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1.
The revision of the antarctic–subantarctic species Orchomenopsis reducta Schellenberg, 1931, has led to its attribution to a new, highly apomorphic genus: Falklandia gen.n. A new definition of the uristid group is given and Falklandia with 36 other lysianassoid genera are attributed to this supposedly monophyletic group. 相似文献
2.
Antigenic Heterogeneity of Human IgD Immunoglobulins 总被引:3,自引:0,他引:3
SUBCLASSES of the three major classes of human immunoglobulins, IgG, IgA and IgM, are recognized: four of IgG are well defined1,2 and at least two of IgA3–5 and two of IgM6,7 have been demonstrated. This communication presents evidence for the existence of an antigenic heterogeneity in the heavy chains of IgD, which may also be indicative of subclasses within this class of immunoglobulin. 相似文献
3.
Socio-genetic structure of mound-building mice, Mus spicilegus, in autumn and early spring 总被引:1,自引:0,他引:1
CHANTAL POTEAUX NICOLAS BUSQUET PATRICK GOUAT KRISZTIÁN KATONA CLAUDE BAUDOIN 《Biological journal of the Linnean Society. Linnean Society of London》2008,93(4):689-699
Mus spicilegus has become a popular biological model species in the last decade because of the evolutionary interest of its behavioural particularities (the building of mounds, bi-parental care and monogamous mating system). The genetic structure of M. spicilegus populations should reflect those life-history traits. Although many studies have reported on mound-building mouse populations in the field or in a semi-natural enclosure, only one used hyper variable genetic markers to assess parentage and social structure. In the present study conducted in Hungary, we analysed individuals from seven highly populous mounds in autumn with the set of loci used in a previous study. Our results confirmed that mounds are inhabited by juveniles from several parental units, but revealed population differences. In a capture–recapture field session in spring, we assessed genetic relationships between individuals after dispersal from the mounds, the other key moment of the life cycle of this species. The results indicate that the social structure at this moment reflects a transition phase between the large over-wintering groups and the monogamous pairs described later in the year. Social bounds forged during the long winter cohabitation may have lasting effects on social and genetic structure of this species. This scenario is discussed in respect of the available literature on this species as well as other species. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 689–699. 相似文献
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ALEXANDRA HOUSSAYE JEAN‐CLAUDE RAGE NATHALIE BARDET PEGGY VINCENT MBAREK AMAGHZAZ SAID MESLOUH 《Palaeontology》2013,56(3):647-661
Abstract: Palaeophis maghrebianus belongs to the Palaeophiinae (Palaeophiidae). This snake subfamily is relatively poorly known, and it is mainly represented by disarticulated vertebrae and ribs and by a few vertebral segments. Its intracolumnar variability remains also poorly understood. The discovery of new isolated vertebrae and vertebral segments of Palaeophis maghrebianus in the Ypresian (Lower Eocene) Phosphates of Morocco enables us to provide a more detailed diagnosis of this species and to describe its intracolumnar variability. Moreover, the new material reveals that this species could reach gigantic size being, with Palaeophis colossaeus, one of the two longer palaeophiids. The microanatomical and histological analysis of some vertebrae illustrating diverse positions along the vertebral column reveals the presence of osteosclerosis, especially in the anterior and mid‐precloacal regions. The occurrence of this osseous specialization implies a role in buoyancy and body trim control in this taxon, which is considered a shallow marine dweller based on its anatomical features and geological data. Palaeophis maghrebianus also displays a dense vascular network suggesting a growth speed, and thus a metabolic rate, much higher than in the biggest extant snakes. 相似文献
6.
CLAUDE MONNIOT 《Zoological Journal of the Linnean Society》1994,110(1):41-51
New specimens from the Pacific coast of Panama provide the opportunity to redescribe Pyura lignosa Michaelsen, 1908. The status of this species and of three other similar pyurids ( P. vannamei nomen novum, P. cadamostoi sp. nov., and P. shiinoi Tokioka, 1949) is examined, and all four species are identified, described, and compared. 相似文献
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GABRIEL RIVERA JULIEN CLAUDE 《Biological journal of the Linnean Society. Linnean Society of London》2008,94(3):483-489
Although physical features of the environment are known to influence shape, to date, the effects of many environmental conditions on asymmetry remain unexamined. The present study aimed to examine the relationship between asymmetry and the fluid media (air versus water) that an organism inhabits and, subsequently, to use these findings to test a novel hypothesis that fluid environments can impose selective forces acting to constrain asymmetry to maintain or enhance biomechanical function. We examined carapace asymmetry in 114 species (69 aquatic and 45 terrestrial) from the chelonian superfamily Testudinoidea. The results obtained indicate that environment is correlated with the degree of asymmetry, but in different directions for the two clades that comprise the Testudinoidea. Within the Testuguria, aquatic turtles have lower levels of asymmetry than terrestrial turtles, which is consistent with our proposed biomechanical hypothesis. This pattern was not observed within the Emydidae, possibly due to the much shorter time that terrestrial taxa in this clade have existed. Nevertheless, the present study provides the first evidence for a relationship between fluid media and asymmetry in any taxonomic group. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 483–489. 相似文献
9.
Abstract: Directed evolution of life through millions of years, such as increasing adult body size, is one of the most intriguing patterns displayed by fossil lineages. Processes and causes of such evolutionary trends are still poorly understood. Ammonoids (externally shelled marine cephalopods) are well known to have experienced repetitive morphological evolutionary trends of their adult size, shell geometry and ornamentation. This study analyses the evolutionary trends of the family Acrochordiceratidae Arthaber, 1911 from the Early to Middle Triassic (251–228 Ma). Exceptionally large and bed‐rock‐controlled collections of this ammonoid family were obtained from strata of Anisian age (Middle Triassic) in north‐west Nevada and north‐east British Columbia. They enable quantitative and statistical analyses of its morphological evolutionary trends. This study demonstrates that the monophyletic clade Acrochordiceratidae underwent the classical evolute to involute evolutionary trend (i.e. increasing coiling of the shell), an increase in its shell adult size (conch diameter) and an increase in the indentation of its shell suture shape. These evolutionary trends are statistically robust and seem more or less gradual. Furthermore, they are nonrandom with the sustained shift in the mean, the minimum and the maximum of studied shell characters. These results can be classically interpreted as being constrained by the persistence and common selection pressure on this mostly anagenetic lineage characterized by relatively moderate evolutionary rates. Increasing involution of ammonites is traditionally interpreted by increasing adaptation mostly in terms of improved hydrodynamics. However, this trend in ammonoid geometry can also be explained as a case of Cope’s rule (increasing adult body size) instead of functional explanation of coiling, because both shell diameter and shell involution are two possible paths for ammonoids to accommodate size increase. 相似文献
10.
We report a study in which we estimate by means of non-equilibriumprocesses the value of an effective partition coefficient, x,a parameter that we use to take into account the non-ideal behaviourof the electrolyte of the external medium in the cell wall space.This parameter is defined by the ratio of the salt partitioncoefficient to the activity of the non-diffusing charges. Tothat purpose, concentration potential in NaCl, LiCI and CuCl2solutions was measured across an isolated cell wall of Nitellaflexilis at different pH. No significant difference appearedbetween the potential values measured in the presence of NaClor LiCl (pH 5.5, 4.0 and 3.0). At pH 3.0, in CuCl2 solutions,the Nitella wall behaved as an uncharged membrane. Two methodshigh concentrations and least-squares approximation-wereused to calculate from these results the value of the effectivepartition coefficient. Both gave similar values of x At a givenpH, the values of x are independent of the concentration ofthe external medium over a large range of concentration ratios.The activity of the exchange sites was estimated by the experimentallydetermined fraction of absorbed monovalent cations. The ionicconcentrations in the wall space were calculated at pH 5.5 and3.0 by introducing the values of x in the relations which correlatethem to the ionic concentrations in the wall for that givenvalue of the activity of the carboxylate sites. From their values,it appears that the negative fixed charges of the wall werefunctionally shaded by the condensation of a part of the adsorbedmonovalent cations. The activity of the former was, therefore,reduced to a value considerably lower than that estimated bythe cationic exchange capacity during equilibrium processes. Key words: Nitella flexilis (L.) Ag., cell wall, concentration potential, partition coefficient, ion condensation 相似文献