Stable Isotope Analysis (SIA) of carbon and nitrogen is useful tool for the understanding functional roles of target organisms in biological interactions in the food web. Recently, mixing model based on SIA is frequently used to determine which of the potential food sources predominantly assimilated by consumers, however, application of model is often limited and difficult for non-expert users of software. In the present study, we suggest easy manual of R software and package SIAR with example data regarding selective feeding of crustaceans dominated freshwater zooplankton community. We collected SIA data from the experimental mesocosms set up at the littoral area of eutrophic Chodae Reservoir, and analyzed the dominant crustacean species main food sources among small sized particulate organic matters (POM, <50 μm), large sized POM (>50 μm), and attached POM using mixing model. From the results obtained by SIAR model, Daphnia galeata and Ostracoda mainly consumed small sized POM while Simocephalus vetulus consumed both small and large sized POM simultaneously. Copepods collected from the reservoir showed no preferences on various food items, but in the mesocosm tanks, main food sources for the copepods was attached POM rather than planktonic preys including rotifers. The results have suggested that their roles as grazers in food web of eutrophicated reservoirs are different, and S. vetulus is more efficient grazer on wide range of food items such as large colony of phytoplankton and cyanobacteria during water bloom period.

Planktonic crustaceans were collected monthly around Hamduck, northern part of Cheju Island from April 1989 to March 1990. Occurrence of mean individuals (244 rods. m^(-3)) from inner~ay stations was 2.4 times higher than that (102 rods. m^(-3)) in outer-bay stations. Mean biomass (wet weight, 18.6 mgm^(-3)) from inner-bay stations was 3.6 times higher than that(5.2 mgm^(-3)) in outer-bay ones. The estimated mean values (251.5 ㎍Cm^(-3)d^(-1)) of daily production from inner-bay, having 141.1 ㎍Cm^(-3)d^(-1) of annual mean, was 2.8 times higher than that (90 ㎍Cm^(-3)d^(-1)) in outer-bay. The ratio of daily production of biomass with average value 0.17 suggested a high turnover rate to maintain a temperate costal ecosystems, in spite of a low biomass around Cheju Island.

1987년 6월-1988년 4월까지 격월로 제주도 해안선주변 10개 정점에서 부유성 갑각류의 현존량과 생산량을 야간채집, 조사하였다. 계절별 평균개체수는 12월에 가장 낮고, 6월에 가장 높았는데, 이들 개체의 대부분(90% 이상)은 90μm 망목의 네트로 채집된 것으로 이뤄졌다. 계절별 평균 현존량의 범위는 6.6-55.0mgm^(-1)(평균 16mgm^(-3))이고, 여름에 높았다. 일일평균 생산량 역시 여름(369μgCm^(-3)d(-1))에 높고 겨울(112μgCm^(-1)d^(-1))에 낮았다. P/B의 비(평균 0.25)는, 수온이 높고 소형 동물플랑크톤의 개체수가 많은 계절에 높은 값을 나타냈다.

Although decapod crustaceans are one of the most important fisheries resources with high market value, we still have only limited knowledge about their basic physiology related to growth, development, and reproduction. This is mainly due to the lack of tools to manipulate genetic information leading the phenotype changes. Recently physiological study for decapod crustaceans changed dramatically by both the development of next-generation sequencing (NGS) technology and RNA interference (RNAi). Significant decrease in the cost for reading genome or transcriptome allowed the even single lab can manage the omics-level study about the non-model system, decapod crustaceans. As genomic and transcriptomic data increased, we are able to screen novel genes in decapod crustaceans related to growth and development. As another useful tool, gene silencing through RNAi is gaining momentum for decapod crustaceans. RNAi has proven instrumental in a growing number of crustacean species, revealing the functionality of novel crustacean genes. Major research topics in decapod crustaceans include immune response, reproduction, development, homeostasis, molting and growth, and environmental stress. In addition to any changes in phenotype, tanscriptomic analysis induced by the specific gene knockdown by RNAi extended our knowledge of physiological responses of novel crustacean genes. Those new techniques extend our knowledge about crustacean physiology providing the basis for increasing productivity of decapod crustaceans.