Respiratory and behavioral responses of the grass shrimp Palaemonetes pugio to cadmium and reduced dissolved oxygen

Adult grass shrimp (Palaemonetes pugio) were collected during July and August, 1973, and exposed for 48-h periods to a series of sublethal cadmium (Cd) concentrations: 0.1 and 0.56 mg l^-1 for metabolic studies; and 0.01, 0.05, 0.1, 0.3, 0.56 mg l^-1 for locomotor studies. Treatment effects were tested singly and in combination at selected dissolved oxygen (DO) concentrations ranging from near saturation to 0.8 mgl^-1. Shrimp not exposed to Cd exhibited metabolic regulation between 6.5 and, 4.6 mg DOl^-1, with progressively lower O₂ consumption rates at lower DO concentrations. Oxygen consumption of Cd-exposed shrimp was suppressed overall relative to the non-Cd treated shrimp, and with one exception, the magnitude of metabolic suppression directly corresponded to Cd concentration. Locomotor activity of non-Cd exposed shrimp was relatively independent of DO concentration down to 2.8 mg DO l^-1 and became significantly suppressed at 1.8 mg DO l^-1 and below. Significant suppression of locomotion was evident in shrimp exposed to 0.56 mg Cd l^-1, but was not seen in treatment groups of 0.3 mg Cd l^-1 or lower. No interaction on locomotor activity of shrimp was detected between Cd exposure and oxygen concentration. The reduction of locomotor activity and metabolism at 0.56 mg Cd l^-1 exposure is similar to that occurring under reduced oxygen condition. It is hypothesized that Cd acts in some manner to suppress O₂ availability to P. pugio, a suggestion consistent with literature reports on adverse effects of Cd on fish respiratory enzymes and gill tissue.Contribution No. 351 of the U.S. Environmental Protection Agency, Environmental Research Laboratory, Narragansett, Rhode Island. Although the research described in this article was funded by the U.S. Environmental Protection Agency, it has not been subjected to Agency review and therefore does not necessarily reflect the views of the Agency and no official endorsement should be inferred     

Effect of cadmium on survival and osmoregulation of various developmental stages of the shrimp Penaeus japonicus (Crustacea: Decapoda)

The object of this study was to evaluate the acute toxicity of cadmium in different post-embryonic stages of the penaeid shrimp Penaeus japonicus (Bate, 1888) and to determine the effect of sublethal cadmium on the osmoregulatory capacity used as an indicator of physiological condition. Tolerance to cadmium increases with the developmental stage. The least tolerant stages are the nauplii (48 h LC₅₀: 124 g Cd l^-1) and the zoeae (96 h LC₅₀: 10 to 30 g Cd l^-1). The most tolerant stages are the postlarvae (96 h LC₅₀: 200 to 3500 Cd l^-1) and juveniles (96 h LC₅₀: 5500 g Cd l^-1). In juvenile shrimp, 2000 g Cd l^-1 significantly reduce hypo- and hyper-OC. The effect of cadmium on hypo- and hyper-osmoregulatory capacity illustrates a dose- and time-dependent response. Surviving shrimp recover their hypo-osmoregulatory capacity after 6 d of readaptation in cadmium-free seawater.     

Synergistic effects of cadmium and salinity combined with constant and cycling temperatures on the larval development of two estuarine crab species

The developmental stages from megalopa to third crab of the blue crab Callinectes sapidus Rathbun were tested in 12 combinations of cadmium (0, 50, and 150 ppb) and salinity (10, 20, 30, and 40) at 25°C. A reduction in survival and a significant delay in development from megalopa to third crab occurred within each salinity regime in 50 ppb compared with the control. Comparison of the delay in development within each salinity regime revealed that the sublethal effect of cadmium was most pronounced in the salinities normally preferred by C. sapidus. A similar comparison within each cadmium concentration, however, showed that the developmental time from megalopa to third crab was approximately the same irrespective of salinity. The developmental stages from hatch to first crab of the mud-crab Rhithropanopeus harrisii (Gould) were examined in 63 combinations of cadmium (0, 50, and 150 ppb), salinity (10, 20, and 30), constant temperature (20°, 25°, 30°, and 35°C) and cycling temperature (20° to 25°C, 25° to 30°C, and 30° to 35°C). The results indicated that cycling temperatures may have a stimulating effect on survival of the larvae compared to constant temperatures, both in the presence and in the absence of cadmium. Effects of cadmium and salinity and their interaction on the survival of the larvae from zoeae to megalopa were documented at most of the temperatures by analyses of variance. The zoeal larvae were more susceptible to cadmium than the megalopa. Effects of different combinations of cadmium and salinity on the duration of larval development were assessed by a t-test.     

Rearing Pandalus borealis larvae in the laboratory

Larvae of the northern shrimp Pandalus borealis (Krøyer) are pelagic. In the Estuary and Gulf of St. Lawrence, Canada, the early stages are found in the upper 25-m of the water column in spring and early summer and are expected to experience a range of water temperatures from as low as 0°C to as high at 6°C. Little is known of the impact of water temperature on metabolic requirements of northern shrimp larvae. In this study, routine respiration (VO₂), maximum respiration (electron transport system activity, ETSA) and metabolic scope for growth (MS, ETSA–VO₂) of northern shrimp larvae were measured as a function of temperature (3, 5 and 8°C), developmental stage (I–V at 3°C, I–VII at 5°C and 8°C) and growth rate in dry mass. After logarithmic transformation, all three metabolic variables were linearly related to dry mass. The increase in VO₂ with body mass was faster at 5°C than at 3 or 8°C, whereas with ETSA this increase was slower. As a result, MS increased more slowly with dry mass at 5°C than at 3 and 8°C. However, MS did not limit growth in this study, since it explained only 39% of the variability in growth. All three metabolic variables as well as growth varied together as a function of temperature and ontogeny. Q₁₀ of all three metabolic variables ranged from 1.6 and 2.2 for stages I–V larvae, except for VO₂ at stage I (3.9) and stage III (2.9).     

Respiratory physiology in summer diapause embryos of the neustonic copepodAnomalocera patersoni

The respiratory physiology of summer diapausing eggs of the neustonic copepodAnomalocera patersoni, maintained under constant temperature (13 °C) and light (12 h light:12 h dark) conditions, was characterized by a bell-shaped curve, with low O₂ uptake levels at the beginning of dormancy. This was followed by a steady rise in O₂ consumption with maximum levels of 0.002 l O₂ embryo^–1 h^–1 70 d after spawning. A slow diminution in O₂ uptake then occurred until Day 150 when minimum values of 0.0003 l O₂ embryo^–1 h^–1 were recorded, coinciding with the hatching of the first embryos. Embryos continued to hatch asynchronously up to 360 d from the moment of egg laying. When eggs were subjected to 20 °C, the respiratory activity was almost three times higher than at 13 °C, even though both respiratory curves were similar. The elevated metabolism in eggs kept at 20 °C led to death of the embryos possibly due to a total depletion of metabolic reserves. ATP content also differed at the two temperatures. Diapause eggs kept at 20 °C showed no rapid rise in ATP content as opposed to those kept at 13 °C. The results of temperature shock experiments, in which eggs were first kept at winter temperatures for several weeks, after which the temperature was raised to 20 °C for another number of weeks prior to a second period of chilling at 13 °C, showed that as long as embryos were kept at 20 °C no hatching occurred. By contrast, hatching was observed after 10 d following the resumption of winter temperatures, suggesting that low environmental temperatures are an essential prerequisite for hatching of these eggs. The type of diapause inA. patersoni differs considerably from the one described in insects and in another neustonic copepod,Pontella mediterrana. In this case, there is a U-shaped respiratory curve with greatest O₂ consumption prior to the onset or upon breaking of diapause. Differences in the two types of diapause seem to involve not only differences in O₂ consumption levels but also in the sequence of metabolic changes with time and the metabolic requirements during sommer and winter dormancy.     

Effect of temperature on the escape responses of larval herring,Clupea harengus

Herring (Clupea harengus L.) larvae from spring and autumn spawning stocks were reared at different constant temperatures from 5° to 17 °C. At equivalent developmental stages, the spring larvae were longer than the autumn larvae and the larvae reared at low temperatures were longer than those reared at high temperatures. At hatching and at the end of the yolk-sac stage, the larvae were induced, by a probe, to make C-start escape responses, which were recorded and analysed using a high-speed video recording at 400 frames s^-1. The response was rapid and of short duration. The tailbeat frequency and swimming speed were measured during the burst of swimming following the C-start at different test temperatures and in larvae with different temperature histories. The tail-beat frequency was strongly temperature-dependent, rising from 19 Hz at 5 °C to 37 Hz at 17 °C with no effect of temperature history, season or developmental stage. The burst-swimming speed ranged at hatching from 75 to 90 mm s^-1 at 5 °C to 110 to 160 mm s^-1 at 17 °C and at yolk resorption from 90–115 mm s^-1 at 5 °C to 175–190 mm s^-1 at 17 °C. The longer, spring-spawned larvae swam faster than the shorter autumn-spawned larvae. When the swimming speeds were expressed as body lengths (L) s^-1, these differences disappeared. Larvae swam from 7–9 L s^-1 at 5 °C to 15–20 L s^-1 at 17 °C at hatching, and from 8–9 L s^-1 at 5 °C to 15–17 L s^-1 at 17 °C at yolk resorption. There was, however, a significantly faster specific swimming speed by the larvae reared at 12 °C in spring 1991.Honorary Research Fellow of the Scottish Association for Marine ScienceUnfortunately, Karen Fretwell was drowned in an accident on 9 January 1993     

Daily energy requirements and trophic positioning of the sand shrimp<Emphasis Type="Italic"> Crangon septemspinosa</Emphasis>

Sand shrimp, Crangon septemspinosa Say, are important to the trophic dynamics of coastal systems in the northwestern Atlantic. To evaluate predatory impacts of sand shrimp, daily energy requirements (J ind.^–1 day^–1) were calculated for this species from laboratory estimates of energy losses due to routine (R_R), active (R_A), and feeding (R_SDA) oxygen consumption rates (J ind.^–1 h^–1), coupled with measurements of diel motile activity. Shrimp used in this study were collected biweekly from the Niantic River, Connecticut (41°33N; 72°19W) during late spring and summer of 2000 and 2001. The rates of shrimp energy loss due to R_R and R_A increased exponentially with increasing temperature, with the magnitude of increase greater between 6°C and 10°C (Q₁₀=3.01) than between 10°C and 14°C (Q₁₀=2.85). Rates of R_R doubled with a twofold increase in shrimp mass, and R_SDA was 0.130 J h^–1+R_R, irrespective of shrimp body size. Shrimp motile activity was significantly greater during dark periods relative to light periods, indicating nocturnal behavior. Nocturnal activity also increased significantly at higher temperatures, and at 20°C shifted from a unimodal to a bimodal pattern. Laboratory estimates of daily metabolic expenditures (1.7–307.4 J ind.^–1 day^–1 for 0.05 and 1.5 g wet weight shrimp, respectively, between 0°C and 20°C) were combined with results from previous investigations to construct a bioenergetic model and make inferences regarding the trophic positioning of C. septemspinosa. Bioenergetic model estimates indicated that juvenile and adult shrimp could meet daily energy demands via opportunistic omnivory, selectively preying upon items of high energy content (e.g. invertebrate and fish tissue) and compensating for limited prey availability by ingesting readily accessible lower energy food (e.g. detritus and plant material).Electronic Supplementary Material Supplementary material is available in the online version of this article at Communicated by J.P. Grassle, New Brunswick     

Effect of ammonia on survival and osmoregulation in different life stages of the lobsterHomarus americanus

Acute toxicity of ammonia was determined for cultured larval, postlarval, and wild adult lobsters (Homarus americanus) in 1988. Ammonia tolerance was found to increase with ontogenetic development. Based on 96-h LC₅₀ values of 58 mg l^–1 NH₄ ⁺ + NH₃ l^–1 seawater (0.72 mg NH₃ l^–1) for Stage I larvae, 87 mg NH₄ ⁺ + NH₃ l^–1 (1.7 mg NH₃ l^–1) for Stage II larvae, 125 mg NH₄ ⁺ + NH₃ l^–1 (2.13 mg NH₃) for Stage III larvae, 144 mg NH₄ ⁺ + NH₃ l^–1 (2.36 mg NH₃ l^–1) for Stage IV postlarvae, 377 mg NH₄ ⁺ + NH₃ l^–1 (5.12 mg NH₃ l^–1) for adult lobsters at 5°C and 219 mg NH₄ ⁺ + NH₃ l^–1 (3.25 mg NH₃ l^–1) for adult lobsters at 20°C, recommendations for safe levels of total ammonia and un-ionized ammonia were calculated using an application factor of 0.1. Effects of ammonia on osmoregulatory capacity were studied on postlarvae and adults. Ability of postlarvae and adults to hyper-regulate in low-salinity media decreased after exposure to ammonia. In postlarval lobsters, osmoregulatory capacity was significantly affected in ammonia concentrations exceeding 32 mg l^–1. Osmoregulatory capacity in adult lobsters (5 and 20°C) was affected at 150 mg l^–1. In postlarval lobsters, a minimum exposure time of 12 h was required to impair osmoregulatory capacity. The decrease in hemolymph osmotic pressure was caused by lower hemolymph sodium concentrations. The presence of ammonia in the external medium could markedly affect the Na⁺/NH₄ ⁺ transport mechanism by permanently, temporarily, or partially impairing the transport sites for sodium.     

Effect of elevated temperature on aerobic respiration of coral recruits

Metabolic rates provide a valuable means to assess the condition of early life stages of scleractinians, but their small biomass creates a signal-to-noise problem in a confined respirometer. To avoid this problem, measurements of the oxygen diffusion boundary layer (DBL) and Ficks first law were used to calculate the respiration rate of coenosarc tissue on recruits (i.e., colonies 5–14 mm diameter) of Porites lutea (Edwards and Haime, 1860) exposed to two temperatures at a flow speed of 0.6 cm s^–1. All experiments were completed in Moorea, French Polynesia, between November and December 2003. At 26.8°C, the DBL was 565±55 µm thick, the oxygen saturation adjacent to the tissue was 80±3%, and the mean respiration of the coenosarc was 1.2±0.1 µl O₂ cm^–2 h^–1 (all values mean ± SE, n=10). Exposure to 29.7°C for 24–48 h did not affect the DBL thickness but significantly reduced the oxygen saturation adjacent to the tissue (to 74%) and increased the mean respiration rate by 35%. As the small corals differed slightly in size, in a uniform flow speed they experienced dissimilar flow environments as characterized by the Reynolds number (Re), thereby creating the opportunity to test the flow dependency of respiration. At 26.8°C, respiration and Re were unrelated, but at 29.7°C, the relationship was positive and statistically significant. Thus, respiration of small corals may not be mass transfer limited at low temperature, but relatively small increases in temperature may result in an increased metabolic rate leading to mass transfer limitation and flow-dependent rates of respiration.Communicated by J.P. Grassle, New Brunswick     

Metabolic adaptation of Cancer irroratus developmental stages to cyclic temperatures

Metabolic-temperature responses of the developmental stages of the sublittoral crab Cancer irroratus cultured at 10° to 20°C daily cyclic and 15°C constant temperatures were determined. Generally, the metabolic rate increased with temperature in the lower range with Q₁₀'s (temperature coefficients) above 2, compensated in the midrange with Q₁₀'s between 1 and 2, and declined at the higher temperatures with Q₁₀ values less than 1. For the larvae cultured at a constant temperature of 15°C, the compensatory response range narrowed with development from first zoeae to the later zoeal stages. In contrast, the compensatory response of the first zoeae, megalops, and crab stages within the range 10° to 25°C was interrupted by a zone of thermal sensitivity between 15° and 20°C for those individuals cultured in the 10° to 20°C cyclic regime. The compensatory response range is narrower for the third stage zoeae and broader for the second, fourth, and fifth stage zoeae. Metabolic rate-temperature (M-T) patterns of C. irroratus developmental stages cultured under the cyclic regime varied from those held at constant temperature by increased respiration and metabolic rate compensation between 20° and 25°C, and by an extension of the metabolically active range towards higher temperatures.     

Metallothionein induction inMytilus edulis exposed to cadmium

The exposure of mussels,Mytilus edulis, collected from Whitsand Bay, southwest England, in August 1988, to sublethal concentrations of cadmium (400µg l^–1) for 65 d resulted in the induction of metallothionein (MT) synthesis in the soft tissues. In cadmium-exposed mussels, metallothionein concentrations, measured by differential pulse polarography, increased by a factor of three, from 2 to 3 mg g^–1 to a maximum of 9 mg g^–1 after 30 d. No significant changes could be detected in controls. Cadmium accumulated in the soft tissues of mussels correlated significantly with metallothionein concentrations and can be described by the relationship: MT (mg g^–1)=0.045 Cd (µg g^–1)+3.03 (r=0.803,P<0.001). Gel chromatography of heat-treated cytosolic extracts showed that the accumulated cadmium is bound principally to the newly formed metallothioneins. Copper and zinc were also analysed in the whole soft-tissues and in subcellular fractions of cadmium-exposed mussels. Although copper concentrations were not affected by cadmium-exposure, zinc levels were significantly reduced. The results demonstrate that the induction of metallothioneins inM. edulis is a quantifiable biological response to sublethal levels of cadmium exposure.     

Influence of temperature changes on oxygen uptake and ammonia and phosphate excretion,in relation to body size and weight,in Oikopleura dioica (Appendicularia)

The relationship between the rates of oxygen consumption, ammonia and phosphate excretion of a pelagic tunicate, the larvacean Oikopleura dioica Fol, 1872 were assessed as a function of size, dry weight and ash-free dry weight at 15°, 20° and 24°C. O. dioica has higher respiration and excretion rates than copepods of similar weight, but the weight exponent of the allometric power function: Y=aX ^b is similar to that of other poikilotherms. Temperatures above 20°C have a depressing effect on respiration and ammonia excretion. 90% of the variance in metabolic rates is explainable by body mass and temperatures Q₁₀ values for oxygen consumption, ammonia and phosphate excretion, respectively, are 2.45, 1.86 and 1.75 between 15° and 20°C, and 3.75, 2.90 and 3.60 between 20° and 24°C. Metabolic quotients (O:N, O:P, N:P) indicate a protein-oriented diet. The results of this study suggest weak metabolic regulation in O. dioica, an energetic strategy which allows an immediate response to favourable changes in feeding conditions.     

Some aspects of the thermal tolerance of Trichomya hirsuta (Mollusca: Bivalvia) of Eastern Australia

The upper temperature tolerance range for Trichomya hirsuta L. is described for acclimation temperatures of 10° to 32°C at 30% S. Changes in thermal resistance with time are described along with the incipient lethal temperatures. The eurythermicity for the species is 240.7 C°-squared. The ultimate upper incipient lethal temperature is 35.1°C. Definition of the incipient sublethal temperature is given, and is equal to 32°C. Diet effects are shown not to be significant in short-term lethal experiments, but indicate that unfed mussels reduce their resistance after prolonged exposure to high temperatures. Size was also shown to have no effect on resistance and tolerance. A comparison of the tolerance triangle of T. hirsuta with those of the temperate species Mytilus edulis and Mya arenaria revealed that the 24-h LT₅₀ minus 2.2 C° approximates the incipient lethal temperature. The eurythermicities of the temperate species are Mytilus edulis, 363 C°-squared; and Mya arenaria, 415 C°-squared.     

Effect of an organophosphorus insecticide, fenitrothion, on survival and osmoregulation of various developmental stages of the shrimp Penaeus japonicus (Crustacea: Decapoda)

The toxicity of fenitrothion was determined in larvae (nauplii, Zoeae 1 to 3, Mysis 1 to 3), postlarvae (PL stages) and juvenile shrimp (Penaeus japonicus Bate), in two media, seawater (SW) and diluted seawater (DSW) (1100 and 550 mosM kg⁻¹, ≃ 37 and 19‰ S). The effects of fenitrothion on the osmoregulatory capacities (OC) of juveniles were recorded. A gill and epipodite histopathological study was also conducted. For larvae in seawater, 24 and 48 h LC₅₀s ranged from 32.9 μg l⁻¹ (Zoeae 2) to 10.7 μg l⁻¹ (Mysis 3), and from 3.9 μg l⁻¹ (Zoeae 3) to 2.0 μg l⁻¹ (Mysis 3), respectively; 48 and 96 h  LC₅₀s in postlarvae (PL) at the same salinity ranged from 1.8 μg l⁻¹ (PL1) to 0.6 μg l⁻¹ (PL5), and from 0.3 μg l⁻¹ (PL7) to 0.4 μg l⁻¹ (PL15). In juveniles, 96 h LC₅₀s were 0.8 μg l⁻¹ in seawater and 1.5 μg l⁻¹ in diluted seawater. From hatching to juvenile stages, the overall trend was a rapid decrease (from nauplii to PL5–PL7) followed by a slight increase (from PL7 to PL15 and juveniles) in the shrimp's ability to tolerate the insecticide. In juveniles kept in seawater and in diluted seawater, fenitrothion decreased the osmoregulatory capacity (OC = difference between the hemolymph osmotic pressure and the osmotic pressure of the medium) at both lethal and sublethal concentrations. This effect was time- and dose-dependent. In SW, the decrease in hypo-OC was ˜ 25% at sublethal concentrations and ˜ 35% at the 96 h LC₅₀. In DSW, the decrease in hyper-OC was ˜ 10 to 15% at sublethal concentrations. In SW, shrimp were able to recover their OC in less than 48 h when transferred to water free of pesticide. In DSW, recovery at 48 h was only possible after exposure to the lowest tested sublethal concentration. Haemocytic congestions (thrombosis) of the gills, lamellae necrosis and other alterations of gills and epipodites (breakage of the cuticle, reduction of the hemolymph lacunae) were noted in juveniles exposed to lethal and sublethal concentrations of fenitrothion. Received: 7 October 1996 / Accepted: 13 November 1996     

Viability of embryos of the winter flounder Pseudopleuronectes americanus exposed to combinations of cadmium and salinity at selected temperatures

Developing eggs of the winter flounder Pseudopleuronectes americanus (Walbaum) were exposed to 9 combinations of cadmium and salinity at 5° and 10°C. Overall mean times to 50% hatch ranged from 7.7 days at 10°C to 17.9 days at 5°C. Mean percentages of total hatches ranged from 50 to 100% for all treatment combinations. Response-surface analyses indicate percentages of viable hatches were generally lowest at 10% S and highest in the 25 to 30% S range. Regression analyses of viable hatch data show that at both temperatures cadmium significantly influenced viable hatch in all experiments. Viable hatch was also significantly influenced by the linear and quadratic effect of salinity in both tests at 5°C and in 2 of 3 tests at 10°C. The interaction between cadmium and salinity also significantly affected viable hatch at 10°C.     

Oil exposure in a warmer Arctic: potential impacts on key zooplankton species

Oil exploration activities are rapidly increasing in Arctic marine areas with potentially higher risks of oil spills to the environment. Water temperatures in Arctic marine areas are simultaneously increasing as a result of global warming. Potential effects of a combination of increased water temperature and exposure to the PAH pyrene were investigated on fecal pellet and, egg production and hatching success of two copepod species, Calanus finmarchicus and Calanus glacialis, sampled in Disko Bay, Greenland on 23–25 April 2008. The two species were exposed daily to nominal pyrene concentrations of 0-0.01-0.1-1-10-100 nM at water temperatures of 0.5, 5 and 8°C for 9 and 7 days, respectively. Daily measurements of faecal pellet production, egg production and hatching showed different responses of the two species to the applied stressors. When temperature increased, low concentrations of pyrene caused a decrease in faecal pellet production by C. finmarchicus, whereas C. glacialis faecal pellet production showed no negative response to pyrene exposure when temperatures increased. Pyrene exposure decreased egg production of C. finmarchicus at all temperatures, but the species was more sensitive at 0.5 and 8°C. A lag period of 1 day before egg production began was prolonged with several days when warmer water was combined with pyrene exposure. Egg production by C. glacialis was only negatively affected by pyrene in a dose-dependent manner at 0.5°C. Hatching success in both species was not affected by pyrene, where increased water temperatures led to a higher hatching success. In conclusion, C. glacialis seemed to be the less sensitive of the two species to the stress combination of increased water temperature and pyrene exposure. As a consequence of the differential responses of the two species, their competition can be impaired with a consequent impact on energy transfer between trophic levels.     

Photosynthetic characteristics of Prochloron sp./ascidian symbioses

The prokaryotic green alga Prochloron sp. (Prochlorophyta) is found in symbiotic association with colonial didemnid ascidians that inhabit warm tropical waters in a broad range of light environments. We sought to determine the light-adaptation features of this alga in relation to the natural light environments in which the symbioses are found, and to characterize the temperature sensitivity of photosynthesis and respiration of Prochloron sp. in order to assess its physiological role in the productivity and distribution of the symbiosis. Colonies of the host ascidian Lissoclinum patella were collected from exposed and shaded habitats in a shallow lagoon in Palau, West Caroline Islands, during February and March, 1983. Some colonies from the two light habitats were maintained under conditions of high light (2 200 E m^–2 s^–1) and low light (400 E m^–2 s^–1) in running seawater tanks. The environments were characterized in terms of daily light quantum fluxes, daily periods of light-saturated photosynthesis (H_sat), and photon flux density levels. Prochloron sp. cells were isolated from the hosts and examined for their photosynthesis vs irradiance relationships, respiration, pigment content and photosynthetic unit features. In addition, daily P:R ratios, photosynthetic quotients, carbon balances and photosynthetic carbon release were also characterized. It was found that Prochloron sp. cells from low-light colonies possessed lower chlorophyll a/b ratios, larger photosynthetic units sizes based on both reaction I and reaction II, similar numbers of reaction center I and reaction center II per cell, lower respiration levels, and lower P_max values than cells from high-light colonies. Cells isolated from low-light colonies showed photoinhibition of P_max at photon flux densities above 800 E m^–2 s^–1. However, because the host tissue attenuates about 60 to 80% of the incident irradiance, it is unlikely that these cells are normally photoinhibited in hospite. Collectively, the light-adaptation features of Prochloron sp. were more similar to those of eukaryotic algae and vascular plant chloroplasts than to those of cyanobacteria, and the responses were more sensitive to the daily flux of photosynthetic quantum than to photon flux density per se. Calculation of daily minimum carbon balances indicated that, though high-light cells had daily P:R ratios of 1.0 compared to 4.6 for low-light cells, the cells from the two different light environments showed nearly identical daily carbon gains. Cells isolated from high-light colonies released between 15 and 20% of their photosynthetically-fixed carbon, levels sufficient to be important in the nutrition of the host. Q₁₀ responses of photosynthesis and respiration in Prochloron sp. cells exposed briefly (15–45 min) to temperatures between 15° and 45°C revealed a discontinuity in the photosynthetic response at the ambient growth temperatures. The photosynthetic rates were found to be more than twice as sensitive to temperatures below ambient (Q₁₀=3.47) than to temperatures above ambient (Q₁₀=1.47). The Q₁₀ for respiration was constant (Q₁₀=1.66) over the temperature range examined. It appears that the photosynthetic temperature sensitivity of Prochloron sp. may restrict its distribution to warmer tropical waters. The ecological implications of these findings are discussed in relation to published data on other symbiotic systems and free-living algae.     

Filter-feeding ethology of benthic invertebrates (ascidians). V. Influence of temperature on pumping,filtration and digestion rates and rhythms in Phallusia mamillata

The influence of temperature has been studied simultaneously on the pumping, filtration, and digestion rates of Phallusia mammillata (Cuvier, 1815). Eighteen experiments were made between 7° and 25°C on 5 individuals. The average velocities of the water current varied between 3.37 and 9.65 cm sec^-1 (maximum 34.90 cm sec^-1). No recognizable rhythm emerged; pumping was continuous except at 7°C, where it soon ceased. Above 20°C, the curves were irregular and reflected the high sensitivity of the ascidian. The pumping rate was highest at 15°C (mean=5,788 ml h^-1 g^-1 dry weight of organs). At 10°C, the mean was 3,560; at 20°C, 2,629 ml h^-1 g^-1 dry weight of organs. At 20°C, the coefficients of variation displayed higher values, indicating a more irregular pumping at this temperature. Although there was no filtration rhythm, the variability of the results was higher at 20°C and above. As for pumping, maximum values were observed at 15°C (mean=4,286 ml h^-1 g^-1 dry weight of organs) decreasing with lower and higher temperatures, such decreases being more marked at the higher temperatures. Means were 352 ml h^-1 g^-1 dry weight of organs at 7°C; 2,935 at 10°C; 1,995 at 20°C; 973 at 25°C. The mean temperature coefficients for the filtration rates were: Q₁₀ for 7° to 15°C=11.86, Q₁₀ for 10° to 20°C=0,66, Q₁₀ for 15° to 25°C=0.22. The filtering efficiency was fairly constant throughout an experiment; the pumping and filtration curves were in fact almost parallel. The filtering efficiency of the branchial sac was high (75 to 85%), with constant values at 10° and 15°C; it became smaller (59%) at 20°C, with a higher coefficient of variation. The digestion rate also displayed maximum values at 15°C (mean=5.47 mg of albumin equivalent 24 h^-1 g^-1 dry weight of organs). It was lower at 10°C (mean=3.60 mg) and reached its minimum at 20°C (mean=1.71 mg). The higher temperature affected the percentage of food utilization, which showed smaller values at 20°C (59%) than at 10°C (89%) and 15°C (87%).     

Energy content at metamorphosis and growth rate of the early juvenile barnacle<Emphasis Type="Italic"> Balanus amphitrite</Emphasis>

The energetic cost of metamorphosis in cyprids of the barnacle Balanus amphitrite Darwin was estimated by quantification of lipid, carbohydrate and protein contents. About 38–58% (4–5 mJ individual^–1) of cypris energy reserves were used during metamorphosis. Lipids accounted for 55–65%, proteins for 34–44% and carbohydrates for <2% of the energy used. Juveniles obtained from larvae fed 10⁶ cells ml^–1 of Chaetoceros gracilis were bigger (carapace length: 560–616 µm) and contained more energy (5.56±0.10 mJ juvenile^–1) than their counterparts (carapace length: 420–462 µm; energy content: 2.49±0.20 mJ juvenile^–1) obtained from larvae fed 10⁴ cells ml^–1. At water temperatures of 30°C and 24°C and food concentrations of 10⁴ and 10² cells ml^–1 (3:1 mixture of C. gracilis and Isochrysis galbana) as well as under field conditions (26.9±3.1°C and 2.2±0.8 µg chlorophyll a l^–1), juveniles obtained from larvae fed the high food concentration grew faster than juveniles obtained from larvae fed low food concentration until 5 days post-metamorphosis. Laboratory experiments revealed a combined effect of early juvenile energy content, temperature and food concentration on growth until 5 days post-metamorphosis. After 10 days post-metamorphosis, the influence of the early juvenile energy content on growth became negligible. Overall, our results indicate that the energy content at metamorphosis is of critical importance for initial growth of juvenile barnacles and emphasize the dependency of the physiological performance of early juvenile barnacles on the larval exposure to food.Communicated by O. Kinne, Oldendorf/LuheAn erratum to this article can be found at     

Nitrogen-fixation by cyanobacteria associated withCodium fragile (Chlorophyta): Environmental effects and transfer of fixed nitrogen

N₂-fixation associated with the green macroalgaCodium fragile subsp.tomentosoides (van Goor) Silva from Long Island, New York, USA, was attributable to several species of endophytic cyanobacteria. Rates of N₂-fixation ranged from 0.03 to 3.2µg N g^–1 dry wt h^–1 in freshly collected plants from several sites. Growth of the cyanobacteria appeared to be light-limited, due to the transmission of only 5 to 10% of incident light through the pigmented surface-layer of the macroalga. Daily irradiance was the most important factor determining both abundance of cyanobacterial cells and rate of N₂-fixation. The rate was also affected by instantaneous irradiance, and increased twofold from dark to ambient surface irradiance. Rates were reduced at low temperature (8°C) but showed no temperature effect between 12° and 26°C. External concentrations of dissolved inorganic nitrogen (DIN) up to 20µM did not influence N₂-fixation rate, but long-term exposure to 60µmol l^–1 d^–1 of NH ₄ ⁺ caused a reduction in the rate. InC. fragile grown under high daily irradiance and low external DIN concentration, ~50% of the assimilated-N was attributable to N₂-fixation. However, chlorophyllb extracted from plants grown with¹⁵N₂ showed an atom % excess¹⁵N of less than 0.1, suggesting that only a small proportion of the bacterially fixed-N was transferred to the seaweed. The association betweenC. fragile and its endophytic cyanobacteria appears to be based primarily on microhabitat suitability, rather than mutual metabolic dependence. It is doubtful that N₂-fixation by cyanobacteria is important to the ecological success of this seaweed species.