Prediction, from temperature, of eyeing, hatching and 'swim-up' times for salmonid embryos

SUMMARY. 1. The literature contains a number of curves relating time (days) required for median hatch (=D₂) to water temperature (T,°C) for the eggs of several salmonid fishes. There are relatively few data on the relationships between time to median eyed (= D₁), days) or time to median swim-up (= D₃, days) and temperature.
2. From published data, over most of the range 0-9.5°C, approximate relationships are D,=0.5D₂ for Atlantic salmon (Salmo salar L.) and D3 = 1.7D₂ for eight species of Salmo and Oncorhynchus.
3. Field and hatchery tests suggest that these are useful empirical models for approximate prediction of D₁ and D₃ from D₂ for most salmonids.     

A desk study of the relationship between temperature and hatching time for the eggs of five species of salmonid fishes

SUMMARY. Information on temperature (T°C) and time from fertilization to 50% hatch ( D days) for five species of salmonid fishes has been used to assess several mathematical models relating D and T . No single equation gave the best fit to all five data sets. The power law with temperature correction (α), log₁₀₁ D = log₁₀ a + b log₁₀ ( T - α) and the quadratic, log₁₀ D = log₁₀ a + bT + b ₁ T ² (where a, b, b ₁, and α are constants), each accounted for over 97 % of the variance of D and were good fits to the observed data points for all five species. There was little difference between the predictions obtained from these two equations within the range of observed temperatures. Therefore, the simpler power-law model is preferred. However, there were substantial within-species differences between values of D predicted from extrapolations of the two models from 2 or 3°C down to 0°C. When more data for low temperatures become available it will be possible to make a more objective choice of model.     

Habitat Utilization and Depth Distribution of Small Cryptobenthic Fishes (Blenniidae, Gobiesocidae, Gobiidae, Tripterygiidae) in Ibiza (Western Mediterranean Sea)

The paper describes the habitat utilization of small cryptobenthic fishes of the families Blenniidae (Lipophrys nigriceps, and Parablennius zvonimiri), Gobiesocidae (Apletodon incognitus, Gouania wildenowi, Lepadogaster candollei, and L. lepadogaster), Gobiidae (Chromogobius zebratus, Corcyrogobius liechtensteini, Didogobius splechtnai, Gammogobius steinitzi, Millerigobius macrocephalus, Thorogobius ephippiatus, T. macrolepis, and Zebrus zebrus), and Tripterygiidae (Tripterygion melanurus). Nine different habitats from the waterline to a depth of about 40m were examined. The depth distributions of the single species and co-occurrences with other cryptobenthic fish species are given.     

Seasonal variations in the energy density of fishes in the North Sea

The energy density ( E _D, kJ g^-1 wet mass) of saithe Pollachius virens , haddock Melanogrammus aeglefinus , whiting Merlangius merlangus , Norway pout Trisopterus esmarki , herring Clupea harengus , sprat Sprattus sprattus , sandeel Ammodytes marinus and pearlsides Maurolicus Muelleri , from the North Sea, increased with total length, L _T. However, there was not always a significant ( P> 0·05) linear relationship between L _T and E _D. Seasonal differences in E _D were obvious in mature fish, while geographical differences were insignificant. For all species there was a highly significant correlation ( P< 0·0001) between the percent dry mass of the fish ( D S) and E _D. A general relationship was established for gadoids and sandeel E _D=–3·1492+0·3459 D _S and herring E _D=–4·6395+0·4170 D _S. Thus seasonal and size-specific data on E _D needed for bioenergetics and gastric evacuation models can be determined simply from D _S, which is considerably less costly and time consuming than calorimetry or proximate analysis.     

Phosphorylation and Palmitoylation of the Human D2L Dopamine Receptor in Sf9 Cells

Abstract: We have expressed and biochemically characterized the human D2_long (D2_L) dopamine receptor isoform using the baculovirus/Sf9 cell system. The expressed receptor bound ligands with a pharmacological profile similar to that reported for neuronal and cloned D2_L receptors expressed in mammalian cell lines. Dopamine binding to D2_L receptor was sensitive to guanine nucleotides, indicating receptor coupling to endogenous G proteins. A D2_L receptor-specific antibody identified two major protein species at ∼44 kDa and at ∼93 kDa in immunoblots, suggesting the presence of D2_L receptor monomers and dimers. Both species were purified by immunoprecipitation from digitonin-solubilized preparation of cells expressing D2_L receptor prelabeled with ³²P_i or [³H]-palmitate. These results constitute the first direct evidence for D2_L receptor phosphorylation and palmitoylation.     

Low carbon dioxide concentrations can reverse stomatal closure during water stress

Leaf water potentials below threshold values result in reduced stomatal conductance (g_s). Stomatal closure at low leaf water potentials may serve to protect against cavitation of xylem. Possible control of g_s by leaf water potential or hydraulic conductance was tested by drying the rooting medium in four herbaceous annual species until g_s was reduced and then lowering the [CO₂] to determine whether g_s and transpiration rate could be increased and leaf water potential decreased and whether hydraulic conductance was reduced at the resulting lower leaf water potential. In all species, low [CO₂] could reverse the stomatal closure because of drying despite further reductions in leaf water potential, and the resulting lower leaf water potentials did not result in reductions in hydraulic conductance. The relative sensitivity of g_s to internal [CO₂] in the leaves of dry plants of each species averaged three to four times higher than in leaves of wet plants. Two species in which g_s was reputed to be insensitive to [CO₂] were examined to determine whether high leaf to air water vapor pressure differences (D) resulted in increased stomatal sensitivity to [CO₂]. In both species, stomatal sensitivity to [CO₂] was indeed negligible at low D, but increased with D, and low [CO₂] partly or fully reversed closure caused by high D. In no case did low leaf water potential or low hydraulic conductance during drying of the air or the rooting medium prevent low [CO₂] from increasing g_s and transpiration rate.     

Low temperature effects on ubiquinone content, respiration rates and lipid peroxidation levels of etiolated seedlings of two differentially chilling-sensitive species

Ubiquinone functions primarily in the electron transport chain of the mitochondria of plants and animals. Secondary roles in plant tissue, such as antioxidant activity, have also been proposed. The effect of low temperature exposure on etiolated seedling embryonic axes of two differentially chilling-sensitive species, mung bean ( Vigna radiata L.) (chilling-sensitive) and pea ( Pisum sativum L. cv. Lincoln) (chilling-tolerant) with respect to respiration rate, lipid peroxidation and ubiquinone content was examined. Whole seedlings (embryonic axis and cotyledon) of both species were exposed to control temperatures (20°C) (6 days) or an acclimatory low temperature treatment of 10°C (3 days) followed by exposure at 5°C (3 days). Measurements were initiated 3 days after seedlings had reached 50% germination (D0). Prior to measurements the cotyledons were removed and only the embryonic axis was used in these experiments. Ubiquinol (UQH₂), ubiquinone (UQ) and total ubiquinone (UQ_tot) content decreased in mung bean in response to the temperature treatment and UQH₂ and UQ_tot remained stable in the more chilling-tolerant pea. The reduction of the total Q-pool was approximately 85–92%, suggesting a high degree of saturation of the respiration pathways. Respiration declined and the RQ ratio increased in both species in response to low temperature. Cytochrome c oxidase (COX) (EC 1.9.3.1) activity was higher in pea than in mung bean but decreased during low temperature exposure in both species. Considering that levels of MDA (lipid peroxidation) did not increase in either species in response to chilling, decreased levels of UQH₂ and UQ observed in chilling-sensitive mung bean may indicate that these compounds were damaged prior to other membrane lipids during low temperature treatment and rendered undetectable.     

Temperature and the tropical tortoise Kinixys spekii: tests of thermoregulation

The mean body temperature (T_b) of active Kinixys spekii did not vary with sex or type of activity, or between hot days (maximum ambient temperature T_a > 29°C) and cool days. On hot days, T_b increased rapidly in the morning, and was constant during the late afternoon after midday inactivity. On cool days, T_b increased more slowly in the morning, and decreased during the afternoon. The slopes of T_b on T_a overall, and on hot days, were close to one, suggesting that tortoises were thermoconformers; the slope was greater than one on cool days. In a second test of thermoregulation, T_bs were compared with temperatures of null models (T_m). Tortoises were clearly thermoregulators compared to 'active-all-day' models. 'Activity-time' models had T_m more similar to T_b. Nevertheless, detailed comparison showed that tortoises were thermoregulating in the late morning, and that this was by choice of microenvironment, rather than ceasing activity when T_b reached a high level. These results are discussed in relation to E, a measure of the effectiveness of thermoregulation based on comparison of T_b and T_m with the set point range (T_set) selected in a thermal gradient. A set of three indices, which separate the variability of T_b, the difference between T_b and T_m, and between T_b and T_set, is suggested as a more generally applicable summary of thermoregulation in ectotherms.     

A unified index to measure ecological diversity and species rarity

Several indices have been created to measure diversity, and the most frequently used are the Shannon-Wiener (H) and Simpson (D) indices along with the number of species (S) and evenness (E). Controversies about which index should be used are common in literature. However, a generalized entropy (Tsallis entropy) has the potential to solve part of these problems. Here we explore a family of diversity indices (S_q; where q is the Tsallis index) and evenness (E_q), based on Tsallis entropy that incorporates the most used indices. It approaches S when q=0, H when q→1 and gives D when q=2. In general, varying the value of the Tsallis index (q), S_q varies from emphasis on species richness (q<1) to emphasis on dominance (q>1). Similarly, E_q also works as a tool to investigate diversity. In particular, for a given community, its minimum value represents the maximum deviation from homogeneity (E_q=1) for a particular q (herein named q*). It is remarkable that our analysis indicates that q* and its corresponding evenness, E_q*, are negatively affected by S when using simulated data. They may represent an index related to species rarity. Furthermore, S_q* (i.e. the value of S_q for a specific q*) is positively affected by richness that is an important property of any diversity index. In general, our findings indicate that the indices H, D, S, S_q*, E and E_q* are only part of a whole set of possibilities. In addition, the ecological properties of E_q* and S_q*, proposed here for the first time, show promise in ecology.     

Effects of river flow on larval growth and survival of Japanese seaperch Lateolabrax japonicus (Pisces) in the Chikugo River estuary, upper Ariake Bay

The abundance and growth history of larval and juvenile Japanese seaperch Lateolabrax japonicus were investigated in the Chikugo River estuary, upper Ariake Bay, from 1990 to 2000. Growth during the larval period (up to 15 mm standard length, L _S, the size at recruitment into the estuary) was backcalculated using sagittal otolith microstructures by the biological intercept method. Growth rates in length declined at body sizes >14 mm L _S. High freshwater discharge through the Chikugo River was associated with high temperatures of the upper Ariake Bay where the larvae spend their planktonic life. Mean larval stage duration (days) from hatch to 15 mm ( D ₁₅) varied between 48·8 and 76·2 days and was inversely correlated with the estimated mean temperature history [mean daily temperature (° C) experienced by the larvae during the period from hatch to 15 mm, T ₁₅]. Mean abundance (number m⁻²) of larvae and juveniles was highest in years when T ₁₅, D ₁₅ and freshwater discharge were at intermediate levels. Although the abundance was not correlated with either of these variables, an exponential relationship between abundance and D ₁₅ was found when data collected during the highest river discharge years (1990, 1991 and 1998) were excluded. The increase in freshwater discharge through the Chikugo River probably had the potential to enhance or diminish Japanese seaperch recruitment in two ways: 1) it could increase recruitment probability by increasing temperature and larval growth and 2) high river flow also had the potential to decrease the probability of immigration into the river by increasing larval seaward dispersion, predation due to decreased turbidity and starvation due to decreased zooplankton prey abundance in the estuary.     

GANGLIOSIDES IN DEVELOPING MOUSE BRAIN MYELIN

Abstract— Gangliosides were isolated from myelin prepared from mouse brains of different ages (23 to 490 days). Quantitative estimation of lipid-bound sialic acid levels indicated a gradual increase from 560 μg/g of myelin at 23 days to about 1200 μg/g of myelin at older ages. The major ganglioside in all myelin preparations was the monosialoganglioside G₄ (G_M1). However, considerable amounts of di- and trisialo species also were found in myelin from young animals. In contrast to human myelin in which the monosialoganglioside, sialosylgalactosylceramide (G₇) was highly enriched (L edeen et al. , 1973), a much smaller enrichment of this ganglioside was noticed in mouse brain myelin. Ganglioside G₇ was not detectable in myelin until the animals were 35 days old, and showed a slight increase with increasing age after that. The results strongly indicated that the concentration of G₇ in myelin is species specific and age dependent. The study also demonstrated that the ganglioside accretion in developing mouse brain myelin was attributable to the enrichment of monosialogangliosides G₄ (G_M1), G₅ (G_M2) and G₇ at the expense of polysialogangliosides.     

Drought-induced shifts in daily CO2 uptake patterns for leafy cacti

For cacti with persistent, relatively large leaves, most shoot CO₂ uptake under well-watered conditions occurs by the leaves using the C₃ pathway. For three species in the primitive subfamily Pereskioideae, droughts of 7 or 14 days decreased leaf daytime net CO₂ uptake by an average of 49 and 88%, respectively; these species always had a net CO₂ release at night by the leaves and both at night and during the day by the stems. For three leafy species in subfamily Opuntioideae, 7 and 14 days of drought reduced leaf daytime net CO₂ uptake by 90 and 100%, respectively. Although drought reduced the total CO₂ uptake over 24 h, the average percentage occurring at night by the leaves of these species increased from 5% under wet conditions to 71% after 7 days of drought to 99% after 14 days of drought. For two of the three species of Opuntioideae, 7 days of drought caused the small net CO₂ uptake by the sterns to shift from the daytime to the nighttime, while for the third species drought caused a reduction of its stem nocturnal net CO₂ uptake. Thus, shifts from predominantly daytime to predominantly nighttime net CO₂ uptake can be induced by drought for the leaves and the stems of leafy cacti in subfamily Opuntioideae, indicating a high degree of biochemical versatility.     

Leaf structure and chemical composition as affected by elevated CO2: genotypic responses of two perennial grasses

Genotypic variability was studied in two Mediterranean grass species, Bromus erectus and Dactylis glomerata , with regard to the response to CO₂ of leaf total non-structural carbohydrate concentration ([TNC]_lf), specific leaf area (SLA), and leaf carbon and nitrogen concentrations ([C]_lf and [N]_lf, respectively). Fourteen genotypes of each species were grown together on intact soil monoliths at ambient and elevated CO₂ concentrations (350 and 700 μmol mol⁻¹, respectively). In both species, the most consistent effect of elevated CO₂ was an increase in [TNC]_lf and a decrease in leaf nitrogen concentration when expressed either as total dry mass [N_m]_lf, structural dry mass [N_mst]_lf or leaf area [N_a]_lf. The SLA decreased only in D. glomerata , due to an accumulation of total non-structural carbohydrates and to an increase in leaf density. No genotypic variability was found for any variable in B. erectus , suggesting that genotypes responded in a similar way to elevated CO₂. In D. glomerata , a genotypic variability was found only for [Cst], [N_m]_lf, [N_mst]_lf and [N_a]_lf. Since [N_m]_lf is related to plant growth and is a strong determinant of plant–herbivore interactions, our results suggest evolutionary consequences of elevated CO₂ through competitive interactions or herbivory.     

Decoupling the influence of leaf and root hydraulic conductances on stomatal conductance and its sensitivity to vapour pressure deficit as soil dries in a drained loblolly pine plantation

The study examined the relationships between whole tree hydraulic conductance ( K _tree) and the conductance in roots ( K _root) and leaves ( K _leaf) in loblolly pine trees. In addition, the role of seasonal variations in K _root and K _leaf in mediating stomatal control of transpiration and its response to vapour pressure deficit ( D ) as soil-dried was studied. Compared to trunk and branches, roots and leaves had the highest loss of conductivity and contributed to more than 75% of the total tree hydraulic resistance. Drought altered the partitioning of the resistance between roots and leaves. As soil moisture dropped below 50%, relative extractable water (REW), K _root declined faster than K _leaf. Although K _tree depended on soil moisture, its dynamics was tempered by the elongation of current-year needles that significantly increased K _leaf when REW was below 50%. After accounting for the effect of D on g _s, the seasonal decline in K _tree caused a 35% decrease in g _s and in its sensitivity to D , responses that were mainly driven by K _leaf under high REW and by K _root under low REW. We conclude that not only water stress but also leaf phenology affects the coordination between K _tree and g _s and the acclimation of trees to changing environmental conditions.     

Leaf stomatal responses to vapour pressure deficit under current and CO2-enriched atmosphere explained by the economics of gas exchange

Using the economics of gas exchange, early studies derived an expression of stomatal conductance ( g ) assuming that water cost per unit carbon is constant as the daily loss of water in transpiration ( f _e) is minimized for a given gain in photosynthesis ( f _c). Other studies reached identical results, yet assumed different forms for the underlying functions and defined the daily cost parameter as carbon cost per unit water. We demonstrated that the solution can be recovered when optimization is formulated at time scales commensurate with the response time of g to environmental stimuli. The optimization theory produced three emergent gas exchange responses that are consistent with observed behaviour: (1) the sensitivity of g to vapour pressure deficit ( D ) is similar to that obtained from a previous synthesis of more than 40 species showing g to scale as 1 −  m  log( D ), where m   ∈  [0.5,0.6], (2) the theory is consistent with the onset of an apparent 'feed-forward' mechanism in g , and (3) the emergent non-linear relationship between the ratio of intercellular to atmospheric [CO₂] ( c _i/ c _a) and D agrees with the results available on this response. We extended the theory to diagnosing experimental results on the sensitivity of g to D under varying c _a.     

Shrinkage of flounder Platichthys flesus (L.) and turbot Psetta maxima (L.) following freezing

Freezing of adult flounder Platichthys flesus and turbot Psetta maxima for 24 h resulted in mean decrease of total length ( L _T) of 2·1 and 1·3% and a reduced body mass ( M ) of 3·1 and 1·3%, respectively. Increasing the freezing time to 25 days increased the shrinkage in turbot but not in flounder. The L _T and M _T conversion equations for the different species and time spent frozen are given. The differences between species could be explained by the higher volume to surface area relationship in turbot compared with flounder.     

Genetic Diversity and Population Structure of Dioscorea tokoro Makino, a Dioecious Climber

Abstract Dioscorea tokoro Makino is a herbaceous climber species widespread in East Asia. Genetic structure of a natural population of D. tokoro was examined employing starch gel electrophoresis of allozymes. Genotypes of seven loci were studied for 1,128 individuals. Twenty-six populations located mainly in the Kinki district of Japan were subgrouped into four large clusters by the geographical distribution of alleles. The D. tokoro population was revealed to contain greater total genetic diversity ( H_T =0.282) and higher intrapopulational genetic diversity ( H_S =0.258) than other outcrossing species for which data are available. On the other hand, interpopulational differentiation ( G_ST =0.096) was smaller than in other outcrossers. For the heterozygosity deficiency observed ( F_IT =0.125), population subdivision ( F_ST =0.096) and inbreeding within the population ( F_IS =0.067) were revealed to contribute to the same extent. From these F -statistics, the migration rate among subpopulations and the rate of between-relative matings were estimated. Overall results on the genetic structure of the D. tokoro population indicated a high gene flow among its subpopulations, and this may be the consequence of its life form as a climber and its habitat in a disturbed environment. During the study, the geographical cline of Pgi allele frequencies was observed. This finding was supposed to be the result of the selection imposed on Pgi by the temperature differences between localities.     

Leaf blade structure and C4 acid decarboxylation enzymes in xCynochloris spp. (Poaceae), intergeneric hybrids between species of different C4 type

PRENDERGAST, H. D. V., STONE, N. E. & HATTERSLEY, P. W., 1988. Leaf blade structure and C₄ acid decarboxylation enzymes in x Cynochloris spp. (Poaceae), intergeneric hybrids between species of different C₄ type. x Cynochloris macivorii Clifford and Everist and x C. reynoldensis B. K. Simon (Poaceae) are intergeneric C₄ hybrids between Cynodon dactylon (L.) Pers., and NAD-malic enzyme (NAD-ME) species, and two different PEP carboxykinase (PCK) species of Chloris . Parental species of each hybrid species have the 'classical' leaf blade structure of their respective C₄ acid decarboxylation types. The outline of the photosynthetic carbon reduction (PCR or Kranz) bundle sheath and the position of the PCR cell chloroplasts in x Cynochloris are intermediate between those of the parental species, C. macivorii being more like Cynodon dactylon and x C. reynoldensis more like Chloris spp. The PCR chloroplast shape in x C. macivorii and x C. reynoldensis is like that of Cynodon dactylon and Chloris spp., respectively. Differences between the hybrids in their enzyme activities complement these structural differences: x C. macivorii has more NAD—ME and less PCK activity than x C. reynoldensis , although in both species PCK activity is the greater. Both hybrids, however, have a suberized lamella in PCR cell walls as do Chloris spp. The close taxonomic relationship between Cynodon and Chloris make these genera especially suitable for reciprocal crossing experiments aimed at increasing understanding of the genetic relationships between subtypes of the C₄ photosynthetic pathway.     

Plasticity in maximum stomatal conductance constrained by negative correlation between stomatal size and density: an analysis using Eucalyptus globulus

Maximum stomatal conductance to water vapour and CO₂ ( g _wmax, g _cmax, respectively), which are set at the time of leaf maturity, are determined predominantly by stomatal size ( S ) and density ( D ). In theory, many combinations of S and D yield the same g _wmax and g _cmax, so there is no inherent correlation between S and D , or between S , D and maximum stomatal conductance. However, using basic equations for gas diffusion through stomata of different sizes, we show that a negative correlation between S and D offers several advantages, including plasticity in g _wmax and g _cmax with minimal change in epidermal area allocation to stomata. Examination of the relationship between S and D in Eucalyptus globulus seedlings and coppice shoots growing in the field under high and low rainfall revealed a strong negative relationship between S and D , whereby S decreased with increasing D according to a negative power function. The results provide evidence that plasticity in maximum stomatal conductance may be constrained by a negative S versus D relationship, with higher maximum stomatal conductance characterized by smaller S and higher D , and a tendency to minimize change in epidermal space allocation to stomata as S and D vary.     

Mutagenic lesion bypass and two functionally different RecA proteins in Deinococcus deserti

RecA is essential for extreme radiation tolerance in Deinococcus radiodurans . Interestingly, Sahara bacterium Deinococcus deserti has three recA genes ( recA _C, recA _P1, recA _P3) that code for two different RecA proteins (RecA_C, RecA_P). Moreover, and in contrast to other sequenced Deinococcus species, D. deserti possesses homologues of translesion synthesis (TLS) DNA polymerases, including ImuY and DnaE2. Together with a lexA homologue, imuY and dnaE2 form a gene cluster similar to a widespread RecA/LexA-controlled mutagenesis cassette. After having developed genetic tools, we have constructed mutant strains to characterize these recA and TLS polymerase genes in D. deserti . Both RecA_C and RecA_P are functional and allow D. deserti to survive, and thus repair massive DNA damage, after exposure to high doses of radiation. D. deserti is mutable by UV, which requires ImuY, DnaE2 and RecA_C, but not RecA_P. RecA_C, but not RecA_P, facilitates induced expression of imuY and dnaE2 following UV exposure. We propose that the extra recA _P1 and recA _P3 genes may provide higher levels of RecA protein for efficient error-free repair of DNA damage, without further increasing error-prone lesion bypass by ImuY and DnaE2, whereas limited TLS may contribute to adaptation to harsh conditions by generating genetic variability.