Influence of light,DMSO and glycerol on the hatchability ofThamnocephalus platyurus Packard cysts

Effects of two light intensities and different concentration of dimethyl sulfoxide (DMSO) and glycerol on hydrated cyst hatching inThamnocephalus platyurus were studied. A maximum of 65±6% hatching was recorded within seven days at 2500 lux continuous light regime. Hatching was at a minimum during the first two days, peaked between the third and fourth days, decreased thereafter. Hatching success was a function of duration of light exposure. Eight percent of cysts hatched in the dark, while cysts exposed to 24h light and subsequently incubated in the dark showed 27±2% hatching. Hatchability was significantly increased (23%) in 0.0375% DMSO and 0.0125% glycerol. Concentration above 0.05% DMSO and 0.025% glycerol had no or a negative influence on hatching. Since low concentrations of DMSO were non-toxic, apolar compounds like Ca²⁺ ionophore can be dissolved in DMSO to study the role of Calcium in cyst hatching.     

The influence of processing and temperature conditions on hatching of resting eggs of Streptocephalus proboscideus (Crustacea: Branchiopoda: Anostraca)

In large freshwater branchiopods, erratic hatching success of resting eggs is a major obstacle to various applications. Lack of knowledge of the diapause-regulating processes makes control of hatching difficult. In the Sudanese fairy shrimp Streptocephalus proboscideus cysts are considered to include a diapausing and a quiescent fraction. To effect hatching, diapausing cysts have to be activated, while the quiescent portion has to be triggered by suitable environmental conditions. Of several attempts to control hatching with varying production, processing, and incubation conditions, only a few treatments proved consistently successful. Cysts were produced in an indoor culture system under controlled conditions and were harvested, washed, and dried according to defined procedures before processing (if any) and incubation. Hatchability (first-day and cumulative) was consistently higher in chemically decapsulated than in untreated (non-decapsulated) cysts at 25 °C. At a temperature of 28 °C, hatching was comparable in untreated and in decapsulated cysts and was significantly higher than at 25 °C. Pre-treatment with 7.5% NaOCl for 5–10 minutes, resulted in higher hatching than other decapsulation procedures and durations. It is believed that the decapsulation and temperature treatments were only effective in triggering quiescent cysts but did not activate the diapausing fraction.     

Rice bran as a diet for culturing Streptocephalus proboscideus (Crustacea: Anostraca)

We cultured Streptocephalus proboscideus using rice bran as a food source, and compared its growth, mortality, fertility, and cyst hatching with published data on animals fed other food sources. We also analysed the fatty acid profile of animals and cysts. The performance of rice-bran fed shrimp was indistinguishable from that of shrimp fed most other formulated diets, but there are indications that some previously applied diets were either defective in essential fatty acids, or toxic.     

Changes in phosphorus concentrations and pH in the rhizosphere of some agroforestry and crop species

The aim of this work was to assess whether agroforestry species have the ability to acquire P from pools unavailable to maize. Tithonia diversifolia(Hemsley) A. Gray, Tephrosia vogelii Hook f., Zea mays and Lupinus albusL. were grown in rhizopots and pH change and depletion of inorganic and organic P pools measured in the rhizosphere. Plants were harvested at the same growth stage, after 56 days for maize and white lupin and 70 days for tithonia and tephrosia, and the rhizosphere sampled. The rhizosphere was acidified by tithonia (pH change –0.3 units to pH 4.8) and lupins (–0.2 units to 4.9), alkalinised by tephrosia (+0.4 units to pH 5.4), and remained unchanged with maize growth. Concurrent with acidification in the rhizosphere of tithonia there was a decline in resin-P (0.8 g P g^–1). However, there was also a decline in NaOH extractable inorganic P (NaOH-P_i) (5.6 g P g^–1 at the root surface) and organic P pools (NaOH-P_o) (15.4 g P g^–1 at 1.5 mm from the root), which would not be expected without specific P acquisition mechanisms. Alkalinisation of tephrosia rhizosphere was accompanied by changes in all measured pools, although the large depletion of organic P (21.6 g P g^–1 at 5 mm from the root) suggests that mineralisation, as well as desorption of organic P, was stimulated. The size of changes of both pH and P pools varied with distance away from the rhizoplane. Decline of more recalcitrant P pools with the growth of the agroforestry species contrasted with the effect of maize growth, which was negligible on resin-P and NaOH-P_i, but led to an accumulation of P as NaOH-P_o (14.2 g P g^–1 at 5 mm from the root). Overall the depletion of recalcitrant P pools, particularly P_o, suggests that the growth of tithonia and tephrosia enhance desorption and dissolution of P, while also enhancing organic P mineralisation. Both species appear to have potential for agroforestry technologies designed to enhance the availability of P to crops, at least in the short term.     

Soil pH influences embryonic survival in Pseudophryne bibronii (Anura: Myobatrachidae)

Abstract: There has been limited research examining the role that terrestrial habitat characteristics play in influencing persistence of amphibian populations. In this study we investigated the influence of a terrestrial habitat attribute on the distribution of the terrestrial egg‐laying toadlet, Pseudophryne bibronii. Eggs of this species are deposited in depressions, or under leaf litter, and develop to a stage where they can hatch to free swimming tadpoles when water covers breeding sites or embryos are washed into water. Because rainfall can be intermittent, eggs may sit for extended periods in terrestrial nests before sufficient rainfall initiates hatching. Appropriate egg‐laying sites must be chosen by both males and females to ensure embryos survive these periods. A study of 20 sites found that soil pH at sites where P. bibronii were recorded as present was significantly lower than pH at sites where P. bibronii were recorded as absent. To determine whether soil pH influenced the hatching success in P. bibronii, experiments were conducted in which batches of eggs were translocated to local areas with different soil pH. Survival rate of eggs was significantly influenced by relatively small changes in pH, with hatching success higher at lower pH. In a laboratory trial survival of eggs raised on sterilized soil was not affected by soil pH. Fungal infection of eggs was observed in the field and laboratory suggesting that hatching success might be affected via a complex interaction between soil pH, fungi and other soil biota. Choice trials using P. bibronii metamorphs indicated that individuals were capable of distinguishing between small differences in pH. Therefore, distribution of P. bibronii may be influenced by either differential mortality of embryos, or habitat choice by post metamorphic individuals, and further experiments are required to determine the relative importance of these factors.     

Quality evaluation of brine shrimpArtemia cysts produced in Asian salt ponds

Artemia cysts produced in inoculated salt ponds in the Philippines, Thailand and India, were analyzed in comparison with the parental strains used for the inoculations. Cyst hatching efficiency, hatching rate and color changed significantly after inoculation, whereas the cyst's diameters, nauplius survival and nauplius growth remained fairly constant. The nutritional value of theArtemia nauplii was determined in a standard culture test withMysidopsis bahia juveniles as test animals. Production results were compared with the fatty acid profiles of theArtemia nauplii. Low levels of the essential fatty acid 20:53 in one of the produced cyst batches were probably caused by inadequate food conditions in the pond and resulted in poorer growth of theMysidopsis juveniles. Based on the results of this study a distinction is made between essential and nonessential strain selection-criteria forArtemia inoculations and transplantations.     

Effects of crowding on populations of Aedes albifasciatus larvae under laboratory conditions

Aedes (Ochlerotatus) albifasciatus(Macquart 1838) (Diptera: Culicidae) is a neotropical flood water mosquito, incriminated as the main vector of the western equine encephalitis virus, and which affects beef and milk production in central Argentina. The short time required to hatch and develop from egg to adult, usually in temporary pools, suggests a strategy which allows for exploitation of transient pools, thus evading predation and interspecific competition. Under these conditions intra specific competition could represent a major density-dependent source of larval mortality, but the relative importance of density-dependent regulation of mosquito populations has generated controversy. Therefore we examined the effects of larval density on basic population characteristics of Ae. albifasciatusin the laboratory. Larvae were obtained by synchronous hatching of eggs laid by field-trapped females. Emerging larvae (L1) were used to build cohorts of different initial densities, kept in plastic trays with 400 ml of distilled water, and food supplied daily during the first 10 days (0.1 g per larvae day^–1). Age-specific development time and specific and relative mortality were estimated, and their relation to initial larval density was assessed through linear and non-linear regressions and correlation analysis. First hatching was registered 3 h after flooding the eggs. Higher levels of pre-adult mortality were detected in groups with higher densities. Specific mortality and average time to enter a stage of L1 to L3 could directly be related to initial larval density, but no significant relations were found for L4 and pupae. Results suggest that crowding could be a factor capable of regulating the density of natural populations of Ae. albifasciatus.     

Variability of <Emphasis Type="Italic">Artemia salina</Emphasis> cysts from Sabkhet El Adhibet (southeast Tunisia) with special regard to their use in aquaculture

Brine shrimp Artemia (Crustacea, Anostraca) diverge in biometry and nutritional quality. These differences in Artemia characteristics are significant not only from strain to strain but also from one harvest to another within same strain. The main objective of this study was to compare Artemia salina cysts harvested from Sabkhet El Adhibet (southeast Tunisia) on different dates between 2002 and 2007 with special regard to their use in aquaculture, using cysts and naupliar biometrics, protein, carbohydrate, and lipid content. Fatty acid profiles as well as hatching characterisation were also evaluated. Hydrated cysts measures ranged between 258.1 and 263.7 μm, while the freshly hatched nauplii of Artemia measures ranged between 458.1 and 476.1 μm. Lipid contents of the samples ranged from 16.2 to 18.3% of the dry weight. Fatty acid profiles showed that cysts from Sabkhet El Adhibet contain a high quantity of eicosapentaenoic acid (20: 5n-3) with a percentage ranging between 7.8 and 14.3% of the dry weight. The highest hatching efficiency was obtained for decapsulated cysts collected in 2007 (139500 nauplii g⁻¹ of cysts). Cysts treated with hydrogen peroxide had a hatching percentage of 14.49 to 42.99%. The hatching synchronization time for untreated cysts varied between 23.5 to 27.4 h.     

In situ hatching of Artemia monica cysts in hypersaline Mono Lake,California

Two emergence trap designs were tested in Mono Lake, California, to measure in situ hatching of Artemia monica cysts on the lake bottom. One design incorporated a removable sample bottle; the other had a catch tube which was pumped from the surface. Both traps rested on the bottom and had a narrow gap between the collecting funnel and bottom flange to allow the chemical conditions within the trap to be similar to those outside. This gap was open during April and May but, because some animals entered from outside the area enclosed by the trap, the gap was covered with 400 µm or 800 µm screen during June and July. The two trap types without screens sampled a station in oxic water 7 m deep similarly in April and May 1985. Mean daily hatching rates from April to May 1985 ranged from 720 to 25 340 shrimp m^-2 day^-1. In contrast, mean daily hatching rates during the same period at a station in anoxic water 21 m deep were from 3 to 138 shrimp m^-2 day^-1. June and July hatching rates in the shallow station were lower than in the spring, usually less than 1000 shrimp m^-2 day^-1.     

Amino acids as a nitrogen source for Chlorella symbiotic with green hydra

Supply of amino acids may be important in controlling cell division of Chlorella symbiotic with green hydra. Freshly isolated symbionts display characteristics of N-limited algae, and low pH in perialgal vacuoles and high levels of host glutamine synthetase (GS) limit uptake of ammonium. Movement of tritiated amino acids from host to algal pools suggests that symbiotic algae utilize amino acids derived from host digestion of prey. Amounts are significant in relation to host and algal amino acids pools. During host starvation, glutamine produced by host GS may be important as a nitrogen supply to the algae, which take up this amino acid at high rates at low pH.     

The adaptive acid tolerance response in root nodule bacteria and Escherichia coli

Root nodule bacteria and Escherichia coli show an adaptive acid tolerance response when grown under mildly acidic conditions. This is defined in terms of the rate of cell death upon exposure to acid shock at pH 3.0 and expressed in terms of a decimal reduction time, D. The D values varied with the strain and the pH of the culture medium. Early exponential phase cells of three strains of Rhizobium leguminosarum (WU95, 3001 and WSM710) had D values of 1, 6 and 5 min respectively when grown at pH 7.0; and D values of 5, 20 and 12 min respectively when grown at pH 5.0. Exponential phase cells of Rhizobium tropici UMR1899, Bradyrhizobium japonicum USDA110 and peanut Bradyrhizobium sp. NC92 were more tolerant with D values of 31, 35 and 42 min when grown at pH 7.0; and 56, 86 and 68 min when grown at pH 5.0. Cells of E. coli UB1301 in early exponential phase at pH 7.0 had a D value of 16 min, whereas at pH 5.0 it was 76 min. Stationary phase cells of R. leguminosarum and E. coli were more tolerant (D values usually 2 to 5-fold higher) than those in exponential phase. Cells of R. leguminosarum bv. trifolii 3001 or E. coli UB1301 transferred from cultures at pH. 7.0 to medium at pH 5.0 grew immediately and induced the acid tolerance response within one generation. This was prevented by the addition of chloramphenicol. Acidadapted cells of Rhizobium leguminosarum bv. trifolii WU95 and 3001; or E. coli UB1301, M3503 and M3504 were as sensitive to UV light as those grown at neutral pH.     

Growth duration and root length density of Solanum sisymbriifolium (Lam.) as determinants of hatching of Globodera pallida (Stone)

Solanum sisymbriifolium is a trap crop for potato cyst nematodes (PCN). In this study, we quantified the effect of different periods of growth of S. sisymbriifolium and root length density on hatching of Globodera pallida, using potato and fallow treatments as references. One‐year‐old and 2‐year‐old G. pallida cysts were used in greenhouse experiments carried out in containers over 2 years. Two methods were used in study hatching. In the first method, 7.5‐cm‐diameter soil cores were removed and backfilled with infested soil. In the second method, cysts were buried in nylon bags. The soil cores infested with cysts used in the first method had very poor root colonisation as compared to surrounding bulk soil. Therefore, the effect of S. sisymbriifolium was strongly underestimated by the soil core method. Hatching of PCN juveniles from cysts, measured with the nylon bag method, increased with the duration of growth of S. sisymbriifolium from 47% after 6 weeks of crop growth up to 75% after 21 weeks of crop growth. Reductions per depth layer were also correlated with root length density and varied between 42.6% at 0.26 cm cm^?3 and 85.3% at 5.8 cm cm^?3. Based on a single exponential decay function, a general method is presented to estimate for any PCN management measure the average reduction in the number of years needed to ensure that the PCN population falls below a given density. Calculated reductions in the number of years ranged from 2.3 years for 59% hatching (equivalent to 90 days of S. sisymbriifolium) to 4.4 years for 75% of hatching (equivalent to 150 days of S. sisymbriifolium). These reductions were independent of initial and final population density. Our results corroborate the hatch‐inducing effect of S. sisymbriifolium, underline the importance of growth duration and root length density as determinants of the reduction in PCN population that can be achieved and draw attention to the pitfall in methodology that can arise in the study of hatch stimulation.     

Growth and sex ratio of nestlings in two species of crows: how important is hatching asynchrony?

Summary In experimental studies of avian hatching paterns offspring sex has been neglected. This may be a problem if nestling growth and mortality is sex biased, and if this bias is influenced by hatching spread. In a field study of two crow species, the magpie Pica pica and the hooded crow Corvus corone cornix, we manipulated hatching spread. Both species have asynchronous hatching, and adult males are larger than females by 12–14%. The sex ratios obtained from the different experimental groups on day 24 post-hatch (total sample n = 403) did not deviate significantly from unity, nor did the sex ratios obtained among young newly hatched in an incubator (total sample n = 305). Male and female offspring were of similar size at hatching but males were larger on day 24 post-hatch. Males seemed to be more costly to rear than females, judging by the 20% difference in the mean amounts of food found in the gizzards of the young on day 24 post-hatch. Dimorphism in body size did not seem to be influenced by degree of hatching spread. Asynchronous hatching did not seem to be needed to produce high quality offspring of the larger sex (i.e. males), nor did asynchronous hatching help to ensure equal parental investment in male and female progeny. One reason for the latter negative results may be that the size dimorphism of the two crow species studied were relatively small.     

Detection of hatching inhibitors and hatching factor stimulants for golden potato cyst nematode, Globodera rostochiensis, in potato root leachate

In a comparison of four potato varieties, in-soil hatch of the golden potato cyst nematode (Globodera rostochiensis) was positively correlated to in vitro hatch in response to potato root leachate (PRL). The in-soil hatch of cysts of G. rostochiensis to two of the four varieties was significantly less than that of the control (cysts in gravel without potato plants) in the first 2 wk after plant emergence, suggesting the production of hatching inhibitors (HIs) by young potato plants. The hatching factor: hatching inhibitor ratio of PRL was positively associated with the net hatching activity of the PRL. Four zones of HI activity were resolved following gel permeation chromatography of PRL on Sephadex G-10. Hatch-inactive chemicals, which stimulated the activity of hatching factors (HFs) in PRL (hatching factor stimulants, HSs), were also isolated from PRL, hatch levels induced by individual HFs responding differently to the same HS preparation. The complex interactions between individual HFs and other hatching chemicals in PRL was illustrated when addition of the hatch-active potato glycoalkaloid α-solanine caused both inhibition and stimulation of PRL-induced hatch, depending on the α-solanine concentration.     

Cyst Distribution and Hatching Pattern of Chirocephalus ruffoi (Crustacea,Anostraca) in an Experimental Undisturbed Pool

The pattern of cyst distribution in the absence of turbation and their hatching behaviour were studied in an outdoor artificial pool, where just differentiated adults of the anostracan Chirocephalus ruffoi (sex ratio 1:3) lived until it dried up. The horizontal and vertical distributions of cysts in the pool bed were determined. The comparison between cyst bank estimate (Mura , 2004) and the actual number of cysts counted in the pool bed revealed an estimate error of 20.9%. Resting eggs occurred only in the upper 2.5 cm thick soil sections and decreased within this section as depth increased. Peripheral areas of the pool contained significantly larger numbers of cysts than the central area. Multiway analysis on the results recorded in hatching success (nested ANOVA) revealed that the differences were significantly affected by initial soil conditions, treatment and vertical distribution of cysts. Among these factors, vertical distribution (sections nested in cores) was the most influential. Hatching success was significantly inversely related to depth. Differences in the timing of hatching depending on the above considered factors were also noted. A nearly synchronous hatching pattern was observed only for cysts from initially dry sediment of the uppermost layers. In all successively deeper layers, hatching showed multiple peaks and was increasingly delayed and erratic (already mentioned). ANCOVA within each of the experimental conditions revealed significant differences in hatching frequencies (time as covariate) depending on sediment depth. Within any given layer, ANCOVA revealed a significant influence of initial sediment conditions and treatment on the timing of hatching. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Relationship of winter concealment habitat quality on pool use by juvenile spring Chinook salmon (<Emphasis Type="Italic">Oncorhynchus tshawytscha</Emphasis>) in the Grande Ronde River Basin,Oregon USA

Winter concealment habitat quality was assessed and its use by juvenile spring Chinook salmon (Oncorhynchus tshawytscha) quantified in three hatching areas of the Grande Ronde River Basin, Oregon USA. Fish densities were significantly higher in pools with a higher winter concealment habitat index than pools with a lower index. The mean fork length and mean growth rate of fish did not differ between pools with a higher or lower winter concealment habitat index, even though residual fish were significantly larger than fish that emigrated. Biomass–density was significantly higher in pools with a higher winter concealment habitat index than pools with a lower index in all three hatching areas. Biomass–density was positively associated with the amount of cobble substrate (10–24.9 cm/m²) in all three hatching areas, and inversely associated with embeddedness in two of the hatching areas. Results of this study indicate that enhancing winter concealment habitat could improve habitat quality resulting in increased carrying capacity and winter usage by juvenile spring Chinook salmon. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Handling editor: J. A. Cambray     

Characterization of two bacteriocins produced by Leuconostoc mesenteroides L124 and Lactobacillus curvatus L442, isolated from dry fermented sausages

Leuconostoc mesenteroides L124 and Lactobacillus curvatus L442, isolated from dry fermented sausages, produce bacteriocins antagonistic towards closely related species and pathogens, such as Listeria monocytogenes. The bacteriocins were inactivated by proteolytic enzymes and lipase but not by catalase and lysozyme. They were also heat stable, retaining activity after heating at 100 °C for 60 min. The bacteriocins were stable at pH values ranging from 2.0 to 8.0. Bacteriocin production was observed at low temperatures (10 and 4 °C) and in meat juice. The maximum bacteriocin activity was observed at the end of the exponential growth phase. The bacteriocins were produced in media with initial pH values ranging from 5.0 to 7.5, but not in media with a pH lower than 5.0 (weak bacteriocin activity of the antibacterial compound produced by Ln. mesenteroides L124 was observed at pH 4.5). Both bacteriocins exhibited strong bactericidal activity following cell/bacteriocin contact.     

THE EMERGENCE OF LARVAE FROM FREE EGGS OF THE POTATO-ROOT EELWORM HETERODERA ROSTOCHIENSIS (WOLL.)

A technique for conducting hatching experiments on eggs freed from cysts is described. The form of the hatching response was found to be similar to that of eggs contained within cysts, but the response of the free eggs to the hatching stimulus was slightly more rapid. Investigations into factors affecting free egg hatching showed that it was necessary to presoak cysts before extracting the eggs from them for hatching. Eggs taken from dry cysts or from cysts that had been opened or cracked before presoaking did not respond to diffusate. When free eggs and whole cysts were exposed to the same graded series of dilutions of diffusate, the L.A. values (i.e. log concentrations of hatching factor) derived from plotting the hatching curves were in very close agreement.     

Removal of wastewater pathogen indicators in a constructed wetland in Leon, Spain

This paper studies the seasonal presence and removal of the pathogenous micro-organisms Escherichia coli, total coliforms (TC), Clostridium perfringens (Cp), faecal streptococci (FS), Giardia cysts, Cryptosporidium oocysts and helminth eggs, in a constructed wetland treatment system. The removal efficiency of this system with respect to the indicator micro-organisms achieved maximum values in spring and autumn at 99.9% for E. coli and TC, respectively, in winter at 97.0% for FS, in summer at 100% for Clostridium and throughout the year, also at 100%, in the case of Giardia cysts, Cryptosporidium oocysts and helminth eggs. In general, very low protozoan and helminth egg counts were found, and the system demonstrated efficient reduction of the wastewater indicator pathogens.     

Laboratory studies of factors affecting egg hatch of triops longicaudatus (LeConte) (Notostraca : Triopsidae)

Egg hatch was greatest (78.33%) for eggs not previously desiccated. A reduction in numbers hatched occurred as the relative humidity at which they were dried decreased. Some eggs hatched (0.67–79.33%) at pH levels of 3.10–10.01 with the highest hatch at pH 5.60. Water temperature greatly affected egg hatch. No hatch occurred until temperatures were above 14°C. A constant 29°C significantly inhibited hatching. Egg hatch increased 13.00 to 43.42% as salinity decreased from 2200 to 9.24 micromhos/cm. As little as 13 mm of flooded soil covering the eggs prevented them from hatching for 14 days. Eighteen percent hatch resulted when soil and eggs were redistributed to a 1 mm soil layer. Egg samples from the same parent, even though treated similarly, often hatched at greatly varying rates and only rarely was hatching 100% within a replication.