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PubMed1997

Allometry of ECG waves in mammals.

The present allometric study deals with the duration of three electrocardiographic intervals (PQ, QRS, QT) and their relationships with the corresponding cardiac cycle length (R-R interval) in mammals across a wide body mass range. The numerical values of the different ECG intervals were obtained from Grauwiler's (1965) monograph on the subject. Because the corresponding body masses were not given by this author, Heusner's (1991) data on basal metabolic rate as function of body mass were used to establish the most likely body mass figure for each case, based on the taxonomic identity between the corresponding specimens. On the other hand, in a recent study we established the "duality" of physiological times (Günther & Morgado, 1996) and, therefore, we adopted this novel approach to investigate the ECG intervals and their relationships with the R-R interval (heart rate reciprocal). Considering that the anatomy and physiology of auricles and ventricles are different (spheroids versus quasi-cylinders), and that excitation (sino-atrial node and His-Purkinje's system) and contraction processes can be described either by Euclidean or fractal geometries, only a quantitative analysis of the different ECG waves could resolve the dilemma. From the present preliminary study we can conclude that fractal geometry is prevalent with regard to ECG intervals.

Animals↗
PubMed2005

Exploring the mechanisms causing a high allometric value of female pleopod in the crayfish Procambarus clarkii.

Female pleopods in Procambarus clarkii have a function of holding eggs, and their length shows positive allometry. It is likely that the positive allometry has resulted from directional selection in terms of egg holding ability. Firstly, we examined the allometry of reproductive potential (ovarian egg number). The allometric value of reproductive potential was lower than that of pleopod length, which indicates that the positive allometry of pleopod length is not merely the reflection of the allometry of reproductive potential. Secondly, we examined the relationship between the relative length of pleopod and egg holding ability to test the presence of directional selection on the pleopod length, and then compared the strength of the directional selection between the individuals differing in their body sizes to infer the mechanisms causing the positive allometry for female pleopods. There was a positive relationship between relative pleopod length and relative egg mass remaining to the pleopod, and this relationship was stronger in small individuals. These relationships were not merely the reflection of relationship between pleopod length and reproductive potential. These results indicate that directional selection was acting on the length of female pleopods, and the strength of the directional selection was stronger in smaller individuals. Therefore, it appears that the positive allometry of female pleopods in P. clarkii has been caused by the constraint for possessing longer pleopods in small individuals, although the mechanisms of the constraint remain unknown.

Animals↗
PubMed2004

On the evolutionary significance of encephalization in some eutherian mammals: effects of adaptive radiation, domestication, and feralization.

Allometries of the brain to body size relationship in eutherian mammals are examined in this study as they can be used for comparative analyses concerning encephalization. In contrast with some modern presentations of this issue, an older concept is revived and expanded through this author's current study. Three allometries with clearly different slopes are valid and lead to reliable results: interspecific, intraspecific, and ontogenetic allometries. Interspecific allometries follow lines with slope values of 0.56 or 0.63 for larger and smaller species, respectively, and characterize different average encephalization plateaus with rodents and lagomorphs generally more strongly encephalized compared to basal insectivores. Artiodactyls, perissodactyls and carnivores as a whole are again on a higher but rather similar plateau. Several species of carnivores have reached different encephalization levels with respect to their average plateau indicating diverse radiations. A phylogenetic brain size increase from fossil to recent radiations is also evident. Intraspecific allometries have slope values of about 0.25. These are of help in comparing brain sizes of ancestral species with their domesticated relatives. Domestication has generally led to a brain size decrease, but species on higher encephalization plateaus show this trend more strongly than species on a lower level of encephalization. Several brain parts and the sense organs also decrease in size during the domestication process, but vary arbitrarily and to different degrees. Ontogenetic growth allometries are species-specific, but are especially different between altricial and precocial mammals. A very steep 1st phase slope of highly encephalized species is particularly useful for understanding evolutionary and adaptive phenomena. Domesticated mammals that have become feral do not show an increase in brain size despite living many generations in wild habitats.

Adaptation, Physiological↗
PubMed2005

Ontogeny, phylogeny, and morphology in anuran larvae: morphometric analysis of cranial development and evolution in Rana tadpoles (Anura: Ranidae).

Comparative studies of chondrocranial morphology in larval anurans are typically qualitative in nature, focusing primarily on discrete variation or gross differences in the size or shape of individual structures. Detailed data on chondrocranial allometry are currently limited to only two species, Rana sylvatica and Bufo americanus. This study uses geometric morphometric and multivariate statistical analyses to examine interspecific variation in both larval chondrocranial shape and patterns of ontogenetic allometry among six species of Rana. Variation is interpreted within the context of hypothesized phylogenetic relationships among these species. Canonical variates analyses of geometric morphometric datasets indicate that species can be clearly discriminated based on chondrocranial shape, even when whole ontogenies are included in the analysis. Ordinations and cluster analyses based on chondrocranial shape data indicate the presence of three primary groupings (R. sylvatica; R. catesbeiana + R. clamitans; and R. palustris + R. pipiens + R. sphenocephala), and patterns of similarity closely reflect phylogenetic relationships. Analysis of chondrocranial allometry reveals that some patterns are conserved across all species (e.g., most measurements scale with negative allometry, those associated with the posterior palatoquadrate tend to scale with isometry or positive allometry). Ontogenetic scaling along similar allometric trajectories, lateral transpositions of individual trajectories, and variable allometric relationships all contribute to shape differences among species. Overall patterns of similarity among ontogenetic trajectories also strongly reflect phylogenetic relationships. Thus, this study demonstrates a tight link between ontogeny, phylogeny, and morphology, and highlights the importance of including both ontogenetic and phylogenetic data in studies of chondrocranial evolution in larval anurans.

Animals↗
PubMed1986

Limb morphology of domestic and wild canids: the influence of development on morphologic change.

Biomechanical hypotheses are often invoked to explain the characteristic scaling of limb proportions. Patterns of static allometry and morphologic diversity, however, may also reflect the developmental mechanisms underlying morphologic change. In this study I document the importance of such developmental influences on the evolution of limb morphology in the extremely polymorphic domestic dog and in wild canid species. I use bivariate and discriminant function analyses to compare the limb morphology of adult dogs and wild canid species. I then compare ontogenetic allometry of four dog breeds with static allometry of domestic and wild canids. Results reveal, first, that there is considerable similarity between dogs and wild canid species; many wolf-like canids cannot be distinguished from domestic dogs of equivalent size. However, all dogs are consistently separated from fox-sized, wild canids by subtle but evolutionarily significant differences in olecranon, metapodial, and scapula morphology. Second, in domestic dogs the pattern of static allometry is nearly identical to that of ontogenetic allometry. This finding can be attributed to simple heterochronic alterations of postnatal growth rates. Apparently the diversity of limb proportions among adult domestic dogs and the observed difference between dogs and wild canids are somewhat predetermined, as they directly reflect the diversity of limb proportions evident during development of the domestic dog.

Animals↗
PubMed1999

The scaling of basicranial flexion and length.

Based on correlations between the cranial base angle (CBA) and the index of relative encephalization (IRE, calculated as the cubed root of brain volume divided by basicranial length), several recent studies have identified relative brain size as the factor most responsible for determining basicranial flexion in primates. IRE, however, scales with positive allometry relative to body mass, unlike the negatively allometric relationship between brain volume and body mass. This poses new questions concerning the factors underlying the correlation between IRE and CBA. Specifically, if basicranial flexion represents a spatial solution to the problem of housing a large brain within a neurocranium of limited size, then why is it that the problem is greatest in those species whose brains are smallest relative to body mass? To address this question, the scaling relationships of IRE and the measurements used to calculate it were examined in 87 primate species. It was found that the positive allometry of IRE is due to the fact that its denominator, basicranial length (BL), scales with very strong negative allometry relative to body mass. The scaling relationship of BL may reflect the fact that the noncortical components of the brain (i.e., diencephalon, mesencephalon, medulla) also scale with strong negative allometry relative to body mass, perhaps because of energetic constraints. Importantly, BL and these three brain components scale isometrically against each other. Thus, although cranial base flexion may be an adaptation to accommodate the size of the brain relative to basicranial length, the reason why that adaptation is necessary is not the evolution of a large brain, but rather the evolution of a short cranial base. In so far as basicranial length is affected by the strong negative allometry of the diencephalon, mesencephalon and medulla, the scaling relationships of these brain components are therefore indirectly responsible for the evolution of basicranial flexion.

Animals↗
PubMed2001

Localization of mandibular changes in patients with class II division 1 malocclusions treated with twin-block appliances: finite element scaling analysis.

Thirty mandibular landmarks were digitized from cephalographs of 46 children (prepubertal, approximately 10 years old) and 53 adolescents (pubertal, approximately 13 years old) to determine mandibular morphological changes in patients with Class II Division 1 malocclusions treated with Twin-block appliances. Procrustes superimposition computed average geometries and an analysis of variance were performed on the cephalographs. Prepubertal pretreatment and approximately 13-month-posttreatment profiles and pubertal pretreatment and approximately 22-month-posttreatment profiles were statistically different (P <.002). In male prepubertal configurations, a color-coded finite element scaling analysis revealed a conspicuous area of positive allometry ( approximately 12%) in the condylar neck and negative allometry ( approximately 17%) at the apex of the coronoid process. For the female prepubertal configuration, local increases in size were discernible in the condylar neck ( approximately 3%) and in the apex of the coronoid process ( approximately 4%). Comparing male pubertal configurations, finite element scaling analysis revealed marked positive allometry ( approximately 27%) in the condylar neck and negative allometry ( approximately 16%) at the apex of the coronoid process. For the female pubertal configurations, local increases in size were noticeable at the condylar neck ( approximately 15%), with negative allometry ( approximately 9%) in the coronoid process. For shape change, all configurations were highly isotropic over the entire mandibular nodal mesh. Therefore, in growing patients treated for Class II Division 1 malocclusions with Twin-block appliances, condylar growth, coronoid process remodeling, and osteogenesis in corpus and dentoalveolar regions may reflect the correction of the underlying skeletal dysmorphology.

Adolescent↗
PubMed1997

Normalizing strength for body size differences in older adults.

The purpose of this study was to compare the normalization methods of ratio standards, allometry, and ANCOVA with knee extensor strength of older adults. The apparently healthy older volunteers were 71 men (mean +/- SD; age, 71 +/- 4 yr; body mass, 81 +/- 10 kg; height, 174 +/- 7 cm) and 77 women (71 +/- 4 yr, 65 +/- 8 kg, 160 +/- 5 cm. respectively). Strength was defined as peak torque (N.m-1) and measured with a Cybex II isokinetic dynamometer. Body composition was estimated with dual energy x-ray absorptiometry. With allometry, the body mass exponent (0.74) was not statistically different from theory (0.67). Body mass adjusted strengths were 34.7% (allometry), 32.0% (ANCOVA), and 29.4% (ratio standards) greater in older men than women. Allometry revealed that the bone-free lean tissue mass exponent was not different from ratio standard exponent of 1.0. After adjustment by bone-free lean tissue mass, strength in men remained 16.0% (allometry and ratio standards) higher than in women, but, strength differences between genders were eliminated with ANCOVA. The methods used to normalize strength yielded similar results with body mass but conflicting results with bone-free lean tissue mass.

Aged↗
PubMed2005

Sexually dimorphic proportions of the harbour porpoise (Phocoena phocoena) skeleton.

Sexual differences in growth, allometric growth patterns and skeletal proportions were investigated by linear measurements of skeletal parts on 225 harbour porpoises (Phocoena phocoena) from the inner Danish and adjacent waters. Females show larger asymptotic sizes and extended period of growth compared with males. Measurements of the skull and flipper bones show negative allometry, whereas those of the bones of the body generally show positive allometry. There are no statistically significant intersexual differences in allometry except for the pelvic bones, where the males show stronger positive allometry. Throughout the range of individual sizes, females have significantly larger skulls and shorter vertebral columns than males for similarly sized individuals. In fully grown specimens, the condylobasal length of females makes up a smaller proportion of total length, and the vertebrae make up a larger proportion as compared with males. As these characters show negative and positive allometry, respectively, it is suggested that males finish their development at an earlier stage than females, retaining more paedomorphic proportions of the skeleton. Paedomorphosis in fully grown males relative to females is also found in the vertebral epiphyses that mature later in males than females, although the males finish growth at a younger age.

Animals↗
PubMed1998

Ontogeny, function, and scaling of the mandibular symphysis in papionin primates.

In vivo study of mastication in adult cercopithecine primates demonstrates a link between mandibular symphyseal form and resistance to "wishboning," or lateral transverse bending. Mechanical consideration of wishboning at the symphysis indicates exponentially higher stresses along the lingual surface with increasing symphyseal curvature. Lengthening the anteroposterior width of the symphysis acts to resist these higher loads. Interspecific adult cercopithecine allometries show that both symphyseal curvature and symphyseal width exhibit positive allometry relative to body mass. The experimental and allometric data support an hypothesis that the cercopithecine mandibular symphysis is designed to maintain functional equivalence--in this case dynamic strain similarity--in wishboning stress and strain magnitudes across adult cercopithecines. We test the hypothesis that functional equivalence during masticatory wishboning is maintained throughout ontogeny by calculating relative stress estimates from morphometric dimensions of the mandibular symphysis in two cercopithecine primates, Macaca fascicularis and M. nemestrina. Results indicate no significant differences in relative stress estimates among the two macaque ontogenies and an interspecific sample of adult papionin primates. Further, relative stress estimates do not change significantly throughout ontogeny in either species. These results offer the first evidence for the maintenance of functional equivalence in stress and strain levels during postnatal growth in a habitually loaded cranial structure. Scaling analyses demonstrate significant slope differences for both symphyseal curvature and width between the ontogenetic and interspecific samples. The distinct interspecific cercopithecine slopes are realized by a series of ontogenetic transpositions in both symphyseal curvature and width. Throughout papionin ontogeny, symphyseal curvature increases with less negative allometry, while symphysis width increases with less positive allometry versus the interspecific pattern. As symphyseal curvature and width are inversely proportional to one another in estimating relative stresses, functionally equivalent stress levels are maintained both ontogenetically and interspecifically, because the relatively slower rate of allometric increase in symphyseal curvature during growth is compensated for by a slower rate of allometric increase in symphyseal width. These results indicate the primacy of maintaining functional equivalence during growth and the need for ontogenetic data in understanding the evolutionary processes that affect form-function relations as well as the interspecific patterning of adult form across a clade.

Analysis of Variance↗
PubMed1981

Allometric analysis of dental variation in a human population.

There exists an extensive literature that deals with interspecific allometry, eg, brain size-body size relationships among species. Yet comparatively little attention has been paid to intraspecific or static adult allometry. An intraspecific allometric analysis was conducted on the complete permanent dentition of a prehistoric American Indian population (N = 156). Mesiodistal and buccolingual measurements were logarithmically transformed and regressed on log transformations of femur length, an estimate of body size. When measurements of antimeric teeth were introduced together into common regressions on femur length, 20 of the 32 slopes were significantly different from zero. Thirty-one of the slopes ranged between zero and one and clustered between 0.2 and 0.4. Hence, negative allometry describes the tooth size-body size association, ie, taller individuals in general possess absolutely but not relatively larger teeth than shorter individuals. In addition, no significant sex differences for the regression slopes were observed. Though significantly correlated, tooth size and body size variables are too weakly associated to permit accurate predictions from regression equations. Evolutionary implications of intraspecific dental allometry are discussed.

Body Height↗
PubMed2006

Post-hatching growth and development of the pectoral and pelvic limbs in the black noddy, Anous minutus.

The black tern (Anous minutus) uses a semi-precocial growth strategy. Terrestrial locomotor capacity occurs soon after hatching, but pectoral limb development is delayed and flight is not possible until about post-hatching day 50. A growth series (hatchlings to fledglings) was used to explore how limb musculoskeletal development varied with body mass. In the pelvic limb, bone lengths scaled isometrically or with negative allometry. Gastrocnemius muscle mass and the failure load and stiffness of the tibiotarsus scaled isometrically. In the pectoral limb, pectoralis and supracoracoideus muscle masses increased with strong positive allometry that was mirrored by increases in wing bone strength and stiffness. Bending strength (sigma(ult)) and modulus (E) remained fairly constant throughout development to fledging for all limb bones. The moment of inertia (I) scaled with negative allometry for the tibiotarsus and with strong positive allometry in the wing bones. Differences in sigma(ult) and E of the tibiotarsus between pre-fledged chicks and adults was due, primarily, to increases in bone density rather than increases in the moment of inertia of the skeletal elements, whereas sigma(ult) of wing bones was a function of increases in both bone density and I. Early development of functional pelvic limbs in tree-nesting birds is relatively unusual, and presumably reflects a familial trait that does not appear to compromise breeding success in this species.

Animals↗
PubMed2005

Molar scaling in strepsirrhine primates.

We examined how maxillary molar dimensions change with body and skull size estimates among 54 species of living and subfossil strepsirrhine primates. Strepsirrhine maxillary molar areas tend to scale with negative allometry, or possibly isometry, relative to body mass. This observation supports several previous scaling analyses showing that primate molar areas scale at or slightly below geometric similarity relative to body mass. Strepsirrhine molar areas do not change relative to body mass(0.75), as predicted by the metabolic scaling hypothesis. Relative to basicranial length, maxillary molar areas tend to scale with positive allometry. Previous claims that primate molar areas scale with positive allometry relative to body mass appear to rest on the incorrect assumption that skull dimensions scale isometrically with body mass. We identified specific factors that help us to better understand these observed scaling patterns. Lorisiform and lemuriform maxillary molar scaling patterns did not differ significantly, suggesting that the two infraorders had little independent influence on strepsirrhine scaling patterns. Contrary to many previous studies of primate dental allometry, we found little evidence for significant differences in molar area scaling patterns among frugivorous, folivorous, and insectivorous groups. We were able to distinguish folivorous species from frugivorous and insectivorous taxa by comparing M1 lengths and widths. Folivores tend to have a mesiodistally elongated M1 for a given buccolingual M1 width when compared to the other two dietary groups. It has recently been shown that brain mass has a strong influence on primate dental eruption rates. We extended this comparison to relative maxillary molar sizes, but found that brain mass appears to have little influence on the size of strepsirrhine molars. Alternatively, we observed a strong correlation between the relative size of the facial skull and relative molar areas among strepsirrhines. We hypothesize that this association may be underlain by a partial sharing of the patterning of development between molar and facial skull elements.

Animals↗
PubMed2005

Human encephalization and developmental timing.

Human evolution is frequently analyzed in the light of changes in developmental timing. Encephalization in particular has been frequently linked to the slow pace of development in Homo sapiens. The "brain allometry extension" theory postulates that the progressive extension of a conserved primate brain allometry into postnatal life was the basis for brain enlargement in the human lineage. This study shows that published primate and human growth data do not corroborate this model. Instead, the unique encephalization of H. sapiens is alternatively described as the result of evolutionary changes in three aspects of developmental timing. The first is a moderate extension in the duration of brain growth relative to our closest extant relatives, contrary to the view that human brain growth is drastically prolonged into postnatal life. Second, humans evolved a derived brain allometry in comparison with chimpanzees and early hominins. Third, humans (and other anthropoid primates to a lesser degree) display a significant retardation in early postnatal body growth in comparison with other mammals, which directly affects adult encephalization in our species. The rejection of the "brain allometry extension" model may require a reevaluation of the adaptive scenarios proposed to explain how human encephalization evolved.

Animals↗
PubMed2001

Relationships between host species and morphometric patterns in Fasciola hepatica adults and eggs from the northern Bolivian Altiplano hyperendemic region.

The highest prevalences and intensities of human fasciolosis by Fasciola hepatica are found in the northern Bolivian Altiplano, where sheep and cattle are the main reservoir host species and pigs and donkeys the secondary ones. Morphometric comparisons of many linear measurements, areas and ratios of F. hepatica adults (from sheep, cattle and pigs) and eggs (from sheep, cattle, pigs and donkeys) in natural liver fluke populations of the Bolivian Altiplano, as well as of F. hepatica adults and eggs experimentally obtained in Wistar rats infected with Altiplanic sheep, cattle and pig isolates, were made using computer image analysis and an allometric model. Although morphometric values of adult flukes from natural populations of sheep, cattle, and pigs showed great overlap, there were clear differences in allometric growth. The allometries analyzed were: body area (BA) versus body length (BL), BA versus body width (BW), BA versus perimeter (Pe), BA versus distance between posterior end of body and ventral sucker (P-VS), BL versus BW, BL versus Pe, and BL versus P-VS. These allometries show a good fit in the seven pairs of variables in all the populations examined. Comparative statistical analysis of the allometries shows that fluke adult populations from sheep, cattle and pigs significantly differ in BL versus BW and BL versus P-VS functions. Statistical analysis of F. hepatica egg size shows characteristic morphometric traits in each definitive host species. In experimentally infected rats, fluke adult allometry and egg morphometry do not vary depending on the Altiplanic definitive host species isolate. Our study reveals that the definitive host species decisively influences the size of F. hepatica adults and eggs, and these influences do not persist in a rodent definitive host model.

Animals↗
PubMed1979

An analysis of tooth and body size relationship in five primate taxa.

The strength and the nature of the covariance between tooth and body size was investigated in Homo, Gorilla, Pan, Papio and Colobus. When sexes are combined in each taxon, the correlations are strong enough to compare the allometry coefficients of taxa, and the non-human taxa show a sufficiently strong linear relationship to compute 'interspecific' allometry coefficients. Allometry coefficients for each variable were not uniform among the taxa, and coefficients also differed from one variable to another. Computed 'intra' and 'inter' specific allometry coefficients from these data suggest that canine size will usually scale at a higher level than molar crown area, which is at most isometric, and not positively allometric with respect to body size. The consequence is that larger representatives of a taxon would be expected to combine relatively larger canines with a proportional, or relatively smaller, molar crown area. It is pointed out that these differences do not correspond to those found between 'gracile' and 'robust' australopithecines.

Animals↗
PubMed1993

[Relative growth of physiques in laboratory-bred cynomolgus monkeys: a longitudinal study during the first 6 years of life].

Physical growth was studied longitudinally in laboratory-bred cynomolgus monkeys (Macaca fascicularis) aged from birth to 6.0 years in females and to 6.5 years in males. An allometric formula was applied to morphometrical growth data and the relative growth of each morphological site to anterior trunk length was analyzed. The growth patterns of all of the measurement sites in females and most of the sites in males showed monophasic allometry; while those of head length, head breadth and morphological upper face length in males were judged to show diphasic allometry. The growth patterns of morphological total face length, upper arm length and lower arm length in some males showed diphasic allometry. Morphological measurements with negative allometry were head length, head breadth, morphological total face length, total head height, biacrominal breadth hand length and foot length, while the other morphological measurements revealed isometry in both sexes. However, the values of the relative growth coefficient to anterior trunk length were larger in males than in females, except for in the case of biiliac breadth. These differences in growth patterns may cause the morphological differences between genders after sexual maturation in this primate species.

Age Factors↗
PubMed2001

The evolution of armament strength: evidence for a constraint on the biting performance of claws of durophagous decapods.

Performance data for the claws of six sympatric species of Cancer crabs confirmed a puzzling pattern reported previously for two other decapod crustaceans (stone crabs, Menippe mercenaria, and lobsters, Homarus americanus): Although biting forces increased, maximum muscle stresses (force per unit area) declined with increasing claw size. The negative allometry of muscle stress and the stress at a given claw size were fairly consistent within and among Cancer species despite significant differences in adult body size and relative claw size, but were not consistent among decapod genera. Therefore, claw height can be used as a reliable predictor of maximum biting force for the genus Cancer, but must be used with caution as a predictor of maximum biting force in wider evolutionary and biogeographical comparisons of decapods. The decline in maximum muscle stress with increasing claw size in Cancer crabs contrasts with the pattern in several other claw traits. Significantly, three traits that affect maximal biting force increased intraspecifically with increasing claw size: relative claw size, mechanical advantage, and sarcomere length of the closer muscle. Closer apodeme area and angle of pinnation of the closer muscle fibers varied isometrically with claw size. The concordant behavior of these traits suggests selection for higher biting forces in larger crabs. The contrast between the size dependence of muscle stress (negative allometry) and the remaining claw traits (isometry or positive allometry) strongly suggests that an as yet unidentified constraint impairs muscle performance in larger claws. The negative allometry of muscle stress in two distantly related taxa (stone crabs and lobsters) further suggests this constraint may be widespread in decapod crustaceans. The implications of this performance constraint for the evolution of claw size and the "arms-race" between decapod predators and their hard-shelled prey is discussed.

Animals↗