A 3-year investigation of sexual reproduction in <Emphasis Type="Italic">Geodia cydonium</Emphasis> (Jameson 1811) (Porifera,Demospongiae) from a semi-enclosed Mediterranean bay |
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Authors: | M Mercurio G Corriero E Gaino |
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Institution: | (1) Dipartimento di Zoologia, Università degli Studi di Bari, Via Orabona, 4, 70125 Bari, Italy;(2) Dipartimento di Biologia Animale ed Ecologia, Università degli Studi di Perugia, Via Elce di Sotto, 06123 Perugia, Italy |
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Abstract: | The reproductive cycle of Geodia cydonium in a semi-enclosed Mediterranean bay (Porto Cesareo, SW Apulia) was studied with monthly frequency over a 3-year period.
The investigation was carried out by utilizing a technique consisting of tagging ten individuals with a PVC stick and cutting
off, by means of a metal cork borer, small samples (cylinders about 5 cm3 in volume) from each of them for histological analysis. Sexual reproductive elements were detected in all individuals, but
in the third year some specimens showed reduced reproductive activity or complete infertility. Spermatogenesis occurred in
a short period (from June to August) whereas oogenesis lasted longer (from spring to late summer). Spermatic cysts occurred
when the frequency of specimens with oocytes reached its maximum values. A relationship between water temperature and the
onset of gamete differentiation was observed. G. cydonium is here confirmed oviparous and gonochoric with a sex ratio in favour of the females. However, in contrast with current literature
on Porifera—which suggests that only a limited number of sponges, all belonging to the same species are sexually active—the
sexual reproduction of this species involves all the examined individuals. This finding can be explained by the methodological
approach used in this research, which differs from the traditional way of assessing the sponge reproductive cycle by analysing
randomly collected specimens within a population. The study of a series of individuals over time represents a better “model
technique” for investigating sponge sexual reproduction and the effect of environmental parameters on gamete differentiation. |
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