Motor incoordination, intracranial fat bodies, and breeding strategy in Crested ducks (Anas platyrhynchos f.d.).

Some Crested ducks (CR) are burdened with an intracranial fat body that, depending on the size and location, may lead to varying degrees of motor incoordination. A behavioral test is proposed that helps to identify those CR individuals bearing the problematical fat body. The test consists of putting the ducks on their backs and measuring the time required to right themselves. This was repeated 13 times per animal, and means were calculated. The minimum time required was 0.5 s, and the maximum was 62.6 s. Individuals that show motor incoordination need more time than ducks without such problems (14.3 s in contrast to 1.2 s) and exhibit a larger intracranial fat body. Ducks used for breeding should require no more than approximately 1 to 2 s to right themselves. In an allometric comparison with 3 other domestic duck breeds, CR show a significantly smaller brain; specifically, the cerebellum, tegmentum, apicale hyperpallium, and olfactory bulb are reduced. The relationship between fat body and these structures was discussed.

[Intracranial fat bodies and their potential effect on brain composition and behaviour in domestic ducks with feather crests (3 case studies)]. / Intrakraniale fettkörper und ihre potentiellen Auswirkungen auf Hirnbau und Verhalten bei hauben- tragenden Hausenten (3 Fallstudien).

Intracranial fat tissue was found in the brains of three crested ducks. The three ducks differed in the size of their crest and in the volume and the location of the fat body within their brains. The duck with the large crest showed a fat body which counts for 19 % of its brain volume. Due to this fat accumulation, brain structures, mainly the cerebellum, were moved laterally. This duck had serious problems in motor coordination. Fat body of the second duck with a middle sized crest was situated in neostriatum and constituted 0,6 % of total brain volume. Additionally this duck displayed an encephalocele. The last duck did show a small crest. Its fat body was found in the area of the tentorium cerebelli and made up 17 % of its brain volume. The later two ducks were not hampered behaviourally.

Brain size, brain composition and intracranial fat bodies in a population of free-living crested ducks ('Hochbrutflugenten').

(1) Brain sizes and brain structure volumes of crested specimens from a population of 'Hochbrutflugenten' ducks (HBTcr), living under seminatural conditions, were compared with those of other duck breeds, among them the breed 'Landente' with the same morphological trait, the crest (LEcr). (2) Brains of both HBTcr and LEcr were larger than expected from an allometric comparison with uncrested breeds. (3) Fat bodies invading the skull were observed in both breeds. (4) In LEcr they could be voluminous; after subtraction of their volume from the brain volume, most brain structures measured were allometrically of the same size as in uncrested breeds. (5) In contrast, HBTcr had small fat bodies, and most of their brain structures were allometrically larger than those of the other breeds. (6) A small fat body in the skull does not appear to influence the survival of HBTcr under seminatural conditions.

Brain alterations in crested versus non-crested breeds of domestic ducks (Anas platyrhynchos f.d.).

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.

Eye muscle nerves nuclear size in a breed of domestic rabbits with floppy ears.

In many wild species there is a correlation between the capacity for directional hearing and directional seeing, which is associated with the mobility of the eye balls. Among the breeds of domestic rabbits, there are some with pendulous, floppy external ears (e.g., Englische Widder, EW) that might limit directional hearing. The size of the brain stem nuclei in EWs has been determined and compared to rabbits with upright ears. In EW, the oculomotor nuclei are relatively larger than in the other breeds. Possibly, this indicates a compensation of a loss in directional hearing ability achieved through greater mobility of the eyes. At the same time, a variability of brain composition between the breeds, which is an intraspecific variability, is obvious.

Allometric comparison of the brain and brain structures in the white crested polish chicken with uncrested domestic chicken breeds.

The feather crest on the head of the White Crested Polish Chicken covers a bony protuberance, a skull modification typical of crested chickens. The telencephalon is displaced into this protuberance, giving the brain the shape of an hour-glass. Allometric comparison (i.e., consideration of the influence of body weight on brain size) shows that the brain is relatively larger in crested chickens. This enlargement is partly due to enlarged ventricles, which are observed in some individuals. Among the brain structures measured, the tegmentum, cerebellum, tectum, paleostriatum, hippocampus, septum and olfactory bulb are not significantly larger in White Crested Polish chickens in comparison to those structures in seven uncrested chicken breeds; the optic tract, diencephalon, telencephalon, accessory hyperstriatum, dorsal and ventral hyperstriatum, and neostriatum, however, are significantly enlarged in this breed.

Volumetric comparison of auditory brain nuclei in ear-tufted Araucanas with those in other chicken breeds.

Domestic chickens of the breed Araucana have ear-tufts, which affect the structure of the ear canal. Volumes of auditory brainstem nuclei were measured in three chicken breeds in order to evaluate whether the characteristics described for ear-tufted individuals of the Araucana chicken breed (alterations in the outer and middle ear anatomy) are associated with changes in the size of the relevant auditory nuclei. Allometric comparison reveals no size reductions of the angular, laminar and superior olivary nuclei in Araucanas, compared to Japanese Bantams and Brown Leghorns, but a slight increase in the size of the magnocellular nucleus.

The size of the middle temporal area in primates.

The increase in the size of the lateral geniculate body and the primary visual cortex from prosimians to apes and man reflects at an anatomical level the importance of the visual system in primates. In the prestriate cortex visual modalities are processed separately in specialized pathways and areas. This arrangement facilitates the allometric analysis of cortical areas subserving defined visual modalities. Its heavy myelination makes the middle temporal area, a visual cortical field specialized for the detection of moving stimuli, an easily detectable and reliably delineable area in histological sections. The size and position of the middle temporal area can therefore be compared between species, in order to collect quantitative data about the development of a defined visual submodality during primate evolution. The volume of the middle temporal area was measured in 27 primate species. Allometric comparisons show that the middle temporal area is larger in simians than in most prosimians. In Callitrichidae, both the middle temporal area and the striate cortex are well developed. In cebids and cercopithecids, however, the sizes of the middle temporal area and primary visual cortex show divergent trends. Whereas the striate cortex is still enlarging, the size of the middle temporal area is reduced as compared to callitrichids. Previous studies have revealed a close correlation between area striata and neocortex sizes, as well as area striata and lateral geniculate sizes. Such a close correlation does not exist for the middle temporal area versus neocortex or area striata. Therefore, the size of a visual structure serving a special submodality (e.g., the middle temporal area for the detection of moving stimuli) may develop in a species relatively independently from the lateral geniculate and primary visual cortex sizes.

Brain structure volumes in the mole rat, Spalax ehrenbergi (Spalacidae, Rodentia) in comparison to the rat and subterrestrial insectivores.

Natural blindness and a subterranean, digging mode of life demand peculiar adaptations of the central nervous system in the mole rat Spalax ehrenbergi, which are the focus of this quantitative investigation. Volumes of 25 brain structures in Spalax were evaluated allometrically, using the least encephalized mammalian species, the Madagassian hedgehog-like tenrecs (Tenrecinae) as a reference base, and their sizes compared with those of the rat (as a more generalized representative of rodents) and of some subterranean Insectivora. The allometric approach reveals that Spalax has a larger brain than tenrecs and the rat. Within the brain, the neocortex and diencephalon are well developed, an observation also made in other mammalian species with a relatively high encephalization. An unique feature in Spalax is the enlargement of motor structures of the brain, such as the cerebellum (and cerebellar nuclei), and the striatum. Most conspicuous is the large size of the nucleus motorius nervi trigemini, reflecting the importance of masticatory muscles for the special digging technique, which demand an intense use of the teeth for loosening the soil.

Size of somatosensory cortex and of somatosensory thalamic nuclei of the naturally blind mole rat, Spalax ehrenbergi.

The hypothesis that the somatosensory system in the naturally blind subterranean rodent Spalax ehrenbergi (= mole rat) is enlarged was tested by measuring the volume of somatosensory cortex and somatosensory thalamic nuclei (Nuclei ventrales posteromedialis and posterolateralis). Electrophysiology and tracing were used to identify and delineate these areas. On average the somatosensory cortex is 1.7 times larger and the thalamic nuclei are 1.3 times larger in the blind mole rat than in the sighted laboratory rat if different body weights are taken into consideration. This confirms the demands of a life underground where it seems touch would replace vision. The data reveal a remarkable brain plasticity among mammals under natural conditions.

Volumetric comparison of hippocampal regions in 44 primate species.

Volumes of retrocommissural hippocampal regions (Subiculum, CA 1, CA 2, CA 3, hilus region, and fascia dentata) were measured using serial sections of 44 species of prosimian and simian brains, including man. The volumes were compared allometrically with those of the least encephalized eutherian mammals, the madagassian tenrecs (Insectivora, Tenrecinae; 4 species). The retrocommissural hippocampus is 2.9 times larger in prosimians, 2.4 times in non-human simians, and 4.1 times in man. The different hippocampal regions do not enlarge uniformly to the same degree as the total hippocampus. The regions can be grouped into three categories, according to the degrees to which they enlarge in primates: a) Structures with the greatest degree of enlargement are the subiculum and the field CA 1. b) An enlargement similar to that of the total retrocommissural hippocampus is seen for the hilus region. c) No or only a slight enlargement as compared to their sizes in tenrecs is observed for the hippocampal fields CA 2, CA 3, and the fascia dentata.

Quantitative development of brain and brain structures in birds (galliformes and passeriformes) compared to that in mammals (insectivores and primates).

The brain weight and brain structure volumes of galliform and passeriform birds were calculated and related to body weight. The total brains and 14 brain regions were investigated in order to calculate factors by which these structures in passeriforms exceed those in galliforms in size. The larger passeriform brains have larger telencephala, especially ventral hyperstriata and neostriata. The enlargement of total brain and telencephalon resembles that in primates, compared to insectivores, within mammals. The enlargement of the ventral hyperstriata + neostriata in passeriforms is fundamentally similar to that of the isocortex in mammals: it reflects an expansion of multimodal integrational capacities, as the ventral hyperstriatum and neostriatum are occupied exclusively or primarily by multimodal integrational areas as is the isocortex.

The megachiropteran pineal organ: a comparative morphological and volumetric investigation with special emphasis on the remarkably large pineal of Dobsonia praedatrix.

This investigation is based upon the pineal organs of 92 specimens of 36 species of the family Pteropodidae (Mammalia, Chiroptera). The size of the megachiropteran pineal correlates well with body size (r = 0.864), confirming the former conclusions that generally larger bodied bats have larger pineals. The range of the pineal size index in 36 megachiropteran species is from 33 to 4393. In most species the pineal organs are small, deeply recessed under the cerebral hemispheres and of Type A (except in Dobsonia and Pteropus, where they are of Type alpha beta C and AB, respectively). Morphological and volumetric data gathered from serially sectioned brains include body and brain weights, pineal type, dimensions, volume and size index for each species. There are distinct dorsal and ventral subdivisions of the pineal in some species and a clear separation of pineal parenchyma into cortical and medullary regions in others. In several species where overlying ependyma is lacking pinealocyte clusters communicate freely with the CSF. Groups of intrapineal neurons are noted in the connective tissue beside blood vessels. The habenular commissure shows much interspecific variation in its course through the pineal. Detailed examination of pineal-brain relationships clearly suggests that, due to the generally deep location of the pineal in relation to cerebral hemispheres, pinealectomies in the species studied may be extremely difficult, it not entirely impossible. The absolutely and relatively largest pineal organ among bats, and relatively perhaps among all vertebrates, has been discovered in the New Guinean naked-backed bat, Dobsonia praedatrix, with pineal size index of 4393, and a volume of 16.3447 mm3, which is 0.56% of the brain. This alpha beta C-type, mushroom-shaped, solid and compact pineal organ measures 5.33 x 4.51 mm. The cortical and medullary parenchyma are divided into lobes by large calibre blood vessels along which numerous intrapineal neurons are observed. A smaller but similarly shaped pineal is noted in the other three Dobsonia. Data on the largest known pineals in ratitae birds, seals and walruses have been compared with that of D. praedatrix and the human pineal. This study supports the hypothesis that pineal development may reflect dependence on habitat and possibly other related factors.

Comparison of brain structure volumes in Insectivora and primates. IX. Trigeminal complex.

Volumes of the trigeminal complex (TR) were measured in 30 species of Insectivora, 3 species of Scandentia, 18 species of prosimians, 26 species of non-human simians and in man. The relative size showed a definite tendency to decrease from 159 in Insectivora to 56 in simians (expressed as size indices). The difference in the development of the TR between Insectivora and Primates is explained by differences in the role of their oro-facial region in exploratory behavior. The largest size was found in semiaquatic Insectivora (average 283). In semiaquatic forms, the reduction of the olfactory centers is compensated by an increase in TR size. The extremely long vibrissae innervated by the trigeminal nerve seem to have a teletactile function in detecting vibrations in the water produced by potential prey.

Comparison of brain structure volumes in insectivora and primates. VIII. Vestibular complex.

Volumes of the vestibular complex (VC) and its four main components (medial, inferior, lateral and superior nuclei; VM, VI, VL and VS) were measured in 28 species of Insectivora, 3 species of Scandentia, 18 species of prosimians, 26 species of non-human simians and in man. The relative size showed a definite tendency to increase 2-4.5 times from Insectivora through simians (expressed by size indices). The highest increase was found in VS, the lowest in VI and, in Pongidae and man, also in VL. The differences are discussed with respect to differences in the locomotory behavior of the various taxonomic groups and to differences in the fiber connections and thus different functions of the various nuclei. Species which exploit a 3-dimensional environment and execute fast and complicated head and body movements have a larger VC than closely related species confined to the ground or which are less skilled leapers. The great increase of the VS may be related to the predominant role of vision in primates, particularly in simians.

Allometric comparison of brain weight and brain structure volumes in different breeds of the domestic pigeon, Columba livia f.d. (fantails, homing pigeons, strassers).

In three breeds of domestic pigeons (fantails, homing pigeons, and strassers) the volumes of fresh, i.e. unfixed tissue of 14 brain structures were determined (telencephalon, diencephalon, nervus opticus, tectum, cerebellum, tegmentum and hyperstriatum accessorium, hyperstriatum ventrale, neostriatum, paleostriatum, hippocampus, septum, regio praepiriformis, bulbus olfactorius). Allometric comparisons that take into account differences in body weight and size were made among these three breeds. The tectum, hippocampus, paleostriatum and especially the neostriatum and olfactory bulb are remarkably larger in homing pigeons. These data are discussed in a functional context, in which the homing ability of homing pigeons is considered.

Comparison of brain structure volumes in Insectivora and primates. VII. Amygdaloid components.

Volumes of the amygdaloid complex (AMY) and some subdivisions were measured in 2 species of Macroscelidea, 39 species of Insectivora, 3 species of Scandentia, 18 species of prosimians, 26 species of simians and man. Changes in the relative size from Insectivora through man (expressed by size indices) showed a definite tendency to increase in the cortico-basolateral subdivision (LAM) and more or less constant relations in the centromedial subdivision (MAM), except for the nucleus tractus olfactorii lateralis (NTO), which becomes distinctly reduced. The reduction of NTO is even stronger than that of the main olfactory bulb (BOL), which in simians and man is small but distinct, whereas NTO is hardly recognizable in most of these forms. In the LAM group the size increase of the large-celled part of the basal nucleus (MCB) is less than that of the small-celled components (including the lateral nucleus). The differences between LAM and MAM groups are discussed with regard to the predominant fiber connections, which in MAM are stronger with conservative brains parts (brainstem), and in LAM with progressive brain parts (e.g. neocortex).

Comparison of brain structure volumes in Insectivora and primates. VI. Paleocortical components.

Volumes of the main structures of the 'paleocortical complex' were measured in 2 species of Macroscelidea, 39 species of Insectivora, 3 species of Scandentia, 18 species of prosimians, 26 species of nonhuman simians and man. Changes in the relative size from Insectivora through man (expressed by size indices) showed a definite tendency to decrease in the lateral olfactory tract (TRL), its nucleus (NTO), and in the olfactory cortices (RB, PRPI, TOL) and to increase in the anterior commissure (COA) and substantia innominata (SIN). The reduction in the olfactory cortices is strongest for the retrobulbar region (RB, = anterior olfactory nucleus in Anglo-American terminology), and least for the olfactory tubercle (TOL). In prosimians, the reduction clearly parallels that of the main olfactory bulb (BOL); in simians and especially in man, the indices of PRPI and TOL are clearly larger than those of BOL. Possible reasons for these growing deviations were discussed: (1) increasing difficulties in clearly homologizing and delineating the olfactory cortices in the microsmatic simians, and (2) non-olfactory functional influences.

The pineal organ of bats: a comparative morphological and volumetric investigation.

Bats are seasonal breeders and roost under a wide range of lighting conditions, from broad daylight to the total darkness of subterranean passageways and caves. Some are true hibernators. These characteristics and the paucity of information on their pineal organ prompted this investigation, which is based upon the pineals of 191 specimens of 88 species and 12 families of bats. Comparative morphological and volumetric observations have been made on serially sectioned brains of each species. Data include brain and body weights, mean pineal dimensions and volume, a computed pineal size index for each species and salient characteristics and relations of the pineal organ of the 12 chiropteran families. Generally speaking, despite some exceptions, larger bodied bats also have larger pineals. Bats of the microchiropteran families such as the Emballonuridae, Megadermatidae, Rhinolophidae, Hipposideridae, and a few vespertilionids (for example, Myotis adversus) and molossids (for example, Tadarida mops), have very large pineal organs, of which many reach the brain surface. All of these bat families inhabit dark caves. By contrast, in megachiropterans (pteropodids) which roost in broad daylight, the pineal lies deeply recessed and covered by the cerebral hemispheres. It is postulated that in general the superficial and deep location of pineal in micro- and megachiropteran species respectively may be a consequence of several factors, such as their habitat and their neocortical and cerebellar development. A system of classifying chiropteran pineal organs has been presented; in most species they are either of Type A or of Type AB. Most species have non-uniformly distributed parenchymal cells arranged in cords or clusters. In some species (for example, Rhinolopus trifoliatus and R. luctus) morphologically distinct dorsal and ventral divisions are observed. Pineal vascularity appears to be related to its size. Intrapineal neurons are rare and, when present, are associated with blood vessels. Epithelium-lined cavities are seen in the pineals of several species, while in a few others, the pineal is either absent or consists of a few scattered cells. Variable relationships between the pineal and the habenular commissure suggest that they may be unrelated functionally.