1. An experiment was conducted to test the directionality, scaling and reversibility of phenotypic responses of the gastrointestinal tract (GIT) of adult ganders to rice husk (RH) diluted dietary switching. 2. A total of 96 140-d-old ganders were acclimatised to a basal diet for 2 weeks. The birds were randomly assigned to 4 treatments. On d 1, diets in the experimental groups were switched from the basal diet to diets which contained 200, 400 or 600 g/kg RH by mass, with no RH in the basal diet. After 21 d, the diet of all the experimental birds was switched back to the basal diet until d 42. 3. Increasing RH content significantly increased feed intake, and a decreased trend appeared after diet-switching. The weights of geese fed on the 600 g/kg RH diet for 21 d reduced, and were significantly less than those of the other three groups, while body weights (BW) of the geese in all groups increased after diet-switching back to the basal diet. At d 21, significantly heavier relative weights of proventriculus, gizzard and all gut components, except duodenum, were observed in birds fed on a 600 g/kg RH diet, and significantly heavier relative weights of gizzard were observed in birds given a 400 g/kg RH diet. Thickness of the two gastric walls, gizzard length and all gut components lengths increased significantly in birds given a 600 g/kg RH diet compared with the other three groups. At d 42, no significant differences were noted in the relative weights or lengths of GIT, except for the caeca, which were significantly heavier in birds fed on 600 g/kg RH diet. 4. The results of the experiment were in accordance with the predictions of the hypothesis that there is matching between loads and capacities. The observed phenotypic responses were directional and scaled to the demands.

A key question in evolutionary genetics is whether shared genetic mechanisms underlie the independent evolution of similar phenotypes across phylogenetically divergent lineages. Here we show that in two classic examples of melanic plumage polymorphisms in birds, lesser snow geese (Anser c. caerulescens) and arctic skuas (Stercorarius parasiticus), melanism is perfectly associated with variation in the melanocortin-1 receptor (MC1R) gene. In both species, the degree of melanism correlates with the number of copies of variant MC1R alleles. Phylogenetic reconstructions of variant MC1R alleles in geese and skuas show that melanism is a derived trait that evolved in the Pleistocene.

In the cat and goose, studies have been undertaken to determine the ultrastructure of airway epithelia, the concentration and distribution of the secretory cells which produce respiratory tract mucus, and the histochemistry of mucins located within cells and on their luminal surfaces. By electron microscopy all the 11 cell types so far described can be found in the airways of the cat but not the goose. Both goblet cells and submucosal glands are abundant in the cat whereas the trachea of goose lacks the latter, having instead abundant goblet cells many of which form 'intraepithelial glands'. Histochemically, the goblet cells of the cat and goose are similar in that they contain mucins with a predominance of sulphate esters. A surface mucosubstance can be demonstrated which, histochemically, is similar to that described in dog and man. Interestingly, this surface layer may be sloughed in response to an inhaled irritant such as ammonia and thereby contribute to the respiratory tract mucus recovered experimentally. Incorporation into macromolecules of radioactively labelled mucin precursors is assessed by autoradiography of tissue sections, and preliminary results of experiments designed to test the response of mucus-secreting cells to airway irritation and the parasympathomimetic drug, pilocarpine, are also presented.

The purpose of this study was to determine the location of neuronal cell bodies with projections to the cervical or lumbar spinal cord in the adult duck and goose. Bilateral or unilateral injections (5-10 microliter) of the retrograde tracer dye True Blue (TB:5%) were made into the high cervical or high lumbar levels of the spinal cord. Similar results were obtained in both species. First, we found no evidence of retrogradely labelled cells in the telencephalon. In the brainstem, the distribution of TB cells was similar to those previously reported for the pigeon; however, the present study now demonstrates that some of these descending pathways project as far as the lumbar cord. We also discovered that there is a topographical representation of spinal projecting neurons within the avian medullary-pontine reticular formation.

1. Metabolic functions, fiber composition and, in some cases, mitochondrial morphology have been investigated in the pectoralis major and sartorius of the goose, quail, pheasant, guinea-hen, broiler chicken and laying hen. 2. In the pectoralis only two types of fibers, red and white twitch fibers, are found in all birds studied except in the quail, where a third twitch fiber also occurs. Red fibers form the main part in the quail and goose, white fibers in the rest. In the sartorius at least three types of fibers, two twitch and one tonus are found in all birds except in the guinea-hen where only two fibers can be found. 3. The metabolic pattern of the muscles, based on determination of specific activities of metabolic key enzymes, varies greatly among the birds. Three groups can be discerned from the ratio between aerobic and anaerobic activities or between fatty acid oxidation and carbohydrate metabolism. The metabolic patterns are reflected in the fiber combinations of the muscles. 4. The size and number of the mitochondria vary among different animals and different fiber types. The metabolism of red and white fibers is discussed.

The lungs of 5 wild mallard ducks (Anas platyrhynchos) and 5 feral graylag geese (Anser anser) of mean body weight 1.04 and 3.84 kg, respectively, were fixed in situ by intratracheal infusion of 2.3% glutaraldehyde, pH 7.4 and total osmolarity 350 mOsm, at a pressure head of 25 cm, and analysed by standard morphometric techniques. The following data apply to both lungs together, in the fixed state, the first value relating to Anas and the second to Anser in each case: lung volume, 30.4 and 95.3 cm3; volume of exchange tissue, 12.32 and 38.50 cm3; volume of capillary blood, 4.06 and 12.49 cm3; surface area of blood-gas (tissue) barrier per unit body weight, 28.56 and 23.10 cm2/g; surface area of the blood-gas (tissue) barrier per unit volume of lung, 977 and 932 cm2/cm3; surface area of blood-gas (tissue) barrier per unit volume of exchange tissue, 241 and 230 mm2/mm3; harmonic mean thickness of tissue barrier, 0.133 and 0.118 microns; arithmetic mean thickness of tissue barrier, 0.903 and 0.887 microns; harmonic mean thickness of plasma layer, 0.369 and 0.322 microns; mean total morphometric pulmonary diffusing capacity per unit body weight, 3.85 and 3.59 ml O2/min/mm Hg/kg. These morphometric parameters of Anas and Anser are compared with those reported in the literature for the domestic fowl (Gallus gallus), the budgerigar (Melopsittacus undulatus), the house sparrow (Passer domesticus), and the violet-eared hummingbird (Colibri coruscans). The lungs of these six avian species show progressively advancing adaptations, from Gallus, through Anser, Anas, Melopsittacus and Passer, to Colibri, which appear to be consistent with the energetic characteristics of these birds.

The segmentum accelerans in geese is a constriction in the caudal end of the primary bronchus. Experimental evidence suggests that this part of the airway functions as an inspiratory aerodynamic valve, accelerating the incoming airstream past the ventrobronchial openings. The luminal diameter of the segmentum accelerans dilates in the presence of elevated CO2 levels, probably through relaxation of smooth muscle. Physiological control of the segmentum accelerans may permit inspiratory aerodynamic valving to be maintained throughout a wide range of ventilatory flows.

Previous studies of cecal sugar and amino acid transport in the domestic chicken led to a widely held generalization that the avian cecum is unimportant as a site of nutrient transport. In fact, we found that the uptake capacity of the cecum for hexose sugars and amino acids is substantial in some species of birds. Cecal transport of glucose was measurable in all five study species (Canada goose, sage grouse, domestic chicken, red-necked phalarope, and rock dove), approached or exceeded intestinal levels in the grouse and phalarope, and accounted for between 0.1%(rock dove) and 49%(sage grouse) of the whole gut's integrated uptake capacity. Proline uptake averaged higher in the proximal portion of the cecum than in any region of the small intestine for all species but the goose. The ceca contributed between 2%(rock dove) and 25%(sage grouse) of the gut's integrated uptake capacity for proline. Similar ranges were found for fructose, lysine, leucine, and aspartate. Future studies should be undertaken to search for phylogenetic and ecological correlates of the interspecific variation in cecal transport and to determine how nutrient transport integrates with other functions of the avian cecum.

The peptidergic melanin-concentrating hormone (MCH) system was investigated by immunocytochemistry in several birds. MCH perikarya were found in the periventricular hypothalamic nucleus near the paraventricular organ and in the lateral hypothalamic areas. Immunoreactive fibers were very abundant in the ventral pallidum, in the nucleus of the stria terminalis, and in the septum/diagonal band complex, where immunoreactive pericellular nets were prominent. Many fibers innervated the whole preoptic area, the lateral hypothalamic area, and the infundibular region. Some fibers also reached the dorsal thalamus and the epithalamus. The median eminence contained only sparse projections, and the posterior pituitary was not labeled. Thus, in birds, a neurohormonal role for MCH is not likely. Immunoreactive fibers were observed in other regions, such as the intercollicular nucleus, stratum griseum periventriculare (mesencephalic tectum), central gray, nigral complex (especially the ventral tegmental area), reticular areas, and raphe nuclei. Although no physiological investigation concerning the role of MCH has been performed in birds, the distribution patterns of the immunoreactive perikarya and fibers observed suggest that MCH may be involved in functions similar to those described in rats. In particular, the projections to parts of the limbic system (ventropallidal ganglia, septal complex, hypothalamus, dorsal thalamus, and epithalamus) and to structures concerned with visceral and other sensory information integration suggest that MCH acts as a neuromodulator involved in a wide variety of physiological and behavioral adaptations (arousal) with regard to feeding, drinking, and reproduction.