Effects of salinity on rates of protein synthesis and oxygen uptake in the post-larvae and juveniles of the tropical prawn Macrobrachium rosenbergii (de Man)

Protein synthesis is a major determinant of growth and yet little is known about the environmental factors that influence protein synthesis rates in farmed freshwater prawns. To this end, post-larvae and juveniles of Macrobrachium rosenbergii were exposed to various salinities (0, 14, 30‰) to determine whole-animal rates of fractional protein synthesis (k_s) and oxygen uptake. In the post-larvae that migrate upstream from brackish to freshwater areas, whole-animal k_s was unaffected by salinity, but rates of oxygen uptake were significantly lower at 14‰. In the freshwater juveniles, a different response was observed, as mean k_s was significantly higher at 14‰ compared with 0‰, but rates of oxygen uptake remained unchanged. Such differences are thought to be related to the energetic costs of osmoregulation and to the ability to maintain osmotic gradients in freshwater. In an additional experiment, acclimation temperature (20, 26, 30 °C) had a direct effect on k_s in juveniles held at 0‰. In all cases, changes in k_s resulted from alterations in RNA activity at constant RNA capacity. In juveniles at least, whole-animal rates of protein synthesis were highest at 14‰ and 30 °C which corresponds to the optimal salinity and temperature recommended for the growth and culture of M. rosenbergii.     

Effects of temperature,salinity and their interaction on growth of Japanese Gambierdiscus spp. (Dinophyceae)

Marine toxic dinoflagellates of the genus Gambierdiscus are the causative agents of ciguatera fish poisoning (CFP), a seafood poisoning that is widespread in tropical, subtropical and temperate regions of the world. In the main island of Japan, distributions of Gambierdiscus australes, Gambierdiscus scabrosus and two phylotypes of Gambierdiscus spp. type 2 and type 3, have been reported. To discuss the bloom dynamics of these Japanese species/phylotypes of Gambierdiscus, first we tested six culture media to optimize growth conditions and then clarified the effects of temperature and salinity and temperature–salinity interactions on growth. All strains of the species/phylotypes tested showed the highest cell yields when they were cultivated in IMK/2 medium. G. australes, G. scabrosus and Gambierdiscus sp. type 2 grew in the range 17.5–30 °C, whereas Gambierdiscus sp. type 3 grew in 15–25 °C. The semi-optimal temperature ranges (≥80% of the maximal growth rate) of the former three species/phylotypes were 19–28 °C, 24–31 °C and 21–28 °C, respectively, whereas that of the latter phylotype was 22–25 °C. Hence, Gambierdiscus sp. type 3 may be adapted to relatively lower water temperatures of ≤25 °C. In contrast, G. australes, G. scabrosus and Gambierdiscus sp. type 2 presumably possess adaptability to relatively high water temperatures. The optimal temperature for G. scabrosus was 30 °C, whereas the optimal temperature for the others was 25 °C. G. australes and Gambierdiscus sp. type 3 grew in a salinity range of 25–40 whereas G. scabrosus and Gambierdiscus sp. type 2 grew in salinity 20–40. Furthermore, the semi-optimal salinity range of G. australes, G. scabrosus, Gambierdiscus spp. type 2 and type 3 were salinity 27–38, 24–36, 22–36 and 29–37, respectively. Among the species/phylotypes, G. scabrosus and Gambierdiscus sp. type 2 grew even at salinity 20 where the others did not grow, thus possessing adaptability to low salinity waters. Our results clearly demonstrate that the optimal and tolerable temperature–salinity conditions differ among Japanese Gambierdiscus species/phylotypes. Considering these results, temperature–salinity interactions may play an important role in bloom dynamics and the distribution of the Gambierdiscus species/phylotypes in Japanese coastal waters.     

Survival,haemolymph osmolality and tissue water of Penaeus chinensis juveniles acclimated to different salinity and temperature levels

Survival, growth, haemolymph osmolality and tissue water of Penaeus chinensis (Osbeck) juveniles (0.11 ± 0.04 g) were investigated, after they were acclimated to 10, 20, 30 and 40 ppt from 33 ppt for 14 days at 24°C, and then acclimated to 12, 18, 24 and 30°C at each salinity for 14 days. The survival of shrimp was the lowest at 10 ppt and 12°C. Growth of shrimp increased with increased temperature in the range 12–24°C, with no significant difference among four salinity levels at 18, 24 and 30°C. Haemolymph osmolality increased with increased salinity, and decreased with increased temperature. The isosmotic point computed from the linear relationship between haemolymph osmolality and medium osmolality was 664, 632, 629 and 602 mOsm/kg which is equivalent to 25.2, 24.1, 24.0 and 23.1 ppt at 12, 18, 24 and 30°C, respectively. Tissue water decreased with increased medium osmolality and haemolymph osmolality. The slope obtained from the relationship between haemolymph osmolality and medium osmolality indicated that there is an impairment of osmoregulatory ability for the P. chinensis juveniles at 12°C.     

Growth and thermal tolerance of a Tibet fish Schizopygopsis younghusbandi juveniles acclimated to three temperature levels

Schizopygopsis younghusbandi is an endemic fish of Tibet characterized by slow growth. Artificial stock enhancement was applied to rebuild the natural population of S. younghusbandi in recent years. However, the optimal growth temperature and thermal tolerance of S. younghusbandi has not been studied, which restricts the production of S. younghusbandi fingerling for stock enhancement. The purpose of this paper is to determine the growth, critical thermal maximum (CTMax), lethal thermal maximum (LTMax) and acclimation response ratio (ARR) of S. younghusbandi juveniles (body weight 5.7 ± 1.2 g) at three acclimation temperature levels (10, 15, 20°C). The results showed that acclimation temperature significantly affected the growth, CTMax, LTMax and ARR of the experimental fish. Largest final weight (7.5 ± 2.3 g) was recorded in 15°C group. At a heating rate of 1°C/30 min, CTMax ranged from 30.98 to 32.01°C and LTMax ranged from 31.76 to 32.31°C in the three acclimation temperatures. Schizopygopsis younghusbandi had lower ARR value (0.097) than most other fish species. Low ARR value indicates that S. younghusbandi may have narrower thermal tolerance range and weaker acclimation ability to global warming. For successful aquaculture of S. younghusbandi juveniles, temperature should be maintained around 15°C.     

Thermal tolerance,growth and oxygen consumption of Labeo rohita fry (Hamilton, 1822) acclimated to four temperatures

A 30 day feeding trial was conducted using a freshwater fish, Labeo rohita (rohu), to determine their thermal tolerance, oxygen consumption and optimum temperature for growth. Four hundred and sixteen L. rohita fry (10 days old, 0.385±0.003 g) were equally distributed between four treatments (26, 31, 33 and 36 °C) each with four replicates for 30 days. Highest body weight gain and lowest feed conversion ratio (FCR) was recorded between 31 and 33 °C. The highest specific growth rate was recorded at 31 °C followed by 33 and 26 °C and the lowest was at 36 °C. Thermal tolerance and oxygen consumption studies were carried out after completion of growth study to determine tolerance level and metabolic activity at four different acclimation temperatures. Oxygen consumption rate increased significantly with increasing acclimation temperature. Preferred temperature decided from relationship between acclimation temperature and Q₁₀ values were between 33 and 36 °C, which gives a better understanding of optimum temperature for growth of L. rohita. Critical thermal maxima (CTMax) and critical thermal minima (CTMin) were 42.33±0.07, 44.81±0.07, 45.35±0.06, 45.60±0.03 and 12.00±0.08, 12.46±0.04, 13.80±0.10, 14.43±0.06, respectively, and increased significantly with increasing acclimation temperatures (26, 31, 33 and 36 °C). Survival (%) was similar in all groups indicating that temperature range of 26–36 °C is not fatal to L. rohita fry. The optimum temperature range for growth was 31–33 °C and for Q₁₀ values was 33–36 °C.     

Effect of rearing temperature on growth and thermal tolerance of Schizothorax (Racoma) kozlovi larvae and juveniles

Effect of rearing temperature on growth and thermal tolerance of Schizothorax (Racoma) kozlovi Nikolsky larvae and juveniles was investigated. The fish (start at 12 d post hatch) were reared for nearly 6 months at five constant temperatures of 10, 14, 18, 22 and 26 °C. Then juvenile fish being acclimated at three temperatures of 14, 18 and 22 °C were chosen to determine their critical thermal maximum (CTMax) and lethal thermal maximum (LTMax) by using the dynamic method. Growth rate of S. kozlovi larvae and juveniles was significantly influenced by temperature and fish size, exhibiting an increase with increased rearing temperature, but a decline with increased fish size. A significant ontogenetic variation in the optimal temperatures for maximum growth were estimated to be 24.7 °C and 20.6 °C for larvae and juveniles of S. kozlovi, respectively. The results also demonstrated that acclimation temperature had marked effects on their CTMax and LTMax, which ranged from 32.86 °C to 34.54 °C and from 33.79 °C to 34.80 °C, respectively. It is suggested that rearing temperature must never rise above 32 °C for its successful aquaculture. Significant temperature effects on the growth rate and thermal tolerance both exhibit a plasticity pattern. Determination of critical heat tolerance and optima temperature for maximum growth of S. kozlovi is of ecological significance in the conservation and aquaculture of this species.     

Acute Toxicity of Arsenic under Different Temperatures and Salinity Conditions on the White Shrimp Litopenaeus vannamei

The aim of this study was to determine acute toxicity in the post larvae of the white shrimp Litopenaeus vannamei after 96 h of exposure to dissolved arsenic under three different temperatures and salinity conditions. Recent reports have shown an increase in the presence of this metalloid in coastal waters, estuaries, and lagoons along the Mexican coast. The white shrimp stands out for its adaptability to temperature and salinity changes and for being the main product for many commercial fisheries; it has the highest volume of oceanic capture and production in Mexican shrimp farms. Lethal concentrations (LC₅₀–96 h) were obtained at nine different combinations (3?×?3 combinations in total) of temperature (20, 25, and 30 °C) and salinity (17, 25, and 33) showing mean LC₅₀–96 h values (±standard error) of 9.13?±?0.76, 9.17?±?0.56, and 6.23?±?0.57 mgAs?L^?1(at 20 °C and 17, 25, and 33 salinity); 12.29?±?2.09, 8.70?±?0.82, and 8.03?±?0.59 mgAs?L^?1 (at 25 °C and 17, 25, and 33 salinity); and 7.84?±?1.30, 8.49?±?1.40, and 7.54?±?0.51 mgAs?L^?1 (at 30 °C and 17, 25, and 33 salinity), respectively. No significant differences were observed for the optimal temperature and isosmotic point of maintenance (25 °C–S 25) for the species, with respect to the other experimental conditions tested, except for at 20 °C–S 33, which was the most toxic. Toxicity under 20 °C–S 33 conditions was also higher than 25 °C–S 17 and 20 °C (S 17 or 25). The least toxic condition was 25 °C–S 17. All this suggests that the toxic effect of arsenic is not affected by temperature changes; it depends on the osmoregulatory pattern developed by the shrimp, either hyperosmotic at low salinity or hiposmotic at high salinity, as observed at least on the extreme salinity conditions here tested (17 and 33). However, further studies testing salinities near the isosmotic point (between 20 and 30 salinities) are needed to clarify these mechanisms.     

Life history characteristics of the western flower thrips,Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), under fluctuating conditions of temperature or relative humidity

Frankliniella occidentalis (Pergande) is a major insect pest of greenhouse crops such as leaf vegetables, flowers and vegetable fruits worldwide. The life history characteristics of F. occidentalis were investigated at control temperature and humidity (27.3 ± 0.54 °C, 79.9 ± 2.79% RH) (mean ± SD), a 10 °C-range fluctuation in temperature (27.1 ± 5.28 °C, 81.5 ± 4.03% RH), a 20 °C-range fluctuation in temperature (26.5 ± 10.09 °C, 80.4 ± 5.76% RH), a 20%-range fluctuation in humidity (26.8 ± 0.37 °C, 80.7 ± 9.55% RH) and a 30%-range fluctuation in humidity (27.3 ± 0.41 °C, 76.3 ± 15.28% RH). Overall, the life history traits of F. occidentalis were more negatively affected by fluctuating environmental conditions. The impact of temperature fluctuation was more severe than that of humidity fluctuation. Additionally, the degree of impact increased as the fluctuation range of the temperature increased, while the reverse trend was observed with humidity fluctuations. With the 20 °C-range fluctuation in temperature, F. occidentalis died at the 1st instar larval stage. The offspring’s sex ratio was significantly higher at the 20%- and 30%-range fluctuations in humidity (0.47 and 0.49, respectively) compared to the control (0.35) and at the 10 °C-range fluctuation in temperature (0.33). From the fertility life table analysis, the intrinsic rate of increase (r) was higher at the 30%-range fluctuation in humidity and control conditions as 0.218 and 0.205, respectively. At the 10 °C-range fluctuation in temperature conditions, r was significantly lower as 0.169. High fluctuations in temperature and low fluctuations in humidity appear to be the best conditions for controlling F. occidentalis populations in greenhouses.     

Optimization of cultivation conditions for fatty acid composition and EPA production in the eustigmatophycean microalga Trachydiscus minutus

We determined the effects of cultivation conditions (nitrogen source, salinity, light intensity, temperature) on the composition of polyunsaturated fatty acids (PUFAs) and the production of eicosapentaenoic acid (EPA) in the laboratory cultured eustigmatophycean microalga, Trachydiscus minutus. T. minutus was capable of utilizing all nitrogen compounds tested (potassium nitrate, urea, ammonium nitrate, ammonium carbonate) with no differences in growth and only minor differences in fatty acid (FA) compositions. Ammonium carbonate was the least appropriate for lipid content and EPA production, while urea was as suitable as nitrates. Salinity (0.2 % NaCl) slightly stimulated EPA content and inhibited growth. Increasing salinity had a marked inhibitory effect on growth and PUFA composition; salinity at or above 0.8 % NaCl was lethal. Both light intensity and temperature had a distinct effect on growth and FA composition. The microalga grew best at light intensities of 470–1,070 μmol photons m^?2 s^?1 compared to 100 μmol photons m^?2 s^?1, and at 28 °C; sub-optimal temperatures (20, 33 °C) strongly inhibited growth. Saturated fatty acids increased with light intensity and temperature, whereas the reverse trend was found for PUFAs. Although the highest level of EPA (as a proportion of total FAs) was achieved at a light intensity of 100 μmol photons m^?2 s^?1 (51.1?± 2.8 %) and a temperature of 20 °C (50.9?±?0.8 %), the highest EPA productivity of about 30 mg L^?1?day^?1 was found in microalgae grown at higher light intensities, at 28 °C. Overall, for overproduction of EPA in microalgae, we propose that outdoor cultivation be used under conditions of a temperate climatic zone in summer, using urea as a nitrogen source.     

Temperature-dependent functional response of Diglyphus isaea and Hemiptarsenus zilahisebessi parasitizing Liriomyza sativae

This study was conducted to address the effect of different constant temperatures (15, 20, 25, 30 and 35 °C) on the functional response of the parasitoid wasps Diglyphus isaea Walker and Hemiptarsenus zilahisebessi Erdös to different densities of Liriomyza sativae Blanchard (2, 4, 8, 16, 32 and 64 larvae) under laboratory conditions. The results revealed the Type II functional response for both parasitoids at different temperatures. The highest searching efficiency for D. isaea and H. zilahisebessi occurred at 25 °C (0.926 ± 0.211 h⁻¹) and 30 °C (1.012 ± 0.241 h⁻¹), respectively. In addition, the shortest handling time for D. isaea and H. zilahisebessi were observed at 25 °C (0.063 ± 0.008 h) and 30 °C (0.058 ± 0.008 h), respectively. These results demonstrated that H. zilahisebessi is more efficient at higher temperatures than D. isaea. Both parasitoids had higher parasitism performance when temperature increased (4.67 parasitized hosts/day at 15 °C vs 15.87 parasitized hosts/day at 25 °C for D. isaea and 3.89 parasitized hosts/day at 15 °C vs 17.24 parasitized hosts/day at 30 °C for H. zilahisebessi). In addition, a quadratic regression was found between handling time and temperature as well as between number of the parasitized larvae and temperature in D. isaea and H. zilahisebessi at different densities of L. sativae. This study provided a preliminary information on the parasitic behavior of these parasitoids and that D. isaea and H. zilahisebessi can be used properly beside other non-chemical approaches to manage L. sativae damage at a temperature range of 25–30 °C, respectively.     

Effect of salinity on the thermoregulatory behavior of juvenile blue shrimp Litopenaeus stylirostris Stimpson

Preferred temperature (PT) of juveniles of Litopenaeus stylirostris was not modified (P>0.05) by salinity. The final preferendum of juveniles was 27.8 °C.The critical thermal maxima (CTMax) determined at 42 combinations (6 temperatures×7 salinities) in blue shrimp was not affected significantly by salinity (P>0.05). We obtained a direct relationship between the CTMax and the acclimation temperature.The end point of CTMax in L. stylirostris was defined as the loss of righting response (LRR).The acclimation response ratio (ARR) for the juveniles of blue shrimp had an interval of 0.45–0.50, values that agreed with others obtained for crustaceans from tropical and sub tropical climates.     

Thermal response and horizontal transmission of cameroonian isolates of the entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae – Candidates for microbial controls of the banana root borer Cosmopolites sordidus

Beauveria bassiana and Metarhizium anisopliae are two promising microbial agents for biopesticides development against the banana root borer Cosmopolites sordidus. In this study, germination, mycelial growth, and sporulation of six local Cameroonian isolates of those two species were assessed under seven different thermal conditions (13, 15, 20, 25, 29 33, and 37 °C) to select thermo-tolerant isolates. The Transmission potential of the thermo-tolerant isolates was determined at 25 ± 1 °C by dipping adult weevils in conidial suspensions (3.2 × 10⁸) conidia/ml and mixing these with uninoculated weevils in different proportions (0, 10, 30 and 50%), in groups of 30, and assessing the spread of the mycosis within the group over 35 d of co-incubation. Incubation temperature and isolates significantly affected germination, mycelial growth and conidial production. All isolates had large thermal tolerance ranges (13–33 °C) except MIITAC6.4.2 (20–29 °C). Horizontal transmission resulted in mortality of non-inoculated weevils from 4.63 ± 1.77 to 53.3 ± 11.9%. The isolate BIITAC6.2.2 exhibited high auto-dissemination potential and high conidia yield in cadavers. These results demonstrate the potential use of these isolates for biopesticides development against C. sordidus in Central Africa.     

The effect of salinity on the growth rate of the macroalgae Enteromorpha intestinalis (Chlorophyta) in the Mondego estuary (west Portugal)

The excessive growth of opportunistic macroalgae in estuaries and other coastal areas, characterised by enormous values of vegetal biomass in the form of dense mats, is a common and widespread picture nowadays. In such conditions, macroalgae completely dominate the nutrient dynamics in the ecosystem and function as high quality food for the microbial, meio- and macrofaunal communities. Due to their important role in the nutrient pathways of the ecosystems, it becomes essential to obtain new information on variables and processes that regulate the bloom formation of these primary producers. The Mondego estuary (west Portugal) is a eutrophic estuary, where usually macroalgae of the genera Enteromorpha seasonally bloom. Nevertheless, in years with high precipitation characterised by a significant increase of the freshwater runoff to the system, no Enteromorpha blooms are observed. Possible explanations for this are related to the reduction of light in the water column, high water speed, high sediment turbulence and low salinity values. Thus, because the decrease in salinity seemed an important feature during such periods, a set of experiments were conducted, to evaluate to what extent the growth of Enteromorpha intestinalis (the most abundant species in the Mondego estuary) is affected by fluctuations in salinity and, particularly, by low salinity values. In the laboratory, the growth rate of E. intestinalis was tested against a range of salinity, from 0 to 32 psu. E. intestinalis showed the lowest growth rates at extreme low salinity values (≤ 3 psu) and for salinity ≤ 1 psu, the algae died. Growth rates at salinity lower than 5 psu and higher than 25 psu were also low, when compared with growth between salinity of 15 and 20 psu, where E. intestinalis showed the highest growth rates. These results agree with the field observations and suggest that, in the Mondego estuary, salinity is an important external parameter to control the growth of E. intestinalis, which has important ecological implications for the system.     

Life tables and development of <Emphasis Type="Italic">Amblyseius swirskii</Emphasis> (Acari: Phytoseiidae) at different temperatures

Development time, reproduction, survival and sex ratio were determined for the omnivorous mite Amblyseius swirskii at nine constant temperatures (13, 15, 18, 20, 25, 30, 32, 34 and 36°C) on pepper leaf disks with cattail, Typha latifolia, pollen for food. These data were used to derive life table parameters at these constant temperatures. No development was observed at 13°C. The lower development threshold, based on the fit to the linear portion of the development curve, was 11.3°C. The upper development threshold was 37.4 ± 1.12°C, and the optimum temperature was calculated to be 31.5°C. Average lifetime fecundity ranged from a low of 1.3 ± 0.24 eggs/female at 15°C to a high of 16.1 ± 0.34 eggs/female at 25°C, and r _m was greatest at 32°C. Non-linear regression of the relationship between temperature and r _m produced an estimate of 15.49 ± 0.905°C for the lower threshold for population growth and 36.99 ± 0.816°C for the upper threshold for population growth, and an optimum temperature of 30.1°C. These values suggest that A. swiskii populations should grow quickly in response to food availability (pollen or prey) between 20 and 32°C, but that, especially below 20°C, population growth could be slow and impacts on prey populations should be monitored carefully.     

Effects of temperature and salinity on the eggs and early larvae of Caranx mate (Cuv. & Valenc.) (pisces: carangidae) in Hawaii

Eggs and larvae of the carangid fish, Caranx mate (Cuv. & Valenc.), were incubated at various temperature (17.2 to 33.1 °C) and salinity (10 to 42 ‰) combinations in five experiments. The following rates were directly proportional to temperature: embryonic development, yolk absorption, eye and jaw development, and increase in length. Unfed C. mate larvae attained a maximum size at 25 °C and 20 ‰ Eyes and jaws of larvae were functional by the end of the yolk sac stage at all temperature and salinity levels tested.Hatching success and larval survival at the end of the yolk sac stage were generally greater than 50 % between 22° and 32°C. Hatching success and larval survival at the end of the yolk sac stage were reduced at salinity extremes, especially in low temperature-low salinity and high temperature-high salinity combinations. The frequency of morphological abnormalities was also high at extreme temperatures and salinities.The incipient upper thermal TL_m for unfed C. mate larvae acclimated to 23.8°C increased from 31.5°C for newly hatched larvae, to 34.2°C for 72 h larvae, but decreased to 32.0°C for starving larvae after the exhaustion of the yolk supply.     

Determining the optimum temperature and salinity for larval culture,and describing a culture protocol for the conservation aquaculture for European smelt Osmerus eperlanus (L.)

Populations of anadromous European smelt Osmerus eperlanus (L.) are declining across its geographical range in northern Europe, but no practical culture techniques exist to develop stock enhancement programmes for this species. In this study, a culture protocol is described to rear fish from fertilised eggs to mature adults in 2 years involving the use of ‘green water’, live feed and artificial diets. The sequence of embryonic development for eggs incubated at 10°C/0 ppt was described and photographed. To determine the optimum conditions for larval culture, fertilised eggs were reared at a range of salinities (0–20 ppt) and temperatures (5–18°C) until first feeding. Best hatching success (ca. 97%), size at hatch (ca. 0.8 mm) and survival to first feeding (ca. 96%) of larvae were achieved under combined conditions of low salinity (0–0 ppt) and temperature (5–10°C). No larvae survived a salinity of 20 ppt. The time taken from fertilisation to hatch (FtH) and hatching duration (HD) were temperature-dependent ranging from 42 days FtH and 10 days HD at 5ºC, to 10 days FtH and 2 days HD at 18°C irrespective of salinity. The results indicate that conservation programmes could utilise existing salmonid hatchery facilities (i.e. freshwater, ≤10°C water temperature) for stock enhancement. Since on-growing of smelt involves the logistical and technical problems of live feed production, it is recommended that smelt enhancement programme utilise freshwater hatchery facilities to rear fish until hatching, and then stock out onto known spawning grounds in rivers allowing hatched larvae to drift into estuaries to complete the larval and juvenile phases. This approach would minimise the time spent in the hatchery post-hatching, eliminate the need for live food production, prevent the development of predator-naïve fish, and hence would mimic the natural life cycle of the species as closely as possible.     

Adaptivity of the bivalve Mytilus trossulus larvae to short-and long-term changes in water temperature and salinity

Adaptivity to short-term and long-term changes in water temperature and salinity was studied in larvae of the bivalve mollusk Mytilus trossulus. It was shown that water temperature of 4°C mostly suppressed growth and development of larvae. A temperature of 20°C promoted an enhanced larval growth and development. Though a temperature of 20°C caused enhanced larval growth, the temperature was not optimal, while its effect caused quality diversity of larval development, owing to the difference in their growth rates. Such diversity was not observed at moderate temperatures of 10 and 15°C. At 20°C, fast-growing mussel larvae were very sensitive to temperature drops. Growth of slowly-growing individuals did not depend on temperature in the range of 10 to 20°C. Daily temperature variations by 3–8°C did not markedly affect growth and development of the larvae. A continuous 24-h exposure to temperature drops by 3–8°C did not influence these very important physiological characteristics either. A salinity drop down to 8‰ exerted an adverse effect only on early larvae. Later on, the larvae showed their ability to adapt to such a strong desalination. The negative effect of reduced salinity (to 8‰) upon mussel larvae was increased at a temperature increase to 20°C.     

Environmental controls on growth and lipid content for the freshwater diatom, Fragilaria capucina: A candidate for biofuel production

The use of microalgae for biofuel production has the potential to reduce fossil fuel consumption. Ideal candidate species of microalgae for bio-oil production need both relatively high growth rates and lipid content. Here, we report on the effects of temperature, nutrients (N, Si), and salinity on growth rates and lipid content of the common freshwater diatom, Fragilaria capucina (Desm), isolated from western Lake Erie. At low NaCl salinity, growth rate increased rapidly from 10 to 20°C, and then further increased slowly from 20 to 30°C, with a maximum specific growth rate of 0.61?day^?1. Growth rate declined with increasing salinity (e.g., reduced by ca. 50 and 100% at 137 and 274?mmol?L^?1 NaCl, respectively), and increased with increased N and Si concentration until ca. 100?μmol?L^?1 for each (with >85% of maximum growth rate at 10?μmol?L^?1). Lipid content (% total lipid per dry mass) in nutrient-replete cultures was 14% and (1) increased to >30% at low N and, especially, low Si; (2) was lower at 30°C vs. 20 or 10°C; and (3) decreased with salinity. Thus, F. capucina accumulates lipid to high levels even under N, Si, and temperature levels that permit a high growth rate for this species, and hence, this species is a candidate for use in biofuel production.     

Incubation temperature fluctuation does not affect incubation length and hatchling phenotype in the Chinese skink Plestiodon chinensis

Studies examining the effects of incubation temperature fluctuation on the phenotype of hatchling reptiles have shown species variation. To examine whether incubation temperature fluctuation has a key role in influencing the phenotype of hatchling Chinese skinks (Plestiodon chinensis), we incubated eggs produced by 20 females under five thermal regimes (treatments). Eggs in three treatments were incubated in three incubators, one set constant at 27 °C and two ramp-programmed at 27±3 °C and 27±5 °C on a cycle of 12 h (+) and 12 h (−). The remaining eggs were incubated in two chambers: one inside a room where temperatures varied from 23.0 to 31.1 °C, with a mean of 27.0 °C; the other outside the room where temperatures varied from 20.2 to 35.3 °C, with a mean of 26.1 °C. We found that: (1) for eggs at a given embryonic stage at ovipositon, the mean rather than the variance of incubation temperatures determined the length of incubation; (2) most (egg mass, embryonic stage at oviposition, incubation length and all examined hatchling traits except tail length and locomotor performance) of the examined variables were affected by clutch; and (3) body mass was the only hatchling trait that differed among the five treatments, but the differences were tiny. These findings suggest that incubation temperature fluctuation has no direct role in influencing incubation length and hatchling phenotype in P. chinensis.     

Effects of extreme changes of sea water temperature and salinity on the development of the sand dollar <Emphasis Type="Italic">Scaphechinus mirabilis</Emphasis>

The combined effects of temperatures of 14, 17, 20, 22, and 25°C and salinities of 36–12‰ on embryos and larvae of the sand dollar Scaphechinus mirabilis was studied. Embryonic development is the most sensitive stage in the early ontogenesis of S. mirabilis. It is completed at a temperature of 14–20°C in a salinity range of 36–24‰ and at temperature of 22°C to 26‰. The fertilization proceeds in wider ranges of temperature and salinity. Among the swimming larvae, blastulae showed the greatest resistance to variations of these environmental factors. All the larvae survived at a temperature of 14–22°C and a salinity of 36–20‰, and more than 70% of them at 18‰. The pluteus I is the most vulnerable stage; probably this is related to the formation of the larval skeleton and transition to phytoplankton feeding. The survival of larvae at the age of 20 days was 100% at 14–22° C and a salinity of 36–24‰, most of them survived at 14–20°C and a salinity 18‰. The temperature 25 ° C is the most damaging for early development of S. mirabilis. The duration of development of that species lasts 28.5–29 days at 20°C and a salinity of 32.2–32.6‰. At 20 and 22°C, the larvae settled and completed metamorphosis more quickly if sand from the parental habitat was present. The larvae did not settle during the experiment (14 days) at 14 ° C and in the absence of sand.