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D Kruska

Publications and source records attributed to D Kruska.

13 recordsLinked to original sources
PubMed1993

Evidence of decrease in brain size in ranch mink, Mustela vison f. dom., during subadult postnatal ontogenesis.

Total brain size and the volume of several brain parts were compared in male and female ranch mink of varying age and body size in an attempt to quantify postnatal maturation and growth processes in this altricial species. Volumes of fresh whole brains and of different brain parts were calculated from prepared histological sections from juvenile (2- to 3-month-old), subadult (5-month-old), and adult (older than 7 months) individuals. Allometrical calculations were performed on the basis of body weight. Changes in size of different parts of the brain obtained to different degrees were found to be dependent on age but independent of body size. From the juvenile stage to the subadult stage, total brain size remains unchanged, although most major brain parts increase in size, while the grey matter of the isocortex decreases. During subsequent development from subadult to adult, total brain size evidently decreases. Within the brain all major structures also decrease in size, except for the medulla oblongata and the mesencephalon, which remains relatively stable in size. The grey matter of the isocortex shows the greatest decrease, followed by the allocortex and corpus striatum, the cerebellum, the white matter of the isocortex, and the diencephalon. Thus, an unusual but evident 'overshoot' in size of the total brain and certain parts apparently occurs in this species before adulthood is reached. This phenomenon is discussed in connection with size changes concomitant with domestication as well as with cageing of individuals and with postnatal and seasonal size changes known from some soricid species as the so-called Dehnel phenomenon.

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PubMed1990

Volumetric comparison of auditory structures in the brains of European wild boars (Sus scrofa) and domestic pigs (Sus scrofa f. dom.).

The size of certain brain parts involved in the processing of auditory stimuli was measured in European wild boars (Sus scrofa) and domestic pigs (Sus scrofa f. dom.). By means of intraspecific allometric methods for analyzing the brain weight to body weight relationships, the volumes were compared in both groups. In general, all measured structures were smaller in the domestic form, indicating that domestication has led to a decrease in the size of auditory brain parts. Within the auditory system, however, differences in the amount of decrease were observed in different structures. The cochlear nucleus is only 15% smaller and the medial geniculate body about 20% smaller in the domestic form, whereas the superior olive (28%), the inferior colliculus (28%), the grey matter of the auditory cortex (32%) and the lateral lemniscus (33%) are decreased more significantly. Furthermore, in the medial superior olivary nucleus, there are 9% fewer neurons in the domestic form, but the neuron density has increased by 28%.

Animals↗
PubMed1987

How fast can total brain size change in mammals?

Changes in size can be ascertained for mammalian brains. These changes must be valued as functional adaptations. The most important biological mechanisms are almost certainly the limited variability of brain size within species caused by genetic diversity and changes of selection factors when conquest of new ecological niches takes place. During phylogenetic evolution such changes only occur very slowly. Thus very small changes in brain size per time unit during the radiation of species must be expected. During domestication a similar process took place on the species level only much more accelerated and in other directions. Decrease of brain size characterises the change from wild living ancestors to domesticated mammals. In connection herewith significantly stronger changes in brain size per time unit could be proved for the initial phase of domestication. Furthermore, according to hitherto existing results on the brain, Dollo's law of the irreversible development of species characters during phylogenetic evolution also seems to prove right during domestication as the feralisation of domestic mammals doesn't lead to increase in brain size. Unusual decreases in brain size during ontogenetic development occur in certain basal mammals. Those are significant and they occur within extreme short periods of time. Although the biological importance of this phenomenon still remains unsolved it nevertheless is evident that brain ontogenesis in mammals may run different ways.

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PubMed1977

[Comparative-quantitative investigations of brains of wild and laboratory rats].

By means of serial sections at equal intervals through the brains of 8 Norway rats and 8 laboratory rats the fresh volume sizes of the optic regions lateral geniculate nucleus (pars dorsalis), striate area, superior colliculus and tractus opticus were determined. Furthermore the sizes of neocortical white matter and grey matter were measured in the same way. On the basis of the intraspecific allometric relation between brain size and body size differences in size of the structures between wild and domestic animals could be established. Especially the subcortical terminal regions of visual input and the striate area showed size reductions of different intensity from Norway to laboratory rats, whereas the optic tract underwent increase. The volume of grey matter showed decrease too and for the white matter no size differences between both groups came out as a result. These changes in size of nervous tissue from Norway rats to laboratory rats were partly discussed as due to the special changes of environment through domestication but in this special case also as due to the effect caused by the albinism of the investigated laboratory rats.

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PubMed1975

[Comparative quantitative study on brains of wild and laboratory rats. I. Comparison of volume of total brain and classical brain parts].

The intraspecific allometric relation between brain weight and body weight of wild Norway rats and laboratory rats was gained from sufficient material. The intraspecific allometry exponent a=0.25, being typical for mammals, also came out as a result for Norway and laboratory rats. But laboratory rats have 8.3% less brain substance at a comparable body weight. This decrease in brain size was interpreted as an adaption to the specific conditions of domestication and discussed accordingly. Futhermore the fresh volumes of the fundamental brain parts telencephalon, diencephalon, mesencephalon, cerebellum, medulla oblongata, neocortex, corpus striatum and allocortex were ascertained by means of serial sections of 8 Norway and 8 laboratory rats, and they were compared with each other by their average brain proporationing. Consequently, differently strong reduction intensities in the sizes of these brain parts from 1.6% (medulla oblongata) to 12.5% (neocortex) became evident. The high reduction values of corpus striatum (10.9%) and cerebellum (10.3%) were especially remarkable. They almost reached the same degree as the forebrain (10.6%). The size reduction of the measured brain parts of rats, caused by domestication were compared with the results of other domestic mammals and discussed accordingly.

Animals↗
PubMed1975

[Comparative quantitative study on brains of wild and laboratory rats. II. Comparison of size of allocortical brain centers].

The size of allocortical regions in the telencephalon of 8 wild Norway rats and 8 laboratory rats of different body size were measured by means of serial sections at equal intervals. On the intraspecific allometric relation between brain size and body size differences in size of the measured structures between wild and domestic animals came out as a result. The olfactory regions of the allocortex in totality were 5.9% smaller in laboratory than in Norway rats. Included in this were, however, size increase of the structures bulbus olfactorius and tuberculum olfactorium as well as size decrease to a different degree of the other olfactory centers. Compared with this all limbic structures showed clearly decrease in size. In totally they were reduced to 9.6% from Norway to laboratory rats. The highest reduction values were found in the adjoining structures of the archicortex and the schizocortex. Equivalent reduction intensities of 10.2% could be established for the main centers of the hippocampus formation (cornuammonis; fascia dentata). The different rates of reduction intensity were interpreted as due to the special environmental changes caused by domestication. They seem to be related to behavioral changes.

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