Effect of nitrate fertilization of gametophytes of the kelp Undaria pinnatifida on growth and maturation of the sporophytes cultivated in Matsushima Bay, northern Honshu, Japan

In northern Japan, the early production of high-quality specimens of kelps Undaria pinnatifida prior to the outbreak of pinhole disease is needed. To address this need, we tested the effect of nitrate fertilization of gametophytes on the growth and maturation of sporophytes using experimental and control gametophytes derived from sporophytes cultivated in Matsushima Bay, northern Honshu, Japan. From mid-August to October 2008, experimental gametophytes were cultured on a rope indoors at a nitrate concentration of 1 mg/L at the optimal seawater temperature of 20 °C, whereas control gametophytes were cultured without the addition of nitrate in normal seawater at an average temperature of 23.5 °C during this period in the past 30 years. Next, the seedlings were cultivated in Matsushima Bay until March 2009. For the experimental kelps, the total length, stipe length, stipe width, sporophyll length, sporophyll width, and dry weight of the blade, midrib, and sporophyll increased significantly from December to January compared to those of control kelps. Matured sporophylls of the experimental kelps were more than those of the control kelps from early December to late January. Significant higher photosynthesis occurred at seawater temperatures of 10 and 15 °C, as well as higher uptake rates of NO₃–N of the experimental kelps in December and January. These results show that nitrate fertilization of the gametophytes makes it possible to harvest the high-priced blade, midrib, and sporophyll in January, which is earlier than the traditional harvest date.     

Variation in morphology and PSII photosynthetic characteristics of Macrocystis pyrifera during development from gametophyte to juvenile sporophyte

Currently, there is increasing demand for brown kelp, especially Macrocystis spp., to support the development of the abalone industry and for use as raw material for the production of alginate. Thus, there is a need to supplement the naturally available kelp biomass with the development of mariculture techniques. In this study, we investigated whether it was possible to cultivate Macrocystis pyrifera sporophytes in the laboratory using gametophyte clones. We propagated gametophytes by periodic fragmentation and then mixed aseptically an equal number of male and female gametophytes to induce fertilization. Approximately 60 days after fertilization, numerous embryonic sporophytes emerged on the seed fibre. By using chlorophyll fluorescence technology, we investigated variation in the photosystem II (PSII) characteristics of M. pyrifera during development from the gametophyte to juvenile sporophyte stage. During this growth period, both the optimal (F_v/F_m) and effective (YII) PSII quantum yields increased significantly from the haploid gametophyte to diploid sporophyte stages. In addition, by comparing female gametophytes with male gametophytes, we found that female gametophytes were not only larger and more pigmented than the males, but also recorded higher values of F_v/F_m and YII. Our results supplemented information on the life cycle and PSII photosynthetic performance during the early development and confirmed the possibility of artificial seeding technology, both of which may contribute to mariculture of M. pyrifera in China in the near future.     

Influence of temperature on growth and survival of juvenile winter flounder,Pseudopleuronectes americanus (Walbaum) reared under continuous light

Winter flounder, Pseudopleuronectes americanus, has emerged as a promising candidate flatfish for cold‐water aquaculture and restocking. Here, juveniles were reared for 8 weeks at three temperatures: 10, 15, and 20°C under 24‐hr light. All fish were imaged at stocking and at 2‐week intervals, where growth was measured as changes in standard length (S_L) and body area (B_A). By week 2, fish reared at 15 and 20°C were larger than those grown at 10°C. At weeks 4 to 6, fish at 15°C were larger than fish at 20°C. Linear regressions were used to model growth dynamics over time at each temperature. Highly significant linear growth trajectories were detected over time for S_L and B_A. S_L and B_A regressions also showed a significant difference among the slopes across temperatures, where comparing slopes showed the best temperature to rear the flounder was 15°C. Weights of fish held at 15°C and 20°C were greater than at 10°C at the termination of the experiment. Within each temperature, the growth rate of malpigmented fish was not different from that of the normally pigmented fish. Overall, growth of winter flounder was comparable to that of other commercially produced flatfish species, providing strong evidence for this flatfish species as a potential species for aquaculture.     

Stepwise temperature regulation and its effect on growth,feeding and muscle growth patterns of juvenile Atlantic halibut (<Emphasis Type="Italic">Hippoglossus hippoglossus</Emphasis> L.)

To investigate the possible direct effect of a stepwise reduction in temperature with increasing size on growth, feeding parameters and muscle growth patterns of juvenile Atlantic halibut (Hippoglossus hippoglossus L.), 804 juvenile halibut (mean initial weight individuals: 14.2 g ± 0.2 SEM) were reared at constant 9, 12 and 15°C or shifted (T-step, i.e. 15–12°C after 36 days) for 99 days. Despite indications of lower optimal temperature for growth with increasing size, equal end weights were obtained between the constant 12°C, constant 15°C and T-step groups. Best overall growth was observed for the group kept at constant 12°C. The limited effect of the T-step group may relate to the size at movement (too big), the temperatures investigated (close to optimum) and the time and size interval investigated (too narrow). Differences in growth were reflected more by alterations in feed intake (C _T and F%) than by differences in feed conversion efficiencies (FCE). Differences were found with respect to the density of muscle cells, whereas no differences were found between the average muscle cell diameters. The mean diameter of muscle cells tended to increase only slightly with increasing fish weight, while the mean density of muscle cells tended to decrease. Using an optimum temperature of 12°C, an indication of a possible increased rate of hyperplasia in relation to higher growth was seen.     

Patterns of growth and nutrient deposition in lake trout (Salvelinus namaycush), brook trout (Salvelinus fontinalis) and their hybrid, F1 splake (Salvelinus namaycush × Salvelinus fontinalis) as a function of water temperature

Several fish species of the genus Salvelinus are used for stocking freshwaters in North and South America and much of Europe but there is little information about their growth and carcass composition. Lake trout (S. namaycush), brook trout (S. fontinalis) and their hybrid F₁ splake (S. namaycush × S. fontinalis) (initial body weight ca. 2–4 g) were raised at 6.4, 10.6 and 14.9 °C to examine growth and nutrient deposition as a function of water temperature. In all species, weight gain and feed intake increased significantly with water temperature and feed efficiency was significantly lower at 6.4 than at 10.6 and 14.9 °C. In brook trout, Thermal‐unit Growth Coefficient (TGC) growth rate was significantly lower at 6.4 than at 10.6 and 14.9 °C, while in F₁ splake TGC was only lower at 6.4 than 10.6 °C. Expressed in terms of relative composition a significant effect of temperature was observed. In all species, moisture content decreased while crude protein, lipid, ash and energy contents increased with increased temperature. Expressed in absolute terms, however, a significant effect of temperature was not observed. In all species carcass contents increased significantly with increased live body weight and were best described by simple linear equations. Gross energy concentration was significantly affected by both water temperature and body weight. These data indicate that the growth of these species is a function of water temperature and, in absolute terms, carcass composition is mainly a function of body weight and not water temperature. Also, such simple linear equations bode well for modification of existing feed requirement and waste outputs models; improving their applicability to these species.     

Pharmacokinetics and tissue residues of marbofloxacin in crucian carp (Carassius auratus) after oral administration

Pharmacokinetics and residue elimination of marbofloxacin (MBF) were studied in crucian carp (Carassius auratus, 250±30 g) kept at two water temperatures of 15 and 25 °C. Marbofloxacin concentrations in plasma and tissues were analysed by means of high‐performance liquid chromatography using an ultraviolet detector. The limits of detection were 0.02 μg mL^?1, 0.02 μg g^?1, 0.025 μg g^?1, 0.02 μg g^?1 and 0.025 μg g^?1 in plasma and muscle, skin, liver and kidney respectively. Fish were administered orally at a single dosage of 10 mg kg^?1 body weight in the PK group. The data were fitted to two‐compartment open models at both temperatures. At 15 °C, the absorption half‐life () and distribution half‐life (t_1/2α) of the drug were 0.36 and 4.48 h respectively. The corresponding values at 25 °C were 0.23 and 0.87 h respectively. The elimination half‐life (t_1/2β) was 50.75 h at 15 °C and 25.05 h at 25 °C. The maximum MBF concentration (C_max) differed little between 15 (6.43 μg mL^?1) and 25 °C (8.36 μg mL^?1). The time to peak concentration was 1.74 h at 15 °C and 0.78 h at 25 °C. The apparent volume of distribution (V_d/F) of MBF was estimated to be 1.36 and 0.87 L kg^?1 at 15 and 25 °C respectively. The area under the concentration–time curve (AUC) was 301.80 μg mL^?1 h at 15 °C and 182.80 μg mL^?1 h at 25 °C. The total clearance of MBF was computed as 0.03 and 0.05 L h^?1 kg^?1 at 15 and 25 °C respectively. After repeated oral administration at a dosage of 10 mg kg^?1 body weight per day for 3 days, the results showed that the elimination half‐lives () of MBF from all tissues at 15 °C were longer than that at 25 °C. Therefore, water temperature is an important factor to be considered when deciding a reasonable withdrawal time.     

Dietary value of gametophytes and juvenile sporophytes of the brown macroalga <Emphasis Type="Italic">Eisenia bicyclis</Emphasis> for juvenile abalone <Emphasis Type="Italic">Haliotis diversicolor</Emphasis>

The dietary value of juvenile stages (gametophyte and juvenile sporophyte) of the brown macroalga Eisenia bicyclis for post-larval and juvenile abalone Haliotis diversicolor of 2.0–6.5 mm in shell length (SL) was examined and compared with that of a benthic diatom, Nitzschia sp., in laboratory experiments. Most abalone actively fed on these diets, but there were large variations in the growth rate among the diets and among the growth stages of abalone. Growth rates of abalone fed on Nitzschia sp. were highly variable within each growth stage, but showed no clear differences among growth stages. In contrast, in abalone fed gametophytes or juvenile sporophytes, growth rates linearly increased as abalone grew. Growth rates of >60 μm SL/day were observed in juveniles of >3 mm SL fed gametophytes, and juveniles of >5 mm SL fed juvenile sporophytes. These results indicate that the dietary value of the juvenile stages of E. bicyclis for the abalone changes as they grow, and with growth juvenile abalone begin to efficiently utilize gametophytes and juvenile sporophytes in that order.     

Algal density alleviates the elevated CO2‐caused reduction on growth of Porphyra haitanensis (Bangiales,Rhodophyta), a species farmed in China

Growing of Pyropia haitanensis, a commercially farmed macroalga, usually increases their densities greatly during cultivation in natural habitats. To explore how the increased algal densities affect their photosynthetic responses to rising CO₂, we compared the growth, cell components and photosynthesis of the thalli of P. haitanensis under a matrix of pCO₂ levels (ambient CO₂, 400 ppm; elevated CO₂, 1,000 ppm) and biomass densities [low, 1.0 g fresh weight (FW) L^?1; medium, 2.0 g FW L^?1; high, 4.0 g FW L^?1]. Under ambient CO₂, the relative growth rate (RGR) was 5.87% d^?1, 2.32% d^?1 and 1.51% d^?1 in low, medium and high densities, and elevated CO₂ reduced the RGR by 27%, 25% and 12% respectively. Maximal photochemical quantum yield of photosystem II (F_V/F_M) was higher in low than in high densities, so were the light‐utilized efficiency (α), saturation irradiance (E_K) and maximum relative electron transfer rate (rETR_max). Elevated CO₂ enhanced the F_V/F_M in low density but not in higher densities, as well as the α, E_K and rETR_max. In addition, elevated CO₂ reduced the content of chlorophyll a and enhanced that of carotenoids, but unaffected phycoerythrin, phycocyanin and soluble proteins. Our results indicate that the increased algal densities reduced both the growth and the photosynthesis of P. haitanensis and alleviated the elevated CO₂‐induced negative impact on growth and positive impact on photosynthesis. Moreover, the elevated CO₂‐induced reduction on growth and promotion on photosynthesis indicates that rising CO₂ may enhance the loss of photosynthetic products of P. haitanensis through releasing organic matters.     

Effects of diet and temperature on post‐settlement growth and survival of the short‐spined sea urchin Strongylocentrotus intermedius

Effects of diet and temperature on post‐settlement growth and survival of a sea urchin Strongylocentrotus intermedius, which fed on one of six mono‐cultured benthic diatoms, gametophytes of a brown alga Undaria pinnatifida, a green alga Ulvella lens plus mixed benthic diatoms, or no food at 6, 9, 12 and 15°C, were examined. Digestion efficiency (DE), ingestion rate (IR), excretion rate (ER) and digested cell content index (DCCI) of each diatom species were measured. Growth rates largely differed among the dietary treatments from 7 days post‐settlement. Sea urchins fed on a diatom Cocconeis sublittoralis showed considerably higher growth (7.85‐34.67 μm day^?1) than those fed on the other diets and high survival rates (100%). DCCI was also highest in C. sublittoralis. These results suggest that the quantity of diatom cell contents digested is an important factor affecting growth and survival of the sea urchins. Growth rates of sea urchins were higher in higher water temperatures, and significant differences in growth rate were observed between 6‐9 and 12‐15°C. ERs of C. sublittoralis were generally higher at higher temperatures, but DEs did not differ among the temperature treatments. Variations in growth rate among different water temperature appear to be caused by different food intakes of the urchins.     

Changes in mitochondrial fatty acid composition following temperature acclimation of carp and their possible effects on FoF1-ATPase activity

Carp undergo temperature acclimation of respiratory function by altering mitochondrial ATP synthase (F_oF₁-ATPase) both quantitatively and qualitatively (Itoi et al. 2003). To address such acclimation temperature-dependent changes of F_oF₁-ATPase activity, we investigated in this study the correlation between the fatty acid composition and F_oF₁-ATPase activity in fast muscle of thermally acclimated carp. The quantities of saturated fatty acids of mitochondria from carp acclimated to 10 °C were significantly lower than those of carp acclimated to 30 °C. While mono- and poly-unsaturated fatty acids tended to increase with cold acclimation of carp, the molar concentration of 16:0 aldehyde in mitochondria from the 10 °C-acclimated carp were less than those from the 30 °C-acclimated fish. The specific activities of F_oF₁-ATPase in the 10 °C- and 30 °C-acclimated fish mitochondria were calculated to be 167±22 and 56±10 nmol/min ⋅ mg mitochondrial protein, respectively, the difference being significant at P<0.005. Taken together, the increase in F_oF₁-ATPase activity in fast muscle mitochondria of carp after cold temperature acclimation may be closely related to the increase of unsaturated fatty acids in mitochondria. Abbreviations: BSA - bovine serum albumin; DHA - docosahexaenoic acid; EGTA - ethyleneglycol bis(2-aminoethylether)tetraacetic acid; EPA - eicosapentaenoic acid; F_oF₁-ATPase - mitochondrial ATP synthase; α-F₁-ATPase - F_oF₁-ATPase α-subunit; β-F₁-ATPase - F_oF₁-ATPase β-subunit; HEPES - 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid; SDS - sodium dodecyl sulfate; SDS-PAGE - SDS-polyacrylamide gel electrophoresis. This revised version was published online in July 2006 with corrections to the Cover Date.     

Temperature tolerance of young sporophytes from two populations of Laminaria japonica revealed by chlorophyll fluorescence measurements and short-term growth and survival performances in tank culture

The cold-water subtidal brown alga Laminaria japonica has been commercially farmed in the Far East and has been on top of all marine-farmed species in terms of farming area and annual output worldwide. The successful trials of transplantation of young sporophytes from the north to the south in winter along the Chinese coast in the 1950s led to the spreading of cultivation activities down to a latitude of 25–26°N. Up to today, nearly 50% of the annual output of this farmed alga, as a cold-water species, comes from the sub-tropical south in China. The demand to have high-temperature-tolerant strains/ecotypes in farming area calls for a practical method to judge and select the desired parental plants for breeding programs and for seedling production. In this paper, we report our results on using chlorophyll fluorescence measurement and short-term growth performance in tank culture to estimate the temperature tolerance of offspring from two populations, Fujian Farmed Population (FFP) sampled from Fujian province (latitude: 25–26°N) in subtropical area and Qingdao Wild Population (QWP) sampled from Qingdao (latitude: 36°N). Contrary to what has been usually thought, the results revealed that offspring from Qingdao wild population in the north showed better performance both in short-term growth and survival rates and in optimal quantum efficiency (F_v / F_m) when exposed to higher temperature (20–25 °C). This result was further confirmed by fluorescence quenching analysis. QWP distributed along the southern distribution limit at a latitude of 36°N in the Pacific west coast is thus taken as a more ideal one than the farmed population in subtropical region as a source of parental plants for breeding high-temperature-tolerant varieties.     

The effect of different numbers of feeding days on feed consumption and growth of rainbow trout [Oncorhynchus mykiss (Walbaum)]

A trial was conducted to evaluate the effects of the number of feeding days on feed consumption and growth of rainbow trout, Oncorhynchus mykiss (Walbaum) (initial mean weight 53.6 ± 11.3 g). Fish were held under natural winter–spring (40°57′N) photoperiod (L:8 D:16 – L:14 D: 10) and ambient water temperatures (4–12 °C) for 128 days, and fed on day 7 (F₇), day 5 (F_5.1: no feeding on weekends and F_5.2: no feeding on Sundays and Wednesdays) or every other day (F_EOD). Feeding treatments were replicated with 50 fish held in 200‐L tanks. Number of feeding days affected final live weight, with fish in group F₇ achieving a mean weight of 285.6 g, followed by F_5.1 (256.6 g), F_5.2 (247.6 g) and F_EOD (223.2 g). Final condition factors (CF) differed between the F_EOD group and the others. Feed conversion ratios (FCR) exhibited significant differences among some of the groups. The results suggest that depriving rainbow trout of feed for more than 1 day a week has a negative effect on growth, but little influence on feed conversion.     

Effects of body size and water temperature on food consumption and growth in the sea cucumber Apostichopus japonicus (Selenka) with special reference to aestivation

To investigate the effects of body size and water temperature on feeding and growth in the sea cucumber Apostichopus japonicus (Selenka), the maximum rate of food consumption in terms of energy (C_maxe; J day^?1) and the specific growth rate in terms of energy (SGRe; % day^?1) in animals of three body sizes (mean±SE) – large (134.0±3.5 g), medium (73.6±2.2 g) and small (36.5±1.2 g) – were determined at water temperatures of 10, 15, 20, 25 and 30°C. Maximum rate of food consumption in terms of energy increased and SGRe decreased with increasing body weight at 10, 15 and 20°C. This trend, however, was not apparent at 25 and 30°C, which could be influenced by aestivation. High water temperatures (above 20°C) were disadvantageous to feeding and growth of this animal; SGRe of A. japonicus during aestivation was negative. The optimum temperatures for food consumption and for growth were similar and were between 14 and 15°C, and body size seemed to have a slight effect on the optimal temperature for food consumption or growth. Because aestivation of A. japonicus was temperature dependent, the present paper also documented the threshold temperatures to aestivation as indicated by feeding cessation. Deduced from daily food consumption of individuals, the threshold temperature to aestivation for large and medium animals (73.3–139.3 g) was 24.5?25.5°C, while that for small animals (28.9–40.7 g) was between 25.5 and 30.5°C. These values are higher than previous reports; differences in sign of aestivation, experimental condition and dwelling district of test animals could be the reasons.     

Physiological differences between gametophytes and sporophytes of five cultivar strains of Saccharina japonica

The demand for high‐yield cultivars of Saccharina japonica in farming areas calls for a practical and simple method to select desired parental plants for seed breeding. In this study, we evaluated PSII photosynthetic performance by measuring chlorophyll fluorescence and the nutrient uptake rate in both the micro‐gametophyte and macro‐young‐sporophyte in five native strains (S1, S2, S3, S4 and S5) of S. japonica with different morphological characteristics. We found significant differences in PSII photosynthetic parameters and nitrate uptake rates between the strains studied in both gametophytes and young sporophytes. Female gametophytes of all strains presented larger cell sizes than males (P < 0.05). Among all tested strains, S2 presented the largest cell sizes and highest levels of PSII photosynthetic parameters and nutrient uptake rates in female gametophytes and young sporophytes. In open sea cultivation, S2 presented the greatest width and largest fresh weight values but the lowest thickness among all strains studied. Correlation analysis further indicated that the algal fresh weight showed strong positive relationships with cell size (R² > 0.747), the PSII photosynthetic parameters of female gametophytes (R² > 0.689) and the nitrate uptake rate of young sporophytes (R² = 0.640). These findings are considered promising for the future seed breeding of renewable, high‐yield strains.     

Effects of light intensity,stocking density and temperature on the air-bubble disease,survivorship and growth of early juvenile seahorse Hippocampus erectus Perry, 1810

This investigation examined the effects of light intensity, stocking density and temperature on the air-bubble disease, survivorship and growth of early juveniles (2–30 days old) of seahorse Hippocampus erectus Perry. The juveniles in the 100 lx treatment had the highest air-bubble disease rate of 20.8 ± 6.2% and the juveniles in the 500 lx treatment had the highest survival rate of 84.4 ± 5.5%. The juvenile seahorses cultured in the 1500 lx treatment had the highest final wet weight of 0.13 ± 0.02 g and the highest final standard length of 4.54 ± 0.37 cm (F_{7, 144}=57.406, F_{7, 144}=12.315, P<0.05). There was no significant effect of stocking density on the air-bubble disease rate (F_{6, 21}=1.893, P=0.126). The juveniles cultured in the 1 ind L⁻¹ had the highest wet weight increment of 0.134 ± 0.031 g, but juveniles in the 2 ind L⁻¹ had the highest standard length increment of 3.17 ± 0.30 cm (F_{6, 126}=34.902, F_{6, 126}=11.726, P<0.05), and juveniles cultured in the 1.5 ind L⁻¹ had the highest survival rate of 86.1 ± 4.6%. The result of interaction of light intensity and temperature showed that the juveniles cultured in the 1500 lx and 26 °C had the highest weight gain and specific growth rate of 3791.17 ± 323.97% and 13.07 ± 0.18, respectively, and the lowest air-bubble disease rate of 9.3 ± 4.5% occurred in the 1000 lx and 26 °C (F_{8, 36}=12.355, P<0.05).     

Effect of rearing temperatures on the growth and maturation of Arctic charr (Salvelinus alpinus) during juvenile and on‐growing periods

The effect of rearing temperature on the growth and maturation of Arctic charr (Salvelinus alpinus) was investigated. Arctic charr juveniles were reared for 6 months (phase I, October–April, size range 20–500 g) at constant temperatures of 9, 12 and 15 °C and according to two temperature‐step groups (T_step) i.e. fish transferred from 15 to 12 °C or from 12 to 9 °C. All the previous treatments were then reared either at 7 °C or at 12 °C for an additional 4 months (phase II, size range 300–1000 g) and then slaughtered in August 2008. The overall growth rate was the highest at a constant temperature of 15 °C for the first 6 months of the trial, with the fish in this group being 44% and 78% heavier than the fish reared at a constant temperature of 12 or 9 °C respectively. Arctic charr showed a negative response in terms of the growth rate when transferred from higher to lower temperatures, especially for groups previously reared at 15 °C. There was a trend for higher gonadosomatic index values at the end of the experiment for groups of fish that were exposed to higher rearing temperatures during the juvenile phase i.e. 4.18% (±0.79) and 7.29% (±0.89), for the temperature groups of 12 and 15 °C, respectively, compared with 2.49% (±0.74) for the 9 °C group. Our results suggest that for the production of fish >1000 g, moderate or low temperatures (here 9 °C) should be applied during the juvenile phase in order to reduce the negative effects arising from maturation. Farmers with access to heat sources should accordingly choose more moderate rearing temperatures during the juvenile stage, especially if the fish is to be moved down in the temperature regime during the on‐growing period.     

Effects of temperature on food consumption, growth and oxygen consumption of freshwater prawn Macrobrachium rosenbergii (de Man 1879) postlarvae

Effects of temperature on food consumption, growth and oxygen consumption were estimated for the freshwater prawn Macrobrachium rosenbergii postlarvae at 23 °C, 28 °C and 33 °C in the laboratory. The results showed that the animal's initial body weight had a close linear relationship with food consumption and growth. Food consumption increased directly with temperature. Consumption rates (C; mg day^?1 ind^?1 ) of the 28 °C and 33 °C groups were much higher than that of the 23 °C group (P < 0.001), and the 33 °C group's consumption rate was higher than that of the 28 °C group (P < 0.05). The relationship of food consumption with temperature and initial body weight (W; mg) could be described as: C = 0.0679W + 0.185t? 3.17. Growth increased significantly with increased temperature. The relationship among specific growth rate, temperature and initial body weight was as follows: SGR = ?0.110W + 0.213t + 0.176. However, temperature showed no effect on growth efficiency. Oxygen consumption increased significantly with temperature (P < 0.01). The weight‐specific oxygen consumption rates (mg O₂ g^?1 h^?1) at 23 °C, 28 °C and 33 °C were 0.83, 1.16 and 1.49 mg O₂ g^?1 h^?1 for 61.92 mg M. rosenbergii.     

The combined effects of temperature and salinity on embryos and larvae of the black-lip pearl oyster, Pinctada margaritifera (L.)

This paper reports on a 4 × 4 factorial design experiment conducted to examine the combined effects of temperature and salinity on embryonic development and growth and survival of black-lip pearl oyster, Pinctada margaritifera (L.) larvae. The temperatures used were 20 °C, 25 °C, 30 °C and 35 °C, and the salinities were 25°/_oo, 30°/_oo, 35°/_oo and 40°/_oo. Response surface contour diagrams were generated from the survival and growth data to estimate optimal conditions. Normal development of embryos occurred only from 25 °C to 30 °C. The optimal conditions for maximum survival and growth were 26–29 °C and 28–32°/_oo. Temperatures of 35 °C or greater were lethal for larvae and, at all temperatures tested, larval growth and survival were lowest at a salinity of 40°/_oo.     

The effect of temperature on the energy budget of the Manila clam, <Emphasis Type="Italic">Ruditapes philippinarum</Emphasis>

In this study, the energy budget of the Manila clam, Ruditapes philippinarum, was evaluated after one-week acclimation periods at 5, 10, 15, 20, and 25°C. Small clams (151 ± 12 mg DW) and large clams (353 ± 16 mg DW) were fed with the microalgae, Isochrysis galbana. Filtration rate, ingestion rate, assimilation efficiency, oxygen-consumption rate, and ammonia excretion rate were measured. Both filtration rate and ingestion rate of small and large clams were found to be related to temperature. The highest Q ₁₀ values were measured in the range 15–20°C for both small and large clams. Assimilation efficiency of both small and large clams was not significantly influenced by temperature, although the maximum mean values were detected at 20°C. Oxygen consumption rate and ammonia excretion rate of small and large clams were found to be related directly to temperature over the entire range, with a maximum being detected at 25°C. The highest Q ₁₀ value was estimated in the range 10–15°C with regard to oxygen consumption rate, and in the range of 15–20°C with regard to ammonia excretion rate. Scope for growth (SFG) was positive at all temperatures, achieving a maximum value at 20°C in both small and large clams, primarily as a consequence of the enhanced ingestion rate which offset the concomitant elevation in the metabolic rate. In this study we have estimated the thermal optimum for this species at 20°C.     

Effects of air exposure on the lysosomal membrane stability of haemocytes in blacklip abalone, Haliotis rubra (Leach)

The neutral red retention (NRR) assay was used to evaluate the effects of air exposure on lysosomal membrane integrity in the haemolymph of blacklip abalone, Haliotis rubra, and its subsequent recovery in water. After acclimation in 16°C water for 7 days, abalone were exposed to an air temperature of 7, 16 or 23°C for 12 h in the air exposure experiment or to these three air temperatures, e.g., for 12, 24 or 36 h, followed by re‐immersion in 16°C water in the lysosomal membrane stability recovery experiment. Statistical analyses of the air exposure experiment showed that when abalone were exposed to different air temperatures (7, 16 or 23°C), the lysosomal membrane stability was significantly affected by the air temperature, the exposure duration and their interaction. Air temperature similar to the acclimation temperature had a significantly lower impact on the lysosomal membrane stability within the initial 4.5 h in comparison with the other two temperatures in the same period. The lysosomal membrane stability recovery experiment showed that after air exposure durations of 12, 24 or 36 h, the re‐stabilization of the lysosomal membrane was faster in the animals exposed to lower temperatures than those exposed to higher temperatures. The recovery of the lysosomal membrane stability in abalone exposed to lower 7°C air temperature was not significantly affected (F_{2, 66}=0.251, P=0.779) by the exposure durations (12, 24 and 36 h) used in this study. Alternatively, the lysosomal membrane stability in abalone exposed to higher air temperatures of 16 or 23°C recovered at a faster rate when subjected to shorter durations of air exposure (F_{2, 66}=3.663, P=0.031 and F_{1, 44}=17.057, P<0.001 for 16 and 23°C respectively).