Inés Martínez-Pita

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.

Males and females gonad fatty acids of the sea urchins Paracentrotus lividus and Arbacia lixula (Echinodermata)

The aim of this study was to analyze male and female gonad fatty acids of two sea urchin species, Paracentrotus lividus and Arbacia lixula, from the south coast of Spain. Additionally, we investigated possible differences between two locations. The ovaries of both species showed higher percentages of 14:0, 16:0, 16:1n-7, 18:2n-6, 18:3n-3 and 18:4n-3 than testes and lower levels of 18:0, 22:1n-9, 20:4n-6 and 22:5n-3. In P. lividus but not in A. lixula, the level of 20:5n-3 was higher in testes than in ovaries. These differences between sexes probably indicate different requirements of males and females during gametogenesis although the presence of a large number of gametes in the mature gonad may also have influences on fatty acid composition. Significant differences in gonad fatty acid profiles where also found when individuals of P. lividus collected at a location of the Mediterranean region were compared with specimens collected at the Atlantic coast. The most remarkable changes were the lower levels of 14:0, 18:1n-7, 20:1n-9, 20:4n-6 and 22:4n-6 and the higher values of 20:1n-11, 20:5n-3 and 22:6n-3 found in males and females of the Mediterranean specimens compared to those of the Atlantic coast. These differences probably reflect the differences in potential food sources at each location.

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.

FATTY ACID COMPOSITION AND UTILIZATION IN DEVELOPING EGGS OF SOME MARINE NUDIBRANCHS (MOLLUSCA: GASTROPODA: OPISTOBRANCHIA) FROM SOUTHWEST SPAIN

Abstract The fatty acid composition of whole egg masses was investigated in 4 marine nudibranchs collected from the southwest of Spain: Polycera aurantiomarginata, Polycera quadrilineata, Berghia columbina and Berghia verrucicornis. The four species are carnivorous. All nudibranchs were characterized by high levels of n-3 polyunsaturated fatty acids (n-3 PUFA), mainly eicosapentaenoic acid (20:5n-3), docosapentaenoic acid (22:5n-3) and docosahexaenoic acid (22:6n-3). Other major fatty acids were the saturated palmitic (16:0) and stearic (18:0) acids, the monounsaturated oleic acid (18:1n-9) and the n-6 PUFA arachidonic (20:4n-6) and docosatetraenoic (22:4n-6) acids. Relative high percentages of the plasmalogen derivatives 16:0DMA and 18:0DMA were also detected. Univariate analysis showed that egg fatty acids from P. aurantiomarginata and P. quadrilineata significantly differed from those of B. columbina and B. verrucicornis. Higher levels of saturated fatty acids and 22:6n-3 and lower percentages of 18:0DMA, 22:4n-6 and 22:5n-3 were found in the spawns of both species of Polycera as compared with both of Berghia. Analysis of the bryozoon Bugula neritina and the sea anemone Sagartia troglodites, main preys of Polycera and Berghia respectively, showed that the differences observed in egg fatty acid composition were likely related to diet. Fatty acids of the fully developed embryos from P. aurantiomarginata and B. columbina, sampled immediately prior to hatching, were analyzed to investigate the dynamics of fatty acids during embryogenesis. The long chain PUFA 20:4n-6, 22:4n-6, 20:5n-3 and 22:5n-3 increased or remained stable during embryogenesis in both species whereas palmitoleic acid (16:1n-7) in B. columbina and 16:0, 17:0, 18:0 and 18:1n-9 in P. aurantiomarginata decreased. The major n-3 PUFA, 22:6n-3, marked decreased in B. columbina but remained unchanged in P. aurantiomarginata. These data indicate that fatty acids play different roles during embryogenesis and that in both nudibranchs the embryo requirements are not the same.

The Effect of Diet on Gonadal Development of the Smooth Venus Clam Callista chione (Mollusca: Bivalvia)

ABSTRACT In this study, the influence of food availability on the gonadal development of the smooth clam Callista chione was analyzed for the first time. Callista chione adults were maintained for 60 days under controlled conditions with two different diet rations: a scarce diet (3% of dry weight of algae by meat dry weight per day) and a high diet (6%). The condition index, gonadal stage, and oocyte size were measured throughout the experiment. Maturation of gonad was achieved in both groups. Nevertheless, the condition index and oocyte diameter were significantly less in the scarce-diet group. These low values seem to be related to a loss in reserve tissue, not to the release of gametes. Thus, in food-limited conditions, the animals use the energy to mature instead of grow. Comparisons with animals from the field were made during all the study periods, and differences were found. In fact, these individuals were primarily in the postspawning stage, and the oocyte size was considerably smaller, coinciding with low chlorophyll a levels.