摘要:

This paper reports the first ultrastructural investigation of bacteriocytes of a member of the genusCryptocercus.The study of thin sections and freeze‐fracture replicas revealed that the symbionts are sequestered intracellularly within a vacuolar system. Aggregates of intra‐membrane particles on the E‐fracture face, close sites of adhesion, and a process of vesiculation have been evidenced on the vacuolar membrane. Moreover, a blebbing process of the symbiont outer membrane is described and the results are compared to those obtained from previously examined cockroaches.

ISSN:0373-4137    

DOI:10.1080/11250009509356070

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The use of specific immunocytochemical techniques to identify prolactin (PRL)‐producing cells allowed us to define more precisely hypophyseal cytology in summer and winter animals and to study its modifications in the ectopic pituitary autograft, namely in a situation in which hypothalamic control is abolished. In the normal adenohypophysis, PRL‐cells are preferentially localized in the an‐teroventral region; in the autograft, these cells are well preserved and a radioimmunoassay (RIA) for amphibian PRL shows that PRL secretion, compared with that of the adenohypophysisin situ, does not vary in winter, while it increases in summer. These results are in agreement with previous data (increase in fin caudal height, a PRL‐dependent character, and in body weight) and demonstrate that, PRL hypophyseal secretion inTriturus camifexcomes under a temperature‐dependent hypothalamic inhibitory control, active only in summer.

ISSN:0373-4137    

DOI:10.1080/11250009509356071

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A survey of the available palaeontological and recent evidence points to the following interim conclusions: (a) animals belonging to the chordate lineage occurred in the Middle Cambrian, when they were already separated in at least three branches; (b) in the Middle Cambrian fossils the notochord may have been not or not entirely differentiated, nor did they have a perfect bilateral symmetry: myomeres, and most probably the nervous system being ≪off symmetry≫ by half a segment between the right and left half of the body, just as they presently are in the Acrania and, incompletely, in the Copelata and Cyclostomata; (c) in one of the Middle Cambrian taxa the skull was represented by skeletal material corresponding to the nonsegmental portions of that of living vertebrates and, as in living cyclostomes, probably derived entirely from neuroectodermal cells from the placodes and neural crest; (d) chordates may have evolved from Vendian animals showing the same type of incomplete bilateral symmetry; (e) the possible affinities of the Cambrian and recent taxa are briefly discussed.

ISSN:0373-4137    

DOI:10.1080/11250009509356072

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Most natural populations of the adder(Vipera berus), including both cryptically coloured (zig‐zag) and melanistic (black) individuals, are polymorphic in dorsal colour pattern. In this study we report experiments to test whether a difference in preference of background colour exists between these morphs. The occurrence of this difference between colour morphs was studied in (1) indoor and outdoor enclosures, (2) basking and not‐basking animals, (3) during daylight and nocturnal hours. Our data show that cryptically coloured and melanistic adders manifest a nearly identical preference in their choice of background colour, both in daylight and nocturnal hours: i.e., a clear‐cut preference for dark substrates independent of sex. Some hypotheses are put forward to explain this preference.

ISSN:0373-4137    

DOI:10.1080/11250009509356073

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A dung‐inhabiting beetle community has been studied at a low‐altitude area of an Italian Alpine valley (Pesio valley) by considering the pattern of beetle succession in droppings and their seasonality. As a whole, the community was characterized by a low density of individuals, with coprophagous beetles largely dominant over carnivorous beetles, both with regard to species richness and abundance. Dung beetles showed the lowest values of species richness and diversity during August a time when predatory beetles peaked. It is possible that during the dry season droppings become a refuge habitat for predatory beetles, as a consequence of moisture and prey availability. With regard to core species (abundance equal to or higher than 20), some intergeneric differences were found.On‐thophagusspecies mainly occurred during May and June, whereasAphodiusspecies were more diversified, with some mainly occurring during May and June, some during September, and others during July. Most Species arrived at the pads during the first two‐four days.Aphodiusspecies, however, were still arriving after five‐six days, whereasOnthophagusspecies virtually stopped arriving after the third day. These differences between Aphodiidae and Scarabaeidae were not enough to produce any effective temporal resource partitioning. In fact, both Principal Component Analysis and a Cluster Analysis showed that only dominant species and some core species were temporally segregated from the others. Most species largely overlapped both in time of arrival at the dropping and in their seasonal distribution. The low population density suggests that intra‐ and interspecific competitive interactions were unlikely to occur in the area during the study period. Also, we doubt that past competition should be invoked to explain the few differences observed. That competition may not be a major organizing factor is also indicated by the similar phenologies of the core dweller species all over Europe.

ISSN:0373-4137    

DOI:10.1080/11250009509356074

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Archilina israelíticasp.n. (Platyhelminthes Proseriata) from the eastern Mediterranean is described. It differs from congeneric species for details of the genital organs. It is the onlyArchilinaspecies known karyologically with n = 4 and the onlyArchilinafrom the Mediterranean occurring intertidally.

ISSN:0373-4137    

DOI:10.1080/11250009509356075

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Twenty‐eight macrodasyid and twenty‐eight chaetonotid species of marine Gastrotricha are reported. Of these species, two ‐Halichaetonotus clavicornisandH. genatus‐ are new, and three are described for the first time for to the Italian fauna. The influence of various physical and chemical environmental factors on gastrotrich distribution along the peninsular and island coasts of the Tyrrhenian Sea are analysed and discussed.

ISSN:0373-4137    

DOI:10.1080/11250009509356076

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The presence ofTroglochaetus beraneckiis reported in the sediments of a small stream in the Lake Tovel area (Trentino, northern Italy). This species is widely distributed in Europe, but was never described in Italy. The relevance of this record from a Zoogeographic point of view is discussed.

ISSN:0373-4137    

DOI:10.1080/11250009509356077

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The distribution ofTalitrus saltator, Talorchestia deshayesiiandTalorchestia ugoliniiin Corsica has been investigated.T. saltatoroccurs on almost all the coasts of Corsica,T. ugoliniionly on the central part of the east coast, whilstT. deshayesiionly on the west. Tests for solar orientation, textural choice, survival in the water, and reproduction rate show a higher ecological valency inT. saltatorthan in the other two species, which could explain its widespread distribution.

ISSN:0373-4137    

DOI:10.1080/11250009509356078

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Investigations were carried out during the summer of 1992 at 32 sampling stations situated on 19 rivers and streams of the River Tiber watershed in Tuscany and Emilia; of these, 31 were located upstream and one downstream from the Montedoglio Dam. Water quality was good and there were no environmental alterations upstream in the sampled streams. The Trichoptera study identified 33 species and 2 subspecies, 7 of which were new records for the area. Taxa abundance was evaluated by grouping into classes the individuals collected by semi‐quantitative sampling. Aquatic stages of Trichoptera, which had a wide range of habitat and trophic categories, were used as indicators of resource distribution along the longitudinal profile of the streams. The results concur with the ≪River Continuum≫ model. Because the reservoir affects the faunistic communities in the downstream reaches of the three immissaries, the Trichoptera population is typical of tracts of higher order water courses.

ISSN:0373-4137    

DOI:10.1080/11250009509356079

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor