Survival and chloride ion regulation of the porcelain crab Petrolisthes armatus exposed to mercury

Acute toxicity bioassays conducted at various salinities demonstrated that mercury (as mercuric chloride) at low concentrations was lethal to Petrolisthes armatus. Ninety-six hour LC₅₀ values varied from 50 to 64 parts per billion (ppb) of mercury, depending on test salinities. Lower salinities. decreased the time to death of mercuryexposed crabs. Differences in survival after 96 h due to salinity were not statistically significant. Blood chloride concentrations were regulated hyperchloride to the medium at low salinities and hypochloride at high salinities by acclimated crabs. The salinity isochloride to blood was 20 S. Transfer of crabs from 15 S to salinities ranging from 7 to 35 S resulted in new steadystate chloride levels within 12 h. Exposure to 50 ppb mercury did not alter chloride ion regulation of either acclimated crabs or crabs adjusting to new salinities.     

Genetic structure of leopard shark (<Emphasis Type="Italic">Triakis semifasciata</Emphasis>) populations in California waters

The leopard shark (Triakis semifasciata) is an important predator in coastal marine ecosystems of California, targeted by recreational and commercial fishermen and of specific interest in fisheries management. From October 2003 to August 2006, 169 leopard sharks were collected from the coast of California (between 40.750°N and 32.678°N) and analyzed for mitochondrial and nuclear genetic structure. Analyses of mtDNA control region sequences revealed relatively low levels of genetic variation (five haplotypes, average pairwise divergence π = 0.0067). In contrast, leopard sharks were highly polymorphic for inter simple sequence repeats (ISSRs), which characterize a broad range of the nuclear genome. The null hypothesis of panmixia in California waters was rejected for both genetic markers, and ISSRs displayed a statistically significant pattern of isolation by distance (IBD) across the species range (P = 0.002). A variety of analyses showed that divergence is most pronounced in the northernmost population of Humboldt Bay. Natal philopatry in T. semifasciata was tested using Siegel-Tukey tests on data partitioned by breeding site status, and sex-specific philopatry was tested by comparing IBD plots between sexes. Although there was some evidence for natal philopatry in leopard sharks (P = 0.038), and population divergence may be related to the proximity of breeding sites (P = 0.064), we found no support for sex-specific philopatry. In addition to identifying a novel set of highly variable genetic markers for use in shark population studies, these results may be used to better inform management decisions for leopard sharks in California.     

Behaviour around encounter sites

Summary We develop a model for the distribution of animals around encounter sites. It is particularly applicable to males attending mate-encounter sites, such as hilltops. Major predictions are: male distributions should be unstable; males should show little site tenacity, particularly when at low densities; males with low probability of mate capture should occupy subordinate positions; probability of mate capture is a better predictor of position than resource-holding potential; female choice favours despotic distributions; males should often patrol together. Several of these predictions are met, others are testable. We identify some parameters that should be more extensively studied.     

The influence of pH and household plumbing on water lead concentration

The water lead concentrations measured in the homes of children who were part of the Edinburgh Lead study are related to the characteristics of the water supply and the household plumbing. At the time of the study one of the City of Edinburgh's two water supplies was lime treated to reduce plumbosolvency but in the second supply this treatment had not yet become effective. This allows us to estimate the extent to which this type of water treatment reduces water lead concentrations, in houses with lead plumbing, to comply with existing and proposed limits for lead in water. The kitchen cold water was supplied from a lead storage tank in 69 (15%) of the houses. These houses had the highest lead concentrations and water treTo whom correrspondence should be addressed.     

Dominions and site-fixed aggressive behavior in breeding male Leucorrhinia intacta (Odonata: Libellulidae)

Summary We report aggressive spacing behavior in male dragonflies, Leucorrhinia intacta, that is characterized by variations in the probability of chasing conspecific male intruders within a defined area around a male's perch. The chase probability depends on the total intruder pressure and the behavior and distance of the intruder from the perched male (Fig. 2). This nonexclusive, site-fixed area has been called a dominion.We also examined the distribution of intruders among the various behavior-distance categories. Chase rates (per 15 min) were correlated mostly with number of intruders that hovered (rather than flew) close to the territorial male. Finally, we examined the impact of the changing chase probabilities on the variation in aggressive interactions as a function of intruder pressure. We conclude that, to some extent, territorial males stabilized defense costs across a variety of intruder pressures by maintaining dominions.     

Effects of symbiont elimination and reinfection on the life processes of the planktonic foraminifer Globigerinoides sacculifer

Laboratory experiments were carried out to determine the influence of symbiotic dinoflagellates (zooxanthellae) on the shell growth, longevity, and reproductive potential of Globigerinoides sacculifer (Brady). Its symbionts were eliminated by 72-h treatment with a photosynthetic inhibitor (DCMU). Symbiont elimination resulted in earlier gametogenesis (shortened survival time) and smaller shell sizes of G. sacculifer when compared to untreated foraminifera grown in sea water. Individuals kept in continuous darkness in untreated sea water also exhibited early gametogenesis, short survival times and small shell sizes. Aposymbiotic foraminifera formed on the average one or two chambers fewer per individual and their rate of shell size increase is slower than symbiont-bearing foraminifera. Symbionts were lysed within perialgal vacuoles of G. sacculifer when subjected to DCMU treatment or kept in continuous darkness. One DCMU-treated group was reinfected with symbionts from crushed G. sacculifer donors. Soon after reinfection, these foraminifera resumed a shell growth rate and exhibited developmental stages that were nearly equivalent to those of untreated individuals, as deduced from their shell size, frequency of sac-like chambers, rate of gametogenesis, and survival time. Our experiments indicate that the symbionts aid in calcification and that elimination of symbionts triggers gametogenesis, thus shortening the life span of the foraminiferal host. The results imply that shell growth in symbiont-bearing planktonic foraminifera occurs mainly in the euphotic zone and that they do not survive for long periods below it.     

Osmoregulation of the grass shrimp Palaemonetes pugio Exposed to polychlorinated biphenyls (PCBs).

Glycine was the most abundant free amino acid (FAA) in abdominal muscle of grass shrimp Palaemonetes pugio, accounting for over 50% of the total pool. Arginine, alanine, proline, taurine and serine were also present at relatively high concentrations. Following transfer from 17%. to 2 and 32%. S, new steady-state levels of total FAA were observed at 72 h. Total FAA and the sum of glycine, alanine and proline exhibited a positive correlation with salinity. Exposure to Aroclor 1254 did not have appreciable effects on total FAA levels, indicating that disruption of intracellular osmoregulation was not a major consequence of PCB toxicity. However, changes in individual amino acid concentrations in exposed shrimp were reflective of an altered metabolic state. Glycine, which did not show changes immediately following exposure, underwent large decreases after transfer to PCB-free water and indicated a delayed effect of PCB exposure. A correlation between salinity and the sum of glycine, alanine and proline did not exist in exposed shrimp.     

Accumulation and release of fuel-oil-derived diaromatic hydrocarbons by the polychaete Neanthes arenaceodentata

Male and gravid female Neanthes arenaceodentata (Moore) (Polychaeta: Annelida) were experimentally exposed to a sublethal concentration of No. 2 fuel oil seawater extract for 24 h. Within 1 h both sexes had incorporated, in equal proportions, most of the diaromatic hydrocarbons (naphthalene, methylnaphthalenes) eventually accumulated. No net loss of accumulated naphthalenes was observed during the exposure period. When returned to hydrocarbon-free seawater, male worms slowly released naphthalenes down to undetectable (< 0.1 ppm) levels in 400 h (17 days). Gravid females retained essentially all of the originally accumulated naphthalenes for 3 weeks, at which time they released their eggs during fertilization, with subsequent dramatic decreases in naphthalenes content. Zygotes and trochophore larvae from exposed females contained 18 ppm naphthalenes, accounting for a majority of those amounts initially present in parent females. As trochophore larvae developed into 18-segment juveniles, naphthalenes concentrations dropped to near undetectable levels (0.4 ppm) in 21-day old juveniles (= 18-segment worms). When sampled at the next stage of development (32-segment worms) 5 days later (1050 h after exposure of gravid females), offspring were free of naphthalenes. Results suggest the importance of lipid-rich eggs in the accumulation and retention of diaromatic hydrocarbons by marine polychaetes.     

Statistical inference on patch-specific survival and movement rates from marked animals

Empirical estimates of patch-specific survival and movement rates are needed to parametrize spatially explicit population models, and for inference on the effects of habitat quality and fragmentation on populations. Data from radio-marked animals, in which both the fates and habitat locations of animals are known over time, can be used in conjunction with continuous-time proportional hazards models to obtain inferences on survival rates. Discrete-time conditional logistic models may provide inference on both survival and movement rates. We use Monte Carlo simulation to investigate accuracy of estimates of survival from both approaches, and movement rates from conditional logistic regression, for two habitats. Bias was low (relative bias < 0.04) and interval coverage accurate (close to the nominal 0.95) for estimates of habitat effect on survival based on proportional hazards. Bias was high ( relative bias 0.60) and interval coverage poor ( = 0.26 vs. nominal 0.95) for estimates of habitat effect based on conditional logistic regression; bias was especially influenced by heterogeneity in survival and the shape of the hazard function, whereas both bias and coverage were affected by ‘memory’ effects in movement patterns. Bias estimates of movement rate was low ( relative bias < 0.05), but interval coverage was poor ( = 0.48–0.80), possibly as a result of poor performance of a Taylor series estimate of variance. An example is provided from a radio-telemetry study of 47 wintering American woodcock (Scolopax minor), illustrating practical difficulties in field studies to parametrize these models. We also discuss extensions of continuous-time models to explicitly include a movement process, and further examine tradeoffs between continuous and discrete models.