The occurrence of the dinoflagellates belonging to the ciguatera-related genus Gambierdiscus is reported for the first time from the north-western Arabian Gulf and northern Red Sea in the Indian Ocean basin. Gambierdiscus yasumotoi was recorded from two sampling sites on the southern Kuwait coast, and co-occurrence of G. cf. belizeanus and G. yasumotoi was found also in the Gulf of Aqaba in Jordan. The morphology of cells is described on the basis of light microscopy and scanning electron microscopy examination.

The occurrence of noctilucoid dinoflagellates Abedinium dasypus and Scaphodinium mirabile is reported for the first time from the Indian Ocean (Kuwait's waters, north-western Arabian Gulf). The morphology of live cells is described on the basis of light microscopic examination and photographically documented for both species. The world distribution of these dinoflagellates is reviewed.

The occurrence of the dinoflagellate Kryptoperidinium foliaceum is reported for the first time from a hypersaline environment in Kuwait based on recurrent observations of this species from a tidal creek in appreciable numbers. This new record extends the known range of salinity tolerance for K. foliaceum to more than 100 psu. The distribution of the species along a salinity gradient within the tidal creek was studied. The morphological features of the species on the basis of light and epifluorescence microscopy observations are described.

Several experiments using a self-regulated system were conducted to define the factors likely to influence the uptake of paralytic shellfish poison (PSP) by oysters in the Penzé estuary (France, Brittany). Each 4-day experiment was carried out in a recirculated sea water system using 15 Pacific oysters (Crassostrea gigas) separated from each other and supplied with unfiltered natural seawater containing alternatively toxic (Alexandrium minutum) or non-toxic (Skeletonema costatum) algal diets. The food supply and exposure times to toxic diets were determined according to field studies of the upstream and downstream movement of patches containing A. minutum. The experimental parameters corresponded roughly to the hydrological conditions generally observed in June when tidal coefficients are lowest and blooms occur: (i) A. minutum concentrations in sea water of 200, 5000 and 10 000 cell ml−1; (ii) inorganic matter consisting of 5 and 15 mg L−1 of calcinated muddy sediments; and (iii) low and high tide salinities of 25 and 35‰, respectively. Significant experimental contamination (greater than the 80 µg STX equiv. 100 g-1 sanitary threshold) occurred after 4 days of exposure for the monospecific A. minutum diet (20-200 cell ml−1) and alternated A. minutum and S. costatum diets (5000 and 20 000 cell ml−1, respectively). Contamination levels were less than the sanitary threshold for alternated A. minutum/S. costatum diets of 200 and 20 000 cell ml−1, respectively, and for a monospecific A. minutum diet (1000−10 000 cell ml−1). In the last case, the accumulation rate was quite low, possibly because of inhibition of the filtration rate related to a lower biodeposit production rate and decreased feeding time activity. The addition of inorganic matter appeared to play a significant role in the observed increase of toxin uptake, whereas salinity was not a determining factor for toxin accumulation rates. These last observations were corroborated by statistical analysis and stepwise multiple linear regressions integrating all or some of the experimental parameters.

Seventeen species of the mainly sand-dwelling genus Amphidinium are reported from south-eastern Australian waters. Three new species are described: A. boggayum, A. mootonorum and A. yuroogurrum. Additional features from previously described species are presented, including non-motile cell stages. Nine of these species are new records for Australia; however, these species are probably widespread and common. Two potentially ichthyotoxic species of Amphidinium were commonly found: A. carterae and A. cf. operculatum. A table of morphological characters is compiled as a step towards recognizing new characters with which to group species of this presently artificially defined unarmoured dinoflagellate genus.

A new benthic marine dinoflagellate, Bysmatrum granulosum Ten-Hage, Turquet, Quod & Couté, sp. nov., was obtained from sediment and coral samples from sites of La Réunion Island (SW Indian Ocean). This new species is described and illustrated by light and scanning electron micrographs. Cells are 40–50 μm long and 40–46 μm wide. The epitheca is conical and smaller than the hypotheca, which is trapezoidal with convex sides. Plate tabulation is typical for the genus (P0, X, 4′, 3a, 7′′, 6c, 5s, 5′′′, 2′′′′); epithecal plates 3′ and 4′′ separate the intercalary plates 2a and 3a. Thecal plates are perforated by pores and covered by both small and minute wart-like projections, linearly arranged, radiating from the apical pore. This new species differs from the three others of the genus Bysmatrum in the following characters: cell shape and size, size of the apical pore complex and features of thecal plates (plate shapes and ornamentations).

The identity of Dinophysis sacculus Stein has proved to be problematic in recent years, during which this species has been associated with diarrhoetic shellfish poisoning (DSP) events along European coasts. To complement the scarce and at times contradictory existing information, we provide details of morphological variation in D. sacculus throughout its geographical range, which includes the Mediterranean Sea and European Atlantic coasts. Our data clarify its relationship with D. pavillardii Schröder. This species differs from D. sacculus only by the presence of a concavity along the dorsal margin, but transitional morphotypes are frequent in almost all the samples examined. We therefore propose merging the two species and classifying morphotypes with a dorsal concavity as D. sacculus f. reniformis (Pavillard) comb. nov. Despite the high variability of Dinophysis sacculus, it was generally possible to separate it from D. acuminata Claparède & Lachmann. The only character distinguishing the two species is the shape of the large hypothecal plates, which in D. sacculus are elongate, almost rectangular or sac-like, whereas in D. acuminata they are shorter, more convex dorsally and often more slender towards the antapex. Thecal areolation and sulcal list ornamentation are more pronounced in D. acuminata, although these characters are somewhat variable. Other thecal details, such as the shape of sulcal platelets and the structure of the apical pore area, were not useful for circumscription of the two taxa. In a few samples from the Galician Rias and from the Spanish Mediterranean coast, we observed morphotypes intermediate between D. sacculus and D. acuminata, which indicates that the two species can have slightly overlapping ranges of variability.