Trabecular bone variation in the gorilla calcaneus

OBJECTIVES

Calcaneal external shape differs among nonhuman primates relative to locomotion. Such relationships between whole-bone calcaneal trabecular structure and locomotion, however, have yet to be studied. Here we analyze calcaneal trabecular architecture in Gorilla gorilla gorilla, Gorilla beringei beringei, and G. b. graueri to investigate general trends and fine-grained differences among gorilla taxa relative to locomotion.

MATERIALS AND METHODS

Calcanei were micro-CT scanned. A three-dimensional geometric morphometric sliding semilandmark analysis was carried out and the final landmark configurations used to position 156 volumes of interest. Trabecular thickness (Tb.Th), trabecular spacing (Tb.Sp), and bone volume fraction (BV/TV) were calculated using the BoneJ plugin for ImageJ and MATLAB. Non-parametric MANOVAs were run to test for significant differences among taxa in parameter raw values and z-scores. Parameter distributions were visualized using color maps and summarized using principal components analysis.

RESULTS

There are no significant differences in raw BV/TV or Tb.Th among gorillas, however G. b. beringei significantly differs in z-scores for both parameters (p = <0.0271). All three taxa exhibit relatively lower BV/TV and Tb.Th in the posterior half of the calcaneus. This gradation is exacerbated in G. b. beringei. G. b. graueri significantly differs from other taxa in Tb.Sp z-scores (p < 0.001) indicating a different spacing distribution.

DISCUSSION

Relatively higher Tb.Th and BV/TV in the anterior calcaneus among gorillas likely reflects higher forces associated with body mass (transmitted through the subtalar joint) relative to forces transferred through the posterior calcaneus. The different Tb.Sp pattern in G. b. graueri may reflect proposed differences in foot positioning during locomotion.

Morphological and evolutionary insights into the keystone element of the human foot's medial longitudinal arch

The evolution of the medial longitudinal arch (MLA) is one of the most impactful adaptations in the hominin foot that emerged with bipedalism. When and how it evolved in the human lineage is still unresolved. Complicating the issue, clinical definitions of flatfoot in living Homo sapiens have not reached a consensus. Here we digitally investigate the navicular morphology of H. sapiens (living, archaeological, and fossil), great apes, and fossil hominins and its correlation with the MLA. A distinctive navicular shape characterises living H. sapiens with adult acquired flexible flatfoot, while the congenital flexible flatfoot exhibits a 'normal' navicular shape. All H. sapiens groups differentiate from great apes independently from variations in the MLA, likely because of bipedalism. Most australopith, H. naledi, and H. floresiensis navicular shapes are closer to those of great apes, which is inconsistent with a human-like MLA and instead might suggest a certain degree of arboreality. Navicular shape of OH 8 and fossil H. sapiens falls within the normal living H. sapiens spectrum of variation of the MLA (including congenital flexible flatfoot and individuals with a well-developed MLA). At the same time, H. neanderthalensis seem to be characterised by a different expression of the MLA.

A geometric morphometric approach to investigate primate proximal phalanx diaphysis shape

Current approaches to quantify phalangeal curvature assume that the long axis of the bone's diaphysis approximates the shape of a portion of a circle (included angle method) or a parabola (second-degree polynomial method). Here we developed, tested, and employed an alternative geometric morphometrics-based approach to quantify diaphysis shape of proximal phalanges in humans, apes and monkeys with diverse locomotor behaviors. 100 landmarks of the central longitudinal axis were extracted from 3D surface models and analyzed using 2DGM methods, including Generalized Procrustes Analyses. Principal components analyses were performed and PC1 scores (>80% of variation) represented the dorsopalmar shape of the bone's central longitudinal axis and separated taxa consistently and in accord with known locomotor behavioral profiles. The most suspensory taxa, including orangutans, hylobatids and spider monkeys, had significantly lower PC1 scores reflecting the greatest amounts of phalangeal curvature. In contrast, bipedal humans and the quadrupedal cercopithecoid monkeys sampled (baboons, proboscis monkeys) exhibited significantly higher PC1 scores reflecting flatter phalanges. African ape (gorillas, chimpanzees and bonobos) phalanges fell between these two extremes and were not significantly different from each other. PC1 scores were significantly correlated with both included angle and the a coefficient of a second-degree polynomial calculated from the same landmark dataset, but had a significantly higher correlation with included angles. Our alternative approach for quantifying diaphysis shape of proximal phalanges to investigate dorsopalmar curvature is replicable and does not assume a priori either a circle or parabola model of shape, making it an attractive alternative compared with existing methodologies.

Bone volume in the distal calcaneus correlates with body size but not leap frequency in galagids

OBJECTIVES

Primate leap performance varies with body size, where performance will be optimized in lightweight individuals due to the inverse relationship between force generation and body mass. With all other factors equal, it is less energetically costly to swing a light hindlimb than a heavier hindlimb. Previous work on the calcaneus of galagids hypothesized that bone volume in leaping galagids may be minimized to decrease overall hindlimb mass. We predict that (1) lighter taxa will exhibit relatively less calcaneal bone volume than heavier taxa, and (2) taxa that are high-frequency leapers will exhibit relatively less bone volume than lower frequency leapers.

MATERIALS AND METHODS

Relationships among bone volume, body size, and leap frequency (high vs. low) were examined in a sample of 51 individuals from four genera of galagids (Euoticus, Galago, Galagoides, and Otolemur) that differ in the percentage of time engaged in leaping locomotion. Using μCT scans of calcanei, we quantified relative bone volume (BV/TV) of the distal calcaneal segment and predicted that it would vary with body size and frequency of leaping locomotion.

RESULTS

Phylogenetic generalized least squares (PGLS) regression models indicate that body size, but not leaping frequency, affects BV/TV in the distal calcaneus. Relative bone volume increases with body size, supporting our first hypothesis.

DISCUSSION

These results support previous work demonstrating a positive correlation between BV/TV and body size. With some exceptions, small galagids tend to have less BV/TV than larger galagids. Leaping frequency does not relate to BV/TV in this sample; larger taxonomic and/or behavioral sampling may provide additional insights.

Evolutionary trends of the lateral foot in catarrhine primates: Contextualizing the fourth metatarsal of Australopithecus afarensis

In 2000, a complete fourth metatarsal (Mt4) of the ∼3- to 4-Million-year-old hominin Australopithecus afarensis was recovered in Hadar, Ethiopia. This metatarsal presented a mostly human-like morphology, suggesting that a rigid lateral foot may have evolved as early as ∼3.2 Ma. The lateral foot is integral in providing stability during the push off phase of gait and is key in understanding the transition to upright, striding bipedalism. Previous comparisons of this fossil were limited to Pan troglodytes, Gorilla gorilla, and modern humans. This study builds on previous studies by contextualizing the Mt4 morphology of A. afarensis (A.L. 333-160) within a diverse comparative sample of nonhuman hominoids (n = 144) and cercopithecids (n = 138) and incorporates other early hominins (n = 3) and fossil hominoids that precede the Pan-Homo split (n = 4) to better assess the polarity of changes in lateral foot morphology surrounding this divergence. We investigate seven morphological features argued to be functionally linked to human-like bipedalism. Our results show that some human-like characters used to assess midfoot and lateral foot stiffness in the hominin fossil record are present in our Miocene ape sample as well as in living cercopithecids. Furthermore, modern nonhuman hominoids can be generally distinguished from other species in most metrics. These results suggest that the possession of a rigid foot in hominins could represent a conserved trait, whereas the specialized pedal grasping mechanics of extant apes may be more derived, in which case some traits often used to infer bipedal locomotion in early hominins may, instead, reflect a lower reliance on pedal grasping. Another possibility is that early hominins reverted from modern ape Mt4 morphology into a more plesiomorphic condition when terrestrial bipedality became a dominant behavior. More fossils dating around the Pan-Homo divergence time are necessary to test these competing hypotheses.

Homo naledi pollical metacarpal shaft morphology is distinctive and intermediate between that of australopiths and other members of the genus Homo

Homo naledi fossils from the Rising Star cave system provide important insights into the diversity of hand morphology within the genus Homo. Notably, the pollical (thumb) metacarpal (Mc1) displays an unusual suite of characteristics including a median longitudinal crest, a narrow proximal base, and broad flaring intrinsic muscle flanges. The present study evaluates the affinities of H. naledi Mc1 morphology via 3D geometric morphometric analysis of shaft shape using a broader comparative sample (n = 337) of fossil hominins, recent humans, apes, and cercopithecoid monkeys than in prior work. Results confirm that the H. naledi Mc1 is distinctive from most other hominins in being narrow at the proximal end but surmounted by flaring muscle flanges distally. Only StW 418 (Australopithecus cf. africanus) is similar in these aspects of shape. The gracile proximal shaft is most similar to cercopithecoids, Pan, Pongo, Australopithecus afarensis, and Australopithecus sediba, suggesting that H. naledi retains the condition primitive for the genus Homo. In contrast, Neandertal Mc1s are characterized by wide proximal bases and shafts, pinched midshafts, and broad distal flanges, while those of recent humans generally have straight shafts, less robust muscle flanges, and wide proximal shafts/bases. Although uncertainties remain regarding character polarity, the morphology of the H. naledi thumb might be interpreted as a retained intermediate state in a transformation series between the overall gracility of the shaft and the robust shafts of later hominins. Such a model suggests that the addition of broad medial and lateral muscle flanges to a primitively slender shaft was the first modification in transforming the Mc1 into the overall more robust structure exhibited by other Homo taxa including Neandertals and recent Homo sapiens in whose shared lineage the bases and proximal shafts became expanded, possibly as an adaptation to the repeated recruitment of powerful intrinsic pollical muscles.

Morphological analysis of new Dryas Monkey specimens from the Central Congo Basin: Taxonomic considerations and an emended diagnosis

OBJECTIVES

The little known guenon Cercopithecus dryas has a controversial taxonomic history with some recognizing two taxa (C. dryas and C. salongo) instead of one. New adult specimens from the TL2 region of the central Congo Basin allow further assessment of C. dryas morphology and, along with CT scans of the juvenile holotype, provide ontogenetically stable comparisons across all C. dryas and "C. salongo" specimens for the first time.

MATERIALS AND METHODS

The skins and skulls of two newly acquired C. dryas specimens, male YPM MAM 16890 and female YPM MAM 17066, were compared to previously described C. dryas and "C. salongo" specimens, along with a broader guenon comparative sample (cranial sample n = 146, dental sample n = 102). Qualitative and quantitative assessments were made on the basis of commonly noted pelage features as well as craniodental characters in the form of shape ratios and multivariate discriminant analyses.

RESULTS

All C. dryas specimens, including the TL2 adults, are comparatively small in overall cranial size, have relatively small I¹ s, and display tall molar cusps; these osteological characters, along with pelage features, are shared with known "C. salongo" specimens. Discriminant analyses of dental features separate C. dryas/salongo specimens from all other guenons.

DISCUSSION

In addition to pelage-based evidence, direct osteological evidence suggests "C. salongo" is a junior synonym of C. dryas. Combined with molecular analyses suggesting C. dryas is most closely related to Chlorocebus spp., we emend the species diagnosis and support its transfer to Chlorocebus or possibly a new genus to reflect its distinctiveness.

New Middle Miocene Ape (Primates: Hylobatidae) from Ramnagar, India fills major gaps in the hominoid fossil record

The fossil record of 'lesser apes' (i.e. hylobatids = gibbons and siamangs) is virtually non-existent before the latest Miocene of East Asia. However, molecular data strongly and consistently suggest that hylobatids should be present by approximately 20 Ma; thus, there are large temporal, geographical, and morphological gaps between early fossil apes in Africa and the earliest fossil hylobatids in China. Here, we describe a new approximately 12.5-13.8 Ma fossil ape from the Lower Siwaliks of Ramnagar, India, that fills in these long-standing gaps with implications for hylobatid origins. This ape represents the first new hominoid species discovered at Ramnagar in nearly a century, the first new Siwalik ape taxon in more than 30 years, and likely extends the hylobatid fossil record by approximately 5 Myr, providing a minimum age for hylobatid dispersal coeval to that of great apes. The presence of crown hylobatid molar features in the new species indicates an adaptive shift to a more frugivorous diet during the Middle Miocene, consistent with other proposed adaptations to frugivory (e.g. uricase gene silencing) during this time period as well.

Medial Femoral Trochlea Osteochondral Graft: A Quantitative Anatomic Comparison to the Proximal Pole of the Scaphoid

Background  Treatment of scaphoid proximal pole (SPP) nonunion with a vascularized osteochondral graft from the medial femoral trochlea (MFT) has been described, with positive outcomes thus far. However, our understanding of the congruency between the articular surfaces of these structures is incomplete. Objective  Our purpose was to evaluate the congruency of the MFT and SPP using a quantitative anatomical approach. Methods  The distal femur and ipsilateral scaphoid were dissected from 12 cadavers and scanned with computerized tomography. Three-dimensional models were created and articular surfaces were digitally "dissected." The radius of curvature (RoC) of the radioulnar (RU) and proximodistal (PD) axes of the SPP and MFT, respectively, as well as the orthogonal axes (SPP, anteroposterior [AP]; MFT, mediolateral [ML]) were calculated. The RoC values were compared using the Wilcoxon signed-rank test. Results  The RoC values for the SPP and MFT were not significantly different in the RU-PD plane ( p  = 0.064). However, RoC values for the SPP and MFT were significantly different in the AP-ML plane ( p  = 0.001). Conclusions  For most individuals, the RU curvature of the SPP was similar to the PD curvature of the MFT. For nearly all individuals, the AP curvature of the SPP and the ML curvature of the MFT shared less congruence. Clinical Relevance  Articular surface congruity may not be a critical factor associated with improvements in wrist function following this procedure.

Calcaneal elongation and bone strength in leaping galagids

OBJECTIVES

Small-bodied vertical clinging and leaping primates have elongated calcanei which enhance leap performance by optimizing leap velocity, distance, and acceleration, but at the expense of experiencing relatively large forces during takeoff and landing. This study tests the hypothesis that the elongated calcaneus of leaping galagids is adapted to resist larger and more stereotyped bending loads compared to more quadrupedal galagids.

MATERIALS AND METHODS

The calcanei of 14 individuals of Otolemur and 14 individuals of Galago (three species of each genus) were μCT scanned. Calcaneal cross-sectional properties (maximum and minimum second moments of area and polar section modulus) were obtained from a slice representing the 50% position of bone segment length and dimensionless ratios were created for each variable using calcaneal cuboid facet area as a proxy for body mass.

RESULTS

There were no significant differences in size-adjusted bending strength between Galago and Otolemur. Galago exhibited more elliptically shaped calcaneal cross sections, however, suggesting that its calcanei are more adapted to stereotyped loading regimes than those of Otolemur.

DISCUSSION

The results suggest that the calcaneus of specialized leapers is adapted to more stereotyped loading patterns. The lack of predicted bone strength differences between Galago and Otolemur may be related to body size differences between these taxa, or it may indicate that loads encountered by Galago during naturalistic leaping are not reflected in the available experimental force data.

Histovariability in human clavicular cortical bone microstructure and its mechanical implications

The human clavicle (i.e. collarbone) is an unusual long bone due to its signature S-shaped curve and variability in macrostructure observed between individuals. Because of the complex nature of how the upper limb moves, as well as due to its complex musculoskeletal arrangement, the biomechanics, in particular the mechanical loadings, of the clavicle are not fully understood. Given that bone remodeling can be influenced by bone stress, the histologic organization of Haversian bone offers a hypothesis of responses to force distributions experienced across a bone. Furthermore, circularly polarized light microscopy can be used to determine the orientation of collagen fibers, providing additional information on how bone matrix might organize to adapt to direction of external loads. We examined Haversian density and collagen fiber orientation, along with cross-sectional geometry, to test whether the clavicle midshaft shows unique adaptation to atypical load-bearing when compared with the sternal (medial) and acromial (lateral) shaft regions. Because fractures are most common at the midshaft, we predicted that the cortical bone structure would show both disparities in Haversian remodeling and nonrandomly oriented collagen fibers in the midshaft compared with the sternal and acromial regions. Human clavicles (n = 16) were sampled via thin-sections at the sternal, middle, and acromial ends of the shaft, and paired sample t-tests were employed to evaluate within-individual differences in microstructural or geometric properties. We found that Haversian remodeling is slightly but significantly reduced in the middle of the bone. Analysis of collagen fiber orientation indicated nonrandom fiber orientations that are overbuilt for tensile loads or torsion but are poorly optimized for compressive loads throughout the clavicle. Geometric properties of percent bone area, polar second moment of area, and shape (I_max /I_min ) confirmed the conclusions drawn by existing research on clavicle macrostructure. Our results highlight that mediolateral shape changes might be accompanied by slight changes in Haversian density, but bone matrix organization is predominantly adapted to resisting tensile strains or torsion throughout and may be a major factor in the risk of fracture when experiencing atypical compression.

Evaluation of Articular Surface Similarity of Hemi-Hamate Grafts and Proximal Middle Phalanx Morphology: A 3D Geometric Morphometric Approach

PURPOSE

Hemi-hamate arthroplasty has been described as a viable treatment option for unstable proximal interphalangeal joint fracture-dislocations. The procedure uses a dorsal distal hamate osteochondral graft to recreate the injured volar middle phalanx (MP) proximal base. The purpose of this study was to evaluate the similarity in shape of these articular surfaces using quantitative 3-dimensional methods.

METHODS

Three-dimensional virtual renderings were created from laser scans of the articular surfaces of the dorsal distal hamate and the volar MP bases of the index, middle, ring, and little fingers from cadaveric hands of 25 individuals. Three-dimensional landmarks were obtained from the articular surfaces of each bone and subjected to established geometric morphometric analytical approaches to quantify shape. For each individual, bone shapes were evaluated for covariation using 2-block partial least-squares and principal component analyses.

RESULTS

No statistically significant covariation was found between the dorsal distal hamate and volar MP bases of the middle, ring, or little digits. Whereas the volar MP bases demonstrated relative morphologic uniformity among the 4 digits both within and between individuals, the dorsal distal hamates exhibited notable variation in articular surface morphology.

CONCLUSIONS

Despite the early to midterm clinical success of hemi-hamate arthroplasty, there is no statistically significant, uniform similarity in shape between the articular surfaces of the dorsal distal hamate and the volar MP base. In addition, there is wide variation in the articular morphology of the hamate among individuals.

CLINICAL RELEVANCE

The lack of uniform similarity in shape between the dorsal distal hamate and the volar MP base may result in unpredictable outcomes in HHA. It is recommended that the variation in hamate morphology be considered while reconstructing the injured volar MP base in the procedure.

Effects of selective breeding for high voluntary wheel-running behavior on femoral nutrient canal size and abundance in house mice

Bone modeling and remodeling are aerobic processes that entail relatively high oxygen demands. Long bones receive oxygenated blood from nutrient arteries, epiphyseal-metaphyseal arteries, and periosteal arteries, with the nutrient artery supplying the bulk of total blood volume in mammals (~ 50-70%). Estimates of blood flow into these bones can be made from the dimensions of the nutrient canal, through which nutrient arteries pass. Unfortunately, measuring these canal dimensions non-invasively (i.e. without physical sectioning) is difficult, and thus researchers have relied on more readily visible skeletal proxies. Specifically, the size of the nutrient artery has been estimated from dimensions (e.g. minimum diameters) of the periosteal (external) opening of the nutrient canal. This approach has also been utilized by some comparative morphologists and paleontologists, as the opening of a nutrient canal is present long after the vascular soft tissue has degenerated. The literature on nutrient arteries and canals is sparse, with most studies consisting of anatomical descriptions from surgical proceedings, and only a few investigating the links between nutrient canal morphology and physiology or behavior. The primary objective of this study was to evaluate femur nutrient canal morphology in mice with known physiological and behavioral differences; specifically, mice from an artificial selection experiment for high voluntary wheel-running behavior. Mice from four replicate high runner (HR) lines are known to differ from four non-selected control (C) lines in both locomotor and metabolic activity, with HR mice having increased voluntary wheel-running behavior and maximal aerobic capacity (VO₂ max) during forced treadmill exercise. Femora from adult mice (average age 7.5 months) of the 11th generation of this selection experiment were μCT-scanned and three-dimensional virtual reconstructions of nutrient canals were measured for minimum cross-sectional area as a skeletal proxy of blood flow. Gross observations revealed that nutrient canals varied far more in number and shape than prior descriptions would indicate, regardless of sex or genetic background (i.e. HR vs. C lines). Canals adopted non-linear shapes and paths as they traversed from the periosteal to endosteal borders through the cortex, occasionally even branching within the cortical bone. Additionally, mice from both HR and C lines averaged more than four nutrient canals per femur, in contrast to the one to two nutrient canals described for femora from rats, pigs, and humans in prior literature. Mice from HR lines had significantly larger total nutrient canal area than C lines, which was the result not of an increase in the number of nutrient canals, but rather an increase in their average cross-section size. This study demonstrates that mice with an evolutionary history of increased locomotor activity and maximal aerobic metabolic rate have a concomitant increase in the size of their femoral nutrient canals. Although the primary determinant of nutrient canal size is currently not well understood, the present results bolster use of nutrient canal size as a skeletal indicator of aerobically supported levels of physical activity in comparative studies.

Ontogeny of hallucal metatarsal rigidity and shape in the rhesus monkey (Macaca mulatta) and chimpanzee (Pan troglodytes)

Life history variables including the timing of locomotor independence, along with changes in preferred locomotor behaviors and substrate use during development, influence how primates use their feet throughout ontogeny. Changes in foot function during development, in particular the nature of how the hallux is used in grasping, can lead to different structural changes in foot bones. To test this hypothesis, metatarsal midshaft rigidity [estimated from the polar second moment of area (J) scaled to bone length] and cross-sectional shape (calculated from the ratio of maximum and minimum second moments of area, Imax /Imin ) were examined in a cross-sectional ontogenetic sample of rhesus macaques (Macaca mulatta; n = 73) and common chimpanzees (Pan troglodytes; n = 79). Results show the hallucal metatarsal (Mt1) is relatively more rigid (with higher scaled J-values) in younger chimpanzees and macaques, with significant decreases in relative rigidity in both taxa until the age of achieving locomotor independence. Within each age group, Mt1 rigidity is always significantly higher in chimpanzees than macaques. When compared with the lateral metatarsals (Mt2-5), the Mt1 is relatively more rigid in both taxa and across all ages; however, this difference is significantly greater in chimpanzees. Length and J scale with negative allometry in all metatarsals and in both species (except the Mt2 of chimpanzees, which scales with positive allometry). Only in macaques does Mt1 midshaft shape significantly change across ontogeny, with older individuals having more elliptical cross-sections. Different patterns of development in metatarsal diaphyseal rigidity and shape likely reflect the different ways in which the foot, and in particular the hallux, functions across ontogeny in apes and monkeys.

Subchondral Bone Radiodensity Patterns in the Glenoid Fossa of Ape and Human Scapulae

Regions of denser subchondral bone deep to a joint's articular surface indicate locations where the joint experiences relatively higher or more frequent compressive trans-articular forces than less dense regions. Human clinically focused studies have hypothesized that regional variation of acquired with computed tomography osteoabsorptiomety (CT-OAM), in the scapular glenoid fossa (GF) is specifically related to forces arising from everyday rotator cuff muscle function. We test this hypothesis by investigating the relationship between rotator cuff function and GF HiRD subchondral bone patterns in a broader comparative context. CT-OAM was used on scapulae of chimpanzees, gibbons and humans to visualize HiRD subchondral bone patterns and assess regional (anterior-posterior; superior-inferior) differences in HiRD concentrations within each group. Like patterns observed in humans, ape GFs show HiRD concentrations in anterior, posterior and superior regions. Gibbons exhibit significantly larger concentrations anteriorly, probably serving as a skeletal correlate of increased subscapularis activity during humeral internal rotation during arm-swinging locomotion. Chimpanzees exhibit relatively larger areas posteriorly (though not statistically significant), conceivably serving as a correlate of increased infraspinatus activity during humeral external rotation and retraction during knuckle-walking. All groups show relatively larger HiRD areas superiorly, likely correlating with forceful humeral abduction (rather than adduction) during routine upper limb use across behaviors. Subchondral bone HiRD patterns in the GF appear to correspond with normal and unbalanced rotator cuff activity and force production not only in humans, but also in other primates, thereby corroborating their value in human clinical studies and functional morphology research. Anat Rec, 301:776-785, 2018. © 2017 Wiley Periodicals, Inc.

New sivaladapid primate from Lower Siwalik deposits surrounding Ramnagar (Jammu and Kashmir State), India

Over the past century, numerous vertebrate fossils collected near the town of Ramnagar, India, have proven to be important for understanding the evolution and biogeography of many mammalian groups. Primates from Ramnagar, though rare, include a number of hominoid specimens attributable to Sivapithecus, as well as a single published mandibular fragment preserving the P₄-M₁ of the Miocene adapoid Sivaladapis palaeindicus. Since 2010, we have renewed fossil prospecting in the Lower Siwalik deposits near Ramnagar in an attempt to better understand the evolution, biogeographic timing, and paleoclimatic context of mammalian radiations in Asia, with a particular focus on primates. Our explorations have resulted in the identification of new fossil localities, including the site of Sunetar. The age of Sunetar and the Ramnagar region, in general, is tentatively dated between 14 and 11 Ma. In 2014, a partial right mandible of a sivaladapid primate was recovered at Sunetar, preserving the corpus with P₄ roots and worn M₁-M₃ dentition. Although sivaladapids are known by numerous specimens of two genera (Sivaladapis and Indraloris) at Lower Siwalik sites on the Potwar Plateau (Pakistan) and at the Middle Siwalik locality of Haritalyangar (India), this new specimen is just the second sivaladapid recovered from the Ramnagar region. Our analyses suggest that the new specimen is distinct from all other sivaladapids, and we therefore describe it as a new genus and species close to the base of the Sivaladapinae.

Mucosal serotonin overflow is associated with colonic stretch rather than phasic contractions

BACKGROUND

Many studies have shown that mucosal serotonin (5-HT) is associated with motility, however, recently there have been some questions to the precise role of this transmitter. The majority of studies have focused on understanding the role of mucosal 5-HT on colonic migratory motor complexes, but very few studies have been carried out to understand how 5-HT release may be associated with other motility patterns.

METHODS

Using distal colon segments from C57BL/6J mice, mucosal 5-HT overflow was monitored using amperometry while applying tension in longitudinal or circular directions to stretch the tissue.

KEY RESULTS

Phasic and basal 5-HT levels were not associated with the strength of phasic contractions, while being altered using scopolamine and L-NNA. There was a significant increase in mucosal 5-HT with longitudinal and circular muscle stretch. A greater applied force was needed to activate 5-HT release in the circular muscle. In the longitudinal muscle, 5-HT levels increased with stretch until 3 mN, after which the levels returned back to baseline. This stretch-evoked 5-HT overflow was inhibited by transient receptor potential A1 (TRPA1) agonist, 30 μM ruthenium red in both circular and longitudinal muscle preparations. The decreased 5-HT overflow after 3 mN of tension was reversed using a 5-HT4 antagonist 100 nM GR113808.

CONCLUSIONS & INFERENCES

Our findings show a relationship between colonic stretch and mucosal 5-HT overflow, while no relationship is observed with phasic colonic contractions. Such findings provide more insight into the role of mucosal 5-HT in influencing the pattern of colonic motility to diversify fecal propulsion.

Management of root-knot nematode (Meloidogyne incognita) in bottle gourd using different botanicals in pots

A pot experiment was conducted to study the efficacy of different botanicals in varying doses for management of root-knot nematode, M. incognita in bottle gourd. The results exhibited that madar (Calotropis procera) and neem (Azadirachta indica) leaves application proved to be more effective in improving plant growth characters and reducing root-knot index and final nematode population. Among the doses tested, higher dose of 1.5 % (w/w) was more effective than lower ones.

Mucosal adenosine triphosphate mediates serotonin release from ileal but not colonic guinea pig enterochromaffin cells

BACKGROUND

Mechanical stimulation of the mucosal epithelium results in increased serotonin (5-HT) release from enterochromaffin (EC) cells. Little is known about how this process varies in different regions of the intestinal tract; however, purines are felt to play a role. We studied the relationship between mechanical stimulation, adenosine triphosphate (ATP), and 5-HT release from ileal and colonic mucosal tissue.

METHODS

Amperometric recordings of ATP and 5-HT were carried out using an ATP biosensor and boron-doped diamond microelectrode. Levels of extracellular ATP and 5-HT were monitored using high performance liquid chromatography.

KEY RESULTS

Under basal conditions, 5-HT levels were significantly decreased in the ileum (p < 0.001) but not the colon in the presence of the P2 antagonist suramin (100 μM). Ecto-ATPase inhibitor ARL67156 (10 μM) elevated ATP levels in the ileum and colon (both p < 0.001), but only 5-HT levels in the ileum (p < 0.001). Exogenous ATP increased 5-HT release in the presence of tetrodotoxin in the ileum (p < 0.001), but had not effect in the colon. Mechanical stimulation increased levels of 5-HT in the ileum (p < 0.001) and colon (p < 0.01), but levels returned to baseline in the presence of suramin and MRS2179 in the ileum. The onset of 5-HT release was delayed following mechanical stimulation. The rise time of the ATP response was quicker than that of 5-HT during mechanical stimulation.

CONCLUSIONS & INFERENCES

During mechanical stimulation of the mucosal epithelium, ATP mediates 5-HT release from EC cells in the ileum, but not the colon. Mucosal 5-HT signaling following mechanical stimulation is varied in different regions of the intestinal tract.

Ontogenetic scaling of fore- and hind limb posture in wild chacma baboons (Papio hamadryas ursinus)

Large-scale interspecific studies of mammals ranging between 0.04–280 kg have shown that larger animals walk with more extended limb joints. Within a taxon or clade, however, the relationship between body size and joint posture is less straightforward. Factors that may affect the lack of congruence between broad and narrow phylogenetic analyses of limb kinematics include limited sampling of (1) ranges of body size, and/or (2) numbers of individuals. Unfortunately, both issues are inherent in laboratory-based or zoo locomotion research. In this study, we examined the relationship between body mass and elbow and knee joint angles (our proxies of fore- and hind limb posture, respectively) in a cross-sectional ontogenetic sample of wild chacma baboons (Papio hamadryas ursinus) habituated in the De Hoop Nature Reserve, South Africa. Videos were obtained from 33 individuals of known age (12 to ≥108 months) and body mass (2–29.5 kg) during walking trials. Results show that older, heavier baboons walk with significantly more extended knee joints but not elbow joints. This pattern is consistent when examining only males, but not within the female sample. Heavier, older baboons also display significantly less variation in their hind limb posture compared to lighter, young animals. Thus, within this ontogenetic sample of a single primate species spanning an order of magnitude in body mass, hind limb posture exhibited a postural scaling phenomenon while the forelimbs did not. These findings may further help explain 1) why younger mammals (including baboons) tend to have relatively stronger bones than adults, and 2) why humeri appear relatively weaker than femora (in at least baboons). Finally, this study demonstrates how field-acquired kinematics can help answer fundamental biomechanical questions usually addressed only in animal gait laboratories.

Changes in the innervation of the mouse internal anal sphincter during aging

BACKGROUND

The innervation of the mouse internal anal sphincter (IAS) has been little studied, and how it changes during aging has not previously been investigated. The aim of this study was therefore to characterize the distribution and density of subtypes of nerve fibers in the IAS and underlying mucosa in 3-, 12- to 13-, 18- and 24- to 25-month-old male C57BL/6 mice.

METHODS

Nerve fibers were immunolabeled with antibodies against protein gene product 9.5 (PGP9.5), neuronal nitric oxide synthase (nNOS), vasoactive intestinal polypeptide (VIP), substance P (SP), calcitonin gene-related peptide (CGRP), and calretinin (CR). Immunoreactivity in nerve fibers in the circular muscle and mucosa was quantified using Image J software.

KEY RESULTS

In young adult (3 month) mice, nNOS-immunoreactive (IR) nerve fibers were densely distributed in the circular muscle, but relatively few in the mucosa; VIP-IR nerve fibers were abundant in the circular muscle and common in the mucosa; SP-IR nerve fibers were common in circular muscle and mucosa; CGRP- and CR-IR nerve fibers were dense in mucosa and sparse in circular muscle. The density of PGP9.5 immunoreactivity (IRY) was not significantly reduced with age, but a significant reduction in nNOS-IRY and SP-IRY with age was found in the IAS circular muscle. Neuronal nitric oxide synthase-, VIP-, and SP-IRY in the anal mucosa were significantly reduced with age. CGRP-IRY in both circular muscle and mucosa was increased in 18-month-old animals.

CONCLUSIONS & INFERENCES

The density of immunoreactivity of markers for some types of IAS nerve fibers decreases during aging, which may contribute to age-related ano-rectal dysfunction.

Visceral hypersensitivity in female but not in male serotonin transporter knockout rats

BACKGROUND

Visceral hypersensitivity occurs in irritable bowel syndrome (IBS), particularly in women. Serotonin signaling, including reduced serotonin transporter (SERT) expression, may be disrupted in IBS patients. We studied SERT gene knockout (KO) rats to determine if they exhibited sex-related alterations in visceral sensitivity.

METHODS

We measured serotonin in the colonic mucosa using HPLC and amperometric microelectrode techniques. Visceral sensitivity was assessed using the electromyographic visceromotor response (VMR) in response to colorectal balloon distention (CRD). We studied the electrophysiologic properties of colon projecting sensory neurons in vitro using whole-cell recordings.

KEY RESULTS

Mucosal serotonin levels were not different among male and female WT and SERT KO rats. Serotonin oxidation currents in vitro were larger (P < 0.05) in tissues from male and female SERT KO compared with WT rats. Oxidation currents in male and female WT, but not SERT KO, rats were increased (P < 0.05) by the SERT inhibitor fluoxetine (1 μmol L(-1) ). The VMR to CRD was increased in female but not in male SERT KO rats (P < 0.05); this response varied with the estrous cycle. Colon projecting sensory neurons from female SERT KO rats fired more action potentials compared with neurons from female WT rats. There were no differences in action potential firing in neurons from male WT and SERT KO rats.

CONCLUSIONS & INFERENCES

Increased colonic extracellular serotonin in female SERT KO rats is associated with visceral hypersensitivity and hyperexcitability of colon projecting sensory neurons. The SERT KO rat is a model for studying interactions between serotonin, sex and visceral sensation.

Joint loads in marsupial ankles reflect habitual bipedalism versus quadrupedalism

Joint surfaces of limb bones are loaded in compression by reaction forces generated from body weight and musculotendon complexes bridging them. In general, joints of eutherian mammals have regions of high radiodensity subchondral bone that are better at resisting compressive forces than low radiodensity subchondral bone. Identifying similar form-function relationships between subchondral radiodensity distribution and joint load distribution within the marsupial postcranium, in addition to providing a richer understanding of marsupial functional morphology, can serve as a phylogenetic control in evaluating analogous relationships within eutherian mammals. Where commonalities are established across phylogenetic borders, unifying principles in mammalian physiology, morphology, and behavior can be identified. Here, we assess subchondral radiodensity patterns in distal tibiae of several marsupial taxa characterized by different habitual activities (e.g., locomotion). Computed tomography scanning, maximum intensity projection maps, and pixel counting were used to quantify radiodensity in 41 distal tibiae of bipedal (5 species), arboreal quadrupedal (4 species), and terrestrial quadrupedal (5 species) marsupials. Bipeds (Macropus and Wallabia) exhibit more expansive areas of high radiodensity in the distal tibia than arboreal (Dendrolagus, Phascolarctos, and Trichosurus) or terrestrial quadrupeds (Sarcophilus, Thylacinus, Lasiorhinus, and Vombatus), which may reflect the former carrying body weight only through the hind limbs. Arboreal quadrupeds exhibit smallest areas of high radiodensity, though they differ non-significantly from terrestrial quadrupeds. This could indicate slightly more compliant gaits by arboreal quadrupeds compared to terrestrial quadrupeds. The observed radiodensity patterns in marsupial tibiae, though their statistical differences disappear when controlling for phylogeny, corroborate previously documented patterns in primates and xenarthrans, potentially reflecting inferred limb use during habitual activities such as locomotion. Despite the complex nature of factors contributing to joint loads, broad observance of these patterns across joints and across a variety of taxa suggests that subchondral radiodensity can be used as a unifying form-function principle within Mammalia.

New primate first metatarsals from the Paleogene of Egypt and the origin of the anthropoid big toe

The specialized grasping feet of primates, and in particular the nature of the hallucal grasping capabilities of living strepsirrhines and tarsiers (i.e., 'prosimians'), have played central roles in the study of primate origins. Prior comparative studies of first metatarsal (Mt1) morphology have documented specialized characters in living prosimians that are indicative of a more abducted hallux, which in turn is often inferred to be related to an increased ability for powerful grasping. These include a well-developed peroneal process and a greater angle of the proximal articular surface relative to the long axis of the diaphysis. Although known Mt1s of fossil prosimians share these characters with living non-anthropoid primates, Mt1 morphology in the earliest crown group anthropoids is not well known. Here we describe two Mt1s from the Fayum Depression of Egypt - one from the latest Eocene (from the ∼34 Ma Quarry L-41), and one from the later early Oligocene (from the ∼29-30 Ma Quarry M) - and compare them with a sample of extant and fossil primate Mt1s. Multivariate analyses of Mt1 shape variables indicate that the Fayum specimens are most similar to those of crown group anthropoids, and likely belong to the stem catarrhines Catopithecus and Aegyptopithecus specifically, based on analyses of size. Also, phylogenetic analyses with 16 newly defined Mt1 characters support the hypotheses that "prosimian"-like Mt1 features evolved along the primate stem lineage, while crown anthropoid Mt1 morphology and function is derived among primates, and likely differed from that of basal stem anthropoids. The derived loss of powerful hallucal grasping as reflected in the Mt1 morphology of crown anthropoids may reflect long-term selection for improved navigation of large-diameter, more horizontal branches at the expense of movement in smaller, more variably inclined branches in the arboreal environment.

Electromyography of wrist and finger flexor muscles in olive baboons (Papio anubis)

Some non-human primates use digitigrade hand postures when walking slowly on the ground. As a component of an extended limb, a digitigrade posture can help minimize wrist joint moments thereby requiring little force production directly from wrist flexors (and/or from the assistance of finger flexors) to maintain limb posture. As a consequence, less active muscle volume would be required from these anti-gravity muscles and overall metabolic costs associated with locomotion could be reduced. To investigate whether the use of digitigrade hand postures during walking in primates entails minimal use of anti-gravity muscles, this study examined electromyography (EMG) patterns in both the wrist and finger flexor muscles in facultatively digitigrade olive baboons (Papio anubis) across a range of speeds. The results demonstrate that baboons can adopt a digitigrade hand posture when standing and moving at slow speeds without requiring substantial EMG activity from distal anti-gravity muscles. Higher speed locomotion, however, entails increasing EMG activity and is accompanied by a dynamic shift to a more palmigrade-like limb posture. Thus, the ability to adopt a digitigrade hand posture by monkeys is an adaptation for ground living, but it was never co-opted for fast locomotion. Rather, digitigrady in primates appears to be related to energetic efficiency for walking long distances.

Electroanalytical approaches to study signaling mechanisms in the gastrointestinal tract

Electroanalytical techniques over the past few years have been applied to study real-time release of various signaling molecules in the GI tract. These approaches have become highly attractive as they provide dynamic spatial information on the amount of signaling molecules released. Although these approaches are relatively new to the field, the studies to date have provided useful insights into the alterations in signaling mechanisms during maturation, obesity and in a model of colitis. New methods and techniques have also allowed the possibility to obtain information on the signaling process and future developments will provide a wide diverse array of information that will be of benefit to all researchers in the field of gastroenterology. This review focuses on the types of techniques utilized, the information they can provide, their potential advantages and disadvantages in monitoring signaling processes in the gastrointestinal tract, the existing scientific studies that have utilized electroanalytical methods to date and the future potential impact of such approaches.

Dynamic pressure patterns in the hands of olive baboons (Papio anubis) during terrestrial locomotion: implications for cercopithecoid primate hand morphology

Habitually terrestrial monkeys adopt digitigrade hand postures at slow speeds to increase effective forelimb length and reduce distal limb joint moments. As these primates move faster, however, their hands transition to a more palmigrade posture, which is likely associated with the inability of wrist and hand joints to resist higher ground reaction forces (GRF) associated with faster speeds. Transitioning to a palmigrade posture may serve to distribute GRFs over a larger surface area (i.e., increased palmar contact), ultimately reducing stresses in fragile hand bones. To test this hypothesis, dynamic palmar pressure data were collected on two adult baboons (Papio anubis) walking, running, and galloping across a runway integrated with a dynamic pressure mat (20 steps each; speed range: 0.46-4.0 m/s). Peak GRF, contact area, peak pressure, and pressure-time integral were quantified in two regions of the hand: fingers and palms (including metacarpal heads). At slower speeds with lower GRFs, the baboons use digitigrade postures resulting in small palmar contact area (largely across the metacarpal heads). At faster speeds with higher GRFs, they used less digitigrade hand postures resulting in increased palmar contact area. Finger contact area did not change across speeds. Despite higher GRFs at faster speeds, metacarpal pressure was moderated across speeds due to increased palmar contact area as animals transitioned from digitigrady to palmigrady. In contrast, the pressure in the fingers increased with faster speeds. Results indicate that the transition from digitigrady to palmigrady distributes increased forces over a larger palmar surface area. Such dynamic changes in palmar pressure likely moderate strain in the gracile bones of the hand, a structure that is integral not only for locomotion, but also feeding and social behaviors in primates.

The interplay between speed, kinetics, and hand postures during primate terrestrial locomotion

Nonprimate terrestrial mammals may use digitigrade postures to help moderate distal limb joint moments and metapodial stresses that may arise during high-speed locomotion with high-ground reaction forces (GRF). This study evaluates the relationships between speed, GRFs, and distal forelimb kinematics in order to evaluate if primates also adopt digitigrade hand postures during terrestrial locomotion for these same reasons. Three cercopithecine monkey species (Papio anubis, Macaca mulatta, Erythrocebus patas) were videotaped moving unrestrained along a horizontal runway instrumented with a force platform. Three-dimensional forelimb kinematics and GRFs were measured when the vertical force component reached its peak. Hand posture was measured as the angle between the metacarpal segment and the ground (MGA). As predicted, digitigrade hand postures (larger MGA) are associated with shorter GRF moment arms and lower wrist joint moments. Contrary to expectations, individuals used more palmigrade-like (i.e. less digitigrade) hand postures (smaller MGA) when the forelimb was subjected to higher forces (at faster speeds) resulting in potentially larger wrist joint moments. Accordingly, these primates may not use their ability to alter their hand postures to reduce rising joint moments at faster speeds. Digitigrady at slow speeds may improve the mechanical advantage of antigravity muscles crossing the wrist joint. At faster speeds, greater palmigrady is likely caused by joint collapse, but this posture may be suited to distribute higher GRFs over a larger surface area to lower stresses throughout the hand. Thus, a digitigrade hand posture is not a cursorial (i.e. high speed) adaptation in primates and differs from that of other mammals.