Presence of two suctorian ciliate species of the genera Acineta and Pelagacineta, epibionts on marine copepod crustaceans.

Acineta arcachoniensis sp. nov., a new species of protist suctorian epibiont on the copepod Chiridius gracilis is described. The individuals show two well-developed actinophores, with two fascicles of capitate tentacles, an irregular nucleus, a cup-shaped lorica and a short stalk. Reproduction of A. arcachoniensis is by endogenous budding. The suctorians are located on the base of the antennae, the final abdominal segments or on the last pereiopod pair of the copepod. In addition, a new registration of the suctorian Pelagacineta euchaetae on the copepod Calanus helgolandicus is recorded.

Toxicity and bioaccumulation of lead and cadmium in marine protozoan communities.

The behavior of lead and cadmium in a protozoan community was studied in order to obtain new data regarding the toxicity and bioaccumulation of these heavy metals. For this purpose, microcosms with different concentrations of the pollutants (without metals, 500 microg Cd and Pb x L(-1) 1,000 microg Cd and Pb x L(-1)) were used. Protozoans bioaccumulated 7.03-207.00 microg Pb x g(-1) dry weight (dw) and 0.05-332.75 microg Cd x g(-1) dw, representing an accumulation capacity of up to 161.45 microg Pb x g(-1) dw and 310.75 microg Cd x g(-1) dw more than that of the bacteria. The addition of both metals caused a significant reduction in the density of protozoans. These data were compared with those obtained previously in treatments that used these metals separately.

Toxicity and bioaccumulation of cadmium in marine protozoa communities.

The behavior of cadmium in a protozoan community was analyzed in order to obtain new data concerning the toxicity and bioaccumulation of this heavy metal. For this purpose, microcosms with different concentrations of the pollutant (without cadmium, 500 microg Cd.l-1 and 1000 microg Cd.l-1) were used. Protozoans bioaccumulated 8. 74-283 microg Cd.g-1 dry weight, representing an accumulation capacity of 15.53-69.59 times more than that of bacteria. The addition of cadmium caused a significant reduction in protozoan density, whereas bacterial abundance was not affected.

Toxicity and bioaccumulation of lead in marine protozoa communities.

The toxicity and bioaccumulation of lead has been studied using marine protozoa communities developed in laboratory microecosystems. The concentrations tested were 500 and 1000 micrograms.L-1 of lead as lead acetate. The protozoan was able to bioaccumulate 27.02-504 micrograms Pb.g-1 dry weight. Bacteria also bioaccumulated lead, but always to a lesser degree than protozoa. Lead caused a significant reduction in the density of protozoa, which could be an indirect response to the cellular increase of lead. On the other hand, the toxicant did not determine a decrease in the number of bacterial cells; this could be due to their capacity to bioaccumulate a lesser amount of lead, the increase in the number of dead cells, and the elimination of their predators by the toxicant. After 120 h, a recovery of the community was observed.

The effects of cadmium on the successional stages of a freshwater protozoa community.

Microcosms containing protozoan were used to observe the differential effects of cadmium on the successional stages of a community. After 7, 14, and 21 days, 500 micrograms/liter cadmium was added. Some environmental parameters such as pH, conductivity, and nutrient levels affect metal toxicity. The effect of cadmium on diversity, density, and biomass was evident 48 hr after the addition of the metal. The pollutant caused a transition period in each treatment, of a different duration, followed by a recovery of the community. In both the control and the treatments, trophic structure was defined by bacterivore-detritivore, nonselective, and photoautotroph organisms.

Changes in trophic structure of a freshwater protozoan community subjected to cadmium.

The development of protozoan communities in laboratory microecosystems has been studied in order to observe the effect of cadmium on the trophic structure and dynamics of these communities. The effect of cadmium was evident on the species richness, density, and biomass. The most sensitive parameters seem to be biomass and species richness. In the controls, the trophic structure of the community was defined for bacterivore-detritivore, photautotroph, algivore, and in low proportion for nonselective species. In the fractions with cadmium there was a decrease in diversity in each trophic group; the bacterivore-detritivore and photosynthetic species were the most affected. Also, there was an appearance of saprotroph species. Species belonging to the control and others exclusively pertaining to microecosystems with cadmium were observed.

Morphology, biometry and taxonomic position of two peritrich ciliate Protozoa found in activated sludge.

The morphology of two sessile peritrich species taken from a plant for the processing of activated sludge is described. One of these species, having a non-contractile, branched peduncle, belongs to the genus, Heteropolaria, and the other having a single, contractile stalk, is a member of the genus Vorticella. A statistical and biometric study is made of their morphological characteristics, and the taxonomic position of both ciliates is discussed.

[Potential model for radiobiological research Stentor coeruleus (Protozoa)]. / Posible modelo para investigación radiobiológica: Stentor coeruleus (Protozoa).

The use of the ciliate Stentor coeruleus as a model to study radiosensibility after cobalt-60 irradiation is described.