RESUMEN

Ectothermic species are particularly sensitive to changes in temperature and may adapt to changes in thermal environments through evolutionary shifts in thermal physiology or thermoregulatory behaviour. Nevertheless, the heritability of thermal traits, which sets a limit on evolutionary potential, remains largely unexplored. In this study, we captured brown anole lizards (Anolis sagrei) from two populations that occur in contrasting thermal environments. We raised offspring from these populations in a laboratory common garden and compared the shape of their thermal performance curves to test for genetic divergence in thermal physiology. Thermal performance curves differed between populations in a common garden in ways partially consistent with divergent patterns of natural selection experienced by the source populations, implying that they had evolved in response to selection. Next, we estimated the heritability of thermal performance curves and of several traits related to thermoregulatory behaviour. We did not detect significant heritability in most components of the thermal performance curve or in several aspects of thermoregulatory behaviour, suggesting that contemporary selection is unlikely to result in rapid evolution. Our results indicate that the response to selection may be slow in the brown anole and that evolutionary change is unlikely to keep pace with current rates of environmental change.

Asunto(s)

RESUMEN

Tropical ectotherms are thought to be especially vulnerable to climate change because they are adapted to relatively stable temperature regimes, such that even small increases in environmental temperature may lead to large decreases in physiological performance. One way in which tropical organisms may mitigate the detrimental effects of warming is through evolutionary change in thermal physiology. The speed and magnitude of this response depend, in part, on the strength of climate-driven selection. However, many ectotherms use behavioral adjustments to maintain preferred body temperatures in the face of environmental variation. These behaviors may shelter individuals from natural selection, preventing evolutionary adaptation to changing conditions. Here, we mimic the effects of climate change by experimentally transplanting a population of Anolis sagrei lizards to a novel thermal environment. Transplanted lizards experienced warmer and more thermally variable conditions, which resulted in strong directional selection on thermal performance traits. These same traits were not under selection in a reference population studied in a less thermally stressful environment. Our results indicate that climate change can exert strong natural selection on tropical ectotherms, despite their ability to thermoregulate behaviorally. To the extent that thermal performance traits are heritable, populations may be capable of rapid adaptation to anthropogenic warming.

Asunto(s)

RESUMEN

OBJECTIVE: To investigate whether increased knowledge and use of public health measures promoted for cholera prevention is reflected in lower prevalence of parasitic infection in households in a community in the state of Tamaulipas, Mexico, that is close to the border with the United States of America. METHODS: Between 1994 and 1997, fecal samples from 438 children were collected through convenience sampling and then examined for helminth eggs/larvae and protozoan cysts as biologic indicators of household compliance with recommended cholera prevention measures. The suggested measures were to wash hands before meals and after defecation, to drink purified water, to wash fruits and vegetables, and to eat well-cooked food. In addition, information on the knowledge of and the use of cholera preventive measures was collected by interviews with adult informants in 252 households (186 of those households also provided a fecal sample for analysis). RESULTS: Parasitic infections occurred in 131 of the 438 children (30%), who resided in 79 of the 186 households (42%) that provided fecal samples. Giardia lamblia accounted for 12.5% of all infections. Infections with Hymenolepis nana, Ascaris lumbricoides, Trichuris trichiura, Enterobius vermicularis, Ancylostoma/Necator, Strongyloides stercoralis, Entamoeba coli, Entamoeba hartmanni, Entamoeba histolytica, Endolimax nana, and Iodamoeba bütschlii were also noted. Infected children were older and more often had an infected sibling. Households with three or more children were also more likely to have an infected child. The primary caregivers in the households where at least one child had a parasitic infection were distinguished by their inability to list at least three cholera prevention measures from memory. CONCLUSIONS: The 42% household prevalence of parasitic infection was relatively high and indicates that some residents of this community may not have fully embraced the public health education efforts promoted for prevention of cholera. The occurrence of nonpathogenic protozoan parasites such as Endolimax nana, Entamoeba coli, Entamoeba hartmanni, and I. bütschlii are important bioindicators for the persistence of unhygienic behaviors that increase the risk of cholera and other infectious diseases dependent on fecal-oral transmission. Information obtained by similar studies can be useful for monitoring compliance with community health and hygiene programs and may indicate the need to intensify educational efforts for the prevention of diarrhea associated with enteric pathogens that cannot be controlled by drugs alone.

Asunto(s)

RESUMEN

OBJECTIVE: To investigate whether increased knowledge and use of public health measures promoted for cholera prevention is reflected in lower prevalence of parasitic infection in households in a community in the state of Tamaulipas, Mexico, that is close to the border with the United States of America. METHODS: Between 1994 and 1997, fecal samples from 438 children were collected through convenience sampling and then examined for helminth eggs/larvae and protozoan cysts as biologic indicators of household compliance with recommended cholera prevention measures. The suggested measures were to wash hands before meals and after defecation, to drink purified water, to wash fruits and vegetables, and to eat well-cooked food. In addition, information on the knowledge of and the use of cholera preventive measures was collected by interviews with adult informants in 252 households (186 of those households also provided a fecal sample for analysis). RESULTS: Parasitic infections occurred in 131 of the 438 children (30 percent), who resided in 79 of the 186 households (42 percent) that provided fecal samples. Giardia lamblia accounted for 12.5 percent of all infections. Infections with Hymenolepis nana, Ascaris lumbricoides, Trichuris trichiura, Enterobius vermicularis, Ancylostoma/Necator, Strongyloides stercoralis, Entamoeba coli, Entamoeba hartmanni, Entamoeba histolytica, Endolimax nana, and Iodamoeba bütschlii were also noted. Infected children were older and more often had an infected sibling. Households with three or more children were also more likely to have an infected child. The primary caregivers in the households where at least one child had a parasitic infection were distinguished by their inability to list at least three cholera prevention measures from memory. CONCLUSIONS: The 42 percent household prevalence of parasitic infection was relatively high and indicates that some residents of this community may not have fully embraced the public health education efforts promoted for prevention of cholera. The occurrence of nonpathogenic protozoan parasites such as Endolimax nana, Entamoeba coli, Entamoeba hartmanni, and I. bütschlii are important bioindicators for the persistence of unhygienic behaviors that increase the risk of cholera and other infectious diseases dependent on fecal-oral transmission...

Objetivos. Evaluar si un mejor conocimiento y una mayor aplicación de las medidas de salud pública fomentadas para la prevención del cólera se reflejan en una menor prevalencia de infestación parasitaria en el medio doméstico de una comunidad del estado de Tamaulipas, México, cercano a la frontera con los Estados Unidos de América. Métodos. Entre 1994 y 1997 se recolectaron muestras fecales de 438 niños mediante un muestreo por conveniencia. Estas muestras fueron examinadas en busca de huevos o larvas de helmintos y quistes de protozoos, como indicadores biológicos del cumplimiento en el medio doméstico de las medidas recomendadas para la prevención del cólera. Las comidas y después de defecar, tomar agua purificada, lavar las frutas y vegetales e ingerir alimentos bien cocinados. Adicionalmente, se obtuvo información relativa al conocimiento y aplicación de las medidas para la prevención del cólera mediante entrevistas a adultos de 252 viviendas (186 de esas viviendas también entregaron muestras para análisis). Resultados. De los 438 niños, 131 (30%) presentaron infestaciones parasitarias. Estos niños residían en 79 (42%) de las 186 viviendas que entregaron muestras fecales. Giardia lamblia representó el 12,5% de las infestaciones. También se encontraron Hymenolepis nana, Ascaris lumbricoides, Trichuris trichiura, Enterobius vermicularis, Ancylostoma/Necator, Strongyloides stercoralis, Entamoeba coli, Entamoeba hartmanni, Entamoeba histolytica, Endolimax nana e Iodamoeba bütschlii. Los niños con parasitosis eran mayores y con mayor frecuencia tenían algún hermano o hermana infestado. Las viviendas con tres o más niños presentaron mayor probabilidad de tener algún niño infestado. Las personas encargadas de cuidar la salud en las viviendas donde había al menos un niño con parasitosis se caracterizaron por no poder mencionar de memoria al menos tres medidas de prevención contra el cólera. Conclusiones. La prevalencia de viviendas con niños infestados con parásitos (42%) fue relativamente elevada e indica que algunos residentes de esta comunidad pueden no haber respondido totalmente a los esfuerzos de educación sanitaria promovidos para la prevención del cólera. La presencia de protozoos parasitarios no patógenos, como Endolimax nana, Entamoeba coli, Entamoeba hartmanni o I. bütschlii, es un marcador biológico importante de la persistencia de hábitos higiénicos inadecuados que aumentan el riesgo de cólera y otras enfermedades infecciosas de transmisión fecaloral. La información obtenida de estudios similares puede servir para vigilar el cumplimiento de los programas de salud e higiene comunitarias, e indica que es necesario intensificar el trabajo educativo dirigido a la prevención de la diarrea asociada con patógenos entéricos que no pueden ser controlados solo con medicamentos

Asunto(s)

Asunto(s)