Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 9

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych:  pancerze
help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
Spatial statistics on the positions of trilobite tubercles indicate the existence of a developmental spacing mechanism. Similar spacing between sensory bristles, due to lateral inhibition, is well known in insects, and the genetic basis for these patterns has been thoroughly studied. Tubercles (granules) in the Middle Cambrian trilobite Paradoxides forchhammeri are spaced out, but otherwise randomly positioned. Assuming that similar genetic principles are in operation for the positioning of peripheral neuronal elements in all arthropods, it can even be speculated that genes with functions similar to Delta, Notch, achaete and scute were active in trilobite cuticular patterning. Also, in P. forchhammeri, terrace lines (ridges) seem to display transitions into granulation, indicating that these two types of structure share an underlying pattern formation mechanism.
Gut content of Branchiobdella spp. was examined in 83-945 individuals belonging to 4 species, collected from 31 individuals of Astacus astacus (L.) and 12 individuals of Pontastacus leptodactylus (Esch.) from north-western and southern Poland. The results show the food of B. hexodonta Gruber, 1883 dwelling in the crayfish gill cavity to include fragments of the crayfish gills, which identifies the species as a parasite. In contrast, B. parasita Henle, 1835, B. kozarovi Subchev, 1978 and B. balcanica sketi Karaman, 1967 are found on the external covers of the crayfish are not parasitic. They feed on diverse items derived from the ambient environment and are thus epibiontic. Cannibalism was observed in all the species examined. Neither cannibalism nor the presence of larvae-containing cocoons of Argulus foliaceus (L.) (Branchiura), a fish parasite, on the crayfish carapace has been recorded in the literature so far.
Comparison of cuticular ultrastructure in Antarctidromia inflata Förster, 1985 from the Miocene Cape Melville Formation on King George Island, Antarctica, with that of the confamilial, extant Homolodromia paradoxa A. Milne Edwards, 1880 suggests that the more rigid carapace of the fossil form results from a relatively thicker, more strongly calcified exocuticle. Epicuticle, exocuticle, and endocuticle are all recognizable on the fossils; however, adherence of the epicuticle to the counterpart may result in misinterpretation of the fine sculpture on the carapace. Absence of dissolution features in the endocuticle confirm conclusions, based upon completeness of remains, that the specimens of Antarctidromia inflata represent corpses, not molts.
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 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.