However, in 36-h trials males and females from the two Atlantic populations always paired to mate. Complete premating isolation was found between Atlantic and Pacific populations. During 10-rain trials, males and females from different oceans often attacked and then avoided each other, and they never paired to mate. Nor did they pair to mate in longer, 36-h trials. One Pacific and one Atlantic population were compared for tolerance to cold temperature. Pacific individuals were less able to tolerate cold water than Atlantic individuals. Two Atlantic populations studied had karyotypes with 11 pairs of small acrocentric chromosomes (2n=22), while the two Pacific populations had nine pairs of large metacentric or submetacentric chromosomes (2n = 18). Such extreme dissimilarity in karyotype was not expected considering the similarity in morphology, habitat, and reproductive mode. Results suggest strongly that the Atlantic and Pacific populations have been allopatric for a long time, and are different species.

Four bioassays [MicrotoxTM, MutatoxTM, sister chromatid exchange (SCE), and metabolic cooperation] were used to analyze marine sediment extracts fractionated by two different methods: silica gel column chromatography and acid–base fractionation. Results indicated that a sediment extract fractionated with different methods can lead to different conclusions about the same sediment. This research also further evaluated the new, mutagenic, bacterial bioassay Mutatox. Mutatox generally correlated with SCE and the Salmonella typhimurium assays. This rapid, operationally simple bioassay has potential as a screening bioassay to detect genotoxic agents. © 1994 by John Wiley & Sons, Inc..

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A mammalian in vitro system was used to evaluate the genotoxic potential of two complex environmental samples. Sister chromatid exchanges (SCEs) were measured in Chinese hamster V79 lung fibroblast cells, following exposure to whole extracts of sediments collected from a highly contaminated harbor — Black Rock Harbor, Connecticut (BRH) — and from a reference site — central Long Island Sound (CLIS). Characterization of BRH sediment by analysis of prepared chemical extracts revealed high concentrations of polyaromatic hydrocarbons, anthraquinones, carbazoles, and several inorganic substances that are genotoxic and capable of inducing SCEs. The CLIS sediment, although cleaner than BRH sediment, does contain low levels of similar contaminants. For instance, BRH sediment contains 3.16 μg/g of the polynuclear aromatic hydrocarbon benzo[a]pyrene (BP), whereas CLIS sediment contains only 0.807 μg/g BP. Sediments were extracted with organic solvents and redissolved in dimethyl sulfoxide (DMSO) for culture exposure. Following exposure, extract‐treated cells were evaluated for increased frequencies of SCEs. All assays were performed with and without exogenous S9 activation. Positive responses were observed only in the presence of exogenous S9 metabolism. Results indicated a concentration‐dependent increase in SCEs in cells exposed to whole BRH sediment extracts and a smaller but significant increase in SCEs in cells exposed to whole CLIS sediment extracts. Four times as much CLIS material (0.13 g extracted sediment [dry wt.]/ml of exposure media) was needed to induce a significant doubling in SCEs, compared to BRH material, in which only 0.03 g extracted sediment (dry wt.)/ml of exposure media was needed. These findings imply that this short‐term in vitro bioassay can be used to evaluate the genotoxic potential of complex environmental samples such as contaminated marine sediments.

Changes in ethoxyresorufin-O-deethylase (EROD) activity were monitored through an extended 6-month dietary exposure to determine the relationship between EROD activity and uptake of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in brook trout, Salvelinus fontinalis. Brook trout were fed labeled TCDD during a 4-week loading phase and an 11-week maintenance phase to achieve whole-body concentrations of 0, 75, 150, 300, 600, and 1,200 pg TCDD/g fish. A spawning phase followed during which no TCDD was introduced. The TCDD had an extended half-life, with maximal levels detected in the late loading-early maintenance phases and 81 d after TCDD had been removed from the diet. Accumulation in liver increased as whole-body target concentration increased but was generally less than half of anticipated whole-body target concentrations. The EROD activity demonstrated a dose-dependent increase. Positive correlations were observed between EROD activity and TCDD body burdens for both males and females. For males, maximal induction was attained early in the maintenance phase and maintained during latter phases. For females, induction was characterized by a biphasic pattern. Maximal induction was attained during late loading-early maintenance, with an attenuated response observed just before spawning. In addition, the induction response was modulated by sex, as induction was lower in females when compared with males. If sexual biases are considered, increased EROD activity may serve as an indicator of level of TCDD exposure and a sublethal predictor of effects of exposure. Keywords-Ethoxyresorufin-O-deethylaseInduction 2,3,7,8-Tetrachlorodibenzo-p-dioxin Brook trout Salvelinus fontinalis EROD response of TCDD-fed brook trout