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BackgroundMale European seabass, already predominant (~ 70%) in cultured stocks, show a high incidence (20–30%) of precocious sexual maturation under current aquaculture practices, leading to important economic losses for the industry. In view of the known modulation of reproductive development by swimming exercise in other teleost species, we aimed at investigating the effects of sustained swimming on reproductive development in seabass males during the first year of life in order to determine if swimming could potentially reduce precocious sexual maturation.MethodsPre-pubertal seabass (3.91 ± 0.22 g of body weight (BW)) were subjected to a 10 week swimming regime at their optimal swimming speed (Uopt) in an oval-shaped Brett-type flume or kept at rest during this period. Using Blazka-type swim tunnels, Uopt was determined three times during the course of the experiment: 0.66 m s− 1 at 19 ± 1 g BW, 10.2 ± 0.2 cm of standard length (SL) (week 1); 0.69 m s− 1 at 38 ± 3 g BW, 12.7 ± 0.3 cm SL (week 5), and also 0.69 m s− 1 at 77 ± 7 g BW, 15.7 ± 0.5 cm SL (week 9). Every 2 weeks, size and gonadal weight were monitored in the exercised (N = 15) and non-exercised fish (N = 15). After 10 weeks, exercised and non-exercised males were sampled to determine plasma 11-ketotestosterone levels, testicular mRNA expression levels of genes involved in steroidogenesis and gametogenesis by qPCR, as well as the relative abundance of germ cells representing the different spermatogenic stages by histological examination.ResultsOur results indicate that sustained swimming exercise at Uopt delays testicular development in male European seabass as evidenced by decreased gonado-somatic index, slower progression of testicular development and by reduced mRNA expression levels of follicle stimulating hormone receptor (fshR), 3-beta-hydroxysteroid dehydrogenase (3βhsd), 11-beta hydroxysteroid dehydrogenase (11βhsd), estrogen receptor-beta (erβ2), anti-mullerian hormone (amh), structural maintenance of chromosomes protein 1B (smc1β), inhibin beta A (inhba) and gonado-somal derived factor 1 (gsdf1) in exercised males as compared with the non-exercised males.ConclusionsSwimming exercise may represent a natural and non-invasive tool to reduce the incidence of sexually precocious males in seabass aquaculture.

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Optically stimulated X-ray diffraction (OSXRD) modifies a traditional powder XRD by attaching a thermocouple, a precision temperature controller (PID control), and a thyristor power regulator firing a halogen lamp (75 w, 220 V, red-infrared) that provides up to 210؇C to the sample. The included OSXRD software allows the diffractometer to be controlled and sequential profiles (ASCII files) to be obtained. These profiles are subsequently processed, obtaining new files: (1) Three-dimensional (cps versus 2 versus time-temperature), (2) peak areas and (3) maximum 2 positions. The automatic temperature control loop, using the proportional-integral-derivative control (PID) method, and the modifications of the XRD chamber are described. Some examples of hydrated minerals were examined in the OSXRD prototype: (1) the epsomite-hexahedrite phase transition in different isothermal analyses (28؇C, 30؇C, 32؇C) and (2) the dehydration of the interfaces of a fibrous aragonite. Three-dimensional plots show the epsomite-hexahedrite phase transition in detail. However, in the case of aragonite (no phase transition) the 3D plot does not show visible changes, but the graph of peak-areas distribution versus temperature increases in sinusoidal shape, suggesting steps during the dehydration processes.ABSTRACT: A commercial engraving tool can be used to carefully disaggregate and vibrate matrix and cement away from stones in semiconsolidated diamictite core. Stone fabrics and planar structures in the core can be measured using a transparent protractor placed over a parallel-lined transparent template that is aligned with an arbitrary North line on the core to determine trends and strikes. Plunges and dips can be read using the dip needle of a geologic compass. These data, combined with stone surface features, shape, and provenance, allow interpretation of sediment genesis and processes where outcrops are rare or of poor quality.

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This work correlates the submarine volcanic and hydrothermal structures detected through seismic profiles on Deception Island (DI) with geochemical distribution patterns of the volcanic sediments which make up the seafloor of the island. A comparison of subaerial and submarine volcanic events is also carried out and three groups of submerged seismo-depositional units are defined. A model is proposed according to which the highest contents of Fe-Mn-Zn are related to volcanic cones, mounds and vents formed in relation with extensional normal low-angle faults. The As-Ba anomalies, active fumaroles and hot-springs are associated to later tensional faults.

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