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First year growth in the lithodids Lithodes santolla and Paralomis granulosa reared at different temperatures
No full textThe southern king crab, Lithodes santolla Molina, and stone crab, Paralomis granulosa Jacquinot, inhabit the cold-temperate waters of southernmost South America (southern Chile and Argentina), where stocks of both species are endangered by overfishing. Recent investigations have shown that these crabs show life-cycle adaptations to scarcity of food and low temperatures prevailing in subantarctic regions, including complete lecithotrophy of all larval stages and prolonged periods of brooding and longevity. However, growth and development to maturity are slow under conditions of low temperatures, which may explain the particular vulnerability of subpolar lithodids to fisheries. In the present study, juvenile L. santolla and P. granulosa were individually reared in the laboratory at constant temperatures ranging from 3–15 °C, and rates of survival and development through successive instars were monitored throughout a period of about nine months from hatching. When the experiments were terminated, L. santolla had maximally reached juvenile instar IV (at 6 °C), V (9 °C), or VII (15 °C). In P. granulosa the maximum crab instar reached was II (at 3 °C), V (6 °C), V (9 °C), or VII (15 °C). The intermoult period decreased with increasing temperature, while it increased in successively later instars. In consequence, growth rate showed highly significant differences among temperatures (P<0.001). Growth-at-moult was highest at 9 °C. Rates of survival decreased significantly in juvenile P. granulosa with increasing temperature. Only at 15 °C in L. santolla, was a significantly enhanced mortality found compared with lower temperatures. Our results indicate that juvenile stages of L. santolla and P. granulosa are well adapted to 5–10°C, the range of temperatures typically prevailing in subantarctic marine environments. In spite of causing higher mortality rates, higher rearing temperatures (12–15 °C) should accelerate the rates of growth and maturation, which may be favourable for projects aiming at aquaculture or repopulation of overexploited king crab stocks
Changes in biomass and chemical composition during lecithotrophic larval development of the southern king crab, Lithodes santolla (Molina)
No full textChanges in biomass and elemental composition (dry mass, W; carbon, C; nitrogen, N; hydrogen, H) were studied in the laboratory during complete larval and early juvenile development of the southern king crab, Lithodes santolla (Molina), formerly known as Lithodes antarcticus (Jacquinot). At 6±0.5 °C, total larval development from hatching to metamorphosis lasted about 10 weeks, comprising three demersal zoeal stages and a benthic megalopa, with mean stage durations of 4, 7, 11 and 47 days, respectively. No differences in development duration or mortality were observed in larvae either fed with Artemia sp. nauplii or unfed, indicating that all larval stages of L. santolla are lecithotrophic. First feeding and growth were consistently observed immediately after metamorphosis to the first juvenile crab stage. Regardless of the presence or absence of food, W, C, N and H decreased throughout larval development. Also the C:N mass ratio decreased significantly, from 7.7 at hatching to 4.1 at metamorphosis, indicating that a large initial lipid store remaining from the egg yolk was gradually utilized as an internal energy source, while proteins played a minor role as a metabolic substrate. In total, 56–58% of the initial quantities of C and H present at hatching, and 20% of N were lost during nonfeeding larval development to metamorphosis. Nine to ten percent of the initially present C, N and H were lost with larval exuviae, half of these losses occurring in the three zoeal stages combined and another half in the megalopa stage alone. Metabolic biomass degradation accounted for losses of about 47–50% in C and H but for only 10% in N. Hence, most of the losses in C and H reflected metabolic energy consumption (primarily lipid degradation), while about half of the losses in N and two thirds of those in W were due to larval exuviation. Complete independence from food throughout larval development is based on an enhanced maternal energy investment per offspring and on energy-saving mechanisms such as low larval locomotory activity and low exuvial losses. These traits are interpreted as bioenergetic adaptations to food-limited conditions in Subantarctic regions, where a pronounced seasonality of day length limits the period of primary production, while low temperatures enforce a long duration of pelagic development. <br/
Cisti ossee di calcagno (Studio di 14 osservazioni)
No full textCisti ossee di calcagno (Studio di 14 osservazioni)
Larval and early juvenile development of Lithodes santolla (Molina, 1782) (Decapoda: Anomura: Lithodidae) reared at different temperatures in the laboratory
No full textThe southern king crab, Lithodes santolla Molina, is distributed in cold-temperate and subantarctic waters ranging from the southeastern Pacific island of Chiloé (Chile) and the deep Atlantic waters off Uruguay, south to the Beagle Channel (Tierra del Fuego, Argentina/Chile). Recent investigations have shown that its complete larval development from hatching to metamorphosis, comprising three zoeal stages and a megalopa, is fully lecithotrophic, i.e. independent of food. In the present study, larvae were individually reared in the laboratory at seven constant temperatures ranging from 1 to 18 °C, and rates of survival and development through successive larval and early juvenile stages were monitored throughout a period of 1 year. The highest temperature (18 °C) caused complete mortality within 1 week; only a single individual moulted under this condition, 2 days after hatching, to the second zoeal stage, while all other larvae died later in the zoea I stage. At the coldest condition (1 °C), 71% of the larvae reached the zoea III stage, but none of these moulted successfully to a megalopa. A temperature of 3 °C allowed for some survival to the megalopa stage (17–33% in larvae obtained from two different females), but only a single individual passed successfully, 129 days after hatching, through metamorphosis to the first juvenile crab instar. At all other experimental conditions (6, 9, 12 and 15 °C), survival through metamorphosis varied among temperatures and two hatches from 29% to 90% without showing a consistent trend. The time of nonfeeding development from hatching to metamorphosis lasted, on average, from 19 days at 15 °C to 65 days at 6 °C. The relationship between the time of development through individual larval or juvenile stages (D) and temperature (T) was described as a power function (D=aTb, or log[D]=log[a]blog[T]). The same model was also used to describe the temperature dependence of cumulative periods of development from hatching to later larval or juvenile stages. One year after hatching, the 7th (6 °C) to 9th (15 °C) crab instar was reached. Under natural temperature conditions in the region of origin of our material (Beagle Channel, Argentina), L. santolla should reach metamorphosis in October–December, i.e. ca. 2 months after hatching (taking place in winter and early spring). Within 1 year from hatching, the crabs should grow approximately to juvenile instars VII–VIII. Our results indicate that the early life-history stages of L. santolla tolerate moderate cold stress as well as planktonic food-limitation in winter, implying that this species is well adapted to subantarctic environments with low temperatures and a short seasonal plankton production. <br/
Discurso del embajador argentino en la undécima conferencia de la UNESCO en París, 1960 : Alfredo Domingo Calcagno habla sobre la educación
No full textEl embajador argentino ante la UNESCO, Alfredo Domingo Calcagno, habla en la conferencia anual, en París, en 1960. Se refiera a la labor del organismo, a la educación y la alfabetización. Destaca la educación argentina con la figura fundacional de Domingo Faustino Sarmiento. Luego describe los adelantos científicos tecnológicos de la época, así como a la función de la UNESCO a la hora de igualar las oportunidades de las distintas naciones en su aprovechamiento. Enfatiza en la realidad latinoamericana al respecto.
Alfredo Domingo Calcagno: nació en Mercedes, provincia de Buenos Aires el 26 de octubre de 1891. Fue rector del Colegio Nacional "Rafael Hernández" en 1934 y presidente de la Universidad Nacional de La Plata entre 1945 y 1946. Fue diputado nacional y embajador argentino ante la Organización de las Naciones Unidas para la educación, la Ciencia y la Cultura. Como pedagogo, fue continuador y discípulo de Víctor Mercante.Radio Universidad Nacional de La Plat
Genova, Livorno, Civitavecchia, Venezia: prove di comparazione sulla frode doganale a partire dalla documentazione di quattro archivi (XVIII secolo)
No full textDigestive enzymes in the ontogenetic stages of the southern king crab, Lithodes santolla
No full textThe early ontogenetic stages of the sub-Antarctic king crab Lithodes santolla were analyzed for the presence and activities of a set of important digestive enzymes. The eggs and non-feeding larvae (zoea I-III, megalopa) showed high activities of esterases, phosphatases, and exopeptidases indicating the enzymatic ability to utilize endogeneous yolk reserves. SDS-PAGE showed a continuous decrease of proteins or proteids in the range of 59–81 kDa during ontogenetic development from the eggs through the zoeal stages to the first juvenile crab stage, CI. This reduction reflects the degradation of storage compounds during lecithotrophic larval development. Activities of the endopeptidases, trypsin and chymotrypsin, were low in eggs and larvae but increased significantly in the first juvenile crab stage. These enzymes typically facilitate the first steps of proteolysis in the extra-cellular spaces of the midgut gland and in the stomach. Their scarcity indicates that the larvae of L. santolla are physiologically not prepared to digest external food. This ability seems to appear first in the CI stage. Extracts of juvenile midgut glands and the gastric fluids of adults showed high activities of a variety of digestive enzymes including phosphatases, carbohydrases, as well as endo- and exopeptidases. High activities of digestive enzymes in adults may compensate for scarce food supply and rate-limiting low temperatures in the predominantly sub-Antarctic habitats of L. santolla
Discurso del embajador argentino en la undécima conferencia de la UNESCO en París, 1960 : Alfredo Domingo Calcagno habla sobre la educación
No full textEl embajador argentino ante la UNESCO, Alfredo Domingo Calcagno, habla en la conferencia anual, en París, en 1960. Se refiera a la labor del organismo, a la educación y la alfabetización. Destaca la educación argentina con la figura fundacional de Domingo Faustino Sarmiento. Luego describe los adelantos científicos tecnológicos de la época, así como a la función de la UNESCO a la hora de igualar las oportunidades de las distintas naciones en su aprovechamiento. Enfatiza en la realidad latinoamericana al respecto.
Alfredo Domingo Calcagno: nació en Mercedes, provincia de Buenos Aires el 26 de octubre de 1891. Fue rector del Colegio Nacional "Rafael Hernández" en 1934 y presidente de la Universidad Nacional de La Plata entre 1945 y 1946. Fue diputado nacional y embajador argentino ante la Organización de las Naciones Unidas para la educación, la Ciencia y la Cultura. Como pedagogo, fue continuador y discípulo de Víctor Mercante.Radio Universidad Nacional de La Plat
leonardo-calcagno/MISSAR: Code for the article "The Emergency Family Income in Argentina (IFE): could it become a permanent safety net?
No full textIncludes all code relative to MISSAR projections. For code relative to the IFE article, see README- EXECUTE IFE RELEASE. The article has been submitted for publication to the International Journal of Microsimulation
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