David U. Hernández-Becerril

Comparative molecular and morphological phylogenetic analyses of taxa in the Chaetocerotaceae (Bacillariophyta)

Kooistra W.H.F.C., Sarno D., Hernández-Becerril D.U., Assmy P., Di prisco C. and Montresor M. 2010. Comparative molecular and morphological phylogenetic analyses of taxa in the Chaetocerotaceae (Bacillariophyta). Phycologia 49: 471–500. DOI: 10.2216/09-59.1 The diatom family Chaetocerotaceae (Mediophyceae) includes two exclusively phytoplanktonic genera: Chaetoceros and Bacteriastrum. Its hallmark feature constitutes setae: hollow, spine-like appendages protruding from the valves. Chaetoceros is morphologically diverse, includes c. 400 described species and is common worldwide; whereas, Bacteriastrum includes only 11, is less common and occurs mainly in temperate and tropical seas. In the present study we gathered morphological information and/or sequence data from 86 strains belonging to 17 morphologically defined species in Chaetoceros and one in Bacteriastrum (B. cf. hyalinum). The Chaetoceros species included in this study belong to 14 of the 22 sections and two of the three subgenera: Chaetoceros (Phaeoceros) and Hyalochaete. A consensus cladogram reconstructed from states associated with morphological characters gathered from strains belonging to these 18 morphological taxa in the Chaetocerotaceae and Hemiaulus hauckii as outgroup resolved Bacteriastrum inside Chaetoceros and demonstrated monophyly for the subgenus Chaetoceros; whereas, the subgenus Hyalochaete was found to be paraphyletic. Molecular phylogenies inferred from the hypervariable region (D1–D4) of the LSU rRNA gene of all strains included in this study and from a subset of these strains corroborated the findings in the cladogram and showed evidence for cryptic or pseudocryptic diversity in C. curvisetus, C. debilis, C. diadema, C. lorenzianus, C. peruvianus and C. socialis. The molecular trees differed topologically from the morphological ones, but characters exhibiting only a few state changes in the molecular tree showed also only a few changes in the morphological one; whereas, characters showing multiple changes in the molecular tree revealed many changes in the morphological tree as well.

Toxic and harmful marine phytoplankton and microalgae (HABs) in Mexican Coasts.

Harmful Algal Blooms (HABs) are becoming an increasing problem to human health and environment (including effects on natural and cultured resources, tourism and ecosystems) all over the world. In Mexico a number of human fatalities and important economic losses have occurred in the last 30 years because of these events. There are about 70 species of planktonic and non-planktonic microalgae considered harmful in Mexican coasts. The most important toxin-producing species are the dinoflagellates Gymnodinium catenatum and Pyrodinium bahamense var. compressum, in the Mexican Pacific, and Karenia brevis in the Gulf of Mexico, and consequently the poisonings documented in Mexico are Paralytic Shellfish Poisoning (PSP) and Neurotoxic Shellfish Poisoning (NSP). Although there is evidence that Amnesic Shellfish Poisoning (ASP), Diarrhetic Shellfish Poisoning (DSP) and Ciguatera Fish Poisoning (CFP) also occur in Mexico, these problems are reported less frequently. The type of phytoplankton and epiphytic microalgae, their toxins and harmful effects as well as current methodology used to study these phenomena are presented in this paper. As an experienced group of workers, we include descriptions of monitoring and mitigation programs, our proposals for collaborative projects and perspectives on future research.

Raphidophyceans on the coasts of Mexico

The presence of ichthyotoxic phytoflagellates Chattonella marina, Fibrocapsa japonica, and Heterosigma akashiwo of the algal class Raphidophyceae are reported for first time in the Gulf of Mexico and the Pacific coast of Mexico. Phytoplankton were sampled to isolate and identify species, and to develop growth experiments in different media. We observed living material of the three species, but were unable to recognize specimens in preserved samples. Cultures were established by isolating single cells and diluting phytoplankton samples in modified f/2 and Erd–Schreiber media. Features, including morphological variations and pigment composition, of living cells under various nutrient conditions are described. These ichthyotoxic species produce harmful blooms in several parts of the world, although no documented cases have been reported in Mexico.

The genus Chaetoceros (Bacillariophyta) from Peter the Great Bay, Sea of Japan

Abstract Several studies in the Sea of Japan have dealt with the taxonomy, morphology and ecology of Chaetoceros species. In this study, a total of 33 Chaetoceros taxa was recorded between 1991 and 2004 from the phytoplankton of Peter the Great Bay, in the northwestern part of the Sea of Japan. This investigation was based on light and electron microscopy. Chaetoceros minimus is a new record for the Pacific Ocean, C. compressus var. hirtisetus is a new record for the seas of Russia, and C. socialis f. radians is a new record for the northwestern Sea of Japan. Diagnostic descriptions, illustrations and distribution are provided for all 33 Chaetoceros taxa from the study area.

Marine planktonic dinoflagellates of the order dinophysiales (Dinophyta) from coasts of the tropical Mexican Pacific, including two new species of the genus Amphisolenia

Despite a recent revision of the dinoflagellates of the order Dinophysiales on Mexican coasts and a checklist of dinoflagellates from the Mexican Pacific, many records still need to be confirmed, for there are very few reliable illustrations and/or descriptions. In this paper, species composition and distribution of dinoflagellates belonging to the Dinophysiales, the product of the analysis of net phytoplankton material collected from coasts of the tropical Mexican Pacific (Jalisco to Chiapas) are presented. The material has been studied using light microscopy, although a few species were also studied by scanning electron microscopy (SEM). Forty-one species from five genera were identified, with two new records annotated for the Mexican Pacific: Amphisolenia thrinax and Metaphalacroma skogsbergii , and two new species of the genus Amphisolenia , Amphisolenia fusiformis sp. nov. and Amphisolenia michoacana sp. nov. Illustrations, dimensions and distribution data are provided for each species, and descriptions of the new species are also given. Amphisolenia palmata , A. rectangulata , A. truncata , Dinophysis apicata , D. hindmarchii , Histioneis biremis , H. crateriformis , H. pulchra , Ornithocercus cristatus , O. heteroporoides and O. orbiculatus are illustrated for the first time in the waters of the Mexican Pacific. The number of species found in this study is relatively low. The species Dinophysis norvegica and D. sacculus , reported in previous papers, do not seem to occur in Mexican waters, as their distribution is rather limited to the Mediterranean Sea and the North Atlantic, respectively. Finally, the identity of certain species of Dinophysis and the nature of the new species described here are discussed.

Marine diatoms from Buenos Aires coastal waters (Argentina). V. Species of the genus Chaetoceros

El genero Chaetoceros es un componente importante del plancton marino, de amplia distribucion mundial en terminos de diversidad y biomasa. El presente trabajo esta abocado a la morfologia, taxonomia y distribucion de las especies pertenecientes al genero Chaetoceros encontradas en aguas costeras marinas de la Provincia de Buenos Aires, Argentina. Las muestras fitoplanctonicas fueron recolectadas desde noviembre de 1994 hasta septiembre de 2000 en siete estaciones ubicadas a lo largo de la costa bonaerense entre los paralelos 36o20� y 37°20� S. El material fue estudiado con microscopia optica y electronica de barrido. Veinte taxa fueron encontrados, identificados, descriptos, ilustrados y comparados con los taxa mas allegados. Tres de esos taxa pertenecen al subgenero Chaetoceros (= Phaeoceros) y los restantes diecisiete pertenecen al subgenero Hyalochaete. Chaetoceros filiferus y C. compressus var. hirtisetus son reportados por primera vez para el Oceano Atlantico sudoccidental. C. danicus, C. debilis, C. lorenzianus y C. socialis, mencionadas como especies nocivas en otras areas geograficas, no fueron asociados a eventos nocivos en el area de estudio durante este periodo.

PARMALES (CHRYSOPHYCEAE) FROM THE GULF OF TEHUANTEPEC, MEXICO, INCLUDING THE DESCRIPTION OF A NEW SPECIES, TETRAPARMA INSECTA SP. NOV., AND A PROPOSAL TO THE TAXONOMY OF THE GROUP1

There are few studies dedicated to species of the Order Parmales all over the world. All 12 taxa described are part of the marine ultraplankton (less than 5 μm). Analysis of filtered samples from the Gulf of Tehuantepec yielded specimens of two taxa of the group. One is a new species, belonging to the genus Tetraparma. Tetraparma insecta sp. nov. is solitary and spherical (2.8–3.8 μm diameter), and all plates lack ornamentations or knobs, the walls are smooth, and only the plate junctions are seen. The shield plates are convex and show a conspicuous rim, some of them with an indentation. This species shows superficial similarities with Tetraparma pelagica, the other species described of the genus, and is very similar to siliceous forms, previously found, with no formal name. The other species is the taxon Triparma laevis form mexicana (Kosman) stat. nov., earlier described for Mexican waters, which has an irregular ala, the shield plates have knobs at the center, the triradiate plates show a “Y”‐shaped keel, and the walls of plates and ala show minute granules. Tetraparma insecta was distributed widely in the study area and was relatively abundant, reaching a density of 4 × 104·L−1, with an evident preference for subsurface waters (10–20 m depth), whereas T. laevis form mexicana was rare and scarce. Both species seem to be restricted to tropical–subtropical waters. We discuss the taxonomy of Parmales, especially concerning the category of subspecies within the group. Parmales is a widespread group in cold and tropical waters.

PLANKTONIC DIATOMS FROM THE GULF OF CALIFORNIA AND COASTS OFF BAJA CALIFORNIA: THE GENERA RHIZOSOLENIA, PROBOSCIA, PSEUDOSOLENIA, AND FORMER RHIZOSOLENIA SPECIES

Net plankton samples from the Gulf of California and coasts off Baja California were analyzed for species of Rhizosolenia, Proboscia and Pseudosolenia, as well as other species of “Rhizosolenia” which do not belong to the genus. Twenty taxa were found: 18 species, one variety and one form. These are briefly described and illustrated by light and electron (both scanning and transmission) microscopy. A new taxonomie combination, Proboscia indica (H. Peragallo) Hernandez-Becerril, is proposed. New morphological observations include a large pore open to the outside at the tip of the proboscis and the absence of spinulae. Details of a structure analogous to the contiguous area of typical Rhizosolenia species are given for “Rhizosolenia” pungens; this structure develops as part of the valvocopula rather than the valve. Four new records for the Gulf of California are reported: Rhizosolenia clevei var. communis, Rhizosolenia debyana, “Rhizosolenia” crassispina, and “Rhizosolenia” pungens. The most widely distribu...

New records of planktonic dinoflagellates (Dinophyceae) from the Mexican Pacific Ocean

Abstract Phytoplankton samples were taken during several oceanographic cruises in the Mexican Pacific Ocean (1998–2000), following three different protocols of collection and analysis, and from the material we report six new records of planktonic dinoflagellates in the region. Two species, Asterodinium spinosum and Brachydinium capitatum, are unarmored, another species, Actiniscus pentasterias, has internal siliceous skeletons, whereas Thoracosphaera heimii usually develops a calcareous coccoid vegetative stage. Calciodinellum operosum produces calcareous cysts that were also found in this study, and Achradina pulchra has an internal skeleton of organic material. Three species, A. spinosum, B. capitatum and C. operosum, were represented by very few specimens, whereas all others were more frequent. Brief descriptions and illustrations of these species by light and scanning electron microscopy are provided. The methods and techniques to study this group have been diverse and useful in finding a greater diversity. The world distribution of the species recorded here is revised.

MORPHOLOGICAL VARIABILITY AND LIFE CYCLE TRAITS OF THE TYPE SPECIES OF THE DIATOM GENUS CHAETOCEROS, C. DICHAETA(1).

Chaetoceros dichaeta Ehrenb. is the type species of the genus Chaetoceros and is one of the dominant planktonic diatom species of the Southern Ocean. A number of varieties and forms have been described for C. dichaeta, which prompted us to investigate the morphological variability in clonal cultures to achieve a better circumscription of the morphological features of this species. We studied eight clonal cultures obtained from the type locality by sequencing the D1‐D3 hypervariable domains of the LSU to assess their genetic identity, following cell‐size reduction and sexual reproduction, and examining the morphological features of cells at different stages of the size reduction process using both LM and EM. Observation of sexual reproduction within clonal strains demonstrated that C. dichaeta is homothallic. The size and morphology of the cells vary considerably during size reduction: cell volume is reduced by over an order of magnitude, and the gradual diminution of the apical axis is accompanied by the elongation of the pervalvar axis. All forms and varieties described for C. dichaeta can be ascribed to the species, with the exception of C. dichaeta f. tenuiformis L. Mangin.