Nickel, lead, and cadmium induce differential cellular responses in sea urchin embryos by activating the synthesis of different HSP70s

Treatment with heavy metals, such as nickel, lead or cadmium, elicits different cellular stress responses according to the metal used and the length of treatment. In Paracentrotus lividus embryos the inducible forms of HSP70 (HSP70/72) are different in molecular mass from the constitutively expressed HSP75, and they can be used as markers of cellular stress. Even a short treatment with each metal induces the synthesis of HSP70/72 which remain stable for at least 20h and differ little in their isoelectric points. Continuous treatment from fertilization with nickel or lead produces late irregular pluteus embryos, with peak HSP70/72 synthesis at blastula followed by the arrest of synthesis by pluteus. On the contrary, the same treatment with cadmium induces continuous HSP70/72 synthesis and produces irregular gastrula embryos which then degenerate. Moreover, a long treatment induces over control embryos a slight increase in the amount of constitutive HSP75 during development while lead treatment depresses constitutive HSP75 at early stages and doubles its quantity at late stages.     

Implications of temporal and spatial variability in Paracentrotus lividus populations to the associated commercial coastal fishery

Analysis of population structure and behaviour of a semi-enclosed and theoretically non-fished population of the echinoid Paracentrotus lividus at Lough Hyne marine nature reserve, Co. Cork, Ireland, showed distinct variability. Aspects of the behavioural variability in this species have significant consequences for the natural fishery harvest potential of this species. Whether or not, when and where individuals migrate to the upper surfaces of rocks varies on a local and regional scale as well as seasonally. The effect of this is apparent changes in (a) the population structure, (b) the population size and (c) the population centres of abundance. The population structure and size of the Lough Hyne population has changed substantially, as have those on a larger spatial scale, although the causative agents are debatable. Such changes are the result of large-scale mortality of adults and failure of cohort recruitment. Despite the undeniable pressures of overfishing at many localities, it seems likely there is a strong `natural' and possibly predictable element to the variability in P. lividus population size and structure. For the restoration and sustainable harvest of Irish P. lividus aspects of its behavioural ecology need to be taken more closely into consideration.     

Cryopreservation of sea urchin embryos (Paracentrotus lividus) applied to marine ecotoxicological studies

Current strategies for marine pollution monitoring are based on the integration of chemical and biological techniques. The sea urchin embryo-larval bioassays are among the biological methods most widely used worldwide. Cryopreservation of early embryos of sea urchins could provide a useful tool to overcome one of the main limitations of such bioassays, the availability of high quality biological material all year round. The present study aimed to determine the suitability of several permeant (dimethyl sulfoxide, Me₂SO; propylene glycol, PG; and ethylene glycol, EG) and non-permeant (trehalose, TRE; polyvinylpyrrolidone, PVP) cryoprotectant agents (CPAs) and their combination, for the cryopreservation of eggs and embryos of the sea urchin Paracentrotus lividus. On the basis of the CPAs toxicity, PG and EG, in combination with PVP, seem to be most suitable for the cryopreservation of P. lividus eggs and embryos. Several freezing procedures were also assayed. The most successful freezing regime consisted on cooling from 4 to −12 °C at 1 °C/min, holding for 2 min for seeding, cooling to −20 °C at 0.5 °C/min, and then cooling to −35 °C at 1 °C/min. Maximum normal larvae percentages of 41.5% and 68.5%, and maximum larval growth values of 42.9% and 60.5%, were obtained for frozen fertilized eggs and frozen blastulae, respectively.     

Harbour and coastal sediment chemistry and toxicity: a preliminary assessment of dredging activities

In a project to assess the environmental impact of dumping contaminated harbour material in a coastal marine area of the Northern Tyrrhenian Sea, sediments from different sites (harbour, dumping and uncontaminated sites) were sampled in December 1993 and February 1994. In order to evaluate sediment quality, concentrations of heavy metals (Cd, Pb, Cr and Hg) and polycyclic aromatic hydrocarbons (PAHs) were determinated and toxicity tests were carried out using the sea urchin Paracentrotus lividus. Interstitial water and the sea water overlying sediments (bedded phase and suspended phase) were tested for their effects on fertilization and embryogenesis. Sediment texture was also considered. Metal concentrations, particularly cadmium content, and PAH total concentrations, in harbour sediments were generally higher than in offshore samples. No significant reductions in fertilization were observed. However, effects on the embryonic development were evident and interstitial water toxicity was shown to be greater than either bedded or suspended exposures.     

Mifepristone affects fertility and development in the sea urchin Paracentrotus lividus

Drugs such as oral contraceptives and hormone replacement therapies are known to find their way into rivers, lakes and seas, and have the potential to affect reproduction and development of the wildlife. The knowledge of the reproductive mechanisms and their regulation in aquatic species is of fundamental importance for predicting and preventing the damage by the increasing release of such chemicals in the environment. Mifepristone, a synthetic steroid used as a drug for chemical abortion, works by blocking the effects of progesterone. Its presence in fresh and salt water has been reported, representing a danger for aquatic species. In this frame, we evaluated in both acute and chronic exposures, the effects of mifepristone on the reproductive performance of the sea urchin P. lividus. In both acute and chronic exposures, mifepristone did not affect the histological structure of the gonads. However, mifepristone administered to females caused the decrease of the percentage of normal developed plutei larvae compared with the control, whereas it did not alter sperm motility parameters and fertilization success in males. The immunohistological localization of progesterone receptor‐like immunoreactivity on the plasma membrane of oocytes and ova and the molecular weight of a progesterone receptor‐like immunoband identified by western blotting, are in agreement with a membrane progesterone receptor deducted from the genome sequence of the sea urchin Strongylocentrotus purpuratus and suggest that in P. lividus mifepristone actions may be mediated by a progesterone receptor.     

Microsatellite markers reveal shallow genetic differentiation between cohorts of the common sea urchin Paracentrotus lividus (Lamarck) in northwest Mediterranean

Temporal variability was studied in the common sea urchin Paracentrotus lividus through the analysis of the genetic composition of three yearly cohorts sampled over two consecutive springs in a locality in northwestern Mediterranean. Individuals were aged using growth ring patterns observed in tests and samples were genotyped for five microsatellite loci. No reduction of genetic diversity was observed relative to a sample of the adult population from the same location or within cohorts across years. F _ST and amova results indicated that the differentiation between cohorts is rather shallow and not significant, as most variability is found within cohorts and within individuals. This mild differentiation translated into estimates of effective population size of 90–100 individuals. When the observed excess of homozygotes was taken into account, the estimate of the average number of breeders increased to c . 300 individuals. Given our restricted sampling area and the known small-scale heterogeneity in recruitment in this species, our results suggest that at stretches of a few kilometres of shoreline, large numbers of progenitors are likely to contribute to the larval pool at each reproduction event. Intercohort variation in our samples is six times smaller than spatial variation between adults of four localities in the western Mediterranean. Our results indicate that, notwithstanding the stochastic events that take place during the long planktonic phase and during the settlement and recruitment processes, reproductive success in this species is high enough to produce cohorts genetically diverse and with little differentiation between them. Further research is needed before the link between genetic structure and underlying physical and biological processes can be well established.     

Detection of spotted fever group Rickettsia spp. from bird ticks in the U.K.

Migratory birds are known to play a role in the long‐distance transportation of microorganisms. To investigate whether this is true for rickettsial agents, we undertook a study to characterize tick infestation in populations of the migratory passerine bird Riparia riparia (Passeriformes: Hirundinidae), the sand martin. A total of 194 birds were sampled and ticks removed from infested birds. The ticks were identified as female Ixodes lividus (Acari: Ixodidae) using standard morphological and molecular techniques. Tick DNA was assayed to detect Rickettsia spp. using polymerase chain reaction and DNA was sequenced for species identification. A single Rickettsia spp. was detected in 100% of the ticks and was designated Rickettsia sp. IXLI1. Partial sequences of 17‐kDa and ompA genes showed greatest similarity to Rickettsia sp. TCM1, an aetiological agent of Japanese spotted fever‐like illness, previously described in Thailand. Phylogenetic analysis showed that Rickettsia sp. IXLI1 fitted neatly into a group containing strains Rickettsia japonica, Rickettsia sp. strain Davousti and Rickettsia heilongjiangensis. In conclusion, this research shows that U.K. migratory passerine birds host ticks infected with Rickettsia species and contribute to the geographic distribution of spotted fever rickettsial agents.     

Cost of parasitism and host immune defence in the sand martin Riparia riparia: a role for parent-offspring conflict?

Parent-offspring conflict may arise because the lifetime reproductive success of the parent is more influenced by its life span than by reproductive success during a particular reproductive event, while the fitness of an offspring depends firstly on its own survival as a juvenile and only subsequently on its own reproductive success. The naive immune system of young animals may allow offspring to be much more affected by parasites than their parents, and thus cause an initial asymmetry in a potential parent-offspring conflict. We investigated this type of conflict by assessing the health status and the immune response of parent and offspring sand martins Riparia riparia infested with manipulated loads of ticks Ixodes lividus (nests either treated with pyrethrin, water, or just visited). The prevalence and the intensity of tick infestations differed among treatments, with low tick loads in nests with the pyrethrin treatment. Ticks reduced the reproductive success of the host and increased offspring wing length. Broods with ticks had higher leukocyte concentrations and concentrations of immunoglobulins. The concentration of immunoglobulins in nestlings was negatively related to brood size and nestling tarsus length. Nestlings receiving the control treatments had a positive association between wing length and the concentration of immunoglobulins and a negative association between tarsus length and immunoglobulins. In contrast, adult sand martins did not respond to the parasite treatment in terms of immune response. Hence, the naive immune system of nestlings may be the crucial factor causing the parent-offspring conflict over costs of parasitism to be resolved to the advantage of parents that may sacrifice nestlings in heavily parasitized nests. Received: 30 March 1998 / Accepted: 5 December 1998