Resumo Estudos comparativos de parasitas em espécies de aves simpátricas são escassos. A infecção/transmissão de parasitas pode acontecer de diversas maneiras, incluindo possível transmissão direta, indireta ou horizontal entre as aves hospedeiras. Com o objetivo de determinar se dois icterídeos simpátricos do centro e sul do Chile compartilham a sua fauna parasitária (ecto- e endoparasitas), foram examinados os parasitas de 27 chupins Molothrus bonariensis e 28 pássaros-pretos-austral Curaeus curaeus, incluindo indivíduos capturados com rede de neblina e em carcaças. Nos chupins analisados, foram encontrados os piolhos de penas Brueelia bonariensis, Philopterus sp. 1, os ácaros Amerodectes molothrus, Proctophyllodes spp. (espécie 1 e 2), e os helmintos Mediorhynchus papillosus, Plagiorhynchus sp., Dispharynx nasuta e Tetrameres paucispina. Em contraste, os pássaros-pretos-austral estavam infectados com os piolhos Myrsidea sp., Philopterus sp. 2, os ácaros Proctophyllodes sp. 3, Amerodectes sp., e os helmintos Anonchotaenia sp., Capillaria sp. e M. papillosus. Adicionalmente, um espécime de pássaro-preto-austral estava parasitado pela pulga Dasypsyllus (Neornipsyllus) cteniopus. A única espécie de parasita que foi encontrada nas duas espécies de aves foi o acantocéfalo M. papillosus, possivelmente devido ao fato de que ambas as aves se alimentam dos insetos que são os hospedeiros intermediários deste parasita. Exceto os registros de B. bonariensis e Philopterus sp. 1 encontrados no chupim, todas as espécies reportadas neste estudo correspondem à novas associações de parasita/hospedeiro e novos registros para a diversidade parasitológica do Chile.

Abstract Comparative studies of parasites in sympatric bird species have been generally scarce. Parasitic infection/transmission can be spread in a number of ways that suggests possible direct and indirect, horizontal transmission between avian hosts. In order to determine whether two sympatric icterids from Central and Southern Chile share their parasite fauna (ecto- and endoparasites), we examined parasites of 27 Shiny Cowbirds, Molothrus bonariensis, and 28 Austral Blackbirds, Curaeus curaeus, including individuals captured in the wild and carcasses. We found that Shiny Cowbirds were infected with the chewing lice Brueelia bonariensis, Philopterus sp. 1, the feather mites Amerodectes molothrus, Proctophyllodes spp. (species 1 and 2), and the helminths Mediorhynchus papillosus, Plagiorhynchus sp., Dispharynx nasuta and Tetrameres paucispina, while Austral Blackbirds had the chewing lice Myrsidea sp., Philopterus sp. 2, the feather mites Proctophyllodes sp. 3, Amerodectes sp., and three helminths: Anonchotaenia sp., Capillaria sp. and M. papillosus. The flea Dasypsyllus (Neornipsyllus) cteniopus was found only on the Austral Blackbird. The only parasite species shared by both icterids was the acanthocephalan M. papillosus, possibly due to their feeding on the same intermediate insect hosts. With the exception of B. bonariensis and Philopterus sp. 1 found on the Shiny Cowbird, all species reported in this study represent new parasite-host associations and new records of parasite diversity in Chile.

Resumo Com o objetivo de identificar a fauna parasitária do saracura-do-banhado, Pardirallus sanguinolentus (Aves: Rallidae) no Chile, 26 carcaças foram necropsiadas. O presente estudo revelou a presença de 14 espécies de parasitos (índice Simpson inverso = 4,64; equitatividade = 0,332), incluindo os ácaros de penas: Analloptes megnini, Grallobia sp., Grallolichus sp., Megniniella sp. e Metanalges sp.; os piolhos de penas Pseudomenopon meinertzhageni, Rallicola andinus e Fulicoffula sp.; e seis espécies de helmintos gastrointestinais: Heterakis psophiae, Porrocaecum ardeae, Tetrameres sp., Capillaria sp., Diorchis sp. e Plagiorhynchus sp. A riqueza parasitária relativa encontrada pode ser devido às condições altamente favoráveis das zonas úmidas para o desenvolvimento do parasita. Todos os parasitos encontrados, com exceção dos piolhos de pena, são novos registros para o saracura-do-banhado. Um checklist dos parasitos do saracura-do-banhado é apresentado.

Abstract With the aim to identify the parasite fauna of plumbeous rail, Pardirallus sanguinolentus (Aves: Rallidae) in Chile, 26 carcasses were parasitologically necropsied. The present study revealed the presence of 14 species of parasites (inverse Simpson index = 4.64; evenness = 0.332), including ectoparasites: feather mites: Analloptes megnini , Grallobia sp., Grallolichus sp., Megniniella sp., and Metanalges sp.; the feather lice Pseudomenopon meinertzhageni, Rallicola andinus, and Fulicoffula sp.; and six species of gastrointestinal helminths: Heterakis psophiae, Porrocaecum ardeae, Tetrameres sp., Capillaria sp., Diorchis sp., and Plagiorhynchus sp. The relatively high parasite richness that was found could be attributed to the highly favorable conditions of wetlands for parasite development. All parasites found, except feather lice, are new records for plumbeous rail. A checklist of parasites for plumbeous rail is presented.

A detailed paleomagnetic and rock magnetic investigation has been carried out on the Early Cretaceous Ponta Grossa dike swarm in southern Brazil. This formation seems an excellent target for paleomagnetic study. The dikes are widely distributed over a large area, easy to access, and they record faithfully the geomagnetic field at the time of the eruption. Most of them are fresh and have been dated by K-Ar and Ar-Ar. Thermomagnetic experiments (low-field versus temperature curves) suggest low-Ti titanomagnetites as main remanence carriers, and their domain structure is characterised by a mixture of single-domain and multi-domain grains. Characteristic paleomagnetic directions are retrieved from 28 out of 29 sites (235 standard paleomagnetic cores). 17 sites show normal polarity, 10 sites show reverse polarity and one site shows an oblique direction, with negative inclination, separated 79° of the mean normal directions. The reversal test is positive at the 95% confidence level which ensures that the secondary remanent magnetizations were successfully removed and the sampling adequately averaged the palaeosecular variation. The paleosecular variation parameters values obtained in this study correlate with those determined for the Cretaceous Normal Superchron, between 125 to 84 Ma. The new paleomagnetic pole position (222.0° E, 88.1° S, N = 24, K = 35.68, A 95 = 5.0°) agrees well (within uncertainties) with the reference poles determined from Besse and Courtillot (2002), and disagree with those reported in previous studies. The new results should be considered for estimating the Cretaceous paleomagnetic poles for stable South America.

A detailed paleomagnetic and rock magnetic investigation has been carried out on the Early Cretaceous Ponta Grossa dike swarm in southern Brazil. This formation seems an excellent target for paleomagnetic study. The dikes are widely distributed over a large area, easy to access, and they record faithfully the geomagnetic field at the time of the eruption. Most of them are fresh and have been dated by K-Ar and Ar-Ar. Thermomagnetic experiments (low-field versus temperature curves) suggest low-Ti titanomagnetites as main remanence carriers, and their domain structure is characterised by a mixture of single-domain and multi-domain grains. Characteristic paleomagnetic directions are retrieved from 28 out of 29 sites (235 standard paleomagnetic cores). 17 sites show normal polarity, 10 sites show reverse polarity and one site shows an oblique direction, with negative inclination, separated 79° of the mean normal directions. The reversal test is positive at the 95% confidence level which ensures that the secondary remanent magnetizations were successfully removed and the sampling adequately averaged the palaeosecular variation. The paleosecular variation parameters values obtained in this study correlate with those determined for the Cretaceous Normal Superchron, between 125 to 84 Ma. The new paleomagnetic pole position (222.0° E, 88.1° S, N = 24, K = 35.68, A95 = 5.0°) agrees well (within uncertainties) with the reference poles determined from Besse and Courtillot (2002), and disagree with those reported in previous studies. The new results should be considered for estimating the Cretaceous paleomagnetic poles for stable South America.

The results of a paleomagnetic study performed over the Matasiete Formation, belonging to the Chubut Group, are presented. Alternating field and thermal demagnetization techniques were employed to analyze the stability of the magnetic remanence. The studied specimens have relatively high magnetic susceptibilities. They have soft viscous and low unblocking temperature components. These components are statistically coincident with each other and with the geocentric axial dipole field direction for the locality. The magnetic remanences were removed below 580ºC, indicating that magnetite is the main remanence carrier. Characteristic remanent magnetization directions were determined by principal component analysis with a maximum angular deviation smaller than 5º. Given the similar attitudes of the strata, the fold-tests are indeterminate. When the structural correction is applied, the concentration of characteristic remanent magnetization directions increases. That increase suggests that these remanences are pretectonic. All virtual geomagnetic poles corresponding to the remanent magnetizations have a normal polarity. The paleomagnetic pole calculated in this study for the Matasiete Formation is located at 84.7ºS, 161.2ºE (n=34, k=17.51, A95=6.1). That position is statistically equivalent to those of the PPs from Cerro Barcino Formation (112-125 Ma) and Los Adobes Formation (112-130 Ma), outcropping at Central Patagonia. The coincidence of these paleomagnetic poles supports the Hauterivian?-Barremian-Aptian age assigned to the Matasiete Formation on the base of different fosiliferous associations. As the normal polarity of all virtual geomagnetic poles suggests that these rocks were deposited during the Cretaceous normal superchron, an Aptian age is proposed for the Matasiete Formation.

Se presentan los resultados de un estudio paleomagnético de la Formación Matasiete, integrante del Grupo Chubut. Se analizó la estabilidad de las remanencias magnéticas empleando desmagnetización por altas temperaturas y por campos alternos. Estas rocas presentan susceptibilidades magnéticas relativamente altas. Los especímenes estudiados portan componentes viscosas blandas y de bajas temperaturas de desbloqueo cuyas direcciones son estadísticamente coincidentes entre sí y con la dirección que corresponde a un campo dipolar axial y geocéntrico para esa localidad. La remanencia prácticamente desaparece al alcanzar 580ºC indicando que la magnetita es el principal portador magnético. En todos los casos se aislaron componentes características con desviaciones angulares máximas <5º. Si bien las pruebas de estructura (fold/tilt tests) resultan indeterminadas dada las actitudes similares de los estratos, el aumento de la concentración de las direcciones de magnetizaciones remanentes características al aplicar la corrección por estructura sugiere que estas remanencias son pretectónicas. A partir de las magnetizaciones se calcularon los polos geomagnéticos virtuales, todos ellos de polaridad normal, y el polo paleomagnético (PP) para la Formación Matasiete (84.7ºS, 161.2ºE, número de muestras n=34, k=17.51, A95=6.1). La ubicación de este PP es equivalente a las de los PP de las Formaciones Cerro Barcino (112-125 Ma) y Los Adobes (112-130 Ma), aflorantes en Patagonia Central. Esta coincidencia en ubicación apoya la edad hauteriviana?-barremiana-aptiana, asignada en trabajos previos a la Formación Matasiete, sobre la base de asociaciones fosilíferas. Sin embargo la polaridad normal de todos los polos geomagnéticos virtuales sugiere que estas rocas se formaron durante el supercron cretácico normal por lo que se propone una edad aptiana para la Formación Matasiete.

A descriptive study was conducted in the Center of Genetic Development in La Lisa municipality from January 1999 to December 2003. The sample was composed of 251 pregnant women with advanced maternal age (38 or over) that seeked genetic counselling for having increased risk of chromosomopathies. The data were processed by the percentage calculation. 189 patients (75.29 %) were prenatally diagnosed (PND). 6 cases were positive, 4 Down's syndrome (47 XY+ 21), 1 super male (47 XYY), 1 trisomy 18 (47 XY + 18) and 15 cases without results. The prenatal diagnosis was not made in 62 patients, 12 due to threatened abortion, 25 due to advanced gestational age, 25 rejected the procedure and 3 for other causes. The genetic counseling was not directive. It respected the personal decisions and it was also reliable, presented the risk-benefit relation and required the informed consent.

Se realizó un estudio descriptivo en el Centro de Desarrollo de la Genética del municipio La Lisa, en el período comprendido de enero de 1999 hasta diciembre de 2003. La muestra la conformaron 251 embarazadas con edad materna avanzada (38 años o más) que acudieron a recibir asesoramiento genético por tener riesgo incrementado de cromosomopatías. Los datos fueron procesados con el cálculo porcentual. Se realizaron diagnóstico prenatal (DPN) 189 pacientes (75,29 %), y se obtuvieron 6 casos positivos, 4 síndrome Down (47 XY+21), 1 súper macho (47 XYY), 1 trisomía 18 (47 XY+18) y 15 casos sin resultados. No se realizaron el diagnóstico prenatal 62 pacientes, 12 por amenaza de aborto, 25 por edad gestacional avanzada, 25 por negarse a la realización del proceder y 3 por otras causas. El asesoramiento genético fue no directivo, respetando las decisiones personales, confiabilidad, exponiendo la relación riesgo / beneficio y obteniendo el consentimiento informado para su realización.

A descriptive study was undertaken at the Office of Genetics Development of La Lisa municipality from January 1999 to December 2003. The sample was composed of 338 pregnant women carriers of sickle cell anemia that received genetical counselling, which included the conduction of hemoglobin electrophoresis in the expectants and their husbands. The data were processed by percentage calculation. 28 risk couples were detected (7.2 %), of which 21 (75 %) chose the prenatal diagnosis of fetal hemoglobin. 4 fetoes with sickle cell anemia (19 %) and 9 carriers (42.8 %) were found. 7 patients did not have prenatal diganosis (25 %), 5 of them (71.4 %) due to advanced gestational age and 2 (28.5 %) for rejecting to do so. The genetical counselling was not directive. The personal decisions were respected and reliability was guaranteed. The risk/benefit relation was explained and in all cases the informed consent for the prenatal diagnosis was obtained.

Se realizó un estudio descriptivo en la Consulta de Desarrollo de la Ginecología del municipio La Lisa, en el período comprendido de enero de 1999 hasta diciembre de 2003. La muestra la conformaron 338 embarazadas portadoras de anemia a hematíes falciformes, a las que se les brindó asesoramiento genético que incluyó la repetición del estudio de electroforesis de hemoglobina y la realización al esposo. Los datos fueron procesados en el cálculo porcentual. Se detectaron 28parejas de riesgo (7,4 %), de las cuales 21 (75, 0 %) optaron por el diagnóstico prenatal de hemoglobina fetal. Se encontraron 4 fetos con anemia a hematíes falciformes (19 %) y 9 portadores (42,8 %). No se realizaron diagnóstico prenatal 7 pacientes (25 %), de ellas 5 (71,4 %) por edad gestacional avanzada y 2 (28, 5 %) por negarse a la realización del proceder médico. El asesoramiento genético fue no directivo, respetando las decisiones personales, confiabilidad, explicando la relación riesgo/beneficio, y obteniendo en todos los casos el consentimiento informado para el diagnóstico prenatal.