Age and growth of the mesopelagic squid Ancistrocheirus lesueurii (Oegopsida: Ancistrocheiridae) from the central-east Atlantic based on statolith microstructure

Statolith microstructure was studied in 56 Ancistrocheirus lesueurii (25 to 423 mm of mantle length, ML) caught in the central-east Atlantic. Statolith growth increments were grouped into three main growth zones, distinguished mainly by increment width. The second transition in the statolith microstructure (from Zone 2 to Zone 3) coincides with the life history shift from epipelagic and upper mesopelagic to a bathyal habitat. Second-order bands (mean 27.65 growth increments) and sub-bands (mean 13.6 growth increments) within statolith microstructure appeared to be related to the lunar cycle. Striking sexual dimorphism is reflected in the age and growth rates: males live ca. 1 yr, while females only start maturing at this age and obviously live >1.5 yr. A. lesueurii is a slow growing squid, attaining 25 to 30 mm ML at the age of 100 d. After ontogenetic migrations into bathypelagic waters at ML > 30 to 35 mm, growth rates gradually decrease to the minimum known values for squids. Based on back-calculated hatching dates, A. lesueurii hatches throughout the year with a peak between November and March. Received: 28 August 1996 / Accepted: 31 January 1997     

The influence of ration level on growth and statolith increment width of the tropical squid Sepioteuthis lessoniana (Cephalopoda: Loliginidae): an experimental approach

Juvenile squids were grown in individual 2.6-l floating enclosures and were fed either a high- or a low-ration diet of fish and the crustacean Acetes. Squids were maintained for a maximum of 44 days in two experiments. The high-ration individuals reached a significantly larger size in both experiments (27, 25.5 mm mean mantle length, ML) compared to their low-ration siblings (19 mm mean ML) in both experiments. The statolith increment widths prior to the start of the experiment were significantly wider (between 3 and 4 μm) compared to the increment widths after the start of the experiment (between 2 and 3 μm) both for the low- and the high-ration squids. High-ration squids also had significantly wider increments and larger statoliths than their low-ration siblings. Even though we detected consistent trends in daily statolith increment widths for the different feeding regimes, we could not detect variation in increment widths at a daily level of resolution (i.e. as a result of differences in day-to-day food intake at an individual level). This was probably due to the relatively consistent diet experienced by each individual. These experiments revealed that ration level influences squid growth rate, statolith size and daily statolith increment width. Received: 30 March 2000 / Accepted: 30 October 2000     

Determination of the entrainment coefficient of a pure plume using the salt-bath technique

Environmental Fluid Mechanics - The entrainment coefficient of the pure plume, the ratio of the radial velocity of the entraining fluid at the edge of the plume to the axial velocity, is...     

Determination of living and active bacterioplankton: a comparison of methods

The purpose of this study was the quantification, through the comparison of different methods, of viable and metabolically active bacteria in marine environments. To quantify the living and active bacterioplankton fractions, we compared the total cell count (TC using DAPI staining), plate count on marine agar (CFU), and three viability-staining methods: nucleoid-containing cell count (NuCC), Live/Dead staining procedure (L/D) and direct viable count (DVC). With respect to TC (mean value 3.0 ± 2.3 × 10⁵ cell ml^-1) CFU represented less than 0.1% and DVC cells 1%, both showing significant differences. NuCC and L/D cells were 18.0% and 15.9% of TC, respectively, showing no significant differences and higher percentages in the Ionian Sea than the Adriatic Sea. Moreover, NuCC and L/D were two orders of magnitude greater than the culturable fraction, while active cells (DVC) exceeded CFU by one order of magnitude. The comparison of different staining methods allowed us to confirm the simultaneous presence of different physiological states within the bacterial population in natural marine environments. The NuCC and L/D methods gave comparable values to those of other authors, while the DVC procedure gave lower values than previously reported. This research provides information on the fraction of living and/or metabolically active bacteria in aquatic ecosystems. Since each method has its own detection limits, the study highlights the need to simultaneously compare the different methods to validate their results.     

Impact of temperature on juvenile growth and age at first egg-laying of the Pacific reef squid Sepioteuthis lessoniana reared in captivity

Cephalopod mollusks exhibit highly plastic life cycle traits influenced primarily by the interactive effects of food availability, light cycle and temperature, with the latter perhaps the most influential. Hatchlings of the tropical reef squid Sepioteuthis lessoniana were hatched from field-collected eggs in the laboratory and cultured at different temperatures to evaluate the effect of temperature on growth rates. All groups showed rapid, sustained growth rates from hatching to a size of 10–25 g. Beyond this size range, growth was slower and not clearly exponential in form. Growth rate was closely linked to temperature. Squids grown at approximately 27 °C attained a size of 10 g in as little as 45 days at sustained growth rates of 12.2% body weight day⁻¹ (%bw day⁻¹), while squids cultured at 20 °C required almost 100 days to attain the same size at rates of 5.7%bw day⁻¹. At an age of 55 days and approximately 1 g body weight, juvenile squids cultured at 20 °C were able to accelerate growth rates from 5.7%bw day⁻¹ to over 12%bw day⁻¹ when temperature was raised to 27 °C. They maintained this growth rate to a size of about 10 g and an age of at least 75 days post-hatching, indicating that body size and not age is the limiting factor for this rapid post-hatching growth. By comparison, conspecifics cultured near 27 °C from hatching had shifted out of the rapid post-hatching growth phase by day 50 at sizes between 10 and 50 g. The hatchlings from temperate to subtropical Japan had consistently higher growth rates at comparable temperatures than hatchlings from tropical Okinawa. When plotted as growth rate versus temperature, the Japanese group had a clearly higher slope to the relationship than the tropical populations, equivalent to a 2%bw day⁻¹ difference in growth rate at 25 °C. Age at first egg-laying was decreased at higher culture temperatures; however, overall life span was not. Received: 21 February 2000 / Accepted: 6 September 2000     

Decolourization of pulp and paper mill effluents using heat-treated coal: a comparison with activated charcoal

A comparison between activated charcoal and heat-treated coal for decolourization of pulp and paper mill waste water was studied. The heat-treated coal was prepared in an inert atmosphere at 800°C. The adsorption dynamics that include batch contact–time study, kinetics along with adsorption isotherms were carried out. The study shows that heat-treated coal is a suitable adsorbent and can be used for the decolourization of pulp and paper mill effluent streams. The maximum removal was achieved at the initial stages of contact, and the overall adsorption was a slow process. However, the equilibrium concentration in the case of both the adsorbents reaches at almost same time. The linear plot of the Lagergren model shows its applicability and first-order kinetics.     

Approaching the upper boundary of driver-response relationships: identifying factors using a novel framework integrating quantile regression with interpretable machine learning

● A novel framework integrating quantile regression with machine learning is proposed. ● It aims to identify factors driving observations to upper boundary of relationship. ● Increasing N:P and TN concentration help fulfill the effect of TP on CHL. ● Wetter and warmer decrease potential and increase eutrophication control difficulty. ● The framework advances applications of quantile regression and machine learning. The identification of factors that may be forcing ecological observations to approach the upper boundary provides insight into potential mechanisms affecting driver-response relationships, and can help inform ecosystem management, but has rarely been explored. In this study, we propose a novel framework integrating quantile regression with interpretable machine learning. In the first stage of the framework, we estimate the upper boundary of a driver-response relationship using quantile regression. Next, we calculate “potentials” of the response variable depending on the driver, which are defined as vertical distances from the estimated upper boundary of the relationship to observations in the driver-response variable scatter plot. Finally, we identify key factors impacting the potential using a machine learning model. We illustrate the necessary steps to implement the framework using the total phosphorus (TP)-Chlorophyll a (CHL) relationship in lakes across the continental US. We found that the nitrogen to phosphorus ratio (N׃P), annual average precipitation, total nitrogen (TN), and summer average air temperature were key factors impacting the potential of CHL depending on TP. We further revealed important implications of our findings for lake eutrophication management. The important role of N׃P and TN on the potential highlights the co-limitation of phosphorus and nitrogen and indicates the need for dual nutrient criteria. Future wetter and/or warmer climate scenarios can decrease the potential which may reduce the efficacy of lake eutrophication management. The novel framework advances the application of quantile regression to identify factors driving observations to approach the upper boundary of driver-response relationships.     

Microphytobenthos of the Dogger Bank: a comparison between shallow and deep areas using phytopigment composition of the sediment

The surface sediment characteristics related to benthic microalgae primary production were studied at the Dogger Bank, North Sea, in order to evaluate the potential role of microphytobenthos as a food source for the macrobenthic fauna. Twenty-one stations were sampled in July 2001 and May 2002, with water depth ranging from 16.3 to 68.5 m. High-performance liquid chromatography pigment analyses revealed that concentrations of chlorophyll a, chlorophyll c and fucoxanthin are mainly associated with benthic diatom flora at most parts of the Dogger Bank. High percentage of phytopigments (>50%) was firmly attached to sand grains at the stations shallower than 40 m water depth. The deeper stations were characterized by a phytopigment composition originating from pelagic phytoplankton settled on the sea floor. Qualitative microscopy showed that the benthic microflora on top of the Bank mainly consists of small diatoms (5–10 μm), such as e.g., Diploneis spp., living attached to the sand grains. The results are discussed concerning possible implications for ecology and biogeochemistry of the Dogger Bank area.     

Habitat and age of the giant squid (<Emphasis Type="Italic">Architeuthis sanctipauli</Emphasis>) inferred from isotopic analyses

The age and habitat of the giant squid, Architeuthis sanctipauli Velain, 1877, were determined based on isotopic analyses of the statoliths of three female specimens captured off Tasmania, Australia, between January and March 1996. Assuming that the aragonite of the statoliths formed in equilibrium with seawater, ¹⁸O analyses indicated that the squid lived at temperatures of 10.5–12.9°C, corresponding to average depths of 125–250 m and maximum depths of 500 m. The capture records indicated that these squid may have occasionally ranged still deeper, to as much as 1000 m. All the statoliths were labeled with bomb ¹⁴C (¹⁴C=+22.9 to +44.6), consistent with the depths inferred from ¹⁸O. A thin section through one of the statoliths revealed 351 growth increments grouped into check-ring structures every 10–16 increments. A model for statolith growth and the pattern of temporal change in ¹⁴C in the water column was used to estimate the ages of the three specimens. These estimates were very sensitive to the choice of depth range over which ¹⁴C values were integrated. Assuming that the capture depths represented the maximum habitat depths of these individuals, the calculations suggested an age of 14 years or less. More refined age estimates require a better understanding of the variation of ¹⁴C and temperature with depth in the areas in which the squids live.Communicated by J.P. Grassle, New Brunswick     

Comparative study between using natural and synthetic zeolites for the improvement of soil salinity and crop yield

The effects of natural zeolite (clinoptilolite, NZ) and synthetic zeolite (Y, SZ) on salinity and the presence of the harmful salts in the soil were compared on Raphanus sativus L. Nine soil treatments were studied: 1 (control), 2 (NaCl), 3 (Na₂SO₄), 4 (NZ), 5 (SZ), 6 (NZ?+?NaCl), 7 (SZ?+?NaCl), 8 (NZ?+?Na₂SO₄), and 9 (SZ?+?Na₂SO₄). Five radish seeds were planted in each pot. Each treatment was repeated 10 times. After 50 days under equal conditions some parameters consisting of the number of leaves (NL), total leaf area (TLA), total fresh weight (TFW), total dry weight (TDW), root fresh weight (RFW), air fresh weight (AFW), root dry weight (RDW) and air dry weight (ADW) were determined. Results showed that adding either NZ or SZ to salinic soil (treatments NZNaCl, NZNa₂SO₄, SZNaCl and SZNa₂SO₄) increased AFW, TFW and TDW. Using both NZ and SZ in normal soil increased the weight of plants by developing AFW. Further NZ was more effective on soil with NaCl than SZ.     

Determination of ammonium uptake and regeneration rates using the seawater dilution method

We have developed a method for the determination of ammonium uptake and regeneration rates applying the principle of the seawater dilution technique. The method is based on the separation of uptake and regeneration processes in the dilution series. A model is used to estimate ammonium uptake and regeneration rates simultaneously, in addition to phytoplankton growth and grazing rates. The method was applied to dilution experiments conducted during a two-year study of the upwelling region off Oregon, USA. Ammonium uptake and regeneration rates determined with our method ranged from 0.5 to 3 mol l^-1d^-1 and from 0.2 to 2.9 mol l^-1d^-1, respectively. These values agree well with those from other studies applying ¹⁵N tracer techniques in the same or similar environments. We found a close coupling between ammonium uptake and regeneration, and a strong relationship between ammonium regeneration and grazing rates. In addition, the nutritional status of the phytoplankton community could be assessed by comparing instantaneous ammonium uptake rates with the specific phytoplankton growth rates. Using the dilution technique to determine ammonium uptake and regeneration rates of the plankton community is a promising alternative to the application of tracer techniques conventionally used to determine these rates.     

Does song reflect age and viability? A comparison between two populations of the great reed warbler Acrocephalus arundinaceus

Song complexity is often regarded as a sexually selected trait that reflects the overall quality of a male. In many passerine species, old males possess larger song repertoires than younger males. This may be either because individual males improve their performance as they get older (longitudinal increase) or because poor singers have reduced viability and, hence, are underrepresented in old age classes (cross-sectional increase). We studied the age dependence of repertoire size and other song traits in a German and a Swedish great reed warbler (Acrocephalus arundinaceus) population. We found marked differences between longitudinal and cross-sectional approaches, as well as between the two study populations. In the German population, we found that syllable switching, a measure of immediate versatility and strophe length, increased with age in a cross-sectional analysis. This was not because birds improved with age (longitudinally) but because syllable switching was positively correlated with male longevity. However, in Sweden, syllable switching seemed to be unrelated to age and longevity. In the Swedish population, individual males increased their repertoire size as they got older (longitudinal increase), but this did not happen in the German population. Hence, two populations, even when belonging to the same subspecies, may differ in whether or not they show delayed song maturation.     

Brood defense and age of young: a test of the vulnerability hypothesis

Summary In many altricial species including the great tit (Parus major) the intensity of brood defense against predators has been shown to increase with the age of the offspring. This effect has been ascribed amongst others to the young becoming more vulnerable as they age (vulnerability hypothesis). In a great tit population suffering heavy losses from brood depredation by the great spotted woodpecker (Dendrocopus major), we rendered first and second broods more vulnerable by artificially enlarging the entrance of the nest hole. Contrary to the vulnerability hypothesis, 16 experimental pairs defended their brood against a dummy great spotted woodpecker less vigorously than did 16 control pairs. Nest concealment behavior potentially compromising active defense was minimized by simultaneous playback of nestling distress calls, thus simulating the act of nest predation. This leaves the brood value hypothesis as an alternative functional explanation of the defense level — age effect. It predicts that parents should defend their brood in proportion to the reproductive value (or some more suitable cohortal equivalent measure) of their offspring. At present, this explanation pertains to one predator species. In first broods, but not in second broods, males defended them more vigorously than did their females. While this parallels previous experiments on brood defense against predators posing a much greater risk to the parents, two functional explanations previously put forward can hardly apply.     

Contrasting C and N isotope ratios from sperm whale skin and squid between the Gulf of Mexico and Gulf of California: effect of habitat

To investigate feeding variation between populations of an apex oceanic predator, stable isotope ratios of carbon (δ¹³C) and nitrogen (δ¹⁵N) have been compared in skin of female and immature male sperm whales (Physeter macrocephalus) from the northern Gulf of Mexico (GoM) and the Gulf of California (GC). Whale sexes were determined genetically. The δ¹³C and δ¹⁵N values from squid muscle were used from the GC, and from inshore and offshore sites in the GoM. We documented contrastingly lower δ¹³C and δ¹⁵N from whales and squid of the GoM compared with those from the GC. While this difference may be associated with variation in trophic position, geographic variation in biochemical cycling influenced significantly the contrasting isotope values between gulfs. Within the northern GoM, the highly distinct δ¹⁵N values of neritic squid versus mesopelagic squid provide further evidence of habitat specificity in δ¹⁵N.     

Variations in the biochemical composition of the diatom Coscinodiscus eccentricus with culture age and salinity

Cultures of the marine diatom Coscinodiscus eccentricus Ehrenberg were grown at four salinities, namely 20, 25, 30 and 35%. The changes in the carbohydrate, protein, silicon and pigment concentrations of the cells were studied throughout the growth cycles in these salinities. The carbohydrate content, expressed as a percentage of the cell dry weight, increased in all cultures during the lag and early log phases. It later fell, sharply at first, as it was used up faster than it was produced. It was not stored during the stationary phase. The protein percentage composition built up to a peak at different stages during the exponential or stationary growth stages, depending on the salinity, but was later respired. The silicon percentage of the dry weight usually decreased during the log phase, as the cells were dividing before becoming fully silicified, and remained low in the stationary phase due to an increase in the volume of the cells. The changes in the frustular thickness were also calculated. The values ranged from 0.24 to 0.35 μm (at the beginning and end of the experiments) to 0.15 μm during the log growth phase. The pigment content was always low. The lipid composition of the cells was calculated by difference. It was usually low during the exponential growth phase, but was accumulated during the stationary phase. The point at which this accumulation began was associated with the time when protein respiration started.     

Age and growth of the naticid gastropod <Emphasis Type="Italic">Polinices pulchellus</Emphasis> (Gastropoda: Naticidae) based on length frequency analysis and statolith growth rings

In Red Wharf Bay, UK the naticid gastropod, Polinices pulchellus, was more abundant and more highly aggregated during the summer months (June–August 2001) than during the winter (December 2000). Whilst small numbers of juvenile P. pulchellus (4–6 mm shell length) were present throughout the year the population consisted mainly of individuals of 12–14 mm shell length. Juvenile snails grew rapidly in size during the winter and early spring; growth then virtually ceased between May and June, following which there was a further period of rapid growth between August and February. Densities ranged between 57 and 4,073 ha⁻¹ and the largest individual collected during this investigation measured 16.2 mm in shell length. Statoliths from adult P. pulchellus revealed the presence of a settlement ring and two prominent growth rings (rings 1 and 2). A curvilinear relationship exists between statolith diameter and shell length in snails up to 16 mm in length. Settlement rings ranged in diameter from 19.7 to 45.2 μm (mean 29.8 μm; SE=0.41) giving an estimated shell length of the settled juvenile of 1.1 mm. The diameter of ring 1 and ring 2 were significantly correlated indicating that rapid growth during the first year is maintained during year 2. Shell lengths estimated from the diameters of the prominent statolith rings and those obtained from length frequency data analysis (LFDA), were broadly congruent strongly suggesting an annual periodicity to the statolith rings. The largest snails (>15 mm) present within this population were estimated to be between 2 and 3 years old. Von Bertallanfy seasonal growth curves obtained from the LFDA predicted values of L∞, K and t ₀ of 14.32 mm, 1.54 and −0.14 years, respectively, suggesting that P. pulchellus rapidly attains its maximum asymptotic size.     

微波辅助萃取-气相色谱法检测裙带菜中的多氯联苯和有机氯农药残留

建立微波辅助萃取-气相色谱法同时检测裙带菜中多氯联苯和有机氯农药残留的方法.裙带菜风干、粉碎后,采用微波辅助萃取仪提取粗提液,经净化、脱酸、脱水、浓缩后,用气相色谱-电子捕获检测器进行分析检测.结果表明,本方法多氯联苯和有机氯农药的检出限分别在0.008—0.044 ng.g-1和0.029—0.273 ng.g-1之间,各组分线性相关系数均大于0.996,加标回收率为72%—131%,相对标准偏差在2%—16%之间(n=3).因此,本方法具有节省时间、减少污染、操作简单便捷等特点,可用于裙带菜等海洋藻类中多氯联苯和有机氯农药残留量的检测.     

Female choice in sage grouse: the roles of attraction and active comparison

Previous studies of female choice in sage grouse Centrocercus urophasianus have implicated both the acoustic quality and repetition rate of the stereotyped strut display as putative cues for female choice. Stages in the choice process at which specific components of male courtship display influence female decisions were investigated using field observations of female pre-mating behavior. Females visited a subset of territorial males and then actively chose one of these as a mate. The order in which males were visited suggested that females searched until an acceptable mate was found, rather than employing a “best-of-n” tactic. Numbers of females visiting a male were related to differences in an acoustical component of display (inter-pop interval) whereas the probability that a visiting female mated was related to display rate (Table 3), indicating that initial attraction and active choice are influenced by different components of display. In addition, inter-pop interval and display rate tended to covary inversely (Fig. 1), suggesting that attraction and active choice may impose conflicting selection pressures on display performance. Received: 11 November 1995/Accepted after revision: 16 March 1996     

Purification and characterisation of octopine dehydrogenase from the marine nemertean Cerebratulus lacteus (Anopla: Heteronemerta): comparison with scallop octopine dehydrogenase

Octopine dehydrogenase from the nemertean Cerebratulus lacteus was purified over 1000-fold to almost homogeneity. The enzyme does not bind to arginine Sepharose 4B. It has a monomeric structure with a relative molecular mass of 40000. Two isoenzymes were identified with isoelectric points of 5.6 and 5.4, whereas the purified isoenzymes of Pecten jacobaeus adductor mucles (which bind to arginine Sepharose 4B) had lower IEP's of 4.9 and 4.7. Apparent K_m's of the nemertean ODH for arginine and pyruvate are dependent on the respective co-substrate concentration. This phenomenon may result in activation of ODH and, thus, production of octopine in locomotory highly active individuals while attacking food, especially when this takes place in a hypoxic habitat, such as decaying mud near the high-water mark. The apparent K_m's for octopine (0.22 mM) and NAD⁺ (14 M) are low. Octopine is a substrate inhibitor for the reverse reaction above 2 mM, and a product inhibitor of the forward reaction by 50% at 1.2 mM. Therefore, only small amounts of octopine are likely to accumulate in vivo. Amino acid substrate specificity is limited to guanidino amino acids. We believe that the amino acid substrate specificity is not an evolutionary modification, but rather that it is narrowed to guanidino amino acids (or even specificity to arginine) in those species where ODH has a physiological function in maintaining redox balance during exercise. The specificity for keto acids is dependent on chain length, (-ketobutyrate>-ketocapronate); a second carboxyl group inactivates the enzyme.     

Paternal age and offspring growth: separating the intrinsic quality of young from rearing effects

Younger individuals are often less successful in reproduction than older ones. This might be because of improving breeding skills with age or because the genetic quality of young or early maternal effects on them vary with parental age. However, no attempt has been made to experimentally separate these processes in vertebrates. We conducted a cross-fostering experiment in collared flycatchers (Ficedula albicollis) in three breeding seasons to disentangle origin- and rearing-related effects of paternal age on chick growth, while controlling for date-specific environmental conditions as well as differences in clutch and brood size. The age of the male at the nest of origin, but not that of the rearing male, had a year-dependent effect on nestling body mass and tarsus length. In two seasons, young of subadult males grew slower in the early linear phase of growth than young of adult males. There was no compensatory growth in the final asymptotic phase, so both body mass and tarsus length before fledging reflected the differential early development. In the remaining year, the age of the male at the nest of origin had no significant effect on chick growth. The environment-dependent origin effect we detected was unexplained by incubation times, hatching asynchrony, chick masses at swapping or previously described age-dependent egg quality patterns. Our results therefore suggest a genotype × environment interaction on the relative development of offspring sired by subadult and adult males. Our results also raise the possibility that female birds may gain genetic benefits by mating with older males. Further studies should identify general patterns of male age-dependent female mate choice and offspring quality in different environmental conditions.