Abstract
Abstract. The reproductive cycles of Microcosmus sabatieri Roule and Halocynthia papillosa (Linnaeus) (Ascidiacea, Pyuridae) were investigated by means of histological observations of the gonads and gonad index measurements on monthly samples from Northeast Spanish coast populations during 1985. Both species are simultaneous hermaphrodites, and the spawning season lasts for two to three months ‐ between September and November ‐ after the period of highest water‐temperatures in the area. The evolution of the gonads during the whole cycle is markedly different in both species. Spawning time is extended towards summer in H. papillosa and towards winter in M. sabatieri.SummaryThe parameters studied in H. papillosa and M. sabatieri indicate a single spawning season per year in the area studied. Both species are simultaneous hermaphrodites, and gamete release occurred after the period of highest seawater temperatures, with a maximum in September‐October for H. papillosa and in October‐November for M. sabatieri. Moreover, the release is noticeably more rapid in H. papillosa.Mean oocyte diameter and gonad index show a good correlation. The values of the latter were almost twice as high in H. papillosa than in M. sabatieri. Since no development of nutritional tissue has been observed in histological sections, this can reasonably be interpreted as a higher investment in gamete production in H. papillosa.Rapid buildup of the gonad, gradual release of gametes, and low gonad indices occur in M. sabatieri, whereas gradual buildup, rapid release, and higher gonad indices are displayed by H. papillosa. This indicates different reproductive behavior in these species, a conclusion which is confirmed by statistical analyses.
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