Anti-mitotic activity towards sea urchin embryos in extracts from the marine haptophycean Phaeocystis pouchetii (Hariot) Lagerheim collected along the coast of northern Norway.
The marine bloom-forming alga Phaeocystis pouchetii is suspected to produce some toxic compound responsible for reduced growth, fecundity and survival of other marine organisms. Sea urchin early development was used as a model to investigate the degree and nature of toxicity. Colonial cells of P. pouchetii were collected during its spring-bloom along the coast of northern Norway and maintained in culture for a short period of time in order to evaluate the concentration of toxic compounds present inside the cells or excreted to the surrounding seawater medium. Cells were harvested by filtration and toxins were extracted separately from the collected cells and the filtrate using organic solvents. We found that extracts from the filtered seawater at a concentration corresponding to 9.0 x 10(5) cells ml(-1) completely blocked cell divisions in embryos of the sea urchin Sphaerechinus granularis, whereas extracts from intact algal cells were only mildly cytotoxic. When the extracts from seawater culture medium were purified by RP-HPLC, cytotoxic activity towards S. granularis embryos was recovered in three consecutive fractions. Moreover, unfertilised eggs incubated in the active HPLC fractions became unproductive, whereas incubation of sperm gave a reduced fertilisation rate. This anti-proliferative effect was further characterized by immunofluorescence staining of sea urchin embryos. DNA labelling revealed that incubating sea urchin embryos in the purified algal extracts inhibited both pronuclei migration and fusion. Incorporation and detection of the DNA-base analogue 5-bromo-2-deoxyuridine showed that DNA-replication was blocked. Furthermore, staining of alpha-tubulin subunits demonstrated that embryonic tubulin organisation was altered. We conclude that P. pouchetii produce some anti-mitotic compound, and that senescent colonial cells to a great extent excrete this compound to their surroundings.
Hansen
Espen
E
Department of Aquatic BioSciences, NFH, University of Tromsø, Tromsø N-9037, Norway. espenh@nfh.uit.no
Eilertsen
Hans Chr
HC
Ernstsen
Arild
A
Genevière
Anne-Marie
AM
D000818:Animals; D002453:Cell Cycle / Q000187:drug effects*; D004625:Embryo, Nonmammalian / Q000187:drug effects*; D056890:Eukaryota; D008387:Marine Toxins / Q000494:pharmacology*; D008938:Mitosis / Q000187:drug effects; D009664:Norway; D010063:Ovum / Q000187:drug effects; D012617:Sea Urchins; D012623:Seawater
D008387:Marine Toxins