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1.
记述采自云南省石林县陆生贝类1新种,即石林管螺Phaedusa shilinensis sp.nov.,文中对新种形态特征、栖息环境进行了描述,并对其相似种进行了分析和讨论。  相似文献   

2.
Nucella lapillus adults were transplanted from the exposed northCornish coast (Bude) to two sheltered inlets in south Devon(Dart Estuary and Plymouth Sound), sites where the native populationshad ceased breeding as a result of sterilisation by tributyltin(TBT) pollution. The transplants produced progeny, many of whichsurvived to maturity and beyond (6 + years). The shell formof Bude individuals is typical of animals exposed to severewave-action, i.e. of light construction with a large apertureto accommodate a broad foot allowing for strong adhesion. However,in contrast, the shell form of the progeny differed markedlyfrom that of their parents; they had the characters associatedwith development under sheltered conditions and subject to severecrab predation, i.e. a robust structure and small aperture.Statistical analysis of the shell characters of the two generationsindicated highly significant differences. It is concluded theseobservations provide evidence of the remarkable plasticity inthe shell form of N lapillus in that both ‘exposed morph’and ‘sheltered morph’ can be produced by the samegene pool when subject to the actions of the appropriate selectionpressures. (Received 25 September 1992; accepted 14 October 1992)  相似文献   

3.
Shell variation within a single population of Litlorina rudis(Maton), collected near the Biological Station at Trondheim,Norway, was studied. The variation of the shell features studied, which includedthe shape of the basal part of the outer lip, and the relativeheight of the spire, width of the shell and of the aperture,were found to be at least partially related to shell height.Furthermore, the shell shape in the population investigated,besides varying with age, also varies due to shell damage. Nosignificant differences were found between the shapes of theshells of males and females. The shell characteristics of different populations of L. rudisalso vary greatly, one of the causes being differences in theenvironmental conditions. When studying this variation betweendifferent populations, however, it must be emphasized that onlyundamaged shells of individuals of about the same age shouldbe compared, in order to obviate the effects of the variabilitydue to age differences and shell damage within each individualpopulation. *Contribution from Trondhjem Biological Station no. 199 (Received 18 February 1980;  相似文献   

4.
The dorsal integument of nearly all species of Peripatidae—one of the two major subgroups of Onychophora (velvet worms)—typically exhibits 12 plicae (=annuli) per segment. The only exception might occur in Plicatoperipatus jamaicensis, from which 24 putative plicae per segment have been reported. Hence, the number of plicae might have been duplicated in this species. If so, one would expect that the structure of the duplicated plicae would resemble that of all other onychophoran species, and that the structures commonly associated with the plicae, including crater‐shaped papillae and hyaline organs, would also have been duplicated. To clarify whether there was indeed such duplication, we compared the structure of the integument in embryos and adults of Pl. jamaicensis (with the putative number of 24 plicae per segment) and Principapillatus hitoyensis (with the common number of 12 plicae per segment). Our scanning electron microscopic data revealed that embryos of both species have 12 plicae per segment. While this number persists in adults of Pr. hitoyensis, 12 additional rows of papillae (=pseudoplicae) occur in the dorsal integument in adults of Pl. jamaicensis. These pseudoplicae differ from the typical plicae of other onychophorans in that they are not equipped with primary papillae and are situated in furrows between the true plicae, as evidenced by the position of hyaline organs and crater‐shaped papillae. Our data further show that the number of the ventrolateral plicae, crater‐shaped papillae, and hyaline organs is similar in the two species studied. This suggests that the plicae have not been duplicated in the integument of Pl. jamaicensis, but rather that additional pseudoplicae have been inserted between the 12 original plicae. These pseudoplicae might have led to a denser package of dermal papillae in the dorsal integument of Pl. jamaicensis, but the functional significance of this evolutionary change is unknown.  相似文献   

5.
F Wachtler 《Acta anatomica》1979,104(4):451-459
The existence of the plica synovialis infrapatellaris, which has long been known in anatomy, is explained from the point of view of evolution. The development of this formation in the early stages of human life is outlined too. The results of the analysis of 117 knee-joints lead to a classification respecting macroscopical points of view of the observed plicae synoviales infrapatellares. 47 plicae synoviales infrapatellares were examined by histological methods under the headings of material, blood vessels and nerves. Mechanical importance of the plica synovialis infrapatellaris must be denied in considering the results of X-ray examination. What is more, the plica synovialis infrapatellaris does not seem to have any importance for the nutrition of neighbouring areas, neither in pre- nor in postnatal life.  相似文献   

6.
Multivariate statistical methods were employed to examine sexualdimorphism in size and shape of Nucella lapillus collected from 16sheltered sites along coasts of Anglesey and the Lleyn Peninsula, NorthWales, UK. Females were significantly larger than males in overallsize; among 12 relative measures of shell shape, two ratios (shellwidth/shell length and aperture length/shell length) were significantlydifferent between males and females, but these differences usuallydecreased with increasing age (shell length). The observed hypoallometricdimorphism could be a result of selection on increased femalefecundity, which may be positively correlated with shell sizein N. lapillus as in other gastropod species. (Received 22 November 1999; accepted 10 April 2000)  相似文献   

7.
Shell variation in two species of the tropical freshwater snailBellamya from two different habitats, was studied. The variation of the shell features studied, which includedthe shell width, spire height, aperture height and aperturewidth, were found to be related to shell height. Furthermore,significant difference in the shell shape was found not onlybetween the two species but also between males and females ofeach species. (Received 18 August 1983;  相似文献   

8.
Using large samples from six localities in New Zealand, thepopulation structure and longevity of the intertidal brachiopodWahonia inconspicua Sowerby has been established. The populationis one containing two modes. The first year group extends upto 3.0 mm shell length and together with the second year groupconstitutes the first mode of the length distribution histogram.Reproduction commences at approximately 10 mm length or duringthe fourth year and at this stage the second mode is formedby the overlap of year groups of mature animals. In Otago HarbourW. inconspicua was found to live up to eight years and occasionallysurvive for as long as 15 years. Growth is slow and unevenly distributed through life, beingfastest during the first four years and decreasing after reproductioncommences. Two years later, at approximately 15 mm shell lengththere is a further reduction in growth rate, and when the animalreaches 17 mm length it slows yet again and becomes very smallin senescence. However, egg production at this stage is veryhigh being greater than 18,000 per year. The rate and type of growth varies considerably between localities.Rough water conditions cause slower growth and more gibbousform, and phenotypic stunting appears to have occurred.  相似文献   

9.
The new genus Atebbania is described for a new hydrobiid species,A. bernasconii, which lives in groundwaters of southern Morocco.Of the Hydrobiidae genera with known shell and anatomy Moitessieriais the closest to Atebbania. The two share the following characters:shell elongate; teleoconch surface with evident microsculpture;seminal receptacle absent. Atebbania is distinguished from Moitessieriaby: shell ovate; penis with a) apical stylet, b) one lobe bentdownward on left (inner) side and c) penial duct running nearthe right (outer) side; posterior end of foot indented. Atebbaniabernasconii n. sp., lives in a limited area, the Tiznit plainin southern Morocco. Other stygobiont hydrobiids from otherareas of Morocco are currently being studied. None of them appearsto be closely related to A. bernasconii or to the species ofMoitessieria (Received 10 February 1998; accepted 30 April 1998)  相似文献   

10.
We investigated variation in shell size and shape of marinesnail species of the Littorina saxatilis complex (L. saxatilis,L. compressa and L. arcana) using geometric morphometric methods.These morphologically similar periwinkle species that are commonin the European intertidal have presented many problems fordiagnosis based on morphology alone. A discriminant analysisdemonstrated that geometric morphometrics is very efficientfor diagnosing individuals to species among sympatric populations.We successfully diagnosed an average of 96% of the specimens(with 85.7–100% correct diagnosis for specific comparisons).The diagnosis capability of this method is absolute at the populationlevel. This makes the technique potentially useful for the designof manipulative field or laboratory experiments. Moreover, ageometric-morphometric analysis was also accomplished in twosnail ecotypes (H and M) of L. saxatilis from rocky shores ofNE England which are apparently adapted to different degreesof wave exposure. We found that the H (exposed) ecotype hasa relatively rounded shell shape with a bigger aperture, whereasthe M (protected) ecotype has a smaller aperture. (Received 23 March 2006; accepted 25 January 2007)  相似文献   

11.
The sublingual structures of Tarsius, Cebuella and Callithrix are studied microscopically. Tarsius has a well developed but not specialized sublingua. In the platyrrhine monkeys the sublingua is lacking completely, but the frenal lamella (plica sublingualis) is very specialized. From this it is concluded that the sublingual organ of Callicebus is a topographically modified frenal lamella, not a sublingua.  相似文献   

12.
The reproductive cycle and shell microgrowth patterns of thevenerid bivalve Ruditapes philippinarum from Matsukawa-ura,a small inlet facing the Pacific Ocean, northeastern Japan wereexamined. Histological examination of the gonads revealed thatspawning in this species occurred twice in 2005, once betweenlate June and early August and the other between late Septemberand early October. Comparison of the shell microgrowth patternswith the developmental stages of the gonad in each individualrevealed that in spawning individuals (mature and spawning stages),the mean lunar-day growth rates were significantly smaller thanthose in individuals which were not in spawning condition (spent,recovery and growing stages). In non-spawning individuals, themean lunar-day growth rates were positively correlated withseawater temperature up to 20°C. However, in spawning individuals,no correlation was observed between shell growth and seawatertemperatures >16°C. These facts suggest that physiologicalstress during reproduction has a negative influence on shellgrowth and results in spawning breaks. The present study indicatethat spawning breaks can be used to identify the timing of sexualmaturity and to count the number of spawning events occurringper year in extant and fossil bivalves.  相似文献   

13.
Patelloida pygmaea (Dunker) and its closely allied species,P. heroldi (Dunker) and P. conulus (Dunker) have caused nomenclaturalconfusion because of their variable shell morphology and distinctivehabitats. According to current nomenclature, these species ofPatelloida have been synonymized and treated as one specieswith two ecological forms. Patelloida pygmaea lives on the shellof Crassostrea gigas (Ostreidae), P. pygmaea form heroldi occurson intertidal rocks on sheltered shores and P. pygmaea formconulus is found on the shell of Batillaria multiformis (Batillariidae).Their taxonomic relationships and possible species status are,however, unclear. Using two mitochondrial genes (fragments ofCOI and 16S ribosomal RNA; total 1192 sites), we analysed 88specimens of P. pygmaea, P. pygmaea form heroldi and P. pygmaeaform conulus from 37 localities in East Asia. In the resultingmolecular phylogenetic trees, the specimens of Patelloida fallinto four clades with high bootstrap probabilities; these cladescorrespond taxonomically to P. pygmaea, P. conulus, P. heroldiand a fourth previously unrecognized taxon, Patelloida ryukyuensisn. sp., described here. A minimum-spanning network for 29 uniquemitochondrial COI haplotypes obtained from 45 specimens in thesame bay in central Japan form three distinct clusters, consistingof P. pygmaea, P. conulus and P. heroldi, respectively. Thissuggests that reproductive isolation has been established betweeneach group. A detailed examination of radular and shell morphologiesof the four taxa clarifies the morphological distinction betweenthese species. The four species form a rather young clade inthe genus Patelloida that diverged during the Pliocene. Theyprovide an example of habitat segregation in a restricted marineenvironment. (Received 21 December 2004; accepted 11 March 2005)  相似文献   

14.
Differences in shell morphology in the intertidal prosobranchmollusc Calliostoma zizyphinum were studied from a number ofsites within four geographical regions of the British Isleswith varying exposures to wave action and crab predation. Meanvalues of damage scarring were highest in shells sampled fromStrangford Lough, Northern Ireland, and lowest in individualsfrom the Atlantic Coast. Shells collected from the Isle of Manwere smaller than those from either the Atlantic coast of Irelandor Strangford Lough. Shells from Strangford Lough had tallershells (higher aspect ratio) than shells from the County Downand Atlantic Coast and shells from the County Down coast weremore squat (lower aspect ratio) than those from all other areas.Shells from Strangford Lough were significantly thinner thanshells from all other geographical areas. The relationshipsbetween shell damage scarring and shell size and tallness werenot consistent among areas. Shells from Strangford Lough arenotable in showing a steep, positive relationship between shellsize and scarring and a steep, negative relationship betweenscarring and tallness. The unusual shell phenotypes observedin shells from Strangford Lough may be explained by rapid shellgrowth, which would not only allow Calliostoma to attain a sizerefuge from crab predators but also to recover successfullyfrom repeated crab attacks on the shell lip. Such a strategywould result in larger, thinner shells with a high number ofdamage scars. (Received 6 June 2006; accepted 20 December 2006)  相似文献   

15.
The geographic variation of 33 morphological characters of the gall-forming aphid Pemphigus populicaulis is studied for 118 localities east of 100oW longitude. Variation can be partitioned into within-gall, among-gall and among-locality components. Among localities variation ranges from 26 to 54%, being significant for all characters. Variation among galls within localities ranges from 24 to. 56%, that within-galls from 8 to 4796. The design of the study permits computation of character correlation matrices within and among localities. Gall size is correlated with tnorphometric characters only on an interlocality but not on an intralocality basis. Interlocalily correlations are a function of intralocality correlations, confirming earlier predictions. There is little correlation between characters of stem mother and alate morphotypes within localities, whereas among localities such correlation is appreciable. This phenomenon may be caused by aspects ol the environment that vary among localities but remain reasonably constant through the earlv life cycle of the aphid. When subjected to factor analysis both correlation matrices yield four factors. Multiple discriminant analysis of the data set results in five interpretable significant axes. Maps are furnished for characters representing the independent dimensions of variation and for discriminant function scores. The patterns of variation can be shown to be significantly nonrandom by Mantel's test and by spatial autocorrelation analysis. All variables are significantly positively autocorrelated at 200 km, many at 400 km and a few at 600 km; few general statements can be made about significant autocorrelations at higher distances. The positive autocorrelation at relatively short distances may be related to the pool of clones from which the genotypes of any one locality sample are taken. There are three correlogram patterns that can be associated with four clusters of variation patterns of characters. The separate patterns presumably cannot be explained by a single microevolutionary process.  相似文献   

16.
Microbilobata avalanchensis n. gen. and n. sp. from the Lower Silurian (upper Wenlock) carbonate rocks of the lower Delorme Group in the Avalanche Lake area, northwestern Canada, is described here as the earliest known terebratulid brachiopod. These small shells (less than 2 mm long) are subtriangular, anteriorly emarginate, possibly punctate, with both valves being sulcate at their anterior halves, the ventral sulcus bearing one prominent plica, and the dorsal sulcus marked by two plicae. Internally, M. avalanchensis has a centronelliform loop extending for about three fifths of the total shell length. The shells are silicified in carbonate rocks of mid to outer shelf origin. M. avalanchensis is relatively rare, with about 40 specimens so far found from samples collected at 58–60 m above the base of section AV5 in the Avalanche Lake area. Its presence in rocks of Wenlock age extends the earliest known terebratulids back about 16 million years from the oldest previously recorded terebratulids (earliest Devonian age). The small size and simple form of the new species suggest that heterochrony (progenesis) could have played a role in the origin of the Terebratulida. M. avalanchensis serves as a good example of Cope's Rule, indicating that the terebratulids evolved from a very small, unspecialized ancestor. The unusually small size of this taxon also offers one explanation as to why some ancestors or transitional forms of major taxonomic groups are extremely difficult to find in the fossil record.  相似文献   

17.
Bird nestlings may be at risk not only from starvation but alsofrom predators attracted to the nest by parental feeding visits.Hence, parents could trade reduced visitation rates for a lowerpredation risk. Here, through field data and an experiment,we show plasticity in daily patterns of nest visitation in theSiberian jay, Perisoreus infaustus, in response to predatoractivity. In high-risk territories, jay parents avoided goingto the nest at certain times of the day and compensated by allocatingmore feeding effort to periods when predators were less active.Such modifications in provisioning routines allowed parentsin high-risk habitat to significantly lower the risk of providingvisitation cues to visually oriented corvid nest predators.These results indicate that some birds modify their daily nestvisitation patterns as a fourth mechanism to reduce predator-attractingnest visits in addition to the clutch size reduction, maximizationof food load-sizes, and prevention of allofeeding suggestedby Skutch.  相似文献   

18.
Reconstructing the phylogeographic patterns of widely distributedand common freshwater mussel species (Bivalvia: Unionidae) mayprovide insight into unionid evolution and speciation. The Wabashpigtoe, Fusconaia flava, is currently recognized as a single,polytypic species that is widely distributed and common throughoutthe Mississippi River drainage and parts of the Canadian Interior,Great Lakes and Gulf Coast drainages. Sequence analysis of themitochondrial COI gene revealed two divergent (3.43%) clades.Clade A consisted of specimens located throughout the upperand lower Mississippi River drainage and in the Red River (Canada)and Lake Erie drainages and all F. cerina specimens. All haplotypeswithin clade A differed by three (0.55%) or fewer nucleotidesubstitutions from the most widely distributed and abundanthaplotype, F1. Clade B, consisting of specimens located in thefar western portion of the species' range, may comprise an undescribedspecies. There was no evidence of genetic differentiation amongF. flava inhabiting headwater and intermediate-sized river localitiesof the Muskingum River system and large river localities ofthe nearby Ohio River. The divergence among F. flava haplotypescomprising clade A (0.18–1.10%) was similar to the divergencebetween the F. cerina haplotypes and the F. flava haplotypescomprising clade A (0–1.10%). This study illustrates theimportance of accessing genetic diversity across the distributionof a polytypic species. Additional analyses based on a combinationof morphology and genetics are needed to determine the taxonomicstatus of clade B and to strengthen our understanding of therelationship between F. flava and F. cerina. (Received 28 May 2007; accepted 13 August 2007)  相似文献   

19.
Aquatic snails from south western Zimbabwe belonging to theBulinus trunscatus/tropicus complex vary widely in shell formsuggesting that more than one taxon could be present. This possibilitywas investigated by making observations on snail samples from13 populations from the Plumtree area, in respect of allozymevariation (5 polymorphic loci), shell morphology (9 variables),copulatory organ and chromosome number. Comparative data wereobtained from snails from north western Zimbabwe identifieddefinitely as B. tropicus. Analysis of the genetic structurerevealed a high degree of polymorphism (P) ranging from 0.29–0.80among populations from Plumtree and expected heterozygosity(He) from 0.02–0.22. No enzymatic diagnostic loci werefound which could differentiate the different morphs or populationsand discriminant function analysis on the morphological datashowed an overlap of morphs among populations. Snails analyzedfor chromosome number were all diploid (2n = 36). Snails exposedto Schistosoma haematobium mira-cidia were all refractory. Thisinformation supports the view of a single species, B. tropicus,which is differentiated due to migration barriers and whereenvironmental variables might be implicated in the morphometricdivergence. (Received 31 July 1995; accepted 15 January 1998)  相似文献   

20.
A conspicuous accumulation of taste buds occurs in the rostral part of the plica sublingualis ("frenal lamella") of Alouatta and Aotus forming taste areas (area gustatoria) superficially situated in the oral mucous membrane. They are found in close vicinity to the orifices of the sublingual salivary glands, but are lacking in the aboral part of the plica sublingualis. They do not occur in all primate species studied. A taste area does not projects above the surface of the surrounding tissue like a papilla. The taste buds open not in crypts of furrows of the oral mucosa, but directly into the spatium sublinguale of the oral cavity proper. In the anterior part of the cavum oris proprium different kinds and very differentiated qualities of sensoral information are perceived (touch, olfaction, temperature). It is conceivable that the taste areas play an important role in perceiving fresh saliva, together with the other sensorial structures in this part of the mouth. This problem can be solved experimentally and by behavioral studies, In addition to its topographical relation to the tongue, the organon sublinguale of Callicebus is structurally very similar to the plica sublingualis of Aotus and Alouatta. Since a sublingua does not occur in New World monkeys, it can be concluded that this organ represents a plica sublingualis which became adherent to the undersurface of the tongue.  相似文献   

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