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In 80 domestic chickens from 8 breeds, the volumes of 12 brain parts were identified as dimensions in a cluster analysis. Based on Euclidean metrics and the Ward algorithm at least 2 groups were found that are congruent with the breeds ‘White Crested Polish chicken’ and ‘Breda’, although the breed identity was not a variable used in the cluster analysis. Domestication is interpreted as evolution which includes the possibility of speciation. It is hypothesized that White Crested Polish chickens and Bredas are becoming new species in terms of a biospecies concept.

A comparison of brain size and brain composition was made between two uncrested duck breeds and Crested Ducks (CR) and between CR individuals that do possess crests and those that do not have the crest. Domestic ducks of the breed CR have allometrically larger brains than uncrested duck breeds. The crest inserts on a cushion of fat and connective tissue that is partly nourished by brain vessels via small holes in the skull. Through these holes, fat tissue may invade the brain cavity. Because the fat accumulations are sometimes hidden deep between the telencephalon, tectum, and cerebellum, they may be invisible macroscopically and, thus, give the impression of a large brain. The size of the crest, however, is not strictly correlated with fat accumulations in the brain, because 2 among 10 specimens of CR showed no fat body at all, and the investigation of 10 uncrested CR (ducks from the same genetic stock, but without the crests) also revealed fat accumulations in 6 specimens. After subtraction of the volume of the fat body, the brain volume of CR (crested and uncrested) was of equal size to that of "Hochbrutflugenten" and Pommeranian ducks, as was the volumes of most brain structures measured. Significantly smaller in CR were the olfactory bulbs, the prepiriform area, and the cerebellum, which was always situated in close proximity to the fat body in CR.

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Essential polyunsaturated fatty acids (PUFAs) have been recognized as a crucial factor that determines the trophic transfer efficiency in plankton communities. As many animals cannot synthesize the classes of ω3‐ and ω6‐PUFAs, the dietary availability of these PUFAs can constrain the fitness of freshwater zooplankton such as Daphnia spp. In particular, eicosapentaenoic acid (EPA, 20:5ω3) is considered to be a crucial determinant of the transfer of biomass at the freshwater plant‐herbivore interface. In contrast to ω3‐PUFAs, the group of ω6‐PUFAs has previously been considered to be of less ecological relevance, although the potential role of the ω6‐PUFA arachidonic acid (ARA, 20:4ω6) remains controversial. To investigate its potential role, we conducted dose‐response growth experiments with two Daphnia species, D. pulex and D. magna, supplemented with EPA or ARA, which allowed us to calculate EPA and ARA saturation thresholds for growth and reproduction of both Daphnia species. Our results provide evidence that not only the availability of ω3‐PUFAs, but also the availability of a ω6‐PUFA, namely ARA, can limit both the growth and reproduction of Daphnia spp. to an equal extent. The saturation thresholds for growth and reproduction were consistently, but not significantly, higher for EPA than for ARA in both Daphnia species. As shifts in phytoplankton community composition might result in environmental fluctuations in the dietary availability of ω3‐ and ω6‐PUFAs, our findings present a significant step in understanding the consequences of the ongoing global biodiversity loss for trophic transfer efficiency at the phytoplankton‐zooplankton interface.

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The pupil in the eye of adult cattle is oval under contraction with the long axis nearly horizontal. Based on simple optophysical facts it is hypothesised that visual perception in such eyes is different for stimuli with vertically-separated details rather than stimuli with horizontally-separated details. This hypothesis was tested with three adult dairy bulls using an operant conditioning technique. The bulls had to discriminate a solid white line from broken white lines with decreasing interspaces. They solved this task better when the stimuli were presented vertically rather than horizontally. This result is discussed in terms of visual acuity and related to the topographical anatomy of the eye, particularly the pupil.

No abstract