Mangrove Oyster Crassostrea Rhizophorae Research Articles

Cloning and detection of metallothionein mRNA by RT-PCR in mangrove oysters ( Crassostrea rhizophorae)

A semi-quantitative RT-PCR protocol was developed to directly evaluate metallothionein (MT) mRNA expression in different tissues of mangrove oysters ( Crassostrea rhizophorae), using β-Actin (ACT) as a normalizing gene. Clones with high degree of identity from partial coding sequences were obtained for both MT and ACT. Although not statistically significant, high relative accumulation of MT mRNA was observed in the digestive gland (DGG), but not in the gills, from samples collected from both control and contaminated sites. Nevertheless, MT expression was not comparable to the high levels of metal in the contaminated oysters. Results indicate that the variation in relative MT mRNA levels from different samples of the same site could be due to multiple gene copies or different MT isoform induction.

Integration of varying responses of different organisms to water and sediment quality at sites impacted and not impacted by the petroleum industry

The toxicity of surface waters and interstitial waters from sediments were determined at six study sites in Todos os Santos Bay, Bahia, Brazil, to evaluate the possibility of chronic environmental impact induced by 40 years of exposure to the local petroleum industry. Samples collected from four sites associated with the extraction, transportation and refinement of petroleum, and from two control sites, were tested at seven three-month intervals. Toxicological assays using acute mortality of brine shrimp ( Artemia salina) nauplii and chronic abnormalities of sea urchin ( Echinometra lucunter) and mangrove oyster ( Crassostrea rhizophorae) larvae were employed. Friedman non-parametric analyses of variance integrated seasonal variations in species response patterns and revealed significant differences among the study sites. Ranging the among-site variations for each organism in each sampling period, on a scale from 0.00 (minimum response) to 1.00 (maximum response), permitted the calculation of a single mean value for each species and the ordination of the sites on a qualitative scale of relative impact. Although the ordinations varied with species, the reduction of three species response patterns to a common relative scale also permitted their integration into a single multispecies ordination of the study sites. A cluster analysis of the six sites and two aquatic substrates, based on their toxicity to all three species, illustrated the similarities and differences between locations. Interstitial waters were more toxic, revealing an integrated ordination of Station 6≤Station 5≤(Station 3=Station2)≤(Station 4=Station 1). The ordination based on surface waters was Station 6≤Station 5≤(Station 2=Station 1=Station 3)<Station 4. In combination, the three procedures served efficiently for the description and inferential testing of the multispecies responses and, complemented with additional data on species diversity and chemical contamination of the sediment, confirmed the existence of chronic impact within the study area.

Integration of varying responses of different organisms to water and sediment quality at sites impacted and not impacted by the petroleum industry

Abstract The toxicity of surface waters and interstitial waters from sediments were determined at six study sites in Todos os Santos Bay, Bahia, Brazil, to evaluate the possibility of chronic environmental impact induced by 40 years of exposure to the local petroleum industry. Samples collected from four sites associated with the extraction, transportation and refinement of petroleum, and from two control sites, were tested at seven three-month intervals. Toxicological assays using acute mortality of brine shrimp (Artemia salina) nauplii and chronic abnormalities of sea urchin (Echinometra lucunter) and mangrove oyster (Crassostrea rhizophorae) larvae were employed. Friedman non-parametric analyses of variance integrated seasonal variations in species response patterns and revealed significant differences among the study sites. Ranging the among-site variations for each organism in each sampling period, on a scale from 0.00 (minimum response) to 1.00 (maximum response), permitted the calculation of a single mean value for each species and the ordination of the sites on a qualitative scale of relative impact. Although the ordinations varied with species, the reduction of three species response patterns to a common relative scale also permitted their integration into a single multispecies ordination of the study sites. A cluster analysis of the six sites and two aquatic substrates, based on their toxicity to all three species, illustrated the similarities and differences between locations. Interstitial waters were more toxic, revealing an integrated ordination of Station 6 ≤ Station 5 ≤ (Station 3 = Station2) ≤ (Station 4 = Station 1). The ordination based on surface waters was Station 6 ≤ Station 5 ≤ (Station 2 = Station 1 = Station 3) &amp;lt; Station 4. In combination, the three procedures served efficiently for the description and inferential testing of the multispecies responses and, complemented with additional data on species diversity and chemical contamination of the sediment, confirmed the existence of chronic impact within the study area.

Mercury in a northeastern Brazilian mangrove area, a case study: potential of the mangrove oyster Crassostrea rhizophorae as bioindicator for mercury

The Channel of Santa Cruz is a mangrove area in northeastern Brasil 40 km north of Recife. Until 1991 a chlor-alkali factory discharged large amounts of mercury into the main tributary of the channel, the Rio Botafogo. The objective of this study was to assess the potential of the mangrove oyster Crassostrea rhizophorae as a bioindicator for mercury in this area and to examine the influence of condition on mercury concentrations in the oysters. The investigation was carried out in the late rainy season (July to September) 1993, in the rainy season (April to June) 1994 and in the dry season (November/December) 1994. At 11 stations in the channel, mangrove oysters, surface sediments and suspended matter were sampled, representing different compartments of the system. The distribution of mercury in the Channel of Santa Cruz exhibited for all compartments the same distinct spatial pattern with maxima in the Rio Botafogo. Seasonal variations were small and revealed no clear tendencies. In addition, mangrove oysters were transplanted from more contaminated stations to less contaminated stations and vice versa. These experiments were designed to study the oysters' capability to adjust their mercury concentrations to a changing bioavailability of mercury. The transplantation experiments suggest that the oysters are capable to adjust to changing ambient mercury availability within a few months. The transplantation experiments also revealed the importance of condition changes on the mercury concentration of the oysters. This factor should not be ignored during pollution studies. However, condition had apparently no strong influence on the spatial or seasonal mercury variations of the oysters. The mangrove oyster is a suitable bioindicator for long-term changes in mercury availability.

Stress protein accumulation as an indicator of impact by the petroleum industry in Todos os Santos Bay, Brazil

Abstract The relative concentrations of stress proteins in juvenile mangrove oysters (Crassostrea rhizophorae), from six study sites in Todos os Santos Bay, Bahia, Brazil, were used to evaluate the possibility of chronic environmental impact induced by 40 years of exposure to the local petroleum industry. Replicated tissue samples from oysters at four sites associated with the extraction, transport and refinement of petroleum, and from two control sites, were used for stress protein (60 kDa) determination. The relative levels of stress proteins were statistically compared by standard methods. Friedman nonparametric analysis of variance, followed by multiple comparisons among samples, revealed significant differences in stress protein levels. Oysters from sites associated with the extraction and transport of petroleum had the highest relative concentrations of stress proteins, while the control areas revealed minimum concentrations. Samples from the refinery site, where oyster populations were severely reduced, did not differ from the control sites. Comparisons with parallel studies on the toxicity of aquatic substrates at the same sites revealed that stress protein analyses were useful in evaluating chronic environmental impact, within the tolerance limits of C. rhizophorae, but that the stress response diminished significantly when conditions approached the lethal limits for this species. The stress protein response appears to serve as a valid biomonitoring method under chronic, sublethal exposures, before biological responses become evident at the organismic or population levels, but may not serve well when the stressor intensity is at or near the lethal tolerance level.

Stress protein accumulation as an indicator of impact by the petroleum industry in Todos os Santos Bay, Brazil

The relative concentrations of stress proteins in juvenile mangrove oysters ( Crassostrea rhizophorae), from six study sites in Todos os Santos Bay, Bahia, Brazil, were used to evaluate the possibility of chronic environmental impact induced by 40 years of exposure to the local petroleum industry. Replicated tissue samples from oysters at four sites associated with the extraction, transport and refinement of petroleum, and from two control sites, were used for stress protein (60 kDa) determination. The relative levels of stress proteins were statistically compared by standard methods. Friedman nonparametric analysis of variance, followed by multiple comparisons among samples, revealed significant differences in stress protein levels. Oysters from sites associated with the extraction and transport of petroleum had the highest relative concentrations of stress proteins, while the control areas revealed minimum concentrations. Samples from the refinery site, where oyster populations were severely reduced, did not differ from the control sites. Comparisons with parallel studies on the toxicity of aquatic substrates at the same sites revealed that stress protein analyses were useful in evaluating chronic environmental impact, within the tolerance limits of C. rhizophorae, but that the stress response diminished significantly when conditions approached the lethal limits for this species. The stress protein response appears to serve as a valid biomonitoring method under chronic, sublethal exposures, before biological responses become evident at the organismic or population levels, but may not serve well when the stressor intensity is at or near the lethal tolerance level.

Aquatic and aerial respiration of crassostrea rhizophorae

1. I. Rates of oxygen consumption in water (.VO 2w) and air (.VO 2A) were determined for the mangrove oyster Crassostrea rhizophorae. 2. 2. The ratio of aerial: aquatic .VO 2 (.VO 2A: .VO 2W) was 0.43, suggesting relatively high aerobicity during the first 2 hr of aerial exposure. 3. 3. Air-gaping facilitates .VO 2A and the degree of valve gape is proportional to .VO 2 in air and water. 4. 4. Previous studies indicating high survival rates in air are likely to be accounted for, in part, by aerial oxygen consumption and not an overt resistance to hypoxia or asphyxia.

Influence of gamete density, salinity and temperature on the normal embryonic development of the mangrove oyster Crassostrea rhizophorae Guilding, 1828

Laboratory experiments were undertaken to determine the optimal environmental conditions and some of the other factors concerned in the development of Crassostrea rhizophorae embryos. Critical variables such as the number of spermatozoa per ovocyte during fertilization, the time of fertilization after gamete liberation, egg density, temperature and salinity were related to the proportion of normal D-larvae of C. rhizophorae in the resulting broods. The highest proportion of normal D-larvae was obtained at concentrations of 500–5000 spermatozoa/ovocyte, under conditions of 25‰ salinity at 25 ± 1°C. The optimal density of eggs, for the production of normal D-larvae, was 10 4−4 × 10 4 ovocytes/l. If fertilization was delayed for more than 45 min after liberation of spermatozoa the proportion of normal D-larvae was greatly reduced. The experiments demonstrated that the temperature for developing embryos should be below 30°C. At 20 and 25°C there was a high proportion of normal D-larvae 24 h after fertilization. The ideal salinity for embryonic development in C. rhizophorae was 25–37‰. Below a salinity of 16‰, less than 2.5% of the D-larvae were normal.

Determinación del tamaño comercial de la ostra de manglar, Crassostrea rhizophorae (Guilding, 1828) en sistema de cultivo suspendido en Estero Viscaya, Limón, Costa Rica

A pilot study of the mangrove oyster (Crassostrea rhizophorae), cultured in a raft system in Estero Viscaya, Limon, Costa Rica, between January and June, 1982 showed that the condition index reached the highest percentage at age V (for dry weight) and age IV (for wet weight). Strong correlations were observed between meat weight, shell weight (dry and wet), shell cavity fluid weight and yield of meat.The minimum commercial size for the fresh market oyster was determined by the analysis of relationships obtained between shell cavity fluid weight, meat and shell weight (dry and wet) and yield of meat to size, and age. The size of 60 mm total length and 23 g weight was reached in five months.

Changes in the condition index for mangrove oysters ( Crassostrea rhizophorae) from Todos os Santos Bay, Salvador, Brazil

The condition index was calculated for two samples of 600 C. rhizophorae taken from Jacuruna farm in September–October 1977 (spawning period) and December 1977–January 1978 (post-spawning period). There was a significant difference ( P ≤ 0.05). Over the size range 2.1 to 10.0 cm (height) the condition index ranged from 59.0 ± 16.2 to 71.8 ± 30.5 for the spawning period, but was only 27.1 ± 10.2 to 43.9 ± 33.0 for the post-spawning period. The size class 4.1 to 6.0 cm gave the best commercial yields and was considered more suitable for the shucked oyster than the fresh oyster market.

Acute toxicity of selected heavy metals to mangrove oyster Crassostrea rhizophorae.

The lethal concentration (LC50) values of four heavy metals for the mangrove oyster Crassostrea rhizophorae were determined by the static bioassays. The test animals were collected from Laguna Grande, Gulf of Cariaco, Sucre State, Venezuela, and were acclimated in the laboratory condition for two weeks prior to bioassays. Acclimation temperature and salinity were 23.5°C and 36‰, respectively. The 216-h LC50 values (mg/l) determined by probability-logarithm transformation were 0.6 for cadmium (II), less than 1 for copper (II), 7 for chromium (VI), and 16 for zinc (II). The above indicates that the order of toxicties of metals tested to the mangrove oyster is cadmium>copper>chromium>zinc.