Population growth of Brachionus macracanthus (Rotifera) in relation to cadmium toxicity: Influence of algal (Chlorella vulgaris) density

Abstract

In the present work, we quantified the harmful effects of Cd(+ 2) to Brachionus macracanthus using both acute (median lethal) and chronic (population growth) toxicity tests. Chronic toxicity tests were conducted under 4 different concentrations (0.000625-0.005 mg L(- 1)) of cadmium chloride at 23 degrees C under 3 food (Chlorella vulgaris) levels (0.5 x 10(6), 1.0 x 10(6) and 2.0 x 10(6) cells mL(- 1)) using static renewal system for three weeks. The median lethal concentration bioassayed at 24 h (LC(50)) for B. macracanthus was 0.19 mg L(- 1) of CdCl(2). Cadmium adversely affected the population growth of B. macracanthus at all tested concentrations. Increase in algal food had a positive effect on the rotifer growth in controls; with increase in Cd levels, the population growth of B. macracanthus decreased even under the highest food level tested. The peak population abundance of B. macracanthus in controls at the highest food level of 2.0 x 10(6) cells mL(- 1) was 40 ind. mL(- 1). Depending on the heavy metal concentration and the algal level, the population growth rate (r) of B. macracanthus varied from 0.02 to 0.28 day(- 1). The relatively higher sensitivity of B. macracanthus to cadmium toxicity is discussed in relation to other species of the same genus.

Body size and population growth ofBrachionus patulus(Rotifera) in relation to heavy metal (copper and mercury) concentrations

“…[6] Also, for a given toxicant, safe concentration derived using application factors from LC 50 may be still adverse to the test species, if evaluation at sublethal concentration is carried out experimentally. [12] This is also evident from the present work. Thus, based on the median lethal data of Cu +2 or Hg +2 reported for B. patulus, [17,20] the safe concentrations (1/10th of LC [25] 50 ) are expected to 10 and 2.7 µg/L, respectively.…”

“…[9] In population growth studies, it is possible to evaluate the possible role of adaptation of a test species because the test jars contain individuals of different age groups simultaneously. [12] Rotifers, particularly brachionids, show changes in the morphology when subject to stress from both biotic (e.g., predation) and abiotic (e.g., temperature) factors. [13−15] Under stressful conditions, the body size of zooplankton vary considerably.…”

Validating the systematic position of Plationus Segers, Murugan & Dumont, 1993 (Rotifera: Brachionidae) using sequences of the large subunit of the nuclear ribosomal DNA and of cytochrome C oxidase

“…The inclusion of more species and sequences of another nuclear or mitochondrial genes would be necessary to clarify the monophyly or paraphyly of Brachionidae. The genus Plationus was described by Segers et al (1993) and included three species Plationus patulus, P. polyacanthus, and P. macracanthus which have been alternatively assigned to Brachionus or Platyias (Müller, 1786;Ahlstrom, 1940;Bartos, 1959;Rudescu, 1960;Kutikova, 1970;Kotikova et al, 2005;XianLing et al 2006;Nandini et al, 2007;Kennari et al, 2008;Sarma et al, 2008). Later another two taxa-P. patulus patulus and P. felicitas-were added to the genus Plationus (Segers, 2007).…”

“…In the most recent revision of Rotifera, the genus Plationus contains three species, Plationus felicitas (Wulfert, 1965), P. patulus, and P. polyacanthus, and two subspecies, P. patulus patulus and P. patulus macracanthus (Segers, 2007). However, some studies do not recognize the validity of these species and subspecies as members of Plationus, and still classify them with Brachionus or Platyias (Kotikova et al, 2005;Xian-Ling et al, 2006;Nandini et al, 2007;Kennari et al, 2008;Sarma et al, 2008). The aim of this study was to develop a phylogeny for five genera of Brachionidae with a particular interest in the systematic position of Plationus patulus and P. patulus macracathus based on gene sequences of cytochrome oxidase subunit 1 (cox1) and domains D2 and D3 of the large subunit of the nuclear ribosomal RNA (LSU).…”