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  • 1
    Electronic Resource
    Electronic Resource
    Genetic variation in the neritic squid Loligo forbesi (Myopsida: Loliginidae) in the northeast Atlantic Ocean (1995)
    Springer
    Marine biology 122 (1995), S. 79-86 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Horizontal starch gel electrophoresis was employed to investigate levels of genetic differentiation between 13 samples of the neritic squid species Loligo forbesi Steenstrup obtained from throughout the majority of its known geographical range. Six enzyme loci identified in a preliminary study as being polymorphic were screened for variation between samples. No significant differences in allele distribution were detected between any of the samples obtained from the Faroe Bank in the north to Lisbon in the south, suggesting that squid throughout this range in the vicinity of the continental shelf are able to maintain panmixia, and effectively belong to a single population sharing a common gene pool. No clinal variation in allele distribution was detected throughout this range, a result which complements the findings of a detailed morphological companion study of the same individuals. Comparison of this homogenous European continental shelf population with squid from the Azores revealed highly significant (P〈0.01) differences in allele distribution at five of the six polymorphic enzyme loci studied. A genetic identity value (I) equivalent to 0.93 over 33 loci was obtained. Analysis of F-statistics suggested migration rates between sites to be as low as one individual per five generations, a rate deemed insufficient under most models to prevent divergence by random genetic drift. The large distance and oceanic depths separating the Azores from continental Europe seem to present an effective barrier to gene flow to L. forbesi, a squid belonging to a family considered to be confined in distribution to relatively shallow, near coastal waters. The two populations of squid in the Azores and along the European continental shelf currently both ascribed to L. forbesi should therefore probably best be regarded as relative subspecies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349280
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  • 2
    Electronic Resource
    Electronic Resource
    Biochemical genetic evidence supporting the taxonomic separation ofLoligo edulis andLoligo chinensis (Cephalopoda: Teuthoidea) from the genusLoligo (1996)
    Springer
    Marine biology 127 (1996), S. 97-104 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Confusion abounds regarding the relative generic status of many member species of the squid family Loliginidae. A taxonomie reorganisation within the family has been proposed in whichLoligo species from the Indo-Pacific possessing photophores on the ink sac, includingLogligo edulis andLoligo chinensis, are removed to the newly created genusPhotololigo. This system of classification has not however gained general acceptance, and some authors have continued to refer to these species asLoligo. Here biochemical genetic data gathered using allozyme electrophoresis are presented supporting the assertion thatL. edulis andL. chinensis should indeed be positioned in a genus distinct from that characterised by the type speciesLoligo vulgaris vulgaris. Cluster analysis of allele frequency data from 22 putative enzyme-coding loci suggests thatL. edulis andL. chinensis are as genetically distant fromL. vulgaris vulgaris as are members of the confamilial generaAlloteuthis, Uroteuthis andSepioteuthis, and as such warrant separate generic status. We conclude that the genusPhotololigo is valid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00993649
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  • 3
    Electronic Resource
    Electronic Resource
    Restricted gene flow and evolutionary divergence between geographically separated populations of the Antarctic octopus Pareledone turqueti (1997)
    Springer
    Marine biology 129 (1997), S. 97-102 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Samples of the Antarctic octopus Pareledone turqueti were taken from three locations on the Scotia Ridge in the Southern Ocean. The genetic homogeneity of these populations was investigated using isozyme electrophoresis. Whilst panmixia appeared to be maintained around South Georgia (F ST = 0) gene flow between this island and Shag Rocks, an island only 150 km away but separated by great depths, was extremely limited (F ST = 0.74). These results are examined with respect to the discontinuous distribution of P. turqueti throughout Antarctica. An estimate of effective population size was also calculated (N e = 3600).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050150
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  • 4
    Electronic Resource
    Electronic Resource
    Genetic evidence for the occurrence of a cryptic species with the littoral nemerteans Lineus ruber and L. viridis (Nemertea: Anopla) (1995)
    Springer
    Marine biology 122 (1995), S. 305-316 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lineus ruber and L. viridis are common intertidal heteronemerteans found on the coasts of northern Europe and the east coast of North America. The two species resemble each other morphologically and were synonymised for many years prior to being separated on the basis of larval development. In this study, specimens of L. ruber and L. viridis were collected from sites along the west and southwest coast of Britain, northern France and the east coast of North America. The external morphology and allele frequencies of isozymes of the two species were compared from all sites. The external morphology of L. ruber and L. viridis was similar but they could generally be separated by colour. Allele frequencies for up to 13 enzyme loci between sympatric populations of L. ruber and L. viridis indicated that these two species are genetically very different (Nei's genetic identity=0.090 to 0.083). Allele-frequency data also indicated the presence of a third genetic type occurring sympatrically with populations of both L. ruber and L. viridis on the coasts of Britain and France but not on the coast of North America. Fixed differences in allele frequencies between populations of the third genetic type and sympatric populations of L. ruber and L. viridis were observed across multiple loci. Genetic identity between the third genetic type and sympatric populations of L. ruber and L. viridis were extremely low (Nei's genetic identity =〈0.078). Such large genetic differences between populations indicate a barrier to gene flow and reproductive isolation. The aberrant type, which exhibits sufficient morphological variation to prevent individuals being distinguished from those of both L. ruber and L. viridis, therefore represents a separate species. The low genetic identities found in intrageneric comparisons of species found in this study have been found in other studies on nemerteans. They may indicate systematic problems within these groups or other phenomena such as morphological stasis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00348944
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  • 5
    Electronic Resource
    Electronic Resource
    Extensive genetic divergence between populations of the common intertidal sea anemone Actinia equina from Britain, the Mediterranean and the Cape Verde Islands (1997)
    Springer
    Marine biology 129 (1997), S. 425-433 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Samples of apparently similar red morphs of the common beadlet sea anemone Actinia equina (L.) were collected from rocky shores on the Isle of Man (Irish Sea), on the French Mediterranean coast near Marseille and on the Cape Verde Island of Sal (off West Africa). For additional comparison an orange morph and the green A. prasina were also collected from the Isle of Man. Morphological descriptions were made and the samples were compared by nematocyst analysis and enzyme electrophoresis. The three British samples showed little genetic divergence (I〉0.90) but the Mediterranean sample was hugely divergent (I〈0.20) from the British ones. The Cape Verde Island anemones were also very different (I〈0.60) from all other samples. It is concluded that the red morph samples from the Cape Verde Islands, the Mediterranean and the Isle of Man belong to three different species. For the new species from the Mediterranean and Cape Verde Islands formal descriptions are given, and the names Actinia schmidti sp.n. and Actinia sali sp.n. are proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050183
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  • 6
    Electronic Resource
    Electronic Resource
    Population differentiation and taxonomic status of the exploited limpet Patella candei in the Macaronesian islands (Azores, Madeira, Canaries) (1996)
    Springer
    Marine biology 125 (1996), S. 141-152 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract There has been considerable confusion in the taxonomy of limpets of the North East Atlantic Ocean and Mediterranean Sea, particularly those from the Macaronesian islands. The present study compared populations of the intertidal limpet Patella candei d'Orbigny from the Azores, Madeira and the Canaries with those of P. caerulea Linnaeus and P. depressa Pennant from the European and African continental coasts. No major differences in radular morphology were detected between the three species. However, electrophoretic analysis of 15 enzyme loci gave overall genetic identity (I) values of ∼0.5 between the three species, indicating that they cannot be regarded as conspecific as previously thought, and suggesting that P. candei is endemic to the Macaronesian islands. Comparisons of P. candei within these islands showed that, although populations did not differ with respect to radular morphology and soft-body parts, populations from the Azores were distinct from those in Madeira and the Canaries in shell shape and gene frequencies. Individuals from the Azores had, no average, taller shells and longer radulae, while those in Madeira and the Canaries had a shallow, depressed and stellate shell form. This was interpreted as being due to the wider habitat distribution of the species in the Azores compared to Madeira and the Canaries. Electrophoretic results showed that P. candei from the Azores differed from P. candei in Madeira and the Canaries by almost 40% of the loci investigated (I=0.660), suggesting that the former is a separate endemic species. An I value of 0.969 between populations in Madeira and the Canaries was typical of conspecific populations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00350768
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  • 7
    Electronic Resource
    Electronic Resource
    Daily feeding rhythms in Atlantic salmon II: size-related variation in feeding patterns of post-smolts under constant environmental conditions (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 50 (1997), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Previous studies of feeding rhythms in post-smolt Atlantic salmon Salmo salar have produced variable results. Therefore, the present study was performed to clarify the source of these differences and to examine size-related variation in daily feeding patterns. A small group of hatchery reared post-smolts was kept in an indoor seawater tank under conditions of constant photoperiod and light intensity, and negligible diurnal variation in water temperature. Feeding responses were monitored by video camera throughout the day. The resultant feeding pattern for the population mirrored an earlier study, with the highest levels of feeding activity in the early morning and late evening. Differences between this and other studies may be due to variation in climate, season or life-history stage. Daily feeding patterns were size-dependent. The largest fish fed at a relatively constant level through the day, medium-sized fish fed in a pattern similar to that described above for the population and small fish fed most at first and last light. These differences were due probably to the effect of competitive interactions upon fish of different sizes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1997.tb01358.x
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  • 8
    Electronic Resource
    Electronic Resource
    Behavioural responses of benthic and pelagic Arctic charr to substratum heterogeneity (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 49 (1996), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Responses to environmental heterogeneity were studied in laboratory-reared offspring of two morphs of Arctic charr Salvelinus alpinus from Loch Rannoch, Scotland, one occupying the pelagic zone and feeding predominantly on zooplankton and the other being benthic in habit and feeding mainly on macroinvertebrates. When housed in groups in tanks with a black-and white striped base, benthic charr demonstrated a clear preference for dark areas, whereas pelagic fish positioned themselves at random with respect to substratum colour. In general, pelagic charr were much less aggressive than benthic charr. In pelagic fish, neither spacing nor aggression was affected by the visual heterogeneity of the substrate. In contrast, benthic charr swam closer together and fought more when housed over a uniform as opposed to a non-uniform substratum. The results are discussed in the context of habitat-specific visual requirements and of an interaction between visual complexity and territoriality previously described for Atlantic salmon Salmo salar.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1996.tb00044.x
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  • 9
    Electronic Resource
    Electronic Resource
    Daily feeding rhythms in Atlantic salmon I: feeding and aggression in parr under ambient environmental conditions (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 50 (1997), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Daily feeding patterns of tank-reared Atlantic salmon Salmo salar parr under ambient conditions and their relationship with patterns of aggression were investigated during spring and autumn. A single, early afternoon feeding peak was observed during spring but no consistent pattern emerged from the autumn trial (fish did tend to feed in synchrony, even though the population's feeding pattern varied between days). Aggression was highest at first light during both spring and autumn, reducing thereafter throughout the day. Feeding and aggression were out of phase during spring, with the level of feeding increasing as aggression decreased. It is suggested that the high levels of early morning aggression are associated with re-establishment of the social order that breaks down after a period of darkness; in the spring this may have inhibited feeding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1997.tb01357.x
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  • 10
    Electronic Resource
    Electronic Resource
    Elementary Organic Chemistry? (1908)
    [s.l.] : Nature Publishing Group
    Nature 78 (1908), S. 342-342 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] MAY I be permitted to direct attention to a question asked in a recent examination in organic chemistry for medical students, the syllabus for which states that “the whole subject is to be treated in an elementary manner”? The question was:-" On analysis an acid whose melting point was ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/078342d0
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