Francisco Javier Herrera García

Gonadal growth and reproduction in the commercial sea urchin Paracentrotus lividus (Lamarck, 1816) (Echinodermata : Echinoidea) from southern Spain

The reproductive state of six populations of the commercial sea urchin P. lividus was investigated. Specimens were sampled monthly from six sites of southern Spain. The development of the gonad during the period of study was measured using histological methods and categorised by four stages for females and two for male specimens. A Gonadosomatic Index was also established. The six populations exhibited similar reproductive patterns, having mature gonads during almost all months while reconstitution and spent were present mainly in autumn. The population from Sancti Petri had the highest Gonadosomatic Index value. Higher food availability may explain this difference.

The Effect of Seasonality on Gonad Fatty Acids of the Sea Urchins Paracentrotus lividus and Arbacia lixula (Echinodermata: Echinoidea)

ABSTRACT The sea urchins Paracentrotus lividus and Arbacia lixula were collected monthly for 1 y in the southern coast of Spain, and their gonad fatty acids were analyzed to evaluate seasonal variations. The gonad fatty acids of A. lixula significantly differed from those of P. lividus, probably because of substantial differences in diet. In both sea urchins, seasonal changes were mainly characterized by the marked decrease of the major polyunsaturated fatty acid 20:5n-3 in summer and early autumn, and the opposite increase of 20:1n-11, 18:1n-9 and the principal nonmethylene-interrupted diene 20:2&Dgr;5,11. Arachidonic acid showed the lowest levels in winter, increasing in April through May, and remaining at relatively high levels until the end of the year. Saturated fatty acids were less affected by seasonality, although they tended to decrease with advancing maturity of the gonad and to increase after spawning. These seasonal changes are discussed in relation to the annual reproductive cycle and to fluctuations in seawater temperature.

Some aspects of the reproductive biology of two Atlantic species of Polycera (Mollusca: Opisthobranchia)

Spawn and the embryonic development of two species of the genus Polycera were studied. Both species, Polycera aurantiomarginata and Polycera quadrilineata, were collected in the intertidal zone of El Portil (Huelva) in south-western Spain. In the laboratory spawn were collected daily. Length and width of the spawn, number of eggs per mm 2 , egg size and capsule size were measured. The egg masses were controlled several times a day to provide a timetable for the main developmental events until hatching. Embryonic growth was measured between some characteristic stages (gastrula, preveliger, primordial velum and veliger prior to hatch). The two species differ in a number of aspects: spawn are longer, eggs and capsules are bigger in P. aurantiomarginata than in P. quadrilineata. The number of eggs per mm 2 , however, is greater in P. quadrilineata than in its congener. Furthermore, spawn of P. quadrilineata are semicircular whereas those of P. aurantiomarginata are spiral and wavy. Both species show planktotrophic development but embryonic development of P. quadrilineata is faster than that of P. aurantiomarginata. The dynamic of embryonic growth is very similar in the two species, although embryos of P. aurantiomarginata are larger at any measured stage than those of P. quadrilineata.

Determination of the magnetic susceptibility and the magentic polarization of weights by means of the susceptometer method

This report summarizes the results of a SIM comparison of magnetic properties by means of the susceptometer method carried out between seven SIM laboratories and BIPM. The travelling standards for the comparison were four weights Class OIML E2 belonging to OAS, with the nominal values of 1 kg (2 uu) and 2 g (2uu) and a special steel disc. The majority of the results from the participants are consistent with each other. This final report shows the degree of equivalence of the participants and their normalized deviations. SIM MASS AND RELATED QUANTITIES WORKING GROUP SIM MWG7

La polémica sobre la ubicación del altar mayor de la Catedral de México y la adopción del tabernáculo -ciprés-exento

Resumen es: La construccion de la catedral de Mexico, en su mayor parte finalizada en 1667, dio lugar a una interesante polemica sobre el espacio idoneo para ubicar ...