Typification for reliable application of subspecific names within Peridinium cinctum (Peridiniales, Dinophyceae)

The application of scientific names is determined by means of nomenclatural types, and every name has to be typified properly. The concept has limitations for unicellular organisms, because original material frequently consists of drawings and/or inadequately preserved physical material. Peridinium cinctum is an abundant freshwater microalga and variable in both morphology and genotype. Morphological variation is mainly expressed in its epithecal conformation: shape deviations of plates, plate rearrangements, plate fusion and plate additions. Different epithecal conformations were traditionally described as either varieties of P. cinctum or were established as closely related species. Despite this, relations between varieties, ribotypes and geographic locations were oversighted, and the full spectrum of plate variation in P. cinctum is still not well represented. For this reason, we sampled localities in Germany and Poland, from which varieties of P. cinctum were described a century ago. We cultivated monoclonal strains, exhibiting two distinct ITS ribotypes, and assessed their epithecal variation of morphology. Based on ca 2,500 observations of individual cells we report a plethora of both plate and suture deviations from the archetypical epithecal conformation of P. cinctum. Morphologies corresponding to previously described varieties were rare, even at their type localities. Nevertheless, we found morphologies consistent with protologues in four cases and use this material for epitypification. These varieties are now linked to specific DNA sequences, allowing reliable application of scientific names for future studies.

Biotic and Abiotic Factors Affecting the Population Dynamics of Ceratium hirundinella, Peridinium cinctum, and Peridiniopsis elpatiewskyi

The present research was conducted to assess the impact of abiotic and biotic factors on the growth of freshwater dinoflagellates such as Ceratium hirundinella, Peridinium cinctum, and Peridiniopsis elpatiewskyi, which reduce the quality of drinking water in the Zayandeh Rud Reservoir. To this end, 152 algal and zoological samples were collected from the reservoir located in the Central part of Iran in January, April, July, and October 2011. Abiotic factors such as pH, temperature, conductivity, transparency, dissolved oxygen, and nutrient concentration of the water were measured in all study stations. The results showed that the population dynamics of dinoflagellates in the Zayandeh Rud Reservoir was different depending on season, station, and depth. The findings proved that C. hirundinella was one of the dominant autumn planktons in the highest biovolume in the Zayandeh Rud Reservoir. While P. elpatiewskyi was present in the reservoir throughout a year with biovolume peak in summer. Accompanying bloom of P. elpatiewskyi and C. hirundinella, P. cinctum also grew in well-heated summer and autumn waters. It was further found that Ceratium density was positively correlated with sulfate ion concentrations, while the growth of P. cinctum and P. elpatiewskyi were associated, first and foremost, with NO2− and Mn.

MICROALGAE IN THE DIET OF EUCYPRIS MAREOTICA (CRUSTACEA, OSTRACODA) IN THE HYPERSALINE LAKE CHERSONESSKOYE (CRIMEA)

In the Crimea, there are many hypersaline lakes and lagoons, where Eucypris mareotica (Ostracoda), high halotolerant species, inhabit. Despite the wide distribution of the species and the abundance of its populations, little is known about the biology of E. mareotica, including its nutrition. Diversity of microalgae in gut of E. mareotica in Lake Chersonesskoye was studied. The crustaceans ate both phytoplankton and alga, which growth on cladophora filaments, as well as various small animals, but microalgae played a main role in their nutrition. The proportion of individuals, which had algae in intestines, ranged in a sample from 0 to 93%. In 335 analyzed individuals, 22 species of microalgae were found, which belong to 4 types, 4 classes and 11 orders. Of these, 4 species belong to the type Cyanobacteria, 3 – to Myzozoa, 4 – to Haptophyta, 11 – to Ochrophyta. The most common species was Peridinium cinctum. Given the availability of a wide variety of consumed microalgae, ostracod gut content analysis can be used to assess species diversity of microalgae in the lakes.

Description of Peridiniopsidaceae, fam. nov. (Peridiniales, Dinophyceae)

The vast majority not only of dinophytes, but also of Peridiniales, live in the marine environment, and some 350 (out of ca 2.500) species are present in freshwater habitats (Mertens et al. 2012). Many freshwater Peridiniales constitute small and only distantly related species groups embedded in predominantly marine clades (e.g., Apocalathium, Chimonodinium, Naiadinium in the Thoracosphaeraceae; species assigned to “Peridiniopsis” in the Kryptoperidiniaceae; Zhang et al. 2011b, Gottschling & Söhner 2013, Annenkova et al. 2015; Fig. 1). However, the most distinguished freshwater group of the Peridiniales are the Peridiniaceae including the type species, Peridinium cinctum, and other frequently encountered species such as Peridinium bipes, Peridinium volzii and Peridinium willei.

Potentialités phagotrophes des phytoflagellés dans la retenue de barrage Allal El Fassi (Maroc)

L'abondance des communautés bactériennes et phytoplanctoniques et l'activité bactérivore des phytoflagellés ont été mesurées à différentes profondeurs de mars à décembre 1998, dans une retenue de barrage (Allal El Fassi, Maroc). L'abondance des communautés bactériennes, essentiellement constituées de cellules libres de forme sphérique, a fluctué de 1,0 à 9,8·106 cellules·mL-1. À toutes les profondeurs, les plus fortes valeurs ont été mesurées au printemps, avec la mise en place de la stratification thermique et le développement de la diatomée centrique Cyclotella oceallata. Le nombre de bactéries baisse de manière notable en été et augmente légèrement au cours de l'automne, alors que deux Chrysophycées (Dinobryon sertularia et D. cylindricum) dominaient la communauté algale, accompagnées de deux Dinophycées (Peridinium cinctum et Ceratium hirundinella) et d'une Cryptophycée (Cryptomonas ovata). À l'aide d'expériences de broutage utilisant un traceur bactérien, nous avons pu mesurer une activité bactérivore chez les cinq espèces d'algues citées. L'impact de la prédation de l'ensemble de cette communauté de phytoflagellés mixotrophes a varié de 1,2 à 357·104·bactéries·L-1 ·h-1, 81 % de cet impact étant lié à l'activité des deux Chrysophycées, contre seulement 12 % pour les deux Dinophycées et 7 % pour la Cryptophycée. L'ensemble des résultats acquis au cours de cette étude laissent donc supposer que le rôle des phytoflagellés mixotrophes est essentiel dans le fonctionnement du réseau trophique microbien du réservoir Allal El Fassi, notamment dans la régulation des peuplements bactériens se développant en automne.

Impact du zooplancton métazoaire sur le phytoplancton et les protozoaires ciliés dans le réservoir Sahela (Maroc)

L'impact du zooplancton métazoaire sur le phytoplancton et les protozoaires ciliés a été mesuré durant la période de juillet à décembre 1999 dans le réservoir Sahela sous climat méditerranéen semi-aride. Les expériences ont été réalisées à l'aide de chambres de diffusion immergées in situ pendant 7 heures en absence (chambres témoins) et en présence (chambres expérimentales) du zooplancton. Les résultats indiquent que la mortalité moyenne à 4 m des algues est de 0,13 + 0,03 h-1, et celle des protozoaires ciliés de 0,07 + 0,03 h-1. Cryptomonas ovata et Halteria grandinella ont subi la plus forte prédation, respectivement, 0,31 + 0,14 h-1 et 0,11 + 0,04 h-1 à 4 m. Toutefois, les algues de grande taille (Pediastrum sp, Ceratium hirundinella et Peridinium cinctum) n'ont été que très peu ou pas consommées.