Liver histopathology in the cane toad, Rhinella marina (Amphibia: Bufonidae), induced by Ortleppascaris sp. larvae (Nematoda: Ascarididae)

Estrogen contamination increases vulnerability of amphibians to the deadly chytrid fungus

Aquatic contaminants and infectious diseases are among the major drivers of global amphibian declines. However, the interaction of these factors is poorly explored and could better explain the amphibian crisis. We exposed males and females of the Brazilian Cururu Toad, Rhinella icterica, to an environmentally relevant concentration of the estrogen 17-alpha-ethinylestradiol (an emerging contaminant) and to the chytrid infection (Batrachochytrium dendrobatidis), in their combined and isolated forms, and the ecotoxicity was determined by multiple biomarkers: cutaneous, hematological, cardiac, hepatic, and gonadal analysis. Our results showed that Cururu toads had many physiological alterations in response to the chytrid infection, including the appearance of cutaneous Langerhans's cells, increased blood leukocytes, increased heart contraction force and tachycardia, increased hepatic melanomacrophage cells, which in turn led to gonadal atrophy. The estrogen, in turn, increased the susceptibility of the toads to the chytrid infection (higher Bd loads) and maximized the deleterious effects of the pathogen: reducing leukocytes, decreasing the contraction force, and causing greater tachycardia, increasing hepatic melanomacrophage cells, and leading to greater gonadal atrophy, which were more extreme in females. The exposure to estrogen also revealed important toxicodynamic pathways of this toxicant, as shown by the immunosuppression of exposed animals, and the induction of the first stages of feminization in males, which corroborates that the synthetic estrogen acts as an endocrine disruptor. Such an intricate relationship is unprecedented and reinforces the importance of studying the serious consequences that multiple environmental stressors can cause to aquatic populations.

What coloration brings: Implications of background adaptation to oxidative stress in anurans

BACKGROUND

Urban development results in habitat destruction, affecting populations of amphibians, the most fragile group of vertebrates. With changes in the environment, these animals become more exposed to light and predators. To enhance their chances of survival, they display plasticity of body coloration. Aside from adaptive benefits, animals exhibiting background matching meet the energetic costs and restrictions of changing body tones. To study the physiological consequences of Hyla arborea tadpole adaptation to background color, we followed oxidative stress parameters after rearing larvae on a constant background (black/white) and after changing the background color.

RESULTS

Larvae cultivated for 20 days on constant substrate color exhibited differences in body coloration but without differences in lipid peroxidation (LPO) concentration between dark and pale individuals, suggesting that coloration investment during this period did not induce higher oxidative damage in darker tadpoles. Prolonged exposure of larvae (37 days) to a dark habitat increased antioxidative system defense and LPO concentrations, compared to animals reared permanently in the white surroundings. The positive correlation of oxidative damage with color intensity of individuals points to the physiological consequences of higher investment in the number of pigment cells necessary for dark pigmentation. In individuals faced with non-matching background and change in body coloration, defense system declined and LPO occurred relative to individuals cultivated in white habitat.

CONCLUSION

Here, we have pointed to consequences related to background matching and stress that amphibians experienced during chromatic adaptations. Background color change causes a complex physiological response affecting the antioxidative defense parameters. This investigation elucidates the accompanying cost of amphibians' adjustment to an altered environment.

Short-term effects of α-melanocyte-stimulating hormone in three distinct melanin-pigmented cell types of Anura

Ectothermic animals present melanin-containing cells in their integument and viscera. Besides cutaneous melanophores, amphibians have melanomacrophages in the hepatic parenchyma and melanocytes in the viscera, which are also present in their testicular stroma. The native melanocyte stimulating hormone (α-MSH) is the main hormone that modulates the color change in melanophores. However, we still know too little about how the α-MSH acts in vivo on visceral melanin-containing cells. In this study, we collected 30 adult males of Physalaemus nattereri (Anura, Leptodactylidae) to evaluate the short-term effects of α-MSH on melanophores, melanocytes and melanomacrophages under light microscopy. For this, we injected 0.05 ml of a single intraperitoneal dose containing 2.5x10-7 mmol/10g of α-MSH, diluted in ringer solution, in five experimental groups with five individuals each one. The different groups were analyzed after 1, 3, 6, 12 and 24h. The control group with five other individuals received only 0.05 ml of ringer solution. The skin pigmentation increased quickly after animals received the hormone α-MSH with the consequent darkening of the body (body darkness). Melanophores, melanocytes and melanomacrophages responded similarly to the test, with an increase in the area containing melanin. However, melanophores and melanomacrophages reached their darkest pigmentation in a shorter period of time in comparison to the testicular melanocytes, probably due to specific metabolic characteristics of each organ. Thus, we verified that the three types of cells, although present in different organs, are responsive to the native hormone α-MSH, which enables us to treat them as a pigmentary system.

Helminth fauna and histopathology associated with parasitic infections in Phrynops geoffroanus (Schweigger, 1812) (Testudines, Chelidae) in a Brazilian river subjected to anthropogenic activities

The objective of this study was to determine the structure of the helminth fauna and identify the macroscopic and histopathological alterations associated with parasitic infections in Phrynops geoffroanus. Freshwater turtles of both sexes were captured during the dry and rainy seasons in four municipalities along the Capibaribe River. The study included 63 animals, of which 79.37% (50/63) were parasitized by one or more helminths. In total, 933 helminths of seven taxa were recovered: Serpinema monospiculatus, Spiroxys figueiredoi, Nematophila grandis, Polystomoides brasiliensis, Cheloniodiplostomum testudinis, Telorchis birabeni, and Prionosomoides scalaris. Monogeneans and digenetic trematodes were more sensitive to environmental pressures, since the prevalences varied significantly between areas. Nematodes proved to be more resistant to environmental pressure and caused severe injuries to their hosts: nodules in the stomach and small intestine, adhesions in the liver capsule, and pulmonary emphysema. Parasitic granulomas were recorded at the infection sites and in the lungs and liver, the latter caused by migration of S. figueiredoi larvae. This is the first record of P. brasiliensis, N. grandis, C. testudinis, and T. birabeni parasitizing P. geoffroanus in the state of Pernambuco. Histopathology proved to be an important tool for studies on the impact of parasites at the individual, population, and ecosystem levels. Considering the use of the Capibaribe River for public water supply, fishing, and other activities, within the One Health perspective, this study demonstrates that the anthropogenic impact affects parasites and their hosts, in addition to the human population that uses this ecosystem.

Differential liver histopathological responses to amphibian chytrid infection

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.

Effects of glyphosate and its commercial formulation, Roundup® Ultramax, on liver histology of tadpoles of the neotropical frog, Leptodactylus latrans (amphibia: Anura)

In the last years, the agricultural expansion has led to an increased use of pesticides, with glyphosate as the most widely used worldwide. This is also the situation in Argentina, where glyphosate formulations are the most commercialized herbicides. It is known that glyphosate formulations are much more toxic than the active ingredient, and this difference in toxicity can be attributed to the adjuvants present in the formula. In this context, the aim of the present study was to evaluate and compare sub-lethal histological effects of the glyphosate formulation Roundup Ultramax and glyphosate active ingredient on Leptodactylus latrans tadpoles at Gosner-stage 36. Semi-static bioassays were performed using 96 h of exposure with Roundup Ultramax formulation (RU; 0.37-5.25 mg a.e./L), glyphosate (GLY; 3-300 mg/L), and a control group. RU exposure showed an increment in the melanomacrophagic cells (MMc) and melanomacrophagic centers (MMCs) from 0.37 mg a.e./L. GLY exposure showed a significant increment in the number of MMc from 15 mg/L, and of MMCs from 3 mg/L. Also, histopathological lesions were observed in the liver of tadpoles exposed to both, GLY and RU. These lesions included: lipidosis and hepatic congestion, but only RU showed significant differences respect to control, with a LOEC value of 2.22 mg a.e./L for both effects. In sum, this study represents the first evidence of adverse effects of glyphosate and RU formulation on the liver of anuran larvae at concentrations frequently found in the environment.

Morphological characterization of Eustrongylides sp. larvae (Nematoda, Dioctophymatoidea) parasite of Rhinella marina (Amphibia: Bufonidae) from Eastern Amazonia

Absctract Eustrongylides spp. nematodes have birds as final hosts and uses other vertebrates as intermediate/paratenic host (fish, amphibians and reptiles) and have zoonotic potential. In amphibians, the larvae may be located in the subcutaneous tissues, liver and mesentery, between the muscle fibres, especially in the lower limbs. Rhinella marina, which is widely observed in Brazil, has exhibited complex diversity in its helminth fauna, reflecting the unique habitat of the Amazon biome. For the first time, this study describes the morphological aspects of third-stage larvae of Eustrongylides sp. in Rhinella marina from Santa Cruz do Ararí, Marajó Archipelago, Eastern Amazonia, using light and scanning electron microscopy.

Characterization of the complete mitochondrial genome of Ortleppascaris sinensis (Nematoda: Heterocheilidae) and comparative mitogenomic analysis of eighteen Ascaridida nematodes

Ortleppascaris sinensis (Nematoda: Ascaridida) is a dominant intestinal nematode of the captive Chinese alligator. However, the epidemiology, molecular ecology and population genetics of this parasite remain largely unexplored. In this study, the complete mitochondrial (mt) genome sequence of O. sinensis was first determined using a polymerase chain reaction (PCR)-based primer-walking strategy, and this is also the first sequencing of the complete mitochondrial genome of a member of the genus Ortleppascaris. The circular mitochondrial genome (13,828 bp) of O. sinensis contained 12 protein-coding, 22 transfer RNA and 2 ribosomal RNA genes, but lacked the ATP synthetase subunit 8 gene. Finally, phylogenetic analysis of mtDNAs indicated that the genus Ortleppascaris should be attributed to the family Heterocheilidae. It is necessary to sequence more mtNDAs of Ortleppascaris nematodes in the future to test and confirm our conclusion. The complete mitochondrial genome sequence of O. sinensis reported here should contribute to molecular diagnosis, epidemiological investigations and ecological studies of O. sinensis and other related Ascaridida nematodes.

Ortleppascaris sp. and your host Rhinella marina: A proteomic view into a nematode-amphibian relationship

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Rhinella marina is a synanthropic amphibian that offers great possibilities for the study of parasite–host relations.

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A complex protein profile, including neuroendocrine proteins indicating intense stress in the liver of the host.

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Important aspects of the host’s immune response plasticity are shown.

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This study contributes to knowledge of the biochemical aspects of the helminth–host interface.

The success of the helminth–host relationship depends on a biochemical molecular arsenal. Perhaps the proteome is the largest and most important set of this weaponry, in which the proteins have a crucial role in vital processes to the parasite/host relationship, from basic metabolism and energy production to complex immune responses. Nowadays, the bioproducts expressed by the parasites are under the “spotlight” of immunoassays and biochemical analysis in helminthology, especially in proteomic analysis, which has provided valuable information about the physiology of the infecting agent. Looking into this point of view, why not turn to the infected agent as well? This study characterised the proteomic profile of fluid-filled fibrous cysts of encapsulated Ortleppascaris sp. larvae in the hepatic parenchyma of their intermediate host, the amphibian Rhinella marina. The proteins were separated by two-dimensional electrophoresis and identified by MS with the aid of Peptide Mass Fingerprint. A total of 54 molecules were analysed in this system, revealing a complex protein profile with molecules related to basic metabolic processes of the parasite, energy production, oxi-reduction and oxidative stress processes as well as molecules related to the host response. This study contributes to proteomic studies of protein markers of the development, infectivity, virulence and co-existence of helminths and their hosts.

Histopathologic aspects in Plagioscion squamosissimus (HECKEL, 1940) induced by Neoechinorhynchus veropesoi, metacestodes and anisakidae juveniles

Plagioscion squamosissimus (Heckel 1840), a fish endemic to the Amazon Basin and commonly known as the “silver croaker”, plays an important role in the ecology and economy of Pará State, Brazil. Knowledge of host-parasite relationships is important to understanding the role of parasites in the control of natural host populations. This work describes histopathological aspects caused by several common intestinal parasites found during a helminthological survey of fish in northern Brazil. We observed a high prevalence of helminth infection, especially by J3 nematode juveniles of the family Anisakidae and metacestodes of the family Protocephalidae (both with 100% prevalence). An external capsule surrounded each juvenile with numerous juveniles inside sac-like structures formed of connective tissue. Inflammation was observed to be caused by infection of metacestodes, reaching the intestinal muscularis mucosa. Neoechinorhynchus veropesoi (38% prevalence) was found in the small intestine of P. squamosissimus, invading the mucosa, submucosa, and internal muscularis of the intestine causing intense inflammation. Histopathology of host-parasite relationships in fish has been rare, and the pathology of parasites in P. squamosissimus is described herein.

Proteomic profile of Ortleppascaris sp.: A helminth parasite of Rhinella marina in the Amazonian region

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We have characterized somatic proteins of a helminth parasite of a synanthropic amphibian from Amazonian region.

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As37, an immunoreactive antigen considered a target for antihelminthic vaccines was found.

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We found virulence factors which are evolutionarily conserved and are potential factors for anti-parasitic interventions.

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This study brings a new approach for host–parasite research by using a amphibian as an animal model.

Ortleppascaris sp. is a helminth that, in its larval stage, infects the liver parenchyma of the amphibian Rhinella marina, resulting in severe physiological and pathological changes. This study used a proteomic approach to determine the overall profile of proteins expressed in a somatic extract from the nematodes to investigate the relationship between the parasite and its host. A total of 60 abundant proteins were selected from the two-dimensional electrophoresis, identified by peptide mass fingerprinting, and grouped based on their Gene Ontology by the biological processes in which they are potentially involved. Important helminthic derivatives, such as the immunoreactive As37 antigen, guanylyl cyclases, proteolytic enzymes, and other proteins conserved among different parasites, were identified through homology. This study represents a new approach to helminth-related proteomic studies using an amphibian animal model. Furthermore, this study identified protein markers that are important to the host–parasite relationship and the viability, development, infectivity, and virulence of helminths.