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  • 1
    Electronic Resource
    Electronic Resource
    Survival, fecundity and sex ratio of Dinophilus gyrociliatus (Polychaeta: Dinophilidae) under different dietary conditions (1999)
    Springer
    Marine biology 133 (1999), S. 231-236 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050462
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of salinity and two food regimes on survival, fecundity and sex ratio in two groups of Dinophilus gyrociliatus (Polychaeta: Dinophilidae) (2000)
    Springer
    Marine biology 137 (2000), S. 23-29 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of salinity on survival, fecundity and sex ratio were studied in Dinophilus gyrociliatus; a small polychaete with a short lifespan, semicontinuous reproduction and progamic sex determination. The experiment was performed on two groups, originally collected as one sample, from the port of Genoa in November 1995. The specimens were separated into two groups, differing only in their diet: the first was fed with frozen spinach and the other with Tetramin Mikromin. The experiment was performed in 1998 after numerous generations had been maintained under laboratory conditions. The maximum expectation of life at birth varied with salinity level, and both groups showed a better tolerance towards a salinity below 35 psu than above 35 psu. The influence of both salinity and diet on fecundity had statistical significance even though the greatest differences were due to diet; animals fed with Tetramin had a two- or even threefold higher fecundity than those fed with spinach. Diet and salinity also had a statistically significant influence on the sex ratio. These results, as well as all the experimental observations carried out up to date, indicate that in D. gyrociliatus the determination of the sex ratio has a strong phenotypic component.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270000327
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  • 3
    Electronic Resource
    Electronic Resource
    Fecundity and reproductive effort in Ophryotrocha labronica (Polychaeta: Dorvilleidae) (1999)
    Springer
    Marine biology 133 (1999), S. 489-494 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Reproductive effort in terms of fecundity and energy allocation was studied in Ophryotrocha labronica La Greca and Bacci, 1962 a small, semicontinuous iteroparous species. In O. labronica fecundity is more or less constant throughout life, and the total fecundity of the 64 couples examined in this experiment only declined by 12% from the first to the last spawning. No linear relationship was found between fecundity and body size.␣The energy content of germinal and somatic tissues was determined by differential scanning calorimeter. The␣reproductive effort and a reproductive index based on the fifth spawning were evaluated to compare the␣patterns of energy allocation of a semicontinuous iteroparous species with semelparous and annual iteroparous species. The reproductive index ranged from 0.20 to 0.77, with an average of 0.480. The average reproductive effort was 0.840, ranging from 0.60 to 0.96. These figures highlight the enormous amount of energy that O. labronica allocates to reproductive tissues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050488
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of diet on reproductive characteristics of Ophryotrocha labronica (Polychaeta: Dorvilleidae) (1998)
    Springer
    Marine biology 132 (1998), S. 163-170 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Effects of food quality on fecundity (defined as the number of eggs deposited in the entire life of a female), egg size and egg energy content (measured by differential scanning calorimeter were studied in two populations of Ophryotrocha labronica (La Greca and Bacci): one taken from the natural environment immediately prior to the experiment, and the other from the same original environment, but bred for more than 5␣years in the laboratory. Results indicated that fecundity is mediated both by food quality and population origin. Specimens fed Tetramin generally spawned more frequently than those receiving the other two diets, while individuals bred in the laboratory since 1990 spawned more frequently than the wild population. Also the number of eggs per spawning and the total fecundity vary with the quality of the diet; Tetramin gives the highest fecundity values. The differences in egg size and energy content seem essentially related to the population origin, in fact, with all diets laboratory specimens produced larger eggs with higher energy contents than wild specimens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050382
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    Paper (German National Licenses)
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