摘要:

The choanocyte chambers of the haploscleridPellina semitubulosawere investigated with regard to their ultrastructural architecture. They are separated from the mesohyl and contain central cells arranged to form a uniform layer. Their cytoplasmic extensions enter the distal parts of the choanocyte collars, thus enveloping the end of the microvilli. Central cells seal up all the spaces between choanocyte collars. On the basis of choanocyte chamber architecture, a water flow dynamics and related filter feeding activity is proposed, which supports a water passageway through the small microvillar slits into the interior of the collar. A slight detachment of the central cells from the microvillar ends originates spaces for a direct water flow into the chamber. Such a plastic organization might enhance the filtration efficiency and prevent chamber clogging as well.

ISSN:1125-0003    

DOI:10.1080/11250009709356215

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

To ascertain whether the pituitary intermediate lobe is able to produce adrenocorticotropic factorsin vivoinTriturus carnifex, two groups of animals were subjected to ectopic pituitary auto‐graft. Animals of one group were sacrificed two months after the autograft; those of the second group one year after the operation. Immunocytochemical study of ACTH and MSH revealed that, in the autograft, only in the second group was the intermediate lobe immunopositive to an antiserum against synthetic ACTH (anti‐ACTH). This result supports the hypothesis that the pituitary intermediate lobe can produce adrenocorticotropic factorsin vivo.

ISSN:1125-0003    

DOI:10.1080/11250009709356216

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This study was undertaken to investigate whether, in the lizardPodarcis sicula, the expression of adrenaline synthesizing enzyme phenylethanolamine‐N‐methyltransferase (PNMT) is influenced by variations in corticosteroid levels. Adrenal glands of specimens treated with ACTH or corticosteroids were collected and stained with avidin‐biotin complex (ABC) and immunogold techniques, for light and electron microscopical observations, respectively. In non treated specimens, positive staining was mainly confined to the catecholamine containing cells (adrenaline cells), located closer to the steroidogenic ones. In treated specimens, instead, positive staining was found in all the cells of the ehromaffin portion of the gland (adrenaline and noradrenaline cells). Immunoelec‐tron microscopy confirmed the distribution of immunoreactive cells observed at the light microscope. These results support the hypothesis that corticosteroids regulate PNMT expression in reptilian adrenal glands similarly to what occurs in mammals.

ISSN:1125-0003    

DOI:10.1080/11250009709356217

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A scanning electron microscopy study was carried out on the dermal pores, ducts and wax secretion in the mealybugMaconellicoccus hirsutusGreen. The observations reveal that the hollow sticky filamentous wax plays an important role in forming the ovisac in adult females and cocoon in males. The sticky nature of the wax helps in attaching the ovisac to the substrate. Trilocular pores produce long curly filamentous wax covering the entire body of the mealybug. The multilocular disc pores produce short curly filaments in females and long ones in males. Different types of dermal pores and ducts produce specific types of wax which protect the insect from its predators and enemies. The wax filaments protect the eggs from desiccation and provide physical protection, and also avoid the eggs sticking together inside the ovisac. Moreover, adult males have several pleural pores on the posterolateral sides, differing structurally from other stages and producing filamentous wax.

ISSN:1125-0003    

DOI:10.1080/11250009709356218

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Adult and larval body size, age distribution and female fecundity, traits related to fitness in the smooth newtTriturus vulgaris meridionalis, were compared in populations differing in water stability conditions in the area surrounding Rome, near the southern limit of the distribution of this subspecies. Larval body size varied among populations at the end of metamorphosis and was positively related to water stability conditions, which probably led to differences in adult body size. In populations of temporary ponds, age at first breeding was lowered to two years. Traits of female fecundity correlated positively with body size, but not with age. The Italian smooth newt adapted to the unpredictable environment by optimizing reproductive strategies such as the exploitation of the short wet period by means of early deposition of large eggs, which can produce large larvae at metamorphosis.

ISSN:1125-0003    

DOI:10.1080/11250009709356219

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The population dynamics of a local population ofCarabus(Chrysocarabus)auronitensFabricius, 1792 has been studied in the Westphalian Lowlands on an area of 0.2 ha since 1982. During the activity seasons of this species pitfall traps were opened overnight twice a week. Beetles were individually marked and released again after every capture. In summer 1992 the area was closed by a beetle‐proof fence ‐C. auronitensis a spring breeder. During the autumn season, freshly hatched beetles are obligatorily active in foraging, whereas surviving old beetles are dormant from the end of the spring season until the next spring season. The probability of surviving from autumn until spring was mostly around 75%; survival probability from the 1st until the 2nd spring season was about 65%; from the 2nd until the 3rd spring about 60%; from the 3rd until the 4th spring about 55%; from the 4th until the 5th spring season about 40%. The phenotypical plasticity of the generations A ‘92, A ‘93 and A ‘94 is described in terms of the following traits: seasonality (date of hatching, start and end of the spring season), body size, post‐ecdysial maturation, weight development during spring and capture rate in the spring seasons. These traits were examined with respect to their influence on individual fitness of viability. The probability of surviving from the autumn until the first spring season was affected in the following way: (1) Time of hatching per se did not influence the survival probability. (2) Early hatching beetles that are small showed an enlarged mortality risk. Concerning the probability of surviving a spring season, it was observed: (3) The individual survival probability was higher, the later a beetle was caught for the first time in a spring season. The relative weight of early appearing females was relatively low at first capture; however, surviving and non‐surviving females of this fraction did not differ with respect to their mean relative weight. (4) Females and males frequently caught in a spring season had a reduced chance of surviving; most of these animals belonged to the fraction of late disappearing specimens. On the other hand, late females and males that had been less frequently caught had a high viability fitness. (5) There were distinct, but non‐uniform influences of body size upon survival probability: in males, the probability of surviving the 1st spring season was highest in a lower middle class of size; the probability of surviving the 2nd spring season was relatively low in small females and males. The main points of discussion are (1) possible objections to the measurement of viability fitness by capture‐recapture data; (2) the heritability of variable phenotypical traits; (3) the question whether the selection‐responding polymorphisms detected can contribute to the genetic adaptation of this local population to environmental changes.

ISSN:1125-0003    

DOI:10.1080/11250009709356220

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The presence of bird species in the city of Turin (northwestern Italy) was recorded along a vegetation gradient ranging from truly urban environments to completely wooded areas. Two methods of censusing urban birds were used to focus upon the detection of all species (Atlas‐Type Method) and the evaluation of species abundance in each habitat (Transect‐Type Method).

ISSN:1125-0003    

DOI:10.1080/11250009709356221

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Seven foxes (Vulpes vulpes) were studied by radio‐tracking from 3 to 12 months/animal, and a total of 4 005 fixes was made. Seasonal home ranges were calculated using several methods giving a minimum of 29–3 and a maximum of 268.7 ha (100% Minimum Convex Polygon). The land use by the foxes was monitored and the habitat analysed. No uniform home range use was revealed, but several core areas were identified; 1–3 of rest and 1–4 of activity being found, seasonally, in each home range. The distribution of core areas of rest and activity suggested that home range size and shape were determined not only by core areas of activity but also by resting sites. The Kernel centres of rest were localised mainly in natural vegetation (85.1%) and sometimes in cereal fields (12.1%) or in hay‐lofts (2.8%), while those of activity were in anthropic environments (56.1%) as well as in natural vegetation (43–9%), but with seasonal variations. Activity was mainly nocturnal, but interrupted by resting periods. Some individual variations were also revealed in home range size, number of core areas, habitat use and daily activity.

ISSN:1125-0003    

DOI:10.1080/11250009709356222

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Codonorchis octaedrusis recorded for the first time since its discovery by Haeckel in 1879. A hydroid colony collected in a cave of the Apulian Coast (between the Ionian and the Adriatic Seas) produced several medusae which have been reared to maturity. This is the first complete description of the species, which was previously considered as doubtful, as was the genusCodonorchis. The diagnostic features for the genus are: hydroid small, naked, sessile, with a single row of few tentacles, gono‐phores on hydrorhiza, medusa with apical projection with apical process from the manubrium, perradial, interradial and adradial ocellate bulbs, two perradial tentacles, horseshoe‐shaped interradial gonads, small mesenteries. The list of Mediterranean hydroidomedusae is updated with the new (or overlooked) records since the last published list (1993). The increase in species number is great (about 10%), showing that the knowledge of biodiversity of even a well‐studied sea as the Mediterranean is far from being complete.

ISSN:1125-0003    

DOI:10.1080/11250009709356223

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Two new species ofNitocrellaChappuis, 1923,N. pesceisp. n. andN. kunzisp. n., from the Presciano spring system (Tirino River, Abruzzo, central Italy) are described. Both species fit into thehirta‐group ofNitocrella, as defined by Petkovski (1976). From an ecological point of view, they are true stygobiont species, linked to different biotopes of the crenal habitat.

ISSN:1125-0003    

DOI:10.1080/11250009709356224

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor