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Abstract Mercury (Hg) is a global pollutant that may exert its toxic effects on living organisms and is found in both aquatic and terrestrial ecosystems in three chemical forms; elemental, organic, and inorganic. The inorganic form (iHg) tends to predominantly accumulate in aquatic environments. The gill apparatus is a very dynamic organ that plays a fundamental role in gas exchange, osmoregulation, acid-base regulation, detoxification, and excretion, and the gills are the primary route of waterborne iHg entrance in fish. In the present work we investigated the morphofunctional and ultrastructural effects in Danio rerio gills after 96 h exposure to two low HgCl2 concentrations (7.7 and 38.5 µg/L). Our results clearly demonstrated that a short-term exposure to low concentrations of mercury chloride resulted in gill morphology alterations and in the modifications of both Na+/K+-ATPase and metallothioneins (MTs) expression pattern. The main morphological effects recorded in this work were represented by hyperplasia and ectopia of chloride cells (CCs), lamellar fusion, increased mucous secretion, alteration of pavement cells (PVCs), detachment of the secondary epithelium, pillar cell degeneration, degeneration, and apoptosis. Trough immunohistochemistry and real-time PCR analysis also showed a dose-related modulation of Na+/K+-ATPase and MTs. [ABSTRACT FROM AUTHOR]

Mercury (Hg) is a highly hazardous pollutant widely used in industrial, pharmaceutical and agricultural fields. Mercury is found in the environment in several forms, elemental, inorganic (iHg) and organic, all of which are toxic. Considering that the liver is the organ primarily involved in the regulation of metabolic pathways, homeostasis and detoxification we investigated the morphological and ultrastructural effects in Danio rerio liver after 96 h exposure to two low HgCl2 concentrations (7.7 and 38.5 µg/L). We showed that a short-term exposure to very low concentrations of iHg severely affects liver morphology and ultrastructure. The main effects recorded in this work were: cytoplasm vacuolization, decrease in both lipid droplets and glycogen granules, increase in number of mitochondria, increase of rough endoplasmic reticulum and pyknotic nuclei. Pathological alterations observed were dose dependent. Trough immunohistochemistry, in situ hybridization and real-time PCR analysis, the induction of metallothionein (MT) under stressor conditions was also evaluated. Some of observed alterations could be considered as a general response of tissue to heavy metals, whereas others (such as increased number of mitochondria and increase of RER) may be considered as an adaptive response to mercury. [ABSTRACT FROM AUTHOR]

The fine structure of book lungs is not homogeneous across Arachnids and is considered phylogenetically informative, however few reports on the ultrastructural features of this organ have been published. In this study, we examined the general morphology and ultrastructure of adult spiders of the genus Cteniza . The respiratory system of Cteniza sp. consists of two pairs of well-developed book lungs, which is considered indicative of primitive spiders. The general organization of the book lungs is similar to that described for other arachnids and consists of leaves of alternating air and hemolymph channels. The air channels are lined with cuticle and open to an atrium that leads to a slit-like spiracle. The air channels are held open by cuticular trabeculae. The space holders in the hemolymph channels are pillar trabeculae formed by two cells from the opposed walls. The pillar cells have a complex ultrastructure that includes an interdigitating connection, gap junctions, microtubules and hemidesmosomes. These features apparently help strengthen the pillar cells and their interconnections with each other and the underlying cuticle. The cytoskeleton resembles that of arthropod tendon cells where substantial structural support is needed. [ABSTRACT FROM AUTHOR]

Abstract: An investigation was conducted to determine the effects of the heavy metal, cadmium (Cd), on the gills of the teleost fish, Thalassoma pavo Linnaeus, 1758. The fishes were exposed to several sublethal concentrations of cadmium (10, 40, 60 and 120μM (mg/L)) for a period of 48, 96 and 192h. The value of the LC50 after 96h of cadmium exposure, determined using the System of Finney, was equal to 128.3μM. The gills of the fishes were examined by light and electron microscopy. Toxic, apoptotic and cadmium effects were analyzed using some neuropeptides, metallothioneins (MT), caspase 3, PCNA and calmodulin, as bioindicators, respectively. The results showed that the alterations in the gills were proportional to the exposure periods and concentrations of the metal, which were found to be both dose and time dependent. The biological responses in the gills of the tested animals are discussed in relation to results obtained by analysis of the biomarkers. These data may be used for the planning of a model to determine biological risk in the marine environment and may be particularly useful to investigate organisms exposed to cadmium. [Copyright &y& Elsevier]

Abstract: We analysed the morphology and ultrastructure of the gill apparatus of the ornate wrasse, Thalassoma pavo, under normal conditions and after exposure to a sublethal concentration of sodium lauryl sulphate (3.5mg/l, which is one-third of the 96LC99 value). To identify the biochemical mechanisms affected by this pollutant, we evaluated and compared the localisation of Na+/K+ ATPase in normal and experimental conditions. Immunocytochemical analysis revealed that this enzyme was active in the chloride cells (CCs), which were distributed in clusters in the interlamellar region of the filament. Ultrastructural analysis revealed conspicuous alterations on the epithelium after 96 and 192h of exposure to sodium lauryl sulphate: structural features of the surface cells were lost, the appearance of intercellular lacunae changed, and cellular degeneration occurred. Statistical analysis comparing the number and dimensions of CCs in normal conditions and after 96h of exposure showed that the CC area decreased after exposure to the detergent. [Copyright &y& Elsevier]

Abstract: Endosulfan is an organochlorine pesticide used in agriculture for a wide range of crops. Endosulfan concentrations of up to 0.7mg/L can be found in ponds and streams near sprayed agricultural fields. We investigated the short-term toxicity of endosulfan in common toad (Bufo bufo) tadpoles after 24, 48, and 96h of exposure. Acute toxicity was evaluated at nominal concentrations ranging from 0.01 to 0.6mg/L: concentrations that could be found after the application of pesticide. Our results show that 0.43mg/L of endosulfan caused 50% mortality (LC50). The effects of a sublethal endosulfan concentration (0.2mg/L) on gill apparatus morphology were evaluated by scanning and transmission electron microscopy. Immunohistochemical methods were also applied to detect the expression pattern of the inducible isoform of nitric oxide synthase (iNOS) in the gills using the confocal laser scanner microscope. Exposure to 0.2mg/L of endosulfan caused an apparent increase in mucus production, the occurrence of secretory vesicles and lamellar bodies, a widening of intercellular spaces and additionally there was evidence of an inflammatory response in the gill apparatus. The morphological alterations occurred after 24h and were more pronounced after 48 and 96h of exposure. Altered morphology and increased mucus secretion indicate impaired gas exchange and osmoregulation in the gills. In addition, there was an increase of iNOS expression after 24 and 48h which may reflect hypoxia and inflammation in the gill epithelium. Our results clearly indicate that short-term exposure to a sublethal concentration of endosulfan, near the high end of the environmental range, disrupts gill morphology and function in B. bufo tadpoles. [Copyright &y& Elsevier]

Chlorpyrifos (CPF) is an organophosphorus insecticide commonly used for domestic and agricultural purposes. The risk posed by environmental contamination from CPF is well acknowledged, and it has been detected worldwide in aquatic habitats and coastal areas. In addition, due to its slower degradation in seawater compared to freshwater, CPF is of particular concern for marine environments. Here, we investigated for the first time the morpho-functional alterations induced by CPF on the gills of Thalassoma pavo, a widespread species in the Mediterranean Sea. We tested the effects of two sublethal concentrations (4 and 8 µg/L) after 48 and 96 h. Our study demonstrates that the alterations induced by CPF are dose and time-dependent and highlight the harmful properties of this insecticide. After exposure to the low tested concentration, the more frequent alteration is an intense proliferation of the primary epithelium, whereas after exposure to the high concentration, the primary epithelium proliferation is less extensive, and the most evident effects are the thinning of secondary lamellae and the ectopia of chloride and goblet cells. CPF also modulated the expression of Na+/K+-ATPase. Dilation of lamellar apical tips, pillar cell degeneration, and appearance of aneurysms are often observed. [ABSTRACT FROM AUTHOR]

• Morphofunctional alterations of seawater fish gills after exposure to lead. • Sublethal lead concentrations affect gills histology and ultrastructure after short-term exposure. • Epithelial and vascular injuries induced by lead contribute to the gills function impairment. • Lead exposure induces metallothionein expression in gills of seawater fish. Lead is one of the most alarming toxic pollutants for the environment due to its acute toxicity and high bioaccumulation tendency. Despite legislative efforts, world lead production has more than doubled since the early 1970s to 2016. Due to extensive exploitation and human activity, the coastal and estuarine regions belong to marine environments that are mostly and more rapidly deteriorated by pollutants including lead. A limited number of studies examined the effects of lead in fishes, compared to other aquatic models and even fewer studies have been dedicated to seawater fishes especially regarding Pb adsorption and accumulation in specific organs. Fish gills, key compartments involved in several crucial functions such as gas exchange, osmoregulation, and excretion, are also the organs in which Pb is mainly accumulated. Herein, we investigated the morphofunctional and ultrastructural modifications in the gills of a marine teleost (Thalassoma pavo) after acute exposure (48, 96, 192 h) to three lead concentrations. We showed that pathological alterations can be detected in all the examined samples. The most common modifications observed were: the curling of the lamellae and the dilation of their apical tips, the lamellar edema, the proliferation and the hypertrophy of CCs, the progressive epithelial disorganization with detachment of the epithelium from connective tissue. This study also demonstrates that there is a weak influence on the expression pattern of Na+/K+-ATPase and AQP3 biomarker enzymes while high metallothioneins expression has been observed. The described alterations may adversely affect gas exchange and ionic balance, with a long chain of cascading effects. This is the first evidence of the effects exerted by lead on gills of seawater fishes that highlights the harmful properties of this metal, even at low concentration. [ABSTRACT FROM AUTHOR]