Ignacio Alejandro Pérez-Legaspi

Effect of temperature and food concentration in two species of littoral rotifers

We performed life-table experiments with two species of the littoral rotifers Lecane luna (O.F. Muller, 1776) and Lecane quadridentata (Ehrenberg, 1832). Three different temperatures (20, 25 and 30°C) and food concentrations of Nannochloris oculata (1×107, 5×106, and 1×106 cells ml-1) were investigated. We found important differences between both species in all the treatments regarding offspring sizes, hatching percentages, life span and reproductive rates. Our data on hatching percentages of asexual eggs suggested that the optimal temperature for both species is in the 20–25°C range. On the other hand, reproductive data placed the optimal temperature near 25°C. This information can be used to develop aquatic toxicology tests with littoral species.

Acute toxicity tests on three species of the genus Lecane (Rotifera: Monogononta)

Three rotifer species, Lecane hamata L. luna, and L. quadridentata, were submitted to acute toxicity tests to compare their susceptibility to 11 toxicants. In acute tests with 48-h exposure of neonates of less than 24 h old, copper was most toxic with LC50 values in the range of 0.06–0.33 mg 1−1, while acetone was the least toxic with LC50 values in the range of 5000–7000 mg 1−1. Differences in LC50 value of up to 22-fold were found in the susceptibility to lead between the three species. These data indicate large differences in toxicity among members of the same genus, and point out that it is necessary to submit several species to toxicity tests in order to assess the potential effects of toxicants to rotifers. The commonly used Brachionus calyciflorus cannot be considered representative of all freshwater rotifers in this respect.

Comparing toxicity endpoints on Lecane quadridentata (Rotifera: Monogononta) exposed to two anticholinesterases pesticides.

Toxicity tests were performed on the freshwater rotifer Lecane quadridentata exposed to the pesticides carbaryl and methyl parathion (lethal, sublethal, and chronic) to compare the sensitivity between different endpoints: (a) 48‐h mortality; (b) 30‐min in vivo inhibition of esterase activity; (c) 5‐day inhibition of the instantaneous growth rate. The emphasis of this work was to find the most appropriate endpoint to evaluate the toxicity of these pesticides in view of their sensitivity, duration, and ecological relevance. The comparison between the three toxicity tests show that the 5‐day chronic tests have the lowest EC50 (2.22 and 6.6 mg/L), lowest‐observed‐effect concentration (2.5 and 2.5 mg/L), and no‐observed‐effect concentration (1.0 and 1.2 mg/L) values for carbaryl and methyl parathion, respectively. This indicates that the estimate of the instantaneous rate of natural increase r is the most sensitive endpoint regarding the toxicity of these pesticides. This sensitivity might be due to the effect on reducing the growth potential form the first generation on. Lethal and sublethal tests are closely related, suggesting that the immediate effect after inhibition of esterases is death. In general, the sensitivity of L. quadridentata is similar to other species of rotifers exposed to methyl parathion. Therefore, the 5‐day chronic toxicity test with the freshwater rotifer L. quadridentata should be considered a good candidate to evaluate the effect of anticholinesterase pesticides, due to its high sensitivity and ecological relevance.

Phospholipase A2 activity in three species of littoral freshwater rotifers exposed to several toxicants.

We analyzed three species of Lecane, a littoral rotifer, for susceptibility to six metals and four organic toxicants using a fluorometric assay based on inhibition of activity of the enzyme phospholipase A2. The metallic toxicants that we tested included Cd, Cr, Cu, Pb, Hg (as HgCl2), and Ti; the organic toxicants included benzene, ethyl acetate, toluene, and vinyl acetate. The three species differed greatly with respect to their susceptibility to the various toxicants. Lecane quadridentata, for example, was particularly sensitive to the four organic compounds (median effective concentration values [EC50] ranged from 6.6 x 10(-4)-0.987 mg/L). Lecane luna, in contrast, seemed particularly sensitive to metals (EC50 values ranged from 2 x 10(-6)-1.92 mg/L). Lecane hamata was relatively insensitive to organic solvents (EC50 values ranged from 4.25-126.5 mg/L).

THE USE OF AQUATIC INVERTEBRATE TOXICITY TESTS AND INVERTEBRATE ENZYME BIOMARKERS TO ASSESS TOXICITY IN THE STATES OF AGUASCALIENTES AND JALISCO, MEXICO

This1 paper describes a series of techniques using several aquatic invertebrates as indicators of adverse effects in natural and man-made aquatic environments. The information obtained in these techniques allowed the monitoring of the municipal drinking water system of the city of Aguascalientes, Mexico and the detection of toxicity in streams suspected of dumping of agricultural and industrial discharges in the states of Aguascalientes and Jalisco, in Mexico.

Identification of exocytotic membrane proteins in three rotifer species

We confirmed the presence and expression of exocytotic membrane proteins: Syntaxin-1, Syntaxin-4, SNAP-23, and SNAP-25 in the rotifers Brachionus calyciflorus, Lecane quadridentata, and Philodina roseola. These proteins were identified by immunohistochemistry and immunoblot analysis using antibodies against Syntaxin-1, Syntaxin-4, SNAP-23, and SNAP-25. The presence of these proteins were observed mainly in regions of the nervous, reproductive, and glandular systems of these rotifer species, which underlines the fundamental role of exocytotic docking and fusion membrane proteins in the vesicular release of secretory proteins. The immunoblot analysis confirmed the expression of Syntaxin-1, Syntaxin-4, and SNAP-23 in the three rotifer studied, but not of SNAP-25. This study contributes to rotifer biology by revealing the presence of conservative exocytotic machinery such as SNAREs proteins in the phylum Rotifera, including members of the Class Bdelloidea the highest taxa of metazoans where sexual reproduction does not exist.

Effects of copper addition to laboratory maintained microcosms of Presidente Calles Reservoir organisms (Aguascalientes, Mexico)

Abstract We studied the effects of five different concentrations of copper (0.05, 0.20, 0.45, and of 0.05 added continuously up to 0.45 mg l-1) in 30 l aquaria containing water and organisms from Presidente Calles reservoir, the biggest reservoir in the State of Aguascalientes, Mexico. Large reductions in zooplankton density, species diversity and total chlorophyll were found when we compared the different treatments against controls. Initial addition of a greater amount of copper has a more adverse effect than constant additions of small amounts of copper as suggested by smaller reductions in zooplankton density and chlorophyll. This result agrees with the previous reports on the effects of other metals in different aquatic microcosms. The most dramatic effect of copper addition on zooplankton density was found three days after copper addition. Lethal effects on cladocerans, copepods, and rotifers were found at a concentration of 0.45 mg l-1. These results are important for regulatory agencies in Mexico ...

Adverse Effects of Herbicides on Freshwater Zooplankton

Roberto Rico-Martinez1, Juan Carlos Arias-Almeida2, Ignacio Alejandro Perez-Legaspi3, Jesus Alvarado-Flores1 and Jose Luis Retes-Pruneda4 1Departamento de Quimica, Centro de Ciencias Basicas, Universidad Autonoma de Aguascalientes, Aguascalientes, 2Limnologia Basica y Experimental, Instituto de Biologia, Universidad de Antioquia, Medellin, 3Division de Estudios de Posgrado e Investigacion. Instituto Tecnologico de Boca del Rio, Boca del Rio, Veracruz, 4Departamento de Ingenieria Bioquimica, Centro de Ciencias Basicas, Universidad Autonoma de Aguascalientes, Aguascalientes, 1,3,4Mexico 2Colombia

Rotifers as Models in Toxicity Screening of Chemicals and Environmental Samples

An important objective of aquatic ecotoxicology is to determine the effects of toxic com‐ pounds in organisms that play a central role in aquatic communities where rotifers have a large impact on several important ecological processes. The contribution of the rotifers to secondary production in many aquatic communities is substantial as they are often the larger fraction of zooplankton biomass at certain times of the year. In addition to the im‐ portance of their ecological roles in aquatic communities, the rotifers are attractive organ‐ isms for ecotoxicological studies by its short life cycles and rapid reproduction, their small size, and little volumes needed for culture and toxicity assays. The main end points used in ecotoxicological studies are mortality, reproduction, behavior, and biomarkers. Such parameters are included in international regulations from all over the world, where different species are used to evaluate the effect of environmental samples or chemical compounds. The high diversity of rotifers is an important issue because it can modify their relative susceptibility to toxicants. Thus, more studies are needed to know the rela‐ tions and mechanisms involved in clonal variation, sensitivity, and development, which can be all assessed by state-of-the-art procedures.

Chapter 3:Rotifers as Models for Ecotoxicology and Genotoxicology

Rotifera is a group of pseudocoelomate aquatic invertebrates with great potential as model organisms for ecotoxicology and genotoxicology. This potential is based on their: (a) fast growth and reproduction, (b) ease of culture and maintenance, (c) cyst production, (d) alternation of asexual and sexual generations, among others. While the use of rotifers as models for ecotoxicology is well documented and more species, tests, and information are added every day, the potential use of rotifers for genotoxicology is still very limited. In this chapter the authors attempt to explain the state of the art regarding the use of rotifers as models for both eco- and geno-toxicology. To achieve this, the authors have implemented a complete search in the mainstream scientific literature describing types of studies, perspectives, and use of rotifers in both areas. In the case of genotoxicology an emphasis has been made to incorporate suggestions on the advantages that rotifers represent if used as model organisms for the different techniques and studies instead of the most traditionally used organisms. Among the main topics included in genotoxicity are: (a) aging, (b) horizontal gene transfers and gene conversion induced by chronic exposure, (c) detoxification mechanisms, (d) transgenerational effects, and (e) micro evolution as mechanisms of adaptation to toxic exposure.