The downstream drifting of eggs of brown trout, Salmo trutta L.

The occurrence of eggs in the drift samples was not related to fluctuations in flow rates, but was probably related to the presence of eggs in the gravel. Both the number ( Y eggs 3h⁻¹) and density ( Y eggs 100⁻¹ m⁻³) of eggs in the drift samples increased with increasing water velocity ( V m sec⁻¹), and the relationship between the two variables was well described by the regression equation Y=a V^b where a and b are constants. Comparisons were made between two streams and different, years.     

Fish production in the Jarama River, Central Spain

Fish production was estimated at three sites on the Jarama River, a small, typical upland river in Central Spain. Population estimates were made by the successive removal method of electrofishing. The same six species were recorded at each of the sites: Chondrostoma polylepis, Barbus barbus bocagei, Leuciscus cephalus pyraenaicus, Salmo trutta m. fario, Gobio gobio and Cobitis paludicola , with the first three species always dominant. Density, biomass, production (assuming that N_o is the total number of eggs spawned), and available production were, respectively: 13502-85776 ind. ha⁻¹, 178.6–221.3 kg ha⁻¹, 221.7–583.6 kg ha⁻¹ yr⁻¹, 118.1–271.9 kg ha⁻¹ yr⁻¹. Production estimates based on mortality curves were 7.9–19.5% (mean: 13.7) lower than those based on estimated from the number of eggs laid. Production per unit of area was highest at the widest and deepest site. Brown trout production contributed only 2–4% of the total production for all sites.     

Oxygen uptake in developing eggs and larvae of the cod, Gadus morhua L.

Unfertilised cod eggs showed a mean oxygen uptake rate at 5°C of 0.089 μl O₂, dry wt.⁻¹ h⁻¹; this gradually rose to 0.768 μl O₂ mg dry wt.⁻¹ h⁻¹ in eggs about to hatch. From hatching to complete yolk absorption larvae respired at 1.6 μl O₂, mg dry wt.⁻¹ h⁻¹. During starvation following yolk absorption, uptake fell significantly to 1.1 μl O₂, mg dry ⁻¹ h⁻¹. Much of this decrease in oxygen consumption was shown to be caused by reduction in activity. Loss of weight during the embryo and larval phases could not easily be reconciled with total oxygen consumption; it is suggested that cod embryos and larvae may not rely solely upon endogenous energy reserves during development.     

The reproductive success of pike, Esox lucius: aspects of fecundity, egg density and survival

Power-law relationships have been estimated between fecundity and fish length, weight and age for pike from two gravel pit lakes (Main Lake and St Peter's Lake) in Buckinghamshire, England. Relative fecundity, estimated at 17.6 eggs g⁻¹ for Main Lake pike and 19.4 g⁻¹ for St Peter's Lake pike, did not differ significantly between the lakes. Population fecundity for the Main Lake was estimated at 10.6 million eggs and 6.4 million eggs in 1986 and 1987, respectively.
Experimental work involving samples of eggs from 18 artificially fertilized Main Lake female pike showed a significant relationship between egg diameter and female length, and a significant difference between mean egg diameters for 41-cm and 101-cm females. No significant relationships were found between mean egg size and mean fry size, nor between fry length and adult length. Mean size differences between newly hatched, 18-day-old and 41-day-old fry from the 41-cm and 101-cm females were not significant.
Samples of eggs taken at 2-day intervals from 6 April to 5 May in a pike spawning area of the Main Lake revealed clumped distributions of eggs, with average egg densities ranging from 1 to 47 eggs per 0.071 m² (14–671 m ²) on sand and silt substrata. The maximum egg density of 51 per 0.071 m² (729 m⁻²) was found on flooded grass. The stages of development of the eggs were identified over the sampling period. Survival from stage 1 to fry was estimated at 3–6%. Egg losses were estimated at 9–10% day⁻¹.
Egg survival experiments gave overall hatching success rates of 11 % on sand/silt compared with 2.5% on aquatic plants (1986), and 18.9% on undisturbed sand/silt compared with 7.9% on disturbed sand/silt (1987). The effect of siltation on egg hatching is discussed.     

Sublethal effects of imidacloprid and pymetrozine on population growth parameters of cabbage aphid, Brevicoryne brassicae on rapeseed, Brassica napus L.

Efficiency of imidacloprid and pymetrozine on population growth parameters of cabbage aphid, Brevicoryne brassicae L. （Homoptera： Aphididae） was determined using demographic toxicology by leaf dip method. At first, bioassay tests were performed. The LC50 value and confidence limit for imidacloprid and pymetrozine were 1.61 × 10^-5 mol/L （0.74 × 10^-5-2.66 × 10^-5） and 2.14 × 10^-4 mol/L （1.24 × 10^-4-3.40 × 10^-4）, respectively. To evaluate the sublethal effect of two insecticides on population growth parameters of cabbage aphid, LC30 concentrations of imidacloprid and pymetrozine were used at 5 mol/L and 30 mol/L. The experiments were carried out in a incubator at 20±1℃, 60% ± 5% RH and 16：8 （L：D） photoperiod on canola seedlings, Brassica napus L. var. ＇PF＇. Net fecundity rate decreased in both insecticide-treated populations. Intrinsic rates of increase （rm） were lower in imidacloprid and pymetrozine treatments than in controls. Intrinsic birth rates also decreased in treated populations. There was a relative increase in intrinsic death rates of treated populations. The mean generation times and doubling time were also lower in populations treated with insecticides than in controls. There was a considerable reduction in the average numbers of nymphs reproduced per female as compared with the control. The average longevity of female adults in the control was significantly different from those treated with imidacloprid and pymetrozine. However, there was no significant differences in aphid life-table parameters between the two insecticide-treated populations （P 〉 0.01）.     

More effective induction of spawning with long-acting GnRH agonist in the shi drum, Umbrina cirrosa L. (Sciaenidae, Teleostei), a valuable candidate for Mediterranean mariculture

Three experiments of spawning induction in shi drum, Umbrina cirrosa L., were performed in six different commercial Italian hatcheries from May to August (water temperatures: 19–29 °C; salinity: 21–37 p.p.t.). In the first experiment, 119 females (1–4.7 kg), subdivided into 29 lots, were injected with a single dose (2, 5, 8, 10, 15 and 20  μ g kg⁻¹ body weight) of short-acting gonadotropin- releasing hormone agonist (GnRHa-S), des-Gly10,[D-Ala6]-LH-RH ethylamide. In the other two experiments, 85 females (0.7–5.8 kg), subdivided into 22 and four lots, were treated with one (40 or 80  μ g kg⁻¹) or three doses (40  μ g kg⁻¹) of long-acting GnRHa (GnRHa-L), respectively. GnRHa-S stimulated spawning in 69% of the 29 treated lots; the number of eggs laid reached a maximum of 130 000 and a weighted mean of 29 200 total eggs kg⁻¹. GnRHa-L elicited a spawning response in 95% of the 22 one-dose treated lots; the number of laid eggs was higher than with GnRHa-S, reaching a maximum of 213 100 and a weighted mean of 59 400 total eggs kg⁻¹. The yield of developing embryos in 67% of the single GnRHa-L treatments was higher (sometimes up to three times) than with GnRHa-S. Triple treatments of the four lots of females with GnRHa-L always resulted in spawning responses; the best result corresponded to a number of total laid eggs of 358 900 eggs kg⁻¹ with a yield of 177 300 developing embryos.     

Changes in ion content and transport during development of embryonic rainbow trout

Wet mass and water content of four lots of whole eggs did not change throughout embryonic development of rainbow trout Oncorhynchus mykiss. Eggs in all four lots accumulated Na⁺. Eggs in lots 2 and 4 also accumulated Ca²⁺ and Cl^-, whereas eggs in lot 1 showed no significant change in Ca²⁺ or Cl^- and eggs in lot 3 showed no change in Cl^-and a small loss of Ca²⁺. Although the Na⁺ content of embryonic tissues increases in the later stages of development, the yolk sac content remained constant, indicating uptake of Na⁺ from the environment. Na+ uptake by whole eggs was non-saturable, consistent with diffusion of Na⁺ across the chorion into the perivitelline fluid. Na⁺ uptake in dechorionated embryos was saturable, as was Ca²⁺ uptake by both whole eggs and dechorionated embryos, consistent with active uptake or facilitated diffusion mechanisms at the surface of embryos. Very low Ca²⁺ uptake rates in dechorionated embryos suggest that the Ca²⁺ uptake mechanism is not fully developed until after hatching.     

Some aspects of the biology of a cyprinid, Aspius vorax Heckel

Scales were used for the determination of age with back-calculation of length. The oldest fish was VII + years old. Back-calculation did not exhibit Lee's phenomenon. The most rapid growth occurred in summer at water temperatures over 25°C. The growth in weight was c . 331 g year^-1 after IV vears of life. Growth was well described by von Bertalanffy equation : l_l - 91·0 [ l= ^{0·122(l0·25)}] The length-weight relationship followed the cube law (b = 3·0601) K_n ranged from 0·74 to 1·18 with a mean value of 1·0. Spawning occurred in January, fecundity was 74 509 with a mean of 1157 eggs -¹ body weight. Mean diameter of eggs was 1071 (pm). A developed ovary had ova of two sizes, immature oocytes and mature ova. The fish is a carnivorous feeder.     

Physiological mechanisms of buoyancy in eggs from brackish water cod

Newly fertilized eggs of brackish water (Gotland, Baltic Sea) and marine (Lofoten, Norway) cod were investigated with regard to specific gravity, wet and dry weight, water content, chorion weight, and content of protein, free amino acids (FAA), and ions. The eggs had neutral buoyancies equivalent to a salinity of 14^.3% (range 11^.5–16^.2%) in brackish water, and 33^.0% (range 31^.8–34^.5%) in the marine environment. A buoyancy model was developed and showed that this difference was mainly caused by differences in egg water content which was 96.6 ± 0^.47% and 92.7 ± 0.45% in the brackish and marine eggs, respectively. The higher water content of the brackish eggs resulted from increased water uptake during final oocyte maturation due to higher intracellular contents of FAA, Cl ^– and NH₄⁺. SDS polyacrylamide gel electrophoresis of eggs and oocytes, and measurements of egg protein content suggested that the FAA pool of both egg types originated from hydrolysis of specific yolk proteins. The main contributor seemed to be a protein with a molecular weight of 100 kDa.     

Fertilization envelope formation induced by melittin in sea urchin eggs does not depend on Ca2+ signalling

In sea urchin eggs, 10 μg/mL melittin was found to induce fertilization envelope formation without any increase in [Ca²⁺]_i (the intracellular free Ca²⁺ level). On the other hand, 10 μmol/L Br-A23187 and 100 μg/mL SDS induced fertilization envelope formation associated with [Ca²⁺]_i increase. If EGTA was injected into eggs to make an intracellular concentration of 2 mmol/L, [Ca²⁺]_i became quite low and was not altered by melittin, or by Br-A23187 and SDS. In eggs containing EGTA, fertilization envelope formation was induced by melittin even in Ca²⁺-free artificial sea water, but not by Br-A23187 or SDS. Thus [Ca²⁺]_i is essential for induction of a fertilization envelope in sea urchin eggs by Br-A23187 or SDS but not by melittin. Melittin probably activates some Ca²⁺-independent reaction downstream of Ca²⁺-dependent reactions in a sequential reaction system that finally results in fertilization envelope formation.     

Intrinsic rate of population increase of Amitus fuscipennis MacGown and Nebeker (Hym., Platygasteridae) according to climatic conditions and bean cultivar

Data on adult longevity, reproduction and intrinsic rate of population increase of insect parasitoid Amitus fuscipennis MacGown and Nebeker (Hym., Platygasteridae) were obtained under different climatic conditions on two bean cultivars. The insect host was the greenhouse whitefly Trialeurodes vaporariorum (Westwood) (Hom., Aleyrodidae). On cv. Chocho, at 19°C, 75 ± 5% RH and at 22°C, 70 ± 5% RH, mean longevity of adult Amitus females on the host insect was 9.3 and 5.7 days; mean fertility was 64.1 eggs and 52.7 eggs; and r_m values were 0.102 day^–1 and 0.144 day^–1 for the respective conditions. On cv. ICA-Pijao, at 19°C, 75 ± 5% RH, mean longevity was 15.2 days; mean fertility was highest (162.8 eggs); and r_m value was 0.117 day^–1. The r_m values of Amitus were higher than those of its host under the same test conditions. This parasitoid may therefore be a suitable candidate for use in inoculative or seasonal inoculative control programs against T. vaporariorum .     

Induction of Fertilization Membrane Formation and Cyanide-insensitive Respiration in Sea Urchin Eggs by the Treatment with Dimethylsulfoxide Followed by an Incubation in an Ice Bath

In unfertilized eggs of the sea urchin Hemicentrotus pulcherrimus , fertilization membrane formation was induced by an incubation with dimethylsulfoxide (DMSO) for several min at 20°c followed by another incubation in an ice bath. The number of eggs with fertilization membrane, thus obtained, increased in relation to the concentration of DMSO between 1 and 3% (v/v) and was higher than 75% at concentrations above 3%. Fertilization membrane formation by this treatment occurred in Ca²⁺ free- or Ca²⁺, Mg²⁺ free- artificial sea water containing EGTA (50 mM) and was inhibited by verapamil. In the presence of DMSO, the membrane formation was also induced by 2, 4-dinitrophenol or cyanide in considerable number of eggs at 20°c. Eggs remained fertilizable, even when they were kept with DMSO for 1 hr at 20°c. DMSO slightly enhanced respiratory rate in unfertilized eggs and substantially reduced it in fertilized eggs. DMSO-treated eggs exhibited cyanide-insensitive respiratory burst following chilling in an ice bath or by adding DNP or cyanide, in a similar manner to the burst induced by sperm.     

Effects of elevated carbon dioxide and ozone on aphid oviposition preference and birch bud exudate phenolics

The effect of atmospheric change on birch aphid ( Euceraphis betulae Koch) oviposition preference was examined and plant characteristics that are possibly responsible for the observed effects were investigated. It was hypothesized that the increasing concentrations of CO₂ and O₃ affect singly or in combination the oviposition of birch aphids via changes in host plant characteristics. Two genotypes of field-growing silver birch ( Betula pendula Roth) trees (clones 4 and 80), which were exposed to doubled ambient concentration of CO₂ and O₃, singly and in combination, in a 3-year open-top chamber experiment, were used in an aphid oviposition preference test. It was found that elevated CO₂, irrespective of ozone concentration, increased the number of aphid eggs laid on clone 4, but not in clone 80. Several flavonoid aglycones were identified from the exudate coating of birch buds. Although elevated CO₂ and O₃ affected these phenolic compounds in clone 4, the effects did not correlate with the observed changes in aphid oviposition. It is suggested that neither bud length, which was not affected by the treatments, nor surface exudate phenolics mediate birch aphid oviposition preference.     

Activation of Sea Urchin Eggs by Halothane and Its Inhibition by Dantrolene

Eggs of the sea urchin, Hemicentrotus pulcherrimus , were stimulated by halothane, known to induce Ca²⁺ release from sarcosome, to cause fertilization membrane formation in normal and Ca²⁺ free artificial sea water. In the absence of external Ca²⁺, halothane-induced formation of fertilization membrane was inhibited by dantrolene, an inhibitor of Ca²⁺ release from sarcosome, but was not blocked by nifedipine, a Ca²⁺ antagonist specific to Ca²⁺ channels in plasma membrane. Ca²⁺ release from sedimentable fraction isolated from eggs was induced by halothane and was inhibited by dantrolene, but was not blocked by nifedipine. In normal artificial sea water, halothane-caused egg activation was not inhibited either by dantrolene or by nifedipine, but was blocked in the presence of both compounds. ⁴⁵Ca²⁺ influx was substantially stimulated by halothane in eggs exposed to ⁴⁵CaCl₂. Halothane-induced ⁴⁵Ca²⁺ influx into eggs was inhibited by nifedipine but was not blocked by dantrolene. When Ca²⁺ release from intracellular organellae is blocked, Ca²⁺ transport through Ca²⁺ channels in plasma membrane probably acts as a "fail-safe" system to induce an increase in cytosolic Ca²⁺ level, resulting in egg activation.     

Egg development of the stoneflies Siphonoperla burmeisteri(Chloroperlidae) and Dinocras cepùnalotes(Perlidae)

SUMMARY. 1. The duration of egg incubation ( Y ) in Dinocras cephalotes and Siphonoperla burmeisteri was related to constant temperatures from 4 to 24°C, by the regression equations Y=2382 T ^{− 1, 402}(r²=0.992, P<0.001) and y= 2683 T ^−1.667 ( r ²=0.994, P <0.001), respectively. No diapause was observed in either species.
2. Egg incubation in D. cephaloles was slow and took 784.9±92.7 (mean ± SD) degree days between 12 and 20°C. significantly more than in S. burmeisteri (445±76.17 degree days: t = 7.44. d.f.=13, P <0.001).
3. For D. cephalotes hatching occurred at temperatures between 12 and 24°C, and for S . burmeisteri between 8 and 20°C. The mean volume of the eggs of D. cephalotes was about 5 times greater than that of S. burmeisteri and the mean body lengths of the newly-hatched nymphs were 1.13 mm and 0.95 mm respectively.
4. This study shows that the freshwater fauna of northern Fennoscan- dia also contains species with warm stenotherm eggs. D. cephalotes. which is of a Mediterranean origin (Zwick, 1981a), may exist at the limit of its distribution in northern Fennoscandia.     

Seasonal variation in egg production and batch fecundity of European hake Merluccius merluccius (L.) in the Bay of Biscay

Sexually mature female hake Merluccius merluccius with hydrated ovaries were sampled on a monthly basis in the Bay of Biscay, from May 1996 to October 1997 and from March to April 1998. The batch fecundity was positively related to total length. The relative batch fecundity ( F _Brel) varied significantly among months and years, but not between areas, i.e. International Council for the Exploration of the Sea Divisions VIIIa and VIIIb within the Bay of Biscay. Two levels of F _Brel were found in 1997: the highest between January and April (mean ± s . e . 167 ± 5 eggs g⁻¹) and the lowest from May to October (112 ± 3 eggs g⁻¹). Population condition factor and gonado-somatic indices ( I _G) followed the expected trend in relation to the monthly changes in F _Brel during 1997. The F _Brel variation between years was 9% for 1996–1997 and 28% for 1997–1998, and the difference of the I _G was c. 14 and 36%, respectively. Population relative egg production varied from a high value in January to March (985 eggs g⁻¹) to a low egg production between April and October 1997 (445 eggs g⁻¹).     

The Wave Pattern of Free Calcium Release Upon Fertilization in Medaka and Sand Dollar Eggs

A transient rise in the concentration of Ca²⁺ in the cortex upon fertilization was demonstrated in medaka eggs injected with aequorin. Detection of the aequorin luminescence with an ultra-high sensitivity photonic microscope system revealed a wave of increased Ca²⁺ concentration starting at the site of sperm entry (animal pole) and being propagated along the cortex of the egg toward the antipode. The wave traversed the entire egg surface within 2–3 min. The peak value of the aequorin luminescence, and therefore the peak value of the Ca²⁺ transient, was generally higher at the site of sperm entry than in other regions. The peak values of the luminescence (and therefore of the Ca²⁺ concentration in the cortex) remained fairly constant during propagation of the wave. Microinjection of Ca²⁺ into the cortex also induced a Ca²⁺ wave. When the egg was stimulated by microinjection of Ca²⁺ at the equatorial region, the Ca²⁺ wave was propagated at a fairly constant speed over the egg surface, except at the region near the vegetal pole where the wave was retarded. Simultaneous recording of the Ca²⁺ wave and the wave of cortical change (breakdown of cortical alveoli) in eggs during fertilization revealed that the Ca²⁺ wave preceded the wave of cortical change.
A Ca²⁺ wave was also demonstrated in sand dollar eggs, although due to their smaller size the phenomenon was not as clear as in medaka eggs.     

Change in the Respiratory Rate of Sea Urchin Spermatozoa following Sperm-egg Interaction in the Absence of Mg2+

Spermatozoa of the sea urchin, Hemicentrotus pulcherrimus (10⁸ cells/ml), preincubated with unfertilized eggs deprived of jelly coats (more than l0⁵ cells/ml) at 20°C for 20min in Mg²⁺ free artificial sea water containing 1 mM Ca²⁺ (MFASW), exhibited very low respiration, which was enhanced by 2, 4 dinitrophenol (DNP). The fertilization rate in MFASW was usually less than 5% and was about 25% at most. Preincubation with fertilized eggs (with and without a fertilization membrane) in MFASW did not reduced the respiratory rate of spermatozoa. The rate of sperm respiration was lower in MFASW than in artificial sea water (ASW), but was higher than the respiratory rate of spermatozoa preincubated in MFASW with unfertilized eggs. Sperm respiration in MFASW or in ASW was not stimulated by 2, 4 dinitrophenol. Almost complete inhibition of sperm respiration was obtained with unfertilized eggs fixed with glutaraldehyde at concentrations of above 10⁵ cells/ml in MFASW and of about l0⁴ cells/ml in ASW. The respiratory rate of spermatozoa treated with fixed eggs was enhanced by DNP. It is concluded that the respiratory rate of the spermatozoa is reduced by their interaction with unfertilized eggs before their penetration into the eggs.     

Water loss from Jackass Penguin Spheniscus demersus eggs during natural incubation

The water budget of incubating Jackass Penguin eggs was studied on Marcus Island, South Africa, and complementary measurements were made in the laboratory. The mean ambient temperature was 16-5 "C and the mean humidity was 12-4 Torr (89% relative humidity). The temperature of incubated live and water-filled eggs ranged between 14^oCand 37 ^oC. The mean calculated egg temperature was 34-9' C. The mean brood patch temperature was 37-1 ^oC, slightly lower than the cloacal temperature (37.8 ^oC). The mean brood patch area was about 38 cm². The rate of water loss was 411 mg day^-1. The total diffusive water loss during 37 days of incubation was, as predicted, 15-2% of the initial 100-3 g egg mass. The total pore number was 6245 per egg and the shell thickness was 577 fira. It is suggested that the eggshell parameters, incubation length and nesting behaviour are compensated in such a way that an egg-to-nest water vapour pressure difference lower than commonly found is sufficient to bring about the normal total water loss.     

SCN— Blocks Hardening of the Fertilization Envelope of Sea Urchin Eggs and Adhesion of Blastomeres

Sea urchin eggs kept in artificial sea water (ASW) containing 0.01–0.3 M NaSCN in place of NaCI from within 2 min after insemination formed thin, enlarged fertilization envelopes, which were broken on mild agitation of egg suspensions more easily than those formed in Ca²⁺-free ASW. The blastomeres of almost all embryos derived from eggs treated with 0.2M SCN^— for 1 hr dissociated spontaneously, and did not reassociate with other blastomeres appreciably. Thus SCN^— probably denaturated some compound(s) participating in blastomere binding and hardening of the fertilization envelope. Abnormal arrangements of blastomeres, probably due to incomplete blastomere dissociation, were observed in embryos derived from eggs treated with 0.1 M SCN^— for 1 hr. Treatment of fertilized or unfertilized eggs with 0.05–0.1 M SCN^— for a short period caused concentration-dependent block of morphogenic processes such as formation of the archenteron and pluteus arms in the post-hatching period. The effects of SCN^— on morphogenesis were not inhibited by furosemide or 4,4'-diisothiocyano 2,2'-disulfonic stilbene. Presumably, the denaturation of several compounds in the egg surface by SCN^— causes abnormal morphogenesis of embryos. The inhibitory effects of SCN^— on hardening of the fertilization envelope, blastomere binding and morphogenesis were greater in the absence of Ca²⁺.