Survival, fecundity and sex ratio of Dinophilus gyrociliatus (Polychaeta: Dinophilidae) under different dietary conditions |
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Authors: | D Prevedelli R Zunarelli Vandini |
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Institution: | (1) Dipartimento di Biologia Animale, Università di Modena, Via Università, 4, I-41100 Modena, Italy, IT |
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Abstract: | The influence of different diets (Tetramin dry fish food, frozen spinach, and Dieterba mixed cereals for babies) on survival,
fecundity and sex ratio was examined in a population of the polychaete Dinophilus gyrociliatus. Specimens were collected in the harbour of Genoa and were studied under controlled laboratory conditions. In D. gyrociliatus sex determination is progamic; a single ovary produces eggs of two sizes, the small eggs develop into dwarf males and the
large ones into females. Sex determination is chromosomal with male heterogamety of the XO/XX type, and therefore a 1:1 population
sex ratio is expected. The results of the experiment revealed that diet significantly influenced survival, fecundity and also
the sex ratio. With all diets the maximum lifespan was about the same, but after 10 weeks of experiments the percentage of
survivors was 9% with Tetramin, 35% with spinach and 39% with cereals. Fecundity was different in relation to diet; females
fed with Tetramin produced the maximum number of eggs. The greater and earlier mortality with the Tetramin diet could be related
to the greater fecundity seen in this group, in that, the greater amount of energy allocated to the production of gametes
may have reduced the percentage of individuals surviving to maximum age. In this species, diet affected not only fecundity
but also the sex ratio; the worms fed with cereals showed a clear displacement of sex ratio towards males.
Received: 10 March 1997 / Accepted: 22 September 1998 |
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