Dynamics of shallow-water populations of Octopus dofleini

Octopus dofleini (Walker) is a common inhabitant of shallow subtidal communities in the Northeast Pacific. The abundances of octopuses at two sites monitored since 1977 have fluctuated greatly during this period. The populations reached high abundances in mid-summer and, during some years, mid-winter. The highest abundances at the two sites did not coincide. There was a constant influx of new octopuses into both study sites, with the greatest immigration occurring in early summer. The octopuses captured spanned a wide range of weights every month, with no clear size classes or seasonal trends in size. The weights of newly-captured octopuses, however, did differ between the sexes and seasons: males weighed more on the average than females, and male weight decreased from winter to fall while female weights did not change O. dofleini appeared to recruit throughout the year; the smallest octopuses occurred between May and November and the greatest number of small octopuses was found in July and August in most years. Females predominated at both study sites throughout the year. However, males predominated among octopuses caught in traps at nearby locations, suggesting that the skewed sex ratios were due to behavioral differences between the sexes.     

Vocal regulation of use of space by groups of titi monkeys Callicebus moloch

Summary The daily movements and the resulting activity and calling fields are described for three groups of titi monkeys Callicebus moloch. Groups move to the periphery of their home range in the early morning and then call. Playback experiments confirmed that both proximity and location of calling by neighboring animals affect the group's response. Subsequent countercalling often regulates the approach of neighboring groups to a boundary. After encountering adjacent groups, animals return to areas near the home range center. Movements, calling behavior, and the response to neighboring groups all increase the probability of intergroup encounters in the early morning. Encounters define and reinforce the conventional location of boundaries. Boundaries decrease the probability of intergroup encounters at other times and allow exclusive use of space.     

Mercury volatilisation and phytoextraction from base-metal mine tailings

Experiments were carried out in plant growth chambers and in the field to investigate plant-mercury accumulation and volatilisation in the presence of thiosulphate (S2O3)-containing solutions. Brassica juncea (Indian mustard) plants grown in Hg-contaminated Tui mine tailings (New Zealand) were enclosed in gastight volatilisation chambers to investigate the effect of ammonium thiosulphate ([NH4]2 S2O3) on the plant-Hg volatilisation process. Application of (NH4)2 S2O3 to substrates increased up to 6 times the Hg concentration in shoots and roots of B. juncea relative to controls. Volatilisation rates were significantly higher in plants irrigated only with water (control) when compared to plants treated with (NH4)2 S2O3. Volatilisation from barren pots (without plants) indicated that Hg in tailings is subject to biological and photochemical reactions. Addition of sodium thiosulphate (Na2S2O3) at 5 g/kg of substrate to B. juncea plants grown at the Tui mine site confirmed the plant growth chambers studies showing the effectiveness of thio-solutions at enhancing shoot Hg concentrations. Mercury extraction from the field plots yielded a maximum value of 25 g/ha. Mass balance studies revealed that volatilisation is a dominant pathway for Hg removal from the Tui mine site. A preliminary assessment of the risks of volatilisation indicated that enhanced Hg emissions by plants would not harm the local population and the regional environment.     

Comparison of particle light scattering and fine particulate matter mass in central California

Particle light scattering (Bsp) from nephelometers and fine particulate matter (PM2.5) mass determined by filter samplers are compared for summer and winter at 35 locations in and around California's San Joaquin Valley from December 2, 1999 to February 3, 2001. The relationship is described using particle mass scattering efficiency (sigmasp) derived from linear regression of Bsp on PM2.5 that can be applied to estimated PM2.5 from nephelometer data within the 24-hr filter sampling periods and between the every-6th-day sampling frequency. An average of sigmaSp = 4.9 m2/g was found for all of the sites and seasons; however, sigmasp averaged by site type and season provided better PM2.5 estimates. On average, the sigmasp was lower in summer than winter, consistent with lower relative humidities, lower fractions of hygroscopic ammonium nitrate, and higher contributions from fugitive dust. Winter average sigmasp were similar at non-source-dominated sites, ranging from 4.8 m2/g to 5.9 m2/g. The sigmasp was 2.3 m2/g at the roadside, 3.7 m2/g at a dairy farm, and 4.1 m2/g in the Kern County oilfields. Comparison of Bsp from nephelometers with and without a PM2.5 inlet at the Fresno Supersite showed that coarse particles contributed minor amounts to light scattering. This was confirmed by poorer correlations between Bsp and coarse particulate matter measured during a fall sampling period.     

The invasion and subsequent die-off of <Emphasis Type="Italic">Mytilus galloprovincialis</Emphasis> in Langebaan Lagoon,South Africa: effects on natural communities

The alien mussel Mytilus galloprovincialis invaded sand banks in Langebaan Lagoon on the west coast of South Africa in the mid-1990s. However, by 2001 these beds had completely died off, with only empty shells and anoxic sand remaining. In an effort to prevent the re-settlement of this aggressive invader, all dead mussel shells were then cleared. This study considered the impacts of the invasion and subsequent die-off on natural benthic communities. Community composition differed significantly between non-invaded and invaded areas (ANOSIM, R = 0.685 and P < 0.01) as the physical presence of mussel beds created a new habitat that promoted invasion by indigenous rocky-shore species. This dramatically increased faunal biomass from 1,132.9 g m⁻² ± 3,454.7 SD to 53,262.4 g m⁻² ± 23,052.6 SD and species richness from 38 to 49 species. Following the die-off of the mussel beds, communities remained significantly different between non-invaded areas and those in which mussel shells remained (ANOSIM, R = 0.663 and P < 0.01). Species richness was significantly greater in non-invaded areas (18 species) than in uncleared areas with remnant shells (four species) (Kruskal–Wallis ANOVA H _2,36 = 10.8964 and P = 0.032), as the previously dominant rocky-shore species became smothered by sediment and the compacted shells formed an impermeable layer excluding sandy-shore burrowing organisms. After the shells were cleared, 50% of the sandy-shore species associated with non-invaded areas returned within 5 months, but community structure still remained significantly different to non-invaded areas (ANOSIM, R = 0.235 and P > 0.05). Invasion thus dramatically altered natural communities and although the subsequent removal of the dead mussel shells appears to have aided recovery, community composition remained different from the pre-invasion state after 5 months.     

The costs of intersexuality: a crustacean perspective

Increasing concerns over rising intersexuality in the animal kingdom and the ability of certain chemicals to disrupt the endocrine system have demanded a better understanding of the costs associated with such conditions. Whilst intersexuality appears relatively widespread throughout gonochoristic crustaceans, i.e. those crustacean species with two separate sexes, the fitness costs have rarely been reported. Through comparable investigation of normal and intersex specimens of the highly abundant marine/estuarine amphipod Echinogammarus marinus (Leach) these fitness costs were determined. Measurements taken to assess fitness costs included fecundity, fertility and embryonic development, maturation period, and any morphological deformities that might result in reduced pairing success. Results from this study suggest that intersex E. marinus suffer from reduced fecundity and fertility, and mature at a larger size than normal specimens. These fitness costs can also, to a certain extent, be related to the degree of intersexuality. It is suggested that the increased size and morphological abnormalities observed in intersexes may result in reduced pairing success. Investigations into intersex organisms, i.e. those organisms with known dysfunctional endocrine systems, and the costs associated with such conditions, should aid researchers in assessing effects at the population and community level.Communicated by J.P. Thorpe, Port Erin