摘要:

Long reciprocal migrations from fresh water to the sea give its specificity to the metamorphosis observed in salmons, eels and lampreys, where the most significant physiological changes concern the hydromineral equilibrium. These events have been more specifically studied in the transition towards a marine environment which accompanies smoltification in salmons, the acquisition of a silver livery in yellow eels and ammocete transformation in lampreys. The osmoregulatory function is modified in various organs including the gills, tegument, kidneys and digestive tract. In particular, the gill chloride cells furnish an important contribution by excreting Na*Cl‐ions into the ambient medium against a concentration gradient. An endocrine control of the hydromineral equilibrium has been demonstrated in salmons and eels. Hormones such as cortisol, thyroid hormones or the growth hormone have a hypoosmoregulatory effect which dilutes the body fluids, essentially by accelerating ion excretion through the gill chloride cells. On the other hand, prolactin has a hyperosmoregulatory effect. During salmon smoltification or yellow eel metamorphosis, these hormones induce a global hypoosmoregulatory effect. Such an effect could preadapt smolts and silver eels to sea water by reducing the deleterious effects of a high ionic strength on the body fluids.

ISSN:0373-4137    

DOI:10.1080/11250009509356058

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Ultrastructural analysis of the regenerating tail epidermis of lizards belonging to the generaLampropholisandAnolishas shown that the apical blastematic and non scaled superficial epidermis (wound epidermis) is made of thin keratinized cells forming mesos and an α‐layers. Lipids and keratin (α, while the presence of the β type is uncertain) are deposited among and into these superficial cells. In more proximal regions, the interscale epidermis is superficially made of mesos and α‐cells and under them spinosus‐like cells containing α keratin are seen. Electronpale cells containing keratoialin‐like granules form a clear layer and under them a new Oberhautchen and β‐layers differentiate down along the forming outer surface of the regenerating scales. Regenerating scales derive from epidermal in‐foldings and their outer surface grows at faster rate than the inner surface. The outer surface produces typical epidermal generations toward the centre of the scale. Oberhautchen, ß, mesos, and α layers are produced like in the shedding cycle of the normal epidermis. Autoradiographical observation after 3H‐thymidine administration have shown that epidermal cells take about six days to migrate from the basal layer to the keratinized superficial layers (β, mesos or α). The inner surface and the hinge region doe not produce any β‐keratin layers but are covered by a mesos‐layer. In this way the regenerated scales are coated by a mesos layer that prevents water loss. The mesos layer covering the inner surface detaches from the Oberhautchen of the outer surface, allowing the emergence of the regenerated scale. In the keratinized scales ofLampropholis, after 30–40 days of tail regeneration, neither lacunar nor clear layers were seen under the differentiating α‐layer of the regenerated outer surface. Therefore, when the wound epidermis is shed, it leaves underneath an incomplete new epidermal outer generation to cover the regenerated tail.

ISSN:0373-4137    

DOI:10.1080/11250009509356059

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The functional organization of both the epidermis and the coelomic lining of the peristomial membrane in the regular sea‐urchinParacentrotus lividusis described and correlated with the extreme deformability of the peristomial membrane and with the ≪mutability≫ of its related dermis. The epidermis consists of a monolayer of columnar supporting cells mixed with ciliated sensory cells, the wide interspaces between these epithelial cells being occupied apically by a variety of cell types and basally by a conspicuous basiepithelial nerve plexus. The coelomic lining is a peripharyngeal coelomic epithelium consisting of apical monociliated peritoneocytes and subapical myocytes, and has an associated basiepithelial nerve plexus. Although the basic morphology of these epithelia is similar to that of corresponding tissues in other echinoderms, they both have significant structural adaptations and display the histological pattern of typical transitional epithelia, which enables them to match the wide range of deformations shown by the peristomial membrane in vivo. Histo‐fluorescence techniques were employed to explore the innervation of the outer epidermis and the inner coelomic lining.

ISSN:0373-4137    

DOI:10.1080/11250009509356060

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The supposed relationship linking alkaline phosphatase (???) activity and selective transepithelial transport processes was investigated in the skin of the crested newt under various experimental conditions of ion transport stimulation and inhibition. The effects of rearing animals in deionized water and of treatment with aldosterone were analysed in the cold (10° C, winter) and warm seasons (22° C, summer); the effect of treatment with prolactin and prolactin plus aldosterone was analysed in the warm season. ??? activity was detected histochemically using Burstone's method, ion transport processes were revealed electrophysiologically by determination of the transepithelial potential difference (PD), short‐circuit current (SCC), and electrical resistance (Rm). ??? activity in keratinocytes markedly increases during the transition from the winter to summer condition. In summer aldosterone significantly increases enzyme activity in keratinocytes compared to controls. In the same condition, prolactin, or prolactin plus aldosterone, dramatically reduces enzyme activity. Modifications of ??? activity in the keratinocytes are closely correlated with corresponding modifications in electrophysiological parameters and appear to be consistent with the hypothesis of an involvment of ??? in ion driving through the skin of the crested newt. Mitochondria‐rich (MR) cells, which energize sodium absorption ≪via≫ principal cells (Harvey, 1992), differ in their pattern of ??? response from the keratinocytes. These results are discussed in the light of current knowledge of the different roles played by keratinocytes and MR cells in the skin of amphibians.

ISSN:0373-4137    

DOI:10.1080/11250009509356061

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

To obtain genetic molecular markers, valuable for the explanation of intraspecific variability, we have sequenced and compared a region of the mitochondrial cytochrome b (Cyt‐b) of seven European eels,Anguilla anguilla(L.), from four different Italian sites. The alignment of the seven sequences shows the existence of 14 variable sites, due to nucleotidic substitutions which are evolutively neutral. Alignment of theA. anguillaCyt‐b sequences with the corresponding sequences fromA. rostrataandA. japonica(both available in the EMBL DNA database) identifies some interspecific differences. A phylogenetic analysis by the neighbour‐joining method clearly confirms the genetic separation and the monophyletic origin of the three species. Six and twenty base substitutions, which are common to all the samples ofA. anguilla, can be diagnostic candidates for the interspecific differences of this species withA. rostrataandA. japónica, respectively.

ISSN:0373-4137    

DOI:10.1080/11250009509356062

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The predatory behaviour on mice by sample of seventeen captive barn owls(Tyto alba)was studied. The owls were divided into two groups according to their age when they entered the Rehabilitation Centre used for this study (either adults/subadults, i.e., with previous predatory experience in the wild, or as fledglings, without any experience of prey catching). The few differences between the behaviour patterns of the age groups suggested that predatory behaviour is mostly under genetic control. While most adult birds caught the mouse, only four young out of eleven studied did so. Both groups showed a decreasing trend in the latency of predation. The young birds were confused or in conflict when facing the prey, and in some cases the owl approached the mouse closely and then returned to the perch to begin a complete predatory sequence again. Three young birds of those that did not hunt were tested six months later. Two of these three young caught a mouse without any evident difficulty. The behaviour displayed by young birds and some patterns indicate that a maturation process is likely influencing the development of the predatory tendency, and do not fully support the hypothesis of the existence of some temporally well‐defined periods.

ISSN:0373-4137    

DOI:10.1080/11250009509356063

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Animal communities, and particularly terrestrial carnivores, are considered to be strongly influenced by competitive interactions among coexisting species. Spiders are ubiquitous and important components of terrestrial ecosystems, but despite their interest, no studies have been published on the community structure and the resource use in the web‐building spiders of southern Europe. We studied species abundance, seasonal occurrence and habitat use by the web‐building spiders of a hedgerow biotope over two years. The spider community was composed of 17 species. Web size and position differed among species and life stages. For most species we observed a higher vegetation density towards the background of the web; this may decrease the ability of insects to see and avoid it. We observed differences among all the spider species in many habitat parameters (horizontal distribution, vertical stratification, density of vegetation around webs), and marked differences in seasonal occurrence. The segregation among species was greater in seasonal occurrence (overlap = 0.18–0.19) than in horizontal distribution (overlap = 0.67) and than in vertical stratification within the vegetation (overlap = 0.64). These differences may help species coexistence.

ISSN:0373-4137    

DOI:10.1080/11250009509356064

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A new species of the stalked genusHalicometes(Porifera, Tethyidae) has been found off the Brazilian coast of Rio Grande do Sul at a depth of 190 m. This is the first finding ofHalicometesfor the South Atlantic.Halicometes minutasp. n., with exotyles on the stalk, is characterized by a thin lacunar cortex, unrecorded for other species of the same genus, and very small body size.

ISSN:0373-4137    

DOI:10.1080/11250009509356065

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The skull and mandible morphometrics of two insular and endemic taxa (C. siculaandC. canariensis) from the Sicilian and Canary archipelagos, both having exactly the same karyotype were analysed by principal component and canonical variate analyses and related multivariate techniques. Information available in the literature was also employed to obtain a better approach to the systematics relationships in this taxon. Specimens ofC. suaveolens, C. leucodon, C. whitakeriandC. russulafrom the Mediterranean, andC. esuaefrom the Pleistocene of Spinagallo (Sicily) were used as references. The results of multivariate analyses of the metric and non‐metric characters of the skull and mandible, coupled with data from the biochemical and cytotaxonomic literature, have provided unanimous results pointing to the marked phenetic similarity of theC. siculaandC. canariensistaxa, that are ascribable to the same monophyletic group. On paleobiogeographic grounds, it is suggested that both taxa are two relict peripheral isolates, so dating today's disjointed distribution back to a colonization of the two archipelagos by a Maghrebi ancestral taxon, related to theC. esuaeform, living in the Middle‐Upper Pleistocene, and today probably extinct. In particular, theC. canariensispopulations are morphologically very close to those of the smaller islands around Sicily (Marettimo, Gozo, Ustica), which have been isolated from Sicily for a long time; this could be explained by the similar adaptive responses on the islands and be caused by the Centrifugal Speciation Model. These findings are considered sufficient to guarantee con‐specificity betweenC. siculaandC. canariensisand to place the latter taxonomically as a subspecies ofC. sicula.A recent typological classification ofC. siculais also discussed and refuted.

ISSN:0373-4137    

DOI:10.1080/11250009509356066

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

During the period 1989–1994, soil samples were collected at 51 localities in six different regions of Italy. Twelve genera and 61 species could be distinguished. One genus (Oconnorellagen. n.) and 12 species (Mesenchytraeus straminicolussp. n.,Cernosvitoviella omodeoisp. n.,Achaeta etruscasp. n.,Fridericia globuligerasp. n.,Fridericia monochaetasp. n.,Fridericia nixsp. n.,Fridericia strenuasp. n.,Fridericia tuberosasp. n.,Marionina brendaesp. n.,Marionina eleonoraesp. n.,Marionina rubenssp. n.,Oconnorella chalupskyisp. n.) are new to science. Two old taxa (Fridericia bretscheriSouthern, 1907 andFridericia viridulaIssel, 1905) are revalidated and their descriptions augmented, and another two (Fridericia ilvanaIssel, 1905 andFridericia gamothecaIssel, 1905) are redescribed from new material. Nineteen known species are new records for Italy, while 30 previous Italian records are confirmed. Four new records for Algeria (Fridericia bretscheri, F. miraflores, F. tuberosasp. n.,F. viridula) and four new records for Ireland (Henlea montana, Fridericia isseli, Enchytraeus bulbosus, Marionina brendaesp. n.) are also provided. The highest number of species was found in the acid, moist soil of coniferous, beech or chestnut woods, even at low altitude. A richFridericiafauna dominates the neutral soils of the evergreen oak forests, whereas very few species are adapted to the shallow and dry soils of the maquis and garigues.

ISSN:0373-4137    

DOI:10.1080/11250009509356067

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor