Fluctuating Asymmetry and Stress in Macaca fuscata: Does Captivity Affect Morphology?

Fluctuating Asymmetry (FA) in morphology is used as a proxy for developmental instability in response to stress factors. FA has important implications for understanding the impact of differential environments and stressors on the skeletal phenotype. Here, we explore FA in the mandibular morphology of wild and captive Macaca fuscata to detect differences induced by the captive environment. We use two different approaches in Geometric Morphometrics to characterise the degree and patterns of FA and Directional Asymmetry (DA) based on 3D mandibular landmarks. Our results show that the wild and captive groups exhibit morphological dissimilarities in the symmetric component of shape while no significant degree of asymmetry (fluctuating or directional) was detected. Based on our results and on previous literature on the subject, we suggest that (I) captivity is likely to affect the mandibular morphology of M. fuscata; (II) FA may not be a suitable indicator to detect stress in the conditions analysed; and that (III) the mandible may not be the ideal region to study asymmetry because of its functional nature.

Hippopotamidae from the Baynunah Formation

The Baynunah hippopotamid material provides further evidence for the Hippopotamine Event, which marked the spread and increased ecological impact of the Hippopotaminae into wet habitats across Africa and Eurasia at around 8 Ma. The Baynunah Formation hippopotamid belongs to a hippopotamine species distinct from all other contemporary and later species in having a relatively more elongate symphysis, a feature similar to the earlier (and more primitive) Kenyapotamus. A phylogenetic analysis suggests that this hippopotamine is so far the most primitive for which the mandibular morphology is well known. The morphological affinities of the Baynunah species confirm biogeographic links with Africa and indicate no connection between Afro-Arabian and southern Asian hippopotamids at this time, between 8 and 6 Ma.

A New Treatment-Oriented Classification and Treatment Algorithm for Comminuted Mandibular Fractures

This study aimed at proposing a new treatment-oriented classification and treatment algorithm of comminuted mandibular fractures which has a guidance effect on choosing management methods. Patients with comminuted mandibular fractures were retrospectively reviewed in the study and all the patients were classified as follows: Type I: mandibular morphology is sound without bone defect and treated conservatively with intermaxillary fixation (IMF); Type II: mandibular morphology is damaged while the degree of comminution is low and treated by open reduction internal fixation (ORIF) with miniplates; Type III: mandibular morphology is also damaged, but with a higher comminution degree and mass of comminuted. The occlusal relationship can be effectively regained by IMF and was done in the primary debridement. 7-10 days after that, ORIF with titanium meshes was performed in the staged operation; Type IV: comparing to the type III fracture, the occlusal relationship is unable to be regained only by IMF and reconstruction plates were used in ORIF; Type V: the occlusal relationship and mandibular morphology are both damaged with segmental bone defect and mandibular continuity losing and bone flap transplantation was performed for reconstruction; 75 patients were included in the study. Type II fractures are the most common type, followed by type III fractures. 44 of the patients were treated according to the classification and algorithm, and 2 patients of type I and IV manifested infection, 1 patient of type III showed malocclusion in the group of patients who were managed according to our treatment algorithm. Of those who were not in the treatment algorithm, 2 patients of type II and 2 of type III manifested infection, 2 patients of type 3 manifested bone un-union, 2 patients of type II and IV displayed malocclusion and 1 patient of type IV showed mandibular asymmetry. The results of this study suggest the treatment-oriented classification and algorithm for comminuted mandibular fractures has a certain guiding effect on the choice of treatment methods and is able to decrease the complication rate.

Mandibular Structure, Gut Contents Analysis and Feeding Group of Orthopteran Species Collected from Different Habitats of Satoyama Area within Kanazawa City, Japan

A study was conducted on assemblies of various orthopteran species from distinct habitats in the Satoyama region, Kanazawa City, Ishikawa Prefecture, Japan, and a total of 50 distinct orthopteran species were registered. These species were represented by 10 families and were belonged to 17 subfamilies and 27 tribes. Results based on stereo-microscopic examination of the mandibular morphology and the analysis of gut contents suggested seven proposed feeding groups for these collected orthopteran species. Among the examined subfamilies, family Tettigoniidae proved to be the most diverse in mandibular structure and four feeding groups were assigned. This was followed by family Acrididae, which showed three feeding groups. Other families contained only single feeding group. It was noted that only five species, from family Acrididae, were graminivorous with their mandibles characterized by comparatively very short incisors and relatively wide molar regions. The analysis of gut contents of these five species proved to contain more than 80% monocotyledonous plant species. Predation and scavenging as feeding habits were also recorded in some orthopteran species.

Geometric morphometrics of mandibular shape in the dwarf fat-tailed jerboa: relevancy for trinomial taxonomy

We explore the pattern of spatial variation in mandibular morphology in relation to subspecific taxonomy in the dwarf fat-tailed jerboa, Pygeretmus pumilio. The unguided k-means clustering on mandible shape scores, partitioned populations into two clusters, corresponding to western and eastern populations. These clusters nearly perfectly matched the two subspecies groups (pumilio and potanini groups) recognized in an independent study based on the morphology of the glans penis. The mandible, although under environmental pressure, has retained a sufficient amount of taxonomic information to retrieve grouping closely resembling the one derived from a sexually selective trait. We recommend morphometrics of the mandible as a routine step in addressing variations in mammals at species and subspecies levels. We also stress the advantage of unsupervised k-clustering in testing null expectation in subspecies taxonomies. However, the power of this approach has its limitations and in our analysis, the k-clustering failed to retrieve subspecies in the potanini group.