Functional morphology of the tongue muscles of some Indian insect-eating birds

In the complex feeding apparatus of birds, the tongue muscles also play an important role like the jaw muscles. Among the passerine birds, the tongue muscles exhibit greater structural uniformity than the jaw muscles. The elaborate system of extrinsic tongue musculature brings about all necessary movements of the tongue. The intrinsic tongue musculature in all the birds studied is extremely weak and reduced. The principal tongue muscles are better developed in Turdoides and Copsychus than in the other birds. However, in Orthotomus, Anthus, Dicrurus, and Merops, some of the tongue muscles are quite well developed, perhaps compensating for the deficiencies of the other muscles. The origin of M. branchiomandibularis posterior from the outer mandibular ramus in Orthotomus, Dicrurus, and Merops is remarkable, but its occurrence may not be unusual among the passerine birds. Some variations are also observed in the origin and insertion of M. genioglossus in Turdoides, Copsychus, and Anthus. The correlations between the structures and functions of the tongue muscles are not always possible without considering the synergistic actions of the other muscles.     

Avian Jaw Function: Adaptation of the Seven–Muscle System and a Review

Avian jaw function is the most interesting part of the feeding apparatus, and essential in the life of birds. The usual seven jaw muscles in birds are highly adapted for diverse food-getting devices through muscular modifications as well as changes in kinesis of the skeletal components of the skull. In the first part I have described from an introspection of my earlier works, the functional morphology of the seven jaw muscles in different birds in four functional groups such as, adductors of the lower jaw, depressor of the lower jaw, protractors of the upper jaw and retractors-cum-adductors of the upper and lower jaws. Emphasis has been laid on the differential force production by these muscles, depending on the nature of their connective tissue attachments on the skeletal parts and changes in the kinesis of the skeletal parts. The contraction of the muscles and movements of the skeletal parts are rhythmically synchronized in such a way that their concerted action performs adaptively in different feeding adaptations. The differential force production by the one-joint and two-joint muscles in terms of ‘torque’ analysis is important in jaw kinesis. The second part of the text is a historical review of some notable works centred around the avian jaw muscles, jaw kinesis, tongue muscles, synchronization with the movements of the tongue apparatus and adaptational as well as evolutionary significance of the feeding apparatus in different feeding strategies.     

Diversity of feeding adaptations in certain columbid birds: A functional morphological approach

With gradual increasing complexity in higher vertebrate structure and function, the birds as a class have acquired very high degree of feeding adaptations for diverse food-niches. A comparative functional morphological study of the feeding apparatus of 6 species of columbid birds showing diversification in their food-habits reveals that some correlations exist between the form-function complexes of the feeding apparatus and the extent of diversity of food-habits shown by these birds. Among the species of columbid birds selected for the Study,Columba andStreptopelia are ground feeders and predominantly grain-eaters, although quite often they invade diversified food-niches.Treron andDucula, on the other hand, are almost exclusively fruit-eaters, plucking and swallowing fruits from the lofty tree branches, WhileColumba andStreptopelia show better kinesis of their jaws for ground-pecking,Treron. andDucula possess wider gape as well as stronger grasp of their bill for plucking off, grasping and swallowing large-sized fruits. Consequently, the size and pinnateness of the jaw muscles in these fruit-pigeons have developed far greater than those observed inColumba andStreptopelia. Further, inTreron andDucula, the thick and broad ‘venter externus’ slip of the M. pterygoideus ensures complete closure of the bill and possibly prevent any excess lateral expansion of the mandibular rami. Similar correlations have also been observed between the tongue features of columbid birds and the diversity of their feeding adaptation.     

Functional morphology of the jaw muscles of two species of imperial pigeons, Ducula aenea nicobarica and Ducula badia insignis

1. The functional morphological study of the jaw muscles of 2 species of Imperial Pigeons, Ducula aenea nicobarica and Ducula badia insignis has revealed that the structural variations of the bill, osteological and connective tissue elements, and muscles of the jaw apparatus may be correlated to functional diversity in the fruit-eating adaptation of these birds. 2. Both the species of Ducula possess moderately long, thick and stout bill with flexion zones inside, elongated orbital process of the quadrate, stout pterygoid, broad palatine and wide mandibular ramus on either side with increased retroarticular space. Such skeletal modifications together with increased orbital space indicate wide attachment-sites for the muscles, aponeuroses, tendons, and ligaments. 3. The morphology of the quadrato-mandibular joints suggests possible 'coupled kinesis' of the upper jaw, along with depression of the lower jaw. However, in a rhynchokinetic upper jaw as possessed by these birds, the kinesis is just moderate. Hence the gape of the mouth is mainly effected by the depression of the lower jaw, rather less so by the protraction of the upper jaw. 4. Among the functional groups of muscles, M. depressor mandibulae, M. adductor mandibulae externus, M. pseudotemporalis profundus, and M. pterygoideus are especially well developed. The various components of these muscles are provided with stiff as well as wide aponeuroses and tendons (much stronger than those observed in Columba), indicating forceful opening and closure of the beaks for plucking off the fruit, grasping it hard and manipulating it with the help of the beaks before swallowing. 5. The fleshy insertion of the outer slip of M. pseudotemporalis profundus extends ventrally over the dorsolateral surface of the mandible much more than it does in Columba. Further, 2 short and stiff aponeuroses at the rostral insertion of the inner slip of the muscle increase the force of adduction on the mandible. 6. M. adductor mandibulae posterior has not only wider origin and insertion, but also greater mass of fibres than that observed in Columba. 7. M. adductor mandibulae externus and M. pterygoideus form muscle-complexes with the predominance of bipinnate and multipinnate arrangements of fibres and with occasional joining fibres between their components. Such arrangements of fibres indicate sustained force-production, rather than faster movements of the jaw apparatus. 8. M. pterygoideus ventralis lateralis has a well developed 'venter externus' slip which has its thick and fleshy insertion on the outer lateral angular and articular mandible.(ABSTRACT TRUNCATED AT 400 WORDS)     

The role of cranial kinesis in birds.

In birds, the ability to move the upper beak relative to the braincase has been the subject of many functional morphological investigations, but in many instances the adaptive significance of cranial kinesis remains unclear. Alternatively, cranial kinesis may be considered a consequence of the general design of the skull, rather than an adaptive trait as such. The present study reviews some results related to the mechanism and functional significance of cranial kinesis in birds. Quantitative three-dimensional X-ray has shown that in skulls morphologically as divers as paleognaths and neognaths the mechanism for elevation of the upper beak is very similar. One of the mechanisms proposed for avian jaw movement is a mechanical coupling of the upper and the lower jaw movement by the postorbital ligament. Such a mechanical coupling would necessitate upper beak elevation. However, independent control of upper and lower jaw has been shown to occur during beak movements in birds. Moreover, kinematic modeling and force measurements suggests that the maximum extensibility of collagen, in combination with the short distance of the insertion of the postorbital ligament to the quadrato-mandibular articulation do not constitute a block to lower jaw depression. The lower jaw ligaments serve to limit the maximal extension of the mandibula. It is suggested here that cranial kinesis in avian feeding may have evolved as a consequence of an increase in eye size. This increase in size led to a reduction of bony bars in the lateral aspect of the skull enabling the transfer of quadrate movement to the upper jaw. The selective forces favoring the development of a kinetic upper beak in birds may be subtle and act in different ecological contexts. Simultaneous movement of the upper and lower jaw not only increases the velocity of beak movements, but with elevated upper beak also less force is required to open the lower jaw. However, the penalty of increased mobility of elements in a lightweight skull and a large eye is potential instability of skull elements during biting, smaller bite forces and limitations on joint reaction forces. Such a lightly built, kinetic skull may have evolved in animals that feed on small plant material or insects. This type of food does not require the resistance of large external forces on the jaws as in carnivores eating large prey.     

A new psittacosaur from Inner Mongolia and the parrot-like structure and function of the psittacosaur skull

We describe a new species of psittacosaur, Psittacosaurus gobiensis, from the Lower Cretaceous of Inner Mongolia and outline a hypothesis of chewing function in psittacosaurs that in many respects parallels that in psittaciform birds. Cranial features that accommodate increased bite force in psittacosaurs include an akinetic skull (both cranium and lower jaws) and differentiation of adductor muscle attachments comparable to that in psittaciform birds. These and other features, along with the presence of numerous large gastroliths, suggest that psittacosaurs may have had a high-fibre, nucivorous (nut-eating) diet.Psittacosaurs, alone among ornithischians, generate oblique wear facets from tooth-to-tooth occlusion without kinesis in either the upper or lower jaws. This is accomplished with a novel isognathous jaw mechanism that combines aspects of arcilineal (vertical) and propalinal (horizontal) jaw movement. Here termed clinolineal (inclined) jaw movement, the mechanism uses posteriorly divergent tooth rows, rather than kinesis, to gain the added width for oblique occlusion. As the lower tooth rows are drawn posterodorsally into occlusion, the increasing width between the upper tooth rows accommodates oblique shear. With this jaw mechanism, psittacosaurs were able to maintain oblique shearing occlusion in an akinetic skull designed to resist high bite forces.     

Nonlinear dynamical model and response of avian cranial kinesis

All modern birds have kinetic skulls in which the upper bill can move relative to the braincase, but the biomechanics and motion dynamics of cranial kinesis in birds are poorly understood. In this paper, we model the dynamics of avian cranial kinesis, such as prokinesis and proximal rhynchokinesis in which the upper jaw pivots around the nasal-frontal (N-F) hinge. The purpose of this paper is to present to the biological community an approach that demonstrates the application of sophisticated predictive mathematical modeling tools to avian kinesis. The generality of the method, however, is applicable to the advanced study of the biomechanics of other skeletal systems. The paper begins with a review of the relevant biological literature as well as the essential morphology of avian kinesis, especially the mechanical coupling of the upper and lower jaw by the postorbital ligament. A planar model of the described bird jaw morphology is then developed that maintains the closed kinematic topology of the avian jaw mechanism. We then develop the full nonlinear equations of motion with the assumption that the M. protractor pterygoideus and M. depressor mandibulae act on the quadrate as a pure torque, and the nasal frontal hinge is elastic with damping. The mechanism is shown to be a single degree of freedom device due to the holonomic constraints present in the quadrate-jugal bar-upper jaw-braincase-quadrate kinematic chain as well as the quadrate-lower jaw-postorbital ligament-braincase-quadrate kinematic chain. The full equations are verified via simulation and animation using the parameters of a Grey Heron (Ardea cinerea). Next we develop a simplified analytical model of the equations by power series expansion. We demonstrate that this model reproduces the dynamics of the full model to a high degree of fidelity. We proceed to use the harmonic balance technique to develop the frequency response characteristics of the jaw mechanism. It is shown that this avian cranial kinesis model exhibits the characteristics of a hardening Duffing oscillator. Beyond the identification of the characteristics of the underlying dynamics, which provides insight into the behavior of the system, the model and methodology presented here provides other potential benefits. A framework has been developed that could be utilized to study the biomechanics of feeding and bite force as well the effects of cranial kinesis on the frequency and modulation of bird songs.     

Cranial kinesis in lizards (Lacertilia): Origin,biomechanics, and evolution

Various methods of investigation of cranial kinesis are compared. The biomechanical model of the amphikinetic cranial mechanism of lizards developed by Frazzetta (1962) corresponds to the skulls of species with the dependent streptostyly. A new modification of this model is proposed for species with the independent streptostyly, which conforms to the results of experimental investigations of cranial kinesis in living lizards. The lacertilian amphikinesis has developed on the basis of the pleurokinesis inherited from fish ancestors of tetrapods. Movable connections of the maxillo-buccal segments with the axial skull persisted in the amphikinetic skull and were completed by the transversal flexible connections in the dermatocranial roof and loose connections of dermatocranium with the braincase. The development of new movable intracranial connections could have been preceded by transformations in the jaw musculature (formation of the pterygoideus muscle and inclined position of the external jaw adductor), which caused longitudinal jaw movements. Development of new movable connections within the skull was triggered by paedomorphosis processes. In various lacertilian groups, the cranial kinesis was improved by the development of various forms of streptostyly and flexipalatality.     

Morphology and evolution of the ectethmoid-mandibular articulation in the meliphagidae (Aves)

The ectethmoid-mandibular articulation in Melithreptus and Manorina (Meliphagidae: Aves) consists of the dorsal mandibular process fitting into and abutting against the ventral ectethmoid fossa; it forms a brace for the mandible. This articulation in Melithreptus is a typical diarthrosis with long folded capsular walls. The mandible, thus, has two separate articulations, each with a different axis of rotation. No other genus of Meliphagidae (except Ptiloprora) or any other avian family possesses a similar feature. The jaw and tongue musculature of Melithreptus are described. The two muscles opening the jaws are well developed, while those closing the jaws are small. The tongue muscles show no special developments. A large maxillary gland, presumably muscus secreting, covers the ventral surface of the jaw muscles. Its duct opens into the oral cavity just behind the tip of the upper jaw. The frilled tip of the tongue rests against the duct opening. The ectethmoid-mandibular articulation braces the adducted mandible against dorsoposteriorly directed forces. The mandible can be held closed without a compression force exerted by the mandible on the quadrate, permitting the bird to raise its upper jaw with greater ease and less loss of force. The tongue can be protruded through the slight gap between the jaws, moving against the duct opening and thus be coated with mucus. Presumably, these birds capture insects with their sticky tongue. Hence, the ectethmoid-mandibular articulation is an adaptation for this feeding method; it evolved independently in three genera of the Meliphagidae. The ectethmoid-mandibular articulation demonstrates that a bone can have two articulations with different axes of rotation, that the two articular halves can separate widely, and that articular cartilages can be flat and remain in contact over a large area. Its function suggests that the basitemporal articulation of the mandible found in many other birds has a similar function. And it demonstrates that in the evolution of the mammalian dentary-squamosal articulation, the new hinge did not have to lie on the same rotational axis as the existing quadrate-articular hinge.     

Biomechanics of cranial kinesis in birds: Testing linkage models in the white-throated sparrow (Zonotrichia albicollis)

Cranial kinesis in sparrows refers to the rotation of the upper jaw around its kinetic joint with the braincase. Avian jaw mechanics may involve the coupled motions of upper and lower jaws, in which the postorbital ligament transfers forces from the lower jaw, through the quadrate, pterygoid, and jugal bones, to the upper jaw. Alternatively, jaw motions may be uncoupled, with the upper jaw moving independently of the lower jaw. We tested hypotheses of cranial kinesis through the use of quantitative computer models. We present a biomechanical model of avian jaw kinetics that predicts the motions of the jaws under assumptions of both a coupled and an uncoupled mechanism. In addition, the model predicts jaw motions under conditions of force transfer by either the jugal or the pterygoid bones. Thus four alternative models may be tested using the proposed model (coupled jugal, coupled pterygoid, uncoupled jugal, uncoupled pterygoid). All models are based on the mechanics of four-bar linkages and lever systems and use morphometric data on cranial structure as the basis for predicting cranial movements. Predictions of cranial motions are tested by comparison to kinematics of white-throated sparrows (Zonotrichia albicollis) during singing. The predicted relations between jaw motions for the coupled model are significantly different from video observations. We conclude that the upper and lower jaws are not coupled in white-throated sparrows. The range of jaw motions during song is consistent with a model in which independent contractions of upper and lower jaw muscles control beak motion. © 1996 Wiley-Liss, Inc.     

Jaw movement kinematics and jaw muscle (EMG) activity during drinking in the pigeon (Columba livia)

Summary Movements of the maxilla and mandible were recorded during drinking in the head-fixed pigeon and correlated with electromyographic activity in representative jaw muscle groups. During drinking, each jaw exhibits opening and closing movements along both the dorso-ventral and rostro-caudal axes which may be linked with or independent of each other. All subjects showed small but systematic increases in cycle duration over the course of individual drinking bouts. Cyclic jaw movements during drinking were correlated with nearly synchronous activity in the protractor (levator) of the upper jaw and in several jaw closer muscles, as well as with alternating activity in tongue protractor and retractor muscles. No EMG activity was ever recorded in the lower jaw opener muscle, suggesting that lower jaw opening in this preparation is produced, indirectly, by the contraction of other muscles. The results clarify the contribution of the individual jaws to the generation of gape variations during drinking in this species.Abbreviations AMEM adductor mandibulae externus muscle - DM depressor mandibulae muscle - EMG electromyographic - GENIO geniohyoideus muscle - LB lower beak - LED light-emitting diode - PQP protractor quadrati et pterygoidei muscle - PVL pterygoideus ventralis muscle, pars lateralis - SeH/StH serpihyoideus or stylohyoideus muscle - UB upper beak     

Functional morphology of the cranio‐mandibular complex of the Guira cuckoo (Aves)

The cranio‐mandibular complex is an important structure involved in food capture and processing. Its morphology is related to the nature of the food item. Jaw muscles enable the motion of this complex and their study is essential for functional and evolutionary analysis. The present study compares available behavioral and dietary data obtained from the literature with novel results from functional morphological analyses of the cranio‐mandibular complex of the Guira cuckoo (Guira guira) to understand its relationship with the zoophagous trophic habit of this species. The bite force was estimated based on muscle dissections, measurements of the physiological cross‐sectional area, and biomechanical modeling of the skull. The results were compared with the available functional morphological data for other birds. The standardized bite force of G. guira is higher than predicted for exclusively zoophagous birds, but lower than for granivorous and/or omnivorous birds. Guira guira possesses the generalized jaw muscular system of neognathous birds, but some features can be related to its trophic habit. The external adductor muscles act mainly during food item processing and multiple aspects of this muscle group are interpreted to increase bite force, that is, their high values of muscle mass, their mechanical advantage (MA), and their perpendicular orientation when the beak is closed. The m. depressor mandibulae and the m. pterygoideus dorsalis et ventralis are interpreted to prioritize speed of action (low MA values), being most important during prey capture. The supposed ecological significance of these traits is the potential to widen the range of prey size that can be processed and the possibility of rapidly capturing agile prey through changes in the leverage of the muscles involved in opening and closing of the bill. This contributes to the trophic versatility of the species and its ability to thrive in different habitats, including urban areas.     

Comparison of the feeding apparatus in the muttonbird, Puffinus tenuirostris (Temminck) and the fairy prion, Pachyptila turtur (Kuhl) in relation to the capture of the krill, Nyctiphanes australis sars

The short-tailed shearwater (muttonbird) Puffinus tenuirostris (Temminck) and the fairy prion Pachyptila turtur (Kuhl) are procellariiform birds which feed extensively on the euphausiid Nyctiphanes australis Sars in south eastern Tasmania. Data from a hydrodynamic study of the heads of the two birds were used to develop a simple qualitative model of food capture. This model predicts that as the bird moves through the water the open gape, aided by the bill architecture, produces and maintains a low pressure volume into which the prey is sucked. Once inside the bill euphausiids are prevented from escaping by filtering systems which differ in the two birds. In the muttonbird, the filtering mesh consists of retroverted papillae of the upper palate which overlap with opposing papillae on the tongue. In the fairy prion a combination of papillae in the oral cavity and a series of closely-set lamellae on the margins of the upper palate serve to retain the krill.     

An HRP study of the central connections of the facial nerve in the mallard (Anas platyrhynchos L.)

The location of several facialis innervated muscles has been determined by injecting individual muscles with horseradish peroxidase. The depressors of the lower jaw are represented in the dorsal facial motor nucleus and the tongue retractor muscles in the intermediate facial motor nucleus. HRP was also directly applied to the rostral and caudal branch of the facial nerve. The afferent connections are described including two small projections to the principal sensory nucleus and n. interpolaris which were not found in birds before.     

Relations between the ectosomatic and the entosomatic organs

A.N. Severtsov, when introduced the concepts of ecto- and entosomatic organs, illustrated them by three examples of adaptations, namely by the blindness of some subterranean vertebrates, by the "suckers" on the geckos' fingers and toes, and by the flattened body shape of skates and rays. Morphology of the pterygoideus muscle in some song-birds, which is one of the most complicated jaw muscles, is considered here in the framework of those concepts. This muscle displays mosaic variation among bird taxa while the arrangement of skeletal and ligamentous components is rather monotonous. The ventromedial portion of the muscle predominates in the Vietnamese babblers (Garrulax leucolophus, Alcippe peracensis, and Yuhina zantholeuca; fam. Timaliidae), in the leafbird Aegithina lafresnayei (fam. Chloropsidae), and in the drongo Dicrurus aeneus (fam. Dicruridae). One part of this portion, m. retractor palatini, is relatively big in the starling, Gracula religiosa (fam. Sturnidae), and in the dipper, Cinclus cinclus (fam. Trogloditidae). Both muscular bulks (entosomatic organs after Severtsov) affect clearly and directly properties of the bill (ectosomatic organ) without any visible differences in its construction. They provide the upper jaw with additional force (directed downward while grasping a prey) and so fasten it against the passive deviation during tearing or pulling off the food item (the mandible does not accept those forces). These two versions of the muscle morphology are parallel in the functional sense and are independent in respect to their evolutionary origin. The ventromedial portion, judging by its attachment to the mandible close to the center of the quadrato-mandibular joint, is neutral in respect to its adduction, and the m. retractor palatini is not connected to it. Thus, muscular portions under consideration, in spite of their position deep in the feeding apparatus, behave as ectosomatic organs. Deviations in their morphology are not the answer to any antecedent modification of the bill shape or of arrangement of the skeleto-ligamentous apparatus components. Instead, they appear to be primary results due to immediate action of the natural selection to provide a direct functional effects.     

Aspects of masticatory form and function in common tree shrews,Tupaia glis

Tree shrews have relatively primitive tribosphenic molars that are apparently similar to those of basal eutherians; thus, these animals have been used as a model to describe mastication in early mammals. In this study the gross morphology of the bony skull, joints, dentition, and muscles of mastication are related to potential jaw movements and cuspal relationships. Potential for complex mandibular movements is indicated by a mobile mandibular symphysis, shallow mandibular fossa that is large compared to its resident condyle, and relatively loose temporomandibular joint ligaments. Abrasive tooth wear is noticeable, and is most marked at the first molars and buccal aspects of the upper cheek teeth distal to P². Muscle morphology is basically similar to that previously described for Tupaia minor and Ptilocercus lowii. However, in T. glis, an intraorbital part of deep temporalis has the potential for inducing lingual translation of its dentary, and the large medial pterygoid has extended its origin anteriorly to the floor of the orbit, which would enhance protrusion. The importance of the tongue and hyoid muscles during mastication is suggested by broadly expanded anterior bellies of digastrics, which may assist mylohyoids in tensing the floor of the mouth during forceful tongue actions, and by preliminary electromyography, which suggests that masticatory muscles alone cannot fully account for jaw movements in this species.     

The cephalic vascular anatomy of three species of sea snakes

The primary and secondary elements of the cephalic vascular system in some sea snakes are similar to those of the generalized ophidian pattern. The three species examined in this study revealed only minor variations in vascular morphology; these variations appear to be correlated with myological differences among the three species. For example, in Hydrophis melanocephalus it appears that the depressor mandibulae artery is displaced by the cranially expanded insertion of the semi-spinalis and spinalis muscles. A preliminary hypothesis is put forth that explains the apparent constancy of the cephalic vascular system of ophidians in terms of possible constraints due to cranial kinesis.     

Myological variability in a decoupled skeletal system: Batoid cranial anatomy

Chondrichthyans (sharks, batoids, and chimaeras) have simple feeding mechanisms owing to their relatively few cranial skeletal elements. However, the indirect association of the jaws to the cranium (euhyostylic jaw suspension) has resulted in myriad cranial muscle rearrangements of both the hyoid and mandibular elements. We examined the cranial musculature of an abbreviated phylogenetic representation of batoid fishes, including skates, guitarfishes and with a particular focus on stingrays. We identified homologous muscle groups across these taxa and describe changes in gross morphology across developmental and functional muscle groups, with the goal of exploring how decoupling of the jaws from the skull has effected muscular arrangement. In particular, we focus on the cranial anatomy of durophagous and nondurophagous batoids, as the former display marked differences in morphology compared to the latter. Durophagous stingrays are characterized by hypertrophied jaw adductors, reliance on pennate versus fusiform muscle fiber architecture, tendinous rather than aponeurotic muscle insertions, and an overall reduction in mandibular kinesis. Nondurophagous stingrays have muscles that rely on aponeurotic insertions onto the skeletal structure, and display musculoskeletal specialization for jaw protrusion and independent lower jaw kinesis, relative to durophagous stingrays. We find that among extant chondrichthyans, considerable variation exists in the hyoid and mandibular muscles, slightly less so in hypaxial muscles, whereas branchial muscles are overwhelmingly conserved. As chondrichthyans occupy a position sister to all other living gnathostomes, our understanding of the structure and function of early vertebrate feeding systems rests heavily on understanding chondrichthyan cranial anatomy. Our findings highlight the incredible variation in muscular complexity across chondrichthyans in general and batoids in particular. J. Morphol. 275:862–881, 2014. © 2014 Wiley Periodicals, Inc.