| Abstract: | Dinoflagellates of the genus Dinophysis are agents of Diarrhetic Shellfish Poisoning (DSP). They occur along the French coast and affect shellfish exploitation during most of the year (during spring, summer and autumn). Because this species is difficult to cultivate, very little is known about this organism. The first problem is the species‐delineation within this genus which is sometimes unclear based upon the solely on morphological features, in particular for the complex D. acuminata (D. cf. acuminata,, D. cf. norvegica, D. cf.sacculus, and D. skagii) or the complex D. sacculus (D. sacculus and D. pavillardii). The second problem is its detection in natural samples. French Dinophysis blooms have been reported to be toxic under 100 cells L?1, a concentration which corresponds to less than 1 cell 10‐mL?1, as determined by the Utermöhl method of enumeration. Molecular tools may help to resolve these two kind of problems. During one year (spring 1999 to spring 2000), more than 100 fixed samples containing Dinophysis spp. cells were collected along the French coast by the French monitoring network (or REPHY; http://www. ifremer.fr). The genetic diversity of Dinophysis spp. was studied by sequencing and analysis of ribosomal DNA genes. We found that sequences were hightly conserved between species or within the D. acuminata or D. sacculus complex. Two oligonucleotide probes, specific to these complex groups, were designed. Their specificity and sensitivity are actually tested on natural samples by a PCR‐based assay. Furthur investigation will include the development of standard molecular diagnostics due to their rapid and sensitive detection in natural samples. |
