António J. Calado

PHAGOTROPHIC MECHANISMS AND PREY SELECTION IN FREE-LIVING DINOFLAGELLATES

Three types of feeding mechanisms are known in dinoflagellates: pallium feeding, tube feeding, and direct engulfment. Pallium feeding has only been described for heterotrophic thecate species (Protoperidinium, Diplopsalis group). Tube feeding is commonly found among both naked and thecate species of mixotrophic and heterotrophic dinoflagellates (e.g. Amphidinium, Dinophysis, Gyrodinium, Peridiniopsis). Direct engulfment is mainly found among naked species (e.g. Gymnodinium, Gyrodinium, Noctiluca): recently, however, some thecate species have been shown to use this feeding mechanism as well. Feeding behavior in dinoflagellates involves several steps prior to actual ingestion, including precapture, capture, and prey manipulation. As feeding mechanisms allow the ingestion of relatively large prey or parts thereof, dinoflagellates are regarded as raptorial feeders. While prey size plays an important role in the ability of dinoflagellates to ingest food, this alone cannot explain observed prey preferences. Some dinoflagellate species can be very selective in their choice of prey, while others show a remarkable versatility.

Diatoms and macroinvertebrates provide consistent and complementary information on environmental quality

Predictive models based on invertebrate assemblages are a powerful tool for assessing water quality. Yet, few attempts have been made to build predictive models with diatoms although they are widely used in freshwater assessment and are among the mandatory biological monitoring elements indicated in the European Water Framework Directive. We built two predictive models for central Portugal, one for macroinvertebrates and the other for diatoms, using data sampled simultaneously from 43 sites in the Spring of 2004 and 2005. Our objective was to test the performance of models based on the diatom community and compare the assessments made by the two indicator communities for the same sites. Each model was tested with 17 sites. Both models showed good performance in predicting reference sites to the correct group: 76 % for the macroinvertebrate model using the discriminant variables longitude, distance to source, alkalinity, depth, number of riffles and channel substrate diversity; 85 % for the diatoms model using latitude, runoff, mineralization, distance to source, slope, discharge and hardness. The water quality assessments of test sites produced by the two models were similar in 76 % of the cases. According to the predictive models, invertebrates were more sensitive to morphological alterations of the channel and habitat conditions (presence of dams and artificial walls, destruction of riparian corridor) while diatoms were more sensitive to changes in water chemistry. Moreover, in lowland streams, where the habitat and substrate heterogeneity are naturally low, assessment by diatoms was more useful than evaluations using invertebrates. We concluded that invertebrates and algae provide consistent and in some cases complementary information on environmental quality and recommend their simultaneous use for bioassessment.

Diversity and abundance of potentially toxic Pseudo-nitzschia peragallo in Aveiro coastal lagoon, Portugal and description of a new variety, P. pungens var. aveirensis var. nov.

The syndrome Amnesic Shellfish Poisoning (ASP) results from ingesting sea food contaminated by a neurotoxin, domoic acid. Diatoms of the genera Pseudo-nitzschia and Nitzschia are responsible for the production of this toxin. A total of eleven species of Pseudo-nitzschia were identified during two plankton surveys at the entrance and in the southern channels of Ria de Aveiro, the largest lagoon on the west coast of Portugal. During the first survey, conducted from February to October 2000, the following species were identified: P. australis, P. cuspidata, P. delicatissima, P. dolorosa, P. fraudulenta, P. pseudodelicatissima, P. subpacifica and a new variety of P. pungens. The second survey took place from September 2003 to April 2004, except for a break between December 2003-January 2004, along with one complementary sample taken in October 2004; it revealed three additional species, P. americana, P. calliantha and P. multistriata. In contrast, P. cuspidata, P. dolorosa and P. subpacifica were not found during the second survey. Five species: P. subpacifica, P. americana, P. calliantha, P. multistriata and P. cuspidata were reported for the first time in Portuguese waters. Overall, P. australis, P. pseudodelicatissima and a new variety of P. pungens were the most common species, the latter being present in all samples except October 2000. The highest concentrations of Pseudo-nitzschia cells registered were 90, 000 cells L–1 in August 2000 and 106, 000 cells L−1 in March 2004, with P. australis accounting for 65–75% of the cells. Cell concentrations were highest near the entrance of the lagoon and decreased along with salinity in the channels. Cultures of P. australis, P. americana, P. fraudulenta, P. multistriata and a new variety of P. pungens were established and tested for the production of domoic acid, but the results were negative. Morphological differences were found between our strains of P. pungens and two other previously described varieties of P. pungens regarding valve width, densities of striae, fibulae, poroids and band striae as well as differences in the morphology of the band striae. These differences were supported by phylogenetic analyses of ITS rDNA sequences, existence of a compensatory base change and mating studies indicate the presence of a separate taxon, which was described as a new variety, P. pungens var. aveirensis var. nov.

Taxonomy and ultrastructure of a freshwater, heterotrophic Amphidinium (Dinophyceae) that feeds on unicellular protists

Amphidinium lacustre Stein, non sensu auctt. was identified by reference to original descriptions, which differ significantly from later interpretations. Mixed cultures containing A. lacustre, cryptomonads, Spermatozopsis exsultans Korshikov, and small chlorelloid cells were examined for feeding events. The dinoflagellate ingested the cytoplasm of cryptomonads, leaving the periplast, and completely ingested Spermatozopsis and chlorelloid cells. A peduncle was used in the initial stages of prey capture, although it was not visible during food uptake. The ultrastructure of A. lacustre was typical of unarmored dinoflagellates. A single pusule per cell, consisting of one long, convoluted tube, opened directly into one of the flagellar canals. An eyespot was present, composed of presumably crystalline, vesicle‐contained units, similar to those of Gymnodinium natalense Horiguchi et Pienaar. The main components of the flagellar apparatus resembled those of other Amphidinium species, but differences were noted. The transverse basal body overlapped the proximal end of the longitudinal one at an angle of about 120°. Three connectives were distinguished between basal bodies, one of which consisted of radiating fibers linking individual triplets of the longitudinal basal body to one triplet of the transverse. Some flagellar apparatus components were closely associated to a vesicle and to a mitochondrion. A ventral ridge extended from the (incomplete) longitudinal striated collar to the peduncular striated collar. The peduncle was supported by a single strand of microtubules, which were surrounded by numerous vesicles with electron‐opaque contents.

On the freshwater dinoflagellates presently included in the genus Amphidinium, with a description of Prosoaulax gen. nov

A.J. Calado and Ø. Moestrup. 2005. On the freshwater dinoflagellates presently included in the genus Amphidinium, with a description of Prosoaulax gen. nov. Phycologia 44: 112–119. Amphidinium is a genus of naked dinoflagellates, characterized by a small epicone and a larger hypocone. Presently about 120 species from both freshwater and marine biotopes have been described. The genus has long been known to be poly-phyletic, however, and the recent rediscovery of the type species has now allowed for more precise definition of the genus. The new circumscription of the genus leaves the freshwater species without a generic name. A new generic name, Prosoaulax gen. nov., is therefore proposed for the first described freshwater species, Amphidinium lacustre Stein (1883), and related species. Based on ultrastructural features, notably the very unusual type of eyespot, Prosoaulax is considered to be related to a recently recognized, but poorly understood group of dinoflagellates, comprising the marine species Gymnodinium simplex, G. natalense, Polarella antarctica, and some symbionts of marine invertebrates, G. bei and G. linucheae. It also includes the symbionts of corals (‘zooxanthellae’) belonging to the genus Symbiodinium, a genus believed to contain the modern representatives of the Suessiales, an order of dinoflagellates extending back into the Mesozoic.

DESCRIPTION OF TYRANNODINIUM GEN. NOV., A FRESHWATER DINOFLAGELLATE CLOSELY RELATED TO THE MARINE PFIESTERIA-LIKE SPECIES 1

On the basis of morphological (light and electron microscopy) as well molecular data, we show that the widely distributed freshwater dinoflagellate presently known as Peridiniopsis berolinensis is a member of the family Pfiesteriaceae, an otherwise marine and estuarine family of dinoflagellates. P. berolinensis is a close relative of the marine species, which it resembles in morphology, mode of swimming, food‐uptake mechanism, and partial LSU rRNA sequences. It differs from all known genera of the family in plate tabulation. P. berolinensis is only distantly related to the type species of Peridiniopsis, P. borgei, and is therefore transferred to the new genus Tyrannodinium as T. berolinense comb. nov. T. berolinense is a very common freshwater flagellate that feeds vigorously on other protists and is able to consume injured metazoans much larger than itself. Production of toxins has not been reported.

ULTRASTRUCTURE AND LSU RDNA‐BASED PHYLOGENY OF ESOPTRODINIUM GEMMA (DINOPHYCEAE), WITH NOTES ON FEEDING BEHAVIOR AND THE DESCRIPTION OF THE FLAGELLAR BASE AREA OF A PLANOZYGOTE1

A small, freshwater dinoflagellate with an incomplete cingulum, identified as Esoptrodinium gemma Javornický (=Bernardinium bernardinense sensu auctt. non sensu Chodat), was maintained in mixed culture and examined using light and serial section TEM. Vegetative flagellate cells, large cells with two longitudinal flagella (planozygotes), and cysts were examined. The cells displayed a red eyespot near the base of the longitudinal flagellum, made of two or three layers of pigment globules not bounded by a membrane. Yellow‐green, band‐shaped chloroplasts, bounded by three membranes and containing lamella with three thylakoids, were present in both flagellate cells and cysts. Most cells had food vacuoles, containing phagotrophically ingested chlamydomonads or chlorelloid green algae; ingestion occurred through the ventral area, involving a thin pseudopod apparently driven by the peduncle. The pusule was tubular, with numerous diverticula in its distal portion, and opened into the longitudinal flagellar canal. Three roots were associated with each pair of flagellar bases, both in vegetative cells and in a planozygote. The longitudinal microtubular root bifurcated around the longitudinal basal body. The planozygote contained a single peduncle and associated structures, and a single transverse flagellar canal with the two converging transverse flagella. Using two ciliates as outgroup species, phylogenetic analyses based on maximum parsimony, neighbor‐joining and posterior probability (Bayesian analysis) supported a clade comprising Esoptrodinium, Tovellia, and Jadwigia.

Architecture of the flagellar apparatus and related structures in the type species of Peridinium, P. cinctum (Dinophyceae)

The ultrastructure of Peridinium cinctum, was examined by serial sectioning with particular emphasis on the detailed construction of the flagellar apparatus. The pusular system of P. cinctum included two sac pusules in open connection with the flagellar canals; disorganized material was found inside the pusules and near the flagellar pores, indicating excretory activity of the pusules. Several cells had replicated basal bodies, which were oriented toward the cell apex. The functional basal bodies formed an angle of about 65° and were linked by a layered connective, a structure so far seen only in peridinioids. A transverse microtubular root looped around the transverse flagellar canal and nucleated several rows of microtubular extensions that lined most of the transverse sac pusule. A single-stranded root was associated with the surface of the longitudinal basal body almost at a right angle to the basal body triplets. A fibrous connective between the transverse striated root and the longitudinal microtubu...

On the identity of the freshwater dinoflagellate Glenodinium edax, with a discussion on the genera Tyrannodinium and Katodinium, and the description of Opisthoaulax gen. nov.

Calado A.J. 2011. On the identity of the freshwater dinoflagellate Glenodinium edax, with a discussion on the genera Tyrannodinium and Katodinium, and the description of Opisthoaulax gen. nov. Phycologia 50: 641–649. DOI: 10.2216/11-21.1 Within the context of the preparation of a flora for the identification of freshwater dinoflagellates, the identity of Glenodinium edax and the affinities of a group of phagotrophic species with a conspicuous eyespot not associated with plastids (eyespot type C) currently classified in Katodinium were re-evaluated. The original description and illustrations of the phagotrophic G. edax suggest affinity with the Pfiesteriaceae. Whereas the tabulation currently associated with G. edax is based on a probable misidentification, the similarity to Tyrannodinium berolinense suggests that the two names can be regarded as synonyms and T. edax comb. nov. is proposed. As presented in modern floras, Katodinium is artificially defined on the basis of the position of the cingulum at or below the posterior third of the cell, and includes widely different forms. The presence of an eyespot of type C in the phagotrophic Katodinium vorticella and related species combines with a general cell morphology reminiscent of Esoptrodinium gemma and the formation of Tovellia-like cysts to mark this group of species as belonging to the Tovelliaceae. The type species of Katodinium, K. nieuportense, is morphologically quite different from these species and does not display tovelliacean characters. None of the known genera of Tovelliaceae matches the characters of K. vorticella and its close relatives. Opisthoaulax gen. nov. is described and new combinations are proposed for K. vorticella and six other species.

ULTRASTRUCTURE AND LSU rDNA–BASED REVISION OF PERIDINIUM GROUP PALATINUM (DINOPHYCEAE) WITH THE DESCRIPTION OF PALATINUS GEN. NOV.1

The name Peridinium palatinum Lauterborn currently designates a freshwater peridinioid with 13 epithecal and six cingular plates, and no apical pore complex. Freshwater dinoflagellate floras classify it in Peridinium group palatinum together with P. pseudolaeve M. Lefèvre. General ultrastructure, flagellar apparatus, and pusular components of P. palatinum were examined by serial section TEM and compared to P. cinctum (O. F. Müll.) Ehrenb. and Peridiniopsis borgei Lemmerm., respectively, types of Peridinium and Peridiniopsis. Partial LSU rDNA sequences from P. palatinum, P. pseudolaeve and several peridinioids, woloszynskioids, gymnodinioids, and other dinoflagellates were used for a phylogenetic analysis. General morphology and tabulation of taxa in group palatinum were characterized by SEM. Differences in plate numbers, affecting both the epitheca and the cingulum, combine with differences in plate ornamentation and a suite of internal cell features to suggest a generic‐level distinction between Peridinium group palatinum and typical Peridinium. The branching pattern of the phylogenetic tree is compatible with this conclusion, although with low support from bootstrap values and posterior probabilities, as are sequence divergences estimated between species in group palatinum, and typical Peridinium and Peridiniopsis. Palatinus nov. gen. is proposed with the new combinations Palatinus apiculatus nov. comb. (type species; syn. Peridinium palatinum), P. apiculatus var. laevis nov. comb., and P. pseudolaevis nov. comb. Distinctive characters for Palatinus include a smooth or slightly granulate, but not areolate, plate surface, a large central pyrenoid penetrated by cytoplasmic channels and radiating into chloroplast lobes, and the presence of a peduncle‐homologous microtubular strand. Palatinus cells exit the theca through the antapical‐postcingular area.