Ontogenetic changes in digestive enzymatic capacities of the spider crab, Maja brachydactyla (Decapoda: Majidae)

Ontogenetic changes in digestive capabilities were analyzed in larvae and first juveniles of the spider crab Maja brachydactyla. Activities of five proteinases (total proteases, trypsin, chymotrypsin, pepsin-like and aminopeptidase), three carbohydrases (amylase, maltase and chitinase), an esterase and an alkaline phosphatase were studied to evaluate digestive enzyme profiles of the species. Both quantitative (spectrophotometry and fluorometry) and qualitative (SDS-PAGE) approaches were used. All assayed enzymes were active from hatching (zoea I-ZI) throughout larval development and in first juveniles. Significant variations during ontogeny were found only in total activities likely as a consequence of digestive system development. Specific activity varied little over ontogeny, being significant only for chitinase. Total proteases, trypsin and pepsin-like activities showed a similar pattern of increase as larval ontogeny advanced, decreasing significantly in juveniles. Chymotrypsin continued to increase, showing maximum activity after metamorphosis. Proteinase zymograms confirmed strong proteolytic activity in first zoeas, with increasing bands over the course of ontogeny, decreasing after metamorphosis. A group of bands with high molecular mass was specific to larval stages. Amylase and maltase showed a parallel pattern of continuous increase of total activity as development advanced. Gel-SDS-PAGE showed unchanged patterns of amylase activity in first zoeas of different ages and the most complex set of bands during larval ontogeny in second zoea. Esterase total activity increased significantly as ZI's aged likely reflecting introduction of a lipid-enriched diet. The importance of lipid accumulation at the beginning of ontogeny was also confirmed by the protease/esterase and amylase/esterase activity ratios, which decreased from hatch to late ZI and might be explained as an adaptation, ensuring the next molt. The results suggest that larvae of M. brachydactyla are capable of digesting a variety of dietary substrates as soon as they hatch.

Survival, development and growth of larvae of the blue swimmer crab, Portunus pelagicus, cultured under different photoperiod conditions

The blue swimmer crab is a commercially important species of the tropical Indo-Pacific regions that shows substantial potential as a candidate species for aquaculture. Optimization of larval rearing conditions, including photoperiod, is therefore important to establish a method for the intensive hatchery culture of this species. Newly hatched larvae of Portunuspelagicus in first zoeal stage (ZI) were reared under five photoperiod regimes 0L: 24D, 6L: 18D, 12L: 12D, 18L: 6D, and 24L: 0D (5 replicates per treatment) till they metamorphosed to megalopae (ranged from 8.5 ± 0.3 days (18L: 6D) to 10.8 ± 1.8 days (0L: 24D) at 29 ± 1 °C). Daily, larvae of each treatment were fed an identical diet of mixed rotifer and Artemia nauplii, and the survival and molt to successive stages was monitored. Newly hatched ZI larvae of P. pelagicus could successfully develop to the megalopal stage under all tested photoperiod conditions, but we detected significant differences in survival among treatments (p & 0.05). The constant darkness treatment (0L: 24D) had the lowest (19.2 ± 7.2%, mean ± S.E.) cumulative survival from ZI to the megalopal stage, while the 18L: 6D treatment achieved the highest survival (51.2 ± 23.6%). Similarly, the photoperiod significantly affected zoeal development. Constant darkness led to the longest cumulative zoeal duration (10.8 ± 1.8 days), whereas the 18L: 6D treatment rendered the shortest larval development (8.5 ± 0.3 days). In addition, larvae reared under constant darkness resulted in the smallest megalopae (carapace length = 1.44 ± 0.09 mm) and the lowest dry weight (0.536 ± 0.188 mg). In conclusion, photoperiod significantly affected the survival, development, and growth of P. pelagicus zoeal larvae. Constant darkness led to the lowest larval survival and developmental rate, while a photoperiod regime of 18L: 6D appeared to be the most suitable condition for the rearing of zoeal larvae of P. pelagicus.

Reducció de despeses ineficients i sostenibilitat de l'Estat del Benestar: el cas de Catalunya

Malgrat que el debat de l’Estat del Benestar està en el bell mig de l’actualitat política i econòmica des de fa uns quants anys amb graus ben diversos i aproximacions diferents, la darrera gran crisi ha disparat com mai la seva actualitat. Fins el present moment, amb algunes notables excepcions, totes les tendències han conduit a desenvolupar l’Estat del Benestar fins a extrems insostenibles. Això té explicacions múltiples i variades com les que s’aborden al llarg del present text. Aquestes tendències tenen una dinàmica econòmica i social pròpia que s’ha constatat amb força durant els darrers anys. Fa unes dues dècades que aquest debat va ser encetat amb profunditat per pocs països, però amb conclusions estimulants. Suècia és l’exemple més reeixit. La reforma duta a terme en el país nòrdics és una referència de primer ordre per molts estudiosos del tema i hauria de ser font d’inspiració per a la resta de països. Seguidament, hem volgut descriure, de forma complementària i des d’una perspectiva econòmica i jurídica, un fenomen estrictament lligat al desenvolupament imparable de l’Estat del Benestar, el de la burocratització. La reflexió d’acadèmics d’escoles en diferents i, en particular, els de la Public Choice proporcionen una visió rica i complexa, que entenem fonamental per avaluar els problemes que se’n deriven. Finalment, dins el marc de la Hisenda Pública i entrant en l’estudi concret del cas català, hem volgut endinsar-nos en l’anàlisi del pressupost. Essent com és una eina indispensable per avaluar el conjunt de polítiques econòmiques i socials d’un país. Aquesta anàlisi es duu a terme des d’una doble perspectiva: la primera, mitjançant un estudi comparatiu de l’evolució del Pressupost de la Generalitat dels darrers anys i, en segon terme, el canvi que el Pressupost 2011 materialitza aquest any, prefigura el de l’any 2012 i les principals crítiques de l’oposició. Queden oberts els camins envers els possibles canvis. De fet, res està definitivament escrit, però la pretensió d’aquest treball és modesta i, alhora, clara. Sense embuts, si volem mantenir un grau de benestar sostenible, és fonamental deixar de banda l’actual concepció de l’Estat del Benestar i començar a treballar per implementar els profunds canvis necessaris que donin pas a l’únic model que, a parer nostre, aconseguirà que això sigui possible: la Societat del Benestar. Una concepció actual del paper que ha de tenir l’Estat, de caràcter liberal i, alhora, social.

Characterization of larval moulting cycles in Maja brachydactyla (Brachyura, Majidae) reared in the laboratory

The moulting cycles of all larval instars (zoea I, zoea II, and megalopa) of the spider crab Maja brachydactyla Balss 1922 were studied in laboratory rearing experiments. Morphological changes in the epidermis and cuticle were photographically documented in daily intervals and assigned to successive stages of the moulting cycle (based on Drach's classification system). Our moult-stage characterizations are based on microscopical examination of integumental modifications mainly in the telson, using epidermal condensation, the degree of epidermal retraction (apolysis), and morphogenesis (mainly setagenesis) as criteria. In the zoea II and megalopa, the formation of new setae was also observed in larval appendages including the antenna, maxillule, maxilla, second maxilliped, pleopods, and uropods. As principal stages within the zoea I moulting cycle, we describe postmoult (Drach's stages A–B combined), intermoult (C), and premoult (D), the latter with three substages (D0, D1, and D2). In the zoea II and megalopa, D0 and D1 had to be combined, because morphogenesis (the main characteristic of D1) was unclear in the telson and did not occur synchronically in different appendices. The knowledge of the course and time scale of successive moult-cycle events can be used as a tool for the evaluation of the developmental state within individual larval instars, providing a morphological reference system for physiological and biochemical studies related to crab aquaculture.

La interpretació i l’argumentació en l’aprenentatge del pensament social crític: la construcció del pensament social crític mitjançant la pràctica de les habilitats cognitivolingüístiques d’interpretar i d’argumentar: una recerca aplicada a l’aula

Hi ha una arrelada corrent en l’ensenyament de les Ciències Socials que considera que aquesta matèria ha d’ajudar a potenciar, mitjançant el procés d’ensenyament i d’aprenentatge, el desenvolupament del pensament social crític (i el concepte associat del relativisme) entre l’alumnat. En aquesta línia, i com objecte de la recerca, és el valorar i avaluar la importància de l’ensenyament de les habilitats lingüístiques associades a continguts de Ciències Socials, en el desenvolupament del pensament social crític. Es treballen, essencialment, les habilitats lingüístiques: d’interpretar, de justificar i d’argumentar, i la seva correspondència amb tipologies textuals i orals.

Catalonia’s participation in calls of the EU 7th Framework Programme for RTD. Period 2007-2009

English translation of the Executive summary of the report “Catalonia’s participation in calls of the EU 7th Framework Programme for RTD. Period 2007-2009” drawn up by researchers of the AQR Research Group – Research Institute of Applied Economics (IREA) of the University of Barcelona. It aims to find out the reality of the Catalonia’s participation in the EU 7th Framework Programme, the main European financial instrument for research during the period 2007-2009.

Growth in a Cross-Section of Cities: Location, Increasing Returns or Random Growth?

This article analyzes empirically the main existing theories on income and population city growth: increasing returns to scale, locational fundamentals and random growth. To do this we implement a threshold nonlinearity test that extends standard linear growth regression models to a dataset on urban, climatological and macroeconomic variables on 1,175 U.S. cities. Our analysis reveals the existence of increasing returns when per-capita income levels are beyond $19; 264. Despite this, income growth is mostly explained by social and locational fundamentals. Population growth also exhibits two distinct equilibria determined by a threshold value of 116,300 inhabitants beyond which city population grows at a higher rate. Income and population growth do not go hand in hand, implying an optimal level of population beyond which income growth stagnates or deteriorates

Els germans Petrides a Barcelona : dos trompistes bohemis al Teatre de la Santa Creu (1794-1798)

Aquest treball documenta l’estada a Barcelona, entre el 1794 i 1798, dels germans Joseph i Peter Petrides, trompistes nascuts a Praga. L’excepcional trajectòria d’ambdós a la capital catalana, com a membres de l’orquestra del Teatre de la Santa Creu i com a solistes destacats, il·lustra el desenvolupament de l’ofici de músic a la ciutat durant l’última dècada del segle XVIII.