Jaap Dubbeldam: professor of neurobehavioural morphology.
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Anatomy↗
Biomedical subjects
G A Zweers
Publications and source records attributed to G A Zweers.
The variety of explanations of living forms and structures.
Over the last decades the image of vertebrate morphology has become at some places chaotic and even opportunistic, which seems to be due to the lack of appraisal or recognition of the leading concepts of the field. This paper analyses the changes in morphology, and shows that these changes have enriched research aims and that the discipline has a clear methodological and philosophical coherence. The situation in morphology is analysed from a semi-historical and review-like point of view to see what aspect is aimed at for explanation, and what types of explanation are used. A preliminary conclusion is reached that the animal form still has to be explained, and that the types of explanation for living form and structure can be divided into three main categories: (1) a category of typological explanation: (2) a category of functional explanation, including a specific constructional explanation; and (3) a category of causal explanation. Each of these categories has a static and a dynamic aspect. The dynamic aspect includes an explanation connected to life time (the system dynamic and morphogenetic explanation) and an explanation connected to evolutionary time (the historical explanation). These categories are used for structure at the molecular up to and including the organismic level of organization. The main challenge for the future is to integrate these different categories of form-explanation and determine their relative dominance when a theory of biology, that is of biological form and activity, is developed.
Animals↗
Cervical kinematics during drinking in developing chickens.
Development of head neck motion patterns is studied in drinking chickens to examine (1) general motion principles, (2) ontogenetic changes in these patterns, and (3) whether pattern changes are due to scaling effects during growth. Behavioral patterns are analyzed by high speed filming, radiography, and calculation of rotation patterns for each joint during all movement patterns. Flexibility and variability are great, but representative kinematic patterns are selected for immersion, upstroke, and tip-up phases. Five principles were found that control cervical motion. Two principles maximize rotation efficiency: the geometric and lever arm principles. Two trajectory compensating principles occur; one controls compensation for overflexion, and the other corrects curved into straight trajectories of head motion. One principle occurs that minimizes rotation force if large forces tend to develop in one joint. This principle results in a characteristic cervical motion pattern ("bike chain" pattern). There are three developmental periods: (1) hatchlings (2) chickens 1 to 4 weeks old (1-4W), and (3) older than 4 weeks. Each period is characterized by different kinematic patterns. In 1-4W chicks, the rotation force is minimized. In older stages, the cervical joints rotate according to geometric and lever arm principles. The totally different motion pattern in hatchlings results from a different behavioral reaction to water and the influence of large centrifugal forces. Transitions in cervical motion patterns are connected to effects of scaling, primarily changes in head and body weights. Changes in motion patterns are not related to changes in anatomical characters such as flexion extremes and relative length of each vertebra since these are similar in all stages.
Analysis of Variance↗
Integration of pecking, filter feeding and drinking mechanisms in waterfowl.
This paper is one of several contributions in a series, illustrating the application of a specific deductive methodology to explain diversity of form. The methodology facilitates the explanation of feeding morphologies in various ducks as a transformation of the mallard's feeding design maximized for specific proportions of performance that are contributed by pecking and filter feeding mechanisms. The earlier described anatomy and formal analyses of the three mechanisms in the mallard served as the initial conditions used in simulation models. Four elements of the feeding system were chosen that play a major role in all three mechanisms. For each element, the main parameter was selected: storage capacity of the rostral mouth cavity, transport capacity of the rostral mouth tube, storage capacity of the caudal mouth cavity and transport capacity of the caudal mouth tube. The boundary conditions for the simulation were determined from internal organismic constraints. The total food uptake of the mallard was regarded as the function to be maximized. This 'object' function is the summation of the food uptake by one second of pecking and one second of filter feeding. The drinking mechanism was shown not to interfere, since that mechanism operates sufficiently whenever the pumping mechanism works properly. The 'object' function, made up by the pecking and filter feeding performances was graphed. From these graphs a morphospace was developed: the region within which modifications of the mouth design are feasible. This procedure allowed examination of the general hypothesis that different modifications of one design for a complex multi-role system are explainable from differences in proportions of the functional performance contributed by each of the roles. Two predictions were evaluated more specifically: 1) If filter feeding performance must increase for a specific change in total food uptake, the volume of the rostral mouth cavity must increase; this requires widening and lengthening of the rostral maxillar portion and also a phase shift in jaw and lingual motion patterns, increasing the stroke volume. 2) If pecking performance must increase, the transport capacity of the rostral mouth tube must increase; this requires shortening of the maxillar mid portion. These two predictions regarding change in mouth morphology were borne out by shovelers and tufted ducks, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)
Animals↗
Avian cranio-cervical systems. Part I: Anatomy of the cervical column in the chicken (Gallus gallus L.).
The osteology, arthrology and myology of the cervical column in the chicken (Gallus gallus L.) are described. The description serves as a basis for comparative and mechanical analysis of the development of stereotypic behavioural patterns. The section on osteology describes about 20 occipital elements and over 50 vertebral elements, and also informs about size differences of homologous vertebral elements. A series of suggestions concerning terminological questions refers to earlier nomenclatures. The section on arthrology comprises descriptions of intra-, capsular and extra-capsular ligaments, as well as a description of the boundaries of the work-envelope of the cervical column from an X-ray analysis. The section on myology comprises a detailed description of the occipito-cervical, ventral and dorsal subsystems of the cervical column. Special attention is given to often incompletely described muscles like the medial part of the musculus flexor colli, the musculus longus colli ventralis, the medial part of the musculus longus colli dorsalis pars caudalis.
Animals↗
Avian cranio-cervical systems. Part II: Arthrology of the occipito-cervical system in the mallard (Anas platyrhynchos L.).
The arthrology of the muscle-bone apparatus of the occipito-cervical system in the mallard (Anas platyrhynchos L.) was analysed by dissection and from histological microsections of an in toto embedded occipito-atlanto-axial apparatus. The description is primarily concerned with ligaments, membranes and fibrocartilages which were so far incompletely analysed. Several newly described elements such as the ligamentum atlantooccipitale laterale and the ligamentum ventromediale atlantoaxiale were added, as well as additional aspects such as the accurately described attachments, course and shape of most of the studied elements.
Animals↗
Avian cranio-cervical systems. Part III: Robot kinematics for cervical systems.
A 2D-model for the kinematics of the cranio-cervical system is developed from algorithms applied for robot kinematics. The model is proposed for avian cranio-cervical systems. Three main problems were to be solved. The problem of underdetermination in an open multi-element kinematic chain, which develops because only kinematics were included, is solved by the application of two approximations for economic motion. The straight-line approximation for the course of the bill tips and the least-motion approximation for all articulations are both assumed to occur in selected phases of pecking and drinking behaviour. The problem that internal constraints and constraints resulting from demands for proper functioning may be operating is solved by incorporating the measured maximal dorsal and ventral flexion of each joint, and also both the target location of the bill tips and the target orientation of head and beak. The third problem, viz. how to handle variations in initial conditions, which developed from the relatively independent working locomotory part, is solved by standardizing the foot-food distance in the experiments, and further by running the simulations for the locomotory components over the trajectories they cover in reality, rather than to allow them to move over their full work-envelope. The model is highly adaptable to changes in the number of bars involved, in bar lengths, in work-envelopes, and in motion patterns. The predicted patterns were tested against combined film- and radiographic analyses. The comparisons lead to some general conclusions. The economy principles tested appear to be confirmed from the observations. Also, the fixed-target orientation approximation seems to be confirmed while the locomotory components clearly operate primarily under different constraints.
Animals↗
Greek classicism in living structure? Some deductive pathways in animal morphology.
Classical temples in ancient Greece show two deterministic illusionistic principles of architecture, which govern their functional design: geometric proportionalism and a set of illusion-strengthening rules in the proportionalism's "stochastic margin". Animal morphology, in its mechanistic-deductive revival, applies just one architectural principle, which is not always satisfactory. Whether a "Greek Classical" situation occurs in the architecture of living structure is to be investigated by extreme testing with deductive methods. Three deductive methods for explanation of living structure in animal morphology are proposed: the parts, the compromise, and the transformation deduction. The methods are based upon the systems concept for an organism, the flow chart for a functionalistic picture, and the network chart for a structuralistic picture, whereas the "optimal design" serves as the architectural principle for living structure. These methods show clearly the high explanatory power of deductive methods in morphology, but they also make one open end most explicit: neutral issues do exist. Full explanation of living structure asks for three entries: functional design within architectural and transformational constraints. The transformational constraint brings necessarily in a stochastic component: an at random variation being a sort of "free management space". This variation must be a variation from the deterministic principle of the optimal design, since any transformation requires space for plasticity in structure and action, and flexibility in role fulfilling. Nevertheless, finally the question comes up whether for animal structure a similar situation exists as in Greek Classical temples. This means that the at random variation, that is found when the optimal design is used to explain structure, comprises apart from a stochastic part also real deviations being yet another deterministic part. This deterministic part could be a set of rules that governs actualization in the "free management space".
Aging↗
[Functional anatomy of the feeding apparatus of the mallard (Anas platyrhynchos L.) structure, movement, electro-myography and electro-neurography (author's transl)].
A causal model for the functioning of the beakapparatus of the mallard during straining is formulated on a qualitative basis. The starting point for this model is an abstraction of the analysed structure of the muscle, bone, ligament system. The system was studied by electromyography and cinematography of the movements. It was attempted to quantify the model. Connections with neurography are shown.
Animals↗
Electromyography, movement and central nucleus activity analysis of the feeding apparatus and the trigeminal system of the mallard (Anas platyrhynchos l.).
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Animals↗