| 1. |
- Andre, C., et al.
(författare)
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Fertilization efficiency and gamete viability of a sessile, free-spawning bivalve, Cerastoderma edule
- 1995
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Ingår i: Ophelia. - : Informa UK Limited. - 0078-5326. ; 43:3, s. 215-227
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Tidskriftsartikel (refereegranskat)abstract
- The fertilization biology of the free-spawning bivalve Cerastoderma edule was studied in the laboratory. Fertilization success declined drastically with decreasing sperm concentration. Viability of both eggs and sperm decreased with age so that no fertilization took place after 4-8 hours. A dilution model suggests that in the field sperm is rapidly diluted to concentrations that would result in very low fertilization efficiencies. The dilution process thus operates on a much smaller time scale than gamete ageing, indicating that most eggs are fertilized close to spawning males. However, it is also shown that under certain circumstances high concentrations of sperm may accumulate over dense populations of bivalves.
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| 2. |
- Calliari, Danilo, 1969, et al.
(författare)
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Summertime herbivory and egg production by Acartia tonsa at the Montevideo coast Rio de la Plata
- 2004
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Ingår i: Ophelia. - 0078-5326. ; 58:2, s. 115-128
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Tidskriftsartikel (refereegranskat)abstract
- We present the first data on copepod feeding and production in the Rio de la Plata, and discuss their correlation to the physical and biological environment. Sampling was performed at a protected area on the Montevideo coast where temperature, salinity and size fractionated chlorophyll a and phaeopigments were monitored weekly from January through February 2003, plus two additional observations in March and April. Acartia tonsa ingestion was measured by gut fluorescence, and gut evacuation rates, egg production and egg hatching success were estimated using standard methods. Food availability was moderate/high, but quality appeared low as reflected by chlorophyll a:phaeopigment ratios <1. Ingestion correlated with both chl-a and pha, suggesting that A. tonsa fed also on detrital matter. Egg production rates were low (1.4-7.5 eggs female(-1) d(-1)) - except for one exceptional record of ca. 88 eggs female(-1) d(-1) - indicating low productivity rates. Egg hatching success ranged from 30-94% and tended to increase during the study period. Overall results suggest that at the study site A. tonsa fed on both phytoplankton and detritus, and that its production was limited by food quality.
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| 3. |
- Granovitch, A., et al.
(författare)
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Digenetic trematodes in four species of Littorina from the west coast of Sweden
- 2000
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Ingår i: Ophelia. - 0078-5326. ; 53:1, s. 55-65
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Tidskriftsartikel (refereegranskat)abstract
- Four species of Littorina (L. littorea, L. obtusata, L. fabalis and L. saxatilis) from the Swedish west coast were examined fur infections with digenetic trematodes. Four species of the genus Microphallus, Podocyte atomon, Renicola roscovita, Himasthla elongata, Cryptocotyle lingua, and Paramonostomum chabaudi were found, in addition to encysted metacercariae of the two genera Himasthla and Renicola. The prevalence of sporocysts and rediae varied substantially among sampled populations (0-44%), as did the prevalence of metacercarial infections (3-100%), and this variation was due both to different microhabitats and to different host species. In L. saxatilis exposed rocky shore populations had lower prevalence than sheltered boulder shore populations. Within the same shores, L. littorea was the trust species with highest prevalence of digeneans. The general pattern of distribution of the nine trematode species ol er host species was similar to what have been reported from other North Atlantic areas. However, prevalence and intensity differed both at a geographic scale (in comparison with other studies) and at a local scale. The temporal variation over years was less significant.
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| 4. |
- Jackson, C M, et al.
(författare)
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Meiofaunal bivalves in maerl and other substrata; Their diversity and community structure
- 2004
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Ingår i: Ophelia. - Stenstrup : Ophelia Publications. - 0078-5326. ; 58:1, s. 49-60
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Tidskriftsartikel (refereegranskat)abstract
- The abundance and diversity of meiofaunal bivalve species from four substrata (live maerl, dead maerl, gravel and sand) were investigated to assess the effects of habitat heterogeneity. Maerl grounds are unusual coastal habitats derived of non-geniculate coralline algae (Corallmaceae, Rhodophyta) and typically exhibit high benthic biodiversity, including a large number of molluscan species. In total 38 species of bivalves were recorded, with the greatest number found in dead maerl (29). These results were contrary to the findings of other authors who have shown dead maerl grounds to have a poorer fauna than live maerl beds. Significant differences were observed in the community structure of the substrata examined, with assemblages on sand being easily distinguishable from those on other substrata. Mysella bidentata was found to be an important species in dead maerl and gravel. In sand the tellinids Moerella pygmaea and Angulus tenuis were the most discriminatory species observed. Number of species, species richness and species diversity observed in dead maerl were considerably greater than in all other substrata. There were no apparent r- or K-selected species associations with particular substratum types. Differences observed may have been linked to habitat heterogeneity affecting differential survival (e.g. predator-prey interactions) both during settlement and post-settlement phases.
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| 5. |
- Kostylev, Vladimir E., et al.
(författare)
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Microdistribution of the polymorphic snail Littorina saxatilis (Olivi) in a patchy rocky shore habitat
- 1997
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Ingår i: Ophelia. - 0078-5326. ; 47:1, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- Galician populations of the marine snail Littorina saxatilis have two main morphs on exposed rocky shores. The ridged and banded morph inhabits the barnacle (Chthamalus stellatus) dominated upper shore, while the smooth and unbanded morph is mainly found in the lower-shore zone of blue mussels (Mytilus galloprovincialis). The distribution of the two morphs overlaps in the mid shore where hybrids are also present. The mid-shore habitat is a mixture of barnacle and mussel patches. We hypothesised that the different architectural complexity of barnacles and mussels would affect the distribution of the two morphs. Fractal dimensions were used to describe the substratum complexity of 96 small patches from three sites with different proportions of barnacles and mussels. Increased proportions of mussels in a patch increased the fractal dimension, and thus surface complexity. Snail abundance decreased with increased substratum complexity in the smooth and unbanded morph and in the hybrids but not in the ridged and banded morph. Furthermore, snail size increased with surface complexity Barnacles seemed a more suitable habitat than mussels as the interstitial volumes between barnacles available as refuges fbr snails were of a similar size range to that of the snails, while the mussel refuges were considerably larger.
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| 6. |
- Littorin, Bengt, et al.
(författare)
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Vertical patterns in biomass, size structure, growth and recruitment of Mytilus edulis in an Archipelago area in the northern Baltic Sea proper
- 1999
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Ingår i: Ophelia. - 0078-5326. ; 50:2, s. 93-112
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Tidskriftsartikel (refereegranskat)abstract
- Although dwarfed by the low saline conditions, the blue mussel (Mytilus edulis L.) is a biomass dominant in coastal areas of the Baltic Sea proper, owing to the lack of invertebrate predators and competitors for space. In the present study patterns of distribution of blue mussels on relatively smooth, moderately sloping rocky surfaces in the Asko area, northern Baltic proper, are described and interpreted. Biomass, growth rate, maximum shell length and recruitment of mussels decreased with water depths (from 3 to 15 m). No consistent differences in total abundance were, however, detected among depths. Shell growth, as measured by annual growth rings, was linear between about 2-8 yr. of age. Within this linear interval the estimated rate of shell growth was significantly faster (3.4 mm yr.(-1)) at 5 m than at 10 m depth (2.7 mm yr.(-1)) Although the observed vertical patterns in biomass distribution correlated both with recruitment and growth, the year round presence of large numbers of small mussel individuals (less than or equal to 2 mm) at all depths indicates that differences in somatic growth may explain the observed variability in biomass among depths. Potentially important processes such as intraspecific competition, food availability and food quality, which may generate the observed patterns in growth and biomass are discussed.
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| 7. |
- Nygren, A, et al.
(författare)
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Three new species of Proceraea (Polychaeta : Syllidae
- 2001
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Ingår i: Ophelia. - 0078-5326. ; 54:3, s. 177-191
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Tidskriftsartikel (refereegranskat)abstract
- Three new species of Proceraea Ehlers, 1868 are described: P. gigantea sp.n. from California, P. nigropunctata sp.n. from California and Washington, and P. rubroproventriculata sp.n. from Florida and Brazil. Comparisons with all similar taxa are provided and summarized in a table. Proceraea gigantea is characterized by large teeth on the distal part of the chitinous inner proboscis lining (trepan) and by the largest known size in Proceraea, P. nigropunctata by a unique colour pattern, and P. rubroproventriculata by having a trepan with 12 large teeth alternating with 12 smaller teeth, in two separate rings.
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| 8. |
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| 9. |
- Persson, Agneta, 1963
(författare)
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Proliferation of cryptic protists and germination of resting stages from untreated sediment samples with emphasis on dinoflagellates
- 2002
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Ingår i: Ophelia. - 0078-5326. ; 55:3, s. 151-166
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Tidskriftsartikel (refereegranskat)abstract
- Incubation of untreated sediment samples from the northern part of the Swedish west coast resulted in a conspicuous proliferation of various protists. Samples from ten coastal sites were incubated in filtered seawater and the resulting vegetative stages were recorded for a period of two weeks. At least 47 different dinoflagellate taxa were encountered as vegetative stages, more than 46 different ciliate taxa and at least 64 living diatom taxa were present. There were also cyanobacteria, haptophytes, cryptophytes, euglenophytes, prasinophytes, chlorophytes and amoebae. As total 263 taxa were identified from less than 100 cm(3) sediment, suggesting that most microorganisms are ubiquitous, present almost everywhere within their geographic region, but often rare or cryptic. All dinoflagellates present in the area that are known to be cyst-producing were found, corresponding to 25% of the known dinoflagellates at the Swedish west coast. Approximately 26% of the planktonic and 22% of the pennate diatoms recorded at the Swedish west coast were present in the samples.
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| 10. |
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