Adaptations to tree-gouging in the anterior masticatory apparatus of marmosets (callithrix) [abstract]

Although all genera of Callitrichinae engage in exudativory to some degree, marmosets (Callithrix, Cebuella) take advantage of exudates to the greatest extent. To facilitate exudate feeding, marmosets use their anterior teeth to gouge holes in bark and actively stimulate gum flow. As such, their anterior mandibular teethpossess specialized adaptations such as thickened labial enamel. Marmosets alsoshow masticatory features that facilitate increased gape, but do not appear to generate relatively large bite forces during gouging. However, even without increased bite force the anterior teeth of gougers likely experience different loading patternscompared to non-gouging platyrrhines. Specifically, one might expect that theanterior teeth and symphysis of marmosets are adapted to accommodate relatively high stresses linked to dissipating forces from yield-resistant and tough tree barks. This study uses histological data from thin- sectioned teeth, microCT data of jaws and teeth, and macroscale tests of simulated symphyseal loads to compare the micro- and macro-architecture of the anterior masticatory apparatus in Callithrix and Saguinus (as well as the outgroup Saimiri). Callithrix differs from the other genera in that its canine enamel possesses a much higher degree of decussation, and its anterior tooth roots are larger relative to alveolar bone volume. However, simulated jaw loading suggests a reduced ability to withstand external forces in the marmoset symphysis. The contrast between increased load-resistance ability in the anterior dentition versus relatively reduced symphyseal strength suggests both a potentially complex loading environment during gouging and a mosaic pattern of dentofacial adaptations to this derived biting behavior

Overview of FEED, the Feeding Experiments End-user Database

The Feeding Experiments End-user Database (FEED) is a research tool developed by the Mammalian Feeding Working Group at the National Evolutionary Synthesis Center that permits synthetic, evolutionary analyses of the physiology of mammalian feeding. The tasks of the Working Group are to compile physiologic data sets into a uniform digital format stored at a central source, develop a standardized terminology for describing and organizing the data, and carry out a set of novel analyses using FEED. FEED contains raw physiologic data linked to extensive metadata. It serves as an archive for a large number of existing data sets and a repository for future data sets. The metadata are stored as text and images that describe experimental protocols, research subjects, and anatomical information. The metadata incorporate controlled vocabularies to allow consistent use of the terms used to describe and organize the physiologic data. The planned analyses address long-standing questions concerning the phylogenetic distribution of phenotypes involving muscle anatomy and feeding physiology among mammals, the presence and nature of motor pattern conservation in the mammalian feeding muscles, and the extent to which suckling constrains the evolution of feeding behavior in adult mammals. We expect FEED to be a growing digital archive that will facilitate new research into understanding the evolution of feeding anatomy

Structure of a monomeric photosystem II core complex from a cyanobacterium acclimated to far-red light reveals the functions of chlorophylls d and f

Far-red light (FRL) photoacclimation in cyanobacteria provides a selective growth advantage for some terrestrial cyanobacteria by expanding the range of photosynthetically active radiation to include far-red/near-infrared light (700–800 nm). During this photoacclimation process, photosystem II (PSII), the water:plastoquinone photooxidoreductase involved in oxygenic photosynthesis, is modified. The resulting FRL-PSII is comprised of FRL-specific core subunits and binds chlorophyll (Chl) d and Chl f molecules in place of several of the Chl a molecules found when cells are grown in visible light. These new Chls effectively lower the energy canonically thought to define the “red limit” for light required to drive photochemical catalysis of water oxidation. Changes to the architecture of FRL-PSII were previously unknown, and the positions of Chl d and Chl f molecules had only been proposed from indirect evidence. Here, we describe the 2.25 Å resolution cryo-EM structure of a monomeric FRL-PSII core complex from Synechococcus sp. PCC 7335 cells that were acclimated to FRL. We identify one Chl d molecule in the ChlD1 position of the electron transfer chain and four Chl f molecules in the core antenna. We also make observations that enhance our understanding of PSII biogenesis, especially on the acceptor side of the complex where a bicarbonate molecule is replaced by a glutamate side chain in the absence of the assembly factor Psb28. In conclusion, these results provide a structural basis for the lower energy limit required to drive water oxidation, which is the gateway for most solar energy utilization on earth

A quantitative assessment of the supraorbital region in modern Melanesian crania

Includes bibliographical references (pages [201]-214)The supraorbital region in modem Homo sapiens has been a topic of continued debate concerning its relationship within the larger craniofacial context and regarding a functional and/or structural explanation of supraorbital expression. A morphometric examination of the supraorbital region in a sample of eighty modem Melanesian crania was conducted to examine these two areas of ongoing discussion. A battery of quantitative dimensions, including measurements taken from CT scanning, were taken on the cranial sample and analyzed using both bivariate and multivariate statistical procedures. The results indicated that the supraorbital region in modem Melanesian crania is intricately related to other metric craniofacial dimensions. The supraorbital region is not realistically considered outside of the craniofacial context. The most pervasive influence upon supraorbital development is craniofacial size. Other interrelationships (between specific supraorbital dimensions) and relationships (with other craniofacial variables) exhibit smaller levels of explained variation. The lateral supraorbital heights are differentiated from both medial supraorbital height and supraorbital projections. The lateral heights are linked to upper facial and frontal breadths and contrasted to frontal length and lower facial breadth dimensions. Conversely, supraorbital projections are associated with frontal lengths and contrasted with frontal and upper facial breadths. Medial supraorbital height is hypothesized to be directly related to the development of the frontal sinus. A second focus of this project was the testing of several hypotheses taken from the functional and/or structural models used to account for the supraorbital region. Among the biomechanical models, only the hypothesis derived from the neuro-facial torsion model was supported throughout the supraorbital region. The lateral supraorbital region was linked to temporalis muscle size following the prediction of the bent beam model. However, no other hypotheses derived from this model were supported. Support for the hypotheses derived from the spatial model was found throughout the hypothesis testing. No support for the influence of prognathism upon supraorbital development was offered. A relationship was exhibited between longer crania and larger supraorbitals. The observation that several hypotheses received support in this section highlights the probability that the supraorbital region is influenced by multiple non-mutually exclusive factors.M.A. (Master of Arts

Development and evolution of the unique cetacean dentition

The evolutionary success of mammals is rooted in their high metabolic rate. A high metabolic rate is sustainable thanks to efficient food processing and that in turn is facilitated by precise occlusion of the teeth and the acquisition of rhythmic mastication. These major evolutionary innovations characterize most members of the Class Mammalia. Cetaceans are one of the few groups of mammals in which precise occlusion has been secondarily lost. Most toothed whales have an increased number of simple crowned teeth that are similar along the tooth row. Evolution toward these specializations began immediately after the time cetaceans transitioned from terrestrial-to-marine environments. The fossil record documents the critical aspects of occlusal evolution of cetaceans, and allows us to pinpoint the evolutionary timing of the macroevolutionary events leading to their unusual dental morphology among mammals. The developmental controls of tooth differentiation and tooth number have been studied in a few mammalian clades, but nothing is known about how these controls differ between cetaceans and mammals that retain functional occlusion. Here we show that pigs, a cetacean relative with regionalized tooth morphology and complex tooth crowns, retain the typical mammalian gene expression patterns that control early tooth differentiation, expressing Bmp4 in the rostral (mesial, anterior) domain of the jaw, and Fgf8 caudally (distal, posterior). By contrast, dolphins have lost these regional differences in dental morphology and the Bmp4 domain is extended into the caudal region of the developing jaw. We hypothesize that the functional constraints underlying mammalian occlusion have been released in cetaceans, facilitating changes in the genetic control of early dental development. Such major developmental changes drive morphological evolution and are correlated with major shifts in diet and food processing during cetacean evolution