Heterosis in the common European water frog

1979 ◽  
Vol 66 (5) ◽  
pp. 268-269 ◽  
Author(s):  
H. G. Tunner ◽  
H. Nopp
Keyword(s):  
Water Frog ◽  
European Water ◽  
The Common ◽  
European Water Frog

Conservation of the introgressed European water frog complex using molecular tools

2009 ◽  
Vol 18 (6) ◽  
pp. 1071-1087 ◽  
Author(s):  
G. HOLSBEEK ◽  
G. E. MAES ◽  
L. DE MEESTER ◽  
F. A. M. VOLCKAERT
Keyword(s):  
Molecular Tools ◽  
Water Frog ◽  
European Water ◽  
European Water Frog

scholarly journals Gametogenesis of intergroup hybrids of hemiclonal frogs

2007 ◽  
Vol 89 (1) ◽  
pp. 39-45 ◽  
Author(s):  
MATILDE RAGGHIANTI ◽  
STEFANIA BUCCI ◽  
SILVIA MARRACCI ◽  
CLAUDIO CASOLA ◽  
GIORGIO MANCINO ◽  
...  
Keyword(s):  
Germ Line ◽  
Parental Species ◽  
Rana Esculenta ◽  
Population System ◽  
F1 Hybrid ◽  
Water Frog ◽  
System Type ◽  
Genome Exclusion ◽  
European Water Frog

European water frog hybrids Rana esculenta (R. ridibunda×R. lessonae) reproduce hemiclonally, by hybridogenesis: in the germ line they exclude the genome of one parental species and produce haploid gametes with an unrecombined genome of the other parental species. In the widespread L-E population system, both sexes of hybrids (E) coexist with R. lessonae (L). They exclude the lessonae genome and produce ridibunda gametes. In the R-E system, hybrid males coexist with R. ridibunda (R); they exclude either their ridibunda or their lessonae genome and produce sperm with a lessonae or with a ridibunda genome or a mixture of both kinds of sperm. We examined 13 male offspring, 12 of which were from crosses between L-E system and R-E system frogs. All were somatically hybrid. With one exception, they excluded the lessonae genome in the germ line and subsequently endoreduplicated the ridibunda genome. Spermatogonial metaphases contained a haploid or a diploid number of ridibunda chromosomes, identified through in situ hybridization to a satellite DNA marker, and by spermatocyte I metaphases containing a haploid number of ridibunda bivalents. The exception, an F1 hybrid between L-E system R. lessonae and R-E system R. ridibunda, was not hybridogenetic, showed no genome exclusion, and evidenced a disturbed gametogenesis resulting from the combination of two heterospecific genomes. None of the hybridogenetic hybrids showed any cell lines excluding the ridibunda genome, the pattern most frequent in hybrids of the R-E system, unique to that system, and essential for its persistence. A particular combination of R-E system lessonae and R-E system ridibunda genomes seems necessary to induce the R-E system type of hemiclonal gametogenesis.

Development of testes and differentiation of germ cells in water frogs of the Rana esculenta - complex (Amphibia, Anura)

1999 ◽  
Vol 20 (3) ◽  
pp. 251-263 ◽  
Author(s):  
Jolanta Bartmańska ◽  
Maria Ogielska
Keyword(s):  
Germ Cells ◽  
Parental Species ◽  
Sex Differentiation ◽  
Gonad Development ◽  
Rana Esculenta ◽  
Water Frog ◽  
New Class ◽  
Water Frogs ◽  
Rana Esculenta Complex ◽  
European Water Frog

AbstractThe European water frog, Rana esculenta, is a hybrid whose genome is composed of haploid chromosome sets of its parental species R. lessonae and R. ridibunda. Prior to meiosis one of the parental sets is discarded and the other is duplicated (hybridogenesis). In the parental species sex differentiation begins at tadpole stages 28-30 (Gosner, 1960), at stages 30-36 the testes are composed of proliferating pale spermatogonia 1°. At stages 36-39 a new class of spermatogonia I° (dark) appears. Before first hibernation, seminiferous lobules are filled with cysts containing germ cells at various stages of spermatogenesis up to elongating spermatids. In R. esculenta gonad development is affected from the earliest stages: the gonads are smaller and composed of reduced number of spermatogonia I°. The phase of pale spermatogonia I° proliferation is prolonged up to the second year of life. The structure of the gonads, as well as that of germ cells themselves, are often abnormal.

Age structure, size and growth rate of water frogs from central European natural Pelophylax ridibundus-Pelophylax esculentus mixed populations estimated by skeletochronology

2010 ◽  
Vol 31 (2) ◽  
pp. 239-250 ◽  
Author(s):  
Małgorzata Socha ◽  
Maria Ogielska
Keyword(s):  
Parental Species ◽  
Rana Esculenta ◽  
Breeding Sites ◽  
Central European ◽  
Water Frog ◽  
Water Frogs ◽  
Pelophylax Esculentus ◽  
Mixed Populations ◽  
The Difference ◽  
European Water Frog

AbstractCentral European water frog Pelophylax esculentus (formerly known as Rana esculenta) is a natural hybrid between P. lessonae and P. ridibundus. The hybrids reproduce by hybridogenesis and usually share populations with one of the parental species. Natural ridibundus-esculentus (R-E) mixed populations are rare. The population described herein is composed of 80% P. ridibundus and 20% P. esculentus represented by both sexes. We analyzed 159 adults and 228 juveniles. Age of adults collected from breeding sites ranged from 2 to 6 years in males and from 3 to 7 years in females of both taxa. The percentage of individuals older than 5 years was low. Average age of P. ridibundus was higher than that of P. esculentus. In P. ridibundus the average age of females was higher than that of males. In P. esculentus the difference between ages of females and males was not significant. Measurements of yearly radial growth of long bones revealed that the frogs grew intensively before reaching sexual maturity (3 years for females and 2 years for males). In the group of juveniles before I hibernation, P. esculentus were significantly bigger than P. ridibundus, however, there was no difference in body size between both taxa after I hibernation i.e., before the start of a new growth season. Mean LAG-1 diameters were significantly greater in adults P. ridibundus than in juveniles after I hibernation, but not in P. esculentus.

Voluntary arrangements to cope with diffuse pollution from agriculture and their role in European water policy

2002 ◽  
Vol 46 (6-7) ◽  
pp. 27-34 ◽  
Author(s):  
I. Heinz ◽  
K. Andrews ◽  
F. Brouwer ◽  
T. Zabel
Keyword(s):  
Agricultural Policy ◽  
Water Policy ◽  
Diffuse Pollution ◽  
Farming Practices ◽  
Local Conditions ◽  
Intensive Farming ◽  
European Water ◽  
Catchment Areas ◽  
The Common ◽  
The Eu

A limited number of Member States in the EU have gained experience with establishing co-operative agreements between agriculture and the water sector. Their main aim is to reduce or prevent water pollution caused by intensive farming practices. The research has shown that significant changes in farming practices have been achieved as a result of negotiation between farmers and water suppliers. Consequently, in many catchment areas improvements in water quality can be observed. Co-operative agreements have the important advantage that the measures taken can be tailored to the different local conditions in catchment areas. Reducing diffuse pollution resulting from intensive agriculture is one of the main issues of the EU Water Framework Directive. The current paper builds on the results of a EU-wide research project which examines the role co-operative agreements can play in water policy and the Common Agricultural Policy.

Catalogue reduction techniques

1978 ◽  
Vol 48 ◽  
pp. 389-390 ◽  
Author(s):  
Chr. de Vegt
Keyword(s):  
Adjustment Process ◽  
Proper Motions ◽  
Measuring Process ◽  
Aerial Photogrammetry ◽  
Reduction Techniques ◽  
Observational Technique ◽  
The Common ◽  
Astrometric Data

AbstractReduction techniques as applied to astrometric data material tend to split up traditionally into at least two different classes according to the observational technique used, namely transit circle observations and photographic observations. Although it is not realized fully in practice at present, the application of a blockadjustment technique for all kind of catalogue reductions is suggested. The term blockadjustment shall denote in this context the common adjustment of the principal unknowns which are the positions, proper motions and certain reduction parameters modelling the systematic properties of the observational process. Especially for old epoch catalogue data we frequently meet the situation that no independent detailed information on the telescope properties and other instrumental parameters, describing for example the measuring process, is available from special calibration observations or measurements; therefore the adjustment process should be highly self-calibrating, that means: all necessary information has to be extracted from the catalogue data themselves. Successful applications of this concept have been made already in the field of aerial photogrammetry.

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