Rhodomonas Baltica Research Articles

Influence of algal diet on feeding and egg-production of the calanoid copepod Acartia tonsa Dana

Threshold concentration, retention efficiency and egg-production in the calanoid copepod Acartia tonsa Dana were examined using the algal species Isochrysis galbana clone T-iso, Dunalietta tertiolecta Butcher, Rhodomonas baltica Karsten, Ditylum brightwellii Grunow and Thalassiosira weissflogii Grun. Feeding and egg-production in A. tonsa was shown to be influenced by the size, quantity and quality of the food particles. The small I. galbana (4.8 μm) were inefficiently retained by A. tonsa and maximum ingestion rates on this species were first obtained at algal concentrations s> 1 μg C · ml −1. However, the highest maximum rate of egg-production was obtained when feeding on this algal species with gross efficiencies of 22 and 38% in terms of carbon and nitrogen, respectively. Egg-production in A. tonsa ceased entirely within 4 days of feeding on a sole diet of D. tertiolecta. D. tertiolecta is similar in size to R. baltica but contained only trace amounts of fatty acids higher than C-18 fatty acids. The diatoms D. brightwellii and T. fluviatilis were retained with maximal efficiency but daily egg-production and gross growth efficiency was lower for these species than for I. galbana and R. baltica.

A reappraisal of the genus Rhodomonas (Cryptophyceae)

Rhodomonas baltica, the type species of the controversial genus Rhodomonas (Cryptophyceae), has been re-examined with light and electron microscopy. The results indicate that recognition of Rhodomo...

The cultivation of Acartia tonsa Dana for use as a live food source for marine fish larvae

The marine calanoid copepod Acartia tonsa has been continuously cultivated in the laboratory at the Danish Institute for Fisheries and Marine Research for over 70 generations. A description of the cultivation procedures is presented in this paper. Adult copepods are maintained in 200–450-l tanks and are fed the cryptophyte Rhodomonas baltica. The concentration of adult copepods is held between 50 and 100/l. Eggs are harvested daily and, on average, ca. 25 eggs are collected per female per day.

Amino acids and some other nitrogenous compounds in Calanus finmarchicus: Cowey C. B. and E. D. S. Corner, 1963. J. Mar. Biol. Ass., U.K., 43 (2): 485–493

Diatoms dominate productive regions in the oceans and have traditionally been regarded as sustaining the marine food chain to top consumers and fisheries. However, many of these unicellular algae produce cytotoxic oxylipins that impair reproductive and developmental processes in their main grazers, crustacean copepods. The molecular mode of action of diatoms and diatom oxylipins on copepods is still unclear. In the present study we generated two Expressed Sequence Tags (ESTs) libraries of the copepod Calanus helgolandicus feeding on the oxylipin-producing diatom Skeletonema marinoi and the cryptophyte Rhodomonas baltica as a control, using suppression subtractive hybridization (SSH). Our aim was to investigate differences in the transcriptome between females fed toxic and non-toxic food and identify differentially expressed genes and biological processes targeted by this diatom. We produced 947 high quality ESTs from both libraries, 475 of which were functionally annotated and deposited in GenBank. Clustering and assembling of ESTs resulted in 376 unique transcripts, 200 of which were functionally annotated. Functional enirchment analysis between the two SSH libraries showed that ESTs belonging to biological processes such as response to stimuli, signal transduction, and protein folding were significantly over-expressed in the S. marinoi-fed C. helgolandicus compared to R. baltica-fed C. helgolandicus library. These findings were confirmed by RT-qPCR analysis. In summary, 2 days of feeding on S. marinoi activated a generalized Cellular Stress Response (CSR) in C. helgolandicus, by over-expressing genes of molecular chaperones and signal transduction pathways that protect the copepod from the immediate effects of the diatom diet. Our results provide insights into the response of copepods to a harmful diatom diet at the transcriptome level, supporting the hypothesis that diatom oxylipins elicit a stress response in the receiving organism. They also increase the genomic resources for this copepod species, whose importance could become ever more relevant for pelagic ecosystem functioning in European waters due to global warming.