Fish can change their skin and eye colour for background matching and signalling. Males of Gasterosteus aculeatus develop ornamental blue eyes and a red jaw during the reproductive season, colours ...that are further enhanced during courtship. Here, the effects of different hormones on physiological colour changes in the eyes and jaws of male and female G. aculeatus were investigated in vitro. In an in vivo experiment, G. aculeatus were injected with a receptor blocker of a pivotal hormone (noradrenaline) that controls colour change. In males, noradrenaline had aggregating effects on melanophore and erythrophore pigments resulting in blue eyes and a pale jaw, whereas melanocyte‐concentrating hormone (MCH) and melatonin resulted in a pale jaw only. When noradrenalin was combined with melanocyte stimulating hormone (MSH) or prolactin, the jaw became red, while the eyes remained blue. In vivo injection of yohimbine, an alpha‐2 adrenoreceptor blocker, resulted in dispersion of melanophore pigment in the eyes and inhibited the blue colouration. Altogether, the data suggest that noradrenalin has a pivotal role in the short‐term enhancement of the ornamental colouration of male G. aculeatus, potentially together with MSH or prolactin. This study also found a sex difference in the response to MCH, prolactin and melatonin, which may result from different appearance strategies in males, versus the more cryptic females.
Genotoxic analyses are commonly used in ecotoxicological studies as early biomarkers to investigate the potential effects of environmental contaminants on biological models. Several pollutants can ...induce DNA damage and, therefore, counting micronuclei and other nuclear abnormalities are efficient tools to evaluate genotoxicity. Some pollutants such as 4-nonylphenol (NP), a detergent used mainly in industries, and Cyproterone Acetate (CPA), an antiandrogenic medicine, have already shown genotoxic effects on some vertebrates. However, although amphibians are considered bioindicators of environmental quality and their populations are declining worldwide, the effects of these compounds on anurans are not yet known and, therefore, we believe that it is important to investigate such effects on anurans. Since water contamination is one of the ultimate causes of amphibian decline, ecotoxicological studies are important to discuss the appropriate solutions to avoid species extinction. Thus, this study investigates the genotoxic effects on Rana catesbeiana tadpoles and juveniles after being exposed to 1, 10 and 100 μg/L NP and 0.025, 0.25 and 2.5 ng/L CPA, by counting the nuclear abnormalities after exposure. The laboratory experiments lasted 28 days. The experimental conditions were the same except for the water volume since tadpoles and juveniles exhibit different habits at different developmental stages. Compared to juveniles, tadpoles were more susceptible to both compounds as indicated by the increased nuclear abnormalities observed in the highest NP concentration and all tested CPA concentrations. The juveniles, on the other hand, responded only to the two highest CPA concentrations. We concluded that CPA, even at very low concentrations, is extremely harmful to both anuran developmental stages and, particularly, to tadpoles. The significant effects observed on tadpoles is an important outcome of this study since 100 μg/L or higher NP concentrations are frequently detected in the environment.
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•Tadpoles are more susceptible than juveniles to genotoxic effects of contaminants.•Cyproterone Acetate increase nuclear abnormalities in both life stages.•Only in tadpoles occurred high incidence of apoptotic cells, indicating severe toxicity.•Nonylphenol increased nuclear abnormalities only in tadpoles, at the highest dose (100 μg/L).
This study emphasizes the importance of knowing how anurans in different developmental stages respond to the genotoxic effects of pollutants such as NP and CPA when exposed to environmentally relevant doses.
The environment receives about 2.7 kg.ha-1 annually of pesticides, used in crop production. Pesticides may have a negative impact on environmental biodiversity and potentially induce physiological ...effects on non-target species. Advances in technology and nanocarrier systems for agrochemicals led to new alternatives to minimize these impacts, such as nanopesticides, considered more efficient, safe and sustainable. However, it is important to evaluate the risk potential, action and toxicity of nanopesticides in aquatic and terrestrial organisms. This study aims to evaluate genotoxic and hematological biomarkers in bullfrog tadpoles (Lithobates catesbeianus) submitted to acute exposure (48 h) to pyrethrum extract (PYR) and solid lipid nanoparticles loaded with PYR. Results showed increased number of leukocytes during acute exposure, specifically eosinophils in nanoparticle-exposed groups, and basophil in PYR-exposed group. Hematological analysis showed that PYR encapsulated in nanoparticles significantly increased the erythrocyte number compared to the other exposed groups. Data from the comet assay indicated an increase in frequency of the classes that correspond to more severe DNA damages in exposed groups, being that the PYR-exposed group showed a high frequency of class-4 DNA damage. Moreover, erythrocyte nuclear abnormalities were triggered by short-time exposure in all treatments, which showed effects significantly higher than the control group. These results showed genotoxic responses in tadpoles, which could trigger cell death pathways. Concluding, these analyses are important for applications in assessment of contaminated aquatic environments and their biomonitoring, which will evaluate the potential toxicity of xenobiotics, for example, the nanoparticles and pyrethrum extract in frog species. However, further studies are needed to better understand the effects of nanopesticides and botanical insecticides on non-target organisms, in order to contribute to regulatory aspects of future uses for these systems.
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The use of nanoencapsulation of botanical compounds it is extremely important aiming applications in pest control, however before its use the study of toxicity in non-target organisms are crucial.
Imazethapyr is an herbicide that is used in a variety of crops worldwide, including soybean and corn. The aim of the present study was to evaluate the biomarkers responses of adult
Leptodactylus ...latinasus
exposed to the formulation Pivot
®
H (10.59% imazethapyr) in the laboratory at concentrations and under conditions that simulate two potential field exposure scenarios: an immersion in field runoff (Scenario 1: 10 mg/L) and a direct exposure to the droplets emitted by spray noozles (Scenario 2: 1000 mg/L). In both scenarios, the experimental procedure involved completely immersing the frogs over a period of 15 s. Different endpoints were evaluated at several ecotoxicological levels 48 and 96 h after the herbicide exposure. These included individual (biometric indices and behavior alterations), histological (liver pigments and lesions), biochemical (catalase, glutathione system and cholinesterase activities) and genotoxic effects (micronuclei induction and nuclear abnormalities). Forty-eight hours after imazethapyr exposure, frogs submitted to Scenario 1 presented an inhibition of liver glutathione-S-transferase activity, whereas histological alterations and increased hepatic cholinesterase levels were observed in frogs exposed under Scenario 2. Ninety-six hours after exposure to the imazethapyr formulation, frogs from the Scenario 1 treatment presented a decrease in liver melanin and hemosiderin, increased hepatic catalase activity and micronuclei induction. For their part, frogs exposed to Scenario 2 presented a decrease in the hepatosomatic index, an increase in liver alterations, melanin reduction and micronuclei induction. The multivariate analysis enables correlations to be made between biomarkers of different organizational level in exposed anurans. Our result indicates that real exposure to imazethapyr formulations under field conditions may pose a risk to
Leptodactylus latinasus
populations living in the agroecosystems.
Anurans can be naturally infected by the bacterium Escherichia coli (Migula, 1895) Castellani and Chalmers, 1919, which contain lipopolysaccharides (LPS) in their external membrane. LPS affects ...reproductive functions in mammals and extracutaneous pigmentary system of anurans. Besides the functional gonad, bufonid amphibians have an undeveloped female organ (Bidder’s organ), whose function is poorly known. We aimed to investigate the effects of LPS on testis and Bidder’s organ germ cells and on liver pigmentation in the toad Rhinella diptycha (Cope, 1862). Animals were inoculated with 0.1 mL of saline solution (control) or LPS solution (18 mg/kg) and then euthanized after 24 or 48 h. The organs were processed for histology and then evaluated with morphometric analysis. The LPS decreased the area of bundle spermatozoa and increased lumen spermatozoa, while in Bidder’s organ, the number of degenerating oocytes decreased. Liver melanin increased after 24 h and decreased after 48 h. Our results suggest that LPS delays the release of spermatozoa, possibly due to alterations in serum levels of testosterone and (or) gonadotropins, which may also explain fewer degrading cells in Bidder’s organ. Increased melanin in the liver was expected due to the bactericidal role of this pigment. Thus, LPS affected reproductive organs and induced cytoprotective responses in the liver of amphibians.
Bufonids have an organ that produces female germ cells in both sexes, known as the Bidder’s organ (BO). In males, BO is located in the anterior pole of the testis and it has been compared to a ...rudimentary ovary. It has been demonstrated that in some species the bidderian follicles can accumulate vitellogenin in males, while in other species, the development of follicles is inhibited by the differentiation of the corresponding gonad. This study describes the anatomical, histochemical and ultrastructural aspects of the BO in males of the neotropical frog Rhinella schneideri during the breeding season. A topographic model has also been built using three-dimensional (3D) reconstruction. BO has an irregular shape with lobes varying in size and number. There is no physical barrier between the BO and male gonads and, for this reason, female cells are in intimate association with seminiferous locules. Histologically, two distinct regions are observed in the BO: the cortex, and medulla. In the cortex, bidderian oocytes are surrounded by follicle cells forming bidderian follicles, which are in pre-vitellogenic stage. The ooplasm of bidderian oocytes is rich in cytoplasmic organelles. Microvilosities are formed in the oolemma, where the follicular cells are juxtaposed with oocytes, and amorphous extracellular material is deposited. Lipofuscin and myelin bodies occur in the medulla as a result of the cellular degradation. Pigmented cells were also detected in the medullar region. The oogonias observed in the BO periphery, and the significant amount of degenerating oocytes in the cortex, showed the renewal capacity of BO cells in R. schneideri males. The BO anatomical pattern in R. schneideri is similar to that observed for most species of bufonids. This work describes for the first time specific aspects related to the morphological description with emphasis on architecture, morphometry and histochemistry.
Amphibians have been facing a pandemic caused by the deadly fungus Batrachochytrium dendrobatidis (Bd). Although studies have elucidated cutaneous and homeostatic disturbances, it is still unknown if ...the hepatic function can be affected or if hepatic effects differ among host species. Thus, we evaluated the effects of an experimental Bd infection on the liver (histopathology and the hepatosomatic index) of 2 anuran species (Xenopus laevis and Physalaemus albonotatus) with different susceptibilities to Bd infection and compared them to uninfected controls. Bd infection increased the melanomacrophage cell area and induced leukocyte infiltration in both species. The effects were more pronounced in the sensitive species, P. albonotatus, which showed severe reduction in glycogen stores and liver atrophy, due to energetic imbalance. Hepatocytes of P. albonotatus also showed ballooning degeneration (vacuolization), which could lead to cell death and liver failure. Our results provide evidence that although the sensitive species showed more severe effects, the tolerant species also had hepatic responses to the infection. These findings indicate that hepatic function can play an important role in detoxification and in immune responses to chytridiomycosis, and that it may be used as a new biomarker of health status in chytrid infections.
ABSTRACT The Gymnotus inaequilabiatus is a Neotropical fish widely distributed in marginal areas of bays. The aim of this study was to describe the main histological and histopathological traits in ...the head and exocrine kidney. Here, histometric and structural density techniques were associated with renosomatic index (RSI). The kidney was processed for light microscopy. Lipofuscin and hemosiderin content were visually estimated in the melonomacrophages centers (MMCs). All the biometric body variables were correlated with RSI, especially the kidney weight and gross lesions count. The general architecture of head and exocrine kidney was similar to that described for other teleost species. MMCs were prevalent in both portions and correlated with RSI in the head and exocrine kidney. Granulomatous structures were often observed in both portions; however, they were associated only in the exocrine kidney with RSI. Of all the structures hystometrically estimated, only proximal tubular diameter and thickness, and distal tubular thickness were correlated to renosomatic index. The RSI is an useful biometric variable that represent some physiological and morphological characteristics of kidney in G. inaequilabiatus. These findings may be used in future studies to evaluate the effects of environmental stressors on the renal adaptative physiological process.
RESUMO Gymnotus inaequilabiatus é um peixe neotropical amplamente distribuído em áreas marginais de baías. O objetivo deste estudo foi descrever características anatômicas, histológicas e histopatológicas no rim cefálico e exócrino. Análises histométricas e a densidade volumétrica estrutural foram associadas ao índice renossomático (IRS). Fragmentos de ambos tecidos foram processados para análise e microscopia de campo claro. O conteúdo de lipofuscina e hemossiderina foi estimado visualmente nos centros de melanomacrófagos (CMMs). Todas as variáveis corporais biométricas foram correlacionadas com o IRS, principalmente o peso renal e a contagem de lesões superficiais. A arquitetura geral do rim cefálico e exócrino foi semelhante à descrita para outras espécies de teleósteos. Os CMMs foram frequentes em ambas as porções e correlacionaram-se com o IRS. Estruturas granulomatosas foram frequentemente observadas em ambas porções; no entanto, foram associadas ao IRS apenas no rim exócrino. De todas as estruturas estimadas histometricamente, apenas o diâmetro e espessura dos túbulos proximais e distais correlacionaram-se ao IRS. Este índice mostrou-se uma variável útil associada a características fisiológicas e morfológicas do rim de G. inaequilabiatus. Esses achados podem ser empregados em futuros estudos a fim de avaliar efeitos ambientais bem como processos adaptativos fisiológicos.
The spleen is a lymphoid organ associated with defense mechanisms in anurans, and also it has pigmented cells. Melanomacrophages (MMs) are melanin-containing cells, which originated from ...hematopoietic stem cells and are found in hematopoietic organs. Melanin has bactericide and cytoprotective actions against free radicals. Furthermore, the α-melanocyte stimulating hormone (MSH) induces dispersion of melanosomes in melanocytes, besides having an anti-inflammatory action. Here, we describe the spleen morphology of Physalaemus nattereri and the response of splenic melanomacrophages to the α-MSH hormone. Animals were treated with α-MSH for 2, 6, 12, 24 and 48 h. Then, we measured the amount of melanin, lipofuscin and hemosiderin in each treatment. The spleen of P. nattereri is ovoid, and a connective tissue capsule covers the organ externally. There are no septa and the stroma is reduced. The parenchyma has two regions slightly separated from each other: white and red pulps. MMs occur in the red pulp. The α-MSH increased the volume of lipofuscin and hemosiderin in MMs after 6 h, but not melanin. Thus, the α-MSH altered only metabolic substances in splenic melanomacrophages, but not melanin, which usually is responsive to this hormone in hepatic MMs. Also, the description of the spleen morphology can help future comparative morphological and evolutionary studies on spleen morphology of vertebrates.
Amphibians have melanin-containing cells in visceral organs that are similar to pigmentary cells from the epidermis. Both of them are derived from the ectodermal neural crest. Epidermal cells respond ...to α-melanocyte stimulating hormone (α-MSH), which is associated to the dispersion of melanin granules within melanocytes. Therefore, our aim was to test whether a non-degradable analogue of the α-MSH changes the superficial colouration of organs of Eupemphix nattereri. The hormone rapidly increases (within 12 hours) the colouration on the surface of the pericardium, heart, testes, nerves of the lumbar plexus, and lumbosacral parietal peritoneum. Colouration increased late (after 24 hours) in the kidneys and mesentery following hormone administration. However, this hormone did not change colouration of intestine, rectum and lungs. Our findings could be explained by the similarities between epidermal and visceral melanocytes, since both cells have a common embryonic origin. Furthermore, the increase in visceral colouration may be related to the dispersion of melanosomes within melanocytes, which causes the darkening of organs. Our results demonstrate for the first time that the visceral colouration is responsive, thereby altering the internal pattern of organs' colouration in anurans.
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