Bennett, D.C., Kojwang, D., Sullivan, T.M., Gray, D.A. & Hughes, M.R. 1998. Effect of saline acclimation on body fluid compartmentalisation in Pekin Ducks. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 378.

The compartmentalisation of body fluids was measured in Mallard Ducks, Anas platyrhynchos, drinking freshwater and after sequential acclimation to 300 mM and 400 mM NaCl. Total body water (TBW), extracellular fluid volume (ECFV) and plasma volume (PV) were measured using ³H₂O, ¹⁴C-polyethylene glycol, and Evans blue dye dilution techniques, respectively. As a result of acclimation to 300 mM NaCl, body mass (BM) was decreased 123 ± 23 g (4%; P = 0.04), but TBW was unaltered (P = 0.99). ECFV tended to be decreased (P = 0.09), but PV did not (P = 0.42). Calculated intracellular fluid volume (ICFV) was increased (P =0.04). Following further acclimation to 400 mM NaCl, there were additional decreases in BM (326 ± 97 g or 11% of initial of BM; (P = 0.102) and TBW 293 ± 61 ml (P = 0.054). ECFV was unchanged (P = 0.47); PV tended to be increased (P = 0.07); and ICFV to be decreased (P = 0.01). Our results suggest that when Mallard Ducks drink high, but tolerable salinities, they maintain TBW, but redistribute water from the interstitial fluid to the ICF compartment. When stressed beyond their ability to maintain TBW, they lose water from the ICF. This research was supported by NSERC (MRH).

Key words: total body water, extracellular fluid volume, plasma volume, intracellular fluid volume, interstitial fluid volume

 

Berkhoudt, H. 1998. Sensory adaptations in bills and forebrain of the Red Knot Calidris canutus. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 379.

Birds have underneath their horny rhamphothea arrays of mechanoreceptive sensory cells. In probing waders and filtering waterfowl these cells aggregate in complex bill tip organs that have consequences for the organisation of CNS-structures. Red Knots are calidrid sandpipers that probe for their food, bivalve molluscs, using "remote touch". Microanatomical analysis of the external billtips shows that only Herbst corpuscles are present in dermal invasions of numerous bony lacunae under the keratin. Sensory detection therefore has to be highly dynamic, since Herbst corpuscles are vibratory mechanoreceptors adapting rapidly in the millisecond-range. Once the food is in reach of the bill tips, other non-rapidly adapting mechanoreceptors, the Grandry corpuscles, take over the control of food processing. Located especially under the palatal spines, these organs control the "throw-and-catch" transport, the next phase in the sequence of mollusc-ingestion. Electrophysiological recordings in the second order trigeminal nucleus basalis located in the telencephalon show (1) that both rapidly and slowly adapting afferents are intermingling, but that (2) a discrete somatotopy of this type of tactile fovea exists.

Key words: mechanoreceptor, sandpiper, bill, forebrain, nucleus basalis

 

Brown, C.R. & Tinney, G.M. 1998. Thermal relations of Red-billed Quelea: Implications for extending distribution. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 379.

Red-billed Quelea Quelea quelea are serious pests of agricultural crops in Africa. In South Africa they appear to have recently expanded their distribution into regions where they were previously uncommon. This expansion has probably been facilitated by changes in agricultural practices, specifically the provision of livestock feedlots and water sources. We measured oxygen consumption, body temperature, thermal conductance (C) and evaporative water loss (EWL) of queleas between -10 and 45 °C to assess whether physiological limitations, especially temperature extremes, might limit their distribution. Individual queleas thermoregulated well at -10 °C which, combined with their communal roosting habit, suggests that low temperatures encountered in South Africa's agricultural regions are not a limitation. The thermal neutral zone of queleas was between 30 and 40 °C. Above 40 °C they became hyperthermic despite increases in C from 3.6 to 29 Jg^-1h^-1 °C and EWL from 5 to 21 mgg^-1h^-1. The latter represents a loss of 17% of their body weight in the course of a hot summer day. Consequently, although mean maximum summer temperatures in South Africa are such that few agricultural regions are immune to the potential spread of Red-billed Quelea, access to water and possibly ecological factors not assessed in this study (e.g. suitability of habitat and roosts), could potentially limit their expansion into some regions.

Key words: thermal physiology, range, agriculture, Quelea quelea

 

Chastel, O. Gaidet, N. & Kersten, M. 1998. Prolactin and parental effort in the House Sparrow. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 379.

Extensive comparative evidence suggests that prolactin mediates parental behaviour in birds. However few studies have examined the relationships between plasma level of circulating prolactin and parental effort. We manipulated brood sizes (-2 and +2 nestlings) of House Sparrows Passer domesticus to investigate if change in parental effort will lead to changes in plasma level of circulating prolactin. Chicks from enlarged brood were in poorer condition and were more likely to die during the fledging period. Females given extra chicks made more feeding visits than did females with reduced or control broods. However, this was not reflected in differences in parental body condition at the end of the nestling period. Females had higher prolactin levels than males during the nestling period. Male plasma prolactin levels were unrelated to brood size. Females given extra chicks tended to show higher titres of prolactin. Furthermore, female prolactin levels were positively correlated with the number of chicks raised. However, prolactin levels were not related to the number of feeding visits. These results suggest that in female House Sparrow, changes in prolactin levels could be mainly associated with the number of chicks in the nest rather than with the effort of provisioning the brood.

Key words: Passer domesticus, physiology, clutch size

 

Gray, D.A. 1998. Osmoregulatory role of avian plasma atrial natriuretic peptide. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 380.

The avian heart secretes a hormone, atrial natriuretic peptide (ANP) which is thought to participate in osmoregulation. Antibodies against ANP (anti-ANP) were used to characterise the physiological role of endogenous plasma ANP in salt and fluid homeostasis of Mallard Ducks Anas platyrhynchos; (1) Conscious birds, undergoing a steady-state renal and extra-renal (salt gland) excretion of salt and fluid, maintained by a constant intravenous infusion of isotonic saline at 2 ml.min^-1 and with an elevated plasma ANP (from basal of 75 pg ml^-1 to 269 pg ml^-1), responded to anti-ANP with an immediate 30% reduction in both kidney and salt gland outputs of sodium and water. (2) The increases in plasma antidiuretic hormone (ADH) caused by elevating plasma osmolality with an intravenous infusion of hypertonic saline, were greater in birds with plasma ANP levels suppressed (less than 10 pg ml^-1) by anti-ANP than in control animals in which ANP remained elevated (193 pg ml^-1). The results show that the high plasma levels of endogenous ANP associated with salt loading, aid in the regulation of salt and fluid balance by stimulating renal and extra-renal salt and water excretion and by suppressing osmotically stimulated ADH release.

Key words: salt gland, duck, Anas platyrhynchos, hormone

 

Holberton, R.L. 1998. Corticosterone and the development of migratory condition. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 380.

The Migration Modulation Hypothesis (MMH) addresses differences in corticosterone secretion between birds in migratory and non-migratory condition. Birds in migratory condition (1) Maintain elevated corticosterone (facilitating hyperphagia/lipogenesis), and (2) Suppress further increase in corticosterone in response to acute stress (protecting skeletal muscle needed for flight). This pattern differs during the non-migratory period when birds exhibit low corticosterone levels which increase with capture stress. Support for this hypothesis has come from free-living birds where it is difficult to determine the relationship between this change and the development of migratory condition. To test the hypothesis that corticosterone secretion changes with the development of migratory condition, fifteen Yellow-rumped Warblers Dendroica coronata were held through two transitions from short- (10.5:13.5 L:D) to long- (15.5:8.5 L:D) day photoperiod. Corticosterone stress profiles and measures of migratory and reproductive condition were recorded periodically. Lean birds on short-days maintained low basal corticosterone levels and exhibited a significant stress response. With the onset of long days they gained mass and fat, maintained higher levels of corticosterone and suppressed the stress response. These results support the MMH, demonstrating that changes in corticosterone secretion occur during the development of migratory condition.

Key words: corticosterone, migration, stress, lipogenesis

 

Hughes, M.R., Sullivan, T.M., Bennett, D.C., & Hwang, H. 1998. Effect of saline drinking water on movement of urine into the mallard gut. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 381.

Birds move urine into the hindgut where Na⁺ may be reabsorbed. High dietary Na⁺ reduces Na⁺ reabsorption in birds lacking salt glands, but not in birds with salt glands that may secrete the reabsorbed Na⁺ to generate free water. The influence of Na⁺ intake (drinking 0.3M NaCl) on rectal, cecal, and ileal mass and length and urine retropulsion (labelled with tritiated polyethylene glycol (³H-PEG)) was examined. Both sexes of the salt-glanded Mallard Duck Anas platyrhynchos, were used, since males are less salt tolerant. Birds were injected intra-venously with ³H-PEG and sacrificed three hours later. Both sexes, regardless of water regime, had refluxed about 20% of the urine into the hindgut (two-thirds of which was in the ceca). Saline intake increased both mass and length of the ilium (P < 0.02) and tended (0.09) to increase cecal length. Cecal contents had the least fluid. Results indicate neither saline nor sex affect movement of urine into the duck hindgut. Saline-related changes in the ileum and ceca suggest osmoregulatory potential for these sites. This research was supported by NSERC (MRH).

Key words: duck, hindgut, urine refluxing, saline accumulation, Anas platyrhynchos

 

Saint-Petersburg State University, Universitetskaya nab.7/9, 199034, Saint-Petersburg, Russia, e-mail obukhov@histo.bio.pu.ru

Konstantinov, L.V. & Obukhov, D.K. 1998. Telencephalon specific features in birds with different level of rational activity. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 381.

Ethological studies have demonstrated that some birds and higher mammals possess rational activity (RA). Corvidae have the highest level RA similar to that of primates. The Columbidae have a much lower level of RA. The present work investigates how the cytoarchitecture of some telencephalon areas, the hyperstriatum (zones HA, HD, HV, HIS) and neostriatun (NS) in Carrion Crow Corvus corone cornix L. and Rock Pigeon Columba livia L. are related to RA. These zones are homologous with certain zones of mammalian neocortex and are characteristic of the most complex structure. They contain multitude neuro-glial complexes or "modules". The structure, number and sizes of these complexes are very different in both different zones of hyper- and neostriatum and in the same zones of the studied species. We propose classification of these complexes. The greatest of the number of neurones, glial cells and neuro-glial complexes per square unit (cell density) in crow is observed in hyperstriatum ventrale (HV), while in the pigeon cell density is highest in nucleus intercalatus superior (HIS). Thus the HV is the most complex telencephalon zones in Hooded Crow, and HIS is the most complex zones in Rock Pigeon. This structural diversity is connected with different forms of rational activity. This work was supported by RFBR 94-04-11566.

Key words: Corvidae, nervous system, telencephalon, sensory systems

 

Michaeli, G. & Pinshow, B. 1998. Respiratory and cutaneous water loss in free-flying pigeons. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 382.

To estimate respiratory water loss in trained, free-flying Rock Pigeons, we measured respired air temperature (T_ex) and respiratory frequency (f). T_ex was sensed with a micro-bead thermistor inserted 3 mm into the pigeons nare’s and attached to an FM transmitter harnessed to the birds body. In 24 flights lasting 2-3 hours with 6 birds, at air temperatures (T_a) of 8 to 26 °C, steady state f was 5-7 Hz, while mean T_ex was 31.8± 2.6 °C and was independent of T_a. We calculated the rate of respiratory water loss (RWL) as the product of ventilation volume (V_g) and the difference between expired (assumed saturated at T_ex) and inspired water vapour density. V_g was the product of f and published values of tidal volume in flying pigeons. Mean RWL for the flights was 10.7 ± 2.8 mg.g^-1.h^-1. We measured the rate of total evaporative water loss (EWL) by mass balance and then calculated the rate of cutaneous water loss as CWL = EWL - RWL. Mean RWL was 32.1% of EWL, while mean CWL was 67.9% of EWL. We conclude that in free-flying pigeons the lack of dependence of T_ex on T_a suggests that birds use the respiratory system to conserve water, and that cutaneous water loss, especially at high ambient temperatures, contributes more to total evaporation than was previously supposed. This study was supported by US-Israel BSF grant 89-00350.

Key words: Columba livia, metabolism, telemetry, respiration, thermoregulation

 

Rayner, J.M.V., Gordon, R. & Martin, J. 1998. Experimental and theoretical visualisation of the wakes of flying birds. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 383.

The ordered vortex structures in the wakes of flying birds provide valuable clues to flight performance, and to forces and energy transfer on the wings in flight. In conjunction with recording of wingbeat kinematics, we have shown that the wakes provide evidence for a limited number of locomotor gaits in flapping flight. We are now able to analyse wake images taken by helium-bubble stereophotogrammetry automatically with a three-dimensional particle tracking system, and can determine the instantaneous velocity and vortex fields in the wake, and can accurately estimate the aerodynamic components of energy output. These flow fields are explored by computer visualisation techniques, and the resulting pictures aid interpretation of complex flow patterns. To explore how the wake is generated by the flapping wings, and to determine the effects of variation in wing shape, posture and kinematics, we are developing computational fluid dynamics (CFD) models based on large-amplitude unsteady vortex panel methods. The results are also displayed by the 3-D visualisation techniques. Flow patterns analysed so far confirm our earlier conclusion that only two gaits (vortex ring and continuous wake) are present in steady forward flight, and that only the vortex ring gait is present in slow flight and in birds with shorter and more rounded wings.

Key words: flight, wake, vortex, visualisation, wings

 

Reynolds, S.J. 1998. Morphological changes in medullary bone during egg-laying in the Zebra Finch Taeniopygia guttata. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban, University of Natal. Ostrich 69: 383.

Medullary bone forms only during egg laying. It is a short-term calcium store which is depleted to supply calcium for eggshell formation. Although studied extensively in the domestic chicken Gallus domesticus, little is known about the role of medullary bone during egg production in passerines. I studied the formation of medullary bone in Zebra Finch hens by comparing bone deposition between egg-laying and non-laying birds at specific times after oviposition. Wing, leg and keel bones were dissected from each bird and longitudinal sections were prepared and stained for medullary bone. Non-laying (control) birds had negligible medullary bone deposits, irrespective of the time of day they were sacrificed. Egg layers had significantly more medullary bone reserves soon after oviposition than in the later stages of egg laying. In the egg laying Zebra Finch, medullary bone is an important short-term store of calcium; deposition of medullary bone occurs during the day when the hen forages for calcium-rich material and overnight depletion of the reserves occurs to supply the high calcium demands of eggshell formation.

Key words: medullary, bone formation, Zebra Finch, Taeniopygia guttata, egg laying

 

Roberts, J.R., Leary, A. & Sharp, P. 1998. Role of aldosterone and prolactin in avian osmoregulation. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 383.

The roles of aldosterone and prolactin in avian osmoregulation remain unclear. Aldosterone enhances the uptake of sodium and water across the lower intestine of birds. However, although receptors for aldosterone are present in the kidney, the effect of aldosterone on kidney function has not been elucidated. Responses of plasma aldosterone to osmotic stress are species dependent. Water deprivation resulted in a reduction in plasma aldosterone in chickens Gallus gallus but an increase in the Galah Eolophus roseicapillus. In addition, the plasma aldosterone concentrations in the galah were consistently much higher than in the chicken, even for animals supplied with ad libitum water. Infusion of aldosterone into chickens resulted in few changes in kidney function. However, sodium and chloride excretion and fractional excretion were lower following aldosterone infusion. A role for prolactin in avian osmoregulation has been proposed following studies which have shown that the plasma concentration of prolactin increased following water deprivation or saline loading. However, our studies using a specific assay have been unable to duplicate this response. Saline loading resulted in reduced plasma prolactin and water deprivation caused no change in plasma prolactin. The role of aldosterone and prolactin in avian osmoregulation requires further clarification.

Key words: avian renal function, avian lower intestine, hormones and renal function

 

Schleucher, E. & Withers, P.C. 1998. Metabolic physiology of Australian pigeons and doves from different habitats. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 384.

Endotherms adapt to their environment by varying their metabolic rates. However, few studies have examined the comparative physiology of closely related species living in different environments. Pigeons and doves Columbidae, which are widespread in all Australian terrestrial habitats, are ideal for such a study. We measured the basal metabolic rates (BMR) of 14 species via oxygen consumption, and compared them with respect to taxonomy and biogeography. Previous allometric analyses predict low metabolic rates for pigeons compared with all birds, but columbid equations are based on relatively a few data. In contrast, pigeons in our study had intermediate metabolism on average. Lowered BMRs were found only in species confined to hot and arid regions. Even in closely related species, e.g. in the genus Phaps, there was a gradation in BMR according to their habitat. Species of the tropical rainforest regions e.g. Ptilinopus superbus, Chalcophaps indica or Columba leucomela, show average or elevated values. Our findings for pigeons and doves suggest that a wide range of species of various ecological backgrounds must be considered when comparing the metabolic status of taxonomic groups.

Key words: Columbidae, metabolic rate, adaptation to environment, taxonomy

 

Stradi, R. & Hudon, J. 1998. The complement of yellow and red pigments in true woodpeckers Picinae. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 384.

The colouration of woodpecker feathers provides vivid examples of parallelism in plumage patterns, introgressive hybridisation, modular evolution of colour patches, patterns and variation in sexual dimorphism. Studies on the pigments responsible for colours in woodpeckers go back to the earlier description of avian feather colours. The name picofulvin dates back to 1882, when it was used by Krukenberg to describe an unusual lipochrome in woodpecker feathers. These substances were later spectrally characterised by Brockmann and Volker who found them to absorb light at much shorter wavelengths than common xanthophylls. They also discussed their metabolic origin but did not elucidate their chemical structure. To fill this gap, we determined the complement of carotenoids in the red and yellow feathers of thirteen species of woodpeckers Picinae, that is Picus viridis, Picus squamatus, Picoides major, Picoides tridactylus, Picoides villosus, Dryocopus pileatus, Melanerpes lewis, Melanerpes candidus, Colaptes auratus, Colaptes melanolaimus, Colaptes campestris, Campephilus leucopogon, Sphyrapicus varius. The pigments were extracted under mild conditions and the extracts analysed by HPLC coupled with mass and UV-vis spectroscopy. The chemical basis for the red colours was shown to be provided by 4-oxo-carotenoids such as astaxanthin and alpha-doradexanthin, that for yellow colours by picofulvins in some species, by lutein, zeaxanthin and beta-cryptoxanthin in some others. Picofulvin structure was finally elucidated and related to diet.

Key words: woodpeckers, carotenoids, picofulvins, plumage

 

Tieleman, B.I. & Williams, J.B. 1998. The role of hyperthermia in the water economy of desert birds. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 385.

Hyperthermia, the elevation of body temperature (Tb) 2 to 4°C above normal, has been suggested to reduce total evaporative water loss (TEWL) in birds. We re-evaluate the benefits and costs of hyperthermia, and assess its net effect on the water economy of birds, especially desert species. First we consider the current model of heat balance in birds at high ambient temperatures (Ta), and show that in most studies, birds were increasing their Tb at high Ta’s, violating the assumption of steady state. Next we incorporate the rate of heat gain into calculations of the dry heat transfer coefficient (h) at high Ta’s. We develop a method to calculate h at Ta = Tb. Our results suggest that birds increase their h even at Ta’s above Ta = Tb, contrary to our prediction. Finally we explore aspects of hyperthermia that reduce water loss (improved thermal gradient, heat storage), and aspects that may augment water loss (changed respiratory variables). Our analysis of the combination of these factors suggests that during acute exposure to high Ta, 10-1000 g birds save about 50% of their TEWL by becoming hyperthermic. For chronic episodes of high Ta, small birds save water by hyperthermia but large birds do not.

Key words: hypothermia, water economy, body temperature, heat balance, birds

 

Thouzeau, C., Le Maho, Y. & Handrich, Y. 1998. Metabolic, thermoregulatory, and behavioural response to fasting in the cold in the European Barn Owl. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr. Durban, University of Natal. Ostrich 69: 385.

European populations of the Barn Owl Tyto alba are particularly affected by winter-induced starvation. Yet, their responses to fasting in the cold are still poorly documented. In this study, the metabolic response of Barn Owls to fasting, superimposed on cold exposure was investigated. Their behaviour was also monitored. Changes in oxygen consumption with ambient temperature showed a narrow thermoneutral zone with metabolic rate already increasing below ± 23 °C. Fasting in the cold induced a decrease in both metabolic rate and body temperature. The mass-specific resting metabolic rate decreased within the first day (16%) and remained constant thereafter. There was a marked daily rhythm in body temperature with an amplitude that increased during fasting and diurnal body temperature being lowered. Daily locomotor activity was maintained throughout the fast, but a rise in diurnal activity compensated for a decrease in nocturnal activity. Thus, in Barn Owls facing a winter fast, despite a decrease in resting metabolic rate, the maintenance of locomotor activity might reflect a poor adaptation to cold whereas the rise in diurnal activity might enhance the probability of finding prey.

Key words: fasting, metabolism, body temperature, locomotor activity, raptor

 

Totzke, U. & Bairlein, F. 1998. Implications of food supply and fattening in the migratory Garden Warbler Sylvia borin. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 385.

Birds often accumulate large amounts of fat either prior to migration as fuel for long-distance flights between summer and winter habitats or as energy reserve when residing in areas subject to harsh winters. The premigratory fattening is endogenously controlled and triggered by photoperiod, whereas for winter fattening, ambient temperature and food availability seem important. However, endocrine or regulatory metabolic factors are still mostly unknown. In captivity, Garden Warblers, a long-distance migrant wintering in the Afro-tropics, showed an increased fattening subsequent to transient food depletion during the fall premigratory period. As in mammals, many endocrine and metabolic adaptations for energy conservation during starvation are known in birds, though the proximate implication of such metabolic changes on premigratory fattening has not yet been considered. Therefore fattening in relation to plasma levels of endocrine and metabolic parameters were investigated in captive birds experiencing different feeding, but otherwise constant conditions during the fall migratory season. The possible implications for fattening and migration of free-living individuals are discussed. This study was supported by the Deutsche Forschungsgemeinschaft

Key words: fasting, lipogenesis, insulin, glucagon, corticosterone, thyroid hormones

 

Vorster, W., Potgieter, H.C., Lizamore, D.J. & Spies, J.H. 1998. b -hydroxynorvaline is an osteolathyrogenic agent in the chicken embryo. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr. Durban, University of Natal. Ostrich 69: 386.

Defects in the collagen matrix affect its metabolic fate as reflected by changes in excretion of deoxypyridinoline (Dpd) in the urine. b -Hydroxynorvaline (b -HNV) inhibits the assembly and excretion of procollagen from fibroblasts, which may affect the metabolism, and integrity of collagen in various structures. The purpose of this study was to investigate the effects of b -HNV on the developing chicken embryo. One hundred and twelve White Leghorn embryos were divided into four groups and dosed (48h post-incubation) with respectively, 75,150 and 300mM b -HNV, dissolved in distilled water. Controls were exposed to distilled water alone. Embryos were sacrificed on the 12^th day of development and the amnionic and allantoic fluids aspirated. Dpd and creatinine levels were quantified and embryos evaluated for abnormalities and mortality. Dpd/creatinine ratios were negatively and significantly correlated (P < 0.01) with b -HNV concentrations. Abnormalities encountered were spinae bifida, encephaloceles, retarded development and mortalities. We conclude that apart from other noticeable toxic effects, b -NHV displays osteolathyrogenic effects, causing abnormalities in the skeletal structures of the neural cord.

Key words: neural tube defects, collagen breakdown, Teratology