排序方式： 共有15条查询结果，搜索用时 15 毫秒
1.
MARCO CASU TIZIANA LAI DARIA SANNA PIERO COSSU MARCO CURINI‐GALLETTI 《Biological journal of the Linnean Society. Linnean Society of London》2009,98(4):907-922
Only a few species belonging to the Proseriata (Platyhelminthes) show a parenchymatic pigmentation, which may aid identification. Among these, Pseudomonocelis agilis has a yellowish body and is provided with a reddish–brown girdle in front of the statocyst. The species is known for limited areas of northern Europe and the Mediterranean. The present study was conducted to assess both the taxonomic status of populations attributed to the species across the unusually wide range for an interstitial flatworm, which lacks an obvious means of dispersal, and the levels of genetic variability within and among populations, by employing an integrative approach that included the analyses, on six populations, of three molecular markers (small subunit ribosomal 18S‐like gene, inter‐simple sequence repeat, allozymes), karyotypes, and 11 morphological characters. Furthermore, crossbreeding experiments were carried out on the Mediterranean populations. The results obtained revealed the existence of four highly divergent genotypic clusters, accompanied by karyological differences, with complete intersterility among the clusters tested. The combination of approaches adopted strongly supports the conclusion that the wide‐ranging European pigmented species P. agilis is actually composed of four species: P. agilis in the Baltic area; Pseudomonocelis cetinae in the Adriatic; and Pseudomonocelis sp. nov. A and Pseudomonocelis sp. nov. B in the western and eastern Mediterranean, respectively. The latter two species are morphologically indistinguishable for the parameters essayed. Reconstruction of the phylogenetic relationships of these taxa, including congeneric and consubfamilial outgroups, showed that pigmentation is a plesiomorphic condition for the genus Pseudomonocelis and that Pseudomonocelis sp. nov. A shares a previously undetected, sister‐group relationship with species of the unpigmented P. ophiocephala complex. The present study thus depicts complex speciation processes in a mesopsammic species, which involves allopatric divergence operating on different scales and ecological shifts, and highlights that the contribution of microturbellarians to marine biodiversity may be seriously underestimated. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98 , 907–922. 相似文献
2.
This review summarizes the biochemistry, mode of action, physiologicfunctions, and clinical usefulness of glucagon, with emphasison its role as a mobilizer of glycogen and fat, when adequateamount of exogenous nutrients are unavailable (starvation, heavyexercise, neonatal state) or cannot be properly utilized (diabetesmellitus). The "anti-insulin" properties of glucagon and thelessons of comparative physiology are reviewed. 相似文献
3.
CARLO RENIERI PIERO CECCARELLI ANNA MARIA GARGIULO JEAN-JACQUES LAUVERGNE GIACOMO MONACELLI 《Pigment cell & melanoma research》1993,6(3):165-170
The biological behavior of the pigmentary phenotypes of four breeds of cattle has been analysed: the black pigmentation of Holstein Friesian; the red pigmentation of Limousin; the dilution in Charolais; and the postnatal disappearance of red pigmentation in Chianina. The analytic techniques included the characterization of melanins by high-performance liquid chromatography, the examination of follicular melanocytes by light microscopy, and the examination of melanosomes by electron microscopy. The black phenotype was very strongly eumelanogenic. The red phenotype in Limousin is polymorphic: individual follicular melanocytes contain both mature eumelanosomes and pheomelanosomes. Charolais and Chianina cattle exhibited a dramatic reduction in melanogenic activity, which was characterized by the almost exclusive presence of prephaoemelanosomes in Charolais and of immature premelanosomes in Chianina. In the dilute Charolais phenotype, the density of distribution of follicular melanocytes also seemed to be reduced. The genes that are responsible for these four phenotypes seem to act on the maturation, differentiation, and density of distribution of the melanosomes. 相似文献
4.
ASTRID PIZZO ANGELA ROGGERO CLAUDIA PALESTRINI PIERO CERVELLA MASSIMILIANO DEL PERO ANTONIO ROLANDO 《Biological journal of the Linnean Society. Linnean Society of London》2006,89(2):197-211
The present study investigated the morphological and genetic differentiation pattern between two sympatric dung beetle sister species, Onthophagus taurus and Onthophagus illyricus . The geometric morphometric approach coupled with the use of molecular markers allowed examination of the nature of interspecific relationships and an outline of the evolutionary and geographical processes that might have led to interspecific differentiation and the present-day partial sympatric and syntopic pattern of distribution. Geometric morphometrics failed to discrimininate the two species on the ground of external morphological traits, but revealed interspecific differences when the shape of the primary sexual traits was taken into account. The use of two different molecular markers (cytochrome oxidase subunit I gene and amplified fragment-length polymorphism) demonstrates that the two species are genetically well differentiated, forming two distinguishable lineages probably diverged during the Pliocene by allopatric speciation. No evidence of past or recent introgression and no support for hybridization were found, suggesting that sympatry was established subsequently, when speciation was accomplished. Both molecular markers and genital shape indicate that phenotypically intermediate individuals, despite their ambiguous appearance, are members of O. illyricus species rather than hybrids. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 197–211. 相似文献
5.
6.
MARCO CASU DARIA SANNA PIERO COSSU TIZIANA LAI PAOLO FRANCALACCI MARCO CURINI‐GALLETTI 《Biological journal of the Linnean Society. Linnean Society of London》2011,103(1):117-135
Monocelis lineata is a complex of cryptic species (three in the Mediterranean and one in the Atlantic) widespread in midlittoral habitats. Throughout the range, populations with or without an ocular pigmented shield are found. We investigated the genetic structure of the North‐East Atlantic populations with the aim of shedding light on their phylogeography and reconstructing possible patterns of recolonization after the Würmian glaciation. Fourteen samples were investigated using cytochrome c oxidase subunit I (COI) and 13 by inter‐simple sequence repeats (ISSRs). COI did not exhibit a clear pattern of decreased genetic diversity along a latitudinal gradient. Populations from Ferrol (Spain), Doolin (Ireland), and Helsingør (Denmark) showed a higher genetic variability, whereas a reduction in the number of haplotypes was found at the northernmost edge of the distribution and in northern Ireland and Scotland. Two genetically differentiated areas (southern Europe and south‐western Ireland versus northern Atlantic) were revealed by ISSR data. The results obtained provided evidence of three refugia (Iberian Peninsula, south‐western Ireland, and North Sea), and the occurrence of secondary contacts that shaped the genetic variability of some of the populations examined. Two different recolonization pathways of north‐western Europe during the post‐Würmian glaciations have been detected. Furthermore, ISSR analysis provided evidence of genetic divergence among populations with and without pigmented eyespot, suggesting the action of ecological differentiation. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103 , 117–135. 相似文献
7.
CLAUDIA JULIANO SALVATORE RUBINO DONATELLA ZICCONI PIERO CAPPUCCINELLI 《The Journal of eukaryotic microbiology》1986,33(1):56-59
ABSTRACT. The flagellated protozoon Trichomonas vaginalis, parasite of the human urogenital tract, possesses a well developed microtubule system organized in highly differentiated structures. We have shown by immunoblotting that monospecific anti-sheep brain tubulin antibodies are able to react with the microtubular tubulin of T. vaginalis. These antibodies were used to study the microtubular system of T. vaginalis both in interphase and mitosis by indirect immunofluorescence. The interphase microtubular pattern, characterized by an axostyle, a pelta, four anterior flagella, and a recurrent flagellum, displayed remarkable changes at the onset of mitosis: the axostyle disappeared, and two pole bodies connected by a short spindle became evident; chromosomal fibers arose while pole-to-pole fibers elongated. The last phases of mitosis were marked by the disappearance of chromosomal fibers, the appearance of two small axostyles, and the depolymerization of the pole-to-pole bundle. At the end of mitosis, the normal interphase microtubule pattern was observed. 相似文献
8.
The organization of the zona pellucida in the lizard Tarentola mauritanica was studied at the transmission electron microscope. Evidence is provided in support of the hypothesis that follicle cells and the oocyte work together to synthesize and release components that give rise to the zona .
The components of the zona consist of fibrils and amorphous electron-dense material, which are first observed in young previtellogenic oocytes. These components seem to be released by coated vesicles that are formed by the Golgi complex in both the oocyte and the follicle cells. The material relased by the coated vesicles forms patches around the microvilli that project from the oocyte and the folds of follicle cells. During the following previtellogenic stages, the patches merge together to form a continuous coat around the oocyte. The coat persists until the end of vitellogenesis. 相似文献
The components of the zona consist of fibrils and amorphous electron-dense material, which are first observed in young previtellogenic oocytes. These components seem to be released by coated vesicles that are formed by the Golgi complex in both the oocyte and the follicle cells. The material relased by the coated vesicles forms patches around the microvilli that project from the oocyte and the folds of follicle cells. During the following previtellogenic stages, the patches merge together to form a continuous coat around the oocyte. The coat persists until the end of vitellogenesis. 相似文献
9.
SILVANA FILOSA PIERO ANDREUCCETTI ELIO PARISI ALBERTO MONROY 《Development, growth & differentiation》1985,27(1):29-34
Detergent treatment of sea urchin eggs at the mid 4-cell stage results in prevention of micromere segregation at the fourth cleavage. In these embryos not only the formation of the primary mesenchyme is suppressed, but synchrony of cell division, which is the rule during the first four cleavage cycles, continues for several cycles after the 16-cell stage while the typical mitotic phase wave that sets in after micromere segregation is abolished.
These results support the hypothesis that micromeres act as coordinators of the mitotic activity of the embryo. 相似文献
These results support the hypothesis that micromeres act as coordinators of the mitotic activity of the embryo. 相似文献
10.