Effects of temperature and salinity on the larvae of two species of rhizocephalan (Crustacea: Cirripedia)

Summary

Responses of larvae of two rhizocephalan species to changes in seawater temperature and salinity were studied under laboratory conditions. Peltogasterella gracilis parasitizes the hermit crab Pagurus pectinatus, which occurs at stable salinity and gradually changing temperature in summer. Sacculina polygenea is a parasite of the crab Hemigrapsus sanguineus, which lives in the intertidal zone in summer where salinity and temperature can fluctuate during the day. The development of both species is comprised of five naupliar stages and the cyprid stage, and it was considered successful if more than 50% of the nauplii attained the cyprid stage. P. gracilis nauplii successfully developed at 12–20°C and 30–34‰, but at 22°C successful development occurred in a narrower salinity range (32–34‰). All nauplii died both at 25°C and in 26‰. S. polygenea nauplii successfully reached the cyprid stage at higher temperatures (18–25°C) and a wider salinity range (18–34‰) than P. gracilis nauplii, but at 12°C and 16‰ larval development of S. polygenea was suppressed. Under favorable conditions, naupliar development lasted 3.5 days in P. gracilis and 2–3 days in S. polygenea. The cyprids of both rhizocephalan species demonstrated a greater resistance to temperature and salinity changes than nauplii. However, P. gracilis cyprids were active in a narrower salinity range (16–34‰), as compared to S. polygenea cyprids (8–34‰). Under favorable conditions the cyprids of both species survived for 6 to 10 days.     

The use of biomarkers in the antioxidant responses of Daphnia magna to the acute and chronic exposure to no. 20 diesel oil and 2,4-dichlorophenol

Abstract

The effects of no. 20 diesel oil exposure, 2,4-dichlorophenol (2,4-DCP) exposure and combined exposure on the antioxidant defences of Daphnia magna have been studied systematically for the first time. Daphnia magna was exposed for 1 day or 10 days to several concentrations of 0, 0.005, 0.01, 0.05, 0.1, 0.5 or 1.0 mg L^?1 solutions. Antioxidant defences consisting of the levels of reduced glutathione (GSH) and glutathione disulfide (GSSG) and activities of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), selenium dependent glutathione peroxidase (Se-GPx) and glutathione S-transferase (GST) of daphnids were determined to evaluate their protective roles and to analyse the occurrence of oxidative stress. The possible antioxidant defence mechanisms are discussed. Furthermore, GST can be a potential biomarker and an early-warning index for the pollutants in waters in that GST responded sensitively to 1 day and 10 days of exposure to diesel oil and 2,4-DCP and 10 days of combined exposure. Crossover comparisons showed an antagonistic action about the no-observed-effect concentration (NOEC) against Daphnia magna, which needs further studies.     

Comparison of nutritional status of field and laboratory reared Balanus amphitrite Darwin (Cirripedia: Thoracica) larvae and implication of starvation

Experiments were carried out to evaluate the influence of rearing temperature and food concentration (20 and 30 °C, 1×10⁵ and 2×10⁵ cells ml⁻¹) on the starvation threshold and nucleic acid content of the larvae of Balanus amphitrite. The larvae were also field-reared using micro-enclosures. Laboratory-reared larvae were larger in size than the field-reared larvae. An increase in size, DNA content and instar index of the starved II instar larvae was observed indicating that the absence of food may not be fatal to this early instar. The temperature at which larvae were raised and the food concentration had variable influence on the capacity to withstand starvation. Exposure to increased temperatures during starvation eliminated the effect of doubling food concentration during their feeding period prior to starvation. The larvae reared at 20 °C had comparatively lower nucleic acid content. The laboratory-reared larvae had ca. 1.7 times greater RNA:DNA ratio than larvae raised at comparable temperature in the field.     

冬青油与肉桂油对淡色库蚊的生物活性

为进一步明确冬青油（wintergreen oil）与肉桂油（cinnamon oil）对蚊虫的生物活性, 本研究采用浸液法、 “Y”型嗅觉仪法和密闭三角瓶熏蒸法, 分别测定了两种精油对淡色库蚊Culex pipiens pallens幼虫的毒杀作用以及对成虫的驱避和熏杀活性。结果显示： 肉桂油和冬青油对淡色库蚊幼虫均具有较强的毒杀作用, 处理24 h的LC₅₀分别为71.87 mg/L和 102.83 mg/L。在0.5 μL的供试剂量下, 冬青油与肉桂油在20 min内对淡色库蚊的驱避率均在80%以上, 显示了较好的驱蚊活性。冬青油对淡色库蚊具有明显的熏蒸击倒作用, 12 μL/L浓度下的KT₅₀为3.97 min; 而肉桂油则具有较好的熏蒸致死活性, 熏蒸5 h的LC₅₀ 为0.31 μL/L。冬青油与肉桂油按1∶1体积比混配后对淡色库蚊表现出较好的击倒和致死效果。冬青油和肉桂油既对淡色库蚊幼虫具有较强的毒杀作用, 又对淡色库蚊雌成虫表现出较好的驱避和熏杀活性, 具有开发成为植物源蚊虫防控剂的潜力。     

The effect of salinity on respiratory metabolism,survival and moulting in the first zoea of Macrobrachium amazonicum (Heller) (Crustacea,Palaemonidae)

Survival, duration of intermoult cycle and respiratory metabolism were evaluated as a function of salinity (0–35‰; 25° C) in early zoeae of the cinnamon shrimp, Macrobrachium amazonicum. Zoeae are extremely resistant to salinity, mortality occurring only in fresh and sea-water after several days. Moulting occurs in all salinities, longer cycles being recorded in 0 and 35‰ S. The metabolism-salinity curve is broadly U-shaped between 0 and 28‰ S but declines sharply in sea-water. Such physiological responses characterise the early zoeae as strongly euryhaline and typically estuarine. Data are discussed in relation to the degree of adaptation of the organism to the freshwater biotope and the position of the species within the generic pattern of adaptive radiation.     

Morphological and physiological responses of Scaevola sericea (Goodeniaceae) seedlings to salt spray and substrate salinity

The effects of substrate salinity and salt spray upon seedlings of Scaevola sericea were examined in this study. Three levels of substrate salinity: 0.0 ppt, 3.0 ppt, and 10.0 ppt were examined in conjunction with three levels of salt spray: zero, medium (200 mg m^-2mdd^-1), and high (1200–1500 mg-m^-2mdd^-1). Leaf surface area, root to shoot ratio, as well as leaf, stem, and root mass decreased significantly (P 0.05) with increasing substrate salinity. Biomass accumulation was very low at 10.0 ppt substrate salinity, suggesting that higher levels of substrate salinity cannot be tolerated by the seedlings. Salt spray had a substantial effect on several of these variables, however its effects were less pronounced than those of substrate salinity. Cell sap osmolarity, leaf thickness, and leaf specific mass increased significantly (P 0.05) with both increasing substrate salinity and salt spray levels. Leaf carbon isotope ratios (δ^l3C) became more positive with increasing salinity, indicating an enhancement of the intrinsic water use efficiency of the seedlings at higher salinities. Scaevola sericea is one of the dominant plants found at the leading edge of strand communities in the Hawaiian archipelago and throughout much of the tropical Pacific. Since substrate salinity and salt spray increase with proximity to the ocean, the two factors may act together to limit the seaward expansion of S. sericea in coastal habitats.     

Germination and growth responses of hybridizing Carpobrotus species (Aizoaceae) from coastal California to soil salinity

Germination, growth, and physiological responses of hybridizing Carpobrotus from coastal California to soil salinity were studied. Hybrids are presumably the result of hybridization and introgression between the exotic Carpobrotus edulis, a succulent perennial invading coastal habitats, and the native or long-naturalized C. chilensis. Germination responses were investigated at 0, 10, 20, and 50% seawater. Seedling growth and physiology were compared by irrigating seedlings with solutions of the same seawater concentrations and in low and high nutrients. Germination was inhibited in the presence of salt, but recovered after transferring the seeds to fresh water. Seeds exposed to salt had higher final germination rates than control. Growth of Carpobrotus was slightly enhanced by low seawater concentrations but reduced at high salinity at both nutrient regimes. Leaf cell sap osmolarity increased with increasing soil salinity, and taxa did not differ significantly in this physiological adjustment. Leaf carbon isotope ratios (∂¹³C) ranged from −28 to −22‰ and became less negative at higher salinities, indicating an improved water use efficiency in the seedlings at high salt concentrations. In addition, ∂¹³C values were generally less negative at high than at low nutrients. Differences among taxa were generally small. The results show that salinity affects both establishment and growth of hybridizing Carpobrotus. The overall weak species differences in salt tolerance indicate that the exotic C. edulis can occupy the same sites as C. chilensis in terms of salinity. The similarity of hybrids in their response to salinity suggests that they may contribute to the invasion by Carpobrotus.     

Germination responses of Spartidium saharae (Coss. & Dur.) Pomel (Fabaceae) to temperature and salinity

Spartidium saharae is an endemic species of the Saharo-Arabian region. It is a tall shrub widely distributed in many sandy habitats including desert dunes and sandy systems in south-western part of Tunisia, where water and salinity are serious constraints. Laboratory experiments were carried out to assess temperature and salinity effects on seed germination. The seed germination responses were determined in complete darkness over a wide range of temperatures and salinities. Germination was inhibited by either an increase or decrease in temperature from the optimal temperature range (15–20°C). Highest germination percentages were obtained under nonsaline conditions and an increase in NaCl concentrations progressively inhibited seed germination. An interaction between salinity and temperature yielded no germination at 200 m m NaCl.     

Mortality and growth responses of Daphnia carinata to increases in temperature and salinity

1.  Daphnia carinata King, a freshwater cladoceran, occurs in Lake Waihola, a tidal lake with seasonal fluctuations in temperature (4–21 °C), and salinity (30–2000 mg L^–1 Cl). We hypothesise that these fluctuations influence the seasonal changes in D. carinata abundance.
2. To test this hypothesis, adults and juveniles were exposed to combinations of temperature and salinity. We measured mortality of adults and juveniles, growth of juveniles over 20 days, and their age at first reproduction.
3. The salinity tolerance of adult D. carinata was temperature-dependent. Juveniles were more sensitive to salinity, but more tolerant of temperature increases.
4. Growth rates were higher at elevated temperatures, but reduced by elevated salinities. The onset of reproduction was earlier at elevated temperatures.
5. We conclude that seasonal changes in temperature and salinity contribute to seasonal population changes of D. carinata .     

Bioventing of diesel oil-contaminated soil: Comparison of degradation rates in soil based on actual oil concentration and on respirometric data

The effects of bioventing, nutrient addition and inoculation with an oil-degrading bacterium on biodegradation of diesel oil in unsaturated soil were investigated. A mesocosm system was constructed consisting of six soil compartments each containing 6 m³ of naturally contaminated soil mixed 11 with silica sand, resulting in a diesel oil content of approximately 2000 mg kg^–1. Biodegradation was monitored over 112 days by determining the actual diesel oil content of the soil and by respirometric tests. The best agreement between calculations of degradation rates based upon the two methods was in July, when venting in combination with nutrient addition resulted in degradation rates of 23 mg kg^–1 day^–1 based on actual oil concentration in the soil and 33 mg kg^–1 day^–1 calculated from respirometric data. In September, these rates decreased to 9 and 1.4 mg kg^–1 day^–1, and in October the degradation rates were 5 and 0.7 mg kg^–1 day^–1 based upon the two methods. The average ambient temperature during the respirometric tests was 14,10 and 2°C in July, September and October, respectively. The combination of venting and nutrient addition resulted in an average residual oil content of the soil of 380 mg kg^–1. Neither venting alone nor inoculation enhanced oil degradation. The respiratory quotient averaged 0.40. The oil composition changed following degradation resulting in the unresolved complex mixture constituting up to 96% of the total oil content at the end of the experimental period.     

Tail docking in pigs: acute physiological and behavioural responses

Tail docking of piglets is a routine procedure on farms to control tail-biting behaviour; however, docking can cause an acute stress response. The objectives of this research were to determine the stress responses to tail docking in piglets and to compare two methods of tail docking; cautery iron (CAUT) and the more commonly used blunt trauma cutters (BT). At approximately 6 days of age, piglets were tail docked using CAUT (n = 20), BT (n = 20) or sham tail docked with their tails remaining intact (CON; n = 40). Blood samples were taken prior to tail docking and at 30, 60 and 90 min after tail docking to evaluate the effect of tail docking on white blood cell (WBC) measures and cortisol concentrations. The above experiment was repeated to observe behaviour without the periodic blood sampling, so as not to confound the effects of blood sampling on piglet behaviour. Piglet behaviour was recorded in the farrowing crate using 1 min scan-samples via live observations for 60 min prior to and 90 min after tail docking. Total WBC counts were reduced (P > 0.05) among BT and CAUT compared with CON piglets 30 min after tail docking. Cortisol concentrations were higher (P < 0.01) among BT compared with CON and CAUT piglets 60 min after tail docking. Cautery and BT-docked piglets spent more (P < 0.05) time posterior scooting compared with CON piglets between 0 and 15 min, and 31 and 45 min after tail docking. Piglets tail docked using CAUT and BT tended to spend more (P < 0.07) time sitting than CON piglets between 0 and 15 min post tail docking. Elevated blood cortisol can be reduced by the use of the CAUT rather than the BT method of tail docking. Although the tail docking-induced rise in cortisol was prevented by using CAUT, the behavioural response to BT and CAUT docking methods was similar.     

Prey naivety in the behavioural responses of juvenile Chinook salmon (Oncorhynchus tshawytscha) to an invasive predator

1. Non‐native predators might inflict proportionally higher mortality on prey that have no previous experience of them, compared to species that have coexisted with the predator for some time. 2. We tested whether juvenile Chinook salmon (Oncorhynchus tshawytscha) were less able to recognise a non‐native than a native predator, by investigating behavioural responses to the chemical cues of the invasive smallmouth bass (Micropterus dolomieu) and the native northern pikeminnow (Ptychocheilus oregonensis) in both laboratory and field experiments. 3. Laboratory results demonstrated strong innate antipredator responses of individual juvenile Chinook salmon to northern pikeminnow; fish spent 70% of time motionless and exhibited 100% greater panic response than in controls. By contrast, antipredator responses to the chemical cues of smallmouth bass did not differ from controls. 4. These results were supported by similar differences in recognition of these predator odours by groups of juvenile Chinook salmon in fully natural conditions, though responses reflected a greater range of antipredator behaviours by individuals. In field trials, responses to northern pikeminnow odour resulted in increased flight or absence, reductions in swimming and foraging, and increased time spent near the substratum, compared to smallmouth bass odour. 5. Given that survival of juvenile fish is facilitated by predator recognition, our results support the hypothesis that naivety may be an important factor determining the effect of non‐native predators on prey populations. Efforts to manage the effect of native and non‐native predators may benefit by considering complex behavioural interactions, such as these at the individual and group levels.     

Antifungal activities of anise oil, lime oil, and tangerine oil against molds on rubberwood (Hevea brasiliensis)

The antifungal activities of anise oil, lime oil, and tangerine oil against molds identified from rubberwood surfaces (Aspergillus niger, Penicillium chrysogenum, and Penicillium sp.) were investigated. The broth dilution method was employed to determine the minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC) using the concentration of essential oils between 20 and 200 μl ml⁻¹. Inhibitory effects of the essential oils against those molds on rubberwood were also examined by means of the dip treatment and vacuum impregnation treatment. It was found that the MIC and MFC values for each treatment on agar were identical for all conditions examined. Anise oil was the strongest inhibitor with the MIC and MFC of 40 μl ml⁻¹ against Penicillium sp. and A. niger, and 60 μl ml⁻¹ against P. chrysogenum. Lime oil and tangerine oil were also effective against those molds at higher concentrations of 100–180 μl ml⁻¹. All essential oils at the MIC and MFC provided a protection from mold growth on rubberwood for at least 12 weeks at storage conditions of 30 °C with 100% RH.     

Eco-physiology of Palaemonetes antennarius (Crustacea, Decapoda): the influence of temperature and salinity on cardiac frequency

Abstract.  The effect of different temperatures and salinities on the cardiac frequency of the freshwater shrimp Palaemonetes antennarius is investigated. The results show that both temperature and salinity influence heart rate. Variations in water temperature are associated with changes in heart rate: variations higher than 8°C in 6 h affect not only heart rate, but also shrimp survival. After an initial rapid increase, the heart rate returns to initial values at saline concentrations of 15‰ and 30‰, whereas, at 20‰ salinity, the shrimps show a persistent decrease of heart rate throughout the test. The marked tolerance of variations of temperature and salinity suggests that P.   antennarius is well adapted to waters with large salinity and temperature oscillations. Cardiac frequency can be used as a valid indicator of physiological stress in this species.     

Physiological basis of interactive responses to temperature and salinity in coastal marine invertebrate: Implications for responses to warming

Developing physiological mechanistic models to predict species’ responses to climate‐driven environmental variables remains a key endeavor in ecology. Such approaches are challenging, because they require linking physiological processes with fitness and contraction or expansion in species’ distributions. We explore those links for coastal marine species, occurring in regions of freshwater influence (ROFIs) and exposed to changes in temperature and salinity. First, we evaluated the effect of temperature on hemolymph osmolality and on the expression of genes relevant for osmoregulation in larvae of the shore crab Carcinus maenas. We then discuss and develop a hypothetical model linking osmoregulation, fitness, and species expansion/contraction toward or away from ROFIs. In C. maenas, high temperature led to a threefold increase in the capacity to osmoregulate in the first and last larval stages (i.e., those more likely to experience low salinities). This result matched the known pattern of survival for larval stages where the negative effect of low salinity on survival is mitigated at high temperatures (abbreviated as TMLS). Because gene expression levels did not change at low salinity nor at high temperatures, we hypothesize that the increase in osmoregulatory capacity (OC) at high temperature should involve post‐translational processes. Further analysis of data suggested that TMLS occurs in C. maenas larvae due to the combination of increased osmoregulation (a physiological mechanism) and a reduced developmental period (a phenological mechanisms) when exposed to high temperatures. Based on information from the literature, we propose a model for C. maenas and other coastal species showing the contribution of osmoregulation and phenological mechanisms toward changes in range distribution under coastal warming. In species where the OC increases with temperature (e.g., C. maenas larvae), osmoregulation should contribute toward expansion if temperature increases; by contrast in those species where osmoregulation is weaker at high temperature, the contribution should be toward range contraction.     

The relationship between lamellar-type cytosomes,DOPA decarboxylase,and lateral ciliary activity of the oyster Crassostrea virginica (Gmelin): Response to salinity change

Lamellar transformations of cytosomes, DOPA decarboxylase and lateral ciliary activity were measured in neuronal components and/or ctenidia of the oyster, Crassostrea virginica (Gmelin). Prolonged exposure to light, anoxic conditions, EGTA (a calcium chelator), and exogenous perfusion of dopamine (a cilioinhibitory neurotransmitter) increases the frequency of lamellar type cytosomes. This is accompanied by decreases in enzymatic activity and a lateral cilioinhibition. Prolonged periods of darkness, electrical stimulation of the branchial nerve and exogenous perfusion of serotonin (a cilioexcitatory neurotransmitter) reduces the conversion of lamellar type configurations, increases enzymatic activity and produces a lateral cilioexcitation. Salinity changes that produce an increase to higher acclimation values result in a gradual decrease in the number of lamellar configurations with a subsequent increase in enzymatic activity and lateral cilioexcitation. The magnitude of the lateral cilioexcitation-cilioinhibition and decarboxylase activity is directly related to the number of lamellar conversions.     

The survival and growth of Gammarus tigrinus Sexton (Crustacea: Amphipoda) in relation to salinity and temperature

Field collections from an inland saline lake indicated that a rapid increase in numbers of a population of Gammarus tigrinus was positively correlated with high summer temperatures and salinities. The laboratory experiments on growth are an attempt to determine whether high summer temperatures or optimum salinity were primarily responsible for the rapid increase in numbers. Furthermore, G. tigrinus was not found in either of two adjacent lakes; one non-saline, the other at a higher salinity. The laboratory experiments on survival are an attempt to determine whether the restricted distribution of G. tigrinus was related to salinity. The implications of the field and laboratory studies are discussed and compared with other data from Europe and North America.