Alicia H. Escalante

Fate of organochlorine pesticides in soils and terrestrial biota of “Los Padres” pond watershed, Argentina

Abstract Concentrations of organochlorine pesticides (OCPs) in soils and associated biota around “Los Padres” pond watershed were determined by gas chromatography with electron capture detector (GC–ECD). Pesticides were analyzed in different horizons (upper 0–15, middle 15–30, lower 45–55 cm) of natural and horticultural soils, developed in highlands and lowlands. Physical and chemical characteristics (organic matter content, pH, moisture, texture, etc.) were determined. Higher concentrations of total OCPs were found in highlands, because of the high content of clay material and organic matter. Lindane, heptachlor, aldrin, DDT and metabolites were found in soils. Depending on physical and chemical characteristics of pesticides and soils, different behaviours were found. Lindane could leach down to lower horizons, rich in clays, while hydrophobic pesticides remain in the upper horizons, retained by organic matter. Vegetables (carrots and potatoes) accumulated lindane with important contributions of DDTs and heptachlor. OCPs were taken up, accumulated and metabolized efficiently by terrestrial invertebrates (earthworms and beetles). The results obtained testify the pollution by OCPs in “Los Padres” pond watershed.

Agricultural soil as a potential source of input of organochlorine pesticides into a nearby pond

A study was conducted in the southeastern region of Buenos Aires province, Argentina, to assess an agricultural soil as a potential source of organochlorine (OC) pesticides for the aquatic biota of a nearby pond. We analyzed γ-HCH (lindane), still in use, and the following banned compounds: DDT, DDE, DDD heptachlor, heptachlor epoxide, aldrin, dieldrin and endrin in soil, bulrush, grass shrimp and fish using gas chromatography with electron capture detection (GC-ECD). Among the OC pesticides, lindane was most dominant in the soil (32.6 ng/g dry wt in the upper and 173.9 ng/g dry wt in the lower horizon) and bulrush (1.9 μg/g lipid). Macrophyte also accumulated high levels of heptachlor epoxide (1.5 μg/g lipid). Heptachlor, although present in the soil, was below the detection limit in all aquatic biota studied. Its primary degradation product, heptachlor epoxide, was found in both soil and biota samples. DDT was found at low levels in the surface soil (6.8 ng/g dry wt), but at higher concentrations in fish (3.6 μg/g lipid), although levels were still below permissible levels for human consumption. Since most of the compounds were found in both soil and aquatic biota, our study suggests that agricultural soil could be an important source for OC pesticides in the nearby pond.

Glycoproteins histochemistry of the gills of Odontesthes bonariensis (Teleostei, Atherinopsidae).

The histochemistry of glycoproteins (GP) in the mucous cells of the gills of the silverside Odontesthes bonariensis was identified with: (1) oxidizable vicinal diols; (2) sialic acid and some of their chain variants, carbon 7 ((7) C), carbon 8 ((8) C) or carbon 9 ((9) C); (3) sialic acid residues without O-acyl substitution and with O-acyl substitution at (7) C, (8) C or (9) C; (4) carboxyl groups and (5) sulphate groups. A battery of seven biotinylated lectins allowed GPs sugar residues to be distinguished. Mucous cells showed the presence of neutral, sulphated and sialylated GPs. Dolichos biflorus agglutinin (DBA) and Glycine max agglutinin (SBA) showed strong positive staining; Arachis hypogaea agglutinin (PNA), Ricinus communis agglutinin-I (RCA-I) and Triticum vulgaris agglutinin (WGA) showed moderate staining, while Ulex europaeus agglutinin-I (UEA-I) was completely negative.

Histology of the liver of Oligosarcus jenynsii (Ostariophysi, Characidae) from Los Padres Lake, Argentina

The liver is an organ notable for its sensitivity to a great variety of environmental factors. It is composed of a parenchyma divided into irregular lobules by the exocrine pancreas or hepatopancreas; the pancreatic cells are arranged around a branch of the portal vein. The hepatocytes are radially arranged in cords around a central sinusoid. The liver histomorphology and the organization of exocrine pancreatic tissue of O. jenynsii (Gunther, 1864) is similar to the acinar morphology of many teleosts, including freshwater and marine species. The aim of the present work was to carry out the histological analysis of the liver of Oligosarcus jenynsii, one of the most common species inhabiting Los Padres Lake (Buenos Aires Province, Argentina).

Trophic ecology and diet of Hydra vulgaris (Cnidaria; Hydrozoa)

Hydra is a genus of common, sessile, solitary freshwater cnidarians, which are defined as carnivorous and efficient predators. The purpose of this study was to obtain information on the feeding habits and diet of Hydra vulgaris collected from its natural habitat in Nahuel Ruca Lake (Buenos Aires Province, Argentina). We found three categories of food items in the coelenteron: algae, fungi, and small invertebrates. Algae dominated the diet in terms of abundance and frequency of occurrence, but their volumetric contribution was almost negligible, as was their possible nutritional value. Invertebrate prey captured, using active predation, represented the major volumetric contribution, with four different taxa found. The detection of phytoplankton in the gastral cavities reveals the input of some organisms present in the surrounding waters in addition to the invertebrates. This information is novel, since studies on the natural diet of Hydra are very scarce.

New record for the distribution of the colonial hydroid Cordylophora caspia (Pallas, 1771) (Cnidaria: Hydrozoa) in Argentina

Cordylophora caspia is a colonial, athecate hydroid inhabiting both in freshwater and brackish habitats. Its global distribution is in part due to its ability to tolerate a wide range of salinity. It is considered an invasive species and its control is widely studied because of the industrial and ecological problems it causes in many environments. We report for the first time the occurrence of this hydrozoan in Nahuel Ruca Lake (Buenos Aires province, Argentina) with some notes on its internal and external morphology.

Steganoderma (Steganoderma) valchetensis n. sp. (Digenea: Zoogonidae) from the relict fish Gymnocharacinus bergi (Osteichthyes: Characidae) in Argentina

A new species of Steganoderma (Steganoderma) (Digenea: Zoogonidae) was found in the digestive tract of the southernmost, endemic and scale-less characid, Gymnocharacinus bergi, inhabiting thermal headwaters of the Valcheta Creek in northern Patagonia, Argentina. Steganoderma valchetensis n. sp. is included in the subgenus Steganoderma because of having a sessile ventral sucker and caeca reaching to the testes. This new species can be distinguished from other species of this genus on the basis of body-length, sucker-ratio, the length of the cirrus-sac, the morphology of the seminal vesicle and gonads, and the location of the vitelline follicles and genital pore. The taxonomic status of the species of Steganoderma, parasitising the freshwater fishes of Patagonia, in southern Argentina, and Chile, is also discussed.