摘要:

A ‘rejuvenated’ cell line ofColpoda cuculluswas yielded from an aged culture submitted to a long‐term resting encystment, and was examined ultrastructurally in logarithmic growth phase and reproductive encystment, after recovery of the standard fission rate. In logarithmically growing cells, the macronuclear envelope shows deep invaginations with the appearance of inner ‘cytoplasmic isles’, and the nucleolar units loosely aggregate as in logarithmically growing young cells. On the other hand, new macronuclear features appear in the reproductive cysts, mainly because of the fusion of the nucleolar units. On the whole, the cytoplasm ultrastructure in rejuvenated cells appears not to differ remarkably from that of young cells. This study indicates that rejuvenated cells ofC. cucullusshow some ultrastructural aspects typical of young cells and others which are commonly observed in aged cells, and are probably derived from the previous senescent condition.

ISSN:1125-0003    

DOI:10.1080/11250009609356114

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The influence of inbreeding was studied in the freshwater planarianDugesia polychroawhich, in addition to reproduce by copulation, is able to form self‐pairs following experimentally induced regeneration. A comparative analysis of the degree of fertility of cocoons laid by cross‐pairs and self‐pairs, showed that cocoons from the latter contain remarkably fewer juveniles which, in addition, are less viable. These results were considered to reflect a Darwinian effect of inbreeding depression.

ISSN:1125-0003    

DOI:10.1080/11250009609356115

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The annual reproductive cycle of both sexes ofTriturus carnifexfrom the Submediterranean was analysed, as well as complex relationships between fecundity, body size, and age. Highly significant seasonal variations in snout‐vent length‐adjusted gonads, fat bodies, and liver weight were found in both sexes. Variations in cycle due to geographic location and climate were recorded. Newts exhibited extended residence in water and lengthening of breeding period. Body size was significantly correlated with age in males, contrary to females. All organ weights were significantly correlated to body size, except for fat body weight in females. In both sexes, fecundity parameters showed a highly significant effect of season, while the effect of age was insignificant (testes weight and total number of oocytes) or barely significant (ovaries weight).

ISSN:1125-0003    

DOI:10.1080/11250009609356116

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A karyotypic analysis was carried out on the Russian sturgeon using C‐ and Ag‐NOR banding techniques and base specific DNA‐binding fluorochromes. The standard karyotype is 2n = 258±4. Nucleolar organizer regions are localized on each of the telomers of four metacentric chromosomes, and on one telomer of four metacentric, four acrocentric, and one large metacentric. C‐bands are mainly located at the centromeric regions of the acrocentric chromosomes. The biarmed chromosomes exhibit either weak or absent C‐bands, but four metacentrics are completely heterochromatic. By means of double staining with complementary fluorochromes, chromomycin A3and DAPI, a pattern of fluorescent regions is recognizable. Interspersion of the opposite DNA base pairs along the chromosomes is discussed.

ISSN:1125-0003    

DOI:10.1080/11250009609356117

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The process of capsule formation inSquilla mantisinvolves the direct action of granulocytes in the recognition of foreign bodies. Evidence was presented that a relevant role in this recognition is played by a lectin (lect‐I), which is synthesized and secreted by granulocytes after the activation of the immunologic reaction.

ISSN:1125-0003    

DOI:10.1080/11250009609356118

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The organic content of the proteinaceous portion of the skeleton of two Mediterranean gorgonian corals was estimated by means of two different methods: a gravimetric one (combustion and incineration) and by elemental analysis.Paramuricea clavatawas investigated at a granitic shoal at the northern entrance to the Strait of Messina (Tyrrhenian Sea);Lophogorgia ceratophytaat a rocky station located off Tinetto Rock (Ligurian Sea). Both gorgonians were the visually dominant macrobenthic species in their habitat. Twenty colonies per species were collected in 1993, ages were estimated by counting axial annual growth increments, and the total content of the organic matrix of the skeleton was determined. The degree of axis mineralization was found to be different in the two species, suggesting different stiffening strategies to withstand water velocities. Annual weight increment ofP. clavatadue to skeletal organics was estimated in 12.72 g AFDW (ash free dry weight) m‐2, while the total resident amount was 78.93 g AFDW m‐2.L. ceratophytayielded, respectively, 47.84 g AFDW m‐2yr‐1and 268.45 g AFDW m‐2. Gorgonian corals can be thought of as ‘energy storer’ organisms, since only a minor part of the organic matter of the colony (i.e., coenenchymal tissue) is immediately available to consumers, while most of it is sequestered in the axial structures, and becomes available to decomposers only after the death of the colony.

ISSN:1125-0003    

DOI:10.1080/11250009609356119

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Morphology and distribution of various types of sensilla in the postembryonic developmental stages on antennae ofCimex hemipteruswere studied using scanning electron microscopy. Four major types of mechanosensilla and chemosensilla, i.e., serrated grooved bristles, unserrated grooved bristles, smooth walled sensilla with pointed tip, and sensilla basiconica were identified. No sexual dimorphism was observed. The sensillar population of serrated grooved bristles and unserrated grooved bristles increased two and six folds, respectively, while smooth walled sensilla with pointed tip and sensilla basiconica increased 3.5 folds from the first nymphal instar to males and females. A high degree of correlation between number of various types of sensilla and different nymphal instars, males and females were observed. Mechanosensilla were found distributed in all the four segments (scape, pedicel, flagellum 1, and flagellum 2) while smooth walled sensilla with pointed tip and sensilla basiconica were mainly confined to the two flagellar segments.

ISSN:1125-0003    

DOI:10.1080/11250009609356120

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This paper describes a method to obtain isolated photoreceptors by means of enzymatic and mechanical dissociation of the whole retina ofOrconectes limosusand the application of patch‐clamp techniquetothese dissociated ommatidia. Several gigaseals and single‐channel currents were recorded, demonstrating the validity and suitability of the experimental protocol. The data reported provide a new element in the ≪single photoreceptor approach≫ to the study of phototransduction mechanisms in invertebrates. These results add another animal model to the few currently described in literature, in which the application of gigaseal techniques to isolated cells has proved useful in the study of ion channels gating.

ISSN:1125-0003    

DOI:10.1080/11250009609356121

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The striking behaviour of several species ofGonodactylus, ofPseudosquilla ciliataand ofOdontodactylus scyllaruswas studied in unharmed animals and in animals with modified eyes and/or an‐tennal scales and antennae. Modifying sensory inputs increases aggressiveness i.e., striking frequency. Precision of hitting the centre of a target disk increases if the middle bands of the eyes are covered and in one‐eyed animals without antennal scales, and decreases if the sides of the eyes are covered. Habituation occurs if trial intervals are shorter than fifteen minutes. Localization and hitting a target in a critical zone should be automatic according to a previously developed model. According to the experiments reported here an additional, learned identification seems to be necessary for the decision to strike. The capacity for learning is shown by habituation. The possible mechanisms for instantaneous and simultaneous localization and identification of a prey (even by animals missing large parts of the eyes) in parallel, nervous subsystems is discussed.

ISSN:1125-0003    

DOI:10.1080/11250009609356122

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The diet of seven passerine trans‐saharian migrant species was analysed by means of faecal analysis during their spring passage at an Italian stopover site (Sardinia). Here birds co‐occur at high densities in a mostly unknown and unpredictable environment. This allows us to analyse the consistency of the species’ feeding pattern in different weather conditions (Capo Caccia 1990–1991) and sites (S. Pietro 1992). The diets of the seven species are mainly composed of insects, they are consistent over the three study years and they reflect the birds’ foraging behaviour. The pied flycatcher and the redstart (mostly ants), the garden warbler and whitethroat (varied diets includingFormicidae, Coleoptera, Apbidoidea, berries), and the willow and the wood warblers (mostlyApbidoidea)are similar or closely related, and form three species pairs with very similar diets. The spotted flycatcher is similar to the first pair, but with a higher proportion ofDipteraandHymenoptera(nonFormicidae). Since species that are similar or closely related have also a very similar diet composition, this cannot be a means by which they can avoid competition. The existence of competition for food and possible ways to test it are also discussed.

ISSN:1125-0003    

DOI:10.1080/11250009609356123

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor