Ulnar shape of extant primates: Functional signals and covariation with triquetrum shape.

OBJECTIVES: In this study, we investigated the shape differences of the distal ulna in a phylogenetic context among a broad range of primate taxa. Furthermore, we evaluated covariation between ulnar and triquetrum shape and a possible association between ulnar shape and locomotor behavior. MATERIALS AND METHODS: We applied 3D geometric morphometrics on a large dataset comprising the distal ulna of 124 anthropoid primate specimens belonging to 12 different genera. For each species, a mean shape was calculated using 11 Procrustes-aligned surface landmarks on the distal ulna. These mean shapes are used in a bgPCA, pPCA, and PACA and 3D morphs were used to visualize more subtle differences between taxa. A p2B-PLS analysis was performed to test the covariance between distal ulnar and triquetrum shape. RESULTS: The results show that more closely related species exhibit a similar distal ulnar shape. Overall, extant hominid ulnae show a shape shift compared to those of extant monkeys and hylobatids. This includes a shortening of the ulnar styloid process and dorspalmarly widening of the ulnar head, shape characteristics that are independent of phylogeny. Within the hominids, Pongo pygmaeus seem to possess the most plesiomorphic distal ulnar shape, while Gorilla and Homo sapiens display the most derived distal ulna. Cercopithecoids, hylobatids, and P. pygmaeus are characterized by a relatively deep ECU groove, which is a shape trait dependent of phylogeny. Although there was no significant covariation between distal ulnar shape and triquetrum shape, the shape differences of the distal ulna between the different primate taxa reveal a possible link with locomotor behavior. CONCLUSIONS: The comparative analyses of this study reveal different shape trends in a phylogenetic context. Highly arboreal primates, such as hylobatids and Ateles fusciceps, show a distal ulnar morphology that appears to be adapted to tensile and torsional forces. In primates that use their wrist under more compressive conditions, such as quadrupedal cercopithecoids and great apes, the distal ulnar morphology seems to reflect increased compressive forces. In modern humans, the distal ulnar shape can be associated to enhanced manipulative skills and power grips. There was no significant covariation between distal ulnar shape and triquetrum shape, probably due to the variation in the amount of contact between the triquetrum and ulna. In combination with future research on wrist mobility in diverse primate taxa, the results of this study will allow us to establish form-function relationships of the primate wrist and contribute towards an evidence-based interpretation of fossil remains.

The co-benefits of biodiversity citizen science for well-being and nature relatedness.

Human well-being is dependent on the health of our planet. Biodiversity-related citizen science supports conservation research, and there is increasing interest in its potential as a health co-benefits intervention. This randomized controlled study investigates the health co-benefits of biodiversity citizen science participation. Seventy participants were randomly assigned to a citizen science project or control group for an 8-month period. Both groups completed pre- and post-intervention surveys, evaluating nature relatedness, self-efficacy related to biodiversity loss, subjective well-being, and climate change anxiety. A subset (N = 13) of participants engaged in the citizen science project also took part in focus group discussions. The intervention group reported a significant increase in nature relatedness and self-efficacy to help address issues of biodiversity loss. Although no significant changes were observed for other well-being or anxiety scales, most participants reported positive outcomes related to mental or physical well-being in focus groups. There were stronger positive effects for participants without previous environmental volunteering experience. These results suggest that citizen science participation has the potential to contribute to Planetary Health goals, with sustained co-benefits for well-being and nature relatedness. Future interventions evaluating co-benefits should consider previous environmental volunteering experience and focus on participants with little experience to maximize health outcomes.

Covariation between wrist bone morphology and maximal range of motion during ulnar deviation and supination in extant nonhuman primate taxa.

This study investigates the maximal range of motion (ROM) during wrist deviation and forearm rotation for five different primate genera and the possible correlation with the shape of the distal ulna, triquetrum and hamate. A two-block phylogenetic partial least square analysis was performed to test this covariation in a phylogenetic context, using shape coordinates and a matrix of maximal ROM data as input data. The results show that gibbons have the highest ROM for both ulnar deviation and supination, whereas Macaca exhibited the lowest ROM for supination, and Pan had the lowest ROM for ulnar deviation. These results can be attributed to differences in locomotor behaviour, as gibbons need a large wrist mobility in all directions for their highly arboreal lifestyle, whereas Macaca and Pan need a stable wrist during terrestrial locomotion. However, we found no correlation between distal ulna/triquetrum/hamate shape and maximal ROM during ulnar deviation and supination in the different primate taxa. A larger dataset, in combination with behavioural and biomechanical studies, is needed to establish form-function relationships of the primate hand, which will aid the functional interpretation of primate fossil remains.

Acute exposure to high temperature affects expression of heat shock proteins in altricial avian embryos.

As the world warms, understanding the fundamental mechanisms available to organisms to protect themselves from thermal stress is becoming ever more important. Heat shock proteins are highly conserved molecular chaperones which serve to maintain cellular processes during stress, including thermal extremes. Developing animals may be particularly vulnerable to elevated temperatures, but the relevance of heat shock proteins for developing altricial birds exposed to a thermal stressor has never been investigated. Here, we sought to test whether three stress-induced genes - HSPD1, HSPA2, HSP90AA1 - and two constitutively expressed genes - HSPA8, HSP90B1 - are upregulated in response to acute thermal shock in zebra finch (Taeniopygia guttata) embryos half-way through incubation. Tested on a gradient from 37.5 °C (control) to 45 °C, we found that all genes, except HSPD1, were upregulated. However, not all genes initiated upregulation at the same temperature. For all genes, the best fitting model included a correlate of developmental stage that, although it was never significant after multiple-test correction, hints that heat shock protein upregulation might increase through embryonic development. Together, these results show that altricial avian embryos are capable of upregulating a known protective mechanism against thermal stress, and suggest that these highly conserved cellular mechanisms may be a vital component of early developmental protection under climate change.

Functional signals and covariation in triquetrum and hamate shape of extant primates using 3D geometric morphometrics.

In this study, we want to investigate the covariation in the shape of two carpal bones, the triquetrum and hamate, and the possible association with locomotor behavior in a broad range of primate taxa. We applied 3D Geometric Morphometrics on a large data set comprising 309 anthropoid primates of 12 different genera. Principal component analyses were performed on the covariance matrix of 18 (triquetrum) and 23 (hamate) Procrustes-aligned surface landmarks. A two-block partial least square analysis was done to test the covariance between triquetrum and hamate shape, without relying on the predictive models implicit in regression analyses. The results show that the carpal shape of quadrupedal anthropoids, which mainly use their wrist under compressive conditions, differs from that of suspensory primates as their wrist is possibly subjected to tensile and torsional forces. Within the hominids, differences in shape also distinguish more terrestrial from more arboreal species. Even within the great apes, we are able to capture shape differences between species of the same genus. In combination with behavioral and biomechanical studies, the results of this research can be used to establish form-function relationships of the primate hand which will aid the functional interpretation of primate fossil remains.

The forearm and hand musculature of semi-terrestrial rhesus macaques (Macaca mulatta) and arboreal gibbons (fam.Hylobatidae). Part II. Quantitative analysis.

Nonhuman primates have a highly diverse locomotor repertoire defined by an equally diverse hand use. Based on how primates use their hands during locomotion, we can distinguish between terrestrial and arboreal taxa. The 'arboreal' hand is likely adapted towards high wrist mobility and grasping, whereas the 'terrestrial' hand will show adaptations to loading. While the morphology of the forearm and hand bones have been studied extensively, functional adaptations in the forearm and hand musculature to locomotor behaviour have been documented only scarcely. In this paper, we investigate the forelimb musculature of the highly arboreal gibbons (including Hylobates lar,Hylobates pileatus,Nomascus leucogenys,Nomascus concolor and Symphalangus syndactylus) and compare this with the musculature of the semi-terrestrial rhesus macaques (Macaca mulatta). Anatomical data from previous dissections on knuckle-walking bonobos (Pan paniscus) and bipedal humans (Homo sapiens) are also included to further integrate the analyses in the scope of catarrhine hand adaptation. This study indicates that the overall configuration of the arm and hand musculature of these primates is very similar but there are some apparent differences in relative size which can be linked to differences in forelimb function and which might be related to their specific locomotor behaviour. In macaques, there is a large development of wrist deviators, wrist and digital flexors, and m. triceps brachii, as these muscles are important during the different phases of palmi- and digitigrade quadrupedal walking to stabilize the wrist and elbow. In addition, their m. flexor carpi ulnaris is the most important contributor to the total force-generating capacity of the wrist flexors and deviators, and is needed to counteract the adducting torque at the elbow joint during quadrupedal walking. Gibbons show a relatively high force-generating capacity in their forearm rotators, wrist and digital flexors, which are important muscles in brachiation to actively regulate forward movement of the body. The results also stress the importance of the digital flexors in bonobos, during climbing and clambering, and in humans, which is likely linked to our advanced manipulation skills.

Three-dimensional geometric morphometric analysis of the first metacarpal distal articular surface in humans, great apes and fossil hominins.

Understanding the manual abilities of fossil hominins has been a focus of palaeoanthropological research for decades. Of interest are the morphological characteristics of the thumb due to its fundamental role in manipulation, particularly that of the trapeziometacarpal joint. Considerably less attention has been given to the thumb metacarpophalangeal (MCP) joint, which plays a role in stabilizing the thumb during forceful grasps and precision pinching. In this study we use a three-dimensional geometric morphometric approach to quantify the shape of the first metacarpal head in extant hominids (Homo, Pan, Gorilla and Pongo) and six fossil hominin species (Homo neanderthalensis Tabun C1 and La Chappelle-aux-Saints, Homo naledi U.W. 101-1282, Australopithecus sediba MH2, Paranthropus robustus/early Homo SK84, Australopithecus africanus StW 418, Australopithecus afarensis A.L. 333w-39), with the aims of identifying shapes that may be correlated with human-like forceful opposition and determining if similar morphologies are present in fossil hominins. Results show that humans differ from extant great apes by having a distally flatter articular surface, larger epicondyle surface area, and a larger radial palmar condyle. We suggest that this suite of features is correlated with a lower range of motion at the MCP joint, which would enhance the thumbs ability to resist the elevated loads associated with the forceful precision grips typical of humans. Great ape genera are each differentiated by distinctive morphological features, each of which is consistently correlated with the predicted biomechanical demands of their particular locomotor and/or manipulatory habits. Neanderthals and U.W. 101-1282 fall within the modern human range of variation, StW 418, SK 84 and U.W. 88-119 fall in between humans and great apes, and A.L. 333w-39 falls within Pan variation. These results agree with those of traditional linear analyses while providing a more comprehensive quantitative basis from which to interpret the hand functional morphology of extinct hominins.