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Synopsis Deviations from morphological intermediacy in six first generation hybrids between three hatchery strains of rainbow trout,
raised in a common environment, are reported. Hybrids have higher mean counts of four meristic characters than their maternal
parental strain in a significantly greater number of cases (18 out of 24). Furthermore, eight of eleven hybrid indices are
not intermediate. These results are discussed in reference to several mechanisms and models proposed to account for observed
responses of meristic characters to environmental and genetic influences. 相似文献
2.
Synopsis Threespine stickleback, Gasterosteus aculeatus, are thought to have been introduced into Hasse Lake, Alberta, where they were discovered in 1980. The population has grown in numbers since 1980 and by 1981 was more abundant than the native brook stickleback, Culaea inconstans. This population is the first to be found in the interior plains of North America, and it occurs at a higher elevation than any other Canadian population. The source of this introduced population is unknown. Significant differences among four years were found in several meristic and morphometric characters but no significant trends during 1980–1983 were found. Most characters were well within the range of other populations of the species. 相似文献
3.
Terry D. Beacham 《Environmental Biology of Fishes》1985,14(2-3):97-105
Synopsis The latitudinal, regional, and annual variation in number of vertebrae and number of gill rakers present in sockeye salmon, Oncorhynchus nerka, stocks in North America was examined. Stocks in more northern areas had higher numbers of vertebrae and gill rakers than did those in more southern ones. Significant annual variability in the frequencies of these meristic characters within stocks was observed. When stocks were grouped into three regions (southern, central, and northern), heterogeneity in vertebral and gill raker frequencies was greater among regions than among stocks within the regions. Similarly, heterogeneity was greater among stocks than among sampling years within stocks. Differences in vertebral and gill raker frequencies are only useful for stock identification of sockeye salmon on a broad regional basis. 相似文献
4.
The main objective of this study was to compare the morphological variability of sea lamprey (Petromyzon marinus L.) larvae from the main Portuguese river basins. Samples were collected in rivers Minho, Lima, Cávado, Vouga, Mondego, Tejo
and Guadiana. Specimens were analysed in terms of morphometric (linear body measures) and meristic (number of myomeres) characters
to investigate the hypothesis of population fragmentation between river basins caused by some degree of homing behaviour.
The discriminant analysis showed a morphological segregation of the studied populations based on the characters head, tail
and branchial length. The discriminatory power of the meristic characters was comparatively weaker, with the number of trunk
myomeres, and to some extent the head myomeres, being responsible for the reduced separation between groups. Both analyses
were consistent in identifying the cephalic region as the most important morphological feature to discriminate populations
of sea lamprey larvae in the Portuguese territory. The largest cephalic region of the ammocoetes sampled in the northern river
basins may be responsible for a better feeding efficiency and, consequently, higher values of condition factor.
Guest editors: S. Dufour, E. Prévost, E. Rochard & P. Williot
Fish and diadromy in Europe (ecology, management, conservation) 相似文献
5.
Jonathan J. Goin Thomas H. Williams Christopher J. Donohoe 《Environmental Biology of Fishes》2008,82(3):207-213
Vertebral counts in fishes are set early in development by a complex interaction of genetic and environmental factors. Recently,
R. M. McDowall showed that vertebral counts can differ between diadromous and non-diadromous galaxiids, and suggested similar
life history-based variation might also occur in the closely related Salmonidae. We examined variation in vertebral counts
of juvenile rainbow trout, Oncorhynchus mykiss, from within a single large basin where anadromous and non-anadromous forms co-occur. Juveniles were collected at 29 sites
within the Klamath River basin using a nested sampling design. Mean vertebral counts varied among regions, among complexes
within regions, and among sites within complexes. Regression showed that mean vertebral counts decreased with increasing distance
from the ocean. This decrease could not be explained by differences in temperature within the basin during early development.
However, the decrease is consistent with the expectation that non-anadromous forms have fewer vertebrae and are more common
at sites distant from the ocean, and suggests that further study of the relationship between vertebral counts and life history
form in O. mykiss is warranted.
相似文献
Thomas H. WilliamsEmail: |
6.
C. Boglione C. Costa M. Giganti M. Cecchetti P. Di Dato M. Scardi S. Cataudella 《Ecological Indicators》2006,6(4):712-732
7.
Synopsis Geographical variation of three meristic characters, the number of pored scales in lateral line (LL), the number of branchial spines on the first gill arch (SPBR) and the number of transverse scale rows (SQU), were studied in the cyprinid fishRhodeus sericeus and their validity for subspecific discrimination was tested. Counts investigated were taken from population samples at 23 localities covering an area of about 68° geographical longitude (2°40 W – 49°30 E and 128°00 E – 143°00 E), and about 15° geographical latitude (37°30 N – 52°00 N). All three characters manifested a distinct clinal variation. LL, SQU and SPBR closely followed the species' essentially longitudinal distribution. The number of segments was also related to latitude, elevation, mean annual air temperature and fish size. Bergmann's rule was fully demonstrated for fishes and at the species level. Local regional differences were found within particular regions, indicating the existence ofsubclines. Variation of truly isolated populations seems to be predictable and dependent on the clines found in adjacent populations. None of the counts investigated, including a key character (number of pored scales in LL), can be used to distinguishamarus fromsericeus. Owing to sufficient evidence that meristic and morphometric characters used to distinguish fish subspecies succumb to the clinal variation controlled by various factors, the concept of subspecies and trinomial nomenclature is inefficient, superfluous and misleading, and should be excluded from taxonomy, nomenclature and ecology. 相似文献
8.
《Zoology (Jena, Germany)》2014,117(1):64-69
Serially homologous systems with high internal differentiation frequently exhibit meristic constraints, although the developmental basis for constraint is unknown. Constraints in the counts of the cervical and lumbosacral vertebral series are unique to mammals, and appeared in the Triassic, early in their history. Concurrent adaptive modifications of the mammalian respiratory and locomotor systems involved a novel source of cells for muscularization of the diaphragm from cervical somites, and the loss of ribs from lumbar vertebrae. Each of these innovations increased the modularity of the somitic mesoderm, and altered somitic and lateral plate mesodermal interactions across the lateral somitic frontier. These developmental innovations are hypothesized here to constrain the anteroposterior transposition of the limbs along the column, and thus also cervical and thoracolumbar count. Meristic constraints are therefore regarded here as the nonadaptive, secondary consequences of adaptive respiratory and locomotor traits. 相似文献
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