Geographical origin determines responses to salinity of Mediterranean caddisflies.

Many freshwater ecosystems worldwide, and particularly Mediterranean ones, show increasing levels of salinity. These changes in water conditions could affect abundance and distribution of inhabiting species as well as the provision of ecosystem services. In this study we conduct laboratory experiments using the macroinvertebrate Smicridea annulicornis as a model organism. Our factorial experiments were designed to evaluate the effects of geographical origin of organisms and salinity levels on survival and behavioral responses of caddisflies. The experimental organisms were captured from rivers belonging to three hydrological basins along a 450 Km latitudinal gradient in the Mediterranean region of Chile. Animals were exposed to three conductivity levels, from 180 to 1400 µS/cm, close to the historical averages of the source rivers. We measured the behavioral responses to experimental stimuli and the survival time. Our results showed that geographical origin shaped the behavioral and survival responses to salinity. In particular, survival and activity decreased more strongly with increasing salinity in organisms coming from more dilute waters. This suggests local adaptation to be determinant for salinity responses in this benthic invertebrate species. In the current scenario of fast temporal and spatial changes in water levels and salt concentration, the conservation of geographic intra-specific variation of aquatic species is crucial for lowering the risk of salinity-driven biodiversity loss.

Enterocolitis asociada a enfermedad de Hirschsprung / Enterocolitis associated with Hirschsprung's disease

La enterocolitis asociada a enfermedad de Hirschsprung (EAEH) se define como la presencia de diarrea, deposiciones explosivas, distensión abdominal y signos radiológicos de obstrucción intestinal o edema de la mucosa. Es la causa más común de mortalidad en pacientes con enfermedad de Hirschsprung (EH). Puede ocurrir en cualquier etapa de la enfermedad, con una incidencia media del 25 por ciento. La fisiopatología es poco conocida. Etiologías potenciales son la obstrucción mecánica, infecciones, barrera mucosa defectuosa, y un sistema inmunológico deficitario. Microscópicamente la EAEH se caracteriza por criptitis y abscesos en las criptas, seguida de ulceración de la mucosa progresiva conduciendo eventualmente a la necrosis transmural. Los pilares del tratamiento son la reanimación con fluidos, la descompresión del intestino y la terapia antibiótica. A veces se requiere de una estoma cuando estas medidas han fracasado. La mayoría de los pacientes con EAEH siguen teniendo trastornos de la función intestinal muchos años después de la cirugía para la enfermedad de Hirschsprung. Investigaciones en la fisiopatología de la EAEH pueden conducir a medidas preventivas y mejores modalidades de tratamiento.

Hirschsprung’s-associated enterocolitis(HAEC) is defined as the presence of diarrhea, explosive stools, abdominal distension and radiologic evidence of bowel obstruction or mucosal edema. HAEC is the most common cause of mortality in patients with Hirschsprung’s disease. This condition may occur in any stage of the Hirschsprung’s disease, with a mean incidence of 25 percent. The pathophysiology is poorly understood. Potential etiologies are mechanical obstruction, infections, defective mucosal barrier, and impaired immunological system. Microscopically HAEC is characterized by cryptitis and crypt abscesses followed by progressive mucosal ulceration eventually leading to transmural necrosis. The mainstays of treatment are fluid resuscitation, decompression of the bowel and antibiotic therapy. Sometimes a stoma is required when such measures have failed. The majority of patients with HAEC continue to have disturbances of bowel function many years after surgery for Hirschsprung’s disease. Researchs into the pathophysiology of HAEC can lead to better preventative measures and treatment modalities.