Jaw Morphology Research Articles

Estimated and invivo measurements of bite force demonstrate exceptionally large bite forces in parrots (Psittaciformes).

Jaw morphology and function determine the range of dietary items that an organism can consume. Bite force is a function of the force exerted by the jaw musculature and applied via the skeleton. Bite force has been studied in a wide range of taxa using various methods, including direct measurement, or calculation from skulls or jaw musculature. Data for parrots (Psittaciformes), considered to have strong bites, are rare. This study calculated bite force for a range of parrot species of differing sizes using a novel method that relied on forces calculated using the area of jaw muscles measured insitu and their masses. The values for bite force were also recorded invivo using force transducers, allowing for a validation of the dissection-based models. The analysis investigated allometric relationships between measures of body size and calculated bite force. Additionally, the study examined whether a measure of a muscle scar could be a useful proxy to estimate bite force in parrots. Bite force was positively allometric relative to body and skull mass, with macaws having the strongest bite recorded to date for a bird. Calculated values for bite force were not statistically different from measured values. Muscle scars from the adductor muscle attachment on the mandible can be used to accurately predict bite force in parrots. These results have implications for how parrots process hard food items and how bite forces are estimated in other taxa using morphological characteristics of the jaw musculature.

Jaw Morphology and Factors Associated with Upper Impacted Canines: Case-Controlled Trial

Introduction and aim: Orthodontic treatment of impacted maxillary canines is challenging and expensive. This study investigated factors associated with impaction risk and the need for surgical exposure. Methods: Seventy-five participants of similar age, skeletal maturity, and gender (32 impacted canines, 43 controls) were included in the case-controlled trial. Three-dimensional study models were created (Trios 3, 3Shape), and panoramic radiographs were taken. The 3D digital models were measured using software to obtain morphological characteristics of the maxilla, such as maxillary surface area (mm2) and volume (mm3). Results: The impacted canine group displayed a significantly higher prevalence of deep bite (OR = 5.01), hypoplastic lateral incisors (OR = 5.47), and rotated adjacent teeth (OR = 3.56) compared to the control group. The impacted canine group exhibited a smaller maxillary surface area and volume. Within the impacted canine group, factors associated with a greater need for surgical exposure included the presence of a persistent deciduous canine (OR = 10.15), a palatal canine position (OR = 7.50), and a steeper canine angulation (p < 0.001). Conclusions: These findings suggest that several signs can serve as potential predictors of increased risk for maxillary canine impaction and the need for surgical intervention. Identifying these factors can aid in early diagnosis and treatment planning for improved patient outcomes.

Kinematics of mandibular advancement devices (MADs): Why do some MADs move the lower jaw backward during mouth opening?

Mandibular advancement devices (MADs) are widely used treatments for obstructive sleep apnea. MADs function by advancing the lower jaw to open the upper airway. To increase patient comfort, most patients allow the mouth to be opened. However, not all systems maintain the lower jaw in a forward position during mouth opening, which results in the production of a retrusion that favors the collapse of the upper airway. Furthermore, the kinematic behavior of the mechanism formed by the mandible-device assembly depends on jaw morphology. This means that, during mouth opening, some devices cause lower jaw protrusion in some patients, but cause its retraction in others. In this study, we report the behavior of well-known devices currently on the market. To do so, we developed a kinematic model of the lower jaw device assembly. This model was validated for all devices analyzed using a high-resolution camera system. Our results show that some of the devices analyzed here did not produce the correct behavior during patient mouth opening.Graphic abstract

Widespread convergence towards functional optimization in the lower jaws of crocodile-line archosaurs.

Extant crocodilian jaws are subject to functional demands induced by feeding and hydrodynamics. However, the morphological and ecological diversity of extinct crocodile-line archosaurs is far greater than that of living crocodilians, featuring repeated convergence towards disparate ecologies including armoured herbivores, terrestrial macropredators and fully marine forms. Crocodile-line archosaurs, therefore, present a fascinating case study for morphological and functional divergence and convergence within a clade across a wide range of ecological scenarios. Here, we build performance landscapes of two-dimensional theoretical jaw shapes to investigate the influence of strength, speed and hydrodynamics in the morphological evolution of crocodile-line archosaur jaws, and test whether ecologically convergent lineages evolved similarly optimal jaw function. Most of the 243 sampled jaw morphologies occupy optimized regions of theoretical morphospace for either rotational efficiency, resistance to Von Mises stress, hydrodynamic efficiency or a trade-off between multiple functions, though some seemingly viable shapes remain unrealized. Jaw speed is optimized only in a narrow region of morphospace whereas many shapes possess optimal jaw strength, which may act as a minimum boundary rather than a strong driver for most taxa. This study highlights the usefulness of theoretical morphology in assessing functional optimality, and for investigating form-function relationships in diverse clades.

Palatal segment contributions to midfacial anterior-posterior growth.

Anterior-posterior (A-P) elongation of the palate is a critical aspect of integrated midfacial morphogenesis. Reciprocal epithelial-mesenchymal interactions drive secondary palate elongation that is coupled to the periodic formation of signaling centers within the rugae growth zone (RGZ). However, the relationship between RGZ driven morphogenetic processes, the differentiative dynamics of underlying palatal bone mesenchymal precursors, and the segmental organization of the upper jaw has remained enigmatic. A detailed ontogenetic study of these relationships is important, because palatal segment growth is a critical aspect of normal midfacial growth, can be modified to produce dysmorphology, and is a likely basis for evolutionary differences in upper jaw morphology. Variation in palatal-segment specific growth may also underlie known differences in palatal segment proportions between inbred mouse strains. We completed a combined whole mount gene expression and morphometric analysis of normal murine palatal growth dynamics and their association with palatal segment elongation and resulting upper jaw morphology. Our results demonstrated that the first formed palatal ruga (ruga 1), found just posterior to the RGZ, maintained an association with important nasal, neurovascular and palatal structures throughout early midfacial development; suggesting that these features are positioned at a proximal source of embryonic midfacial directional growth. Our detailed characterization of midfacial morphogenesis revealed a one-to-one relationship between palatal segments and upper jaw bones during the earliest stages of palatal elongation. Growth of the maxillary anlage within the anterior secondary palate is uniquely coupled to RGZ-driven morphogenesis that more than doubles the length of this palatal segment prior to palatal shelf fusion. Our results also demonstrate that the future maxillary-palatine suture, approximated by the position ruga 1 and consistently associated with the palatine anlage, forms predominantly via the posterior differentiation of the maxilla within the expanding anterior secondary palate. Our complementary ontogenetic comparison of three inbred mouse strains identified small but significant strain-specific differences in early embryonic palatal segment contributions to the upper jaw. Although early palatal segment specific growth is not primarily responsible for adult differences in upper jaw morphology between these strains, our ontogenetic series of measurements provide a useful foundation for understanding the impact of background genetic effects on facial shape and elongation. In combination, our results provide a novel and particularly detailed picture of the earliest spatiotemporal dynamics of intramembranous midfacial skeletal specification and differentiation within the context of the surrounding palatal segment A-P elongation and associated rugae formation.

Morphological Diversity and Evolution of Jaw Morphologies in Zeiform Fishes (Teleostei, Paracanthopterygii).

Zeiformes (dories, tinselfishes, and oreos) are primarily benthopelagic acanthomorph fishes, distributed between 50 and 1000 m depth on continental slopes and on flanks of oceanic islands and seamounts. Among the interesting morphological adaptations of zeiform fishes are their unique and highly protrusible jaws involving premaxillae with long ascending processes and a four-bar linkage, including mobile palatines that pivot on their posterior articulation. This adaptation for increased jaw protrusion has enabled zeiform fishes to capture elusive prey more efficiently and is arguably a major factor in their morphological diversity and evolutionary success. This study examines the evolution of zeiform jaw morphologies using 3D landmark-based multivariate morphometrics as well as phylomorphospace analysis. Results show that the descendants of the zeiform ancestor branched rapidly early in their history, retaining conservative jaw morphologies during this early branching, but subsequently strongly diverged in many of the resulting lineages. Results from this study are compared with earlier research based on overall body form, demonstrating that morphological variation within Zeiformes arose along at least two distinct trajectories: body form and jaw morphology. Variation among genera in body form is not associated with variation among the same genera in jaw morphology, and vice versa. Hypotheses to explain the apparent decoupling of body shape and jaw morphology are addressed along with avenues for further study to better understand the morphological evolution of these iconic fishes.

What is missing from the sturgeon jaw: Developmental morphology of the upper jaw in Acipenser.

Sturgeons belong to the family Acipenseridae, the most species-rich extant family of Acipenseriformes, a basal actinopterygian group of key importance in assessing the early radiations of the actinopterygians. At the same time, acipenseriforms display unique specializations in the morphology of the snout and jaws which make them a valuable model for studying evolutionary novelties. However, despite a long history of research, the homologies of the snout and the mandibular arch of acipenseriforms remain uncertain preventing further studies on the evolutionary origin of their unique snout and jaw structure, and in particular, of the upper jaw symphysis, the key apomorphy of the group and the preoral snout. In the present study, a detailed description of the upper jaw morphology and development in sturgeons is provided in order to address its composition in terms of the common actinopterygian archetype. Based on the obtained results, the upper jaw of acipenseriforms is assumed to have lost the autopalatine portion, which most likely is represented by the separate cartilages supporting the tentacles. Also, the conventional interpretation of the sturgeon's maxilla as dermopalatine is rejected on the grounds of this bone structure and development. Paedomorphosis is proposed to be the most likely mechanism explaining the evolutionary origin of the upper jaw symphysis and supposed modifications of the snout in sturgeons.

Three-dimensional analysis of the morphological changes of the craniofacial jaw and condyle in patients with idiopathic condylar resorption

In this study we aim to describe the three-dimensional analysis of condylar deformation of the temporomandibular joint (TMJ) and morphological changes of the craniofacial jaw in patients with idiopathic condylar resorption (ICR). We also compare those with a control group that is healthy and matched for age and gender. Cone-beam computed tomography (CBCT) and cephalometric radiograph (X-ray) were conducted and analysis of craniofacial measurement, condylar width, length, height, and condylar axial angle changes were done three-dimensionally using ProPlan CMF™ 3.0 software (Materialise). The craniofacial jaw measurements of the ICR patients were significantly different than the control group and the significant changes in the mandible can be seen in ICR patients according to the results of this study. The results of smaller condylar width and height in the ICR group reflect the smaller size of the condyle compared with an unaffected condyle. Also, both right and left sagittal condylar angles (p = 0.001 and p = 0.003), respectively, and axial condylar angles (p = 0.01 and p = 0.02), respectively, displayed significant differences between the two groups. In conclusion, the vertical development of the condyle decreased along with reduced measurements in the width and height of the condyle in ICR patients, and differences in the morphology of the craniofacial jaw and condylar angles were observed between study groups.

Evaluation of tongue pressure and lip closing force in bimaxillary orthognathic surgery: A retrospective study

The purpose of this study was to quantitatively compare changes in tongue pressure and lip closing force among skeletal Class II and Class III patients, who had undergone orthognathic surgery, and a control group.Maximum tongue pressure and lip closing forces were measured preoperatively and at 6 and 12 months postoperatively. Time-course changes were analyzed and compared among the groups.The control group involved 40 skeletal Class I occlusion volunteers (20 male and 20 female), the Class II group involved 20 female patients, and the skeletal Class III group involved 40 patients, who were subdivided by sex into two groups comprising 20 males and 20 females, respectively. Time-course changes in tongue pressure were not significantly different between and within groups. However, postoperative lip closing forces became gradually higher in the Class III group female and male subjects compared with the control group, although this was not observed in the Class II group. There were significant correlations between tongue pressure and lip closing force before and after surgery (p = 0.001), and these correlations increased over time.Although there was no significant increase in maximum tongue pressure after orthognathic surgery, there was an associated increase in perioral muscle strength. This suggests that an increase in perioral muscle strength may contribute more to the stability of postoperative jaw morphology.

Gene losses, parallel evolution and heightened expression confer adaptations to dedicated cleaning behaviour

BackgroundCleaning symbioses are captivating interspecific interactions in which a cleaner fish removes ectoparasites from its client, contributing to the health and diversity of natural fish communities and aquaculture systems. However, the genetic signatures underlying this specialized behaviour remain poorly explored. To shed light on this, we generated a high-quality chromosome-scale genome of the bluestreak cleaner wrasse Labroides dimidiatus, a dedicated cleaner with cleaning as primary feeding mechanism throughout its life.ResultsCompared with facultative and non-cleaner wrasses, L. dimidiatus was found with notable contractions in olfactory receptors implying their limited importance in dedicated cleaning. Instead, given its distinct tactile pre-conflict strategies, L. dimidiatus may rely more heavily on touch sensory perception, with heightened gene expression in the brain in anticipation of cleaning. Additionally, a reduction in NLR family CARD domain-containing protein 3 might enhance innate immunity of L. dimidiatus, probably assisting to reduce the impacts from parasite infections. In addition, convergent substitutions for a taste receptor and bone development genes across cleaners (L. dimidiatus and facultative cleaners) may provide them with evolved food discrimination abilities and jaw morphology that differentiate them from non-cleaners. Moreover, L. dimidiatus may exhibit specialized neural signal transductions for cleaning, as evidenced by positive selection in genes related to the glutamatergic synapse pathway. Interestingly, numerous glutamate receptors also demonstrated significantly higher expression in L. dimidiatus not engaged in cleaning, as compared to those involved in cleaning. Besides, apparent contractions in L. dimidiatus for protocadherins, which are responsible for neuronal development, may further promote specialized neural signal transductions in this species.ConclusionsThis study reveals that L. dimidiatus harbours substantial losses in specific gene families, convergent evolutions across cleaners and a large-scale high gene expression in preparation for cleaning, allowing for adaptation to the dedicated cleaning behaviour.

Oral findings in children with congenital cholestatic disease: A systematic review of case reports and case series

Multiple causes of congenital neonatal cholestasis have been identified, and are classified as extrahepatic or intrahepatic. Biliary atresia (BA), Alagille syndrome (AGS), and progressive familial intrahepatic cholestasis (PFIC) are the most common of these. Many factors associated with cholestatic diseases are known to degrade the oral health of these children. What are the oral manifestations associated with these diseases in the pediatric population? The aim of this article was to evaluate the impact of congenital cholestasis on oral health in pediatric patients.A systematic review of case reports and case series was carried out in PubMed, the Cochrane Library, and the Web of Science to identify relevant articles in French and English published up to April 2022.The review included 19 studies, 16 case reports, and three case series. Only studies dealing with BA and AGS were found. These studies showed an impact on jaw morphology, dental structure, and periodontal health. The facial dysmorphism observed in AGS was specific. Exposure to high levels of bilirubin during the period of dental calcification led to particular coloration. Regarding periodontal status, gingival inflammation was common in these patients, probably resulting from the use of certain treatment-associated drugs and poor oral hygiene. Cohort studies are needed to confirm the classification of these children as being at high individual risk of caries.Many major oral manifestations are found in children with AGS and BA, confirming the need to include a dentist in the care team of patients with congenital cholestatic disease as early as possible. It appears necessary to carry out individual prospective studies of each phenotype in order to confirm and better describe the oral impact of these cholestatic diseases and provide adequate medical care.

Many ways to build an angler: diversity of feeding morphologies in a deep-sea evolutionary radiation.

Almost nothing is known about the diets of bathypelagic fishes, but functional morphology can provide useful tools to infer ecology. Here we quantify variation in jaw and tooth morphologies across anglerfishes (Lophiiformes), a clade spanning shallow and deep-sea habitats. Deep-sea ceratioid anglerfishes are considered dietary generalists due to the necessity of opportunistic feeding in the food-limited bathypelagic zone. We found unexpected diversity in the trophic morphologies of ceratioid anglerfishes. Ceratioid jaws span a functional continuum ranging from species with numerous stout teeth, a relatively slow but forceful bite, and high jaw protrusibility at one end (characteristics shared with benthic anglerfishes) to species with long fang-like teeth, a fast but weak bite and low jaw protrusibility at the other end (including a unique 'wolftrap' phenotype). Our finding of high morphological diversity seems to be at odds with ecological generality, reminiscent of Liem's paradox (morphological specialization allowing organisms to have broader niches). Another possible explanation is that diverse ceratioid functional morphologies may yield similar trophic success (many-to-one mapping of morphology to diet), allowing diversity to arise through neutral evolutionary processes. Our results highlight that there are many ways to be a successful predator in the deep sea.

Unique dentition of rhynchosaurs and their two‐phase success as herbivores in the Triassic

AbstractRhynchosaurs were key herbivores over much of the world in the Middle and Late Triassic, often dominating their faunas ecologically, and much of their success may relate to their dentition. They show the unique ankylothecodont mode of tooth implantation, with deep roots embedded in the bone of the jaw and low crowns that were rapidly worn down in use. During growth, the main area of oral food processing, located in the middle and posterior portions of the occlusal surfaces of the jaws, moved posteriorly relative to the anterior tips of the jaws, which curved up. As the maxilla and dentary grew by addition of new bone posteriorly, the dental lamina fed in new teeth at the back of the tooth rows. CT scanning of the holotype skull of Bentonyx sidensis from the Middle Triassic of England reveals previously concealed details of the dentition. Together with new dentary material from the same location, this has enabled us to examine the tooth replacement process and elucidate ontogenetic changes in dentition and jaw morphology as the animals aged. There were major changes in rhynchosaur anatomy and function through their evolutionary history, with the early forms of the Middle Triassic dying out before or during the Carnian Pluvial Episode (233–232 Ma), and the subclade Hyperodapedontinae, with broad skulls and adaptations to chop tough vegetation, subsequently diversifying worldwide in a successful ecological expansion until their global extinction 227–225 Ma.

Mechanical properties of the California sea lion (Zalophus californianus) and northern elephant seal (Mirounga angustirostris) lower jaws explain trophic plasticity.

The fossil record of pinnipeds documents a suite of morphological changes that facilitate their ecological transition from a terrestrial to an aquatic lifestyle. Among these is the loss of the tribosphenic molar and the behavior typically associated with it in mammals: mastication. Instead, modern pinnipeds exhibit a broad range of feeding strategies that facilitate their distinct aquatic ecologies. Here, we examine the feeding morphology of two species of pinnipeds with disparate feeding ecologies: Zalophus californianus, a specialized raptorial biter, and Mirounga angustirostris, a suction specialist. Specifically, we test whether the morphology of the lower jaws facilitates trophic plasticity in feeding for either of these species. We used finite element analysis (FEA) to simulate the stresses during the opening and closing of the lower jaws in these species to explore the mechanical limits of their feeding ecology. Our simulations demonstrate that both jaws are highly resistant to the tensile stresses experienced during feeding. The lower jaws of Z. californianus experienced the maximum stress at the articular condyle and the base of the coronoid process. The lower jaws of M. angustirostris experienced the maximum stress at the angular process and were more evenly distributed throughout the body of the mandible. Surprisingly, the lower jaws of M. angustirostris were even more resistant to the stresses experienced during feeding than those of Z. californianus. Thus, we conclude that the superlative trophic plasticity of Z. californianus is driven by other factors unrelated to the mandible's tensile resistance to stress during feeding.

Correlation between facial asymmetry of skeletal class III jaw relationship and morphology of the temporomandibular joint: A cone beam computed tomography study

Background/purposeFacial asymmetry is a common dentofacial deformity especially in skeletal Class III jaw relation. The purpose of this study was to evaluate the condylefossa relationship of Taiwanese people in skeletal Class III jaw relation with or without facial asymmetry by CBCT image. Materials and methodsCBCT images were collected from Kaohsiung Medical University Hospital and then divided into symmetric Class III group (Menton [Mn] deviation ≦ 4 mm) and asymmetric Class III group (Menton [Mn] deviation > 4 mm). Maxilla deviation, upper and lower dental midline deviation, joint space, condylar axial angle and condylar volume was measured. Independent t test was used for comparison between groups, and paired t test was applied for comparison between both condyles within each group. The Pearson correlation coefficient was used to analyze the correlation between skeletal midline deviations and joint morphology. ResultsNo significant difference was found in joint space between groups or between sides within each group, but we can find a significant difference in axial condylar angle easurement which was greater on the non-deviation side of condyle. Significant lesser condylar volume was also found on the deviation side in asymmetric group. There had a significant positive correlation between Mn point deviation, geometric center difference and condylar volume ratio. ConclusionThese results demonstrated that in the side with greater mandibular growth potential, the axis rotation in axial plane would be greater. In the side with lesser mandibular growth potential, the total condyle volume would be lesser, even though with large variation.

Fitting fangs in a finite face: A novel fang accommodation strategy in a 280-million-year-old ray-finned fish.

Though Paleozoic ray-finned fishes are considered to be morphologically conservative, we report a novel mode of fang accommodation (i.e., the fitting of fangs inside the jaw) in the Permian actinopterygian †Brazilichthys macrognathus, whereby the teeth of the lower jaw insert into fenestrae of the upper jaw. To better understand how fishes have accommodated lower jaw fangs through geologic time, we synthesize the multitude of ways living and extinct osteichthyans have housed large mandibular dentition. While the precise structure of fang accommodation seen in †Brazilichthys has not been reported in any other osteichthyans, alternate strategies of upper jaw fenestration to fit mandibular fangs are present in some extant ray-finned fishes-the needlejaws Acestrorhynchus and the gars of the genus Lepisosteus. Notably, out of our survey, only the two aforementioned neopterygians bear upper jaw fenestration for the accommodation of mandibular fangs. We implicate the kinetic jaws of neopterygians in this trend, whereby large mandibular fangs are more easily fit between the multitude of upper jaw and palatal bones. The restricted space available in early osteichthyan jaws may have led to a proliferation of novel ways to accommodate large dentition. We recommend a greater survey of Paleozoic actinopterygian jaw morphology, in light of these results and other recent reevaluations of jaw structure in early fossil ray-fins.

A comparative analysis of the ontogeny of syngnathids (pipefishes and seahorses) reveals how heterochrony contributed to their diversification.

Syngnathids are a highly derived and diverse fish clade comprising the pipefishes, pipe-horses, and seahorses. They are characterized by a plethora of iconic traits that increasingly capture the attention of biologists, including geneticists, ecologists, and developmental biologists. The current understanding of the origins of their derived body plan is, however, hampered by incomplete and limited descriptions of the early syngnathid ontogeny. We provide a comprehensive description of the development of Nerophis ophidion, Syngnathus typhle, and Hippocampus erectus from early cleavage stages to release from the male brooding organ and beyond, including juvenile development. We comparatively describe skeletogenesis with a particular focus on dermal bony plates, the snout-like jaw morphology, and appendages. This most comprehensive and detailed account of syngnathid development to date suggests that convergent phenotypes (e.g., reduction and loss of the caudal fins), likely arose by distinct ontogenetic means in pipefishes and seahorses. Comparison of the ontogenetic trajectories of S. typhle and H. erectus provides indications that characteristic features of the seahorse body plan result from developmental truncation. Altogether, this work provides a valuable resource and framework for future research to understand the evolution of the outlandish syngnathid morphology from a developmental perspective.

A new morphotype of nothosaurs (Sauropterygia: Nothosauridae) from the Middle Triassic of South China

ABSTRACT A new morphotype of nothosaurs collected from the Upper Member of Anisian Guanling Formation in the Muta village, Luxi County, Yunnan Province, China is reported here. The new morphotype is represented by a single specimen that can be distinguished from other nothosaurs in the combination of the following features: premaxilla partly fused, jugal positioned forward in the cheek, pineal foramen in a deep trough and close to the middle of the skull table, quadratojugal present, distinctly long internal naris. The right lower jaw of the new specimen is completely exposed in medial view, providing hereto unknown information about the medial morphology of the lower jaw for nothosaurid sauropterygians, including the large splenial forming half of the inner wall of the lower jaw, the slender and elongate coronoid located in the middle of the mandible, and the Meckelian foramen located within the adductor fossa bounded by surangular and prearticular. Morphological comparison with other Triassic eosauropteygians reveals previously unrecognised characters that may be used for reconstructing the phylogeny of sauropterygians in the future.

The first record of the family Parvaplustridae (Gastropoda, Heterobranchia) from hydrothermal vent fields of the Piip Volcano, Bering Sea with the description of a new species of the genus Parvaplustrum

A new species, Parvaplustrum wareni sp. nov. (Parvaplustridae), collected in the area of the submarine Piip Volcano, the northwestern Bering Sea, at depths of 400–472 m, has been described on materials obtained during the research cruises #75 and #82 aboard the R/V Akademik M.A. Lavrentiev. This is the first record of the family in the Bering Sea. Parvaplustrum wareni sp. nov. is found around hydrothermal vents, where it forms aggregations with population densities of up to 6000–31 000 ind./m2. Parvaplustrum wareni sp. nov. differs from the other species of the genus by its globose shell, jaw morphology, and by the absence of spiral sculpture on the body whorl. In addition to the morphology, molecular data on mitochondrial (cytochrome c oxidase subunit I and 16S rRNA) and nuclear (histone H3 and 28S rRNA) markers were used. We assume that P. wareni sp. nov. feeds on bacterial mats, scooping them up with its petaliform radular teeth. The presence of bacteria-like filaments on gill lamellae suggests the possibility of an epibiotic association which needs further study. In addition to the Bering Sea, the range of this new species covers also the Hydrate Ridge, off Oregon (northeastern Pacific), where specimens were previously identified as P. cadieni.

Fish as Model Systems to Study Epigenetic Drivers in Human Self-Domestication and Neurodevelopmental Cognitive Disorders

Modern humans exhibit phenotypic traits and molecular events shared with other domesticates that are thought to be by-products of selection for reduced aggression. This is the human self-domestication hypothesis. As one of the first types of responses to a novel environment, epigenetic changes may have also facilitated early self-domestication in humans. Here, we argue that fish species, which have been recently domesticated, can provide model systems to study epigenetic drivers in human self-domestication. To test this, we used in silico approaches to compare genes with epigenetic changes in early domesticates of European sea bass with genes exhibiting methylation changes in anatomically modern humans (comparison 1), and neurodevelopmental cognitive disorders considered to exhibit abnormal self-domestication traits, i.e., schizophrenia, Williams syndrome, and autism spectrum disorders (comparison 2). Overlapping genes in comparison 1 were involved in processes like limb morphogenesis and phenotypes like abnormal jaw morphology and hypopigmentation. Overlapping genes in comparison 2 affected paralogue genes involved in processes such as neural crest differentiation and ectoderm differentiation. These findings pave the way for future studies using fish species as models to investigate epigenetic changes as drivers of human self-domestication and as triggers of cognitive disorders.