Z-chromosome dimorphism in eagle owls

Chromosomal variation within bird species has been rarely studied. Having studied three individuals, I report a difference in the length of Z-chromosomes in one male eagle owl (Bubo bubo) and use C- and R-banding to study the variation between these Z-chromosomes. Absence of non-centromeric heterochromatin in one Z-chromosome is the cause of the difference in length. The presence of two types of Z-chromosome in this eagle owl may reflect hybridization of animals from different subspecies, or might be caused by a spontaneous deletion of C-band positive DNA. © 1992 Wiley-Liss Inc.     

Phylogenetic relationships in theSideritis leucantha group (Lamiaceae)

Six closely related taxa of the sect.Eusideritis of the genusSideritis (S. leucantha, S. pusilla, S. flavovirens, S. granatensis, S. biflora andS. osteoxylla) are analysed to elucidate their phylogenetic relationships and position within the sect.Eusideritis. Meiotic behaviour, karyotype features, size and fertility of pollen grains, DNA amounts and seed protein profiles are reviewed. A polyploid origin of the group (from x = 7) and the further diversification through dysploidy and chromosome repatterning is postulated.S. osteoxylla is apparently of hybrid origin.     

Karyotype variability in successive generations after hybridization between the great sturgeon, Huso huso (L.), and the sterlet, Acipenser ruthenus L.

Effects of particle size, fish size and temperature on the filtration rate of silver carp were determined. When feeding at 20°C on zooplankton and spherical particles (yeast, micronic beads and pollen), 32-g silver carp filter particles larger than 70 urn at a maximum rate of 18.251 h⁻¹. For particles smaller than 70 μm, filtration rates decrease with decreasing particle size until there is no measured filtration for particles smaller than 10 μm. Filtering rates ( FR ) for particles between 10 and 50 μm are described by the equation, FR =−20.8 + 21.7 × log particle diameter. Filtration rates rise as fish size, particle size and temperature increase. Filtration rates per unit biomass, however, fall as fish size increases: FR = 1.54 W^0.713, where FR is the maximum filtration rate in ¹ h ¹ fish ¹ and W is weight of fish in grammes. The results of these trials are consistent with the hypothesis that particle selection by silver carp is a mechanical, passive function of gill raker morphology.     

Chromosomes of the Antarctic amphipod Waldeckia obesa Chevreux

Mitotic and meiotic chromosomes of the Antarctic lysianassoid amphipod Waldeckia obesa are described. The modal chromosome number is n = 25 and 2n = 50. The potential applications of cytogenetical studies in this group are discussed.     

Siberian species of the riihimakiensis-group in the genusChironomus (Diptera,Chironomidae). 1. Karyotypes and morphology

Karyotypes and morphology of three species with close relations toC. riihimakiensis Wülker 1971 are described from material of Tuva and Altai in Siberia. Only one of them could be reared to the male adult and was namedC. tuvanicus n.sp.     

Vergleichende Karyologie der Gräser-SubtribenAristaveninae undAirinae (Poaceae — Aveneae)

The chromosome numbers of nearly all species of the grass subtribesAristaveninae andAirinae from Europe and northern Africa are presented. Among theAristaveninae the genusAristavena has 2n = 14 chromosomes, whereasDeschampsia forms a polyploid series with the basic number x = 13. In the subtribeAirinae the basic number x = 7 predominates.Avenella includes a polyploid series up to dekaploidy, whilst the lowest diploid value so far known in grasses — caused by descending dysploidy — exists in the annual generaAiropsis andPeriballia with 2n = 8.From both subtribes 12 different karyotypes are described and depicted as idiograms. The basic karyotypes ofCorynephorus, Periballia andVahlodea differ from each other by different chromosome length. SAT-chromosomes in theAirinae vary somewhat. Some marker chromosomes eludicate phylogenetic relationships. Amphiplasty appears in various genera and was studied particularly in the amphidiploidAira caryophyllea. Karyological and genomatic trends are considered in relation to evolutionary strategies of annuals and perennials.The nuclear DNA content of some species has been determined cytophotometrically. In subtribeAirinae a positive correlation exists between chromosome volume, pollen diameter, and DNA content. A comparison of the duration of microsporogenesis and microgametogenesis in annual and perennial species with their nuclear DNA content has shown that a primary nucleotypic influence is not recognizable.

     

桤木属7种植物的核型分析

利用改良去壁低渗法对分布于欧美地区的桦木科(Betulaceae)桤木属(Alnus Mill.)7种植物进行染色体数目与核型分析。结果显示:所有材料染色体形态比较一致,多为由中部(m)及近中部(sm)着丝点染色体组成。意大利桤木(A.cordata)为六倍体,体细胞染色体数为2n=6x=42,核型公式为2n=6x=42=36m+6sm;绿桤木(A.viridis)为八倍体,体细胞染色体数为2n=8x=56,核型公式为2n=8x=56=46m+10sm(SAT);薄叶桤木(A.tenuifolia)、灰桤木(A.incana)、欧洲桤木(A.glutinosa)、裂叶桤木(A.sinuata)和红桤木(A.rubra)均为四倍体,体细胞染色体数均为2n=4x=28,其核型公式分别为2n=4x=28=16m(1SAT)+12sm、2n=4x=28=22m+6sm、2n=4x=28=24m+4sm、2n=4x=28=24m+4sm、2n=4x=28=26m+2sm。其中红桤木(A.rubra)的核型属于1B型,其余均为2B型。     

Karyotypes on three species of Chinese mesogastropod snails, Semisulcospira libertina, S. dolichostoma and Viviparus rivularis

Three species of the families Viviparidae and Pleuroceridae, the first intermediate host of paragonimiasis, metagonimiasis and echinostomiasis were studied cytologically. The observed diploid chromosome number was as follows: Semisulcospira libertina 36, S. dolichostoma 34, and Viviparus rivularis 64. The mitotic chromosome complement of S. libertina has nine metacentric pairs and nine submetacentric pairs, and S. dolichostoma has three metacentric pairs and 14 submetacentric pairs of chromosomes. Viviparus rivularis showed two metacentric pairs and 30 submetacentric pairs of chromosomes.