Cardio‐pulmonary anatomy in theropod dinosaurs: Implications from extant archosaurs

Although crocodilian lung and cardiovascular organs are markedly less specialized than the avian heart and lung air‐sac system, all living archosaurs possess four‐chambered hearts and heterogeneously vascularized, faveolar lungs. In birds, normal lung function requires extensive, dorsally situated nonvascularized abdominal air‐sacs ventilated by an expansive sternum and specially hinged costal ribs. The thin walled and voluminous abdominal air‐sacs are supported laterally and caudally to prevent inward (paradoxical) collapse during generation of negative (inhalatory) pressure: the synsacrum, posteriorly directed, laterally open pubes and specialized femoral‐thigh complex provide requisite support and largely prevent inhalatory collapse. In comparison, theropod dinosaurs probably lacked similarly enlarged abdominal air‐sacs, and skeleto‐muscular modifications consistent with their ventilation. In the absence of enlarged, functional abdominal air‐sacs, theropods were unlikely to have possessed a specialized bird‐like, air‐sac lung. The likely absence of bird‐like pulmonary function in theropods is inconsistent with suggestions of cardiovascular anatomy more sophisticated than that of modern crocodilians. J. Morphol. 2009. © 2009 Wiley‐Liss, Inc.     

Periosteal biaxial residual strains correlate with bone specific growth rates in chick embryos

It has been proposed that periosteal residual tensile strains influence periosteal bone apposition and endochondral ossification. The role of bone growth rates on the development of residual strains is not well known. This study examined the relationships between specific growth rate and residual strains in chick tibiotarsi. We measured length and circumference during embryonic days 11-20 using microCT. Bones grew faster in length, with longitudinal and circumferential specific growth rates decreasing from 17 to 9% and 14 to 8% per day, respectively. To calculate residual strains, opening dimensions of incisions through the periosteum were analysed using finite element techniques. Results indicate that Poisson's ratio for an isotropic material model is between 0 and 0.04. For the model with Poisson's ratio 0.03, longitudinal and circumferential residual strains decreased from 46.2 to 29.3% and 10.6 to 3.9%, respectively, during embryonic days 14-20. Specific growth rates and residual strains were positively correlated (p<0.05).     

Relative growth rates of predator and prey dinosaurs reflect effects of predation

Hadrosaurs grew rapidly, and quantifying their growth is key to understanding life-history interactions between predators and prey during the Late Cretaceous. In this study, we longitudinally sampled a sequence of lines of arrested growth (LAGs) from an essentially full-grown hadrosaur Hypacrosaurus stebingeri (MOR 549). Spatial locations of LAGs in the femoral and tibial transverse sections of MOR 549 were measured and circumferences were calculated. For each bone, a time series of circumference data was fitted to several stochastic, discrete growth models. Our results suggest that the femur and the tibia of this specimen of Hypacrosaurus probably followed a Gompertz curve and that LAGs reportedly missing from early ontogeny were obscured by perimedullary resorption. In this specimen, death occurred at 13 years and took approximately 10-12 years to reach 95 per cent asymptotic size. The age at growth inflection, which is a proxy for reproductive maturity, occurred at approximately 2-3 years. Comparisons with several small and large predatory theropods reveal that MOR 549 grew faster and matured sooner than they did. These results suggest that Hypacrosaurus was able to partly avoid predators by outgrowing them.     

An infrared, thermographic study of surface temperature in three ratites: ostrich, emu and double-wattled cassowary

(1)Surface temperatures of the ostrich (Struthio camelus), emu (Dromaius novaehollandiae) and double-wattled cassowary (Casuarius casuarius) were meas ured using infrared thermography at ambient temperatures ranging from 0 to 27°C. (2) The pattern of surface temperature regulation for thermoregulatory purposes was similar in all species examined. Beak, lower leg and neck surface temperatures are regulated in all species to alter heat exchange with the environment. The feet and toes are also used by the ostrich and emu to regulate heat exchange. The cassowary does not use the feet and toes to the same extent but used the casque in a similar manner. (3) Standard metabolic rates were estimated using a geometric model of a bird and instantaneous heat loss calculated for specific body parts. (4) Up to 40% of metabolic heat production can be dissipated across these structures which comprise 12% and 17.5% of total body surface area. (5) The ostrich was able to regulate surface temperature more precisely than the other species, probably due to a larger body size. The large wings of the ostrich are useful for thermoregulation by increasing convective heat loss.     

Kinematic parameters of terrestrial locomotion in cursorial (ratites), swimming (ducks), and striding birds (quail and guinea fowl).

The importance of size, functional features and morphological features in adaptation for walking in birds were studied. The time and space kinematic parameters of locomotion were compared in two running birds, the ratites (rhea, kiwi, Paleognatiforms), in two swimming birds, (ducks) and two striding birds, (quail and Guinea fowl). The results showed that in the two phases, stance and swing, the time and space parameters worked in opposite ways: the duration of the swing was constant, but its length increased with speed. In contrast, the duration of the stance was correlated to speed, while its length was not (except in ducks). In all the birds, a higher speed was achieved by a decrease of the stance duration, and an increase of the swing length. The kinematic parameters were not used in the same way in all species: There is a size effect and large birds increase their speed mainly by increasing the frequency of their movements and the small species increase mainly their amplitude. Nevertheless, it is not the main factor and morphology, such as swimming adaptation features of the ducks, and behaviour, are important because they modify the mechanical constraints and influence the kinematics parameters.     

Morphogenesis of bone ornamentation in extant and extinct crocodilians

Summary Histological study of bone in the skull and osteoscutes of extant and extinct Crocodylia reveals that the skeletal ornamentation of crocodiles is caused by a process of differential, superficial resorption of bone. A partial reconstruction follows the resorption, and several resorption-reconstruction cycles are necessary to suit pit dimensions to overall bone growth. Bone ornamentation is a dynamic structure during ontogeny: the shape and the location of a given pit or groove vary in accordance with the instantaneous regional trends of skeletal growth. This supports the contention that bone oranmentation can be used as a reliable indicator of regional bone growth trends.     

Structural variation in d(CTCTAGAG). Implications for protein-DNA interactions

Single-crystal X-ray diffraction techniques have been used to characterize the structure of the self-complementary DNA oligomer d(CTCTAGAG). The structure was refined to an R factor of 14.7% using data to 2.15-A resolution. The tetragonal unit cell, space group P4(3)2(1)2, has dimensions a = 42.53 and c = 24.33 A. The asymmetric unit consists of a single strand or four base pairs. Two strands, related by a crystallographic dyad axis, coil about each other to form a right-handed duplex. This octamer duplex has a mean helix rotation of 32 degrees, 11.3 base pairs per turn, an average rise of 3.1 A, C3'-endo furanose conformations, a shallow minor groove, and a deep major groove. Such averaged parameters suggest classification of the octamer as a member of the A-DNA family. However, the global parameters tend to mask variations in conformational parameters observed at the level of the base pairs. In particular, the central TpA (= TpA) step displays extensive interstrand purine-purine overlap and an unusual sugar-phosphate backbone conformation. These structural features may be directly related to certain sequence-specific protein-DNA interactions involving nucleases and repressors.     

High-resolution computed tomography for the comparative study of fossil and extant bone

Special methods have been developed to use computed tomography (CT) for 3-dimensional imaging of both fossil and extant bones. Most commercial CT scanners cannot display the internal structure of fossils because the very high density is beyond the upper limits of the normal CT number scale (Hounsfield scale) of the scanners. X-ray projections from CT scans of fossils were modified by scaling the data to provide an expanded CT number scale, allowing the internal structure of highly fossilized objects to be visualized. These images were compared with state-of-the-art, high-resolution CT images of extant bone. Special image reformatting software was used to provide qualitative and quantitative 3-dimensional imaging. The recent rapid advances in CT technology have made this imaging modality the procedure of choice in much of diagnostic radiology. Use of this tool in paleoanthropology has been limited in the past by restricted access to scanners. However, new developments in CT will make this technique available to many researchers in the near future.     

In vivo bone strain and ontogenetic growth patterns in relation to life-history strategies and performance in two vertebrate taxa: goats and emu

This study examined ontogenetic patterns of limb loading, bone strains, and relative changes in bone geometry to explore the relationship between in vivo mechanics and size-related changes in the limb skeleton of two vertebrate taxa. Despite maintaining similar relative limb loads during ontogeny, bone strain magnitudes in the goat radius and emu tibiotarsus generally increased. However, while the strain increases in the emu tibiotarsus were mostly insignificant, strains within the radii of adult goats were two to four times greater than in young goats. The disparity between ontogenetic strain increases in these taxa resulted from differences in ontogenetic scaling patterns of the cross-sectional bone geometry. While the cross-sectional and second moments of area scaled with negative allometry in the goat radius, these measures were not significantly different from isometry in the emu tibiotarsus. Although the juveniles of both taxa exhibited lower strains and higher safety factors than the adults, the radii of the young goats were more robust relative to the adult goats than were the tibiotarsi of the young compared with adult emu. Differences in ontogenetic growth and strain patterns in the limb bones examined likely result from different threat avoidance strategies and selection pressures in the juveniles of these two taxa.     

Postcranial element shape and function: assessing locomotor mode in extant and extinct mustelid carnivorans

Assessment of locomotor modes in fossil taxa must often be made on the basis of heavily fragmented postcranial material. Previous authors have used quantitative methods to determine locomotor function from whole postcranial elements. The goals of this project were to assess the ability of element shape to discern between locomotor modes through landmark analysis, and to apply the results to assessment of fossils. Results suggest that element shape is a good predictor of function, but that different elements have different predictive capacities for each locomotor mode. Additionally, a relationship between size and shape exists that appears to drive morphological differentiation in the group. Finally, data from the extant sample were applied to fossil material of the extinct Plio-Pleistocene taxon Trigonictis . The results suggest that the locomotor mode of Trigonictis was generalized and probably an intermediate between the half-bound locomotion found in weasels and ferrets and the scansorial locomotion of martens and fishers.  © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society , 2007, 150 , 895–914.     

Molecular characterization of goose- and chicken-type lysozymes in emu (Dromaius novaehollandiae): evidence for extremely low lysozyme levels in emu egg white

Lysozyme (LZ), a bacteriolytic enzyme, is found in the egg white of many avian eggs and plays an important role in host defense; however, LZ activity in emu (Dromaius novaehollandiae) egg white is exceptionally undetectable. We cloned and characterized emu goose-type LZ (LZG) and chicken-type LZ (LZC) genes. RT-PCR analysis revealed very low LZG gene expression levels and absence of LZC gene expression in the emu oviduct. Sequencing of full-length LZG and LZC cDNAs indicated that their amino acid sequences show high similarities to ostrich LZG and LZC, respectively, with conserved catalytic residues for enzymatic activities. Whereas recombinant emu LZG prepared using Pichia pastoris exhibited similar enzyme activity as ostrich LZG, recombinant emu LZC exhibited significantly higher lytic activity than chicken LZC. We concluded that emus have functional genes for both LZG and LZC like many other avians, and the LZG gene is expressed in oviduct probably as in other ratite, however, its expression levels in egg white were low to be detected.     

A method for assessing phagocyte clearance rates in man.

By comparing the clearance rates of ICG and 99mTc-sulphur colloid from the blood stream, it has been possible to provide a method for assessing the phagocytic activity of the reticulo-endothelial system in man.     

Evidence for speciational change in the evolution of ratites (Aves: Palaeognathae)

To perform a comparative analysis of character associations framed in a phylogenetic context (e.g. independent contrasts), a model of character evolution must be assumed. According to phyletic gradualism, morphological change accumulates gradually over time within lineages, and speciation events do not have a major role. Under speciational models, morphological change is assumed to occur during or just after cladogenesis in both daughter species, and the resulting morphologies do not change over long periods of time (stasis), until the next cladogenetic event. A novel method is presented for comparing these models of character evolution that uses permutational multiple phylogenetic regressions. The addition of divergence times to well-corroborated phylogenetic trees and the utilization of the method developed in this paper allows the estimation of relative frequency of gradual change and speciational change from living organisms. This method is applied to a dataset from ratites with the conclusion that, for a range of morphological features, change tends to have been speciational rather than gradual.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 80 , 99–106.     

Variation in penaeid shrimp growth rates along an estuarine salinity gradient: Implications for managing river diversions

Freshwater inflows from river diversions may affect nekton populations by altering the salinity and temperature of estuarine waters. To investigate the influence of these environmental variables on the growth and survival rates of brown shrimp Farfantepenaeus aztecus and white shrimp Litopenaeus setiferus, we conducted field experiments in May and September 2007 to expose experimental animals to the range of different combinations of salinity and water temperature that commonly occur in an estuarine environment. Growth rates for shrimp held in mesocosms for approximately 7 days were compared among four locations and three treatments; locations were identified by the dominant marsh vegetation and distance from the Gulf of Mexico (low to high salinity: Intermediate, Brackish, Saline UE = Saline Up Estuary, Saline DE = Saline Down Estuary). At each location, the treatments were replicated four times and included shallow water with additional food, shallow water without food added, and deeper water (an attempt to expose animals to lower temperatures). Our experiments were designed to test the null hypothesis that shrimp growth and survival rates did not differ by location or treatment. Both brown shrimp and white shrimp grew more slowly at the Intermediate than higher salinity locations. Potential prey (benthic infauna) biomass was relatively low at both the Intermediate and Brackish locations in May, and both shrimp species consistently grew faster in mesocosms where food was added. We conclude that reduced growth in low salinity environments is likely due to the combined effects of increased metabolic costs and less food in these areas. River diversions that reduce estuarine salinities over a large portion of available habitat during peak recruitment periods may reduce overall growth rates and shrimp productivity in the affected areas.     

Methods of assessing population increase in aphids and the effect of growth stage of the host plant on population growth rates

Realistic values of population growth rates are needed when used in forecasting programmes, e.g., in a programme of integrated control. Therefore, comparisons were made in a chrysanthemum – aphid system between different methods of assessing population growth rates. The reproductive performances of the aphid species Aphis gossypii and Myzus persicae were measured on two chrysanthemum cultivars using three plant growth stages (young vegetative, budding and flowering). In the first set of experiments, development time and reproduction were used to estimate the population growth rate r_m. The mean relative growth rates (MRGR) were also assessed. It was shown for the first time that the relationship between r_m and MRGR was influenced by aphid species. In a second experiment, the aphid population increase on a whole plant was measured and r_m was estimated by calculating the slope of the (ln transformed) population increase. It is shown that population growth rate is affected by the growth stage of the plant, and that cultivar and aphid species interact with plant growth stage in influencing population growth rate. Thus, no single growth stage of chrysanthemum for maximal aphid population growth can be assigned, but the budding and flowering stage are the most suitable in three out of four aphid × cultivar combinations. Comparison between the results from both experiments demonstrates clearly that more realistic values for r_m are obtained when measured on whole plants.