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Artificial cultivation increases clams' availability and is an alternative to the extraction from natural banks. The culture of clams requires species-specific research in the different growth stages, and studies on the effects and interactions of culture parameters are essential to obtain and control the proper development of larvae. This paper aims to compare methods to induce spawning, describe the embryonic development, and compare the effect of different culture densities on the yield of "D" larvae of the "taca" clam Ameghinomya antiqua. Breeders were collected on the southwest coast of Quinchao Island, Chiloé, Chile. Spawning induction assays were performed comparing different combinations of biological and physical factors. Experiments on the effect of embryonic density in the obtention of "D" larvae were performed, and the embryonic development was described at 11 ± 1°C. The spawning inductions were successfully achieved with the addition of food combined with temperature changes, resulting in the liberation of oocytes with a jelly coat with a diameter of 140 µm. Trochophore larvae were observed at 40 h post-fertilization. The percentage of embryos developed showed significant differences when testing cultures with densities of 20, 40, and 60 embryos mL-1. Experiments with 20 embryos mL-1 density were the ones that obtained a greater number of developed embryos (50%). These results suggest spawning induction with the addition of food and temperature changes with a density of 20 embryos mL-1. This paper describes the embryonic development and technology development for spawning induction for the first time. [ABSTRACT FROM AUTHOR]

Several types of development are reported in the worldwide distributed Family Calyptraeidae. In species with direct development, embryos can grow from large eggs or can feed on nurse eggs, nurse embryos, or other intracapsular nutritional resources. Here the reproductive mode of Trochita pileolus and how biochemical composition varies among egg size between three species of Trochita were studied. Adults and broods of T. pileolus were collected off Tierra del Fuego and nearby Burdwood Bank at depths of 96–151 m. The mean shell diameter of brooding females was 16.3 ± 2 mm and the number of egg capsules observed ranged from 5 to 9. In each egg capsule 7–10 embryos developed from uncleaved eggs of about 500 µm diameter. Neither nurse eggs nor other kinds of extraviteline food sources were recorded. No oophagy, adelphophagy, or late intracapsular cannibalism were observed. The development mode of T. pileolus closely resembles that of the giant T. trochiformis from Chile, in which the energy for developing embryos is obtained from large fertile eggs. The eggs of T. trochiformis had higher lipid content than the other two species and were more energy-dense than glycogen-enriched eggs. The relative lipid coverage area and the hatching size of T. pileus were similar to T. pileolus, although the egg size was three times smaller. This could be attained because T. pileus has developed intracapsular nutritional resources such as nurse eggs and adelphophagy. [ABSTRACT FROM AUTHOR]

This article, excerpt from the doctoral thesis of one of the authors, aims to discuss the principle of dialogicity as a vector of Freirian thought from the historical context of the fac-similada publication of the manuscript of the Pedagogy of the Oppressed. The historical context in which the work was created in Chile between 1967 and 1968 is recovered, describing the itinerary followed until the first publication in 2013. It is a qualitative research of theoreticalanalytical nature based on contributions coming primarily from discourse analysis and genetic criticism. In the manuscript, the matrix embryo of what could be called the Pedagogy of the Educommunicative Dialogue was found, woven with the oppressed and not for the oppressed. It can be concluded that the manuscript opens new possibilities for the 21st century reader, both for the appropriation of new meanings for the work and for its historical validation. [ABSTRACT FROM AUTHOR]

The kodkod (Leopardus guigna) is a small felid endemic of Chile and is considered a vulnerable species. Domestic cat oocytes have been successfully used as recipient cytoplast to reprogram somatic cells from different felids by interspecific somatic cell nuclear transfer (iSCNT). The developmental competence of felid embryos generated by iSCNT can be improved by the aggregation method using a zona-free culture system. The objective of this research was to evaluate the developmental competence of kodkod embryos generated by iSCNT using domestic cat oocytes and the aggregation method. For this purpose, five experimental group were done: (1) cat embryos generated by IVF, (2) cat embryos generated by SCNT (Ca1x), (3) aggregated cat embryos generated by SCNT (Ca2x), (4) kodkod embryos generated by iSCNT (K1x) and (5) aggregated kodkod embryos generated by iSCNT (K2x). Cleavage, morulae and blastocyst rates were estimated. The blastocyst diameter was evaluated. The gene expression level of pluripotency (OCT4 , SOX2 and NANOG) and differentiation markers (CDX2 and GATA6) was analyzed in blastocysts. Morulae rate was higher in the IVF group and when cloned embryos were cultured in aggregates (IVF: 68.2%, Ca2x: 58.0% and K2x: 62.4%) compared to individually cultured kodkod embryos (K1x: 37.0%) (P < 0.05). Embryo aggregation increased blastocysts formation in the Ca2x group (30.9%) to a similar rate compared to the IVF group (44.5%) (P > 0.05). No blastocysts were generated in the K1x group, whereas blastocysts formation was obtained in K2x group (5.9%). The diameter of blastocysts from the K2x group (172.8 μm) was significantly lower than blastocysts from the Ca2x group (P < 0.05). The relative expression of OCT4 was lower in blastocysts from Ca1x than in blastocysts from IVF (P < 0.05). Furthermore, CDX2 expression was lower in blastocysts from Ca2x than in blastocysts from Ca1x and IVF groups (P < 0.05). In kodkod embryos, only one blastocyst from the K2x group expressed OCT4. No expression of SOX2 , NANOG , CDX2 and GATA6 was detected in kodkod blastocysts. In conclusion, after iSCNT, domestic cat oocytes support the development of kodkod embryos until the morula stage. The aggregation method increases the morulae rate of kodkod cloned embryos and allows blastocysts formation. However, kodkod blastocysts have a poor morphological quality and a lacking expression of pluripotency and differentiation markers, probably caused by an incomplete nuclear reprogramming. • The production of kodkod (Leopardus guigna) embryos by iSCNT was evaluated. • Embryo aggregation was used to improve the developmental capacity of cloned embryos. • The aggregation method increases the developmental capacity of domestic cat and kodkod cloned embryos. • Kodkod blastocysts have reduced morphological quality compared to domestic cat. • Kodkod blastocysts have a lacking expression of pluripotency and differentiation markers. [ABSTRACT FROM AUTHOR]

The estuarine crab Hemigrapsus crenulatus has a wide distribution range along the coast of the South Pacific Ocean (from 20 °S to 53 S°). This decapod is abundant in these coastal and estuarine habitats and plays a key ecological role as prey of the snook fish (Eleginops maclovinus) and kelp gull (Larus dominicanus). Its diet consists of detritus, dead fish, and crustaceans, and the macroalgae Ulva sp. In response to contrasting environmental conditions and anthropogenic impacts along the Chilean coast, H. crenulatus may present intraspecific variations in its reproductive traits and changes in the elemental composition of its embryos, directly affecting its biological fitness. Along the Chilean coast, female individuals were collected during late spring 2019 and early summer 2020 (from November 2019 to February 2020) in six areas of Chile (north: Tongoy (30°S); south-central: Lenga (36°S), Tubul (37°S); south austral: Calbuco (41°S), Castro (42°S), Quellón (43°S). The environmental conditions (i.e. sea surface temperature, precipitation and chlorophyll α) present during each sampling event were also recorded. We evaluated the reproductive parameters of females (fecundity, reproductive output (RO)) as well as their body size (carapace width and dry weight), volume, water content, dry weight, elemental composition (carbon, hydrogen, nitrogen: CHN), and finally the energy content of their embryos. Our results indicated that the environmental conditions of the sea water temperature, precipitation (proxy of water salinity) and chlorophyll α (proxy of food availability) have direct effects on the reproductive parameters of females and the characteristics of their embryos. We observed a low fecundity and high RO in Calbuco and Quellón, where precipitation was high (i.e. diluted salinity) and temperatures and productivity was low. For embryo traits, the highest values of volume and water content were observed in female crabs from the estuarine areas (i.e. Tongoy, Lenga, Tubul), values much higher than those found in the internal sea of Chile (i.e. Calbuco, Castro, Quellón). For the elemental composition, we observed high nitrogen levels and a low C:N proportion in embryos from female crabs from Lenga (a nitrogen enriched area). Fluctuating environmental variables among localities proved to modulate intraspecific variations in females and embryos of H. crenulatus , revealing different reproductive strategies, particularly in the quality and energy investment per embryo, which subsequently influenced successful embryogenesis and larval survival. • Temperature is a key driver determining female and embryo traits. • Food supply may affects female reproductive traits. • Salinity may promotes intraspecific variation in embryos. • Anthropogenic impact has implications in the elemental composition. [ABSTRACT FROM AUTHOR]

In the Seno de Reloncaví, southern Chile, seasonal changes in dry weight (DW) and elemental composition (CHN) were studied in embryo (initial embryonic stage), newly hatched zoeae, and newly settled megalopae of a porcelain crab, Petrolisthes laevigatus. Samples were taken throughout the seasons of egg laying (March-December), hatching (August-February), and settlement (October-February). Values of DW and CHN per embryo or larva, respectively, were consistently minimum in the middle of each season and maximum near its beginning and end. Patterns of seasonal variation in early embryonic biomass may thus be carried over to larvae at hatching and, possibly, to the settlement stage. Such carry-over effects may be selectively advantageous, as zoeae released at the beginning or near the end of the hatching season face conditions of poor planktonic food availability in combination with low winter temperatures or decreasing temperatures at the end of summer (enforcing long development duration). Hence, an enhanced female energy allocation into egg production may subsequently translate to enhanced yolk reserves remaining at hatching, allowing for a larval development under unfavourable winter conditions. In summer, by contrast, plankton productivity and temperatures are generally high, allowing for fast larval growth and development. This coincides with minimal biomass and energy contents both at hatching and settlement. In conclusion, our data suggest that seasonal patterns in the biomass of early developmental stages of P. laevigatus may reflect phenotypic variability as an adaptive response to predictable variations in environmental conditions, allowing this species to reproduce in temperate regions with marked seasonality in water temperature and plankton productivity. [ABSTRACT FROM AUTHOR]

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