The peculiarities of larval development of the European smelt Osmerus eperlanus eperlanus (L.)

The larval development of the European smelt Osmerus eperlanus eperlanus from hatching to full resorption of the vitelline sac has been described. On the basis of the morphological and dimensioning characteristics, three stages almost equal in the duration have been distinguished during present period. The duration of the larval stages was measured in relative units τ_s. Two palingeneses were discovered during larval development of the smelt: (1) the presence of the ciliary epithelium in the intestine and (2) plasmatic circulation of the blood without blood cell formation. These features are evidence of the antiquity of the origin of smelt and place them at the base of the suborder Salmonoidei.     

Temperature effects on egg and larval development rate in European smelt,Osmerus eperlanus,experiments and a 50 year hindcast

This study investigates the effect of water temperature on the development rate of eggs and larvae, the duration of the endogenous feeding period and its consequences for recruitment of smelt (Osmerus eperlanus) in Dutch lakes IJsselmeer and Markermeer. This study measured temperature-dependent egg and larval development rates as well as mortality rates from fertilization till the moment of absorption of the yolk-sac and from yolk-sac depletion onwards in temperature-controlled indoor experiments. Using multinomial modelling the authors found significant differences in development time of egg development stages under different temperature regimes. Based on historic water temperatures, the model predicted that the larval endogenous feeding period has advanced at a rate of about 2.9 days per decade in a more than 50 year period since 1961, yet there was no change in the duration of the endogenous feeding period. As zooplankton is more responsive to daylight than water temperature cues, a mismatch between the peak of the onset of exogenous feeding of smelt and the peak of zooplankton blooms could lead to high mortality and therefore low recruitment of smelt. Such a mismatch might contribute to a decline in the smelt population in Lake IJsselmeer and Lake Markermeer.     

The year cycle of Eudiaptomus vulgaris (Schmeil, 1896) (Copepoda,Calanoida) in a small,acid water body during 1973. Development in the natural habitat and relationships between temperature and duration of development stages

The development of a population of Eudiaptomus vulgaris (Schmeil, 1896) in the Meeuwenven, a shallow acid guanotrofic moorland pool, has been described during one year. The population hibernates as copepodite 5 stages, adults and, to a small extent as naupliar stages N1, N2 and N3 (which could not develop further at low temperatures in autumn). In spring the population development starts at temperatures above 10°C and shows 3 or 4 pulses a year. An attempt has been made to explain seasonal changes in the size of adult males and females and in the sex ratio.In order to establish the duration of the various development stages, the animals have been cultured at different temperatures under illumination with 2000 Lux at a daylength of 14 hours. An adequate quantity of food from the natural habitat was available.Total egg development and total naupliar and copepodite development have been compared with the results of other workers, especially with those from Eckstein (1964), who studied Eudiaptomus vulgaris in the deep Schluchsee. The duration curves do not differ markedly with those of Eckstein and are strongly temperature dependent.The relation between the development times of the various stages with temperature can be generally expressed as parabolic regressions of the type D = a + b₁T + b₂T², the C₅ and adult stages being the only exception at higher temperatures. Comparison of the relative duration of the stages at different temperatures did show that younger stages can take a larger share of the total development time at lower temperatures, stage N6 being the most temperature-sensitive.     

Preferences of AAA/AAG codon recognition by modified nucleosides, τm5s2U34 and t6A37 present in tRNALys

Deficiency of 5-taurinomethyl-2-thiouridine, τm⁵s²U at the 34th ‘wobble’ position in tRNA^Lys causes MERRF (Myoclonic Epilepsy with Ragged Red Fibers), a neuromuscular disease. This modified nucleoside of mt tRNA^Lys, recognizes AAA/AAG codons during protein biosynthesis process. Its preference to identify cognate codons has not been studied at the atomic level. Hence, multiple MD simulations of various molecular models of anticodon stem loop (ASL) of mt tRNA^Lys in presence and absence of τm⁵s²U₃₄ and N⁶-threonylcarbamoyl adenosine (t⁶A₃₇) along with AAA and AAG codons have been accomplished. Additional four MD simulations of multiple ASL mt tRNA^Lys models in the context of ribosomal A-site residues have also been performed to investigate the role of A-site in recognition of AAA/AAG codons. MD simulation results show that, ASL models in presence of τm⁵s²U₃₄ and t⁶A₃₇ with codons AAA/AAG are more stable than the ASL lacking these modified bases. MD trajectories suggest that τm⁵s²U recognizes the codons initially by ‘wobble’ hydrogen bonding interactions, and then tRNA^Lys might leave the explicit codon by a novel ‘single’ hydrogen bonding interaction in order to run the protein biosynthesis process smoothly. We propose this model as the ‘Foot-Step Model’ for codon recognition, in which the single hydrogen bond plays a crucial role. MD simulation results suggest that, tRNA^Lys with τm⁵s²U and t⁶A recognizes AAA codon more preferably than AAG. Thus, these results reveal the consequences of τm⁵s²U and t⁶A in recognition of AAA/AAG codons in mitochondrial disease, MERRF.     

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.     

The threshold of perception of angular acceleration as a function of duration

The threshold for rotation about the yaw axis was determined for constant acceleration stimuli as a function of their duration in the range from 3 to 25 s. From the torsion-swing model the following theoretical equation can be derived: 1 $$a_{{\text{thr}}} = {C \mathord{\left/ {\vphantom {C {\left[ {1 - \exp \left( { - {{t_s } \mathord{\left/ {\vphantom {{t_s } {\tau _1 }}} \right. \kern-\nulldelimiterspace} {\tau _1 }}} \right)} \right]}}} \right. \kern-\nulldelimiterspace} {\left[ {1 - \exp \left( { - {{t_s } \mathord{\left/ {\vphantom {{t_s } {\tau _1 }}} \right. \kern-\nulldelimiterspace} {\tau _1 }}} \right)} \right]}}$$ , where a _thr=acceleration amplitude at threshold, t _s =duration of the acceleration, τ₁=time constant, C=threshold for very long stimuli. According to this formula the Mulder product (i.e. the product of the threshold acceleration amplitude and the duration of the stimulus) is constant for durations up to 0.3 τ₁. The best fit of this theoretical function to the somatosensory data is found for τ₁=14.5 s, and C=0.22⁰/s ². The time within the Mulder product is constant (about 5s) is doubtless due to the mechanics of the semicircular canals. For the oculogyral data a lower value of τ₁ is found. We do not have any explanation for this lower value.     

The rate of development in poikilothermic animals calculated in astronomical and relative time units

• 1.1.|The problem of comparing the rate of development of various species of poikilothermic animals, using the astronomical time units and relative units of development duration (in the unit of τ₀ — the duration of one mitotic cycle in the period of synchronous cleavage divisions) is considered, a number of fish and amphibian species is taken by example.
• 2.2.|A dimensionless criterion of the relative rate of development (CRR) is proposed. In closely related animal species and genera in the early development CCR = 1, and only later on do some species begin to develop faster than the others, as it takes them less time (measured in a lesser number of τ₀) to pass the identical developmental periods (τ_n).
• 3.3.|In more distant animal groups the same name but not identical developmental periods have different relative duration from the early stages of development, due to gastrulation beginning at different stages of the blastulation, i.e. as a result of heterochronies.

     

Plasticity of the thermal requirements of exotherms and adaptation to environmental conditions

In exothermal organisms, temperature is an important determinant of the rate of ecophysiological processes, which monotonically increase between the minimum (t_{d min}) and maximum (t_{d max}) temperatures typical for each species. In insects, t_{d min} and t_{d max} are correlated and there is a approximately 20°C interval (thermal window W_T = t_{d max} − t_{d min}) between them over which insects can develop. We assumed that other exotherms have similar thermal windows because the thermal kinetics of their physiological processes are similar. In this study, we determined the thermal requirements for germination in plants. Seeds of 125 species of Central European wild herbaceous and crop plants were germinated at nine constant temperatures between 5 and 37°C, and the time to germination of 50% of the seeds D and rate of germination R (=1/D) were determined for each temperature and the Lactin model used to determine t_{d min}, t_{d max}, and W_T. The average width of the thermal windows for seeds was significantly wider (mean 24°C, 95% CI 22.7–24.2°C), varied more (between 14.5 and 37.5°C) and development occurred at lower temperatures than recorded for insects. The limiting temperatures for germination, t_{d min} and t_{d max}, were not coupled, so the width of the thermal window increased with both a decrease in t_{d min} and/or increase in t_{d max}. Variation in W_T was not associated with taxonomic affiliation, adult longevity, or domestication of the different species, but tends to vary with seed size. Plants are poor at regulating their temperature and cannot move to a more suitable location and as a consequence have to cope with wider ranges in temperatures than insects and possibly do this by having wider thermal windows. Synthesis: The study indicated specificity of W_T in different exotherm taxa and/or their development stages.     

Effects of temperature on development,survival, longevity,and fecundity of Serangium japonicum (Coleoptera: Coccinellidae), a predator of Bemisia tabaci Gennadius (Homoptera: Aleyrodidae)

In this study, we evaluated the effect of temperature on the development and reproductive biology of Serangium japonicum (Coleoptera: Coccinellidae) at seven constant temperature regimes (17, 20, 23, 26, 29, 32 and 35°C) for its effect as a predator of Bemisia tabaci (Homoptera: Aleyrodidae). Results indicated that the duration of the egg, larval and pupal stages were significantly affected by temperature. The developmental time gradually declined with the increase of temperature from 17 to 29°C, however an extension in the developmental periods was observed in the temperature range of 32 to 35°C. The survival rates of different insect stages were stable at temperatures between 20 and 32°C; however at extreme temperatures of 35°C, a sharp decrease was evident. The highest fecundity of the female (387.2 eggs per female) was recorded at 20°C. Based on these results, life tables of S. japonicum were constructed for temperatures in the range 20–35°C. The maximum reproductive rate (R ₀=279.9) occurred at 26°C. The maximum values for innate capacity for increase (r _m=0.1131) and the finite rate of increase (λ=1.1197) occurred at 29°C. The mean generation time (T) decreased with increased temperature, the longest of which was 76.0 days (at 20°C) and the shortest was 36.6 days (at 32°C). These results offer valuable insight on the importation and establishment of S. japonicum into new environments with diverse temperature regimes.     

European smelt Osmerus eperlanus in the eastern Gulf of Finland,Baltic Sea: Stock status and fishery

In the eastern Gulf of Finland, European smelt Osmerus eperlanus occurs as an anadromous ecological form that spawns in coastal, low-salinity zones and in several rivers entering the gulf, most importantly in the River Neva. Osmerus eperlanus is a key commercial fish species for the population of St. Petersburg, and the city's fish symbol. However, the state of the smelt stock has considerably deteriorated over the past few decades. Monitoring shows that annual catches during 1965–1992 averaged 2274 t, compared to 292 t in 2002–2017, although some improvement is inidicated by a gradual increase in catches in recent years (e.g., to 595 t in 2017). This paper addresses long-term and recent changes in the fisheries for smelt in the eastern Gulf of Finland, including both commercial and recreational fisheries, and the range of fishing gears used. The commercial smelt fishery is mainly conducted during the spawning period (April–May) on migrating fish, using trap nets of various designs and beach seines. There has been an increase in recreational fisheries for smelt; in years when ice cover on the gulf during winter (December–April) is steady, recreational fishers from St. Petersburg, using hook and line, may catch quantities that are comparable to those of commercial catches. Several factors may account for the stock dynamics and associated changes in catches of smelt: these include a decrease in prey availability in the gulf; loss and degradation of spawning and nursery habitats, partly associated with large-scale hydroengineering operations in Neva Bay; and illegal, unreported and unregulated (IUU) fishing which became widespread in post-Soviet decades. In spite of a gradual increase in smelt abundance in the most recent 15 years, a failure to accurately monitor and manage the extent of IUU and recreational fishing for smelt, to assess the status of the stock, or to forecast catches, increases the risk of overfishing of the spawning stock.     

Embryonal effects of <Emphasis Type="Italic">t</Emphasis>-haplotypes in mice

The effects of t-haplotypes on embryonic morphology in house mouse Mus musculus were described. Lethal mutations, t-haplotypes, in homozygotes induce abnormal embryogenesis and zygotic death at different developmental stages, which depends on the time of their action in ontogeny. Death commonly occurs in the first semester of pregnancy from the morula to the mature embryo stage (day 9–10), and the embryogenetic abnormalities and their timing were Specific for each t-haplotype. Such mutations were analyzed to identify the gene products (proteins) affecting the nervous system development. The t-complex proved to contain tandem repeats coding for regulatory factors modulating the expression of specific structural genes in mouse neurons.     

In vivo temperature-dependent development of Beauveria bassiana (Deuteromycotina: Hyphomycetes) mycosis of the European corn borer,Ostrinia nubilalis (Lepidoptera: Pyralidae)

The in vivo incubation period of Beauveria bassiana mycosis of the European corn borer, Ostrinia nubilalis, was found to vary in response to temperature of incubation, level of initial exposure (dose), and the age of the host larvae. Incubation temperature was found to be the dominant factor affecting disease development within each of the host instars examined, while dose produced significant effects only in the early instars. A nonlinear regression model was used to construct three-dimensional stimulus-response surfaces for each host instar. This model has provided reasonable predictions of the disease incubation period when used within the temperature regimes found throughout New York State.     

Embryonic development of the pacific cod <Emphasis Type="Italic">Gadus macrocephalus</Emphasis> (Gadidae)

Incubation of pacific cod eggs was divided into eight series, in which temperatures were set at −0.04°C to +4.03°C and warm and cold conditions alternated. The morphological changes that took place during the embryogenesis were described in detail using the results of the incubation. Twenty-two morphological characters that could be identified easily and that characterized the morphogenesis were defined in the course of development. The results of the incubation and data from the literature showed that the duration of the embryonic period in the Pacific cod’s lifecycle grew exponentially as water temperature decreased. It was found during the experiment that developing cod eggs survived low water temperatures up to freezing, as well as abrupt warming or cooling (over 3°C). According to the widely accepted Rass scale, the first stage of the Pacific cod embryogenesis takes 21% of its total duration, the second stage 23%, the third, 17%, and the fourth, 39%. However, at a temperature below 0°C, the relative duration of the stages of cleavage and embryonic shield was slightly shortened, whereas the mature embryo stage extended to almost half of the embryogenesis period. A more comprehensive analysis of temperature effects on embryogenesis revealed that the reduction of the rate of embryogenesis upon a temperature decrease occurred mostly at later stages of embryo growth. Modeling of development using defined morphological characters showed that the duration of embryogenesis grew linearly as the incubation temperature dropped in the first half of the embryogenesis and exponentially in the second half. A function was selected that described the obtained results most satisfactorily and that could be used for estimating the duration of the entire embryogenesis or any its stages within the range of water temperatures typical for Pacific cod.     

The role of temperature in the population dynamics of smelt <Emphasis Type="Italic">Osmerus eperlanus eperlanus</Emphasis> m. <Emphasis Type="Italic">spirinchus</Emphasis> Pallas in Lake Peipsi (Estonia/Russia)

We analysed lake smelt (Osmerus eperlanus eperlanus m. spirinchus Pallas.) population dynamics in relation to water level and temperature in Lake Peipsi, Estonia/Russia, using commercial fishery statistics from 1931 to 2004 (excluding 1940–1945). Over this period, smelt provided the greatest catch of commercial fish although its stock and catches have gradually decreased. At times, catches of smelt were quite variable with a cyclic character. Disappearance of smelt from catches in years 1973–1975 was the result of summer fish kill. Regression analysis revealed a significant negative effect of high temperature on the abundance of smelt stock, while the effect of water level was not significant. Our results suggest that critical factors for the smelt population are the absolute value of water temperature in the hottest period (≥20°C) of summer and the duration of this period. These weather parameters have increased in synchrony with smelt decline during the last 7 decades. There appeared to be a significant negative effect of hot summers on the abundance of smelt operating with a lag of one and 2 years, which can be explained by the short life cycle (mainly 1–2 years) of this species.     

Thermal and thermoperiodic effects on larval development and diapause in the European corn borer, Ostrinia nubilalis

Effects of temperature and thermoperiod on larval development and the induction of diapause were investigated in the European corn borer, Ostrinia nubilalis. Developmental threshold temperatures characteristic of the first four larval instars were estimated under both thermoperiods and constant temperatures. Threshold values were similar under the two conditions, but the 4th-larval instar was shown to display a significantly lower developmental threshold temperature than was characteristic of the earlier instars. Although developmental times (days per instar) were not greatly affected by fluctuating temperature regimes, the quantity of growth (weight, head width) during the 4th and 5th (last) stadia was found to be much greater under thermoperiodic regimes than under comparable constant temperature conditions. By means of thermoperiodic regimes having identical mean temperatures but different cryophase durations, it was demonstrated that the induction of diapause is dependent on the duration of the cryophase rather than on the mean temperature of the thermoperiod. To be effective, the cryophase must be colder than the insect's thermoperiodic response threshold. It was also demonstrated that thermoperiodic responses that are readily produced under continuously dark rearing conditions are not manifested under continuous light.     

Lie Group Analysis of the Photo-Induced Fluorescence of Drosophila Oogenesis with the Asymmetrically Localized Gurken Protein

Lie group analysis of the photo-induced fluorescence of Drosophila oogenesis with the asymmetrically localized Gurken protein has been performed systematically to assess the roles of ligand-receptor complexes in follicle cells. The (2×2) matrix representations resulting from the polarized tissue spectra were employed to characterize the asymmetrical Gurken distributions. It was found that the fluorescence of the wild-type egg shows the Lie point symmetry X ₂₃ at early stages of oogenesis. However, due to the morphogen regulation by intracellular proteins and extracellular proteins, the fluorescence of the embryogenesis with asymmetrically localized Gurken expansions exhibits specific symmetry features: Lie point symmetry Z ₁ and Lie point symmetry X ₁. The novel approach developed herein was successfully used to validate that the invariant-theoretical characterizations are consonant with the observed asymmetric fluctuations during early embryological development.     

Heterochronic shifts in germband movements contribute to the rapid embryonic development of the coffin fly Megaselia scalaris

The coffin fly, Megaselia scalaris, is a species of medical and forensic importance and is increasingly being used for the study of genetics. Postmortem interval can be estimated based on the life stage of M. scalaris recovered from corpses, therefore many studies have addressed the duration of each life stage. These studies demonstrate that embryogenesis completes significantly faster in M. scalaris than in the congener Megaselia abdita and faster even than the 24 h needed for Drosophila melanogaster embryogenesis. However, until now it has been unclear if this increased speed is achieved by reducing developmental time across all embryonic stages or by the acceleration of individual stages and processes. Here I use time-lapse imaging to create a staging scheme for M. scalaris embryogenesis. Comparison of stages between D. melanogaster and both Megaselia species reveals that heterochronic shifts, simultaneous morphogenetic movements and compression of individual stages all contribute to the rapid development of M. scalaris.     

Developmental and Hormonal Regulation of Genes Coding for Proline-Rich Proteins in Female Inflorescences and Kernels of Maize

The pattern of expression of two genes coding for proteins rich in proline, HyPRP (hybrid proline-rich protein) and HRGP (hydroxyproline-rich glycoprotein), has been studied in maize (Zea mays) embryos by RNA analysis and in situ hybridization. mRNA accumulation is high during the first 20 d after pollination, and disappears in the maturation stages of embryogenesis. The two genes are also expressed during the development of the pistillate spikelet and during the first stages of embryo development in adjacent but different tissues. HyPRP mRNA accumulates mainly in the scutellum and HRGP mRNA mainly in the embryo axis and the suspensor. The two genes appear to be under the control of different regulatory pathways during embryogenesis. We show that HyPRP is repressed by abscisic acid and stress treatments, with the exception of cold treatment. In contrast, HRGP is affected positively by specific stress treatments.