Biological Responses of the American Coot (Fulica americana), in wetlands with contrasting environmental conditions (Basin of México).

Wetland ecosystems are subject to severe impacts (physical and chemical) and to the input of various xenobiotics that provoke toxicological consequences. Waterbirds are potential sentinel species of these environments. To analyze how habitat conditions affect the health of Fulica americana, early-warning biomarkers, histopathology, somatic indices, and water quality were examined in two wetlands of the Basin of Mexico: Xochimilco, an urban wetland highly eutrophic with a mixture of pollutants, and Tecocomulco (the reference site), a rural wetland with hunting migratory birds in winter, and with some agricultural contaminants. Coots were collected over 1 year, and the birds were aged, eviscerated, and weighed. Liver samples were analyzed biochemically and histologically. Biomarkers revealed that coots displayed higher lipid peroxidation and elevated activities of gamma-glutamyl transferase and alanine aminotransferase, suggesting hepatic damage during autumn and winter. In Tecocomulco, coots during winter has the highest thiobarbituric acid reactive substances (as a measure of oxidative stress), which may be associated with the presence of predators. In Tecocomulco, the higher gonadosomatic index was detected in spring and summer, while in Xochimilco it was elevated in summer, indicating a delayed egg laying and reproduction in coots from the latter study site. In both wetlands, leukocyte infiltration, alone or combined with vasocongestion, reflected alterations in the inflammatory processes in liver throughout the annual cycle and thus potentially altered hepatic function and organism survival. In both wetlands, coots were permanent residents and chronically exposed to different stressors, suggesting damage may be irreversible with potentially adversely reproductive consequences.

Liver histological changes and lipid peroxidation in the amphibian Ambystoma mexicanum induced by sediment elutriates from the Lake Xochimilco.

Lacustrine sediments accumulate pollutants that input from the lake watershed and can be released to the water column by sediment resuspension; thus, pollutants can change their bioavailability and exert adverse effects to aquatic biota. Shallow-urban lakes are particularly susceptible to receive pollutants from urban discharges and sediment resuspension. Lake Xochimilco, in Mexico City, an urban-shallow lake, faces multiple problems: urban sprawl, overexploitation of aquifers, drying of springs, discharge of wastewater from treatment plants, and sediment resuspension. The aquatic biota living in this ecosystem is continuously exposed to the release of pollutants from the sediments. We assessed the risk that pollutants released from sediments from Lake Xochimilco, Touristic (TZ) and Agriculture zone (AZ), can exert on a native amphibian species of the lake (Ambystoma mexicanum) through exposure bioassays to sediment elutriates. We evaluate alterations in the amphibian by three approaches: biochemical (level of lipid peroxidation, LPO), cellular (ultrastructure) and the liver histology of A. mexicanum and we compare them with a batch control. Additionally, we assessed heavy metals (Pb, Cd and Hg) in elutriates. Elutriates from TZ showed the highest concentrations of the metals assessed. Organisms exposed to sediment elutriates from either study sites showed higher LPO values than control organisms (p<0.05). Organisms exposed to elutriates from the TZ showed the most conspicuous damages: hepatic vasodilation of sinusoids, capillaries with erythrocytes, leukocyte infiltration and cytoplasmic vacuolation in hepatocytes. The biological responses assessed reflected the risk that faces A. mexicanum when is exposed for prolonged periods to sediment resuspension in Lake Xochimilco.

Histopatología del hígado, lipoperoxidación e índices somáticos de Fulica americana en los humedales de Xochimilco (urbano) y Tecocomulco (rural) de la Cuenca de México / Liver histopatology, lipidperoxidation and somatic indices of Fulica americana in Xochimilco (urban) and Tecocomulco (rural) wetlands in the Mexico basin

Los humedales son cuerpos de agua muy productivos y son refugio para aves migratorias; sin embargo, continuamente reciben contaminantes que ejercen daños en los organismos acuáticos. El objetivo del trabajo fue evaluar el estado de salud de Fulica americana mediante biomarcadores histopatológicos, de estrés oxidativo, e índices somáticos en dos humedales de la Cuenca de México, para evaluar el efecto de las condiciones del hábitat en la salud de las aves. Se obtuvieron ejemplares en los humedales, Xochimilco (X) y Tecocomulco (T) en diferentes períodos de un año. Se determinó su edad, se evisceraron y pesaron, se obtuvieron porciones del hígado para el análisis histológico y para la cuantificación del nivel de lipoperoxidación (LPO). Se analizó la calidad del agua de X y T. Se realizó la técnica histológica de inclusión en parafina y la tinción Hematoxilina-Eosina. El mayor deterioro de la calidad del agua se observó en X. Se encontró infiltración leucocitaria (IN) y vasocongestión (VA) en tres grados. En T se observó la mayor prevalencia de ejemplares con daños combinados, en particular en las hembras; mientras que en X se presentó un mayor porcentaje de organismos con IN. La LPO más alta se observó durante el invierno en T lo que pudiera estar relacionado con el arribo de aves migratorias y la cacería; mientras que en X la mayor LPO estuvo relacionada con la reproducción. La mayor masa corporal eviscerada se presentó en los machos de T y la menor en las hembras de X. En todas las gallaretas los índices hepatosomáticos máximos se alcanzaron en otoño y los mínimos en primavera. F. americana puede ser utilizada como centinela debido a que presentó respuestas diferenciadas en los índices somáticos y en los biomarcadores histopatológicos y de estrés oxidativo en las distintas localidades, sexo y épocas del año.

Wetlands are very productive ecosystems and water birds complete their lifecycle there. Unfortunately, they constantly receive xenobiotics which can cause damage in aquatic organisms. This work assessed the health conditions of Fulica americana through histopathological and oxidative stress biomarkers and somatic indices in two wetlands from the Mexico Basin to evaluate the effect of habitat conditions on the birds health. The specimens were collected from Xochimilco (X) and Tecocomulco (T) wetlands during an annual cycle. They were eviscerated and weighed. Liver samples were taken for histological analysis and to quantify the lipid peroxidation (LPO) in the laboratory. The coots were aged. The water quality from both wetlands was analyzed. The liver tissue was embedded in liquid paraffin and was stained with hematoxylin and eosin. Two pathologies were detected in three levels each (I, II and III): leukocyte infiltration (IN) and vasocongestion (VA). The highest prevalence of both damages were observed in T coots, while the highest IN percentage was detected in X coots. The maximum LPO levels were detected during winter at T, which could be related to hunter season and the wintering migratory birds. In X the highest LPO levels were related to breeding season. The biggest eviscerated body mass was noted in T males and the smallest in the X females. All coots reached the highest hepatosomatic index during autumn and the minimum during spring. American coot can be used as sentinel because it is able to present differentiated responses, somatic indices, histopathological biomarkers and oxidative stress in different locations, sex and periods of the year.

Histological description of oogenesis in chiton virgulatus (Mollusca: Polyplacophora) / Descripción histológica de la ovogénesis de chiton virgulatus (Mollusca: Polyplacophora)

This paper describes the oogenesis of Chiton virgulatus, based on histological observations under transmission and scanning electron microscopy. Three oocyte types were identified: i) previtellogenic oocytes with a mean diameter of 50±20.5 µm, surrounded by elongated follicular cells of approximately 5 µm, ii) immature vitellogenic oocytes with a mean diameter of 113±15.3 µm and small cytoplasmic projections denoting the onset of the oocyte hull development; adjacent to each projection are pores approximately 0.7 µm in diameter, and iii) mature vitellogenic oocytes with a mean diameter of 146±24.8 µm; the oocyte cytoplasmic projections grow and its apical zone becomes trident-shaped; follicular cells adopt a bulbous shape due to the growth of the elongation and can reach up to 20 µm in length. The morphology and ultrastructure of the projections of the mature vitellogenic oocyte, as well as the size of pores at their base, are specific to C. virgulatus; therefore, these features could be used in taxonomic or fertilization studies.

En el presente trabajo se describe la ovogénesis de Chiton virgulatus, utilizando histología y las técnicas de microscopía electrónica de barrido y de transmisión. Se identificaron tres tipos de ovocitos: i) ovocitos previtelogénicos con un diámetro promedio de 50±20,5 µm, rodeados por células foliculares de forma alargada y un tamaño de aproximadamente 5 µm, ii) ovocitos vitelogénicos inmaduros con un diámetro promedio de 113±15,3 µm, este tipo de ovocitos presentan pequeñas proyecciones citoplasmáticas, que indican el inicio del desarrollo del casco del ovocito. Adyacentes a cada prolongación se presentan poros con un diámetro aproximado de 0,7 µm y iii) ovocitos vitelogénicos maduros con un diámetro promedio de 146±24,8 µm, las proyecciones citoplasmáticas del casco del ovocito crecen y en su parte apical adquieren la forma de un tridente, las células foliculares, dado el crecimiento de la prolongación toman el aspecto bulboso y llegan a medir hasta 20 µm de longitud. La morfología y la ultraestructura de las proyecciones del casco del ovocito vitelogénico maduro, así como el tamaño del poro en la base de las proyecciones son particulares para C. virgulatus, dichas características podrían ser utilizadas en trabajos de taxonomía y fertilización.

Estudio histológico del tubo digestivo y aparato venenoso de Gemmula periscelida (Gastropoda: Turridae) / Histologic study of digestive tract and venom apparatus of Gemmula periscelida (Gastropoda: Turridae)

En el presente trabajo se describe anatómica e histológicamente el tubo digestivo y aparato venenoso de Gemmula periscelida (Gastropoda: Turridae) en ejemplares colectados al Noroeste de la Plataforma Continental Yucateca. Se determinó que el tipo de epitelio que reviste a cada una de las zonas del tubo digestivo (probóscide, esófago anterior, medio y posterior, estómago, glándula digestiva e intestino) y al aparato venenoso, es diferente a lo reportado para otros túrridos; por lo que se infiere el posible mecanismo de alimentación para esta especie.

In this paper we realized anatomical and histologically description of the digestive tract and venom apparatus of Gemmula periscelida (Gastropoda: Turridae) specimens collected northwest of the Yucatan Shelf. Results of analysis show that there are differences in the type of epithelium coating each of the areas of the digestive tract (proboscis, anterior, middle and posterior esophagus, stomach, digestive gland and intestine) and of a venom apparatus with respect to that reported for other turrid snails. This suggests the possible feeding mechanism for this species.

Biología Reproductiva de Mytilopsis leucophaeata (Conrad, 1831) (Bivalvia: Dreissenidae) de la Laguna de Tampamachoco, Túxpam-Veracruz / Reproductive Biology of Mytilopsis leucophaeata (Conrad, 1831) (Bivalvia: Dreissenidae) of Tampamachoco Lagoon, Tuxpan-Veracruz

Se caracterizó el ciclo reproductivo de Mytilopsis leucophaeata (Conrad, 1831) en organismos colectados mensualmente durante un ciclo anual en la laguna de Tampamachoco, Túxpam, Veracruz, que se ubica en la costa del Golfo de México en la Región Terrestre Prioritaria (RTP-103) de CONABIO considerada sitio RAMSAR 1602 en México. Los resultados histológicos indican que M. leucophaeata presenta cuatro etapas gametogénicas: gametogénesis, madurez, desove total para hembras y expulsión parcial para machos. Uno de los principales factores que influyen en el desove sincrónico de gametos tanto en machos como en hembras es la salinidad, en los meses de enero a marzo.

The reproductive cycle of Mytilopsis leucophaeata (Conrad, 1831) was characterized in organisms collected monthly during an annual cycle in Tampamachoco lagoon Tuxpam-Veracruz, located on the coast of the Gulf of Mexico in the Terrestre Prioritaria Region (RTP-103) of CONABIO considered a RAMSAR 1602 site in Mexico. Histological results indicated that M. leucophaeata has four gametogenic stages: gamete, maturity, female's total spawning and partial expulsion inmales. One of the main factors that influence the synchronous spawning gametes in both males and females is salinity, in the months of January to March.

Biochemical and Mitochondrial Changes Induced by Cd, Fe and Zn in Limnodrillus hoffmeisteri / Cambios Bioquímicos y Mitocondriales Inducidos por Cd, Fe y Zn en Limnodrillus hoffmeisteri

The effects of sublethal concentrations of cadmium (0.64 µg/L), iron (0.043 mg/L) and zinc (0.31 mg/L) and a mixture of these metals on succinate dehydrogenase (SD) and alkaline phosphatase (AP) activity and on structural changes in the mitochondria of epithelium cells of the digestive tract were examined in the oligochaete Limnodrillus hoffmeisteri after 96 h of exposure in artificial sediments. SD activity was significantly inhibited, particularly in treatments with Cd alone (92.57 percent), while AP increased its activity with Cd alone (73.23 percent). However, when this metal was mixed with Fe and Zn, the inhibition of SD activity was lower (67.82 percent) than with Cd alone, showing an antagonistic effect and AP increased its activity (73.26 percent). Mitochondria were structurally damaged by exposure to Cd alone. However, in the metal mixtures, the toxic effects may exert interactive effects eliciting a less structural damage in the mitochondria of epithelium cells of the digestive tract than when Cd is alone.

Se estudió el efecto de las concentraciones subletales de Cd (0,64 µg/L), Fe (0,043 mg/L) y Zn (0,31 mg/L) en forma aislada y en mezcla sobre la actividad de la succinato deshidrogenasa (SD) y la fosfatasa alcalina (AP) en las mitocondrias de las células epiteliales del tracto digestivo en el oligoqueto Limnodrillus hoffmeisteri después de 96 h de exposición en sedimentos artificiales. La SD se inhibió significativamente, particularmente en los tratamientos con Cd en forma aislada (92,57 por ciento), mientras que la AP se incrementó con Cd en forma aislada (73,23 por ciento). Sin embargo, cuando este metal se mezcló con Fe y Zn, la inhibición de la SD fue menor (67,82 por ciento) que con Cd en forma aislada, lo que mostró un efecto antagonístico y la AP incrementó su actividad (73,23 por ciento). Sin embargo, cuando este metal estaba en mezcla con Fe y Zn, la inhibición de la SD fue menor (67,82 por ciento) que con Cd en forma aislada, mostrando un efecto antagonístico y un incremento en la actividad de la AP (73,26 por ciento). Las mitocondrias fueron dañadas estructuralmente por exposición al Cd en forma aislada. Sin embargo, con los metales en mezcla, los efectos tóxicos pudieron ejercer efectos interactivos provocando un menor daño estructural en la mitocondria de las células del epitelio del tracto digestivo que cuando el Cd estaba en forma aislada.

Effect of Yerbimat herbicide on lipid peroxidation, catalase activity, and histological damage in gills and liver of the freshwater fish Goodea atripinnis.

The use of herbicides for agricultural and aquatic weed control has increased worldwide. These substances are potentially toxic pollutants because they induce the production of reactive oxygen species for biological systems and exert oxidative stress in nontarget organisms living in the treated aquatic systems. Recent evidence suggests differences in the toxicity of glyphosate in the form of an active ingredient compared to the toxicity of glyphosate in combination with surfactants, such as those found in commercial formulations. In Mexico, one of the most widely used glyphosate-based herbicides is Yerbimat, which has agricultural as well as aquatic weed control applications. However, there are no aquatic toxicity data, particularly regarding native fish. Therefore, we determined the acute toxicity of commercial-formulation Yerbimat in a static bioassay at 96 h (LC(50)). We also determined its toxicity at 96 h in sublethal concentrations to assess the lipid peroxidation levels (LPX), catalase activity, hepatic glycogen content, and histological damage in the liver and gills of the fish Goodea atripinnis associated with chronic exposure (75 days). The LC(50) was 38.95 ± 0.33 mg/L. The results of the short-term exposure study indicate that Yerbimat can potentially induce oxidative stress in G. atripinnis, because LPX was increased in the gills and liver. Catalase activity was reduced in the gills but increased in the liver, whereas hepatic glycogen was depleted. Chronic exposure was associated with histopathological damage in the gills and liver, some of which was irreversible. Yerbimat represents a potential risk for aquatic biota; therefore, we recommend that its application be carefully considered.

Histological description of the male and female gonads in Tegula eiseni, T. funebralis, T. aureotincta, T. gallina and T. regina from Bahia Tortugas, B.C.S., Mexico / Descripción histológica de las gónadas masculinas y femeninas en Tegula eiseni, T. funebralis, T. aureotincta, T. gallina y T. regina de Bahía Tortugas, B. C. S., México

Some of the gastropods of the Baja California peninsula are of commercial value, but the majority are not. Among the less commercially valuable species are members of the genus Tegula, which are ecologically important because of their abundance and the trophic level they occupy. Mature specimens of T. eiseni, T. funebralis, T. aureotincta, T. gallina, and T. regina were collected from two rocky reefs close to Bahía Tortugas, B.C.S. and were processed using a paraffin-embedding technique. All of these species are dioecious, without external sexual dimorphism; in adults, the female gonads are green moss colored while male gonads are cream colored. The gonadal tissue is limited externally by a single ciliated cylindrical epithelium with plentiful granular glandular cells and is located on a connective tissue and muscular fiber layer. This layer is invaginated towards the gonad core, creating radially distributed trabeculae where the germinal tissue is found. The size of the oogonia fluctuates between 10 and 30 um, and that of the developing oocytes ranges between 30 and 140 um. In this stage, the cells are pyriform with a peduncle linked to the trabeculae. Mature oocytes have an average size of 165 um and present a well-defined chorion and a large quantity of vitelline platelets that occupy the whole cytoplasm. In the five species, the development in males is similar until the spermatid stage. In general, the average size of the spermatic cell nucleus is 2.5 um, while the flagellum length varies from 35 to 45 um. The species differ in the shape of the acrosome.

La costa oriental de la Península de Baja California se caracteriza por ser una zona de alta productividad biológica en la que coexiste un elevado número de gastrópodos, algunos de alto valor comercial y otros, la gran mayoría, no. Tal es el caso de diversas especies del Género Tegula, las cuales, ya sea por su abundancia y/o por el nivel trófico que ocupan dentro de la comunidad, resultan relevantes. Ejemplares adultos de Tegula eiseni, T. funebralis, T. aureotincta, T. gallina y T. regina, fueron colectados en dos arrecifes rocosos próximos a Bahía Tortugas, B.C.S. y procesados mediante la técnica de inclusión en parafina. Las especies estudiadas son dioicas sin dimorfismo sexual externo; la gónada de las hembras adultas es color verde musgo, mientras que la de los machos es color crema. La gónada se encuentra limitada externamente por un epitelio cilíndrico simple ciliado con abundantes células glandulares granulares, que se asienta sobre una capa de tejido conjuntivo y fibras musculares. Esta capa se invagina formando trabéculas de disposición radial donde se desarrolla el tejido germinal. Las ovogonias presentan un tamaño que fluctúa entre 10 y 30 um, en tanto que el de los ovocitos en desarrollo varía entre 30 y 140 um; en este estadio, las células son piriformes con un pedúnculo, por medio del cual se unen a las trabéculas. Los ovocitos maduros tienen un tamaño promedio de 165 um, presentan un corion bien definido y una gran cantidad de plaquetas vitelinas que ocupan la totalidad del citoplasma. En los machos el desarrollo es similar en las cinco especies, hasta la etapa de espermátide. En general, el tamaño promedio del núcleo de la célula espermática es de 2,5 um, mientras que el flagelo tiene una longitud que fluctúa entre 35 y 45 um. La forma del acrosoma es diferente para cada especie.

Estudio Histológico de Boca, Esófago, Estómago e Intestino de Polystira albida (Gastropoda: Turridae) / Histology Study of Mouth, Esophagus, Stomach and Intestine of Polystira albida (Gastropoda: Turridae)

En la presente investigación se realizó la caracterización histológica del tubo digestivo de Polystira albida (Toxoglossa:Turridae) mediante microscopía óptica, utilizando ejemplares colectados en la Sonda de Campeche. Los resultados del análisis muestran que los labios, la boca y la probóscide presentan un epitelio cilindrico simple ciliado. La cavidad bucal tiene un epitelio cilindrico estratificado. El esófago presenta un epitelio cilindrico simple con células glandulares granulares acidófilas (naturaleza proteica), y es el sitio donde comienza la digestión. El estómago se divide en tres regiones histológicas, y tiene dos tipos de epitelio, uno cilindrico simple ciliado y otro cilindrico simple; el primero está formado por abundantes células glandulares acidófilas y basófilas (naturaleza proteica y glicoproteica', respectivamente); y el segundo contiene slo células glandulares acidófilas. La glándula digestiva está constituida por adenómeros túbulo-acinosos con células glandulares acidófilas y basófilas, en diferentes grados de secreción y los conductos presentan un epitelio cilindrico ciliado con células glandulares de ambos tipos. El intestino se divide en cinco regiones histológicas, la primera presenta un tiflosol con dos tipos de epitelio, cilindrico simple y cilindrico simple con chapa estriada; y el resto del tracto tiene un epitelio cilindrico simple ciliado con células glandulares granulares acidófilas y pliegues de diferentes tamaños que aumentan o reducen la cavidad del conducto. Se concluye que existen diferencias, principalmente en la región anterior del tubo digestivo (cavidad bucal, esófago y estómago), con respecto a las descripciones generales realizadas para la subclase Prosobranchia.

In the present investigation it was realized a histological characterization of the digestive tract of Polystira albida (Toxoglossa: Turridae), by using optic microscopy of specimens collected in Sonda de Campeche. Results of analysis show that lips, mouth and proboscis present a simple columnar epithelium with cilia. Buccal cavity has a stratified columnar epithelium. Esophagus presents a simple columnar epithelium with acidophilic granular glandular cells (proteic nature), and it is the place where digestion starts. Stomach is divided in three histological regions that have two epithelial types, simple columnar with cilia and without one; the first is formed by a lot of acidophilic and basophilic glandular cells (proteic and glycoproteic nature respectively), and the second only contains acidophilic glandular cells. Digestive gland is constituted by tubule-acinous adenomers with acidophilic and basophilic glandular cells in different grades of secretion, and ducts have simple columnar epithelium with cilia and scarcely glandular cells. Intestine is divided in five histological regions, the first presents atyphlosole with two types of epithelium, simple columnar with stratified border; the rest of the tract has simple columnar epithelium with cilia, acidophilic granular glandular cells and folds of different sizes that increase or reduce the cavity duct. Based on previous this, we conclude that in this study exist differences principally in front region of digestive tract (buccal cavity, esophagus and stomach) compared to general descriptions realized for Prosobranchia subclass.

The role of vitellogenin during gestation of Girardinichthys viviparus and Ameca splendens; two goodeid fish with matrotrophic viviparity.

Goodeid fish have matrotrophic viviparity, and unlike lecitotrophic fish, yolk loss forces the female to provide the nutritional requirements for embryonic development. Vitellogenin (VTG) is the yolk precursor protein synthesized in the maternal liver, but there is only circumstantial evidence regarding VTG supply during the ontogenesis of bony fish with matrotrophic viviparity. Therefore, the goal of the present study was to identify and quantify VTG during gestation of the black fin goodeid Girardinichthys viviparus and the butterfly split-fin goodeid Ameca splendens. Females at different gonadic developmental stages were selected in order to evaluate VTG mRNA expression in the maternal liver using RT-PCR; VTG quantification in maternal muscle and liver, as well as in the embryos, was done using ELISA, and immunohistochemical detection of VTG was done in the black fin goodeid. The results suggest that VTG supplies nutrients during embryonic development of both species, which have different life histories. It is possible that the transition from lecitotrophy to matrotrophic viviparity in bony fish with intraluminal gestation involved adaptive transition strategies that included changes in the relationship between oocytes and follicular cells, as well as a gradual loss of VTG synthesis during embryonic development.