1,721,070 research outputs found
Ricerche sulla variabilità genetica della "trota marina" (Salmo Trutta L, 1758) dell'Adriatico centrale (Osteychthyes: Salmonidae)
No full textPattern of gonad maturation in a highly stocked population of brown trout (Salmo trutta L, 1758) from Central Italy.
No full textGenome Duplication in Early Vertebrates: Insights from Agnathan Cytogenetics
No full textAgnathans represent a remnant of a primitive offshoot of the
vertebrates, and the long evolutionary separation between
their 2 living groups, namely hagfishes and lampreys, could
explain profound biological differences, also in karyotypes
and genome sizes. Here, cytogenetic studies available on
these vertebrates were summarized and data discussed with
reference to the recently demonstrated monophyly of this
group and to the 2 events of whole genome duplication
(1R and 2R) characterizing the evolution of vertebrates. The
comparison of cytogenetic data and phylogenetic relationships
among agnathans and gnathostomes seems to support
the hypothesis that 1R and 2R occurred before the
evolutionary divergence between jawless and jawed vertebrates
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The role of life-history traits, selective pressure and hydrographic boundaries in shaping the genetic structure of the transparent goby, Aphia minuta
No full textThe transparent goby (Aphia minuta) is a small progenetic goby that displays a short life cycle with early reproductive maturity and represents a valuable fishery resource harvested by artisanal fleets in most part of its distributional range. This study aimed to define the genetic variability in A. minuta at five sampling sites within the Mediterranean Sea and one in the Atlantic Ocean through the analysis of 11 nuclear microsatellite loci. The results revealed that several genetic diversity estimators (expected and observed heterozygosities, mean number of alleles and allelic richness) were lower in the Atlantic Ocean than in the Mediterranean Sea, suggesting the role of past or current demographic events in shaping this pattern. The genetic structure was investigated using both classical genetic differentiation descriptors and Bayesian approaches, and by defining the current and past migration rates. The results obtained revealed a pronounced genetic structure within the Mediterranean Sea and suggest a very low current migration rate. The pattern of historical migration suggests the possible role of hydrographic boundaries in shaping the genetic structure detected in this species. In addition, the identification of loci under selection suggests the possible implication of selective pressures that are acting on genes connected with the peculiar life cycle of this gobiid fish
Role of environmental factors in the spread of domestic trout in Mediterranean streams
No full text1. Overharvesting, habitat alteration and pollution have contributed to the decline of many wild
populations of brown trout in Europe. Since the mid-19th century, stocking with domestic strains
has added a further threat to their genetic integrity. In this study, we adopted a landscape genetic
approach to evaluate the role of environmental factors in promoting or hindering invasion by an
alien genome.
2. Two classes of molecular markers (LDH-C1* locus and mtDNA) were used to evaluate the level of
introgression between native and domestic strains of brown trout in Central Italy. A multivariate
method (redundancy analysis, RDA) was employed to find relationships between genetic diversity
and 19 environmental variables that describe lithology, geomorphology, fish community and human
activities.
3. The RDA indicated that streams with more stable ecological conditions sustain almost pure native
populations, whereas streams characterised by unpredictable hydrological conditions harbour populations
with high levels of introgression or pure for foreign genotypes.
4. Our study revealed that the outcome of supplementary stocking with hatchery-reared brown trout
is strongly linked to the environmental features of different drainage basins
Isolation and characterisation of novel microsatellite loci in the transparent goby Aphia minuta (Perciformes, Gobiidae)
No full textFifteen microsatellite loci were isolated and characterised for the transparent goby (Aphia minuta). These loci were tested on a total of 45 individuals from two geographically distant locations (Ancona and Majorca
Island). The number of alleles ranged from 2 to 34, with expected (He) and observed (Ho) heterozygosities per locus ranging from 0.048 to 0.978 and from 0.048 to 0.958, respectively
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