Yellow grub disease is a parasite infection, caused by Clinostomum spp. Metacercariae and affecting axial muscles and internal organs of freshwater fish. Killifishes live in seasonal ponds and are short-lived; in the Neotropical region they are among the most vulnerable vertebrates. The current study analyzes the possible injury and inflammatory reaction caused by parasitic infection with Clinostomum spp. metacercariae in testes, ovaries, liver, intestine and mesentery in the seasonal killifishes Trigonectes aplocheiloides and Titanolebias monstrosus. Apparently, this parasite could migrate through the circulatory system to different organs, since a cercaria was found in the lumen of a hepatic sinusoid. In all organs the inflammatory response showed dilated, congested vascular areas and infiltration of numerous inflammatory cells, mainly composed of lymphocytes, eosinophilic granular cells and macrophages. However, the most affected organs were the pancreas, ovaries and testes. In these organs, severe pancreatitis with degranulation of the pancreatic acini, scarce ovarian follicles and spermatocysts dilated with few or no seminiferous cells were observed. In seasonal killifish, yellow grub disease could cause low fertility rates or even sterility by reducing or impairing their reproductive capacity. Therefore, this type of parasitism has a considerable impact on the perpetuation of this species due to the short periods they have to breed before their habitats dry out.

Introduction: The frequent use of pesticides is currently considered a cause of environmental pollution due to the high rate of entry of these substances into agroecosystems. This constitutes a risk for the species that inhabit these ecosystems, in particular anurans whose characteristics make them prone to exposure to and interaction with environmental pollutants. Objective: To report the occurrence of abnormalities in larvae of the common toad Rhinella arenarum inhabiting ponds surrounded by agroecosystems. Methods: In two consecutive springs (2015 and 2016), reproductive events of common toads were monitored in temporary pond systems in agricultural and non-agricultural areas, located near the city of La Plata (Buenos Aires, Argentina). The physicochemical parameters of the ponds were measured, and the stage of each reproductive event was recorded, such as the numbers of adult toads, amplexus and clutches. In the laboratory, the larvae were measured and photographed, their stage of development was recorded, and their morphology was examined under a stereomicroscope. Representative samples (normal and abnormal) from each pond studied were processed for histopathological analysis. Results: In the field studies carried out on a population of R. arenarum collected in an agroecosystem, a lower number of reproductive adults and clutches were observed in relation to the population of a non-agricultural pond. A total of 1 910 larvae were collected: 529 and 1 381 larvae from ponds located in non-agricultural and agricultural areas, respectively. Larvae from the agroecosystem showed two types of abnormalities: severe tail flexure and abdominal bloating. In addition, five degrees of severity could be determined in relation to abdominal bloating. Conclusions: This work reports the high frequency and severity of abnormalities observed in the early stages of R. arenarum larvae living within an agroecosystem, providing evidence of the negative impact that agricultural activities cause on aquatic ecosystems surrounded by farming areas.

Cheirodon interruptus is a small characid widely distributed in South America and frequently used as bait. The harvesting of wild fish to supply the market has a significant environmental impact. The effect of photoperiod and temperature on ovarian maturation is assessed to evaluate its potential to manipulate reproduction. Fish were exposed to three treatments (in triplicate): (light hours: L/temperature: degrees C) 12 L/20 degrees C, 24 L/20-25 degrees C, and 9.8-13.3 L/20-25 degrees C. Gonadosomatic index (GSI), plasma estradiol (E2), oocyte diameter, and vitellogenic oocyte percentage were estimated. Mean GSI, E2 values, oocyte diameter, and percentage were significantly higher in 9.8-13.3 L/20-25 degrees C than in the other treatments, indicating ovarian maturation. In turn, these values were minimal in the 24 L/20-25 degrees C treatment, revealing ovarian regression. These results suggest that in C. interruptus, the photoperiod is the primary driver of gonadal maturation and the temperature plays a secondary role. This study demonstrated that manipulation of ovarian development is possible through the design of photothermal regimes based on the winter-spring transition.

In viviparous teleosts, intraovarian gestation occurs intrafollicularly, as in poeciliids, or intraluminally, as in goodeids and anablepids. Furthermore, there are two different forms of embryonic nutrition: lecithotrophy and matrotrophy; depending on the species, these can be exclusive or coexist during gestation. In matrotrophic species, nutrients are transmitted from the mother to the embryo and are especially important in species with intraluminal gestation. Jenynsia lineata is a South American viviparous teleost with intraluminal gestation, characterized by eggs with scarce yolk, which is resorbed when embryos are 6 mm long, thus developing a branchial placenta. Using histological, histochemical, and immunohistochemical techniques, the present study describes the characteristics and changes of the ovarian mucosa in J. lineata during gestational and nongestational phases, and analyzes the embryonic pharyngeal epithelium in the branchial placenta. The ovaries of 30 adult female specimens were processed using histological techniques and stained with hematoxylin-eosin, Masson's trichrome, and Alcian Blue pH 2.5/periodic acid Schiff reagent. To detect cell proliferation, we used antiproliferating cell nuclear antigen antibody. In nonpregnant females, eosinophilic granular cells (EGCs) and lymphocytes were identified in the lamina propria of the tunica mucosa, and melanomacrophage centers (MMCs) and fibroblasts were identified adjacent to tissue debris in the ovarian folds'. In the cellular debris, an embryo in resorption was observed. In pregnant females, the ovarian mucosa has thin vascularization branches entering the opercular chamber of the embryos, in close contact with the forming gill processes, thereby establishing a branchial placenta. Active cell replacement was observed in these ovarian branches. The identification of fibroblasts, lymphocytes, EGCs, and MMCs adjacent to tissue debris could indicate that these cell types are involved in the embryonic resorption process. Considering the new data obtained in this study on the branchial placenta of J. lineata, we conclude that cell proliferation could be involved in the development of maternal-embryonic interaction.

In aquaculture farms, incubation is a one crucial stage, as frequently shows high percentage of mortality. In fish and amphibians, egg oomycosis is a common infection during the early stages of embryonic development. Infection is usually promoted by unfertilized or damaged eggs that provide a medium for the zoospores to establish and grow, resulting in colonization and spread of the infection to nearby viable eggs. Numerous essential oils have been shown to have anti-oomycotic activity and to inhibit production and spore germination of Oomycetes species of the order Saprolegniales

In aquaculture, the intensification of cultures of aquatic organisms to obtain large volumes of production leads to the establishment of an environment that generates stress. These conditions weaken the immune system of these organisms, which increases the spread of diseases and generates great economic losses. One of the factors responsible for the mortality of cultivated species is fungal infections. In farms, the handling procedures that are carried out during the incubation, rearing and fattening stages are important for the final yield. One of the crucial stages is incubation as there is usually a high degree of mortality at this stage. Several studies have been conducted using chemical products for the prophylaxis, disinfection and control of mycoses. This use has caused the resistance of pathogens and the accumulation of residues in the tissues of aquatic organisms or in the environment. For this reason, other forms of therapy that are more profitable and with less deleterious effects on the environment are being developed. Phytotherapy emerges as an alternative due to its proven action against diseases of diverse etiology. This review compiles and discusses the existing bibliography on the most common fungal diseases in fish, amphibians and crustaceans, emphasizing those that affect the eggs of cultures organisms and analyzing the natural antifungal agents used in vitro and in vivo in aquaculture.

En acuicultura, la intensificación de los cultivos para obtener grandes volúmenes de producción conlleva a establecer un ambiente que genera estrés en los organismos. Estas condiciones debilitan su sistema inmune lo que incrementa la propagación de enfermedades y generan grandes pérdidas económicas. Uno de los factores responsables de la mortalidad de las especies cultivadas son las infecciones fúngicas. En las granjas de cultivo, los procedimientos de manejo que se realizan durante las etapas de incubación, cría y engorde son importantes para el rendimiento final del producto. Una de las etapas cruciales es la incubación, ya que en esta etapa suele haber un alto grado de mortalidad. Se han realizado diversos estudios que utilizan productos químicos para la profilaxis, desinfección y control de las micosis. Esta utilización ha provocado la resistencia de los agentes patógenos y la acumulación de residuos en los tejidos de los organismos acuáticos o en el ambiente. Por ello, se están desarrollando otras formas de terapia más rentables y con menos efectos deletéreos sobre el medio ambiente. La fitoterapia surge como una alternativa por su comprobada acción ante enfermedades de diversa etiología. En esta revisión se compila y discute la bibliografía existente sobre las enfermedades fúngicas más comunes en los peces, anfibios y crustáceos, se enfatiza en las que afectan a las ovas de los organismos en cultivo y se analizan los antimicóticos naturales utilizados in vitro e in vivo en acuicultura.

Lebranche mullet, Mugil liza , is an important economic resource and has been recommended for aquaculture in South America. Also, this is the only mullet that breeds in Argentina. In the course of our routine investigations on the parasitic fauna of fishes from brackish waters of Samborombón Bay, Buenos Aires province, an infection of acanthocephalan worms, identified as Floridosentis mugilis was observed in juvenile lebranche mullets. These parasites were attached deeply into the intestinal wall but without piercing it. In this study we analysed the intestinal damage that F . mugilis inflicts on their hosts through the evaluation of histological sections. In the pathological analysis we observed that these parasites cause a non-specific cellular response that leads to the degranulation of eosinophilic granular cells and, consequently, the formation of a fibrous core with oedema, vascular congestion, and lymphocytic infiltration.

During embryogenesis, teleost females do not develop Müllerian ducts, which form the oviducts in all other vertebrates. Thus, when they reach sexual maturity they do not have oviducts. In viviparous teleosts, the lack of oviducts means that the development of the embryos occurs as an intraovarian gestation, unique among vertebrates. The ovary is an unpaired hollow organ whose cavity is continuous with the caudal portion, the gonoduct, characterized by the absence of germinal cells, which opens to the exterior at the gonopore. The gonoduct attains essential function as a barrier between the germinal region of the ovary and the exterior during all reproductive stages. This study describes the functional morphology of the gonoduct in the viviparous teleost Cnesterodon decemmaculatus during non‐gestation (previtellogenesis and vitellogenesis) and gestation. The ovaries were processed using histological techniques and stained with hematoxylin–eosin, and periodic acid Schiff. The gonoduct has two regions: cephalic and caudal, and is formed by three histological layers, which are, from inside to the periphery: (a) tunica mucosa; (b) tunica muscularis; and (c) tunica serosa. In the cephalic region there are mucosal folds extending into the lumen and forming a structure similar to a cervix. The histology of the gonoduct indicates essential functions, that is, (a) the control of the luminal diameter in the limit to the germinal region of the ovary by the presence of a cervix; (b) during insemination the gonoduct receives the spermatozoa, may store and transport them to the germinal region; (c) the presence of melano‐macrophage centers indicates support of immunological processes, especially during gestation when these centers increase in size; (d) production of exocrine secretions; and (e) it is the birth canal, internally lined by an ciliated epithelium and surrounded by smooth musclesboth tissues supposedly supporting the birth process.

The Neotropical armoured catfish Corydoras paleatus is a facultative air-breathing teleost commonly exported as ornamental fish. In this species, air breathing enables it to survive and inhabit freshwater environments with low oxygen levels. Therefore, it is important to analyse the gills from a morphological aspect and its dimensions in relation to body mass with reference to aquatic respiration. For that, the gills were analysed using a stereoscopic microscope for morphometric studies, and structural and ultrastructural studies were carried out to compare the four branchial arches. Furthermore, two immunohistochemical techniques were used to locate and identify the presence of a Na+ /K+ pump. The characterization of the potential for cell proliferation of this organ was assessed using an anti-PCNA antibody. The results show that gills of C. paleatus present some characteristics related to its diet and lifestyle, such as the limited development of gill rakers and the abundance of taste buds. In addition, other special features associated with the environment and bimodal breathing were observed: scarce and absent mucous cells (MCs) in the gill filaments and branchial lamellae, respectively, and the localization of mitochondria-rich cells (MRCs) covering the basal third of the branchial lamellae, which reduces the gill respiratory area. A peculiar finding in the gill epithelium of this armoured catfish was the presence of mononuclear cells with sarcomeres similar to myoid cells, whose functional importance should be determined in future studies. Finally, in C. paleatus, the interlamellar space of gill filaments is an important site for cell turnover and ionoregulation; the latter function is also performed by the branchial lamellae.

In the Laboratory of Parasites of Fishes, Crustaceans and Mollusks (CEPAVE), we undertook a parasitological study on three species of fish from the Espinal and Esteros del Iberá ecoregions of Argentina. Clinostomid metacercariae were found parasitizing Characidium rachovii, Crenicichla vittata and Gymnogeophagus balzanii. In this study, we analysed the damage that these parasites inflict on their hosts through the evaluation of histological sections. In addition, Clinostomum metacercariae were identified using morphological characters and DNA barcoding. In the pathological analysis, we observed that muscle tissue was the most affected. The inflammatory response showed vascular congestion areas and infiltration of numerous inflammatory cells, mainly lymphocytes. The molecular and morphological approach supports the presence of three new lineages of clinostomid metacercariae in Argentina. This could lead to the discovery of a high number of lineages or species of Clinostomum from South America.

Giardia sp. is a genus of endoparasite protozoo of the small intestine, responsible for infections generally asymptomatic, especially in children. They can cause acute, sub acute, and chronic diarrheas and duodenal irritation with increment of the mucus and deficiencies in the absorption of liposolubles vitamins. Giardia sp. can inhibit the activity of the pancreatic lipasa causing mal absorption of fats. Their cysts remain viable more than two weeks in humid areas and the way of infection is by ingestion of water or polluted foods with cysts. Studies carried out in the Canadian goose (Branta canadensis) determined the presence of cysts of Giardia sp. in the faecal pellets of these birds, and considering their migratory nature the possible dissemination of the parasite has special interest. Giardia sp.has been also identified in feces of other aquatic birds that are considered reservoirs. The small gallareta (Fulica leucoptera) possesses a wide and profuse distribution in Argentina. It occupies a similar ecological niche of that of the Canadian goose, so their possible participation in the contamination of the superficial waters with cysts of Giardia sp. can be considere. With the purpose of testing this possibility, were captured some gallaretas in the complex Nordelta-Tigre (Bs. As., Argentina), taking samples of faecal pellets and duodenal content. The carried out studies did not showed Giardia sp. Anyway, it should be taken in to consideration the small size of the sample and it restricted geographical representation before possible epidemic inferences. The results provide original information on the rol of the wild aquatic birds as possible agents of dispersion of parasitosis whit importance in public health.

Riggia puyensis, an ectoparasitic isopod, was collected in juvenile Chaetostoma breve and Chaetostoma microps host specimens from the Amazonian region of Ecuador. The aim of this work is to study the possible injury that the parasite causes in its host. R. puyensis was found covered by a fold of the skin, which formed a sort of pocket or pouch within the host's peritoneal cavity. The alterations described in the epidermis were associated with the mechanical action of the isopod inside the pouch.

Fil: Plaul, Silvia Elena. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias; Argentina

The Rio Negro floodplain (tributary of the Amazon River) is a natural habitat of the cardinal tetra Paracheirodon axelrodi. In home aquaria, this species has high vulnerability to superficial infections and is affected by the protist Dermocystidium. Protist cysts were located in the dermis causing lesions reaching the epidermis. We observed that a few weeks after the introduction of new wild ornamental fish (mostly Hemigrammus sp. or Hyphessobrycon sp.) into established home aquaria, the cardinal tetra fish became infected, suggesting that the new fish could have acted as carriers.

Cheirodon interruptus is a ubiquitous small characid that inhabits the Pampean region and commonly used as bait. Its vast market is supplied from the wild population causing a significant environmental impact. In this study, we assess the effect of photoperiod on ovarian maturation in order to evaluate its potential as a tool to manipulate reproduction under artificial conditions. Four treatments in triplicate (light: dark, L: D) were tested: 24L: 0D, 12L: 12D, 0L: 24D and a progressive photoperiod corresponding to the daily photoperiod increments in wild during winter-spring transition, accelerated three times. The experiment was conducted for 45 days. Gonadosomatic index (GSI), oocyte mean diameter, vitellogenic oocyte proportions, plasma estradiol concentrations (E2), condition factor (Kn) and standard length were estimated. Values of mean GSI, oocyte diameter, vitellogenic oocyte proportions and E2 concentration were maximum in the progressive treatment indicating vitellogenesis stimulation. In turn the same parameters were minimum in the 24L: 0D, revealing the vitellogenesis inhibition. This study showed that photoperiodic regime play an important role in the onset of ovarian maturation in C. interruptus.

The Neotropical catfish Corydoras paleatus is a facultative air-breather and the caudal half of theintestine is involved in gas exchange. In South America, air-breathing fishes are found in tropical or sub-tropicalfreshwaters where the probability of hypoxia is high. The aim of this study was to characterize by traditionalhistochemical and lectinhistochemical methods the pattern of carbohydrate in the intestinal mucosa. Intestinesamples were taken from 25 healthy adult specimens collected in Buenos Aires (Argentina). Samples were fixedby immersion in 10 % buffered formalin and routinely processed and embedded in paraffin wax. Subsequently,these sections were incubated in the biotinylated lectins battery. Labeled Streptavidin-Biotin (LSAB) system wasused for detection, diaminobenzidine as chromogen and haematoxylin as a contrast. To locate and distinguishglycoconjugates (GCs) of the globet cells, we used the following histochemical methods: PAS; PAS*S; KOH/PA*S; PA/Bh/KOH/PAS; KOH/PA*/Bh/PAS; Alcian Blue and Toluidine Blue at different pHs. Microscopically,the general structure of vertebrate intestine was observed and showed all the cell types characteristic of theintestinal epithelium. The cranial sector of catfish intestine is a site of digestion and absorption and its structureis similar to other fish groups. In contrast, enterocytes of the caudal portion are low cuboidal cells; and betweenthese, globet cells and capillaries are observed, these latter may reach the mucosal lumen. Underlying the epithelium,observed a well-developed lamina propria-submucosa made of connective tissue; this layer was highlyvascularized and did not exhibit glands. According to histochemistry, the diverse GCs elaborated and secretedin the intestine are associated with specific functions in relation to their physiological significance, with specialreference to their role in lubrication, buffering effect and prevention of proteolytic damage to the epitheliumtogether with other biological processes, such as osmoregulation and ion exchange. The lectinhistochemicalanalysis of the intestinal mucosa reveals the presence of terminal residues of glucose, mannose and galactose.In conclusion, this study has shown that GCs synthesized in the intestine of C. paleatus exhibit a high level ofhistochemical complexity and that the lectin binding pattern of the intestinal mucosa is characteristic of eachspecies and the variations are related with the multiple functions performed by the mucus in the digestive tract.The information generated here may be a relevant biological tool for comparing and analyzing the possibleglycosidic changes in the intestinal mucus under different conditions, such as changes in diet or different pathologicalstages.

A new species of nematode parasite, Philometroides tahieli sp. nov. is described. The juvenile whitemouth croaker, Micropogonias furnieri Desmarest, was collected during the spring and summer of the years 2008-2010 from estuarial environments of Argentina. During investigations of the parasite fauna a nematode encapsulated in the musculature of the operculum was found. The nematodes were removed from the host's muscle tissue and slide-mounted in lactophenol solution to clarify the specimens. Opercular muscle with the parasite was processed for histopathological examination. Philometroides tahieli sp. nov. can be identified by the location of gravid females in the host, presence of anterior oesophageal bulb, bosses on the surface of the body, presence of transversal mounds and 14 cephalic papillae in two circular rows. The pathogenicity of the parasite is low in the natural environment, but lesions are consistent with a chronic process. The appearance of caseous necrosis suggests the presence of a locally acting substance. Philometroides tahieli sp. nov. is the second species of this genera described from brackish waters, and since the discovery of Philometroides maplestoni in 1928, is the first species of this genus recorded for South America.

ABSTRACT The Neotropical catfish, Corydoras paleatus (Callichthyidae) is a facultative air‐breathing teleost that makes use of the caudal portion of the intestine as an accessory air‐breathing organ. This portion is highly modified, being well vascularized with capillaries between epithelial cells, which makes it well suited for gas exchange. Instead, the cranial portion is a digestion and absorption site, as it has a typical intestinal epithelium with columnar cells arranged in a single row, villi and less vascularized tunica mucosa. Therefore, the intestine was studied by light and electron microscopy to assess differences between the cranial, middle and caudal portions. To characterize the potential for cell proliferation of this organ, we used anti‐proliferating cell nuclear antigen antibody and anti‐Na + K + ‐ATPase monoclonal antibody to detect the presence of Na + /K + pump. In C . paleatus it was observed that cell dynamics showed a decreasing gradient of proliferation in cranio‐caudal direction. Also, the intestine of this catfish is an important organ in ionoregulation: the basolateral Na + /K + pump may have an active role, transporting Na + out of the cell while helping to maintain the repose potential and to regulate cellular volume. Microsc. Res. Tech. 79:140–148, 2016 . © 2016 Wiley Periodicals, Inc.

The genus Parabrachiella Wilson, 1915 (Lernaeopodidae) is represented by copepods that are highly adapted to a parasitic way of life. In Argentina, only P. insidiosa var. lageniformis Heller, 1865, P. chevreuxii Van Beneden, 1891 and P. spinicephala Ringuelet, 1945 have been cited, but none of these have been reported on mugilids. Recently, other species of this genus were found attached to the nasal cavities of juvenile grey mullets, Mugil liza Valenciennes, from Samborombón bay, Buenos Aires province. In this study, the prevalence and mean intensity of the Parabrachiella sp. on grey mullet is investigated. In addition, the damage the parasite imposes on its hosts is examined through evaluation of histological sections and immunostaining for proliferative cell nuclear antigen (PCNA). The morphology of the parasite's bulla is described from light and scanning electron micrographs.