Population dynamics of marine ciliate Euplotes vannus (Protozoa, Ciliophora) in different artificial seawaters

To study population dynamics of marine ciliates in different artificial seawaters （ASW）, the population growth dynamics of a common marine ciliate Euplotes vannus were investigated using beef extract media and rice media for five types of ASW and natural seawater （NSW）. The results show that： （1） the population growth rate was in the order of NSW〉Flack ASW〉Nakamula ASW〉Schmadz ASW〉Oshima ASW〉Subow ASW and was considerably higher in rice media than in beef extract media （apart from Subow ASW）; （2） the maximum density of E. vannus in stationary phase in each treatment was ranked as Hack ASW〉Nakamula ASW〉Schmadz ASW〉NSW〉Oshima ASW〉Subow ASW, and was again higher in rice media than in beef extract media （except for Subow ASW）; （3） the exponential and stationary phases were longer in rice media than in beef extract media; （4） strains of E. vannus that had been domesticated for 〉1 year in ASW grew significantly slower, with lower maximum density and longer stationary phase than those isolated and maintained in NSW. It was demonstrated that： （1） E. vannus may grow well in Flack, Nakamula and Schmads ASW compared with NSW （mainly in terms of growth rate）; and （2） Oshima ASW is the preferred choice for stock cultures of E. vannus, but the ASWs Flack, Nakamula and Schmadz are preferred for mass culture. These findings suggest that these three ASWs are effective for the cultivation of marine protozoa for experimental studies on ecology, toxicology and molecular biology.

High efficiency of protoplast preparation for artificially cultured Ulva prolifera(Ulvophyceae,Chlorophyta)

Protoplast isolation was relevant for gene manipulation in U lva, and universal protocols have been proposed based on evaluation for various wildly collected species. However, only clonal laboratory cultures were practical for genetic transformation, and whether applicability of such universal protocol existed for these artificial cultures has never been investigated. In this research, samples in different physiological states or developmental stages were tested in U. prolifera. The results proved that the protoplast yields were strongly dependent on the characteristics of samples. Neither F_v/F_m value nor chlorophyll content exhibited an ideal correlation with the protoplast yields. Alternatively, specific growth rate, coupled with developmental stage, could serve as an ef fective combined index to determine the right time for protoplast isolation. According to this instruction, here we reported the highest yields of protoplast((31.5±1.9)×10~6 cells/g f. wt.) in U. prolifera, following comparison between protocols, and further optimizations on enzyme content, incubation period, starting biomass and pretreatment. This specified protocol for artificially cultured clonal samples could meet the need for protoplast-mediated genetic transformation in U. prolifera.

Succession and seasonal variation in epilithic biofilms on artificial reefs in culture waters of the sea cucumber Apostichopus japonicus

Periphytic biofilms in aquaculture waters are thought to improve water quality, provide an additional food source, and improve the survival and growth of some reared animals. In the AsiaPacific region, particularly in China, artificial reefs are commonly used in the commercial farming of sea cucumbers. However, few studies have examined the epilithic biofilms on the artificial reefs. To gain a better understanding of the succession of epilithic biofilms and their ecological processes in sea cucumber culture waters, two experiments were conducted in culture waters of the sea cucumber Apostichopus japonicus in Rongcheng, China, using artificial test panels. On the test panels of succession experiment, more than 67 species were identified in the biofilms. On the test panels of seasonal variation experiment, more than 46 species were recorded in the biofilms. In both experiments, communities of epilithic biofilms were dominated by diatoms, green algae and the annelid Spirorbis sp. In the initial colonization, the dominant diatoms were Cocconeis sp., Amphora spp. and Nitzschia closterium in June, which were succeeded by species of Navicula, Cocconeis and Nitzschia(July to September), and then by Licmophora abbreviata, Nitzschia closterium and Synedra spp. in the following months. A diatom bloom in the autumn and filamentous green algae burst in the summer were also observed. Ecological indices well annotated the succession and seasonal changes in epilithic communities. Multidimensional scaling(MDS) analysis found significant differences in diatom community composition among months and seasons. Fast growth of biofilms was observed in the summer and autumn, whereas the biomass of summer biofilms was largely made up of filamentous green algae. Present results show that the components of epilithic biofilms are mostly optimal foods of A. japonicus, suggesting that biofilms on artificial reefs may contribute important nutritional sources for sea cucumbers during their growth seasons. Future works should include quantitative determination of the contribution of epilithic biofilms to the diet of A. japonicus, potential roles of epilithic biofilms in regulating the water quality of sea cucumber ponds, and the regulation of epilithic biofilms in sea cucumber culture ponds.

ARTIFICIAL CULTURE OF AMPHIOXUS (BRANCHIOSTOMA BELCHERI TSINGTAUENSE)

Mature amphioxus ( Branchiostoma belcheri tsingtauense ) collected by trawl in June, 1994 from Qingdao Shazikou sea area bottom sands, were cultured under controlled indoor conditions, where they spawned and their eggs were fertilized and hatched into larvae which gradually settled at the bottom and dug into the sands after 40-50 days culture in a water trough outdoors. The total survival rate of the larvae(LSR)was 5.5% before they went into the sands, 1.9% in 4 months, 0.7% in 10 months. The survival rate of the young fish which had dug into the sands (YSR) was 35.6% in 4 months, and 12.6% in 10 months. The amphioxus number tended to be constant from the 11th month on. In the first five months after incubation, the amphioxus body length increased by an average of about 1.5 mm a month, and about 0.4 mm a month from Dec. to May of next year. The maximum length after ten months was 24 mm; the average was about 11 mm. After two years culture in the water trough, the maximum length could reach 34-35 mm, when the amphioxus gonads began to develop.

Experimental Studies on the Natural Restoration and the Artificial Culture of the Moss Crusts on Fixed Dunes in the Tengger Desert,China

Soil microbiotic crusts cover extensive portions of the arid and semiarid regions of the world and play an important ecological role.Moss is one of the major components in the crusts.The reproduction and establishment of the mosses are crucial to the formation of moss crusts.Bryum argenteum is the dominant species of moss crusts in the Shapotou region(104°57′E,37°27′N)of the Tengger Desert.In search for the characteristics of natural reproduction and establishment of the mosses,10 quadrates(10×10 cm for each)were obtained by removing the moss crusts in different positions of fixed dunes.These 10 quadrates were observed for 3 years depending on the species’components and coverage.Meanwhile,in the third year,two quadrates(1×1 m for each)were set up in a crustabsent area and two different experiments of the asexual reproduction(broadcast planting and offshoots)were conducted,respectively.The reproductive process was observed under the microscope,and the morphological indicators of the new individuals were measured.The results were compared with the ones from indoor experiments using the same methods.All the results showed the following:(1)70%of the quadrates(i.e.,7 of the 10 quadrates)were recovered within 3–4 years;thus,the quick recovery might be due to the dispersal and reproduction of the fragments of stems and leaves of B.argenteum;(2)as for the two quadrates in the artificial reproduction test,the new plants occupied the uncovered space of the quadrates in 1 month,and there were two main reproduction approaches,one of which was that the stems continually branched and produced young plants,and the other was that the young plants and the fragments of the stems and leaves repeatedly and extensively reproduced protonema,which finally developed into a large number of new plants;(3)the reproductive characteristics were identical,though the protonema in the field was more robust and had more branches than the ones indoors.