Diatomeas de las lagunas de Unare y Píritu, estado Anzoategui Venezuela: subclases thalassiosirophycidae y coscinodiscophycidae round & crawford / Diatoms from unare and piritu lagoons, Anzoayegui state Venezuela: subclasses thalassiosirophycidae and coscinodiscophycidae round & crawford

Se describen 9 especies de diatomeas (Bacillariophyta) pertenecientes a las Subclase Thalassiosirophycidae y Coscinodiscophycidae. Las muestras de agua de las lagunas de Unare y Píritu (Venezuela) fueron colectadas entre Noviembre 1988 y Julio 1989. Los especimenes fijados con formol neutralizado y montados con Bálsamo de Canadá, se examinaron mediante microscopia de contraste de fase. Las especies estudiadas fueron: Thalassiosira eccentrica (Ehrenberg) Lange et al., T. leptopus (Grun) Hasle & Fryxell, Cyclotella menenghianiana (Kützing) Wood, C. striata (Kützing) Grunow in Cleve et Grunow, Coscinodiscus asteromphallus (Ehrenberg) Makarova, C. janischi (Schmidt) Wood, C. marginatus (Ehrenberg) Navarro, C. subtilis (Ehrenberg) var. normanii (Gregory) Van Heurck, Actinocyclus octonarius (Ehrenberg) Navarro.

Biovolumen de algunas diatomeas céntricas de la plataforma nororiental de Venezuela / Biovolume of some centric diatoms from the northeastern continental shelf of Venezuela

Biovolume variation of twelve centric diatom species from eight natural habitats of the northeastem continental shelf of Venezuela were analyzed. Also, the morphometric variable that exerts the greatest influence on the biovolume was determined. Samples were collected with a net (mesh 36 microns), or with a Niskin bottle (5 l) and fixed with neutralized formaldehyde (4 per cent). Water temperature and salinity were measured. The species studied were: Detonula sp., Skeletonema costatum, Lauderia annulata, Pseudoguinardia recta, Cerataulina pelagica, Helicotheca tamesis, Rhizosolenia styliformis, Proboscia alata, Guinardia flaccida, G. striata, Dactyliosolen fragilissimus y Leptocylindrus danicus. Forty individuals of each species from each locality were isolated and measured with a Leitz Wetzlar binocular microscope with an ocular micrometer, magnified 400X. A one-way ANOVA showed the existence of highly significant differences (p < 0.001) in the biovolume of the species regarded with its locality. These differences could be due to: (a) temporal differences in sample collection: (b) the existence of populations in different phases of their vital cycles; (c) genetic differences; (d) and differences in the physical-chemical environment at each locality. The diameter was the morphometric variable exhibiting the largest positive correlation (r > or = 0.77, p < 0.001) with biovolume for all species, except for H. tamesis. In the latter, the apical axis (or side) exhibited the best correlation with biovolume (r = 0.94, p < 0.001). The high correlation between the diameter and/or the apical axis with the biovolumen suggests that the latter could be predicted from these morphometric variables with great reliability in these species.

Diatomeas de las lagunas de Unare y Piritú, estado Anzoátegui, Venezuela. Subclase Bacillariophycidae D. G. Mann / Diatoms from Unare and Píritu Lagoons, Anzoátegui state, Venezuela. Subclass Bacillariophycidae D. G. Mann

RESUMEN: La flora diatomológica de las Lagunas de Unare y Píritu, Venezuela, comprende organismos dulceacuícolas, estuarinos y marinos. En este trabajo se describen quince (15) especies de diatomeas (Bacillariophyta) pertenecientes a la subclase Bacillariophycidae. Las muestras de agua de las lagunas de Unare y Píritu (Venezuela), fueron colectadas entre noviembre 1988 y julio 1989. Estas fueron fijadas con formol neutro (10 %) y se examinaron mediante microscopía de contraste de fase. Las especies estudiadas fueron: Dictyoneis marginata (Lewis) Cleve, Cymbella affinis (Kützing) Cleve, Cymbella sp., Achnanthes brevipes var. intermedia (Kützing) Cleve, Lyrella irroratoides (Hustedt) Mann, Navicula carinifera (Grunow) Peragallo, Navicula liber (W. Smith) Peragallo, Navicula vacillans (Schmidt) Peragallo, Navicula sp., Amphora crassa var. campechiana Grunow, Amphora decussata Grunow, Caloneis powelli (Lewis) Cholnoky, Tryblionella acuta (Cleve) Mann in Round et al., Tryblionella apiculata Gregory, Surirella febigerii Lewis.

Dinoflagelados (pyrrhophyta) del archipiélago los Roques (Venezuela): familias prorocentraceae y ostreopsidaceae / Dinoflagellates (pyrrhophyta) from the los Roques archipielago (Venezuela): families prorocentraceae and ostreopsidaceae

Se examinaron muestras provenientes del Parque Nacional Archipiélago Los Roques, en el Mar Caribe Sur-Oriental (Venezuela), mediante microscopía óptica. Se describen quince (15) especies de dinoflagelados (Pyrrhophyta) pertenecientes a las familias Procentraceae y Ostreopsidaceae. Los símbolos (*) y (**) señalan nuevos registros para Venezuela y el Mar Caribe respectivamente. Se encontraron diez especies para Prorocetraceae: Mesoporos perforatus (Gran) Lillick, Prorocentrum compressum (Bailey) Abé ex Dodge, *Prorocentrum concavum Fukuyo, *Prorocentrum emarginatum Fukuyo, *Prorocentrum gracile Schütt, Prorocentrum lima (Ehrenberg) Dodge, Prorocentrum micans Ehrenberg, *Prorocentrum rhathymun loeblich III, Sherley & Schmidt, *Prorocentrum scutellum Schröder y Prorocentrum triestinum Schiller. En Ostreopsidaceae se encontraron cinco especies: Coolia monotis Meunier, *Gambierdiscus toxicus Adachi&Fukuyo, ** Ostreopsis lenticularis Schmidt, *Ostreopsis ovata Fukuyo y **Ostreopsis siamensis Schmidt. Finalmente se presenta una clave para las especies Prorocentrum y Ostreopsis encontradas en este estudio.

Order coccolithales (haptophyta): classification and phylogenetic relationships of extant families using phenetic and cladistic methods / Orden cocolithales (haptophyta): relaciones filogeneticas y clasificación de las familias vivientes mediante metodos feneticos y cladisticos

Cladistic and/or phenetic methods have not been used frequently in taxonomy and systematic of microalgae to develop more natural classifications. In this paper, these methods are applied for the first time to analyze eleven extant genera of Coccolithales. Also, the derived trees are compared with those ones suggested by fossil evidence and traditional systematic. Coccoliths morphological data of the following genera are used: calcidiscus kamptner, cocolithus schwarz, crenalithus roth, cyclolithela loeblich & tappan, emiliania hay & mohler, gephyrocaspa kamptner, hayaster bukry, helicosphaera kamptner, oolithotus reinhardt, tergestiella kamptner, and umbilicosphaera lohmann. Cladistic analysis suggests the existence of six evolutionary lineages, the most important of them are those formed by calcidiscus-cyclolithela-umbilicosphaera, and tergestiella-oolithotus. These lineages, and those suggested by fossil evidence and traditional systematic, are very similar. Helicosphaera could represent a very different lineage, an it may integrate another family. Homoplasies and reversions seem to be more frequent in Haptophyta than in other groups of microalgae. These results may explain partly the surprising diversification observed on this group of microalgae. These results may explain partly the surprising diversification observed on this group after the frequent massive extinctions showed by geological record.