摘要:

In the odonate mating system, communication comprises (a) a visual and (b) a tactile stage. Visual communication is confined to male‐male competitive interactions and to courtship display. The stage of tactile communication is initiated by tandem linkage. Following mainly Eberhard's (1985) hypothesis of rapid and divergent evolution of sex‐involved traits, I here develop the idea that communication devices in the odonate mating process are an important target of sexual selection. Implications of sexual selection to these devices are briefly reviewed and their operating as potential reproductive isolating mechanisms is discussed.

ISSN:0373-4137    

DOI:10.1080/11250009309355839

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The fine structure of mature spermatozoon of the strepsipteranHalictophagus chilensisHofmann was studied by light and transmission electron microscopy. The spermatozoon was seen to have an elongated head and a tail with a ≪9 + 9 + 2≫ axoneme and two mitochondrial derivatives. The mono‐layered acrosome is conical in shape and the long nucleus has an internal channel of uncondensed chromatin. The tail is five times longer than the head and the end of the axoneme shows progressive loss of microtubules. These findings are compared with the sperm ultrastructure of other strepsipteran species studied so far.

ISSN:0373-4137    

DOI:10.1080/11250009309355840

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Microanatomy of the anterior median eyes (AME) of a lycosid spider(Lycosa tarentula)shows two classes of photoreceptors in the retina: dorsal and median visual cells (A) are polygonal in cross‐section and bear rhabdomeres on all their faces; ventral visual cells (B), rectangular in section, bear rhabdomeres only on two opposite faces; rhabdomes are aligned in parallel series and successive lines of rhabdoms are oriented orthogonally to each other. Receptor A cells are wider than ? cells, and about twice as numerous. In AME optic nerve, axons are also of two types, large and small, and the optic centre shows thick and narrow fibres, from the second order neurons, being separated by connective and glial cells. Anterior median eyes of second stage juveniles already present the same structure as those of adults. A similar anatomical structure was previously described in the AME of an agelenid spider by Schröer (1974). Since the detection and analysis of polarized light by agelenid and lycosid AME have also been demonstrated, it is suggested that the analysers of the e‐vector of sky‐polarized light are in the receptor ? cells and that the analysis is a successive process using a twisting of the retina due to the action of two muscles.

ISSN:0373-4137    

DOI:10.1080/11250009309355841

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A comparative study of the development ofDirofilaria repensin resistent and susceptible strains ofAedes aegyptiwas performed to acquire more information about the ultrastructural events in the Malpighian tubules and hemocoel of the mosquito, and to investigate the defense mechanisms activated by the host. Larval growth in the primary cells of the Malpighian tubules of the susceptible strain, associated with increasing changes in cytoplasmic organization of the host‐cell leading to cell death, were observed by scanning and transmission electron microscopy. When the parasite reaches the L3 stage and migrates to the hemocoel, hemocytes rarely intervene and seem ineffective. In the resistent strain, it was observed that the destiny ofD. repensis decided in the Malpighian tubules where the intracellular development of penetrating microfilaria is blocked by chemical and/or biochemical defense mechanisms activated by the host.

ISSN:0373-4137    

DOI:10.1080/11250009309355842

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The breeding success of night heron and little egret showed few and non‐systematic variations between two heronries over four years. The most frequent clutch sizes were 3 and 4 eggs, respectively. However, the highest productivity was attained by larger clutches: night heron nests with 4 hatched chicks and 2.6 survivors; little egret nests with 6 chicks and 4.6 survivors. These results confirm a pattern observed in other birds, namely that modal clutch size is lower than the most productive clutch size. Our results are consistent with the hypotheses that the discrepancies between actual and optimal clutch size is due either to a local abundance of food, or to the existence of individual optima.

ISSN:0373-4137    

DOI:10.1080/11250009309355843

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Common terns departed from their breeding colony together and in the same directions. However the low success foragers did not follow the more efficient feeders. This finding contrasts with the hypothesis that colonies may act as information centres in the common tern. We suggest that leaving colonies contemporaneously and in the same direction as a flock may be the results of different ecological pressures such as the predation; moreover clumped departures and arrivals may be related.

ISSN:0373-4137    

DOI:10.1080/11250009309355844

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The form and structure of fish otoliths are species specific. The validity of using otoliths found in pellets to determine the number, size and weight of fish consumed was tested on cormorants. They were fed with fishes of known number, size and weight; pellets were recovered after 24 hours. Sandsmelt(Atherina boyeri),striped mullet(Mugil cephalus),sole(Solea vulgaris)and eel(Anguilla anguilla)were used. It was found that it is possible to estimate the size and weight of prey consumed by birds from size or weight of the otoliths recovered from pellets.

ISSN:0373-4137    

DOI:10.1080/11250009309355845

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0373-4137    

DOI:10.1080/11250009309355846

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Fibroblast heterogeneity within normal tissues and the subsequent modulation in pathological settings are reflected by ultrastructural criteria and expression patterns of cytoskeletal proteins. The temporal or permanent expression of α‐smooth muscle (sm) actin in fibroblastic cells is generally related to the development of structural features typical of myofibroblasts. There is evidence of site specific subtypes of myofibroblasts and even of a histogenetic diversity. While granulation tissues myofibroblasts are derived from local fibroblasts, other cell types may also have the potential to acquire a myofibroblastic phenotype. Myofibroblast phenotype can be modulated by several agents such as cytokines (e.g., GM‐CSF and γ‐interferon) and extracellular matrix components.

ISSN:0373-4137    

DOI:10.1080/11250009309355847

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In freshwater planarians the existence of at least two major actin isoforms has been demonstrated. One isoform is expressed by differentiated muscle cells and is different from vertebrate α‐sarcomeric and α‐smooth actin. The other isoform is recognized by a specific anti warm‐blooded vertebrate α‐smooth muscle actin monoclonal antibody. This latter isoform is expressed mainly in mesenchymal‐like cells ‐ generally called neoblasts ‐ activated during regeneration and growth. To date planaria is the only invertebrate where the existence of an antigen related to α‐smooth muscle actin has been demonstrated. Further studies in this field may be important to define the phylogenetic position of Platyhelminthes.

ISSN:0373-4137    

DOI:10.1080/11250009309355848

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor