Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 22

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
The main aim of this paper has been to assess natural values of the Janówek area (Wrocław) from the geobotanical point of view. The area is a valuable natural territory because a rich population of Salvinia natans (protected by law and vulnerable species VU category), consisting of about 1000 handsome specimens occurs here. There are also situated localities of some rare species in Lower Silesia, i.e. Cyperus fuscus (NT cat.), Kickxia elatine (NT), Sherardia arvensis (LC) and Euphorbia exigua (LC), and a borderland, fragmentarily developed form of Kickxietum spuriae association, a segetal weeds community of the Caucalidion lappulae alliance, as well as the area of ecological use Łacha Farna Old River-bed. Probably, within the Janówek area a rare butterfly species Euphydryas maturna L. appears and this is one of the only two localities in Poland. The western part of the investigated ground should be conserved as the Protected Landscape Area.
The paper describes the vascular flora and plant communities of the Łacha Farna Old River-bed area of ecological use which is situated in Wrocław city (SW Poland). The full list of recorded plants comprises 173 taxa. The most interesting plant is Ceratophyllum submersum (the rare species in Lower Silesia LC category). The vegetation is also strongly differential 41 plant communities belonging to 8 classes occur here. The two richest classes are: Phragmitetea australis and Artemisietea vulgaris (10 communities found for each). There is only locality of Ceratophylletum submersi association (Potametea class), never recorded earlier on the area and its vicinity. The paper also provides precise descriptions of the localities examined to be used later for all the subsequent comparisons to identify the directions of changes within the studied oxbow lake. The distribution of the analysed localities and protected species is shown as Fig. 1. All the features of the investigated area confirm that it should be protected by local authorities.
A specimen of Trochulus hispidus from Buchenbach, Germany, had its male and female parts of thereproductive system completely separated. The female part lacked auxiliary organs. The male part opened into the genital atrium, but the vas deferens was blind-ended in a way precluding sperm transfer.
Selected life-cycle and population parameters of a common Euro-Siberian wetland snail – Succinea putris (L.) – were studied in the field and in the laboratory. In the field the snails reproduced at least from April till September, with April–May and August–September peaks; only one such peak (April) was observed in the laboratory, though the snails reproduced throughout the year. The changes in population size structure in the field and the laboratory results (life span 210–420 days, mean 309) indicated semelparity. Growth in the laboratory included two phases: slow (November–March) and fast (June–October); which phase came first during the life cycle depended on the date of hatching. The growth rate in the field corresponded closely with the fast-phase growth in the laboratory. The smallest reproducing individual was slightly over 2.8 whorls; snails of 3.0 whorls were regularly observed to produce eggs (maximum number of whorls in adults: 4.0). Sexual maturity was attained in ca. 160 days. The eggs (non-calcified, translucent, spherical, 1.7–2.0 mm in diameter) were laid in batches, 5–64 per batch; the eggs within a batch were glued together. The batch dimensions were 3.5–25.7×2.2–24.7 mm. The time to lay a batch was 20–35 minutes. Forty-eight snails produced 74 batches within 12 months. The duration of the egg phase was 11–28 days, which might indicate egg retention of varied duration; hatching was asynchronous, spanning 1–12 days within a batch. The hatchlings had shells of 1.1–1.2 whorls; hatching success was 95%. Neither uniparental reproduction, nor egg or juvenile cannibalism were observed. When compared to data in the literature, our results imply that Succinea putris displays substantial local variation in life-cycle traits.We also provide an overview table to discuss similarities and adaptive radiation in the European succineid species.
The paper discusses arguments for the preservation of the original spelling of the species-level name for Trochulus lubomirski (Ślósarski, 1881) versus arguments for the preservation of the amended spelling lubomirskii. The authors argue that the obvious "prevailing usage" of the spelling lubomirskii should be taken as the decisive argument to preserve this form of spelling under Art. 33.3.1 of the International Code of Zoological Nomenclature.
During laboratory studies on the reproductive biology of Vallonia pulchella and V. costata we observed an unusual behaviour in adults and juveniles of both species. The snails moved with their heads and radulae over the egg surface as if feeding. The examination of the egg shell revealed the presence of the fungus Arthrobotrys oligospora, which commonly occurs in the soil and has multiple lifestyles: it is known as a nematode pathogen, a saprophyte and a coloniser of plant roots. The extraordinary behaviour of Vallonia may be associated with the presence of mycelium on the egg surface. We hypothesise three possible explanations of egg grooming: (1) parental care, (2) trophic behaviour and (3) the infection can constitute a means of defence against nematodes, which are known to be predators of snails and slugs as well as their eggs. The removal of the fungus is not associated with overcrowding, but may be a selective advantage when combined with feeding.
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.