Toxicity of cadmium to free-living marine and brackish water nematodes (Monhystera microphthalma, Monhystera dis-juncta, Pellioditis marina)

Abstract

Cadmium toxicity to 3 marine and brackish-water nematodes (Monhystera microphthalma, M. disjuncta, Pellioditis marina) was estimated under static tests. These nematodes are very resistant to cadmium poisoning. LC 50 values are extremely time-dependent; an exposure time of 96 h underestimates the degree of toxicity. For M. rnicrophthalrna LC 50 values decreased from 23.6 ppm after 96 h to 5.4 ppm after 312 h. For M. disjuncta LC 50 values were 21.2 and 18.4 ppm after 192 and 264 h respectively. P. marina was much more tolerant to cadmium in comparison with the monhysterids and had LC 50 values of 90.5 ppm at 120, and of 77.0 ppm at 192 h. It is argued that MEC (minimum effective concentrations) values are ecologically more meaningful than LC 50 values, and that the former levels can be used as indicators of intolerable thresholds in the field. MEC values based on mortality and on a developmental assay in which success in attaining the adult stage was studied, turned out to be very similar. The developmental assay takes less time than the survival assays and the slope of the response curve can be used as a parameter for describing species sensitivity.

Closely related intertidal and deep-sea Halomonhystera species have distinct fatty acid compositions

“…It has been suggested that marine nematodes do not accumulate lipids for energy storage [27] indicating that nematode fatty acid composition reflects membrane fatty acid composition, however, information remains scant. In this study we will focus on the marine free-living nematode Halomonhystera disjuncta (formerly known as Geomonhystera disjuncta), which is known for its high resistance to environmental stress, especially to heavy metals and temperature changes [25,[75][76][77]. H. disjuncta and sister species has been reported both in shallow-water [15,47,74] and in deep-sea environments [53,71].…”

Heavy Metal Contents in Tissues of Dominant Species of the Benthos and in Bottom Sediments of Zolotoi Rog Bay, Sea of Japan

“…Nonselective deposit-feeders and omnivores are extremely nonsensitive, they can rapidly increase their density by completely changing the trophic structure of the nematocene. Such structural alteration has been reported for heavily polluted areas of the North Sea where bottom sediments are inhabited by impoverished communities of nematodes composed almost entirely of nonselective deposit-feeding and omnivorous species [30], in ports of the Sea of Japan [16,17], and in microcosm experiments [14,24].…”

“…Cuticular adsorption and the absorption of heavy metals cause increased metal contents in the hypoderm [19]. The external part of the three-layer cuticle consists of collagenlike material secreted by nematodes, which contains disulfide bonds that support its tertiary structure and sulfhydric groups ensuring heavy metal binding and detoxification [10,19,21,30].…”

Description of two free-living nematode species of Halomonhystera disjuncta complex (Nematoda: Monhysterida) from two peculiar habitats in the sea

“…The type species H. disjuncta (Bastian 1865) is one of the most well-known marine nematodes. As a model species, H. disjuncta (then under generic names Monhystera and Geomonhystera) has been subject of previous studies on morphology and ultrastructure (Geraert et al 1981; Van de Velde and Coomans 1987, 1991, 1992, demography, physiology and energetics (Chitwood and Murphy 1964;Vranken et al 1988;Herman and Vranken 1988;Herman et al 1984), impact of temperature and salinity on life cycle (Gerlach and Schrage 1971;Vranken and Heip 1986), and toxicology (Vranken et al , 1985(Vranken et al , 1989. Data on geographical records of H. disjuncta and related species have been summarized by Gerlach and Riemann (1973), Jacobs (1987) and in some subsequent publications thereafter.…”