Browsing by Author "CASTILLA, JC"

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    BODY-SIZE, POPULATION-DENSITY, AND THE ENERGETIC EQUIVALENCE RULE
    (1995) MARQUET, PA; NAVARRETE, SA; CASTILLA, JC
    1. We critically evaluated the Energetic Equivalence Rule (EER) with regard to its underlying theoretical framework, its dependence of a particular relationship between population density and body size, and the way it is calculated.
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    EMERSION BEHAVIOR AND FORAGING ECOLOGY OF THE COMMON CHILEAN CLINGFISH SICYASES-SANGUINEUS (PISCES, GOBIESOCIDAE)
    (1988) CANCINO, JM; CASTILLA, JC
    The present study is the first to correlate information on emersion behaviour and foraging ecology of Sicyases sanguineus, a common clingfish of the Chilean coast. Individuals smaller than 15 cm in total length were frequently found at the highest points in the inter-tidal zone and consumed inter-tidal animals and seaweeds. Fish larger than 23 cm were infrequently observed emersed in the lower inter-tidal zone, but were collected sub-tidally by divers. These large clingfish ate mainly benthic animals occurring in the low inter-tidal and sub-tidal zones. Size-dependent factors, dessication and wave impact restrict the area of action of S. sanguineus to certain areas of the rock inter-tidal and shallow sub-tidal zone. However, the fish can be locally very abundant, consuming a great diversity of prey items including both direct primary space users and mobile animals able to affect community structure through grazing. We argue, therefore, that S. sanguineus may be important in structuring communities in some areas of the rocky inter-tidal and shallow sub-tidal zones of Central Chile.
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    GALLERIES OF THE CRABS ACANTHOCYCLUS UNDER INTERTIDAL MUSSEL BEDS - THEIR EFFECTS ON THE USE OF PRIMARY SUBSTRATUM
    (1989) CASTILLA, JC; LUXORO, C; NAVARRETE, SA
    The mid rocky intertidal of Cachagua, like many other rocky sites in central Chile, is dominated by beds of the mussel Perumytilus purpuratus. Under these mussel beds the predatory crabs Acanthocyclus gayi and A. hassleri build separated bind-ending galleries whose floor is the rock and the roof is the mussel bed. Samples of 1 m2 of Perumytilus beds (100% cover) showed that the surface area of crab galleries ranged between 17.4% and 34.7% of the total area, and that 80% of the crabs were A. hassleri. In 130 of the 157 galleries analyzed, one or two conspecific crabs were found. In the remainder, up to six crabs were found together. Comparisons between the floor of crab galleries and similar rocky areas under the mussel bed, but without galleries (controls), showed that both density and cover of Balanus flosculus, Phymactis clematis and bryozoans were significantly higher in galleries. Similarly, the total number of species was greater on the floor of the galleries than in the controls. Although from outward appearances the cover of P. purpuratus remained at 100%, crab galleries allowed more sessile species to occupy the mid intertidal fringe. This occurs because of the introduction of species typical of the lower intertidal, which would otherwise be excluded by mussels.
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    IMPACT OF HUMAN EXPLOITATION ON POPULATIONS OF THE INTERTIDAL SOUTHERN BULL-KELP DURVILLAEA-ANTARCTICA (PHAEOPHYTA, DURVILLEALES) IN CENTRAL CHILE
    (1990) BUSTAMANTE, RH; CASTILLA, JC
    The effect of small-scale harvesting on populations of Durvillaea antarctica (Chamisso) was studied at four localities in central Chile. Density, standing crop and mean individual size were compared between populations protected from harvesting and those subjected to repeated cropping. Populations on islands, where access by collectors is restricted, were also assessed. Populations of D. antarctica at harvested mainland sites did not differ in abundance (density and standing crop) or mean size. At non-harvested sites standing crops were twice as high as at harvested sites. However, plant density at harvested sites was double that at non-harvested sites. Mean algae size at harvested sites was significantly smaller than at non-harvested sites, because collectors select the largest individuals, usually those with a holdfast diameter of greater than 4 cm. A significant positive correlation was found between wet biomasses present on the islands and those at adjacent harvested and non-harvested mainland sites. Availability of potential space for settlement was also correlated with the density of algae, both on the mainland and on islands. Islands appear to act as seeding grounds or refugial areas, supplying recruits to the adjacent mainland sites. Differences in abundance of D. antarctica between the different localities could therefore be explained by the level of exploitation and by the local geomorphology, particularly the presence or absence of nearshore islands.
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    MARINE ENVIRONMENTAL-IMPACT DUE TO MINING ACTIVITIES OF EL-SALVADOR COPPER MINE, CHILE
    (1978) CASTILLA, JC; NEALLER, E
    Marine environmental impact as a result of Cu mine tailing dumping in the sea is studied at Chanaral (North Chile). These dumpings, from the Cu mine El Salvador, hindered harbor activities, caused geomorphological coastal modifications and seriously affected marine coastal ecosystems and recreational activities. At the old dumping site, Chanaral Bay (1938-1974), nearly 150 million tons of fine sediments were accumulated. Tailing discharges at the new dumping site, Caleta Palito, about 8 km north of Chanaral Bay are accumulating approximately at the rate of 25,000 tons of fine sediments/day, plus unknown quantities of chemicals (Cu, As, CN-). From Jan., 1975-July, 1976, this site received over 13 million tons of sediments, which caused deterioration of the marine coastal environment, reduction in light penetration and high mortalities among marine invertebrates, fishes and algae.
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    NEUROTRANSMITTER-RELATED ENZYME ACETYLCHOLINESTERASE IN JUVENILES OF CONCHOLEPAS-CONCHOLEPAS (MOLLUSCA, GASTROPODA, MURICIDAE)
    (1990) GONZALEZ, M; PERELMAN, A; FUENTES, ME; CASTILLA, JC; LABARCA, R; BRANDAN, E; GONZALEZPLAZA, R; INESTROSA, NC
    With the aim of understanding the organization of the nervous systemn in the Prosobranchia gastropod Concholepas concholepas, we studied the properties, specificity, sedimentation coefficient, and solubility of the cholinergic enzyme, acetylcholinesterase (AChE). It was found that 95% of the esterase was inhibited by BW284c51 dibromide but not by iso-OMPA, which is consistent with the specificity of AChE. The calculated Km 0.22 mM is eight to ten times higher than are the Kms for AChE of other invertebrates and similar to the values reported for fish and vertebrates. The AChE shows a maximal activity around 22.degree. C, has a glycoprotein character and presents sedimentation coefficients of 6.5 S and 10.5 S. Most of this AChE activity is soluble under low ionic strength conditions; however, the enzyme aggregates in the absence of detergents. In conclusion, our evidence indicates the presence of a well-recognized molecular marker that could be useful for the study of the development of Concholepas concholepas.
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    SCALING POPULATION-DENSITY TO BODY SIZE IN ROCKY INTERTIDAL COMMUNITIES
    (1990) MARQUET, PA; NAVARRETE, SA; CASTILLA, JC
    Interspecific comparisons of animal population density to body size has been the subject of active research in the last decade, especially for terrestrial animals when considering particular taxa or taxonomic assemblages. Studies of rocky intertidal communities showed that animal population density scales with body size to the -0.77 power. This relation held within local communities representing a broad array of animal taxa and was not affected by a dramatic alteration in the network of between-species interactions, as revealed by two long-term human exclusion experiments.
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