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  • 1
    Electronic Resource
    Electronic Resource
    Genetic evidence for cryptic speciation in the marine bryozoan Alcyonidium gelatinosum (1978)
    Springer
    Marine biology 49 (1978), S. 27-32 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The common subtidal marine bryozoan Alcyonidium gelatinosum (L.) is one of the most confusing species of a taxonomically very difficult genus. It shows massive variation for almost all morphological characters. A number of sympatric colonies collected off the coast of Lundy (Bristol Channel) could be clearly divided on morphological grounds into two quite distinct types. Using starch gel electrophoresis the products of a range of genetic enzyme loci were compared between the two morphotypes and also between these and other Bristol Channel populations of A. gelatinosum. Minimal differences were observed between one Lundy morphotype and the other allopatric populations, which it was consequently concluded were conspecific. The second morphotype showed considerable genetic differentiation [genetic identity (Nei, 1972) =0.417] from the other Lundy population, with no common alleles at some loci. The probability of obtaining the observed results by chance in a single population is significantly low (P〈10−14). It is therefore concluded that the two morphotypes of A. gelatinosum from Lundy are not conspecific.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00390727
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  • 2
    Electronic Resource
    Electronic Resource
    Reproductive strategies and life histories in the cheilostome marine bryozoans Chartella papyracea and Bugula flabellata (1982)
    Springer
    Marine biology 71 (1982), S. 241-256 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seasonal life history phenomena were monitored through 1978 for two sublittoral cheilostome bryozoans from souther Britain: Chartella papyracea (Ellis and Solander), a non-placental brooder, and Bugula flabellata (Thompson in Gray), which is placental. The intracolonial relationships between growth by zooid budding, polypide recycling, and sexual reproduction, were analysed for both species — quantitatively in the case of C. papyracea. Although both species grow only in summer, their life histories differ. C. papyracea is more of a K-strategist, producing perennial fronds that release larvae in several successive years, most being liberated in winter months. The reduced need for maximization of the larval productivity rate is reflected in the intracolonial configuration of polypide and sexual recycling. B. flabellata is more of an r-strategist. The larvae are produced by the ephemeral fronds of two successive colony generations each summer. Colonies are dormant in winter. The need to maximize the larval productivity rate in this species is reflected in the polypide/sexual recycling configuration. It is believed that embryonic placentation contributes to the maximization of the larval productivity rate in this and other placental brooders.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397041
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  • 3
    Electronic Resource
    Electronic Resource
    Storage of exogenous sperm by the compound ascidianDiplosoma listerianum (1991)
    Springer
    Marine biology 108 (1991), S. 111-118 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Experimental evidence is presented for the storage of exogenous sperm by zooids of the simultaneously hermaphroditic didemnid ascidianDiplosoma listerianum. Cross-fertilized zygotes can be produced up to 1 mo after a ramet is placed in reproductive isolation. Previously published observations, considered in the light of the present data, suggest that the lumen of the ovary is the site of sperm storage. This is believed to be the first report of post-transmission storage of sperm by an ascidian. Existing records of storage of exogenous sperm in other taxa rarely involve aquatic animals in which spermatozoa are transmitted between mates singly through the surrounding water, as inD. listerianum. The potential significance of sperm storage in the mating systems of sessile aquatic invertebrates is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01313478
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  • 4
    Electronic Resource
    Electronic Resource
    High genetic variability and patchiness in a common Great Barrier Reef zoanthid (Palythoa caesia) (1994)
    Springer
    Marine biology 121 (1994), S. 153-160 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Allozyme electrophoretic analysis of seven polymorphic enzyme loci suggested that 1261 samples of Palythoa collected along 1765 km of the Great Barrier Reef during 1992–1993 were members of a single taxon, identified as Palythoa caesia Dana, 1846, with high external morphological variability and possibly encompassing several previously described species. Populations were slightly genetically differentiated (standardized genetic variance, F ST=0.010, p〈0.05), but there was no evidence of isolation by distance, or of the particular genetic distinction of geographic sets of reefs such as the Swains, as has been observed in other invertebrates. Differentiation was thought to be the result of random selection acting on patches of larvae, not the consequences of long-term reproductive isolation of populations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349484
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  • 5
    Electronic Resource
    Electronic Resource
    Patterns of genetic subdivision in populations of a clonal cnidarian, Zoanthus coppingeri, from the Great Barrier Reef (1995)
    Springer
    Marine biology 122 (1995), S. 665-673 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Samples of an intertidal zoanthid, Zoanthus coppingeri, Haddon and Shackelton, 1891, were collected from three localities in the Great Barrier Reef region during 1992–1993, and subjected to allozyme electrophoretic analysis at seven polymorphic loci. The reduced ratio of observed to expected genotypic diversity indicated that populations were partly clonal, but they were not dominated by a few clones as occurs in some other cnidarians. Regular disturbance by wave action is postulated to prevent the formation of large stands of particular clones by clearing space and mixing genotypes over small scales. The sexual origin of clonal genotypes was confirmed by conformance to Hardy-Weinberg predictions of genotype frequencies at all but one locus. Values of the standardised genetic variance among populations, F ST , were highly significant between localities and between replicate sites within localities separated by only 50 m. Strong genetic structure has not previously been described in a Great Barrier Reef invertebrate species, and is considered to be the consequence of stochastic changes in gene frequencies as a result of low levels of gene flow. High clonal longevity and low recruitment rates may maintain genetic differences over long periods. Similar effects may be seen in other Great Barrier Reef invertebrate species with comparable reproductive patterns.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00350688
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  • 6
    Electronic Resource
    Electronic Resource
    Toxicity and palatability of some British ascidians (1994)
    Springer
    Marine biology 120 (1994), S. 297-303 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Bioassays were conducted to test crude extracts of nine temperate-water ascidians for bioactivity against a range of marine organisms. The extracts generally produced moderate to weak effects, with the exception of those from the ascidian Clavelina lepadiformis, which consistently produced high mortalities against invertebrates. Some of these were then tested in simple palatability assays for feeding-deterrent effects. In general, no strong effects were detected for assays with shore crabs (Carcinus maenas) and fishes (the goby Pomatoschistus minutus and the grey mullet Chelon labrosus). Feeding-deterrent effects were observed with Carcinus maenas for the extracts of Aplidium proliferum, Botryllus schlosseri and Dendrodoa grossularia. It is postulated that these ascidians are unpalatable, but no toxic effects are evident.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349691
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  • 7
    Electronic Resource
    Electronic Resource
    Genetic variation and biochemical systematics in the marine bryozoan Alcyonidium mytili (1978)
    Springer
    Marine biology 49 (1978), S. 343-350 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract For many years the taxonomic position of the marine ctenostome bryozoan Alcyonidium mytili Dalyell (1848) has been in doubt, with some authorities regarding it as being conspecific with A. polyoum (Hassall). We have set out to resolve this problem using enzyme electrophoresis to examine the genetics of the population structure in the two “species”. The results show beyond reasonable doubt that sympatric populations of the two species are indeed from quite separate and non-interbreeding gene pools. An examination of various allopatric populations shows a new species of “A. mytili” to exist sympatrically with the other at Langstone Harbour, Hampshire, England. This species can be readily distinguished on morphological as well as genetic ground. Samples of “A. mytili” from Guernsey also show substantial genetic differences from other populations examined. It is tentatively concluded that this population also represents a separate gene pool and consequently should be recognised as a third species of “A. mytili”.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00455029
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  • 8
    Electronic Resource
    Electronic Resource
    Influence of Filming and of Surface Texture on the Settlement of Marine Organisms (1960)
    [s.l.] : Nature Publishing Group
    Nature 185 (1960), S. 119-119 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] A second assumption frequently made is that marine larvae will attach themselves to a roughened surface more readily than to a smooth one. Both these assumptions are being currently tested on a variety of invertebrate larvae. Small rectangular pieces of chemically inert material are used, the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/185119a0
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  • 9
    Electronic Resource
    Electronic Resource
    Bugula simplex Hincks, a Newly Recognized Polyzoan from British Waters (1958)
    [s.l.] : Nature Publishing Group
    Nature 181 (1958), S. 1146-1147 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Fig. 1. A, Buqula simplex, portion of branch showing hemispherical ovicells and single spines on zocecial angles; Bt B. flabeUaia, distal end of zocBcium showing globular ovicell and two spines on each zooecial angle; 0, avicularium of B. simplex; D, avieularhim from marginal zooecium of B. ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/1811146b0
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of Temperature on the Efficiency of Growth of Plaice Prolarvae (1967)
    [s.l.] : Nature Publishing Group
    Nature 214 (1967), S. 529-530 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The survival of eggs and larvae of the plaice (Pleuranectes platessa L.) in the North and Irish Seas is currently being investigated2. The interpretation of data from surveys at sea to determine the pattern of mortality requires, however, an ability to age the eggs and larvae on the basis of their ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/214529a0
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