CEAZA
Heritability and genetic correlations of escape behaviours in juvenile scallop Argopecten purpuratus.
Brokordt, K., Farías, W., Lhorente, J., & Winkler, F.
Escape behaviours are generally considered adaptive because of their obvious effects on fitness. However, little is known about the genetic basis of escape responses. The estimation of the magnitude of hereditary factors affecting variation in escape responses indicates their potential to evolve by natural selection. Scallops are exceptional among bivalve molluscs because they possess an excellent swimming capacity, which helps them to escape predators. In this study we estimated the narrow-sense heritability (h2), phenotypic variance components and phenotypic and genetic correlations of several escape response traits (i.e. reaction time, number of claps (rapid valve closures and openings), and the duration and intensity of the clapping response) in juvenile Argopecten purpuratus scallops. We stimulated scallop escape responses using their natural predator, the sea star Meyenaster gelatinosus. Genetic estimates for escape response traits were determined by the animal model. Most studied traits showed substantial amounts of additive genetic variance controlling their phenotypic variation (CVA = 18.43–100.2), were repeatable (at least over a short period, R = 0.36–0.42), and had significant heritabilities (h2 = 0.36–0.57). Indeed, it can be inferred that most of the analysed escape response traits of A. purpuratus could evolve through natural selection. Moreover, significant genetic correlations between some escape response traits were observed, suggesting that selection acting on one escape trait will affect that of another, facilitating their coevolution.
Año: 2012
Palabras claves: Argopecten purpuratus; escape behaviour; genetic correlation; heritability; scallop
Referencia APA: Brokordt, K., Farías, W., Lhorente, J., & Winkler, F. (2012). Heritability and genetic correlations of escape behaviours in juvenile scallop Argopecten purpuratus. Animal Behaviour, 84(2), 479-484.
Effects of the toxic dinoflagellate Alexandrium catenella on histopathogical and escape responses of the Northern scallop Argopecten purpuratus.
Hégaret, H., Brokordt, K., Gaymer, C., Lohrmann, K., García, C., & Varela, D.
Juvenile Northern scallops Argopecten purpuratus were exposed to cultures of the paralytic shellfish toxin (PST) producing dinoflagellate, Alexandrium catenella, or a non-toxic microalga as a control, T-iso. After 3 and 6 days of exposure to either A. catenella or T-iso, scallops were stimulated to elicit an escape response by exposing them to the predatory sea star Meyenaster gelatinosus. We monitored the escape response of the scallops in terms of reaction time after first contact with the sea star, number of claps (burst of rapid valve closures) until exhaustion, clapping time, clapping rate, the time scallops spent closed when exhausted, and recovery from the initial number of claps, clapping time and clapping rate. Additionally, histopathological and stress responses (through heat-shock protein [hsp70] induction), as well as accumulation of Paralytic Shellfish Poisoning (PSP) toxins, were monitored on scallops after 3 and 6 days of exposure to A. catenella. After 6 days of exposure, scallops exposed to A. catenella accumulated PSTs and reacted more rapidly with a higher clapping rate, however the duration of their escape response was shorter than controls, when exposed to M. gelatinosus. Additionally, scallops exposed to A. catenella showed histopathological features, especially after 6 days of exposure, including increased melanization of the tissues and myopathy, with high levels of degeneration of the muscle fibers. A six-day exposure to A. catenella also caused an increase in prevalence of rickettsiales-like organisms within scallop tissues. This study suggests that PST accumulation can affect the interaction between the Northern scallop and both pathogens and predators, potentially increasing their susceptibility to either of them.
Año: 2012
Palabras claves: Scallop; Alexandrium; HAB; Escape response; Histopathology; PSP
Referencia APA: Hégaret, H., Brokordt, K., Gaymer, C., Lohrmann, K., García, C., & Varela, D. (2012). Effects of the toxic dinoflagellate Alexandrium catenella on histopathogical and escape responses of the Northern scallop Argopecten purpuratus. Harmful Algae, 18, 74-83.
Assessing the Influence of the MJO on Strong Precipitation Events in Subtropical, Semi-Arid North-Central Chile (30°S).
Juliá, C., Rahn, D., & Rutllant, J.
Annual precipitation in subtropical, semiarid north-central Chile (30°S) during rainy years comprises a few (3–5) strong events in the fall and winter, which are presumably modulated by the Madden–Julian oscillation (MJO). Precipitation from 1979–2009 was recorded daily at three stations along the Elqui Valley. The relationship between the MJO and precipitation is investigated from two perspectives: 1) examining a MJO index (MJOI) based on the actual precipitation events and 2) examining the likelihood of precipitation based on a favorable MJOI. About 80% of the strong precipitation events at the coast in La Serena are related to an active MJO near the central equatorial Pacific. These events are often typified by broad, slow moving synoptic systems in phase with the MJO propagation. Blocking in the far southeast Pacific is associated with precipitation 75% of the time, while deep troughs make up the rest.
A relationship between a MJOI and strong rainfall suggests that, though it could be used as a potential diagnostic, the number of cases where there is a favorable MJOI but no precipitation (i.e., false alarms) limits its utility. Additional criteria such as the Southern Oscillation (SO) and Antarctic Oscillation (AAO) phases were used to reject false alarms. Rejecting cases with positive values of the SO index reduced the number of false alarms from 70% to 58%, leaving about two false alarms for every correctly diagnosed event. The AAO index could not discriminate between false alarms and real cases. While a favorable MJOI increases the likelihood of precipitation in the Elqui Valley, false alarms remain problematic.
Año: 2012
Palabras claves: South America; Madden-Julian oscillation; Precipitation; Surface observations; Seasonal forecasting; Intraseasonal variability.
Referencia APA: Juliá, C., Rahn, D., & Rutllant, J. (2012). Assessing the Influence of the MJO on Strong Precipitation Events in Subtropical, Semi-Arid North-Central Chile (30°S). Journal Of Climate, 25(20), 7003-7013.
The conquest of the South Pole: Importance and lessons for the present.
Molina-Montenegro, M. & Corcuera, L.
On December 14, 1911, the Swedish Roald Amundsen, heading a group of explorers reached the South Pole. This date has become a symbol of all those great explorers that risking their lives in the most inhospitable continent in our planet, reached places that looked impossible to conquer. This date is also a symbol of the great difficulties that must be overcome to work in the Antarctic and of much that is yet to be known in the white continent. These are the reasons why Revista Chilena de Historia Natural is commemorating this important historic event with a Special Feature dedicated to Antarctic research.
The era of epic exploration in the Antarctic, such as those led by Roald Amundsen, Robert Scott, Ernest Shakleton, and many others has come to an end. This era had great unforgettable victories and defeats. The exciting race to conquer the South Pole among Amundsen and Scott left valuable lessons on the enormous difficulties to perform Antarctic exploration and the importance of planning and logistic design for any activity in the Antarctic. Perhaps, one of the best known expeditions for the magnitude of the encountered, adverse climatic conditions and importance of international cooperation is the Endurance Expedition, led by Ernest Shackleton in the period between 1914 and 1916. The loss of the Endurance, the courage of the explorers to reach Elephant Island, and the incredible determination of the leader of the expedition to achieve impress us even today. It was this determination that inspired the Chilean pilot Luis Pardo to risk the precarious ship Yelcho, performing one of the most celebrated rescue expeditions in Antarctic history. This era of great explorers, in addition to opening new routes, had the merit of drawing international attention on the great white continent and raised interest of many countries on the possible colonization, use of resources, and scientific research of Antarctic organisms, geological resources, climate, atmosphere, climatic change, and other aspects.
The difficulties and dangers of Antarctic research are still enormous in spite of the technology which is available today. Logistic costs to perform modern and safe Antarctic expeditions are very high. For this reason, the available budget is the main limitation for Antarctic research. However, in spite of the encountered difficulties, researchers have unveiled step by step the importance of Antarctic in the world's climate, ocean levels, availability of natural resources, and aspects of conservation and utilization of its flora and fauna.
Año: 2012
Palabras claves:
Referencia APA: Molina-Montenegro, M. & Corcuera, L. (2012). The conquest of the South Pole: Importance and lessons for the present. Rev. Chil. Hist. Nat., 85(4), 365-367.
What do we know about high-altitude precipitation in the semi-arid Andes of Chile?
Bourgin P, Andreassian V, Gascoin S, Valery A.
Mapping precipitations on a regular grid is often required for hydrological and ecological modelling. The spatial interpolation methods are generally used to estimate such a distribution from ground-based measurements. In the case of mountainous areas, the estimation of precipitation amounts is still a challenging task and the results of spatial interpolation should be verified as much as possible. Here we describe a three-steps method for the validation of a precipitation map. This is used in the context of a mountainous semi-arid region, the Norte Chico in Chile (26°S-32°S). The implementation of this validation method showed the benefits of an interpolation method developed by Valéry [2010] for mountainous areas. The hydrological balance of the high-altitude watersheds is now more realistic.
Año: 2012
Palabras claves: Precipitation, spatial interpolation method, extrapolation, altitude, altitudinal corrections, validation, water equivalent, water balance.
Referencia APA: Bourgin P, Andreassian V, Gascoin S, Valery A. (2012). Que sait-on des précipitations en altitude dans les Andes semi-arides du Chili?. La Houille Blanche. 2012;(2):12-17.