Isolation of palm oil-utilising, polyhydroxyalkanoate (PHA)-producing bacteria by an enrichment technique

In early attempts to isolate palm oil-utilising bacteria from palm oil mill effluent (POME), diluted liquid samples of POME were spread on agar containing POME as primary nutrient. 45 purified colonies were screened for intracellular lipids by staining with Sudan Black B. Of these, 10 isolates were positively stained. The latter were grown in a nitrogen-limiting medium with palm olein (a triglyceride) or saponified palm olein (salts of fatty acids) as carbon source. None of the isolates grew in the palm olein medium but all grew well in the saponified palm olein medium. Of the latter however, only one isolate was positively stained with Nile Blue A, indicating the presence of PHA. This method did not successfully generate bacterial isolates which could metabolise palm olein to produce PHA. An enrichment technique was therefore developed whereby a selective medium was designed. The latter comprised minerals and palm olein (1% w/v) as sole carbon source to which POME (2.5% v/v) was added as the source of bacteria. The culture was incubated with shaking at 30 degrees C for 4 weeks. Out of seven isolates obtained from the selective medium, two isolates, FLP1 and FLP2, could utilise palm olein for growth and production of the homopolyester, poly(3-hydroxybutyrate). FLP1 is gram-negative and is identified (BIOLOG) to have 80% similarity to Burkholderia cepacia. When grown with propionate or valerate, FLP1 produced a copolyester, poly(3-hydroxybutyrate-co-3-hydroxyvalerate).     

Purification and Some Properties of Milk Protease

Separation of acetic acid from palm oil mill effluent (POME) to increase its concentration by an anion exchange resin was examined as a preliminary study for its recovery from POME that had been anaerobically treated by sludge from a palm oil mill. This paper concerns the acetic acid thus separated for producing bacterial polyhydroxyalkanoate (PHA) by Alcaligenes eutrophus. It was found that sludge particles in POME strongly inhibited the adsorption of acetic acid on the anion exchange resin. Removing the sludge particles from the POME facilitated the separation of acetic acid from the POME efficiently. The concentrated acetic acid thus obtained from anaerobically treated POME could be used as a substrate in the fed-batch production of polyhydroxyalkanoate by Alcaligenes eutrophus.     

Screening and identification of polyhydroxyalkanoates producing bacteria and biochemical characterization of their possible application

Polyhydroxyalkanoates (PHAs) accumulating bacteria were isolated under various selective conditions such as pH, salt concentrations and types of heavy metal. Fifty strains of bacterial isolates were found to belong to Bacillus, Proteus, Pseudomonas, Aeromonas, Alcaligenes and Chromobacterium, based on phenotypical features and genotypic investigation. Only twenty five bacterial isolates were selected and observed for the production of PHAs. Interestingly, bacteria belonging to Firmucutes Bacillus sp. produced a high amount of PHAs. The maximum PHAs were accumulated by B. licheniformis PHA 007 at 68.80% of dry cell weight (DCW). Pseudomonas sp., Aeromonas sp., Alcaligenes sp. and Chromobacterium sp. were recorded to produce a moderate amount of PHAs, varying from 10.00-44.32% of DCW. The enzymatic activity was preliminarily analyzed by the ratio of the clear zone diameter to colony diameter. Bacillus gave the highest ratio of hydrolysis zone which corresponds to the highest hydrolytic enzyme activities. Bacillus licheniformis PHA 007 had the highest lipase and protease activity at 2.1 and 5.1, respectively. However, the highest amylase activity was observed in Bacillus sp. PHA 023 at 1.4. Determination of metabolic characteristics was also investigated to check for their ability to consume a wide range of substrates. Bacillus, Aeromonas sp. and Alcaligenes sp. had great ability to utilize a variety of substrates. To decrease high PHA cost, different sources of cheap substrates were tested for the production of PHAs. Bacillus cereus PHA 008 gave the maximal yield of PHA production (64.09% of DCW) when cultivated in anaerobically treated POME. In addition, the accumulation of PHA copolymers such as 3-hydroxyvalerate and 3-hydroxyhexanoate was also observed in Bacillus and Pseudomomas sp. strain 012 and 045, respectively. Eight of the nine isolates accumulated a significant amount of PHAs when inexpensive carbon sources were used as substrates. Here it varied from 1.69% of DCW by B. licheniformis PHA 007 to 64.09% of DCW by B. cereus PHA 008.     

Isolation of bacteria producing polyhydroxyalkanoates (PHA) from municipal sewage sludge

Bacterial isolates from sludge samples collected at a local municipal sewage treatment plant were screened for bacteria producing polyhydroxyalkanoates (PHA). Initially Sudan black B staining was performed to detect lipid cellular inclusions. Lipid-positive isolates were then grown in a nitrogen limitation E2 medium containing 2% (w/v) glucose to promote accumulation of PHA before the subsequent staining with Nile blue A. The positive isolates were quantified initially with a u.v. spectrophotometer, for a very large number of isolates (105) and among them high PHA-producing isolates (15) were selected and were confirmed by gas chromatographic analysis. The GC analysis showed the polymers produced by 13 of the selected isolates to be polyhydroxybutyrate (PHB), and the remaining two isolates produced polyhydroxybutyrate-co-hydroxyvalerate (PHB-co-HV) copolymer. The proportion of the PHA-positive bacterial isolates showed variability in the number of PHA accumulators during various months. The correlation of PHB production with the cell dry weight (CDW) was found to be statistically significant. The metabolism of PHB in these selected 15 isolates was studied using the Nile blue A staining, which showed an initial increase in the fluorescence followed by a decline, on further incubation. All the selected 15 isolates were classified to genus level by studying their morphological and biochemical characteristics. There were seven Bacillus species, three Pseudomonas species, two Alcaligenes species, two Aeromonas species, and one Chromobacterium species.     

Benthos and zooplankton of coal strip mine ponds in the mountains of northwestern Colorado,U.S.A.

Zooplankton, benthos and associated physico-chemical conditions were sampled in coal strip-mine ponds in northwestern Colorado from June 1977 to May 1978. Two spoils ponds derived all of their drainage from the coal mine, but differed in age; one pond received only partial drainage from mine spoils; a control pond was located in an adjacent drainage basin. Acid mine drainage was not observed, although total dissolved solids (TDS), nitrate and sulfate values were higher in the spoils ponds than in the control pond. Net zooplankton were less abundant in the spoils ponds, although standing stock of benthos exhibited a progressive decrease from the youngest spoils pond to the control pond. Zooplankton and benthos species diversity values were lower in the ponds affected by mine drainage. Certain groups of zooplankters (Cladocera) and benthos (Trichoptera, Amphipoda, Hydracarina, and Sphaeriidae) were rare or absent in the youngest spoils pond. Percentage Similarity Coefficients indicate that colonization phenomena (age and distance from a source of colonizers) may be responsible, in part, for the faunal differences between ponds, since the higher levels of nitrate, sulfate, and TDS in the spoils ponds were generally within the tolerance range of aquatic organisms.     

The distribution of pond snail communities across a landscape: separating out the influence of spatial position from local habitat quality for ponds in south-east Northumberland,UK

Ponds support a rich biodiversity because the heterogeneity of individual ponds creates, at the landscape scale, a diversity of habitats for wildlife. The distribution of pond animals and plants will be influenced by both the local conditions within a pond and the spatial distribution of ponds across the landscape. Separating out the local from the spatial is difficult because the two are often linked. Pond snails are likely to be affected by both local conditions, e.g. water hardness, and spatial patterns, e.g. distance between ponds, but studies of snail communities struggle distinguishing between the two. In this study, communities of snails were recorded from 52 ponds in a biogeographically coherent landscape in north-east England. The distribution of snail communities was compared to local environments characterised by the macrophyte communities within each pond and to the spatial pattern of ponds throughout the landscape. Mantel tests were used to partial out the local versus the landscape respective influences. Snail communities became more similar in ponds that were closer together and in ponds with similar macrophyte communities as both the local and the landscape scale were important for this group of animals. Data were collected from several types of ponds, including those created on nature reserves specifically for wildlife, old field ponds (at least 150 years old) primarily created for watering livestock and subsidence ponds outside protected areas or amongst coastal dunes. No one pond type supported all the species. Larger, deeper ponds on nature reserves had the highest numbers of species within individual ponds but shallow, temporary sites on farm land supported a distinct temporary water fauna. The conservation of pond snails in this region requires a diversity of pond types rather than one idealised type and ponds scattered throughout the area at a variety of sites, not just concentrated on nature reserves. Handling editor: B. Oertli     

Effects of rainfall on water quality in six sequentially disposed fishponds with continuous water flow.

An investigation was carried out during the rainy period in six semi-intensive production fish ponds in which water flowed from one pond to another without undergoing any treatment. Eight sampling sites were assigned at pond outlets during the rainy period (December-February). Lowest and highest physical and chemical parameters of water occurred in pond P1 (a site near the springs) and in pond P4 (a critical site that received allochthonous material from the other ponds and also from frog culture ponds), respectively. Pond sequential layout caused concentration of nutrients, chlorophyll-a and conductivity. Seasonal rains increased the water flow in the ponds and, consequently, silted more particles and other dissolved material from one fish pond to another. Silting increased limnological variables from P3 to P6. Although results suggest that during the period under analysis, rainfall affected positively the ponds' water quality and since the analyzed systems have been aligned in a sequential layout with constant water flow from fish ponds and parallel tanks without any previous treatment, care has to be taken so that an increase in rain-induced water flow does not have a contrary effect in the fish ponds investigated.     

Detection of Arcobacter spp. in piggery effluent and effluent-irrigated soils in southeast Queensland

AIMS: To investigate the occurrence and levels of Arcobacter spp. in pig effluent ponds and effluent-treated soil. METHODS AND RESULTS: A Most Probable Number (MPN) method was developed to assess the levels of Arcobacter spp. in seven pig effluent ponds and six effluent-treated soils, immediately after effluent irrigation. Arcobacter spp. levels in the effluent ponds varied from 6.5 x 10(5) to 1.1 x 10(8) MPN 100 ml(-1) and in freshly irrigated soils from 9.5 x 10(2) to 2.8 x 10(4) MPN g(-1) in all piggery environments tested. Eighty-three Arcobacter isolates were subjected to an abbreviated phenotypic test scheme and examined using a multiplex polymerase chain reaction (PCR). The PCR identified 35% of these isolates as Arcobacter butzleri, 49% as Arcobacter cryaerophilus while 16% gave no band. All 13 nonreactive isolates were subjected to partial 16S rDNA sequencing and showed a high similarity (>99%) to Arcobacter cibarius. CONCLUSIONS: A. butzleri, A. cryaerophilus and A. cibarius were isolated from both piggery effluent and effluent-irrigated soil, at levels suggestive of good survival in the effluent pond. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study to provide quantitative information on Arcobacter spp. levels in piggery effluent and to associate A. cibarius with pigs and piggery effluent environments.     

不同水深条件下刺参养殖池塘大型底栖动物群落结构季节性变化特征

于2012年7月至2013年4月调查了荣成靖海湾3个不同水深的刺参(Apostichopus japonicus)养殖池塘内大型底栖动物的构成,以了解不同水深对刺参养殖池塘环境条件的影响以及由此引起的大型底栖生物群落结构的改变。结果表明:3个不同水深梯度池塘(1#浅水位、2#正常水位和3#高水位)底部光照强度、叶绿素a(Chla)和总有机物(TOM)含量存在显著差异,各池塘水温差异不显著。光强、Chla和TOM含量在夏季、冬季和春季均表现为1#池塘显著高于3#池塘;秋季各池塘间光强和TOM含量差异不显著,Chla含量则表现为3#池塘显著高于1#池塘。各季节3个池塘间大型底栖动物在种类组成、丰度、生物量和多样性指数上均存在显著性差异。大型底栖动物丰度和生物量夏季均表现为1#池塘显著高于3#池塘,秋季和冬季则相反;春季1#池塘丰度显著高于3#池塘,生物量则差异不显著。这些差异主要与其各自优势种及其优势度指数大小有关。大型底栖动物多样性指数夏季和秋季均表现为1#池塘高于3#池塘,春季则相反,冬季各池塘间多样性指数差异不显著。单因子相似性分析(ANOSIM)表明,各季节3个池塘间大型底栖动物群落结构均存在显著差异,表明水深梯度对刺参养殖池塘大型底栖动物群落结构造成显著性影响。相似性百分比分析(SIMPER)显示,各季节对3个池塘间大型底栖动物群落差异起主要作用的物种为各个池塘的优势种。典范对应分析(CCA)表明,水深、Chla和TOM含量为影响大型底栖动物群落的主要环境因子。     

轮虫培育池生态系统各有机碳库储量及其日变化

2001年5～6月对辽宁省盘锦光合水产有限公司的两种模式轮虫培育池有机碳库储量及动态进行了研究.结果表明,静水池溶解有机碳（DOC）和颗粒有机碳（POC）库储量平均值分别为5.69±2.90 mg·L^-1和24.56 ± 2.12 mg·L^-1;流水池DOC和POC分别为9.61±3.17 mg·L^-1和24.13 ±2.91 mg·L^-1.流水池和静水池TOC、DOC和POC的比例分别为 1∶0.75∶0.25和1∶0.82∶0.18.POC含量高的池塘DOC含量也较高.流水池的POC、DOC周日变动幅度大,静水池昼夜变动幅度小.流水池POC含量白天(5:00～17:00)升高,静水池降低,夜间(15:00～23:00)两池POC含量均降低.从23:00至次日5:00上升,两池分别在17:00和5:00达到高峰.白天(5:00～17:00) 流水池DOC/POC升高,静水池降低;夜间(17:00～23:00)两池均上升,23:00 至次日5:00则呈下降趋势.     

Isolation of poly(3-hydroxybutyrate-<Emphasis Type="Italic">co</Emphasis>-4-hydroxybutyrate) producer from Malaysian environment using γ-butyrolactone as carbon source

Samples from various natural environments in Peninsular Malaysia were screened for microorganisms that are capable of producing poly(3-hydroxybutyrate-co-4-hydroxybutyrate). A total of 663 isolates were isolated and 119 out of these isolates were identified as possible PHA producers based on Nile red staining methods. All these potential producers emitted pink fluorescence when grown on solid mineral salts medium (MSM) containing Nile red and exposed to UV light. The isolates obtained in this study were cultivated in MSM containing γ-butyrolactone as the carbon source. Gas chromatography (GC) analysis confirmed that 95 out of the 119 isolates were PHA producers. Among the 95 positive isolates, 77 isolates produced only P(3HB) homopolymer and 18 isolates produced PHA containing 3-hydroxybutyrate (3HB) and 4-hydroxybutyrate (4HB) monomers. Of these 18 isolates, USMAA1020 was screened as the best P(3HB-co-4HB) producer based on GC analysis. For further confirmation, PHA was extracted from the isolate and analyzed by GC as well as nuclear magnetic resonance (NMR). Results from both analyses confirmed that this isolate was capable of producing PHA containing 3HB and 4HB. Based on, biochemical characterization, 16S rRNA sequencing, DNA base composition, cellular fatty acids analysis and DNA–DNA hybridization, it is clearly indicated that this isolate belongs to the genus Cupriavidus. Poly(3HB-co-4HB) was synthesized by this bacterium in one-stage, two-stage and three-stage cultivation using γ-butyrolactone as the carbon source. The highest 4HB composition of 82 mol% was obtained through three-stage cultivation.     

Stability of toxigenic Microcystis blooms

This is the first detailed study on the occurrence of cyanobacterial toxins in India, where we studied five eutrophic, temple ponds in the vicinity of Varanasi city, Uttar Pradesh, which continuously supported blooms of Microcystis sp. for several years. Bloom material from all five ponds was sampled bi-monthly from September 2003 to August 2004. Analysis of extracts by high-performance liquid chromatography (HPLC) indicated that microcystin-RR (MC-RR) was present all year round at high concentrations (311–1540 μg/g, dry weight), posing a significant health hazard especially since all five ponds are widely used for bathing, washing, cattle drinking supply, irrigation and recreation. In addition, there was unusually low temporal variation in concentration of MC-RR in each pond, <20% variation in four out of five ponds throughout the year.Characterization of microcystin composition of several bloom samples from this study by HPLC–PDA/MS confirmed that additional microcystins were present in many of the samples. The rarely reported, MC-AR was frequently detected in bloom samples from three of the ponds (Adityanagar, Durgakund and Sankuldhara), where it typically represented 20% of the microcystin pool. MC-WR was frequently found in samples from Adityanagar and Sankuldhara, representing 5–10% of the microcystin pool. MC-LR, along with the previously unreported MC-AHar, each represented approximately 5% of the microcystin pool when present. Bloom samples from each pond had a characteristic microcystin profile, when sampled from 2003 to 2006, suggesting persistent species/strain domination.The perennial and consistent nature of the toxic Microcystis blooms in these ponds is highly unusual, in contrast to the commonly encountered temporal and spatial variation of toxigenic and non-toxigenic species. Laboratory isolates from several ponds were shown to produce microcystins, showing similar microcystin composition to the original bloom material.     

Crustacean zooplankton community structure in temporary and permanent grassland ponds

Lentic community structure varies across a size gradient of ponds and lakes with physical factors, such as pond drying, and biotic factors, such as fish predation, determining the species assemblage. We studied the effects of pond drying and fish absence on crustacean zooplankton across a gradient of pond sizes in a Texas grassland. We determined the species compositions and size distributions of crustacean zooplankton in 20 temporary and 18 permanent ponds in April after March rains had refilled the ponds. The surface areas of temporary and permanent ponds ranged from <0.01 to 0.21 ha and 0.04 to 13.8 ha, respectively, and temporary ponds were significantly smaller, on average, than permanent ponds. Fish were absent from all temporary ponds and present in all permanent ponds. We detected a difference in the zooplankton species assemblages of the temporary and permanent ponds. Out of 14 total zooplankton taxa that occurred in eight or more ponds, seven taxa were significantly more prevalent in temporary ponds and four taxa were significantly more prevalent in permanent ponds. The sizes of zooplankton in the temporary fishless ponds were greater than those in the permanent ponds with fish present. We concluded that pond size mediated susceptibility to pond drying, and pond drying determined the presence and absence of fish and their secondary trophic-level effect on zooplankton community structure. Handling editor: Steven Declerck     

Invertebrate communities and turnover in wetland ponds affected by drought

1. Changes to the macroinvertebrate fauna found in small ponds on a freshwater marsh (Aberlady Bay, Scotland) in 1986, 1987 and 1992 were used to assess the impact of the 1988–92 drought on taxon turnover in pond communities. 2. Permanent ponds accumulated taxa over the study period. Ponds that were wet throughout 1986–87 but dried in 1992 lost some of the many taxa associated with permanent water but acquired a reduced fauna typical of temporary ponds. Ponds that were temporary in 1986–87 were dry during most of 1992 and lost almost all aquatic taxa. 3. Faunal turnover was considerable even in permanent ponds. Extinction rates were high for taxa typical of permanent or temporary ponds. Colonization rates were poor for the taxa from permanent water, but high for the taxa from temporary ponds. 4. The importance of colonization and extinction rates as main predictors of the distribution of species between the ponds was looked at using metapopulation incidence functions, where observed incidence of a taxon can be used to predict colonization and extinction rates. Predicted rates were then compared with observed rates. Incidence functions gave reasonable predictions of observed colonization rates but were poor predictors of extinction, even for taxa that appeared likely to be true metapopulations. 5. For the pond fauna, including fugitive species adapted to temporary ponds, whilst colonization may well depend on environmental stochasricity (how long a pond holds water), subsequent survival depends on other, demographic, processes (e.g. finding a mate, predation) rather than the pond drying out.     

Emergence of the damselfly Pyrrhosoma nymphula (Sulzer) (Zygoptera: Coenagrionidae) from two adjacent ponds in northern England

Emergence of the damselfly Pyrrhosoma nymphula was followed closely at two similar and adjacent ponds in northern England. Males emerged earlier than females at both ponds (significantly so at one). The sex ratio was significantly male biased at both ponds. Size of emerging adults declined through the emergence period at both ponds. Adults emerging from one pond did so significantly earlier and were significantly larger than those from the other pond. The density of larvae was approximately twice as high in the pond from which larvae emerged early; this pond was also slightly deeper and usually achieved higher maximum daily water temperatures. These findings are discussed in the light of the conventional view of seasonal regulation in a spring-emerging damselfly.     

Effect of land use on pollution status and risk of fish endocrine disruption in small farmland ponds

To study whether the intensity of agricultural activities affects pesticides loads in pond environment, a large number of Belgian farmland ponds were surveyed in spring 2004. Temporal distribution of pollutants was also investigated over restricted survey ponds sampled three times round year 2007. Sedentary pond Prussian carp juveniles were also captured to determine their brain aromatase activity (AA) and plasma vitellogenin (VTG) levels. Heavy metal distribution was also examined in various pond matrices. Amongst the pesticides analysed, only herbicides were detected. Contamination of pond water by atrazine was frequently observed during spring 2004, while isoproturon and glyphosate were detected round year 2007. Levels of herbicides were inversely related to the distance of ponds to crop field, and values peaked in April or October. Absence of endocrine disruptors in pond water was confirmed by lack of modulation in VTG and AA in male fish. Heavy metals were present in all the pond matrices, but overall contamination levels were low. The results demonstrated that Belgian ponds were mainly contaminated by herbicides and that pond sedentary fish were not affected by endocrine disruptors. They also demonstrated a marked effect of land-use intensity on herbicide pollution which can be mitigated by an adjustment of the buffer zones.     

水蕹菜浮床对草鱼主养池塘轮虫群落结构的影响

研究了水蕹菜浮床对草鱼主养池塘轮虫群落结构的影响,共检出轮虫38种,隶属于2纲14属,其中浮床池塘出现轮虫36种,而非浮床池塘28种。浮床池塘与非浮床池塘的优势种组成基本类似,萼花臂尾轮虫（Brachionus calyciflorus）、裂足臂尾轮虫（Brachionus diversicornis）、裂痕龟纹轮虫（Anuraeopsis fissa）、暗小异尾轮虫（Trichocerca pusilla）以及长肢多肢轮虫（Polyarthra dolichoptera）为共有优势种;浮床池塘与非浮床池塘的轮虫平均密度分别为1892和2255 ind./L,差异极显著（p0.01）;浮床池塘与非浮床池塘轮虫平均生物量分别为1.535和1.405 mg/L,差异不显著（p0.05）。结果表明,水蕹菜浮床显著促进了轮虫种类数增加,提高了轮虫多样性和均匀度,并在一定程度上减缓了轮虫小型化。       

Calculation of the release of total organic matter and total mineral using the hydrodynamic equations applied to palm oil mill effluent treatment by cascaded anaerobic ponds

Anaerobic treatment processes to remove organic matter from palm oil mill effluent (POME) have been used widely in Malaysia. Still the amounts of total organic and total mineral released from POME that may cause degradation of the receiving environment need to be verified. This paper proposes the use of the hydrodynamic equations to estimate performance of the cascaded anaerobic ponds (CAP) and to calculate amounts of total organic matter and total mineral released from POME. The CAP efficiencies to remove biochemical oxygen demands, chemical oxygen demands, total solids and volatile solids (VS) as high as 94.5, 93.6, 96.3 and 98.2 %, respectively, are estimated. The amounts of total organic matter and total mineral as high as 538 kg VS/day and 895 kg FS/day, respectively, released from POME to the receiving water are calculated. The implication of the proposed hydrodynamic equations contributes to more versatile environmental assessment techniques, sometimes replacing laboratory analysis.     

Simple Patchy-Based Simulators Used to Explore Pondscape Systematic Dynamics

Thousands of farm ponds disappeared on the tableland in Taoyuan County, Taiwan since 1920s. The number of farm ponds that have disappeared is 1,895 (37%), 2,667 ponds remain (52%), and only 537 (11%) new ponds were created within a 757 km² area in Taoyuan, Taiwan between 1926 and 1960. In this study, a geographic information system (GIS) and logistic stepwise regression model were used to detect pond-loss rates and to understand the driving forces behind pondscape changes. The logistic stepwise regression model was used to develop a series of relationships between pondscapes affected by intrinsic driving forces (patch size, perimeter, and patch shape) and external driving forces (distance from the edge of the ponds to the edges of roads, rivers, and canals). The authors concluded that the loss of ponds was caused by pond intrinsic factors, such as pond perimeter; a large perimeter increases the chances of pond loss, but also increases the possibility of creating new ponds. However, a large perimeter is closely associated with circular shapes (lower value of the mean pond-patch fractal dimension [MPFD]), which characterize the majority of newly created ponds. The method used in this study might be helpful to those seeking to protect this unique landscape by enabling the monitoring of patch-loss problems by using simple patchy-based simulators.     

PERFORMANCE OF TADPOLES FROM THE HYBRIDOGENETIC RANA ESCULENTA COMPLEX: INTERACTIONS WITH POND DRYING AND INTERSPECIFIC COMPETITION

The performance of three genotypes (LL, LR, RR) of tadpoles resulting from the hybrid mating system of Rana lessonae (phenotype L, genotype LL) and Rana esculenta (phenotype E, genotype LR) was determined in artificial ponds. The effects of interspecific competition and pond drying on growth, development, and survival of tadpoles were used to measure the performance of genotypes and the relative fitness of offspring. Among the three genotypes, tadpoles from the homogametic mating RR had the lowest survival, growth, and development under all environmental conditions. Body size of the LL and LR genotype tadpoles at metamorphosis was reduced by competition and pond drying. Days to metamorphosis were also higher for the LL and LR genotype tadpoles in competition ponds. The proportion of individuals metamorphosing of each genotype was differentially lowered by competition and pond drying. The LL genotype produced more metamorphs than the LR genotype in the constant water level ponds, but the LR genotype produced more in drying ponds. In competition ponds, the LR genotype produced more metamorphs than the LL genotype, but the LL genotype produced more metamorphs in ponds without competition. The RR genotype produced no metamorphs in any of the experimental environments. Increased performance of LR offspring from the heterogametic mating, in harsh conditions, and reduced performance of RR offspring from the homogametic mating, even under favorable conditions, relative to the parental genotype (LL) suggests that the population dynamics of this hybridogenetic system is strongly dependent on mate choice in mixed populations and the subsequent pond environment females select for oviposition and larval development.