Development of thermal stratification and destratification scaling concepts. Volume 1: Definition of thermal stratification scaling parameters and experimental investigations

The dimensionless parameters associated with the thermal stratification and pressure history of a heated container of liquid and its vapor were examined. The Modified Grashof number, the Fourier number, and an Interface number were parameterized using a single test liquid, Freon 113. Cylindrical test tanks with spherical dome end caps were built. Blanket heaters covered the tanks and thermocouples monitored the temperatures of the liquid, the ullage, the tank walls, and the foam insulation encapsulating the tank. A centrifuge was used for the 6 inch tank to preserve the same scaling parameter values between it and the larger tanks. Tests were conducted over a range of Gr* values and the degree of scaling was checked by comparing the dimensionless pressures and temperatures for each scaled pair of tests. Results indicate that the bulk liquid temperature, the surface temperature of the liquid, and the tank pressure can be scaled with the three dimensionless parameters. Some deviation was, however, found in the detailed temperature profiles between the scaled pairs of tests

Egg development, hatching rhythm and moult patterns in Paralomos spinosissima (Decapoda: Anomura: Paguroidea: Lithodidae) from South Georgia waters (Southern Ocean)

Larval release, hatching rhythms and moult patterns were examined in a captive population of the subantarctic lithodid, Paralomis spinosissima from the South Georgia and Shag Rocks region. Larvae hatched throughout the year with the majority of females starting to release larvae at the end of the austral summer and beginning of autumn. Larval release continued over a period of up to 9 weeks with high variability in the numbers that hatched each day. A similar seasonal pattern to hatching was evident in the moulting of females. Intermoult period for two adult females (CL = 63 and 85 mm) ranged from 894 to 1,120 days while an intermoult period for males was estimated to be in excess of 832 days. The results are consistent with other species of Paralomis and are discussed in relation to physiological and environmental adaptations to the cold-water conditions south of the Antarctic Convergence

First year growth in the lithodids Lithodes santolla and Paralomis granulosa reared at different temperatures

The 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

Las centollas colonizan la Antartida

Es conocido que en Antartida no viven cangrejos. El hallazgo en los ultimo años de centolla podria estar anunciando la futura conquista de la Antartida por los cangrejos

Distribution and population structure of the crab Halicarcinus planatus (Brachyura, Hymenosomatidae) in the Beagle Channel, Tierra del Fuego

El cangrejo Halicarcinus planatus es el único himenosomátido que habita el extremo austral de Sudamérica, con una distribución subantártica, incluyendo las islas periantárticas y Nueva Zelanda. En este trabajo, se presenta información sobre la abundancia y estructura poblacional de H. planatus en el intermareal de Bahía Brown, Canal Beagle, Tierra del Fuego durante un año. Además, se muestran las variaciones en la estructura poblacional en otras playas y ambientes del canal. A diferencia de los machos, la densidad de hembras mostró fluctuaciones mensuales en el intermareal de Bahía Brown y fue mayor durante los meses de verano. Las altas densidades de H. planatus podrían relacionarse con la baja mortalidad de estadios larvales y las características oceanográficas de la bahía, probablemente aumentado por la presencia de bancos y cuerdas de cultivo de mejillones, sustratos donde ocurriría el asentamiento de H. planatus. La proporción de sexos poblacional estuvo sesgada hacia las hembras solo en verano, mientras que la proporción sexual operativa se sesgó hacia los machos durante casi todo el período estudiado, sugiriendo una fuerte competencia entre machos por el apareamiento. A su vez, los machos solo estuvieron presentes en el intermareal de Bahía Brown y en los grampones de Macrocystis pyrifera pero no se encontraron en el resto de los intermareales estudiados, probablemente relacionado con la ausencia de refugio en el submareal de Bahía Brown. El reclutamiento existiría en dos períodos diferentes, verano (enero-febrero) y otoño-invierno (mayo-junio), que se corresponde con las dos cohortes larvales de H. planatus presentes en el Canal Beagle.The crab Halicarcinus planatus is the only hymenosomatid that inhabits the southern tip of South America and has a sub-Antarctic distribution, including the peri-Antarctic islands and New Zealand. In this paper, we report the abundance and population structure of H. planatus for a year in the intertidal zone of Bahía Brown, Beagle Channel, Tierra del Fuego. Moreover, we show variations in the population structure in other beaches and environments of the channel. In contrast with males, female density showed monthly variations and was higher during austral summer months. High densities of H. planatus could be related with low mortality during the larval stage and oceanographic features of Bahía Brown, probably enhanced by the presence of both culture and mussel beds, substrates where settlement would occur. The populational sex ratio was biased towards females only in summer, while the operational sex ratio was biased towards males during all periods studied, suggesting strong competition among males for mating. In turn, males were present only in the intertidal zone of Bahía Brown and Macrocystis pyrifera but were absent in the other studied intertidal areas.This is perhaps related to the lack of shelter in the subtidal zone of Bahía Brown. Recruitment occurs in two different periods, summer (January-February) and autumn-winter (May-June), which corresponds with the two larval cohorts of H. planatus in the Beagle Channel.Fil: Diez, Mariano Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Florentin, Olga Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Lovrich, Gustavo Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentin

Defensas antioxidantes y peroxidación de lípidos en dos especies de Lithodes del Atlántico Sur durante el verano

En el sur de Sudamérica Lithodes santolla y L. confundens representan las especies de centollas más apreciadas, debido a sus altos rendimientos y aceptación en los mercados. Desde un punto de vista fisiológico, las especies reactivas del oxígeno (ROS) son continuamente producidas como productos de la respiración celular. Estos ROS se transforman en metabolitos menos tóxicos por medio de enzimas antioxidantes. El objetivo fue determinar en Lithodes santolla (del Golfo San Jorge) y L. confundens (de la costa atlántica de Tierra del Fuego) el nivel de base de la actividad enzimática antioxidante y los niveles de peroxidación de lípidos. Las enzimas catalasa (CAT) y glutatión-S-transferasa (GST) y la peroxidación de lípidos se midieron en branquias, músculo y hepatopáncreas. Ambas especies mostraron actividad enzimática antioxidante, mientras que las branquias presentaron la mayor actividad enzimática de CAT. La actividad de CAT y GST fue mayor en L. confundens en el músculo y branquias respectivamente, comparado con L. santolla; mientras que la peroxidación de lípidos fue menor en ambos órganos. Estas diferencias entre ambas especies sugieren que L. confundens sería más eficiente ante situaciones de estrés oxidativo, debido probablemente a los periodos de anoxia que experimenta durante las bajas mareas de primavera. Además, estas diferencias podrían ser atribuidas a características intrínsecas de adaptación de cada especie de centolla y/o a condiciones ambientales de cada área de estudio en particular. Parámetros como CAT, GST y peroxidación de lípidos podrían proponerse como biomarcadores de estrés oxidativo en Lithodes santolla y L. confundens.In Southern South America Lithodes santolla and L. confundens are the most valuable king crabs species, specially due to their high yields and their high acceptance in the markets. From a physiological point of view, reactive oxygen species (ROS) are continuously produced as by-products of cell respiration. These ROS are transformed into less toxic metabolites by antioxidant enzymes. The aim of the present study was to determine in Lithodes santolla (from San Jorge Gulf) and L. confundens (from Atlantic coast of Tierra del Fuego) the baseline status of both antioxidant enzyme activity and lipid peroxidation levels. Activities of catalase (CAT), glutathione-S-transferase (GST), as well as lipid peroxidation were measured in the muscle, gills and hepatopancreas. Both species showed antioxidant enzyme activities, and the gills were the organs with the highest CAT enzyme activities. CAT and GST activities were higher in muscle and gills, respectively, in L. confundens compared with L. santolla, whereas lipid peroxidation was low in both organs. These differences between both species suggest that L. confundens is more capable to afford oxidative stress than L. santolla, which may be a response to the common occurrence of L. confundens at the intertidal during the spring low tides. Differences in the analysed parameters could be attributed to intrinsic adaptation features of each king crab species and/or to environmental conditions of each particular study area. Furthermore, our results showed that parameters as CAT, GST and lipid peroxidation could be proposed as biomarkers of oxidative stress in Lithodes santolla and L. confundens.Fil: Romero, Maria Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina;Fil: Schvezov, Natasha. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina;Fil: Sotelano, María Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina;Fil: Diez, Mariano Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina;Fil: Florentin, Olga Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina;Fil: Tapella, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina;Fil: Lovrich, Gustavo Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina

Estacionalidad de larvas de Brachyura y Anomura (Crustacea Decapoda) en el Canal del Beagle, Argentina

This is the first study in the Beagle Channel that reports the larval seasonal distribution, abundance and duration of the larval stages of Anomura and Brachyura, on the basis of a fortnightly sampling programme. An identification key to the specific level of zoeal stages is included. Between September 1987 and March 1989, 304 plankton samples were taken by means of oblique hauls from the bottom to the sea-surface. Eighty-five percent of the samples were taken shallower than 60 m depth. Decapod larvae occurred only in spring and summer. All but two taxa showed a single cohort of larvae which emerge at the beginning of the spring. A second cohort of Munida spp. and Halicarcinus planatus also occurred during summer. The most abundant taxa were Munida spp. (312 larvae ? 10 m-3), Peltarion spinosulum (288 larvae ? 10 m-3),), H. planatus (143 larvae ? 10 m-3),) and Pagurus spp. (79 larvae ? 10 m-3), which represented 97% of the total larvae collected. Larvae of Pinnotheridae, Eurypodius latreillii, Libidoclaea granaria, and Paralomis granulosa were about an order of magnitude less abundant. Relative abundances of larvae correspond to relative abundances of the respective benthic stages. The absence of certain larval stages or of certain species (Acanthocyclus albatrossis and Lithodes santolla) probably indicates their differential distribution within the Beagle Channel. Particularly, lithodid larvae may have benthic or epibenthic habits.En este artículo se presenta la distribución estacional, abundancia y duración de los estadios larvales de los Anomura y Brachyura presentes en el plancton del Canal del Beagle, Argentina, sobre la base de muestreos quincenales. Se incluye además una clave para la identificación de los estadios zoea al nivel taxonómico de especie. Entre septiembre de 1987 y marzo de 1989, se tomaron 304 muestras de plancton, la mayoría provenientes de lances oblícuos desde el fondo hasta la superficie del mar. El 85% de las muestras se tomaron a < 60 m de profundidad. Las larvas estuvieron presentes sólo en primavera y en verano. Todos los taxa excepto dos presentaron una cohorte que provino de la eclosión de los huevos que ocurrió a comienzos de la primavera. Munida spp. y Halicarcinus planatus presentaron también una segunda cohorte durante el verano. Los taxa más abundantes fueron Munida spp. (312 larvas • 10 m-3), Peltarion spinosulum (288 larvas • 10 m-3), H. planatus (143 larvas • 10 m-3) y Pagurus spp. (79 larvas • 10 m-3), y representaron el 97% de las larvas recolectadas. Las larvas de Pinnotheridae, Eurypodius latreillii, Libidoclaea granaria, y Paralomis granulosa fueron aproximadamente un orden de magnitud menos abundantes que las anteriores. La abundancia relativa de las larvas se corresponde aproximadamente con la abundancia relativa de los estadios bentónicos de los respectivos taxones. La ausencia de ciertos estadios larvales o de ciertas especies (Acanthocyclus albatrossis y Lithodes santilla) podría ser debida a una distribución diferencial de las larvas de anomuros y braquiuros dentro del Canal del Beagle. En particular, debido a la ausencia de las larvas de Lithodidae en el plancton se plantea la hipótesis de que sean bentónicas o epibentónicas

Climate Change and invasibility of the Antarctic benthos

Benthic communities living in shallow-shelf habitats in Antarctica (&lt;100-m depth) are archaic in their structure and function. Modern predators, including fast-moving, durophagous (skeleton-crushing) bony fish, sharks, and crabs, are rare or absent; slow-moving invertebrates are the top predators; and epifaunal suspension feeders dominate many soft substratum communities. Cooling temperatures beginning in the late Eocene excluded durophagous predators, ultimately resulting in the endemic living fauna and its unique food-web structure. Although the Southern Ocean is oceanographically isolated, the barriers to biological invasion are primarily physiological rather than geographic. Cold temperatures impose limits to performance that exclude modern predators. Global warming is now removing those physiological barriers, and crabs are reinvading Antarctica. As sea temperatures continue to rise, the invasion of durophagous predators will modernize the shelf benthos and erode the indigenous character of marine life in Antarctica

Potencial reproductivo de los litodidos Lithodes santolla y Paralomis granulosa (Anomura, Decapoda) en el Canal del Beagle, Argentina

Lithodidae is the only group of reptant decapods that occurs in Antarctic waters and has been particularly abundant in the Beagle Channel, Straits of Magellan and south to 50º S. Because of their abundance in coastal waters, the sympatric Lithodes santolla and Paralomis granulosa have constituted a mixed fishery since the 1930s. The two species differ markedly in their reproductive potential. Lithodes santolla is large (maximum size of 190 mm carapace length, CL, and 8 kg weight), has a generation time of 6 yrs., the reproductive cycle is annual and females carry between 5,000-60,000 eggs per female per clutch. In their life span, L. santolla females produce 6 times more eggs than P. granulosa females. Paralomis granulosa is smaller than its relative (maximum 115 mm CL and 1.5 kg weight), and has a slower growth rate, resulting in a generation time of 12 yrs. The reproductive cycle is biennial and females carry between 800-10,000 eggs per female per clutch. Moreover, the reproductive potential of P. granulosa is reduced because an important proportion of the largest and more prolific females of the population do not carry eggs. In other terms, in one generation time of P. granulosa, two complete generations of L. santolla are produced, and compared to other Subantarctic lithodids L. santolla is the most prolific species. The higher reproductive potential of L. santolla probably confers to this species the ability to recover more rapidly from an overfishing situation.Lithodidae es el único grupo de crustáceos reptantes presente en aguas antárticas y ha sido particularmente abundante en el Estrecho de Magallanes, Canal del Beagle y al sur de los 50º de latitud. Debido a su abundancia en aguas costeras, las especies simpátricas Lithodes santilla y Paralomis granulosa han constituído una pesquería mixta desde la década de 1930. Ambas especies difieren en su potencial reproductivo. Lithodes santolla es más grande (tamaño máximo de 190 mm de largo de caparazón, LC, y 8 kg de peso), su tiempo de generacion es de 6 años, el ciclo reproductivo es anual y las hembras llevan entre 5.000-60.000 huevos por puesta. Durante su vida reproductiva, las hembras de L. santolla producen 6 veces más huevos que las hembras de P. granulosa. Los individuos de esta especie son más pequeños (tamaño máximo 115 mm LC y 1,5 kg de peso), y tienen una tasa de crecimiento más lenta, que resulta en un tiempo de generacion de aproximadamente 12 años. El ciclo reproductivo es bienal y las hembras llevan entre 800-10.000 huevos por puesta. Además, el potencial reproductivo de P. granulosa está reducido porque una proporción importante de las hembras más grandes, y consecuentemente más prolíficas, no portan huevos. En otros términos, en el transcurso de un tiempo de generacion de P. granulosa se producen dos generaciones completas de L. santolla. Asimismo, comparada con otros litódidos subantárticos L. santolla es la especie más prolífica, y comparativamente con P. granulosa, su potencial reproductivo más alto la capacitaría para recuperarse más rapidamente de una situación de sobrepesca

Temperature effects on zoeal morphometric traits and intraspecific variability in the hairy crab Cancer setosus across latitude

International audiencePhenotypic plasticity is an important but often ignored ability that enables organisms, within species-specific physiological limits, to respond to gradual or sudden extrinsic changes in their environment. In the marine realm, the early ontogeny of decapod crustaceans is among the best known examples to demonstrate a temperature-dependent phenotypic response. Here, we present morphometric results of larvae of the hairy crab , the embryonic development of which took place at different temperatures at two different sites (Antofagasta, 23°45′ S; Puerto Montt, 41°44′ S) along the Chilean Coast. Zoea I larvae from Puerto Montt were significantly larger than those from Antofagasta, when considering embryonic development at the same temperature. Larvae from Puerto Montt reared at 12 and 16°C did not differ morphometrically, but sizes of larvae from Antofagasta kept at 16 and 20°C did, being larger at the colder temperature. Zoea II larvae reared in Antofagasta at three temperatures (16, 20, and 24°C) showed the same pattern, with larger larvae at colder temperatures. Furthermore, larvae reared at 24°C, showed deformations, suggesting that 24°C, which coincides with temperatures found during strong EL Niño events, is indicative of the upper larval thermal tolerance limit.   is exposed to a wide temperature range across its distribution range of about 40° of latitude. Phenotypic plasticity in larval offspring does furthermore enable this species to locally respond to the inter-decadal warming induced by El Niño. Morphological plasticity in this species does support previously reported energetic trade-offs with temperature throughout early ontogeny of this species, indicating that plasticity may be a key to a species' success to occupy a wide distribution range and/or to thrive under highly variable habitat conditions