Feeding habits of the dwarf weakfish (Cynoscion nannus) off the coasts of Jalisco and Colima, Mexico

Sciaenids from the Pacific coast of Mexico are used as a second-class fish species for human consumption (Aguilar-Palomino et al., 1996). The dwarf weakfish (Cynoscion nannus) (Castro-Aguirre and Arvizu-Martínez, 1976) is often caught as bycatch in the shrimp fishery but, because of its small size (<27 cm TL, total length), it is not considered a valuable resource. This species can be found in great numbers in waters between 100 and 812 m (Allen and Robertson, 1994; Fischer et al., 1995) associated with the soft-bottom regions off the coast of Jalisco and Colima (González-Sansón et al., 1997)

Supraspecific units in correlative niche modeling improves the prediction of geographic potential of biological invasions

Background Biological invasions rank among the most significant threats to biodiversity and ecosystems. Correlative ecological niche modeling is among the most frequently used tools with which to estimate potential distributions of invasive species. However, when areas accessible to the species across its native distribution do not represent the full spectrum of environmental conditions that the species can tolerate, correlative studies often underestimate fundamental niches. Methods Here, we explore the utility of supraspecific modeling units to improve the predictive ability of models focused on biological invasions. Taking into account phylogenetic relationships in correlative ecological niche models, we studied the invasion patterns of three species (Aedes aegypti, Pterois volitans and Oreochromis mossambicus). Results Use of supraspecific modeling units improved the predictive ability of correlative niche models in anticipating potential distributions of three invasive species. We demonstrated that integrating data on closely related species allowed a more complete characterization of fundamental niches. This approach could be used to model species with invasive potential but that have not yet invaded new regions

First record of the invasive coral Oculina patagonica de Angelis, 1908 (Cnidaria, Scleractinia) in the Gulf of Mexico

Colonies of coral with morphology similar to that of Oculina patagonica de Angelis, 1908 were found in the National Park Veracruz Reef System (NPVRS) along the coast of Veracruz, Mexico in the southern Gulf of Mexico. The identity of these colonies as O. patagonica was confirmed by morphological and molecular analyses. Here, we document the first records of O. patagonica in the Gulf of Mexico. This species is native to the Mediterranean Sea, and could have been accidentally introduced to the Gulf of Mexico through ballast water from ships. In the NPVRS, poor environmental conditions such as polluted waters with high sedimentation, and the capability of O. patagonica to adapt could have facilitated the establishment of this species in the Gulf

Implications of global environmental change for the burden of snakebite.

Snakebite envenoming is a set of intoxication diseases that disproportionately affect people of poor socioeconomic backgrounds in tropical countries. As it is highly dependent on the environment its burden is expected to shift spatially with global anthropogenic environmental (climate, land use) and demographic change. The mechanisms underlying the changes to snakebite epidemiology are related to factors of snakes and humans. The distribution and abundance of snakes are expected to change with global warming via their thermal tolerance, while rainfall may affect the timing of key activities like feeding and reproduction. Human population growth is the primary cause of land-use change, which may impact snakes at smaller spatial scales than climate via habitat and biodiversity loss (e.g. prey availability). Human populations, on the other hand, could experience novel patterns and morbidity of snakebite envenoming, both as a result of snake responses to environmental change and due to the development of agricultural adaptations to climate change, socioeconomic and cultural changes, development and availability of better antivenoms, personal protective equipment, and mechanization of agriculture that mediate risk of encounters with snakes and their outcomes. The likely global effects of environmental and demographic change are thus context-dependent and could encompass both increasing and or snakebite burden (incidence, number of cases or morbidity), exposing new populations to snakes in temperate areas due to "tropicalization", or by land use change-induced snake biodiversity loss, respectively. Tackling global change requires drastic measures to ensure large-scale ecosystem functionality. However, as ecosystems represent the main source of venomous snakes their conservation should be accompanied by comprehensive public health campaigns. The challenges associated with the joint efforts of biodiversity conservation and public health professionals should be considered in the global sustainability agenda in a wider context that applies to neglected tropical and zoonotic and emerging diseases

DNA microarrays to identify etiological agents, as sensors of environmental wellbeing

Background: The epidemiologic transition in Mexico has generated a change of paradigm in public health. Morbidity is characterized by infectious diseases and the mortality is due to chronic degenerative diseases. The three most important infectious diseases in the country are: respiratory infections, diarrhea, and urinary tract infections.Method: The objective of this work was to build a tool to monitor the presence of health risks in the environment in a timely manner and to demonstrate its application in different sicknesses, especially those that are water related. In this study, we analyzed water samples from five cenotes with high tourist flow in the State of Yucatan. We developed a DNA microarray for the adequate and prompt detection of viruses, bacteria, fungi, and parasites. This microarray could be used in samples of different origin including air, water (fresh, brackish and saltwater), food, inert surfaces or wounds. Clinically, it would allow prompt and precise detection of etiological agents of infectious diseases to prevent outbreaks. It would also be useful for the identification of those agents that cannot be detected in our laboratories with the traditional methods. It includes 38,000 probes that detect 252 etiological agents of diseases in humans and antimicrobial resistance genes. Results from DNA samples can be obtained in 24 h, which would be difficult or impossible using other technologies.Results: The results are readily available within 24 h. Samples from five cenotes (sinkholes) with high flow of people, were analyzed with the microarray. The water samples analyzed detected 228 different bacteria, viruses, fungi, and protozoa. They are amongst the most important etiological agents for infectious diseases in Mexico.Conclusions: The microarray provides the opportunity for precise and early detection of various infectious agents in individuals, hospitals and natural environments. This could help reduce the global burden of diseases, the severity of outbreaks, and reduce antibiotic resistance

Ejercicio crítico a partir de la filosofía de Karl Popper.

A partir de un análisis crítico realizado en el Seminario de la Maestría de Ciencias Biológicas, se concluyen varios puntos: 1. Uno de los intereses fundamentales en los trabajos de Popper es definir el método o procedimiento para lograr el conocimiento. 2. Las teorías científicas no pueden ser comprobadas sino refutadas. 3. La investigación científica debe entenderse como un proceso que permite generar conocimiento por medio de la presentación de problemas y el planteamiento de diversas formas alternativas para solucionarlos

Feeding ecology of juvenile marine fish in a shallow coastal lagoon of southeastern Mexico

Many species of marine fish use coastal lagoons during early stages of their life cycles due to the protection provided by their turbid waters and complex structure of the environment, such as mangroves and mudflats, and the availability of food derived from the high productivity of these sites. In this study, we analyzed the diet of six species of juvenile marine fishes that use a karstic lagoon system in the northwest portion of the Yucatan Peninsula, Mexico. Through stomach contents analysis we determined the trophic differences among Caranx latus, Oligoplites saurus, Trachinotus falcatus, Synodus foetens, Lutjanus griseus, and Strongylura notata. C. latus, O. saurus, S. foetens, and S. notate, which are ichthyophagous species (>80% by number). L. griseus feeds mainly on crustaceans (>55%) and fish (35%), while T. falcatus feeds on mollusks (>50% bivalves, >35% gastropods). The analysis of similarities (ANOSIM) showed differences in the diet of all species. Cluster analysis, based on the Bray-Curtis similarity matrix revealed three groups; one characterized by the ichthyophagous guild (S. notata, S. foetens, C. latus, and O. saurus), other group formed by the crustacean consumers (L. griseus), and the third, composed by the mollusk feeder (T. falcatus). Species of the ichthyophagous guild showed overlap in their diets, which under conditions of low prey abundance may trigger competition, hence affecting juvenile stages of these marine species that use coastal lagoons to feed and grow

Mass density assessment : comparison of three methods using Oikopleura dioica (Appendicularia) as a model system

Individual and environmental mass densities have an important effect on the dynamics of suspended particulate material in the water column. We used Oikopleura dioica as a model system to compare the accuracy of mass density estimates (rho(s)) using three methods. The first one was based on a morphometric analysis which allowed the construction of a three-dimensional geometric model of the organism to estimate individual body volumes (IBV), while weight was directly measured to calculate density. The second method was derived from Stokes Law, using the settling velocity of Oikopleura houses. Finally, the actual mass density of organisms was measured using a single-density gradient column calibrated with known-density glass floats. Mean h, estimates ranged from 1.0314 g.cm(-3) to 1.0846 g(.)cm(-3), and did not differ significantly among the three methods. Nevertheless, the greatest accuracy was attained with the single-density gradient column. The methodological approach presented in this paper is useful to assess the mass density of small plankton organisms and contribute to the generation of data on the rate at which energy transfer occurs in aquatic ecosystems

Reproductive variability of the common snook, Centropomus undecimalis, in environments of contrasting salinities interconnected by the Grijalva–Usumacinta fluvial system

The common snook, Centropomus undecimalis, is a migratory euryhaline fish. In the southern Gulf of Mexico, fishing of large snooks occurs mainly in the marine environment (MA), while medium-size adults and juveniles are caught in freshwater environments (FW); however, large-size adults can also be found in FW far away from the sea, and the effect of different environments on their reproductive cycle is unknown. To describe the reproductive cycle of this species in different salinity habitats, we analyzed macroscopic reproductive characteristics during one annual cycle in FW and MA interconnected by the Grijalva–Usumacinta basin. Specimens with full-grown gonads and capable of spawning were found in FW, an unusual condition not reported for this habitat, but active spawning was observed only in MA. Centropomus undecimalis has a biological strategy that allows the use of FW as a juvenile until it reaches sexual maturity as a male and joins the reproductive stock in MA. Adults of both sexes can remain in both FW and MA without affecting their reproductive cycle, suggesting that those that mature in FW migrate to the sea during the spawning season.

Feeding habits of the fishes Lutjanus peru and Lutjanus guttatus (Pisces: Lutjanidae) of Guerrero, México.

Se analiza la composición de la dieta del huachinango (Lutjanus peru) y del flamenco (Lutjanus guttatus) en la costa de Guerrero, México. Los ejemplares se obtuvieron mensualmente de las capturas comerciales en tres regiones de pesca y presentaron intervalos de talla comprendidos entre 130 y 684 mm de longitud horquilla (LH) para el caso de L. peru, y de 120 a 550 mm para L. guttatus. A partir del número y del peso de los distintos componentes alimentarios, identificados hasta el taxon más bajo posible, se calcularon los porcentajes numéricos (%N), gravimétricos (%P) y de frecuencia de ocurrencia (%FO) que fueron sintetizados como valores de importancia relativa. En los estómagos de L. peru se identificaron 68 ítems alimentarios dentro de los cuales predominan los peces (%P = 50.9), los crustáceos (%P = 35.6) y los moluscos (%P = 7.2) mientras que el espectro alimentario de L. guttatus estuvo integrado por 88 componentes que incluyeron principalmente peces (%P = 50.8) y crustáceos (%P = 43.4). Ambas especies son depredadoras generalistas, con un amplio espectro de presas. Los valores de los índices de traslape de las dietas de estas especies sugieren que no existe un alto grado de competencia intraespecífica por el alimento. Con el fin de encontrar similitudes en la dieta de estos lutjánidos en varias localidades de México y Costa Rica, se realizó un análisis de conglomerados con los valores de importancia relativa de las presas, publicados en varios trabajos. Se encontró más afinidad en la dieta de aquellas especies que habitan en una misma localidad, que entre organismos de la misma especie distribuidos en diferentes zonas. Se infiere que la disponibilidad de las presas, más que la selectividad por el alimento, determina la dieta de estas especies.Diet composition of the Pacific snapper (Lutjanus peru) 130-684 mm fork length (FL) and the spotted snapper (Lutjanus guttatus) 120-550 mm FL, was analyzed. Monthly samples were obtained from commercial landings in three regions off the coast of Guerrero, Mexico. Percentage by number (%N), percentage by weight (%W), and percentage of occurrence (%O) were calculated for each prey and summarized as the index of relative importance. Both species are polyphagous predators feeding on a variety of prey: Sixty-eight prey items, mainly fish (%W = 50.9), crustaceans (%W = 35.6), and mollusks (%W = 7.2), were found in the stomach contents of L. peru, while 88 components were identified in the diet of L. guttatus, the most important prey being fish (%W = 50.8) and crustaceans (%W = 43.4). Diet overlap between species is not significant (p&lt;0.05), indicating that competition for food is unlikely. Based on published values of the relative importance index, the diets of these Lutjanidae were analyzed considering different regions of the Pacific coast of Mexico and Costa Rica, and similarities among sites and species were discussed. The cluster analysis showed that similarities among species inhabiting in the same area are more important than within organisms of the same species living in different zones. Results suggest that prey availability rather than food selectivity, conditions the feeding behavior of these fish species