摘要:

Fifteen days oldOreochromis niloticusjuveniles were gradually adapted to 10, 20, 30 and 35‰ sea water. The morphology of the oesophagus epithelium was observed at different intervals after transfer to higher salinities. At 10‰, no changes are evident compared to fresh water controls. Regions of single columnar epithelium, reported to play a role in ion trasport, appear within the normal pluristratified one at 20, 30 and 35‰ four weeks after transfer from fresh water. These modifications widen in individuals left for longer at high salinities.

ISSN:0373-4137    

DOI:10.1080/11250008809386600

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A revision of the morphology ofNectocaris pteryxConway Morris, 1976, and a comparison with the morphology of living Chor‐dates supports the inclusion ofNectocarisin the phylum Chordata. The supposed somewhat crustacean‐like valves, which sheath the forepart of the animal are probably better considered as being the dermo‐epidermal folds that limit the peribranchial cavity of most lower Chordates, while the tail closely resembles the tail of the larval Tunicata and ofBranchiostoma.The large eyes are a unique feature. A new subphylum within the Chordata is needed forNectocaris.

ISSN:0373-4137    

DOI:10.1080/11250008809386601

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Tetranchyroderma sardum, a new species of macrodasyid gastrotrich, was found in litoral sand from Sardinia. It is characterized by: 1. two pairs of cephalic tentacles, one rod‐like and the other knob‐like; 2. twenty‐two pairs of ventrolateral adhesive tubes; 3. three furcal adhesive tubes and 4. thirteen longitudinal rows of pen‐tancres.T. sardumclosely resemblesT. esarabdophorumandT. anten‐natum, both collected from the Mediterranean Sea.

ISSN:0373-4137    

DOI:10.1080/11250008809386602

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The rare and poorly known lumbricidEophila tellinii, type species of the genus inquirendumEophila(Rosa, 1894), is described anew. is quite different from the type species of the lumbricid genera escribed before 1894: thus, according to international usage, the genusEophila isvalid. A new lumbricid from Turkey together with other less known endemic species that may be assigned to this genus are described. The close relationships between the genusSnhenthecà(Bouché, 1972) andEophilaare discussed.

ISSN:0373-4137    

DOI:10.1080/11250008809386603

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Biogeographical provinces have been defined for the earthworm fauna of continental Portugal by subjecting data obtained at 100 sites distributed among 23 zones to correspondence analysis and dendritic clustering so as to detect faunistically similar groups of zones. Various measures of species importance and interspecific association were calculated in order to characterize the provinces so detected. On the basis of our findings and the existing literature, ve propose that Galicia and Northern Portugal be included in a Galaico‐Lusitanian Province characterized by the joint dominance ofA. caliginosaand the three typical speciesD. madeirensis, D. taedraandA. olivtirae, which are accompanied by other, more widely distributed species; and that continental Portugal south of he River Mondego be considered an Atlantic Province character‐zed by the dominance ofA. caliginosa, A. roseaand the≪A. molleri≫:omplex species, and by the absence of the three typical Northern species and all species of the genusLumbricus.

ISSN:0373-4137    

DOI:10.1080/11250008809386604

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

To investigate the significance of chemical and size stimuli for cocoon recognition and nursing behaviour inFormica cunicularia, nurses of this species were given a choice‐test between homospeci‐fic cocoons (Fc) and respectively:Latins alienuscocoons (La) which are much smaller than Fc, L. alienuscocoons (LaT) impregnated with a whole‐cocoon chemical extract of Fc;Formica lugubriscocoons (Fl) which are similar in size to Fc;F. lugubriscocoons (FlT) imbued with the Fc extract; and LaT cocoons. In this latter case the homospecific cocoons (FcT) were masked by whole‐cocoon chemical extract of La. As adoption criterion we used the life span of each kind of cocoon supplied at the choice‐test and tended by the ants for the following 13 days. La and LaT cocoons were never adopted but rapidly destroyed or eaten. On the contrary, FlT cocoons were tended by the ant‐workers in a manner similar to the Fc ones, whereas the Fl cocoons were generally destroyed. Finally, the FcT cocoons were considered alien and thus not adopted. These results clearly indicate that cocoon discrimination and care in this ant species is based on a synergistic perception of odour and size.

ISSN:0373-4137    

DOI:10.1080/11250008809386605

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

ISSN:0373-4137    

DOI:10.1080/11250008809386637

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

ISSN:0373-4137    

DOI:10.1080/11250008809386639

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The ovary of female supplementary reproductives is constituted by panoistic‐type ovarioles containing a linear array of germ cells in successive stages of differentiation. In the distal region of the germarium, germ cells cannot be morphologically and ultrastructu‐rally discriminated from somatic cells. In the middle and proximal region of the germarium, oogonia at two developmental stages have been identified. The oocytes at the beginning of meiosis are characterized by nuclear vacuoles and by a polar localization of cell organelles, in addition to synaptonemal complexes. The post‐pachytcne oocytes are partially isolated by prefollicular cell extensions and show annulate lamellae and Balbiani bodies. During previtellogenesis, the oolemma forms microvilli, with coated pits and vesicles, about 60 nm in diameter, at their bases. At the onset of vitellogenesis, coated pits and vesicles about 120 nm in diameter and early yolk globules appear in the cortical ooplasm. At a later stage, wide spaces filled with flocculent material are formed between the oocyte and follicular cells, and coated pits and vesicles about 180 nm in diameter are found in the cortical ooplasm. In late vitellogenesis, the endocytotic activity decreases, and large yolk globules and lipid droplets fill the whole ooplasm. The ultrastructural features during differentiation provide evidence of organelle renewal before vitellogenesis and then exogenous yolk synthesis.

ISSN:0373-4137    

DOI:10.1080/11250008809386606

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

In Eukaryotic organisms morphogenesis is linked to peculiar properties of plasmalemma and cytoskeleton. In the Protozoa these properties allow the formation of structures of colonial type derived either from the descent of a single cell or from the confluence of isolated cells. In Plants morphogenesis is linked to the orienting of spindles and divisory plans during mitoses, while in the Metazoa cells reach their position in the embryonic frame by active morphogenetic movements: their number and relative position are controlled by regulating mechanisms.

ISSN:0373-4137    

DOI:10.1080/11250008809386607

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor