Chromosomal and nuclear characteristics of deep-sea hydrothermal-vent organisms: correlates of increased growth rate

A range of tissue and cell types from adult and juvenile stages of vent- and non-vent-dwelling deep-sea and shallow-water organisms were compared for signs of cell division, in preparation for a cytogenetic study of the different groups. Virtually all the Mid-Atlantic Ridge (MAR) vent species (bresiliid shrimp, bathymodiolid mussel, branchipolynoid polychaete, and a range of small gastropods) showed an abundance of metaphase chromosome spreads, indicating a generally high intrinsic rate of cell division, irrespective of their phylogenetic group. In comparison, similar tissues and life-history stages (i.e. gonad, developing eggs and gill) from two deep-sea bathypelagic crustaceans, Hymenodora and Gnathophausia, failed to yield any convincing evidence of cell division. This indicated that rates of growth and reproduction in the rest of the deep sea are extremely low. While much has been written about the contrasting growth rates of vent versus non-vent organisms, this is the first direct evidence of differences in cell-division rate between vent and non-vent species, which undoubtedly reflects contrasting conditions relating to food availability and temporal stability in these two deep-sea environments. The cells of shallow-water marine invertebrates (Mytilus, Nucella, Littorina, Pomatoceros and Crangon), based on the results of previous cytogenetic investigations, occupy an intermediate position with respect to their cell-division kinetics. When chromosome numbers, DNA content and nuclear diameters were compared between vent and non-vent species, this showed that no change had occurred in these characters since the time of vent colonisation. Representative chromosome spreads from hydrothermal-vent organisms are shown here for the first time.     

Satisfaction with fishing and the desire to leave

Predicting who may leave a fishery is an important consideration when designing capacity reduction programs to enhance both ecological and economic sustainability. In this paper, the relationship between satisfaction and the desire to exit a fishery is examined for the Queensland East Coast Trawl fishery. Income from fishing, and changes in income over the last 5 years, were key factors affecting overall satisfaction. Relative income per se was not a significant factor, counter to most satisfaction studies. Continuing a family tradition of fishing and, for one group, pride in being a fisher was found to be significant. Satisfaction with fishing overall and the challenge of fishing were found to be the primary drivers of the desire to stay or leave the fishery. Surprisingly, public perceptions of fishing, trust in management and perceptions of equity in resource allocation did not significantly affect overall satisfaction or the desire to exit the fishery.     

Cephalopod remains from the stomach of a sperm whale stranded off Patagonia

The stomach of a male sperm whale (Physeter macrocephalus) stranded near Comodoro Rivadavia, Argentina, on 21 March 1986, contained 247 cephalopod beaks (128 upper and 119 lower). The lower beaks were identified, their rostral lengths were measured and used to estimate the mantle lengths and wet weight of the representatives of each cephalopod taxon. Fifteen species from nine families were represented. The most numerous species, in order of decreasing abundance, were the large cranchiidMesonychoteuthis hamiltoni (32.8% of total numbers),Mastigoteuthis sp. A (16.0%), andKondakovia longimana andHistioteuthis atlantica (both 13.5%). Almost 85% of the estimated total weight was contributed by two species,Mesonychoteuthis hamiltoni (61.6%) andK. longimana (23.1%). The presence of beaks fromK. longimana, Alluroteuthis antarcticus andM. hamiltoni, which are all thought to be restricted to the Antarctic, suggests that the whale had migrated North prior to stranding.     

A comparison of methods for measuring acute toxicity to Hydra vulgaris

The freshwater coelenterate Hydra vulgaris (Pallas) is a common component of freshwater ecosystems and is sensitive to a range of pollutants. It can be cultured easily in the laboratory to provide large numbers of test animals and can be used in simple, cost effective bioassays of both acute, sub-acute and chronic toxicity. This study, using the heavy metals: copper, cadmium and zinc, aimed to compare two methods of assessing acute toxicity. The first method was based upon a conventional determination of LC50s while the second involved an evaluation, using a scoring procedure, of progressive changes in structure and proved to have a number of advantages compared with a simple LC50. These include the potential to help explain mechanisms of toxicity and to examine the ability of animals to recover from pollutant-induced damage.     

Do pharmaceuticals affect freshwater invertebrates? A study with the cnidarian Hydra vulgaris

Pharmaceuticals enter natural waters through sewage effluent and landfill leachates and present an unknown risk to aquatic species including freshwater invertebrates. In this study the acute and chronic toxicity of 10 drugs, commonly prescribed in the UK i.e. ibuprofen, paracetamol, acetylsalicylic acid, amoxicillin, bendroflumethiazide, furosemide, atenolol, diazepam, digoxin, amlodipine were assessed using the cnidarian Hydra vulgaris. In a 7 day exposure period there were no effects on survival at concentrations up to 1.0 mg l(-1) and after 17 days neither feeding nor bud formation were adversely affected. However the ability of dissected polyps to regenerate a hypostome, tentacles and foot was inhibited by diazepam, digoxin and amlodipine at 10 microg l(-1). It is suggested that other drugs targeted at mammalian receptor systems may also affect aquatic invertebrates although it is unlikely, at their low environmental concentrations, that those examined in this study actually present a risk.     

The Cost of Co-viability in the Australian Northern Prawn Fishery

Fisheries management must address multiple, often conflicting objectives in a highly uncertain context. In particular, while the bio-economic performance of trawl fisheries is subject to high levels of biological and economic uncertainty, the impact of trawling on broader biodiversity is also a major concern for their management. The purpose of this study is to propose an analytical framework to formally assess the trade-offs associated with balancing biological, economic and non-target species conservation objectives. We use the Australian Northern Prawn Fishery (NPF), which is one of the most valuable federally managed commercial fisheries in Australia, as a case study. We develop a stochastic co-viability assessment of the fishery under multiple management objectives. Results show that, due to the variability in the interactions between the fishery and the ecosystem, current management strategies are characterized by biological and economic risks. Results highlight the trade-offs between respecting biological, economic and non-target species conservation constraints at each point in time with a high probability and maximizing the net present value of the fishery.     

The toxicity of copper,cadmium and zinc to four different Hydra (Cnidaria: Hydrozoa)

An acute toxicity study of three metals to Hydra species carried out using two different assessment methods, (i) determination of the LC50 and (ii) measurement of progressive morphological changes, demonstrated that relative toxicity decreased from copper to cadmium with zinc the least toxic for all species. The latter method revealed more details of the effect on Hydra in terms of physical damage to the polyp but both methods indicated that H. viridissima was more sensitive to copper and cadmium than H. vulgaris¹ (Zurich strain, male clone), H. vulgaris² (a dioecious strain reproducing sexually and asexually) and H. oligactis (dioecious, reproducing sexually and asexually). The responses to zinc were similar for all Hydra. The possible role of metabolic interactions between H. viridissima and its symbiotic green algae in contributing to the greater sensitivity of this polyp is discussed.     

Reduced Metals Concentrations of Water, Sediment and Hyalella Azteca from Lakes in the Vicinity of the Sudbury Metal Smelters, Ontario, Canada

Hyalella azteca (Crustacea: Amphipoda), water and sediments from 12 circum-neutral lakes between Sudbury and North Bay in Ontario, Canada were sampled in August 1998 and analyzed for 10 metals including Cu, Zn, Cd, Ni, Pb, Co, Mo, V, Ba and Ti. Statistical analyses showed that concentrations of the metals in H. azteca, water and sediment differed significantly (ANOVA, P<0.05) among lakes (except for Zn and Pb in H. azteca and Mo in water). There was a trend of declining metal concentration, especially for Cu, Ni and Co (in water, Hyalella and sediment), with distance from the smelters indicating the reduced impact of atmospheric pollution. Metal concentrations of lakes (water) in the Sudbury area were found to be lower compared to data from the 1970s and 1980s indicating an improvement in water quality. Metal concentrations in field-collected amphipods compared favorably with those measured in the laboratory in animals exposed to deep-water sediments, provided metal concentrations were not extremely low (e.g., Pb) and that water chemistry differences (e.g., pH) were taken into account for some metals (especially Cd). In general bioaccumulation of metals in H. azteca was predicted better from surface water than from sediment total metal.     

Investigation of hydrocyclones for the separation of shredded fridge plastics

The recycling of fridges produces a mixed plastic product of limited value. In order to maximise its value, the separation of the individual polymers that include high impact polystyrene (HIPS), acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC) and polyethylene (PE) must take place. The effectiveness of a hydrocyclone system for the separation of these plastics, using both water and calcium chloride solutions, has been investigated. In addition a qualitative procedure for the determination of the HIPS content of a mixed ABS/HIPS product, by selective dissolution in R-limonene, has been developed. It was found that the effective density of separation depended on the particle size and aspect ratio. As the particle size and aspect ratio decreased, the separation became more efficient and the offset between separation density and hydrocyclone medium density decreased. This suggests that, for efficient density separation, closely sized, fine plastic fractions are required. Using these criteria, it was found that the removal of high density plastic such as PVC was readily achieved using a hydrocyclone. A partial separation of HIPS from ABS was found to be possible, taking advantage of a small density difference, using a hydrocyclone medium density of 1035kgm(-3).     

Structural chromosomal polymorphism in the dog-whelk Nucella lapillus (Mollusca: Neogastropoda)

On the English and French Channel coasts, the dog-whelk Nucella lapilus (L.) exhibits variation in chromosome number which appears to correlate with the degree of wave action on the shore. The more common, 2n=26 morph is typically found on exposed shores subjected to a high degree of wave action, whereas those with higher chromosome numbers, up to the recorded maximum of 2n=36, are restricted to more sheltered environments. The polymorphism is thought to be Robertsonian in nature, involving centric (centromere) fission or fusion, but detailed analysis of the polymorphism has been restricted by lack of success in labelling individual chromosomes. Using a silver-staining technique for the nucleolar organiser regions (NORs), three pairs of chromosomes, in the basic 2n=26 karyotype, have been positively identified. A series of structural chromosomal rearrangements (pericentric and paracentric inversions) affecting one pair of chromosomes involved in the numerical polymorphism is described. Significant differences exist between populations with respect to this character. These chromosomal rearrangements have the potential to reduce the level of interbreeding between the different types, and may act as isolating mechamisms between breeding groups. Structural chromosomal polymorphism is likely, therefore, to have greater significance in relation to adaptation than simple numerical variation. This finding raises important questions concerning the (cyto)taxonomic status of N. lapillus in different parts of its range.