Effects of temperature on hatching rate, embryonic development and early larval survival of the edible sea urchin, Tripneustes gratilla

The temperature tolerances of embryonic and early larval development stages of Tripneustes gratilla were investigated from 13-34°C under laboratory conditions. Zygotes showed unequal cleavage at 13°C, whereas cleavage did not occurred at 34°C. Hatching was observed between 16–31°C with maximum hatching rates observed at 22–29°C. The lower and higher temperature limits for embryonic development were approximately 22°C and 29°C, respectively. Outside of this temperature range, embryos showed abnormality at different incubation times. Early larvae of this species have the ability to survive the higher temperature limit for short periods of time. Prism and 2 arm pluteus larvae survived at temperatures between 30 and 33°C, whereas 4 arm pluteus larvae survived at temperatures between 30 and 36°C for 2 h. These results suggest that the larval temperature tolerance capability of T. gratilla is stage dependent. These findings are important for understanding the life history strategy of this sea urchin in the shallow open water environment.     

Molecular identification of symbiotic dinoflagellates (Symbiodinium spp.) from Palythoa spp. (Anthozoa: Hexacorallia) in Japan

In Japan, zooxanthellate Palythoa tuberculosa Klunzinger and Palythoa mutuki Verrill (Anthozoa: Hexacorallia: Zoantharia) are found over a 1,000 + km latitudinal range, often in environments where most other zooxanthellate anthozoans are not found (i.e. tidal lagoon pools, around shallow water hydrothermal vents, subtropical rocky shorelines). Sequences of internal transcribed spacer of ribosomal DNA (ITS-rDNA) of the symbiotic dinoflagellate genus Symbiodinium (zooxanthellae) Freudenthal (Order Suessiales) from P. tuberculosa and P. mutuki from several locations in Japan (34°11′N–24°16′N) were analysed. Unexpectedly, despite the ability of the genus Palythoa to be flexible in association with different Symbiodinium subclades, most (35 of 36) Palythoa investigated here specifically associate with subclade C1 and closely related types. Symbiodinium subclade C1 has been characterized as a “generalist” in terms of the ability to associate with a range of hosts, but present results suggest that subclade C1 may also be a “generalist” in terms of being able to live in a variety of environments over a latitudinal range. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Effects of ambient temperature and of temperature acclimation on nitrogen excretion and differential catabolism of protein and nonprotein resources in the intertidal snails,Littorina saxatilis (Olivi) and L. obtusata (L.)

Nitrogenous excretion in two snails, Littorina saxatilis (high intertidal) and L. obtusata (low intertidal) was studied in relation to temperature acclimation (at 4° and 21°C), including total N excretion rates, the fraction of urea in N excretion, corresponding O:N ratios and the partitioning of deaminated protein between catabolic and anabolic processes at 4°, 11° and 21°C. Aggregate N excretion rates in both species showed no significant compensatory adjustments following acclimation. Total weight specific N excretion rates at 21°C were higher in standard 3 mg L. saxatilis (739 ng N mg⁻¹ h⁻¹) than standard 5 mg L. obtusata (257 ng N mg⁻¹ h⁻¹) for snails acclimated to 21°C. Comparisons of Q₁₀ values of total weight specific N excretion to Q₁₀ values for weight specific oxygen consumption ({xxV}O₂) between 4° to 11 °C and 11° to 21°C indicated that, while total rates of catabolic metabolism ({xxV}O₂) and protein deamination in L. obtusata were essentially parallel, the relationship between N excretion and {xxV}O₂ in L. saxatilis revealed the partitioning of a larger share of deaminated protein carbon into anabolism at 4° and 21°C than at 11°C. Urea N accounted for a larger share of aggregate N excreted in L. saxatilis than in L. obtusata, but in both species urea N is a greater proportion of total N excreted when acclimated at 4°C (urea N: ammonia N ratio range: 1 to 2.15) than in snails acclimated to 21°C (urea N: ammonia N ratio range: 0.46 to 1.39). Molar O:N ratios indicate that the proportion of metabolism supported by protein catabolism is greater in L. saxatilis (O:N range: 2.5–8.4) than in L. obtusata (O:N range: 7.3–13.0). In both species, regardless of acclimation temperature, the O:N ratios are generally lowest (high protein catabolism) at 4°C and highest at 21°C.     

Foliage consumption and larval development of parasitized and unparasitized soybean looper,Pseudoplusia includens [Lep.: Noctuidae], reared on a resistant soybean genotype and effects on an associated parasitoid,Compidosoma truncatellum [Hym.: Encyrtidae]

Field grown foliage from the resistant soybean [Glycine max (L.) Merrill] breeding line GAT “81–327” and the susceptible cultivar “Ransom” was used to rear unparasitized larvae of the soybean looper (SBL),Pseudoplusia includens (Walker), and larvae parasitized byCopidosoma truncatellum (Dalman). SBL larvae, whether parasitized or not, consumed more foliage when fed “Ransom”. Unparasitized larvae reared on “81–327” had longer developmental times and suffered greater mortality than unparasitized larvae reared on “Ransom”. Parasitization of SBL larvae byC. truncatellum increased total foliage consumption of both soybean lines. Parasitized larvae reared on the resistant “81–327” weighed less and yielded fewer parasitoid adults.

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Résumé Des larves dePseudoplusia includens (Walker) parasitées ou non parCopidosoma truncatellum (Dalman) ont été nourries des feuilles de deux lignées de soja [Glycine max (L.) Merrill] l'une, GAT “81–327” résistante et l'autre, “Ransom” sensible. Les larves deP. includens qu'elles soient parasitées ou non consommaient plus de feuillage lorsqu'elles étaient nourries de la lignée “Ransom”. Les larves non parasitées élevées sur “81–327” avaient un cycle de développement beaucoup plus long et un taux de mortalité beaucoup plus élevé que les larves non parasitées élevées comparativement sur feuilles de “Ransom”. Par contre, les larves parasitées manifestaient une consommation accrue du feuillage des deux lignées de soja. Les larves parasitées élevées sur les feuilles de la variété résistante GAT “81–327” pesaient moins et produisaient moins également de parasites adultes.

     

Resting metabolism of helodermatid lizards: allometric and ecological relationships

We measured metabolic rates at 15 and 25°C in 42 helodermatid lizards ranging in mass from 26 to 1616 g. No consistent repeatable daily rhythms of metabolism were detected. There were no significant differences in metabolic rates between the two species of Heloderma. The temperature coefficient for metabolism (Q ₁₀) was 3.0 between 15 and 25°C. The mass exponent for helodermatids (0.69) differed significantly from the among-species mass exponent of 0.80 for all squamates combined. However, adult Heloderma had a mass exponent of 0.80. Rates of metabolism of adult helodermatids were lower than those of other squamate reptiles, and at 15°C periods of apnea contributed to a further reduction in metabolic rate. Our finding that helodermatids have low SMRs supports the hypothesis that ecology is important in influencing metabolic rate, and that “reclusive” squamates have lower rates of metabolism than do nonreclusive species.     

Effect of high temperature on photosynthesis and transpiration of sweet corn (<Emphasis Type="Italic">Zea mays</Emphasis> L. var. <Emphasis Type="Italic">rugosa</Emphasis>)

Four temperature treatments were studied in the climate controlled growth chambers of the Georgia Envirotron: 25/20, 30/25, 35/30, and 40/35 °C during 14/10 h light/dark cycle. For the first growth stage (V3-5), the highest net photosynthetic rate (P _N) of sweet corn was found for the lowest temperature of 28–34 μmol m⁻² s⁻¹ while the P _N for the highest temperature treatment was 50–60 % lower. We detected a gradual decline of about 1 P _N unit per 1 °C increase in temperature. Maximum transpiration rate (E) fluctuated between 0.36 and 0.54 mm h⁻¹ (≈5.0–6.5 mm d⁻¹) for the high temperature treatment and the minimum E fluctuated between 0.25 and 0.36 mm h⁻¹ (≈3.5–5.0 mm d⁻¹) for the low temperature treatment. Cumulative CO₂ fixation of the 40/35 °C treatment was 33.7 g m⁻² d⁻¹ and it increased by about 50 % as temperature declined. The corresponding water use efficiency (WUE) decreased from 14 to 5 g(CO₂) kg⁻¹(H₂O) for the lowest and highest temperature treatments, respectively. Three main factors affected WUE, P _N, and E of Zea: the high temperature which reduced P _N, vapor pressure deficit (VPD) that was directly related to E but did not affect P _N, and quasi stem conductance (QC) that was directly related to P _N but did not affect E. As a result, WUE of the 25/20 °C temperature treatment was almost three times larger than that of 40/35 °C temperature treatment.     

Biosorption of Cu(II) ions from synthetic and actual wastewater using three algal species

The use of three freshwater microalgal cultures—Chlorella sorokiniana, Anabaena laxa, and Hapalosiphon welwitschii—for sorption of copper(II) from synthetic Cu(II) solutions and Marinduque, Philippines, wastewater was studied. The optimum amount of biomass for the three species was 0.025 g dry weight. The optimum contact time for both C. sorokiniana and A. laxa was 1 h, whereas that of H. welwitschii was 30 min. All three species exhibited maximum Cu(II) sorption at pH 4.0–6.0. The Langmuir adsorption isotherm was the best fit model for the three species. The three cultures were found to be effective biosorbents when used in synthetic wastewaters of low concentration (10–30 ppm). Maximum Cu(II) reductions obtained were 88.2, 88.6, and 91.7% for the C. sorokiniana, A. laxa, and H. welwitschii cultures, respectively. C. sorokiniana, A. laxa, and H. welwitschii removed 5.70, 11.16, and 7.15% of Cu(II), respectively, when applied to wastewater taken from Consolidated Mines Inc. (CMI) containing around 150 ppm Cu(II). C. sorokiniana and A. laxa, in combination, exhibited 14.05% Cu(II) removal from CMI wastewater. Desorption with 0.11 M HCl effected 73.20, 64.54, and 70.85% removal of Cu(II) from the surfaces of C. sorokiniana, A. laxa, and H. welwitschii, respectively. SEM-EDS spectra of the three species confirmed the presence of Cu(II) on their surfaces. Presented at the 6th Meeting of the Asia Pacific Society of Applied Phycology, Manila, Philippines.     

The “Phoca standard”: An external molecular reference for calibrating recent evolutionary divergences

Comparison of the complete mitochondrial DNA (mtDNA) of the high-Arctic ringed seal (Phoca hispida) and the sub-Arctic harbour (P. vitulina) and grey (Halichoerus grypus) seals shows that they are genetically equidistant from one another. We relate the evolutionary divergence of the three species to expanding glaciation in the Arctic Basin and establish, in conjunction with mtDNA data, a standard reference for calibration of recent divergence events among mammalian taxa. In the present study, we apply the “Phoca standard” to the dating of divergences within the hominid phylogenetic tree. After determining the relative rates of substitution over all mitochondrial protein-coding genes in the different evolutionary lineages, we estimate that humans and chimpanzees diverged from each other 6.1 Mya (95% confidence limits: 5.2–6.9 Mya). The corresponding lower-limit divergence between common chimpanzee,Pan troglodytes, and pygmy chimpanzee,P. paniscus, occurred 3 (2.4–3.6) Mya, and the primary split within theP. troglodytes complex 1.6 (1.3–2.0) Mya. The analyses suggest that the split betweenGorilla andPan/Homo occurred 8.4 (7.3–9.4) Mya. They also suggest thatPongo (orangutan) and the lineage leading to gorillas, chimpanzees, and humans diverged 18.1 (16.5–19.6) Mya. The present analysis is independent of the hominid paleontological record and inferential morphological interpretations and thus is a novel approach to the lower-limit dating of recent divergences. Correspondence to: U. Arnason     

The influence of various temperature regimes on the abundance dynamics and thermal tolerance of cladoceran Ceriodaphnia quadrangula (O.F. Müller, 1785)

Experimental studies on the abundance dynamics and thermal tolerance of cladoceran Ceriodaphnia quadrangula (O.F. Müller, 1785) as they depend on the value and action pattern of a thermal factor, as well as field observations and mathematical calculations were carried out. Based upon the results of these studies, the values of the temperature zone of normal vital functions (17.0–25.0°C) and of the zones of temperature “static” optimum (21.4–25.0°C) were determined for C. quadrangula. It was shown using experimental populations of C. quadrangula as an example that it is necessary not only to keep the range of the factor optimal values within the tolerance scale (i.e., the static optimum) but also to maintain the optimal parameters of dynamic factor changes (or “dynamic optimum”) in order to form optimal conditions for their growth and development. For C. quadrangula this dynamic temperature optimum is 24.0 ± 1.1°C, with non-periodical (graded) warming to 24.7–25.3°C over five to eight days.     

Salinity and Temperature Effects on Germination for Three Salt-resistant Euhalophytes, Halostachys caspica, Kalidium foliatum and Halocnemum strobilaceum

The effects of three salinities (0, 100 and 500 mM NaCl) and four constant temperatures (10, 20, 30 and 35 °C) on seed germination of Halostachys caspica (M. B.) C. A. Mey., Kalidium foliatum (Pall.) Mop. and Halocnemum strobilaceum (Pall.) Bieb. were investigated. After seeds were treated with different concentrations of NaCl at constant temperatures of 10–35 °C for 16 days, ungerminated seeds were transferred to distilled water for 10 days to investigate the total germination; after this time, the ungerminated seeds from the 10 and 20 °C treatments were then moved to 35 °C for another 5 days to determine the final germination. The three plant species in the present experiment are salt-resistant euhalophytes growing in high saline soils in the Zhungur Basin in Xinjiang, a northwest province of China.Compared with germination under control conditions, germination percentages of all three species were not affected by 100 mM NaCl at 10–35 °C, while severely inhibited by 500 mM NaCl; germination percentages were very low at 10 °C up to 100 mM NaCl for all species; the optimum temperature for germination of H. caspica and K. foliatum was 20–30 °C, while 35 °C for H. strobilaceum, up to 100 mM NaCl; seeds did not suffer ion toxicity for all species, as evidenced by the high total germination after ungerminated seeds pretreated with 500 mM NaCl were transferred to distilled water at constant temperatures of 10–35 °C for 10 days, and the high final germination after the ungerminated seeds from the 10 and 20 °C treatments were subsequently moved to 35 °C for another 5 days; Halostachys caspica had greater sensitivity to increasing temperatures from 10 and 20 °C to 35 °C compared with the other two species.     

Agar properties of two species of Gracilariaceae from the Gulf of California,Mexico

Agar properties of two potentially commercial important seaweeds from the Gulf of California were studied. Maximum yield in Gracilaria vermiculophylla (45.7%) occurred during the summer months, coinciding with high water temperatures (31°C) whereas minimum yields (11.6%) were obtained during the coldest months of the year when populations of this species diminish in the bay. Gracilariopsis longissima showed two yield peaks, one in spring and another in fall, before the maximum and minimum seawater temperatures. Gel strength in native agar from the two species was low (<22.5 g cm⁻²) for most of the year. G. vermiculophylla native agar showed a slight increase in gel strength from June to August, which were the hottest months. Maximum value was 85 g cm⁻¹ in August. Maximum gel strength in G. longissima was observed in October (91 g cm⁻¹), and an unusual native agar with no detectable gel strength was observed in March and April samples. Gelling temperatures range from 27.7 to 36.5°C in G. vermiculophyla and from 26.6 to 34.9°C in G. longissima, meanwhile melting points were 73.9 – 53.5°C and 75.5 – 56.6°C, respectively. Sulfate content was high, 6.3–13.9% in G. vermiculophylla and 1.9–11.9% in G. longissima, and on the other hand 3,6 anhydrogalactose content was low 12.1–26.7% and 9.1–23%, respectively compared to other species. Results obtained showed that mean native agar yields of Gracilaria vermiculophylla and Gracilariopsis longissima from the Gulf of California are comparable to other tropical Gracilaria. However, the low gel strength, high sulfate content and low 3,6 anhydrogalactose content observed in the native agar extracted from these species make this an agaroid, thus alternative methods of extraction should be used to evaluate the possibility of commercial utilization of both species.     

Effect of temperature on the development, fecundity, progeny sex ratio and life-table of Campoletis chlorideae, an endolarval parasitoid of the pod borer, Helicoverpa armigera

Development, survival, fecundity, progeny sex ratio (PSR) and age-specific life-table parameters of the parasitoid Campoletis chlorideae Uchida (Hymenoptera: Ichneumonidae) were examined at six different constant temperatures (12, 17, 22, 27, 32 and 37°C) in the laboratory [70 ± 10% RH and 10:14 h (light:dark) photoperiod]. Second instar larvae of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) were reared on chickpea (Cicer arietinum L.) and used as the host. Development times shortened as the temperature increased from 12 to 37°C. The estimated lower developmental threshold (tL) was 3.4°C. The thermal summation for total immature stages was 379.97 degree-days. A reciprocal relationship between temperature and longevity was observed in the range of 12–17°C. The maximum mortality of pupae (71.8%) occurred at 37°C. At 22°C, the yield of a female parasitoid averaged 137.3 ± 14.7 (mean ± SD) progeny, of which 89.6 ± 7.6 were daughters. The number of daughters produced decreased when the females were kept either above or below 22°C, although the PSR was female biased in the range of 17–27°C. The analyses of life-table parameters, developmental rates, reproduction, mortality and PSR suggest that maximum population growth (r _m ) is near 27°C. There was little variation observed in most of the desired qualities of C. chlorideae in the range of 17–27°C, and it appears that the parasitoid is adapted to a wide range of temperatures. We suggest that for maximum production the parasitoid should be reared at 22 ± 4°C and be released in areas where the temperature ranges between 17° and 27°C, as in the plains of northern India.     

Early development of germlings of <Emphasis Type="Italic">Sargassum thunbergii</Emphasis> (Fucales,Phaeophyta) under laboratory conditions

Morphology and culture studies on germlings of Sargassum thunbergii (Mertens et Roth) Kuntze were carried out under controlled laboratory conditions. Growth characteristics of these germlings grown under different temperatures (from 10 to 25°C), irradiances (from 9 to 88 μmol photons m⁻² s⁻¹), and under blue and white light conditions are described. The development of embryonic germlings follows the classic “8 nuclei 1 egg” type described for Sargassaceae. Fertilized eggs spent 5–6 h developing into multicellular germlings with abundant rhizoids after fertilization. Under conditions of 20°C, 44 μmol photons m⁻² s⁻¹ and photoperiod of 12 h, young germlings with one or two leaflets reached 2–3 mm in length after 8 weeks. Temperature variations (10, 15, 20, 25°C) under 88 μmol photons m⁻² s⁻¹ significantly influenced the growth rate within the first week, although this effect became less obvious after 8 weeks, especially at 15 and 20°C. Variation in germling growth was highly significant under different irradiances (9, 18, 44, 88 μmol photons m⁻² s⁻¹) at 25°C. Low temperature (10°C) reduced germling growth. Growth of germlings cultured under blue light was lower than in white light. Optimal growth of these germlings occurred at 25°C and 44 μmol photons m⁻² s⁻¹.     

Lack of metabolic temperature compensation in the intertidal gastropods,Littorina saxatilis (Olivi) and L. obtusata (L.)

Two intertidal snails, Littorina saxatilis (Olivi, 1972) (upper eulittoral fringe/maritime zone) and Littorina obtusata (Linnaeus, 1758) (lower eulittoral) were collected from a boulder shore on Nobska Point, Cape Cod, Massachusetts, in July and acclimated for 15–20 days at 4 ° or 21 °C. Oxygen consumption rate (Vo₂) was determined for 11–15 subsamples of individuals at 4 °, 11 ° and 21 °C with silver/platinum oxygen electrodes. Multiple factor analysis of variance (MFANOVA) of lo₁₀ transformed values of whole animal Vo₂ with log₁₀ dry tissue weight (DTW) as a covariant revealed that increased test temperature induced a significant increase in Vo₂ in both species (P<0.00001). In contrast, MFANOVA revealed that temperature acclimation did not affect Vo₂ in either L. saxatilis (P= 0.35) or L. obtusata (P= 0.095). Thus, neither species displayed a capacity for the typical metabolic temperature compensation marked by an increase in Vo₂ at any one test temperature in individuals acclimated to a lower temperature that is characteristic of most ectothermic animals. Lack of capacity for metabolic temperature acclimation has also been reported in other littorinid snail species, and may be characteristic of the group as a whole. Lack of capacity for respiratory temperature acclimation in these two species and other littorinids may reflect the extensive semi-diurnal temperature variation that they are exposed to in their eulittoral and eulittoral fringe/maritime zone habitats. In these habitats, any metabolic benefits derived from longer-term temperature compensation of metabolic rates are negated by extreme daily temperature fluctuations. Instead, littorinid species appear to have evolved mechanisms for immediate metabolic regulation which, in L. saxatilis and L. obtusata and other littorinids, appear to centre on a unique ability for near instantaneous suppression of metabolic rate and entrance into short-term metabolic diapause at temperatures above 20–35 °C, making typical seasonal respiratory compensation mechanisms characteristic of most ectotherms of little adaptive value to littorinid species.     

A Modified PCR System for Amplifying <Emphasis Type="Italic">β</Emphasis>-ketoacyl-ACP Synthase Gene Fragments with DNA from <Emphasis Type="Italic">Streptomyces luteogriseus</Emphasis>

Streptomyces luteogriseus strain 099, producing a new type of macrolide antibiotic with anti-coxB6 virus and anti-HIV protease activities, was isolated from soil. PCR was optimized to amplify β-ketoacyl-ACP synthase (KS) genes. The system was optimized around the use of higher concentrations of DMSO (15% vs. 10% v/v) and dNTP (500 μM vs. 50–200 μM) and a lower annealing temperature (55 °C vs. 60–70 °C) than the normal PCR method used to amplify high GC content DNA.     

Distribution Patterns of Isomorphic Cold-Water Dinoflagellates (Scrippsiella/Woloszynskia Complex) Causing ‘red tides’ in the Baltic Sea

During the latest years medium-sized (15–30 μm), single-celled dinoflagellates have been reported to form blooms in the northern Baltic Proper and the Gulf of Finland in winter and spring. Recent studies (Kremp et al., 2003. Proceedings of the 7th International conference of Modern and Fossil Dinoflagellates, September 21–25, Nagasaki, Japan, 66 pp.) indicate that those blooms are caused by two isomorphic species – Scrippsiella hangoei (Schiller) Larsen, and a new species, tentatively belonging to the genus Woloszynskia. Until now there has been no report on how widely distributed these phytoplankton species are in the Baltic Sea. In this study, the occurrence of Scrippsiella/Woloszynskia complex in the entire Baltic Sea was investigated, by using monitoring data from 1997 to 2003. The species occurred in a salinity range from 2 to 8 PSU. Highest concentrations were observed at salinity 4.5–6.5 PSU. Maximum cell densities of Scrippsiella/Woloszynskia complex in the water column were mainly obtained in April or in the beginning of May by the water temperature <3 °C prior to stratification was formed. In the central Gulf of Finland, the second maximum was found in 1999 and 2002 by the temperature >6 °C. Bloom formations in the Baltic Proper and in the Gulf of Finland may not only be explained by optimum temperature and salinity, but also with other factors e.g. high nutrient concentrations and good seeding conditions from the sediments.     

Final thermal preference in parthenogenetic females of Daphnia magna straus (Crustacea: Cladocera) acclimated to various temperatures

The final thermal preference FTP) range in parthenogenetic females of cladoceran Daphnia magna was assessed by “acute” and “chronic” methods. The first method included 4-month acclimation to different temperatures in the range of 14.2 ± 0.7 to 27.1 ± 0.3°C; the “chronic” method was characterized by long-term acclimation to +20°C. Two ranges of FTP were found for D. magna, 13.3–15.4°C and 20.2–26.2°C. The thermal preference of daphnids and the temperature of acclimation were correspondingly linearly. The range of FTP was independent of the season. The searching activity of D. magna rose in April, when the FTP range increased, and the FTP was less pronounced.     

Early thermal history significantly affects the seasonal hyperplastic process occurring in the myotomal white muscle of <Emphasis Type="Italic">Dicentrarchus labrax</Emphasis> juveniles

The effect of early (embryonic and larval) thermal history on subsequent (juvenile) white muscle hyperplasia was studied in a teleost fish, the European sea bass (Dicentrarchus labrax L.). D. labrax, incubated and reared at constant temperatures of 13°C, 15°C or 20°C from the embryonic stage of half epiboly up to 18–19 mm in total length, were transferred to ambient seawater temperature and reared for the subsequent 14 months on commercial feed. The somatic growth of juveniles was linked to annual variations of ambient seawater temperature and inversely related to early rearing temperature, so that, after 14 months, the juveniles originally reared at low temperatures had compensated for the growth retardation experienced during early life. The white muscle growth process of juveniles was quantified after two periods of growth opportunity at ambient seawater temperature (100 and 400 days post-transfer) as well as, in order to follow total-length-dependent effects of early temperature and to discriminate total-length-independent effects of early temperature, on juveniles from the three batches sampled at six successive equivalent total lengths (31–33, 84–88, 141–145, 166–172, 196–206 and 211–220 mm). Our data demonstrate the existence of a seasonal recruitment of new white muscle fibres when seawater temperature increases and of a shrinkage of the largest white muscle fibres during the winter months. The seasonal recruitment of new white muscle fibres occurring in juveniles is linked to their early rearing temperature. Juveniles originating from low temperatures have a higher and longer capacity to recruit new white muscle fibres when seawater temperature increases, supporting their better somatic growth. This finding is discussed in relation to the early (embryonic and larval) myogenic processes of the three populations and is related to their sex ratio. This work was financed by the European Commission, FAIR Program no. PL96–1941 “Muscle Ontogeny in Sea bass and Trout”.     

Thermal acclimation to 4 or 10°C imparts minimal benefit on swimming performance in Atlantic cod (Gadus morhua L.)

Thermal acclimation is frequently cited as a means by which ectothermic animals improve their Darwinian fitness, i.e. the beneficial acclimation hypothesis. As the critical swimming speed (U _crit) test is often used as a proxy measure of fitness, we acclimated Atlantic cod (Gadus morhua) to 4 and 10°C and then assessed their U _crit swimming performance at their respective acclimation temperatures and during acute temperature reversal. Because phenotypic differences exist between different populations of cod, we undertook these experiments in two different populations, North Sea cod and North East Arctic cod. Acclimation to 4 or 10°C had a minimal effect on swimming performance or U _crit, however test temperature did, with all groups having a 10–17% higher U _crit at 10°C. The swimming efficiency was significantly lower in all groups at 4°C arguably due to the compression of the muscle fibre recruitment order. This also led to a reduction in the duration of “kick and glide” swimming at 4°C. No significant differences were seen between the two populations in any of the measured parameters, due possibly to the extended acclimation period. Our data indicate that acclimation imparts little benefit on U _crit swimming test in Atlantic cod. Further efforts need to identify the functional consequences of the long-term thermal acclimation process.