ISSN:0373-4137    

DOI:10.1080/11250009309355816

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The rate of food vacuole formation was shown to vary inParamecium primaureliaduring early clonal life; under constant external environmental conditions, remarkable changes occurred in young cells within a few fissions. Studies on different life span clones showed an increased rate, sometimes gradual and constant, and sometimes interrupted by a decrease, followed first by a reduced, then by a constant number of food vacuoles per unit of time. The decrease in food vacuole number, which was not followed by recovery of the food uptake rate, was related to a decline in fission rate. An explanation of the varying rate of food vacuole formation is discussed in terms of a known change in macronuclear DNA content during clonal life. Cells with a high DNA content were supposed to require less food to complete their cell cycle than cells with a low DNA content.

ISSN:0373-4137    

DOI:10.1080/11250009309355803

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Electrophysiological techniques were used to study active ion transport across the skin in larval, pedomorphic and metamorphosed alpine newts (Triturus alpestris apuanus).Data were compared with morphological and histoenzymological studies (alkaline phosphatase ‐ APH ‐) in the skin of the same animals. A short circuit current, which presumably corresponds to active sodium transport, apparently absent in larvae, develops in pedomorphic specimens during the adult epidermis differentiation process and appears to be sensitive to some extent to temperature changes. Flask cells appear early in pedomorphic forms and reveal intense APH activity, a characteristic which is also found in adult animals. Circumstantial evidence correlates APH activity with transport phenomena. These findings support the hypothesis that morphological and physiological differentiation form part of a single process occurring during metamorphosis.

ISSN:0373-4137    

DOI:10.1080/11250009309355804

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The eggs of eleven species belonging to the genusHabroleptoides,namelyH. annae, H. assefae, H. auberti, H. berthelemyi, H. budtzi, H. confusa, H. malickyi, H. nervulosa, H. pauliana, H. thomasiandH. umbratilis,were examined by scanning electron microscopy. Eggs ofH. aubertiare readily distinguished by a large‐mesh reticulation of the chorion formed by ribs which delimit polygonal areas. In the other species, egg chorion is covered by raised ribs running along the major axis of the egg to form longitudinal rows. Ribs are arranged side by side, except inH. annaewhere they are widely separated from each other by a groove. From an ootaxonomic point of view, the ultrastructural organization of the egg chorion suggests that, except forH. auberti,the species ofHabroleptoidesare very closely related. Nevertheless, the wide separation between ribs occurring inH. annaedistinguishes this species from the others in the group characterized by eggs with a uniform covering of ribs. Analysis of the metric data, calculated for all the above mentioned species ofHabroleptoides,showed a correlation between egg length and width. Scatter plots of these parameters yielded separations among species.

ISSN:0373-4137    

DOI:10.1080/11250009309355805

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The morphology and distribution of the cutaneous sense organs ofGambusia affiniswere studied employing usual techniques and an original one. The lateral‐line organs are divided into two groups of mechanoreceptors which differ from each other in size, shape, and skin location, as well as distribution throughout the body. The taste buds are typical, and are present only in the pharyngeal cavity.

ISSN:0373-4137    

DOI:10.1080/11250009309355806

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

An eversible endophallus is present in most groups of bees. Its presence or absence and its morphological variation were studied in 122 species, representing nine families of bees. An eversible endophallus is absent in the sphecoid wasps and other aculeate Hymenoptera, as well as in the bee families Colletidae and Oxaeidae, and part of the subfamily Andreninae of the Andrenidae. It is suggested that the families Colletidae and Oxaeidae may represent early offshoots in bee phylogeny. Extremely complex endophalli occur in some groups of bees: a positive correlation between complex endophalli and polyandrous mating system was found, suggesting that sexual selection may be the evolutionary force shaping endophallic morphology. The function of the endophallus, as well as of other parts of the external genitalia, was studied in specimensin copulaofNomia nevadensisandPerdita albipennis.The study of the mechanics of copulation was extended to other species, showing that the several sclerotized parts of the bee genital capsule function as clasping devices.

ISSN:0373-4137    

DOI:10.1080/11250009309355807

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Some breeding ecology features of a small colour‐ringed Cetti's warbler population was studied for four years in the countryside near Vicenza (northeastern Italy). Dry brambles (54.9%) proved to be by far the most preferred site for nest building. The commonest clutch size was of four eggs, and 94.1% of completed clutches were of three or four eggs. Clutch size decreased throughout the breeding season. About half of the yearly female population was actually double‐brooded. This percentage seemed influenced mainly by the result of the first clutch, Cetti's warbler generally laying only repeat clutches after an unsuccessful first one. One‐year‐old Females had a smaller first clutch size, nestling weight, and number of fledglings than older females. Hatching success was higher in repeat (87.7%) than in first clutches (70.1%), as was breeding success (64.9% vs. 54%). Females laying in early spring increased their fitness in rearing more season‐long offspring than did later females. This reproductive strategy seems especially profitable in years with an unusually high rate of nesting failure. The high breeding success (60% of eggs produced fledglings, or 75% excluding the anomalous 1989 data) is supposed to be related to the recent Cetti's warbler breeding range expansion.

ISSN:0373-4137    

DOI:10.1080/11250009309355808

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Spatial and food resource use, and activity time were studied in syntopical populations of bank voleClethrionomys glareolusand wood mouseApodemus sylvaticusin woodland habitats. In every habitat, the two species selected different microhabitats; the abundance of thin vegetation and size and dispersion of overstorey trees were generally the variables that segregated the microhabitat, but no constant preferences were shown by the two species in every habitat. Time activity rhythms were significantly different, with the bank vole showing a multi‐phase diel activity, while the wood mouse was strictly nocturnal. However, the diets of the two species overlapped almost completely; the wood mouse showed a higher preference for a seed‐formed diet, while the bank vole showed both folivore and granivore feeding habits. The differences in microhabitat selection and activity time rhythms suggested a shifting in resource use due to competition between the two species; the absence of significant differences in diet was thought to be related with the role of primary consumers played by these rodents in the woodland habitats.

ISSN:0373-4137    

DOI:10.1080/11250009309355809

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Some aspects of the biology of a population of the hermit crab,Cestopagurus timidus,collected from aPosidonia oceanicabed off the Ligurian coast, were investigated also in relation to housing gastropod shells. The population studied was composed by specimens with a carapace length not exceeding 3.6 mm and a sex‐ratio close to 1:1. Ovigerous females were present from March to September. The young, small‐sized specimens occupiedBittiumshells, whilst the medium and large‐sized ones preferred shells of other genera, particularlyCantharus.Interspecific and intersexual competitions for the shell were not apparent; it is possible that similar‐sized specimens may fight for the preferred shells. The few ovigerous females observed occupied shells adequate to their size. Among the different shell parameters examined, linear dimensions appeared to be valid and reliable for evaluating the shell suitability for the hermit crab.

ISSN:0373-4137    

DOI:10.1080/11250009309355810

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Experiments were carried out with anosmic Cory's shearwaters to verify whether these birds, which are strictly nocturnal in their activity on land, use olfactory cues to localize individual nest burrows. Both the experimental birds, subjected to intranasal injection of zinc sulphate solution, which produces a reversible impairment of the olfactory mucosae, and unmanipulated controls were captured at their breeding colony on the island of Linosa (Pelagian Islands, Italy). Releases were carried out on the coast nearly 2 km away from the breeding colony. Recoveries at the nests showed that experimentals achieved significantly poorer homing success than controls. The view that the birds were disturbed in a non‐specific way by experimental manipulation is weakened by the fact that injection of the same zinc sulphate solution into the coanae, a method only marginally involving the olfactory receptors, does not influence homing behaviour. Our results indicate that in Cory's shearwaters the search for individual burrows is based on, or at least complemented by, olfactory cues.

ISSN:0373-4137    

DOI:10.1080/11250009309355811

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor