Oscar Zúñiga

Recording of ocean-climate changes during the last 2,000 years in a hypoxic marine environment off northern Chile (23°S)

Atmosphere-ocean interactions are particularly strong along the Chile-Peru coast and largely account for the extreme aridity of the Atacama Desert. Near the center of the driest part of this coastal desert, we found that the embayment Bahia Mejillones constitutes an unusually favorable setting for the formation and subsequent preservation of a sedimentary record of the successive oceanographic conditions of the last few thousand years. This work deals with relative abundance of various bio-indicators, including fish scales, foraminifers and phytoplankton, with a centimetre-scale resolution, in several gravity cores taken from 80 to 120 m depth, in a low-oxygen environment. We use this information to document oceanclimate changes at decadal to centennial time scales in the region. Radiocarbon dating on the bulk organic-rich sediment provides the chronological framework for the observed paleoceanographic changes. We interpret that an episode of relatively warmer water, with a stratified water column and enhanced anoxic ( 0.3 ml l -1

Distribution and characterization of Chilean populations of the brine shrimp Artemia (Crustacea, Branchiopoda, Anostraca)

Hypersaline habitats in Chile, from marine solar salt pans to saline lagoons and pools in Andean salars, were prospected in search of Artemia populations. These saline ecosystems were characterized through physico-chemical parameters and ionic composition of their brines. Biometrics of cysts and nauplii, as well as morphometrics by using multivariate discriminant analysis for adult specimens evidenced that the Chilean populations of brine shrimp belong to A. franciscana. Cross-breeding results supported the former hypothesis of conspecific Chilean populations, and their differences with A. persimilis, also endemic to the New World, but restricted to Argentinean sites.

Comparación biométrica del lóbulo frontal en poblaciones americanas de Artemia (Anostraca, Artemiidae)

Se compararon el diametro del lobulo frontal y su relacion con la longitud corporal, en poblaciones de Artemia franciscana (Chile y Estados Unidos), A. persimilis (Argentina) y Artemia sp. (Chile), cultivadas en laboratorio bajo condiciones controladas. Se encontraron diferencias significativas en ambos parametros entre las poblaciones de A. franciscana y Artemia sp., de Salina El Convento (Chile) y entre A. persimilis y Artemia sp. de Torres del Paine (Chile). Se discuten en el presente trabajo los factores geograficos, ecologicos y geneticos que determinaron la especiacion de Artemia en Chile y Argentina, y como esta se manifiesta en distintos patrones morfometricos

Foraminíferos bentónicos recientes en sedimentos micróxicos de la bahía Mejillones del Sur (23º S), Chile

The composition of recent benthic foraminifera was analyzed in eight sedimentological interfase samples collected with a box core of 0,16 m 2 surface in Mejillones del Sur bay (23o S) at depths of 56 to 138 m. The study area is characterized by a large relative abundance of Bolivina seminuda Cushman and the presence of Nonionella stella Cushman & Moyer and Bolivina costata Orbigny. The registered diversity (H) is low and varies between 0,8 and 2,4. The deepest station near Punta Angamos, presents the highest index and is the only one with Cancris auriculus (Fichtel & Moll) and Valvulineria inflata (Orbigny). The faunistic density of stations located in the center and external zones of this bay showed the highest values (average= 2600 ind/g), with most of the material representated by Bolivina seminuda. The results showed that the benthic foraminiferal distribution is directly related with bottom-water oxygen content. B. seminuda is adapted notably to microxic conditions (0,01 ml l - 1 ). Buliminella elegantissima (Orbigny) is found in more oxygenated areas (0,5 ml l -1 ), while B. costata and N. stella

Fairy Shrimp (Branchiopoda: Anostraca) of Chile

Abstract Portions of Chile were surveyed for Anostraca. Including the two species of Artemia previously reported from Chile, we found 5 new localities and range extensions for 5 species of Branchinecta. Previous studies on Chilean Anostraca have focused on Artemia, and although Branchinecta was previously reported in Antarctica close to Chilean Air Force installations, and in a few temporal ponds in Southern Patagonia, the species were never determined. Brief habitat descriptions, as well as conservation status, and identification keys are presented and discussed. Additionally, we describe a new species from the Atacama Desert, Branchinecta papillata n. sp.

Evaluación del crecimiento del pulpo común Octopus mimus del norte de Chile alimentado con dietas formuladas

The growth and survival of juvenile octopus, Octopus mimus, from northern Chile, fed three different diets were analyze during 57 days. Two of the diets (A and B) were wet diets stuffed in lamb gut with a gelatin solution, and the third (C) was a natural control. Diet (A) was a mixture of chopped fish meat (Cheilodactylus variegatus) and pellets of salmon meal; diet B was made up of clam (Protothaca thaca) mixed with C. variegatus meat; and diet (C) (control) consisted of fresh frozen clams. The experimental design was based on repetitive measures; the octopuses were supported individually 70-L tanks, with constant sea water circulation and aeration. The octopuses fed diet B did not registred mortality, whereas those fed the control (diet C) presented a mortality of 16.7%. Growth rates were similar (P > 0.05) for these two groups, with absolute growth rates (AGR) of 7.0 ± 0.91 (g d -1 ) and 6.6 ± 1.10 (g d -1 ), respectively. The octopuses fed diet A had a mortality of 33.3% and an AGR of -1.70 ± 0.37 (g d -1 ). Diet A, which contained pellets of ground salmon meal, was not well-accepted, and the weight of the octopuses in this group declined. Diet B, prepared with gelatin from animal origins, was no less palatable or acceptable than the control diet of fresh frozen clams, and the individuals in these two groups showed similar growth. These results will allow us to improve the nutritional quality of artificial diets in order to maximize the growth of O. mimus in captivity.

Oviducal glands throughout the gonad development stages: a case study of Octopus mimus (Cephalopoda)

ABSTRACT The oviducal glands (ODG) play a crucial role in octopus reproduction. Herein, structural changes of each section of the ODG of Octopus mimus are described histologically throughout the gonad development stages (GDS). To do this, the epithelial height, stereociliated or non-stereociliated epithelium, nucleus type (pycnotic or non-pycnotic), epithelial secretions and the value range of the macroscopic maturity index (MaMI), which directly involves ODG status, were measured. The ODG are internally constituted of two glandular units (central and peripheral glands) and one set of receptacles (the spermathecae). High epithelia (40 to 80 μm) were observed in both gland units during periods with low MaMI values (< 0.1) corresponding to III-mature and IV-pre-spawning. The stereociliated epithelium was only apparent in II-maturing and III-mature in both gland units. The nuclei were noticeably pycnotic in the central gland during III-mature, IV-pre-spawning and V-spawning, but pycnotic in the peripheral gland only during VI-depletion. The epithelium was disorganised during VI-depletion, while sulphated acid mucin was only present during III-mature in the central gland. The epithelium transformations during the GDS are related to the functions of the gland units and to their multiple secretions. The ODG histology complements the GDS and provides better reproductive status assessment.