摘要:

The ontogenesis of isozyme patterns of alcohol dehydrogenase (ADH), glycerol‐3‐phosphate dehydrogenase (α‐GPDH), lactate dehydrogenase (LDH), malate dehydrogenase (MDH), glucose‐6‐phosphate dehydrogenase (G‐6‐PD) and glucosephosphate isomer‐ase (GPI) inDicentrarchus labraxwas studied.

ISSN:0373-4137    

DOI:10.1080/11250008909355615

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

We report preliminary findings on the development ofLernaea cyprinaceafrom cleavage to hatching. The eggs are centrolecithal with superficial cleavage. Nucleoli were found in the nuclei of the perilecithal syncytium. Gastrulation occurs byin situaggregation of cells, without evident morphogenetic movements.

ISSN:0373-4137    

DOI:10.1080/11250008909355616

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The ultrastructure of the spermatozoon of the following gall‐midge flies (Diptera, Cecidomyiidae) is described:Rhopalomyia foliar‐um, Wachtliella riparia, Oligotrophus juniperinus, Semudobia betulae, Cys‐tiphora sonchii, Jaapiella cirsiicola, Rabdophaga rosaria, Macrolabis luceti, Dasineura pseudococcus, D. loewiana, D. affinis, D. serotina, D. euphor‐biae, D. gleditchiae, Mikiola fagi, Lasioptera rubi.The spermatozoon of the whole Oligotrophidi group is characterized by the presence of a great number of singlet microtubules in addition to an axoneme of 9+0 type. The microtubules penetrate peripheral outfoldings of the cell membrane. The spermatozoa are immotile and the microtubu‐lar doublets lack dynein arms. The nucleus contains large dense bodies and there is no acrosome. Sperm characters in the super‐tribes Oligotrophidi and Lasiopteridi are very similar; there are thus no strong reasons to separate these groups. Sperm data rather support the proposal that subfamily Cecidomyiinae is subdivided in three supertribes only (Lasiopteridi. Asphondyliidi and Cecidomyii‐di).

ISSN:0373-4137    

DOI:10.1080/11250008909355617

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The ultrastructure ofHolothuria poliicoelomocytes is described and related to cell functions. Amebocytes, spherule cells and progenitor cells are the major circulating cellular types. Two morphological phases (bladder and filipodial) of the amebocytes are distinguished. Type I and Type II spherule cells are described on the basis of the morphological and ultrastructural characteristics of their granules. Maturative stages of these cells are also observed. Probably a third type of spherule cell is present. It could correspond to the acidophilic and Schmorl's positive cells. Progenitor cells lacking elaborate cytoplasmic specialization and with a probable staminal function are also normal circulating coelomocytes ofHolothuria polii.

ISSN:0373-4137    

DOI:10.1080/11250008909355618

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The regulation of the hydric content in three species of terrestrial oligochaetes,Eiseniella tetraedra, Allolobophota motteriandEisenia foetida,when submerged in water has been investigated.

ISSN:0373-4137    

DOI:10.1080/11250008909355619

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Electrophysiologic techniques were used to study the bioelectri‐cal activity of the ovipositor chemosensilla of the apple maggot fly,Rhagoletis pomonellaWalsh (Diptera, Tephritidae), in response to contact and volatile stimulation with various chemicals associated with fruits. The spike amplitude peaks evoked by contact stimuli showed that the chemosensilla are sensitive to glucose, malic acid, and quinic acid but not to fructose. There is evidence that ovipositor chemosensilla may provide information allowing glucose to be distinguished from the two acids. In addition, slow compound potentials were recorded in response to various volatiles associated with fruits. The contact stimulation experiments indicate that the ovipositor chemosensilla permit females to distinguish between a sugar and two acids that occur in apples in variable concentrations depending on the stage of ripeness, and that this difference may provide the fly with information about host suitability and/or quality.

ISSN:0373-4137    

DOI:10.1080/11250008909355620

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

This study examines the characteristics of the breeding microhabitats of threeAcrocephalinae(Aves) species inhabiting a marshland surrounding Lake Alserio (NW Italy). A total of 45 territories (24 forAcrocephalus scirpaceus,13 forAcrocephalus arundinaceusand 8 forAcrocephalus palustris)were mapped. In each territory 18 environmental and vegetation variables were measured in 3 to 5 sampling plots in the estimated centre of the territory or in the singing perches of males. Data were subjected to Principal Component Analysis (PCA) and to Discriminant Function Analysis (DFA). According to PCA, the breeding microhabitats of the species are ordered along the first principal component, which is strongly related to several structural and cover variables. Horizontal overlap of territories was observed forA. scirpaceusandA. arundinaceus,but not between these andA. palustris.Conversely, DFA showed that breeding microhabitat configurations are different forA. arundinaceusas compared withA. scirpaceusandA. palustris,but not completely distinguishable between the last two species. In conclusion, the data suggest thatA. arundinaceusandA. scirpaceushave different ecological requirements and their territories may overlap where the vegetation is suitable for both species. On the other hand,A. scirpaceusandA. palustrishave partially similar ecological requirements, but are horizontally well‐spaced, in agreement with the hypothesis of their interspecific territoriality.

ISSN:0373-4137    

DOI:10.1080/11250008909355621

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Groups ofKalotermes flavicolliswere removed from their wild nest and colony in order to study the digging of their new shelter in an agar/sawdust mixture. On the first day the insects dug numerous tunnels, some of which (usually the shortest) were soon abandoned. Digging continued with great regularity and finally the nests consisted mainly of tunnels with few branches and communication passages.

ISSN:0373-4137    

DOI:10.1080/11250008909355622

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

We studied the three main components of trophic niches in the richest assemblages of breeding gulls and terns in Italy (8 species) that typify the communities of the large deltas of Mediterranean Europe. Each species feeds mainly on fish, except for the gull‐billed tern that feeds essentially on terrestrial vertebrates. Other prey contributed slightly to the energy balance, although small invertebrates prevailed numerically in the diets of the Mediterranean and black‐headed gulls. The seabirds cumulatively consumed a variety of fish, in frequencies that closely reflected the latter's abundance. Selection of fish species by each seabird were strongly determined by the bird's foraging habitat, and not by any preference for particular prey. The size of the prey was related to the size of the seabird. The diurnal rhythms of feeding activity were uniform, and the time component did not contribute to niche segregation. Dietary patterns suggest that within the overall space of their niches, the seabirds select trophic resources mainly through preferences for specific types of foraging habitats with their associated prey types. In the selected habitats, various prey types are exploited in relation to availability, and prey is selected on the basis of size. Although it is well known that interspecific competition is not proportional to the overlap in resource use, in our community of seabirds evidence that competition promotes niche segregation comes from the observation that overlap in the foraging and feeding niches are clearly complementary, and that the foraging niches and the preferred prey size seem to be regularly rather than randomly spaced. We suggest that the seabirds segregate their trophic niches by selecting different macro‐habitats, while their overlap in food is high, thus confirming earlier reports that habitat is more important than food in the segregation of trophic niches.

ISSN:0373-4137    

DOI:10.1080/11250008909355623

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A spined loach (Cobitis taeniaL.) population inhabiting a small river in northern Italy was studied. At each age, females were larger than males and both sexes showed a marked seasonal pattern of growth with a high rate from May through November. Total population density averaged 2.38 ± 1.6 ind/m2and the annual production in the study area was 3.3 g/m2. The first year class during the summer accounts for more than half the production. The sex‐ratio did not significantly depart from unity. Most individuals achieved sexual maturity in their second spring after hatching and spawning occurred in late May and June. The relationship between female total length and fecundity was lnF=l.07+0.065L. Males showing three different liveries were found throughout the year; the seasonal variation in their frequency suggested that males change livery in relation to their reproductive conditions.

ISSN:0373-4137    

DOI:10.1080/11250008909355624

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor