Effects of fertilization and development of the common mussel Mytilus edulis after long-term exposure to a nonionic surfactant

Common mussels (Mytilus edulis L.) were exposed over a 5-month period to low-level concentrations (0.5 to 1.5 ppm) of a nonionic surfactant. Upon maturation at the end of this period, spawning ability was examined. Fertilization occurred at low-level concentrations (0.1 to 2.0 ppm) of the surfactant, and was most successful for gametes from the long-term controls and the highest long-term concentration (1.5 ppm). Inhibited or delayed larval development was observed, related to the concentration gradient of the short-term exposures. Gametes from mussels long-term exposed to the surfactant were more sensitive than those from the long-term control.     

Effects of the insecticide sevin and its first hydrolytic product, 1-naphthol,on some early developmental stages of the bay mussel Mytilus edulis

Six developmental stages of the bay mussel Mutilus edulis, from fertilization to 32 h after fertilization, and also unfertilized eggs, were exposed for 1 h to different concentrations of the insecticide Sevin and its first hydrolytic product, 1-naphthol. After exposure, the larvae or eggs were separated from the pesticide solution and returned to clean water. At 48 h after fertilization, the numbers of normal and abnormal larvae were determined and 1-h EC₅₀ values (the effective concentrations that caused anomalous development of 50% of the test animals) were calculated. The most sensitive developmental stage was the one that occurred shortly after fertilization at the time of appearance of the first polar body. Thereafter, sensitivity decreased as age increased. The EC₅₀ of Sevin for the first polar body stage and 32-h stage were 5.3 and 24.0 mg/l of Sevin, respectively. The EC₅₀ of l-naphthol for the first polar body stage was 5.2 mg/l. Effects of the toxicants on development were characterized by disjunction of blastomeres, a reduction in the rate of development, and asynchronous and unaligned cleavages.     

Sensitivity of veliger larvae of Mytilus edulis and mussel of various sizes to chlorination

The blue mussel Mytilus edulis is one of the dominant fouling organisms in cooling water systems. In this work, how veliger larvae and different size groups of the mussels responded against chlorine dosage was examined. Veliger larvae mortality was studied at different residual chlorine concentrations (0.05–0.5 mg L^?1), and it was found that a chlorine dose of 0.5 mg L^?1 is 4 times as effective as 0.05 mg L^?1 and twice as effective as 0.1 mg L^?1. Mortality of 100% for three size groups (1.4, 14, and 25 mm) and relative physiological activities of two size groups (14 and 25 mm) were observed. The exposure duration for 100% mortality of mussels decreased with the increasing residual chlorine concentration (0.1–4.0 mg L^?1). Mussel size was also found to be an important factor, considering that the continuation times for mussel mortality were 28 h for the 1.4 mm and 410 h for the 25 mm size groups. All size groups showed progressive reduction in physiological activities, such as oxygen consumption, foot activity, and byssus thread production with increasing chlorine dose (0.05–1.0 mg L^?1); the two data-sets were strongly correlated with each other. The results of this study should be of significance for optimizing the chlorine content, and minimize the environmental threat to industries where mussels are the dominant fouling organisms.     

有机氯农药硫丹的生殖毒性及其机制研究进展

硫丹作为一种广谱有机氯农药,在农业区域周边的土壤和水体中都存在较高残留,2011年被斯德哥尔摩公约列入持久性有机污染物(POPs)名单。硫丹已被证实对神经系统、心血管系统、肝、肾等具有毒性作用,关于其生殖毒性的研究很多,但潜在机制尚不完全清楚。本文总结了硫丹导致的不同动物的生殖毒性,并从生殖器官和生殖细胞损伤、氧化应激以及DNA损伤、生殖细胞周期阻滞及细胞凋亡等方面,对近年来硫丹生殖毒性及其作用机制研究进展进行综述,并对其中存在的问题进行讨论,以期有助于深入了解硫丹的毒性效应。     

Effects of copper on the latency of lysosomal hexosaminidase in the digestive cells of Mytilus edulis

Mytilus edulis collected from Tomales Bay, California, USA, during mid-winter 1979 were exposed to increased concentrations of dissolved copper under controlled laboratory conditions. A dose-dependent reduction in the latency of lysosomal hexosaminidase activity in digestive cells was induced after a 30 d exposure to copper. The half-time of the hexosaminidase staining reaction in sections of digestive gland from control mussels was 15.5 min; for mussels exposed to 25, 50, and 75 g Cu l^-1 it was 11.8, 8.5 and 5.5 min, respectively. In addition, the dyecoupled reaction product was seen earlier in sections from individuals exposed to 50 and 75 g Cu l^-1 (after 30 s) and 25 g Cu l^-1 (1 min) than in sections from control individuals (2.5 min). Copper accumulations were demonstrated histochemically to have the same distribution as the hexosaminidase reaction product, indicating that copper is sequestered in lysosomes. Copper concentrations in digestive gland tissue, were related to the concentrations of copper in the water to which the mussels were exposed.     

Photoperiodic regulation of gametogenesis and gonadal growth in the sea star Pisaster ochraceus

A photoperiod regime 6 mo out of phase between December 1978 and August 1980 resulted in gametogenesis, gonadal growth, and spawning in laboratory-maintained sea stars [Pisaster ochraceus (Brandt)] 6 mo out of phase with individuals in the field or laboratory on normal celestial photoperiods at Santa Cruz, California (USA). The seasonal fluctuation of pyloric cecum size also was shifted when the sea stars were held on the out-of-phase photoperiod regime. Phase shift of all these events was evident within 6 to 9 mo. Long daylengths (or short nightlengths) in spring and summer apparently synchronize or entrain the initiaion of gametogenesis and gonadal growth in fall.     

Effects of oil pollution on the freezing tolerance and solute concentration of the blue mussel Mytilus edulis

Exposure of blue mussels (Mytilus edulis L.) to oil-polluted sea water for 7 d in the laboratory did not affect their body fluid concentrations of inorganic ions and free amino acids. Mussels exposed to-4°C for 12 h did not freeze, whereas freezing occurred invariably in mussels exposed to-7°C or lower temperatures for the same period. Following freezing at-10°C, oil polluted mussels resumed normal activity considerably more slowly than unpolluted ones, but oil-polluted as well as unpolluted mussels showed normal activity 3 h after thawing. Freezing at-15°C was invariably lethal to individuals of both groups. One possible explanation of the delayed recovery of oil-polluted mussels frozen at-10°C may be that oil components had become concentrated to toxic levels as the amount of solvent water diminished during freezing.     

Seasonal variation in uptake and depuration of anthracene by the brackish water clam Rangia cuneata

Rangia cuneata were collected every six weeks for one year from February 1984 to January 1985 at the mouth of the Dog River, Alabama, USA and dosed with 200 ppb [9–¹⁴C] anthracene at 10, 20, and 30°C. Uptake rates of [9–¹⁴C] anthracene measured over a 15-h period were not significantly different (P>0.05), but depuration rates measured over a two-week period were significantly higher with increasing temperature. The seasonal changes in rates were related to the annual changes in biochemical composition of the clams associated with the reproductive cycle. Lipid levels were nearly constant over the year, averaging 88.0±2.0 mg/g dry wt. The level of carbohydrates peaked in July, a month before the maximal gonad index, and decreased steadily through September during spawning. The level of proteins increased from 76.6 mg/g dry wt prior to spawning to 138.3 mg/g dry wt after spawning. Uptake rates were highest in late summer during the peak of gametogenesis and decreased during spawning in the fall. Depuration rates remained low from March through August and rapidly increased to the highest levels during the fall spawning period. The results suggest that the stage of the reproductive cycle, with its associated biochemical changes, and temperature play an important role in the pattern of accumulation and release of anthracene in R. cuneata.     

水体和甘蓝及土壤中毒死蜱残留检测方法

研究运用不同的样品前处理方式,在装配火焰光度检测器的气相色谱(GC-FPD)上检测,建立了有机磷杀虫剂毒死蜱在水样、土壤和甘蓝中的残留测定方法.研究表明,不同样品中的毒死蜱残留采用本文中介绍的前处理方法是可行的,用石油醚盐析提取和净化水样中毒死蜱,采用丙酮振荡提取甘蓝中毒死蜱,选用索氏提取法提取土壤中毒死蜱,并经液液分配净化后,采用OV-101大口径毛细管柱(30 m×0.53 mm×1.0μm),在装配火焰光度检测器(FPD和磷滤光片)的气相色谱上测定.该分析方法下,毒死蜱的保留时间为1.74 min,线性范围在1.0×10-11—1.0×10-8g之间,其线性相关系数为0.9998,最小检出量为2.0×10-12g.在设定的较低添加浓度的条件下,毒死蜱在水样、土壤与甘蓝上的添加回收率为80%—120%,变异系数均小于5%.该分析方法灵敏、准确、操作简便,适合水样、甘蓝和土壤中低浓度毒死蜱的残留检测.     

Metallothioneins and lysosomes in metal toxicity and accumulation in marine mussels: the effect of cadmium in the presence and absence of phenanthrene

It has been confirmed that metallothioneins play an important role in the accumulation of cadmium (Cd) in the digestive gland cells of mussels (Mytilus galloprovincialis Lam.). The content of Cd in the tissue of mussels exposed for 9 d to the metal (estimated dosage of 180 g Cd mussel^-1 d^-1) was 66.2 ppm. This value is about the same as the metal content found in the digestive gland of Cd-exposed mussels kept in clean water for a recovery period of 28 d. At the end of the recovery period, however, the Cd bound to thionein had increased by approximately 250%. Our data demonstrate that the stability of lysosomes, a biological parameter adopted as a cellular stress index, is extremely low in mussels exposed to Cd for 9 d, but returns to control values in the digestive gland cells of mussels allowed to recover for 28 d in uncontaminated sea water. At this point most of the Cd present in the cytosol is bound to thionein. These data demonstrate the importance of metallothionein induction in the reduction of the cytotoxic effects exerted by high levels of Cd accumulation. The results of tests designed to clarify the reasons for the long biological half-life of Cd demonstrated that, in the digestive gland of mussels, the lysosomes are not able to eliminate Cd either bound to insoluble thionein polymers or to lipid peroxidation products such as lysosomal lipofuscin, both of which are apparently involved in the elimination of copper. The absence of these two mechanisms of metal sequestration and elimination via excretion of residual bodies (tertiary lysosomes) is in agreement with the persistence of cadmium in the digestive gland of mussels. Finally, the results also demonstrate that simultaneous exposure of mussels to Cd and phenanthrene, an established lysosomal membrane destabilizer, did not significantly alter the accumulation of Cd or the kinetics of the metal in mussels.     

Toxizität und anreicherung von blei bei der miesmuschel Mytilus edulis im laborexperiment

In a laboratory experiment, conducted over 130 days, three batches of a total of 100 common mussels, Mytilus edulis, were maintained in media containing different lead concentrations. Two vessels served as controls. There was no acute injury to the mussels; but, over an extended period of time, a marked increase in mortality occurred which was related to the lead concentration in the medium. The median lethal time (LT₅₀) was computed to be 218 days for the control, 150 days with 0.5 mg Pb/l in the medium, 129 days with 1 mg/l, and 105 days with 5 mg/l. Quantitative analyses of the soft parts of M. edulis by flameless atomic-absorption-spectrophotometry revealed a distinct accumulation of lead. From a natural lead content of 8.4 μg Pb/g dry weight, the lead concentration increased to 12,840 μg/g at 0.5 mg/l, to 20,770 μg/g at 1 mg/l and to 39,830 μg/g at 5 mg/l. The ratio of the concentration of lead in the soft parts of M. edulis to the concentration in the medium remained in the same order of magnitude both under laboratory conditions using high lead concentrations and under in situ lead levels. Over a period of 130 days, lead uptake expressed as percentage of lead offered was 10.9% at 0.5 mg/l, 9.5% at 1 mg/l, and 3.4% at 5 mg/l, respectively.     

Seasonal variation of nitrate-N in surface and ground-waters of South Western Nigeria: a preliminary survey

Two surveys of nitrate-N concentrations in surface and ground water in Ogun and parts of Lagos and Oyo States of south-western Nigeria were undertaken between October 1997 and December 1998, and between July 2000 and May 2001 (covering both dry and rainy seasons). The study was conducted to ascertain the extent of nitrate-N pollution of the surface/ground water in some parts of the three states. Seventy-two water points (33 rivers/streams, 21 wells and 18 boreholes) were sampled three times during each of the two seasons. Nitrate-N was detected in all the river/stream samples analysed with concentrations ranging from 0.5 to 15.3 mg/l and 1.0 to 7.7 mg/l during the rainy and dry seasons, respectively (average value 2.7 and 2.4 mg/l for rainy and dry season, respectively). 98.5% of the rivers/streams sampling points contained nitrate-N in amounts equal to or less than 10 mg/l. 88.1% of wells and 97.2% of boreholes had a nitrate-N content less than 5 mg/l. Nitrate-N concentrations in the sampled wells ranged from 1.4 to 7.4 mg/l and 1.1 to 6.0 mg/l during the rainy and dry seasons, respectively (average value 2.6 and 2.2 mg/l, respectively). The sampled boreholes had a lower nitrate-N concentration ranging from 0.1 to 5.2 mg/l and from below the detection limit to 5.0 mg/l during the rainy and dry seasons, respectively (average value 1.8 and 1.6 mg/l, respectively). Nitrate-N concentrations in boreholes were below detection limit in 22% of the samples. Generally, for most of the sampling points, nitrate-N concentrations were slightly higher during the rainy season compared with the dry season. The present results indicated that nitrate-N concentrations in all the water points (except one) were below the World Health Organization (WHO) maximum acceptable limit in potable waters (10 mg/l). Therefore, contamination of the surface and ground water of the study area is not indicated. This study provides background data against which future changes in nitrate-N concentrations of surface and ground waters in the study area can be measured.     

Analytical survey of arsenic in geothermal waters from sites in Kyushu,Japan, and a method for removing arsenic using magnetite

The objective of this study was to survey the cation and anion contents of geothermal waters to gather fundamental information on geographical variations. Sixteen sites in hot spring areas on the island of Kyushu in Japan were studied. The study focused on the arsenic content of the samples. Very high arsenic concentrations (more than 0.1 mg/l) were detected in most of the geothermal waters sampled. High contents of boron and fluoride (more than 1.0 mg/l) were also detected in some samples. Arsenic removal was performed on a laboratory scale using columns packed with a magnetite-type adsorbent. The reduction of arsenic contamination to a concentration of less than 0.01 mg/l could be achieved in the early stages of adsorption (bed volume = 200).     

Lead uptake from sea water and food,and lead loss in the common mussel Mytilus edulis

Common mussels, Mytilus edulis (shell length 19 to 21 mm, average dry weight 30 mg) were maintained for 6 weeks in sea water containing different concentrations of lead (0.005 to 5 mg · l^-1). The lead concentration in the mussels' whole soft parts was analysed at different times during the experiment. A constant rate of lead uptake, linearly dependent on the lead concentration of the medium, was observed. Thus, the temporal change of the concentration factor is also linear (regression coefficient 149.9 daily). Rate of lead loss, measured after transferring the mussels into natural sea water, is linearly dependent on the original lead concentration in the soft parts. Rates of uptake and loss in large mussels (shell length 45 to 55 mm, average dry weight 750 mg) are less than those in small mussels (shell length 19 to 21 mm, average dry weight 30 mg). During a much more extended experimental period, adjustment to a steady state is expected to occur; rates of lead uptake and loss are then non-linear. Lead uptake by individual organs (kidney, gills, adductor muscle, digestive gland, foot, mantle with gonads) of large M. edulis (shell length 45 to 55 mm, average dry weight 750 mg) was analysed in 2 test series. In the test series medium, the mussels were kept in a seawater medium containing 0.01 mg. Pb.l^-1. In the test series food, the mussels were kept in natural sea water but fed with the green algae Dunaliella marina containing lead (approximately 600 g.g^-1 dry weight). The lead quantity given per mussel per day was about 2 g in both test series. Within 35 days, the mussels of test series medium took up 29% of the total amount of lead given, those of test series food took up 23.5%. In all organs, lead concentration increased, but rates of uptake differed; the kidney displayed by far the highest rate of uptake. With these physiological properties M. edulis is an ideal indicator organism for lead pollution in the marine environment. A biologic calibration curve, the relationship between lead concentration in the mussels' whole soft parts at equilibrium and lead concentration in sea water, is presented.This paper forms part of a doctoral thesis in biology at Hamburg University     

Light and electronmicroscopic studies of the acute and long-term toxic effects of N-nitrosodipropylamine and N-methylnitrosurea on the marine mussel Mytilus edulis

The acute (1) and long-term (2) toxic effects of N-nitrosodipropylamine (NDPA) and N-methylnitrosurea (NMU) were studied by light and electronmicroscopy following injection of the chemicals into the foot of the mussels Mytilus edulis (L.) (1) Mussels reveived one injection of NDPA at concentrations of 0.25, 0.5, 1.0, and 2.0 mg NDPA mussel^-1, and one injection of NMU at concentrations of 0.25, 0.5, 1.0, and 4.0 mg NMU mussel^-1. Within 12d, necrosis of the epithelial lining of the digestive diverticula took place, and the vesicular connective tissue in the digestive diverticula were heavily infiltrated by eosinophilic granular leucocytes. (2) Mussels received four weekly injections of 0.5 mg NDPA mussel^-1, and 0.5 mg NMU mussel^-1. NDPA-exposed mussels were examined for a period of 17 weeks, and NMU-exposed mussels were examined for a period of 24 weeks. Both chemicals produced progressive tissue damage, characterized by destruction of digestive tubules and ducts in the digestive diverticula. Destroyed tubules and ducts were replaced by collagenous scars, and granulocytomas were frequently seen.     

Effect of curacron toxicity on the total serum protein content of Cyprinus carpio

An experiment was conducted on freshwater fish Cyprinus carpio to study the effect of the pesticide curacron on total serum protein. Curacron is an organophosphate pesticide and used by the farmers to protect their crops. This pesticide reaches the aquatic ecosystem by direct or indirect means and affects aquatic fauna. LC50 for curacron for C. carpio was calculated by the log-dose/probit regression line method and found to be 0.38?ppm at 96?h. Three sub-lethal concentrations (0.1, 0.01, and 0.001?mL?L^?1) were selected to expose the fish for 1, 7, 14, and 21days. Changes in total serum protein were observed at all pesticide concentrations and exposure periods. Total serum protein was decreased from control. At 1 and 7 days, the decrease was quantitative at all concentrations, while at 14 and 21 days, the fall was significant at all concentrations. Hence, human population may be at risk by consuming these contaminated fish.     

铅暴露与排放对中华鲟幼鱼血液中ALT、AST活力的影响

采用水溶液静态置换法,从中华鲟(Acipenser sinensis)受精卵发育至96 h开始,研究了其在0(对照组)、0.2、0.8和1.6mg·L~(-1) Pb~(2+)水溶液中暴露16周,随后排放6周,对中华鲟幼鱼血液中ALT、AST活力的影响.结果显示:Pb暴露后幼鱼血液中的ALT和AST活力均表现为随Pb暴露剂量增加而升高的趋势,1.6mg·L~(-1)组ALT活力与其它各组比较呈极显著差异(P<0.01);0.8和1.6mg·L~(-1)组AST活力与对照组比较分别呈显著差异(P<0.05)和极显著差异(P<0.01). Pb排放后,各暴露组血液中ALT活力降低至对照组水平(P>0.05);1.6 mg·L~(-1)组的AST活力依然较高.超出对照组近2倍(P<0.01).对照组血液的AST/ALT值在2.24～2.32之间;随Pb质量浓度增加,暴露后AST/ALT值呈增加趋势.Pb排放后AST/ALT值降低,但1.6 mg·L~(-1)组与其余各组比较仍维持较高值(P<0.05).初步认为,0.2 mg·L~(-1)和0.8 mg·L~(-1) Pb~(2+)暴露导致中华鲟幼鱼肝细胞不同程度受损,经Pb排放后,轻度受损的组织细胞能够恢复.血液中的AST/ALT值在判断鱼类组织损伤中也具有重要意义.     

Accumulation of 14C-1-naphthalene by an oceanic and an estuarine copepod during long-term exposure to low-level concentrations

Accumulation of the bi-cyclic aromatic hydrocarbon ¹⁴C-1-naphthalene in adult female Calanus helgolandicus Claus and adult female Eurytemora affinis Poppe in sea water concentrations of hydrocarbon ranging from 0.2 to 992 g/l was studied during exposure periods of up to 15 days as part of an investigation of the possible effects on marine zooplankton of persistent exposure to low levels of petroleum hydrocarbons. With both species the body levels of radioactivity increased rapidly during the first few days of the exposure period, but after exposure for 7 to 8 days to sea water containing 50 g hydrocarbon/l an equilibrium condition was approached; in some experiments where E. affinis was exposed to 1.0 and 10 g hydrocarbon/l for 15 days there was no further increase in body levels of radioactivity after 7 to 8 days. Using a low concentration of hydrocarbon (1 g/l), the quantity of radioactivity accumulated after 10 days was found to be nearly fifty times greater in the smaller species, E. affinis, than in C. helgolandicus, when expressed in terms of body weight. After they had been exposed to the hydrocarbon for several days the copepods contained a considerable proportion of radioactivity that was no longer identifiable as naphthalene and was presumably present as metabolites. Radioactivity accumulated in the copepods after several days was rapidly lost after they were transferred to uncontaminated sea water: e.g. C. helgolandicus lost nearly 90% of its body level of radioactivity in 24 h. Thereafter the rate of loss was greatly reduced, and 5% of the original body level of radioactivity still remained in the copepods at the end of 11 days. Experiments on the breakdown of naphthalene added at low concentrations to sea water samples containing natural microbial populations indicated degradation rates of 0.1 to 0.2 g/l/24 h in oceanic water, and 2.6 g/l/24 h in inshore water samples. The results are discussed in terms of the possible transfer of hydrocarbon to a higher trophic level in areas subjected to constant low-level inputs of petroleum hydrocarbons.     

The effect of seasonality on oxidative metabolism in the sea urchin Loxechinus albus

The objective of the present study was to investigate seasonal variations in the oxidative metabolism of the sea urchin Loxechinus albus gonads. The reported spawning period for this species is from September to November. Lipid radical content showed non-significant changes upon the seasons. Ascorbyl radical content and the content of α-tocopherol were lower in samples collected in spring and summer as compared to the values in winter-collected animals. Ascorbate content decreased in samples collected in fall as compared to those collected in winter. For the lipophilic compartment, the lipid radical content/α-tocopherol content ratio is an indicator of oxidative stress. This index increased significantly in tissues during spawning as compared to the values in samples collected during winter. The ascorbyl content/ascorbate content ratio is an indicator of oxidative stress for the hydrophilic milieu. A significant decrease by 66% was determined in tissues from gonads of animals collected in summer as compared to values in animals collected in winter. The data reported here suggest a different profile of response against oxidative stress at the lipophilic and hydrophilic milieus in L. albus gonads.     

Local extinction of a foundation species in a hypoxic estuary: integrating individuals to ecosystem

We integrated across individual, population, community, and ecosystem levels to understand the impact of environmental stress by tracking the foundation species Mytilus edulis in the hypoxic estuary Narragansett Bay, Rhode Island, USA. Our initial surveys revealed that the mussels occurred in nine extensive (2-28 ha) dense (814-9943 individuals/m2) subtidal reefs that attracted a diverse suite of predators (sea stars, crabs, gastropods). Hypoxia occurred in the summer of 2001, and a mussel transplant experiment revealed overall reduced growth rates of individuals, and higher mortality rates among larger mussels. At the population level, large decreases in densities and cover of mussels were correlated with dissolved oxygen concentrations, leading to extinction at one site and reductions of over an order of magnitude at others. Within one year, seven of the eight remaining populations were edged to extinction, and the previously extinct population was recolonized. At the community level, a predator exclusion experiment indicated that predation was an unimportant source of mussel mortality during the hypoxic period, in part due to the emigration of sea stars, as predicted by the Consumer Stress Model. However, mussels were too intolerant to hypoxia to have a net benefit from the predation refuge. The seasonal (summer) occurrence of hypoxia allowed sea stars to return following a lag, as predicted by a stress return time model, and the resumption of predation contributed to the subsequent extinction of mussel populations. At the ecosystem level, the initial filtration rate of the mussel reefs was estimated at 134.6 x 10(6) m3/d, equivalent to filtering the volume of the bay 1.3 times during the 26-d average residence time. That function was reduced by >75% following hypoxia. The effect of hypoxia on each level of organization had consequences at others. For example, size-specific mortality and decreased growth of individuals, and reduced filtration capacity of reefs, indicated a loss of the ability of mussels to entrain planktonic productivity and potential to control future eutrophication and hypoxia. Our study quantified patterns of loss and identified pathways within an integrative framework of feedbacks, summarized in a conceptual model that is applicable to similar foundation species subjected to environmental stress.