Edith Fanta

Liver histopathology of the fish brachydanio rerio hamilton-buchman after acute exposure to sublethal levels of the organophosphate dimethoate 500

Among the new substances that were synthesised by the chemical industiy during the last decades, with the aim to improve human prosperity, some cause negative effects on non target organisms like fish. Among the pesticides, the organophosphates (OP) are widely used in cattle management, agriculture and aquaculture activities. Brachydanio rerio Hamilton-Buchman, 1822 is used world-wide in fish-tests for the establishment of the lethal levels of pesticides. Nevertheless, these fish show morphological changes in their hepatocytes when exposed experimentally for 24 hours to the sublethal dose of 0.025 µl/l of the OP Dimethoate 500, in acute tests. Right hours after exposure, a high density of cells with cytoplasmic granulation is seen as well as focal necrosis. The main changes that occurred in the first 24 hours of exposure were the loss of the typical polygonal cell shape and of detectable cell limits, lateral migration of nuclei, nuclear size and shape, condensation of chromatin and pycnosis, increased cytoplasmic granulation followed by vacuolisation. After 48 hours in clean water, 72 hours from contamination, besides significant morphological changes and necrosis, focal regeneration of the hepatocytes, canaliculi, ducts and sinusoids were seen. Even having been exposed to the half of the dose considered as safe according to the general pesticide allowance rules, significant changes of the liver tissue were observed.

Sub-lethal effects of the organophosphate folidol 600 (methyl parathion) on Callichthys callichthys (pisces:teleostei)

Abstract 1. The sublethal effects of Folidol 600, an organophosphate containing methyl parathion as its active principle, were analysed in the fish Callichthys callichthys. 2. After an intracoelomatic application of 500 mg/kg of Folidol 600, the behavior and the levels of plasmatic cholinesterase were analysed along the time, in acute experiments. 3. Plasma cholinesterase activity was inhibited by 90% after 4 hr from the initial time, keeping this level of inhibition for 4 days. 4. It recovered slowly in the next 8 to 10 days, reaching about 80–90% of the normal levels around the 35th day after the beginning of the experiment. 5. Many behavioral changes were observed in the first 96 hr, such as: lowering of motility with loss of equilibrium and frequent unnatural body positions; uncoordinated movements leading to incapacity of food intake; and increase in the levels of respiratory frequency.

Surface ultrastructure of the gills of the mullets Mugil curema, M. liza and M. platanus (Mugilidae, Pisces).

Mugil curema, M. liza, and M. platanus were collected from the southeastern and southern coast of Brazil. The second gill arches were analyzed by scanning electron microscopy and histology. The highest density of chloride and mucus‐secreting cells was observed in the gill filaments of M. liza and M. platanus. Spines are scarce and were found only in the pharyngeal region of M. curema. The dorsal angle of curvature of the simple projections is most reduced in the rakers of M. liza and M. platanus. The raker borderline on the internal side of the arches of M. curema has grooves that do not occur in the other two species. On the external side of the branchial arches, the borders of the rakers of M. liza and M. platanus are smooth. The shape of the rakers is characteristic for each species: in M. curema, it resembles the letter “D”; in M. liza, it is trapezoidal, and in M. platanus, it is triangular. Thus there is a morphologic similarity between M. liza and M. platanus, and both differ from M. curema. All three species show elongated and extremely elaborated rakers that are placed next to each other and turned toward the opercular cavity. There are few taste buds and only several mucus‐secreting cells along the whole pharyngeal region. These characteristics suggest that these species do not select food chemically but obtain it mechanically with the rakers and aggregate it with mucus. J. Morphol. 247:122–133, 2001.

Microscopic morphology and histochemistry of the digestive system of a tropical freshwater fish Trichomycterus brasiliensis (Lütken) (Siluroidei, Trichomycteridae)

The digestive system of Trichomycterus brasiliensis (Lutken, 1874), a small sized tropical Teleostean fish widely distributed in South America, was studied. Tissue samples were prepared for light and scanning electron microscopy (SEM). Trichomycterus brasiliensis shows stratified esophagus epithelium with taste buds and goblet cells with neutral and acid mucus at the anterior region. The stomach is caecal, presenting a pyloric valve with neutral mucus cells. At the terminal portion it is surrounded by a thick muscular wall. The intestine shows two loops; the epithelium is single columnar, with acid and neutral mucus in goblet cells. Multicellular intestinal glands are absent. Granular cells are often seen in the mucosa, less in the submucosa but were not observed in the muscularis. After the intestine-rectal valve, the rectum shows lower mucosal folds, more goblet cells and a thicker muscularis. No lobes were observed at the liver. Small regions of pancreatic tissue may be identified within the hepatic tissue mainly surrounding vessels and ducts. A compact pancreas may also be observed ventrally to the stomach and covering the bile duct. The possible significance of the heterogeneous character of the digestive tube mucosubstances is discussed. The digestive system of T. brasiliensis presents structural characteristics of a predator fish.

Gills of juvenile fish piaractus mesopotamicus as histological biomarkers for experimental sub-lethal contamination with the Organophosphorus Azodrin®400

Piaractus mesopotamicus e um peixe de agua doce encontrado na Bacia Parana-Paraguai e na regiao do Pantanal, tendo sido usado em programas de repovoamento no Brasil. Peixes juvenis foram expostos por 96 horas a dose sub-letal de 1.08mg/L do organofosforado (OP) Azodrin®400 que contem 0,43µL/L do principio ativo monocrotofos. A patologia frequente nas brânquias foi o descolamento epitelial que variou de minimo nas primeiras 24 horas a severo ou intenso apos 48 horas de contaminacao. Deformacoes e degeneracao de celulas pilares nas lamelas respiratorias levando a formacao de espacos sanguineos irregulares e congestao sanguinea, hiperplasia e fusao lamelar tambem foram observadas. Sugere-se que 48 horas apos o T0 e um tempo critico apos exposicao a niveis subletais de OP, pois a capacidade de trocas gasosas podera ter diminuido, levando ao enfraquecimento dos peixes. Os sintomas poderao prejudicar o desenvolvimento dos juvenis introduzidos em corpos de agua em programas de repovoamento.

Hepatic alterations in the fish Rhamdia quelen contaminated with Folidol 600

This study has the aim of verifying the morphologic alterations in the hepatic tissue of Rhamdia quelen juveniles when exposed to 0.01 mL/L of Folidol 600. Techniques of light microscopy and transmission electronic microscopy were used. The liver was target for the Folidol 600 action after 4h of contamination. Loss of cellular contour, picnotic nucleus and decharacterization of the endothelium and of the rough endoplasmic reticulum were observed. Focuses of necrosis increased significantly when compared to the control sample at the exposure times of 48 and 72 h to the organophosphate. The density of hepatocytes increased significantly in every experimental time when compared to the control sample. The number of hepatocytes with biliary pigment increased significantly in the first 72 h of exposure when compared to the control. Folidol 600 was responsible for serious alterations in the hepatic tissue of the Rhamdia quelen.

The effect of environmental oxygen and carbon dioxide levels on the tissue oxygenation and the behavior of Antarctic fish

Abstract 1. 1. The effect of the environmental oxygen and carbon dioxide levels on the tissue oxygenation of Antarctic fishes was studied. 2. 2. Levels of muscle oxygen were directly assayed in living animals by means of an implanted oxygen microelectrode; the respiratory frequency was established and the behavior of the animals described. 3. 3. Notothenia rossii marmorala N. neglecla N. gibberifrons, Trematomus bernacchii and T. hansoni (Pisces, Teleostei, Notothenidae) displayed different reactions to this kind of environmental impact.

Influence of photoperiod on visual prey detection in the Antarctic fish Notothenia neglecta

Reaction to the presence of prey, after visual stimulation, was tested in the Antarctic nototheniid fish Notothenia neglecta Nybelin under four different simulated Antarctic seasons - photoperiods of 24 hours light, 22 light/2 darkness, 12 light/12 darkness, and 24 hours darkness. Live Lepidonotothen nudifrons were used for visual stimulation, with exclusion of chemical and mechanical signals. The photoperiod showed significant correlation with the number of individuals stimulated and with the latency time of the first response to the presence of prey, but not with the number of attacks or pursuits. However, there were more pursuits in darkness than in light. Notothenia neglecta presumably perceive a large spectrum of wavelengths, because they had the shortest reaction time under red light, used to simulate darkness. The tests proved that N. neglecta are capable of detecting prey using only vision, in all seasons of the year, but that the optimal reactions occur in a photoperiod corresponding to the Antarctic autumn or spring.

Spatial and temporal variation in krill consumption by the Antarctic fish Notothenia coriiceps , in Admiralty Bay, King George Island

An index of integrated food preferences (IFA) of Notothenia coriiceps Richardson at two sites in Admiralty Bay (Ipanema and Smok Point), calculated for two sequential summers, showed that during 1998/99, the most important food item was Euphausia superba (krill) at both Ipanema (IFA = 0.83) and Smok Point (IFA = 0.75), while the sum of all other food items was significantly smaller (IFA respectively 0.21 and 0.26). Macroalgae, gammarid amphipods and gastropods dominated the diet in the summer 1999/00 (IFA respectively 0.32, 0.32 and 0.21), at Ipanema, while macroalgae were dominant at Smok (IFA = 0.67), where krill and amphipods were secondary prey (IFA respectively 0.12 and 0.14) and gastropods were absent. Thus, the diet composition of N. coriiceps can possibly be used as an indicator of the presence of pelagic krill swarms.

Behaviour and orcadian rhythm of the fish bathygobius soporator Valenciennes (Gobiidae) under the influence of environmental salinity and temperature

The behavioural patterns and their cireadian rhythms may be adaptive to the peculiar environmental conditions of subtropical brackish waters where Ba-thygobius soporator Valenciennes, 1837 live. Adult fish were caught at the southern Brazilian coast from mangrove rivers and rocky shores in a bay, where temperature and water salinity vary during the day and through the year. Observation on the behaviour of the animals was undertaken in salinity 8.5ppt, 17.0ppt, 25.5ppt and 34.0ppt, each one in temperatures of 18oC and 28oC. Temperature and salinity affect the frequency and intensity of some of the behavioural events, more than its pattern or rhythm. Swimming is rare, decreasing along the day and with temperature increase, being even lower at low salinity; aggressiveness is the highest in the morning being not affected by temperature, but by salinity, being higher the higher it is; territory defence decreases along the day and is lower at high temperature and extreme salinities; fish hide more at high temperature and with the decrease of salinity, but this is not rhythmical; a higher proportion of fish rest in vertical position when salinity and temperature are high, increasing slightly at the beginning of the afternoon; respiratory frequency increases with temperature, salinity and in the afternoon; the colour of the fish is mainly light with spots in all hours of the day and in all temperatures and different levels of salinity, but with a tendency of the presence of some dark fish during the morning and some light ones in the afternoon, showing a higher variability of colours at low temperature and extreme salinities. Besides temperature, salinity and light, feeding seems to be one of the determinant factors for the performance of the typical behaviour of B. soporator.