Effects of incubation temperatures on embryonic development in the Asian yellow pond turtle

The Asian yellow pond turtle, Mauremys mutica (Cantor), is a potential aquaculture target in China owing to the higher values for food and remedy than other species of turtle. In this study, color and morphological changes of fertilized eggs were observed during embryogenesis, and the effects of incubation temperature on embryonic development were analyzed. Both calcium layer and membrane layer are thicker in the middle portion of egg-shell than that in the terminal portion, and become thinner after embryo hatching than before embryonic development. Significant change in the white spot and subsequent white ring on the eggshell occurs during embryonic development. Of five different incubation temperatures used to investigate the effects of incubation temperatures on embryonic development, 29.0 +/- 0.5 degrees C was optimal for embryo survival and development. Moreover, the incubation temperature of 33.0 +/- 0.5 degrees C was harmful effect to embryonic development. The data provide important and useful information for husbandry and management of the Asian yellow pond turtle. (c) 2006 Elsevier B.V. All rights reserved.

Relationship between organic carbon concentration and potential pond bottom soil respiration

There was a positive correlation between the concentration of organic carbon and potential respiration as measured by carbon dioxide evolution (R-2 = 0.923) and oxygen consumption (R-2 = 0.986) in soil samples collected from the bottoms of drained ponds. This finding supports the frequent use of organic carbon analysis as an indicator of sediment respiration rate under optimal conditions in commercial aquaculture facilities. (c) 2005 Elsevier B.V. All rights reserved.

Survival, growth, sex ratio, and maturity of the Chinese mitten crab (Eriocheir sinensis) reared in a Chinese pond

Aspects of the biology of pond-cultured Chinese mitten crab (Eriocheir sinensis H. Milne-Edwards) were studied from June to November 1993. The survival rate of the population was estimated at 18.6%, and there was no significant difference between sexes in growth (t-test, P > 0.05). As the crabs grew from 7.3 to 33.8 mm in mean carapace length, seven molts were observed for the population. The intermolt period ranged from seven to 22 days and lengthened with increased size. Sex ratio at each sampling time did not differ significantly from 1:1 (Chi-square test, P > 0.05). Female crabs presumably required about eleven postlarval molts to reach sexually mature size, which was 34.1 +/- 3.9 (SD) mm. in carapace length in this study.

Studies on the biology of Chaoborus flavicans (Meigen) (Diptera : Chaoboridae) in a fish-free eutrophic pond, Japan

Population dynamics of Chaoborus flavicans larvae of various instars was studied from November 1986 to December 1987 in a eutrophic, fish-free pond, Japan. First and 2nd instar larvae were observed from late April to late October, indicating a reproductive period of about half a year. C. flavicans overwintered in the 4th instar larvae. In water column samples, total density of all instars was 680-23 680 m(-2), and pupal density 0-2 600 m(-2); larvae of the Ist, 2nd, and 3rd instars showed 5-6 density peaks in 1987, suggesting that 5-6 generations occur during a year (peaks of the 4th instar larvae were not clear, probably due to their longer development than those of younger instars). In sediment samples, no Ist and 2nd instar larvae were found, 3rd instar larvae were found occasionally but density of the 4th instar larvae was 280-18 600 m(-2), and pupal density varied between 0-502 m(-2). Fouth instar larvae accumulated in sediment in the cold season and in the water column in the warm season; high temperature and low oxygen concentration were the most important factors limiting the distribution of larvae in the sediment in summer in the NIES pond. The dry weight of total C. flavicans larvae was 0.08-4.2 g m(-2) in sediment samples and 24-599 mu g l(-1) (0.10-2.40 g m(-2)) in water column samples. Comparisons of maximum densities in the NIES pond in different years and in waters of different trophic status show that density is generally higher in eutrophic than in oligotrophic habitats.

Changes in the structure of a zooplankton community during a Ceratium (dinoflagellate) bloom in a eutrophic fishless pond

The community structure of zooplankton was studied in a eutrophic, fishless Japanese pond. The ecosystem was dominated by a dinoflagellate, Ceratium hirundinella, two filter-feeding cladocerans, Daphnia rosea and Ceriodaphnia reticulata, and an invertebrate predator, the dipteran Chaoborus flavicans. The midsummer zooplankton community showed a large change in species composition (the Daphnia population crashed) when a heavy Ceratium bloom occurred. It is shown that (i) the rapid density decline of D.rosea in mid-May was mainly caused by a shortage of edible phytoplankton, which was facilitated by the rapid increase in C.hirundinella abundance; (ii) the low density of D.rosea in June-July was considered to be mainly caused by the blooming of Ceratium hirundinella (which may inhibit the feeding process of D.rosea), while predation by C.flavicans larvae, the changing temperature, the interspecific competition and the scarcity of edible algae were not judged to be important; (iii) the high summer biomass of the planktonic C.flavicans larvae was maintained by the bloom of C.hirundinella, because >90% of the crop contents of C.flavicans larvae were C.hirundinella during this period. The present study indicates that the large-sized cells or colonies of phytoplankton are not only inedible by most cladocerans, but the selective effect of the blooming of these algae can also influence the composition and dominance of the zooplankton community, especially for the filter-feeding Cladocera, in a similar way as the selective predation by planktivorous fish. The large-sized phytoplankton can also be an important alternative food for ominivorous invertebrate predators such as Chaoborus larvae, and thus may affect the interactions between these predators and their zooplanktonic prey. In this way, such phytoplankton may play a very important role in regulating the dynamics of the aquatic food web, and become a driving force in shaping the community structure of zooplankton.

KINETICS OF SIZE-FRACTIONATED AND DISSOLVED ALKALINE-PHOSPHATASE IN A FARM POND

Nutrient addition bioassays were conducted in 10 L carboys with water from a eutrophic farm pond. The four bioassay treatments each conducted in triplicate were control (no nutrients added), +N (160 mu mol L(-1) NH4Cl), +P (10 mu mol L(-1) KH2PO4), and N+P (160 mu mol L(-1) NH4Cl and 10 mu mol L(-1) KH2PO4). The size fractionated (0.2-0.8, 0.8-3, > 3 mu m) contents of the carboys were analyzed after 7 d for alkaline phosphatase activity (APA) and chlorophyll-a content. Chlorophyll data suggested P deficiency in ammonium and control mesocosms and no P deficiency with phosphate additions. Pond water also was collected in June, August, October, and March for measurement of APA. In water from the pond, the greatest V-max of APA usually was associated with microorganisms in the size classes between 0.8-3 mu m. In mesocosm experiments, the N+P treatment increased V-max of dissolved and particulate associated APA in the 0.2-0.8 mu m size range and in dissolved form. The V-max of APA in the largest size-fraction (> 3 mu m) increased markedly with P deficiency (+N treatment) and decreased in the P-enrichment treatment. The patterns of APA and chlorophyll associated with different size fractions often varied independently among different treatments and seasons and not always as a function of P deficiency, indicating the difficulty of attempting to normalize APA to phytoplankton biomass or chlorophyll. The Michaelis half saturation constant of APA in the pond water showed no strong trends with varied seasons or size fraction.

STUDIES ON THE PURIFICATION AND RECLAMATION OF WASTE-WATER FROM A MEDIUM-SIZED CITY BY AN INTEGRATED BIOLOGICAL POND SYSTEM

The feasibility of an inexpensive wastewater treatment system is evaluated in this study. An integrated biological pond system was operated for more than 3 years to purify the wastewater from a medium-sized city, Central China. The experiment was conducted in 3 phases with different treatment combinations for testing their purification efficiencies. The pond system was divided into 3 functional regions: influent purification, effluent upgrading and multi-utilization. These regions were further divided into several zones and subzones. Various kinds of aquatic organisms, including macrophytes, algae, microorganisms and zooplankton, were effectively cooperating in the wastewater treatment in this system. The system attained high reductions of BOD5, COD, TSS, TN, TP and other pollutants. The purification efficiencies of this system were higher than those of most traditional oxidation ponds or ordinary macrophyte ponds. The mutagenic effect and numbers of bacteria and viruses declined significantly during the process of purification. After the wastewater flowed through the upgrading zone, the concentrations of pollutants and algae evidently decreased. Plant harvesting did not yield dramatic effects on reductions of the main pollutants, though it did significantly affect the biomass productivity of the macrophytes. The effluent from this system could be utilized in irrigation and aquaculture. Some aquatic products were harvested from this system and some biomass was utilized for food, fertilizer, fodder and some other uses. The wastewater was reclaimed for various purposes.

Production of astaxanthin from Haematococcus in open pond by two-stage growth one-step process

We have developed a two-stage growth one-step process for cultivation of Haematococcus using a self-designed system that mimics an open pond in the natural environment. The characteristics of this process are green vegetative cell growth and cysts transformation and pigment accumulation that proceed spontaneously and successively in one open photobioreactor. Four strains of Haematococcus (H. pluvialis 26; H. pluvialis 30; H. pluvialis 34; H. pluvialis WZ) were cultured in this imitation system for a duration of 12 days. The changes in cell density and medium pH were closely monitored, and the astaxanthin content and yield of the four Haematococcus strains were measured at the end of 12 days of cultivation. Two of the strains, H. pluvialis 26 and H. pluvialis WZ, were selected as strains suitable for mass culture, resulting in the astaxanthin yield of 51.06 and 40.25 mg L-1 which are equivalent to 2.79 and 2.50% of their dry biomass respectively. Based on the laboratory work, 6 batch cultures of H. pluvialis WZ were conducted successfully to produce astaxanthin in two 100 m(2) open race-way pond by two-stage growth one-step process. The astaxanthin content ranged from 1.61 to 2.48 g 100 g(-1) dry wt., with average astaxanthin content of 2.10 g 100 g(-1) dry wt. Compared with the one-stage production of astaxanthin based on continuous culture, the superiority of our process is that it can accumulate much more astaxanthin in red cysts. Compared with two-stage production of astaxanthin, the advantage of our process is that it does not need to divide the production process into two parts using two bioreactors. The presented work demonstrates the feasibility for producing astaxanthin from Haematococcus using a two-stage growth one-step process in open pond, culture systems that have been successfully used for Spirulina and Chlorella mass culture. The future of Haematococcus astaxanthin production has been also discussed. (C) 2009 Elsevier B.V. All rights reserved.

SOME ASPECTS OF THE GROWTH OF GRACILARIA-TENUISITIPITATA IN POND CULTURE

The effect of temperature, salinity, nitrogen, culture density and depth on the growth of Gracilaria tenuistipitata were investigated between April 1985 and March 1986 in outdoor ponds in Guangxi Province, South China. The mean annual growth rate was 2.4% per day. Under favourable temperatures of 20-30-degrees-C, daily growth rate may reach as high as 3.3%. Salinity had an obvious effect on growth and photosynthesis and growth peaked at 21 parts per thousand, with a broad plateau between 7-27 parts per thousand. Growth experiments showed that a total nitrogen (NH4-N plus NO3-N) concentration of 4 muM was sufficient to enable the plants to maintain a daily growth rate of 2.7%. The best growth of the plant was obtained at a culture density of 0.5-1 kg M-2 and a culture depth of 30 cm in the pond.

Effects of salinity on energy budget in pond-cultured sea cucumber Apostichopus japonicus (Selenka) (Echinodermata: Holothuroidea)

Pond farming for sea cucumber has developed rapidly along the northern coast of China in the recent years. Holothurians inhabiting ponds undergo seasonal fluctuations of salinity. This study deals with the bioenergetic responses of pond-cultured sea cucumbers Apostichopus japonicus (wet weight of 37.5 +/- 1.8 g) to different water salinities [22, 27, 31.5, and 36 practical salinity units (psu)] at 15 degrees C in the laboratory to determine the influence of water salinity on growth and energy allocation in this species. Results show that ingested energy and scope for growth (SFG) were highest at 31.5 psu and then decreased when water salinity was below or above this point. Although energy ingested was lowest at 36 psu, the lowest SFG occurred at 22 psu (only 102.68 +/- 14.26 J g(-1) d(-1)) because animals reared at 22 psu spent much more consumed energy on feces (72.19%), respiration (21.70%), and excretion (2.59%), leaving less energy for growth (3.52%). Results suggest that pond-cultured sea cucumbers could tolerate chronic salinity fluctuations at a range of 22 to 36 psu and grew better between 27 and 31.5 psu, but decreased at salinities above and below the mentioned salinity range. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.

Detection of hybridization between two loach species (Paramisgurnus dabryanus and Misgurnus anguillicaudatus) in wild populations

Artificial interspecific hybrids between large scale loach P. dabryanus and tetraploid pond loach M. anguillicaudatus (Cobitidae, Cypriniformes) are viable. To detect the occurrence of possible natural hybridization, genetic analyses by using microsatellite markers were performed for natural populations of large scale loach and pond loach, the reciprocal laboratory hybrids, and "supposed hybrids" with ambiguous morphology. The fertility of the artificial hybrids was also tested. At one diagnostic microsatellite (Mac50), one out of 20 "supposed hybrids" was identified to be F-1 hybrid between the two loach species because it had the same genotype as that of the laboratory hybrids. The triploid hybrids between the two species were confirmed to be female-sterile. The results show that rare hybridization has occurred between diploid large scale loach and tetraploid pond loach in nature although it may have little effect in genetic introgression. This study is helpful for fish conservation and encourages further investigation on natural hybridization and introgression of loaches.

FLUCTUATION OF SIZE-FRACTIONATED ALKALINE PHOSPHATASE AFTER BLOOM DISAPPEARANCE IN TWO SHALLOW PONDS

The temporal and vertical fluctuations of size fractionated alkaline phosphatase activity (APA) and kinetics parameters as well as orthophosphate (o-P) and chlorophyll concentrations were investigated after bloom disappearance in two shallow ponds A and B from 27 October 2001 to 15 April 2002. Pond A (Microcystis) bloomed seriously but pond B did not. The data of o-P and chlorophyll suggested that phosphorus was the principal limiting nutrimental element and its vertical flux should be regarded as an important driving factor for algal growth. In pond A, the accumulation of algae-derived detritus after bloom disappearance in overlying water stimulated excretion of algal fraction APA, mainly produced by attached bacteria responsible for detritus decomposition, whereas bacterial fraction APA preferred to function in surface water. Interestingly, completely contrary phenomena were observed in pond B. In season, even though no obvious difference for size-fractionated APA in both ponds, the total APA in pond A peaked earlier showing higher activity and efficiency (low K-m and high V-max values) as a result of algal-derived detritus input. In summary, it is suggested that the excretion of alkaline phosphatase with strongly catalyzing efficiency and high activity should be taken as important contributor to algal-derived detritus decomposition, further fueling nutrient recycle and accelerating algal development next year. Furthermore, some inhibitors and surfactants were testified to be good tools to identify the origin of dissolved alkaline phosphatase.

First description of a novel Weissella species as an opportunistic pathogen for rainbow trout Oncorhynchus mykiss (Walbaum) in China

Six strains of Gram-positive, catalase-negative, non-motile, irregular short rod-shaped Weissella bacteria, with width and length of 0.5-0.6 and 1.2-2.7 mu m were isolated from diseased rainbow trout Oncorhynchus mykiss (Walbaum) in winter of 2007 at a commercial fishery in Jingmen, Hubei province, China. The diseased rainbow trout exhibited hemorrhage in eyes, anal region, intestine and abdomen wall, petechia of liver, some fish with hydrocele in stomach. Six isolates had identical biochemical reactions, phylogenetic analysis of 16S rDNA sequences, amplified ribosomal DNA restriction analysis (ARDRA), enzymatic profile analysis and antimicrobial susceptibility results, indicating as a single clonal outbreak. But all were different from any other validated twelve Weissella species in the term of physiological and biochemical characters. It is indicated that isolates are phylogenetically closer to Weissella halotolerans, Weissella viridescens and Weissella minor on 16S rDNA phylogenetic analysis result, than to W halotolerans and W viridescens on the result of ARDRA study and enzymatic profile analysis. Antimicrobial susceptibility testing was used to scan effective drugs for the therapy of this disease. Experimental infection assays with one isolate were conducted and pathogenicity (by intraperitoneal injection) was demonstrated in rainbow trout O. mykiss (Walbaum) and crucian carp (Carassius auratus gibelio) fingerlings. Because no Weissella was detected in fish feedstuffs and pond water, the source of this pathogen remains unknown, and Weissella isolates were regarded as an opportunistic pathogen for rainbow trout. This is the first report of Weissella strains which can cause disease of cultured fish in the world. (C) 2009 Elsevier B.V. All rights reserved.