Cultivation of marine copepods for genetic and evolutionary research

Beneficial microbes to suppress Vibrio and improve the culture performance of copepod Tigriopus japonicus Mori

The use of beneficial microbes, i.e., probiotics, to reduce pathogens and promote the performance of the target species is an important management strategy in mariculture. This study aimed to investigate the potential of four microbes, Debaryomyces hansenii, Ruegeria mobilis, Lactobacillus plantarum, and Bacillus subtilis, to suppress Vibrio and increase survival, population growth and digestive enzyme activity (protease, lipase, and amylase) in the harpacticoid copepod, Tigriopus japonicus. Copepod, T. japonicus stock culture with an initial mean density of 50 individual/mL (25 adult male and 25 adult female) was distributed into five treatments (i.e., four experimental and a control, each with four replicates; repeated twice) using 20 beakers (100 mL capacity each). The copepods were fed a mixture of the dinoflagellate Alexandrium tamarense and the diatom Phyaeodactylum tricornutum (3 × 104 cells/mL-1). Each microbe's concentration was adjusted at 108 CFU/mL-1 and applied to the culture condition. D. hansenii, L. plantarum, and B. subtilis all improved the copepods' survival and population growth, likely by including a higher lipase activity (P < 0.05). In contrast, using R. mobilis did not improve the copepod's culture performance compared to control. B. subtilis was the most effective in decreasing the copepod's external and internal Vibrio loading. The probiotic concentrations in the copepod decreased within days during starvation, suggesting that routine re-application of the probiotics would be needed to sustain the microbial populations and the benefits they provide. Our results demonstrated that D. hansenii and B. subtilis are promising probiotics for mass copepod culture as live food for mariculture purposes.

Effects of Oxyrrhis marina (Dinoflagellata), bacteria and vitamin D(2) on population dynamics of Tisbe holothuriae (Copepoda)

Laboratory experiments were performed to determine which food combinations had the most favorable effect on population dynamics of the harpacticoid copepod Tisbe holothuriae. In addition to basic diets of TetraMin (T), rice (R) or a mixture of both (T+R), supplements consisting of the following were given: the heterotrophic dinoflagellate Oxyrrhis marina, a bacterial suspension and vitamin D(2). Results show a beneficial effect of bacteria at a given concentration on T. holothuriae, which is enhanced in combination with vitamin D(2). A higher concentration of bacteria together with vitamin D(2), however, has a reverse effect leading to greater mortality, lower sex ratio and number of ovigerous females, and a dramatic decrease in production of eggs, regardless of the basic diet. We conclude that different concentrations of a given bacterial community may have variable effects on the reproduction of harpacticoid copepods and that, in addition to the bacteria, vitamin D(2) may also play a role in invertebrate nutrition.