Morphometric differences in two calanoid sibling species, Boeckella gracilipes and B. titicacae (Crustacea, Copepoda)

Núcleo de Estudios Ambientales, Universidad Católica de TemucoCalanoid copepods are abundant in South American inland waters and include widespread species, such as Boeckella gracilipes (Daday, 1902), which occurs from the Ecuador to Tierra del Fuego Island. This species occurs under various environmental conditions, and is found in oligotrophic lakes in Patagonia (39-54°S) and in shallow mountain lakes north of 39°S. The aim of the present study is to conduct a morphometric comparison of male specimens of B. titicacae collected in Titicaca and B. gracilipes collected in Riñihue lakes, with a third population of B. gracilipes collected in shallow ponds in Salar de Surire. Titicaca and Riñihue lakes are stable environments, whereas Salar de Surire is an extreme environment. These ponds present an extreme environment due to high exposure to solar radiation and high salinity levels. The results of the study revealed differences among the three populations. These results agree well with systematic descriptions in the literature on differences between the populations of Titicaca and Riñihue lakes, and population of Salar de Surire differs slightly from the other two populations. It is probable that the differences between the population of Salar de Surire and the other two populations result from the extreme environment in Salar de Surire. High exposure to solar radiation, high salinity and extreme variations in temperature enhance genetic variations that are consequently expressed in morphology.Los copépodos calanoideos son abundantes en aguas continentales sudamericanas e incluyen especies de amplia distribución geográfica como Boeckella gracilipes (Daday, 1902) que se encuentra desde Ecuador hasta la isla de Tierra del Fuego. Esta especie vive bajo varias condiciones ambientales, y se encuentra en lagos oligotróficos en la Patagonia (39-54°S) y en lagunas superficiales de montaña al norte de los 39°S. El objetivo del presente trabajo es realizar un estudio comparativo morfométrico de machos de B. titicacae colectado en el lago Titicaca y B. gracilipes colectado en el lago Riñihue, ambos son ambientes estables, con una tercera población colectada en lagunas superficiales en el Salar de Surire. Estas lagunas tienen condiciones ambientales extremas debido a alta exposición a la radiación solar y altos niveles de salinidad. Los resultados del presente estudio encontraron diferencias entre las tres poblaciones. Estos resultados concordarían con las descripciones sistemáticas en la literatura sobre las diferencias de las poblaciones de los lagos Titicaca y Riñihue, y la población del salar de Surire tuvo leves diferencias respecto a las dos poblaciones anteriores. Es probable que las diferencias entre la población del Salar de Surire y las otras dos se deban a alta exposición a la radiación solar, salinidad y condiciones extremas de temperatura que acelera las diferencias genéticas las que se expresan en diferencias morfológicas

Ecosistemas acuáticos de islas oceánicas de Chile: Conservación de microfauna endémica y el rol de especies exóticas en el control biológico de enfermedades tropicales

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Richness and Distribution of Zooplanktonic Crustacean Species in Chilean Andes Mountains and Southern Patagonia Shallow Ponds

The lacustrine ecosystems located in the Andes Mountains in the Atacama desert and in the Chilean Southern Patagonia are characterized by their high levels of salinity, the zooplankton in these sites are characterized by a marked predominance of calanoid copepods at low or intermediate salinity levels, and at high salinity levels pratically only the genus Artemia is dominant. Data on levels of salinity and zooplanktonic composition in both regions were collected in field work and from published data. Statistical analysis showed a marked inverse association between salinity and species richness that was notoriously significant for Andes Mountains (R = -0.8193; p = 0.0037), whereas for Southern Patagonia there were observed weakly similar results, caused by lack of data between 5.0-15.0 g/l. Both zones observed calanoid dominance at low and moderate salinity levels between 3-51 g/l and 1-16 g/l for Andes Mountains and Southern Patagonia, respectively, and Artemia genus was dominant at salinities above 100 g/l for Andes Mountains and 20 g/l for Southern Patagonia. Ecological and biogeographic effects, and comparison with zooplankton assemblages of Australian saline lakes are discussed in the present study

Uso de distribuição binomial negativa para descrever a presença de Anisakis em Thyrsites atun.

Nematodes of the genus Anisakis have marine fishes as intermediate hosts. One of these hosts is Tyrsites atun, an important fishery resource in Chile between 38 and 41°S. This paper describes the frequency and number of Anisakis nematodes in the internal organs of Thyrsites atun. An analysis based on spatial distribution models showed that the parasites tend to be clustered. The variation in the number of parasites per host could be described by the negative binomial distribution. The maximum observed number of parasites was nine parasites per host. The environmental and zoonotic aspects of the study are also discussed.Nematóides do gênero Anisakis têm nos peixes marinhos seus hospedeiros intermediários. Um desses hospedeiros é Thyrsites atun, um importante recurso pesqueiro no Chile entre 38 e 41°S. Este artigo descreve a freqüência e o número de nematóides Anisakis nos órgãos internos de Tyrsites atun. Uma análise baseada em modelos de distribuição espacial demonstrou que os parasitos tendem a ficar agrupados. A variação numérica de parasitas por hospedeiro pôde ser descrita por distribuição binomial negativa. O número máximo observado de parasitas por hospedeiro foi nove. Os aspectos ambientais e zoonóticos desse estudo também serão discutidos

Abundance of Boeckella gracilis (Daday, 1902) (Copepoda, Calanoida) in seasonal coastal pools in the Araucania region (38°S, Chile)

The presence of the calanoid copepod Boeckella gracilis (Daday, 1902) in Chilean seasonal pools has been only poorly studied as yet. The aim of the present study thus is to investigate the role of conductivity and temperature on the relative and absolute abundance of B. gracilis in seasonal coastal pools in the Araucania region (38 degrees S, Chile). The results of correlation analysis revealed the presence of a significant inverse correlation between conductivity and relative abundance, whereas no significant correlations were found between conductivity and absolute abundance, between temperature and absolute abundance, and between temperature and relative abundance. These results agree partially with similar observations for mountain pools in the same region, but they would not agree with observations for calanoids of saline and subsaline inland waters in the northern and southern extremes of Chile. Considering this scenario, the species would show different populational responses to environmental stress in different situations, which phenomenon deserves to be studied more extensively and in more detai

A null model to study community structure of microcrustacean assemblages in northern Chilean shallow lakes

The inland water bodies of northern Chile (18-27°S) are characterized by high salinity levels and impoverished species richness. This study presents field observations of species associations sampled from shallow water bodies in the Antofagasta region of northern Chile (23°S). A species presenceabsence matrix was created for calculating the Jaccard Index of community similarity and for testing null models of species associations, with the aim of determining whether species associations, are random or not. The results of the Jaccard Index calculations indicated the existence of defined groups, including three sites with Artemia franciscana, two sites with Boeckella poopoensis, and a sixth site only containing the ostracod Sarscypridopsis aculeata. The results of the null model analysis denoted the presence of regulating factors only in fixed-fixed simulation, that is the most robust in comparison to the other two simulations that denoted absence of regulator factors in species associations. The Jaccard indices and significant null model analysis agree with previous ecological descriptions of salinity as a determinant of species associations, whereas the non-significant results of the other two simulations could be due to the low number of species reported. The ecology and biogeography of these communities are also discussed. © 2011 Koninklijke Brill NV, Leiden

Estrutura da comunidade de invertebrados em rios da região central do Chile

River systems of Central Chile are short, steep and fast flowing. They are characterized by discharge regimes dominated by rainfall and snowmelt. Invertebrate fauna is highly endemic. This study aimed to describe the community structure of invertebrate in eight river systems in Central Chile (33-39°S) using species co-occurrence and niche sharing null models. Methods: Invertebrate samples were collected from Central Chilean rivers (33-39°S), data were analyzed co-occurrence species and niche sharing null models for determine potential structuring patterns. Results: The results revealed the presence of non-structured patterns in co-occurrence considering each site as well as all sites, that is most probably an effect of presence of many repeated species in the studied sites. Furthermore, we found the existence of niche overlap due to interspecific competition at each site and among all sites. The results obtained from these river systems corroborate observations from Chilean Patagonian Rivers. Conclusion: This study contributes to understanding of biogeographical and ecological patterns of invertebrate communities in central Chilean Rivers and provide foundations for more complex ecological studiesOs sistemas fluviais do Chile central são curtos, íngremes e fluem rapidamente. Eles são caracterizados por regimes de descarga dominados por chuvas e neve derretida. A fauna de invertebrados desses sistemas fluviais é altamente endêmica. O objetivo do presente estudo foi descrever a estrutura da comunidade de invertebrados em oito sistemas fluviais na região central do Chile (33-39°S), utilizando co-ocorrência de espécies e modelos nulos de compartilhamento de nichos. Métodos: Amostras de invertebrados foram coletadas de rios chilenos centrais (33-39 ° S), os dados foram analisados com as espécies de coocorrência e os modelos nulos de compartilhamento de nichos para determinar potenciais padrões de estruturação. Resultados: Os resultados revelaram a presença de padrões não estruturados em coocorrência, considerando cada local, bem como todos os locais que é mais provavelmente um efeito da presença de muitas espécies repetidas nos locais estudados. A sobreposição de nicho revelou a existência de competição interespecífica em cada local e entre locais Os resultados obtidos para estes sistemas fluviais corroboram observações dos rios patagônicos chilenos. Conclusões: O presente estudo contribui para a compreensão dos padrões biogeográficos e ecológicos das comunidades de invertebrados nos rios da região central do Chile e, como tal, constitui a base para estudos ecológicos mais complexo