剪形臂尾轮虫形态的时空变化及其与生态因子间的关系

对芜湖市镜湖和汀棠湖中剪形臂尾轮虫(Brachionus forficula)的发生及其形态特征进行了一年的观察,并分析了其与环境因子间的关系。结果表明,镜湖中,剪形臂尾轮虫出现于7月至10月,且仅存在短后棘刺型个体;2样点内,除了前外棘刺长以外,轮虫的其他各形态参数均随季节显著变化,形态参数的样点间差异也因季节的不同而异;轮虫的各形态参数均随pH的升高而延长,随过滤水体中叶绿素a含量和水体中总叶绿素a含量的升高而缩短;体长和体宽均随晶囊轮虫密度的升高而增大。汀棠湖中,短后棘刺型个体出现于6月至10月,而长后棘刺型个体仅出现于6月至8月;2种形态型个体同时存在时,长后棘刺型个体在种群中所占比例始终高于短后棘刺型个体,并与水温、水体中总叶绿素a含量以及枝角类、桡足类和晶囊轮虫的密度均呈显著的正相关;2样点轮虫短后棘刺型个体各形态参数均随季节显著变化;长后棘刺型个体在1号样点内仅前外棘刺和后棘刺长有显著变化,而2号样点内仅体长、体宽和后棘刺长有显著变化;2样点内长后棘刺型个体的体长、体宽以及前外棘刺和后棘刺均显著长于短后棘刺型个体;同一形态型个体形态参数的样点间差异因季节的不同而异;短后棘刺型个体的前外棘刺和后棘刺长均与水体中总叶绿素a含量呈显著的正相关,后者与过滤水体中叶绿素a含量和枝角类密度也呈显著的正相关;长后棘刺型个体的后棘刺长与桡足类密度呈显著正相关,前内棘刺长与水温、溶氧量和晶囊轮虫密度呈显著负相关。两湖泊内剪形臂尾轮虫的后棘刺长和体长之间均呈显著的正相关,提示其后棘刺的延长并不是对体长的异速增长。     

Morphology and coexistence of congeneric ectoparasite species: reinforcement of reproductive isolation?

Assuming that differences or similarities in morphology among congeneric parasite species living in the same habitat are not a random pattern, several hypotheses explaining morphological differences were tested: (i) reproductive isolation, (ii) niche restriction resulting from competition, and (iii) niche specialization. Congeneric monogenean (platyhelminth) ectoparasites parasitizing the gills of one host species were used as an ecological model. Morphometric distances of the attachment organ and morphometric distances of the copulatory organ between species pairs were calculated, Levin's niche size and Renkonen niche overlap indices were applied. Our results support the prediction that the function of niche segregation is to achieve reproductive isolation of related species in order to prevent hybridization (reinforcement of reproductive barriers). Parasite species living in the same niche differ greatly in the size of copulatory organ. Moreover, species coexistence is facilitated by an increase in morphometric distances of copulatory organ and niche centre distances. Our results also show that species living in overlapping niches have similar attachment organs, which supports the prediction that morphologically similar species have the same ecological requirements within one host and suggests small effects of interspecific competition for the evolution of morphological diversity of attachment organs. Specialist adaptations also seem to facilitate species coexistence and affect the niche distribution within host species. Parasite species that can colonize more than one host species, i.e. generalists, occupy more distant niches within host species than strictly host-specific parasites. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 76, 125–135.     

Morphometric analysis of B2cAMP-induced reverse transformation in synchronized CHO cells

Summary Synchronized transformed and reverse-transformed (by 10⁻³ M B₂cAMP) CHO-K1 cells, growing adherent to plastic, are characterized by means of geometric and densitometric parameters at the level of both the entire cell and of the nuclei at various time intervals after selective mitotic detachment. Transformed and reverse-transformed cells triple-stained with Feulgen, Napthol Yellow S, and periodic acid-Schiff appeared very similar in terms of integrated optical density (IOD), related to either polysaccharides, protein, or DNA amount. On the other hand, a shift from a polygonal to a spindle-shaped morphology is accompanied by a significant decrease in both form factor and average optical density (AOD) of intact cell and nuclei, which are the most conspicuous measured changes caused by B₂cAMP, in addition to a lengthening of the cell cycle duration. In both control and treated cells, important and parallel cell-cycle-dependent modulations of geometric and densitometric parameters are also observed, for both the cytoplasmic (i.e., cell morphometry) and DNA space (i.e., nuclear morphometry). Specifically, the modulation in nuclear morphometry during G1, S, G2, andM phases confirms previous findings on synchronized HeLa cells. The optical density threshold-dependence of geometric parameters shows that, while becoming fusiform, the cytoplasm of reverse-transformed cells had a particularly low optical density precisely in the polar area. Utilization of such an approach in the development of anobjective morphological classification of all cell lines grown as monolayers “in vitro” is also discussed.     

First record of the brown lanternshark,Etmopterus unicolor, from the waters around New Zealand, and comparison with the southern lanternshark,E. granulosus

Specimens of the brown lanternshark,Etmopterus unicolor, reported here for the first time from the waters around New Zealand, were caught on bottom longlines. This study compares morphometeric and meristic characters of New Zealand and Japanese specimens ofE. unicolor and New Zealand specimens of the southern lanternshark,E. granulosus. E. unicolor andE. granulosus are clearly distinguishable by the height of the first dorsal fin, number of spiral valves, number of vertebrae, and shape of the dermal denticles and teeth.     

Morphometric and phylogenetic analysis of theDaviesia ulicifolia complex (Fabaceae, Mirbelieae)

Daviesia ulicifolia is a widespread species that exhibits complex variation throughout its range. Using ordination and cluster analysis of morphometric characters we resolved ten terminal taxa for phylogenetic analysis. A data set including these and five closely related species was coded for a combination of morphometric and qualitative characters and analysed using parsimony. This revealed thatD. ulicifolia is paraphyletic by inclusion ofD. acicularis, D. arenaria andD. microcarpa. One terminal cluster is more similar to an outgroup species (D. arthropoda) than toD. ulicifolia and should be treated as a new species. Given recent theoretical and empirical studies showing paraphyly to be both expected and observed at species level, we propose that all existing species in this group continue to be recognised taxonomically. We suggest subdividingD. ulicifolia into several subspecies.     

Shape plasticity in response to water velocity in the freshwater blenny Salaria fluviatilis

A non‐random association between an environmental factor and a given trait could be explained by directional selection (genetic determinism) and by phenotypic plasticity (environmental determinism). A previous study showed a significant relationship between morphology and water velocity in Salaria fluviatilis that conformed to functional expectations. The objective of this study was to test whether this relationship could be explained by phenotypic plasticity. Salaria fluviatilis from a Corsican stream were placed in four experimental channels with different water velocities (0, 10, 20 and 30 cm s^?1) to test whether there was a morphological response associated with this environmental factor. After 28 days, fish shape changed in response to water velocity without any significant growth. Fish in higher water velocities exhibited a more slender body shape and longer anal and caudal fins. These results indicate a high degree of morphological plasticity in riverine populations of S. fluviatilis and suggest that the previous relationship between morphology and water velocity observed in the field may largely be due to an environmental determinism.     

Semiautomatic extraction of cortical thickness and diaphyseal curvature from CT scans

The understanding of locomotor patterns, activity schemes, and biological variations has been enhanced by the study of the geometrical properties and cortical bone thickness of the long bones measured using CT scan cross‐sections. With the development of scanning procedures, the internal architecture of the long bones can be explored along the entire diaphysis. Recently, several methods that map cortical thickness along the whole femoral diaphysis have been developed. Precise homology is vital for statistical examination of the data; however, the repeatability of these methods is unknown and some do not account for the curvature of the bones. We have designed a semiautomatic workflow that improves the morphometric analysis of cortical thickness, including robust data acquisition with minimal user interaction and considering the bone curvature. The proposed algorithm also performs automatic landmark refinement and rigid registration on the extracted morphometric maps of the cortical thickness. Because our algorithm automatically reslices the diaphysis into 100 cross‐sections along the medial axis and uses an adaptive thresholding method, it is usable on CT scans that contain soft tissues as well as on bones that have not been oriented specifically prior to scanning. Our approach exhibits considerable robustness to error in user‐supplied landmarks, suppresses distortion caused by the curvature of the bones, and calculates the curvature of the medial axis.     

Cranial morphological variation of Dromiciops gliroides (Microbiotheria) along its geographical distribution in south-central Chile: A three-dimensional analysis

We analyzed the variation in cranial morphology of the marsupial Dromiciops gliroides along its distribution in south-central Chile. We evaluated whether the cranial morphological variation is congruent with the phylogeographic structure previously observed in this species. We built three-dimensional models of 69 crania on which we digitized 30 landmarks. We used standard geometric morphometric methods to extract and analyze the shape and size components of the crania. Our data showed a subtle but consistent cranial size and shape variation along the studied distributional range, suggesting a geographic variation pattern rather than a phylogeographic structuring. Indeed, our multivariate analyses recovered a subtle morphological differentiation between island and mainland populations, contrary to what is suggested by a former phylogeographic study. We detected that either the cranial size variation, as well as the insularity and the latitude could be important factors underlying the cranial shape changes. We suggest that an interplay of historical and contemporary processes could be shaping the morphological pattern observed in this marsupial.