Comparative morphology,morphometry and distribution pattern of the trigeminal nerve branches supplying the bill tip in the ostrich (Struthio camelus) and emu (Dromaius novaehollandiae)

The subdivisions of the trigeminal nerve (N. ophthalmicus R. medialis and N. intramandibularis) innervating the upper and lower bill tip, respectively, were well developed in both the ostrich and emu and displayed extensive branching. Transmission electron microscopy revealed that both nerves displayed features typical of a mixed, peripheral nerve. Nerve fibre size in the ostrich and emu was larger than that reported in domestic poultry. There were a significantly higher number of myelinated nerve fibres in the N. ophthalmicus R. medialis in the emu by comparison with the same nerve in the ostrich, or by comparison with the N. intramandibularis of either species. As myelinated nerve fibres supply Herbst corpuscles, and these structures have been demonstrated in this region in these two species, this may indicate that the upper bill of the emu is more sensitive to vibrational stimuli than the upper bill of the ostrich or the lower bill of both species. The large size of the nerve fibres, the high nerve fibre count and the particular distribution of the nerves in the bill tip support the existence of a well‐developed sensory area in this region of the ostrich and emu.     

Expression of DPP6 in Meckel's cartilage and tooth germs during mouse facial development

Dipeptidyl peptidase-like protein 6 (DPP6), a member of the dipeptidyl aminopeptidase family, plays distinct roles in brain development, but its expression in embryonic Meckel's cartilage and tooth germs development is unknown. We analyzed the expression pattern of DPP6 in Meckel's cartilage and tooth germs development using in situ hybridization. DPP6 was detected in different patterns in Meckel's cartilage and tooth germs during mouse facial development from 11.5 to 13.5 days post-coitus (dpc) embryos. The expression pattern of DPP6 suggests that it may be involved in mandible and tooth development.     

Gross morphology and topographical relationships of the hyobranchial apparatus and laryngeal cartilages in the ostrich (Struthio camelus)

The ostrich hyobranchial apparatus consists of the centrally positioned paraglossalia and basiurohyale and paired caudo‐lateral elements (horns), each consisting of the ceratobranchiale and epibranchiale. The paraglossalia lie within the tongue parenchyma and consist of paired, flat, caudo‐laterally directed cartilages joined rostrally. The basiurohyale forms a single dorso‐ventrally flattened unit composed of an octagonal‐shaped body from which extend rostral (the rostral process) and caudal (the urohyale) projections. The laryngeal skeleton consists of cricoid, procricoid and paired arytenoid cartilages. The large ring‐shaped cricoid cartilage displays a body and paired wings which articulate with each other and with the procricoid. The blunt, ossified, rostral projection of the cricoid and the scalloped nature of the arytenoid cartilages are unique to the ostrich. The procricoid is a single structure which links the paired arytenoids and wings of the cricoid. The hyobranchial apparatus is firmly attached to the tongue parenchyma and to the larynx and proximal trachea. In contrast to previous reports in this species, the horns of the hyobranchial apparatus are not related to the skull. Ossification of the body of the basihyale, the ceratobranchials and the rostral process and body of the cricoid cartilage of the larynx lends stability to these structures.     

Cranial skeletogenesis and osteology of the redeye tetra Moenkhausia sanctaefilomenae

The skeletogenesis and osteology of the syncranium of the redeye tetra Moenkhausia sanctaefilomenae is described. Skeletal development is rapid, with many elements of the chondrocranium and splanchnocranium well formed prior to the onset of ossification. The chondrocranium develops from an initial set of cartilaginous precursors, and continued elaboration proceeds from a series of processes which expand and converge to form the floor of the cranial vault, the otic capsule, the supraorbital bridge and the ethmoid region. Prodigious growth is observed for a number of splanchnocranial elements, including the Meckel's cartilage and the ceratohyal cartilage. Ossification occurs in overlapping phases with initial ossification of the jaws and neurocranial floor followed by the splanchnocranium, the supraorbital bridges and the ethmoid and cranial vault. Teeth are observed primarily on the premaxilla and dentary, while a single tooth is present on the maxilla. Particular cartilages, which had originally formed in the early larva, appear to degenerate and have no ossified representative in the adult syncranium. The cranial development for M. sanctaefilomenae is compared to those of other characiforms.     

Tissue regeneration during lower jaw restoration in zebrafish shows some features of epimorphic regeneration

Zebrafish have the ability to regenerate skeletal structures, including the fin, skull roof, and jaw. Although fin regeneration proceeds by epimorphic regeneration, it remains unclear whether this process is involved in other skeletal regeneration in zebrafish. Initially in epimorphic regeneration, the wound epidermis covers the wound surface. Subsequently, the blastema, an undifferentiated mesenchymal mass, forms beneath the epidermis. In the present study, we re-examined the regeneration of the zebrafish lower jaw in detail, and investigated whether epimorphic regeneration is involved in this process. We performed amputation of the lower jaw at two different positions; the proximal level (presence of Meckel's cartilage) and the distal level (absence of Meckel's cartilage). In both manipulations, a blastema-like cellular mass was initially formed. Subsequently, cartilaginous aggregates were formed in this mass. In the proximal amputation, the cartilaginous aggregates were then fused with Meckel's cartilage and remained as a skeletal component of the regenerated jaw, whereas in the distal amputation, the cartilaginous aggregates disappeared as regeneration progressed. Two molecules that were observed during epimorphic regeneration, Laminin and msxb, were expressed in the regenerating lower jaw, although the domain of msxb expression was out of the main plain of the aggregate formation. Administration of an inhibitor of Wnt/β-catenin signaling, a pathway associated with epimorphic regeneration, showed few effects on lower jaw regeneration. Our finding suggests that skeletal regeneration of the lower jaw mainly progresses through tissue regeneration that is dependent on the position in the jaw, and epimorphic regeneration plays an adjunctive role in this regeneration.     

Social dynamics modify behavioural development in captive white-cheeked (<Emphasis Type="Italic">Nomascus leucogenys</Emphasis>) and silvery (<Emphasis Type="Italic">Hylobates moloch</Emphasis>) gibbons

Behavioural development was quantified in one family group of silvery gibbons (Hylobates moloch) and one of white-cheeked gibbons (Nomascus leucogenys) over 11 months during 2005 and 2008 at the Perth Zoo. Levels of locomotion, solo play and play solicitation peaked by 5 years of age but continued solo and social play in older immatures suggested that social development continued until at least 7 years of age. Mature offspring responded to play solicitations from younger siblings. The transition to sub-adulthood was marked by the presence of spatial peripheralisation from the parents, and coincided with aggression from the father to a sub-adult male. After the birth of a new infant, the male sub-adult stayed closer to his mother (and the infant) but not to his father; his juvenile brother was closer to both parents. Within-family observations of behaviour that is difficult to observe in the wild but can be observed in captivity contributes to our understanding of family dynamics in gibbons. Observations of these captive groups suggest that sub-adult peripheralisation may be influenced by family social dynamics as well as by local ecology, and that older offspring are responsive to the development of younger siblings.     

Embryogenesis and early larval development in wild-caught Levantine scraper,Capoeta damascina (Valenciennes, 1842)

Levantine scraper, Capoeta damascina is a candidate species for future stock assessments, conservation studies, and hatchery efforts. Herein, we documented embryonic and early larval development, from egg activation to the exogenous feeding period, using morphological and histological landmarks. Embryos were obtained by in vitro fertilization from hormonally induced wild-caught broodstock, and subsequent development was monitored at temperatures coinciding with native conditions. Embryonic development from fertilization to hatch lasted ~105–110 hr. Larvae emerged with unpigmented eyes and body morphology, as well as an undifferentiated digestive tract. The mouth was closed at hatch by the oropharyngeal membrane and opened by the early endogenous feeding period. Trabeculae cartilage, quadrate bone, and Meckel's cartilage of the endoskeleton were present during the endogenous feeding period. During this period, the larvae underwent considerable changes in craniofacial morphology, locomotion, and organogenesis of the digestive tract. The cartilaginous floor of the neurocranium developed and the first four ceratobranchials appeared simultaneously at the end of endogenous feeding period. The digestive tract was differentiated into buccopharynx, esophagus, and small intestine during the endogenous feeding period. The intestinal valve and numerous longitudinal folds at the posterior region of the intestine formed together by the endo–exogenous feeding period. Major developmental events in retinogenesis occurred during the endogenous feeding period. When larvae entered exogenous feeding the mouth was fully-functional. Additionally, liver size and eye diameter increased. Our analysis of embryonic and early larval development in Levantine scraper aligned with other freshwater fishes.     

Partial amino acid sequence of osteocalcin from an extinct species of ratite bird

Osteocalcin the major gamma carboxyglutamic acid containing protein of vertebrate bone has been purified from the bones of a specimen of Pachyornis elephantopus, a species of the extinct class of New Zealand ratite birds, the moas. The sequence of the N-terminal region of moa osteocalcin was determined using gas phase N-terminal sequencing. The N-terminal sequences of the ostrich and rhea osteocalcins were also determined. Alignment of the N-terminal sequence of osteocalcin from the extinct moa against the osteocalcins of the extant ostrich, rhea and emu reveals the homology amongst the ratite species is greater than the homology with the chicken osteocalcin.     

Chromosome studies in four species of Ratitae (Aves)

Chromosomes were studied in female specimens of the ostrich, Struthio camelus L., cassowary, Casuarius casuarius (L.), emu, Dromiceius novaehollandiae (Lath.) and rhea, Rhea americana L. by means of blood and feather pulp culture techniques. Male karyotypes were also studied in the emu and rhea. The diploid chromosome number was most likely 80 in the ostrich and rhea and 82 in the emu, while the exact number could not be determined in the cassowary. Karyotypes of the 4 species were strikingly similar and apparently interchangeable with one another with slight modifications of the centromeric position in one or two pairs of macrochromosomes. No heteromorphic macrochromosomal pair was found either in female specimens or in male ones of the ratite species so far examined, except for a female rhea. This specimen was found to possess an acrocentric chromosome which was evidently a member of nos. 4–6, but considerably smaller than any other chromosome of the group. ³H-thymidine autoradiography provided no more information than the straightforward morphological analysis with regard to the differentiation of the sex-chromosomes.Contributions from the Chromosome Research Unit, Hokkaido University. Dedicated to Emeritus Professor Sajiro Makino on the occasion of his retirement, in honor of his 40 years' service with the University. Supported by a grant from the Scientific Research Fund of the Ministry of Education (No. 584099).     

Histochemical Characterization and Distribution of Fiber Types in the Pectoralis Muscle of the Ostrich (Struthio camelus) and Emu (Dromaius novaehollandiae)

The muscle fibers of the pectoralis (M. pectoralis pars thoracicus) of a male and a female ostrich (Struthio camelus) and a male and a female emu (Dromaius novaehollandiae) were studied histochemically for succinate dehydrogenase and myofibrillar adenosine triphosphatase. Slow-tonic (ST), fast-twitch oxidative-glycolytic (FOG) and fast-twitch glycolytic (FG) fibers were approximately equal in number and distribution in the emu pectoralis examined. In the ostriches, both predominantly FG and approximately equal areas, were present. ST fibers were significantly (P ≤ 0.05) larger than the similarly (P ≥ 0.05) sized FG and FOG fibers in the female ostrich and emus. In the male ostrich ST fibers were smaller (P ≤ 0.05) than FG fibers, neither of which were significantly (P ≥ 0.05) different from FOG fibers. The ratites have the greatest percentage and widest distribution of ST fibers found in any avian pectoralis studied to date. This could represent the ancestoral avian pectoralis, neoteny or an effect of flightlessness. ST fibers are used in the maintenance of posture, which is probably the main role of the pectoralis in the emu. The predominantly FG areas of the ostrich are indicative of an additional function, namely, behavioural display. Sexual dimorphism in the ostrich pectoralis is strongly suggested.     

An infrared, thermographic study of surface temperature in three ratites: ostrich, emu and double-wattled cassowary

(1)Surface temperatures of the ostrich (Struthio camelus), emu (Dromaius novaehollandiae) and double-wattled cassowary (Casuarius casuarius) were meas ured using infrared thermography at ambient temperatures ranging from 0 to 27°C. (2) The pattern of surface temperature regulation for thermoregulatory purposes was similar in all species examined. Beak, lower leg and neck surface temperatures are regulated in all species to alter heat exchange with the environment. The feet and toes are also used by the ostrich and emu to regulate heat exchange. The cassowary does not use the feet and toes to the same extent but used the casque in a similar manner. (3) Standard metabolic rates were estimated using a geometric model of a bird and instantaneous heat loss calculated for specific body parts. (4) Up to 40% of metabolic heat production can be dissipated across these structures which comprise 12% and 17.5% of total body surface area. (5) The ostrich was able to regulate surface temperature more precisely than the other species, probably due to a larger body size. The large wings of the ostrich are useful for thermoregulation by increasing convective heat loss.     

The Tarsometatarsus of the Ostrich Struthio camelus: Anatomy,Bone Densities,and Structural Mechanics

Background

The ostrich Struthio camelus reaches the highest speeds of any extant biped, and has been an extraordinary subject for studies of soft-tissue anatomy and dynamics of locomotion. An elongate tarsometatarsus in adult ostriches contributes to their speed. The internal osteology of the tarsometatarsus, and its mechanical response to forces of running, are potentially revealing about ostrich foot function.

Methods/Principal Findings

Computed tomography (CT) reveals anatomy and bone densities in tarsometatarsi of an adult and a young juvenile ostrich. A finite element (FE) model for the adult was constructed with properties of compact and cancellous bone where these respective tissues predominate in the original specimen. The model was subjected to a quasi-static analysis under the midstance ground reaction and muscular forces of a fast run. Anatomy–Metatarsals are divided proximally and distally and unify around a single internal cavity in most adult tarsometatarsus shafts, but the juvenile retains an internal three-part division of metatarsals throughout the element. The juvenile has a sparsely ossified hypotarsus for insertion of the m. fibularis longus, as part of a proximally separate third metatarsal. Bone is denser in all regions of the adult tarsometatarsus, with cancellous bone concentrated at proximal and distal articulations, and highly dense compact bone throughout the shaft. Biomechanics–FE simulations show stress and strain are much greater at midshaft than at force applications, suggesting that shaft bending is the most important stressor of the tarsometatarsus. Contraction of digital flexors, inducing a posterior force at the TMT distal condyles, likely reduces buildup of tensile stresses in the bone by inducing compression at these locations, and counteracts bending loads. Safety factors are high for von Mises stress, consistent with faster running speeds known for ostriches.

Conclusions/Significance

High safety factors suggest that bone densities and anatomy of the ostrich tarsometatarsus confer strength for selectively critical activities, such as fleeing and kicking predators. Anatomical results and FE modeling of the ostrich tarsometatarsus are a useful baseline for testing the structure’s capabilities and constraints for locomotion, through ontogeny and the full step cycle. With this foundation, future analyses can incorporate behaviorally realistic strain rates and distal joint forces, experimental validation, and proximal elements of the ostrich hind limb.     

The Complete Mitochondrial Genome of Rhea americana and Early Avian Divergences

The complete mitochondrial DNA, mtDNA, molecule of the greater rhea, Rhea americana, was sequenced. The size of the molecule is 16,710 nucleotides. The organization of the molecule conforms with that described for the chicken and the ostrich. It has been shown previously that relative to other vertebrates the NADH3 gene of the ostrich has an insertion of one nucleotide in position 174 of the gene. The same observation was made in the rhea and in the newly sequenced NADH3 gene of the emu, Dromaius novaehollandiae. Comparison with the NADH3 gene of the chicken and the rook suggests that the inserted nucleotide may be deleted by RNA editing. The divergence between the two struthioniform species, the ostrich and the rhea, was molecularly dated at ≈51 million years before present, MYBP. This dating is more recent than commonly acknowledged. Phylogenetic analysis of the complete cytochrome b genes of seven avian orders placed the Passeriformes basal in the avian tree with the Struthioniformes among the remaining Neognathae. These findings challenge the commonly accepted notion that the most basal avian divergence is that between the Palaeognathae and Neognathae. Received: 13 October 1997 / Accepted: 17 January 1998     

Kinematic analysis of jaw protrusion in orectolobiform sharks: A new mechanism for jaw protrusion in elasmobranchs

Jaw protrusion is an important component of prey capture in fishes, although the mechanics of protrusion have thus far been studied largely in teleosts. Elasmobranchs are also able to protrude their jaws (Tricas and McCosker [1984] Proc. Cal. Acad. Sci. 43: 221–238; Tricas [1985] Mem. S. Calif. Acad. Sci. 8:81–91.; Frazzetta and Prange [1987] Copeia 4:979–993). Several related features of the feeding apparatus contribute to jaw protrusion in sharks. Labial cartilages form an extendible series attached dorsally to the anterolateral face of the palatoquadrate and ventrally to the anteroventral surface of Meckel's cartilage. The labial cartilage chain swings anterolaterally as the lower jaw is depressed, thrusting the labial margins forward to form a circular oral opening and displacing the jaw apparatus towards the food; this pattern is analogous to halecomorph and primitive actinopterygian fishes in which the maxilla swings forward (Lauder [1979] J. Zool. Lond. 187:543–578). The palatoquadrate and Meckel's cartilage also project anteriorly and represent the major contribution to protrusion. These movements occur simultaneously with enlargement of the oral cavity to generate suction. The wobbegong sharks (Orectolobidae) are specialized for jaw protrusion. The spotted wobbegong protrudes its jaw by 33% of its chondrocranial length using two different mechanical systems. In the first mechanism of jaw protrusion, the intermandibularis and interhyoideus muscles medially compress the lower jaw and hyomandibulae. Compression of the lower jaw results in a more acute symphyseal angle so that the anteroposterior alignment of the lower jaw increases due to the rotation of each lower jaw towards a saggital orientation. Distal compression of the hyomandibulae at their attachments to the jaws swings the jaws forward. The second mechanism involves rotation of the ceratohyal around a posterior process of the lower jaw, pushing the hyomandibulae anteroventrally, thereby pushing the jaw articulation ventrally and anteriorly to protrude the jaws. © 1994 Wiley-Liss, Inc.     

Description of the adult skeleton and developmental osteology of the hyperossified horned frog,Ceratophrys cornuta (Anura: Leptodactylidae)

The adult skeleton and tadpole chondrocranium of the leptodcatylid frog, Ceratophrys cornuta (Ceratophryinae), are described in detail, including the ontogenetic development of the chondrocanium and the ossification sequence of the skeleton. The chondrocranium of the carnivorous larvae is unique in lacking a frontoparietal fontanelle and possessing a complete dorsal roof of cartilage. Furthermore, the chondrocranium is extremely robust, particularly those elements involved in the feeding mechanism; these include large palatoquadrate cartilages, stout Meckel's, supra- and infrarostral cartilages, and short, wide, cornua trabeculae. The chondrocranium of C. cornuta resembles that described for Ceratophrys cranwelli, but differs from the chondrocrania reported for the species of Lepidobatrachus. The large adult skull is hyperossified; most elements are fused into a single unit, and nearly all dermal elements are ornamented, casqued, and co-ossified. Calcification is present in nearly every cartilaginous element of the skeleton in larger (older) adults. Several osteological characters previously used in ceratophryine systematics, such as the otic ramus of the squamosal and the columella, are reassessed. Contrary to previous reports, the ossified, dorsal dermal shield above the vertebral column in many ceratophryine anurans is absent in C. cornuta. With few exceptions, the ossification sequence relative to metamorphosis is consistent with those that are known for other anurans. The squamosal arises from three distinct centers of ossification, including an otic element. The frontoparietal arises from two centers of ossification that fuse early in development. A robust postorbital arch is formed primarily by the otic flange of the frontoparietal, which articulates laterally with the medial border of the otic ramus of the squamosal. Changes in the timing of development, or heterochrony, are involved with the evolution of the unusual skull and skeleton of ceratophryine frogs. J Morphol 232:169–206, 1997. © 1997 Wiley-Liss, Inc.     

Mammalian development does not recapitulate suspected key transformations in the evolutionary detachment of the mammalian middle ear

The ectotympanic, malleus and incus of the developing mammalian middle ear (ME) are initially attached to the dentary via Meckel''s cartilage, betraying their origins from the primary jaw joint of land vertebrates. This recapitulation has prompted mostly unquantified suggestions that several suspected—but similarly unquantified—key evolutionary transformations leading to the mammalian ME are recapitulated in development, through negative allometry and posterior/medial displacement of ME bones relative to the jaw joint. Here we show, using µCT reconstructions, that neither allometric nor topological change is quantifiable in the pre-detachment ME development of six marsupials and two monotremes. Also, differential ME positioning in the two monotreme species is not recapitulated. This challenges the developmental prerequisites of widely cited evolutionary scenarios of definitive mammalian middle ear (DMME) evolution, highlighting the requirement for further fossil evidence to test these hypotheses. Possible association between rear molar eruption, full ME ossification and ME detachment in marsupials suggests functional divergence between dentary and ME as a trigger for developmental, and possibly also evolutionary, ME detachment. The stable positioning of the dentary and ME supports suggestions that a ‘partial mammalian middle ear’ as found in many mammaliaforms—probably with a cartilaginous Meckel''s cartilage—represents the only developmentally plausible evolutionary DMME precursor.     

Evolution and functional significance of tendon ossification in woodcreepers (Aves: Passeriformes: Dendrocolaptinae)

The woodcreepers, a clade of scansorial, neotropical birds, are distinctive among passerines in having extensive tendon ossification. Dissection of 42 of the 50 species indicates that such ossification in the hindlimb is limited almost entirely to tendons of insertion of the crural muscles. Most crural muscles have ossifications, and in all but one the ossified tendons are long and thin. Preliminary dissection revealed a similar pattern among ossified wing tendons. Phylogenetic analysis suggests that extensive tendon ossification is a synapomorphy of the woodcreepers. The species of Dendrocincla, which form a clade, show secondary reduction of ossification in some tendons, which may be correlated with increased intraspecific variation and with an expansion of foraging habits and postures to include nonscansorial behaviors. In contrast, the larger woodcreepers, other than Drymornis bridgesii and Nasica longirostris, form a clade with virtually no loss in ossification or evidence of intraspecific variation, even in large series of two species. Phylogenetic losses do not occur for the primary flexor of the ankle (M. tibialis cranialis), whereas two extensors (Mm. fibularis longus and gastrocnemius pars lateralis) show a complex pattern of derivation and loss. Previous biomechanical studies demonstrate that ossification increases the stiffness of tendons, making them stretch less under a given force. These structural and phylogenetic patterns are consistent with the view that hindlimb tendon ossification in woodcreepers is an adaptation to resist increased forces that act to extend the limb during vertical climbing. © 1993 Wiley-Liss, Inc.     

Aspects of the biology of the icefish Dacodraco hunteri (Notothenioidei, Channichthyidae) in the Ross Sea, Antarctica

On the basis of five specimens, the icefish Dacodraco hunteri (Notothenioidei, Channichthyidae) is documented for the first time in the Ross Sea, Antarctica. Meristic counts and morphometric measurements are provided for this small, streamlined, laterally compressed species. D. hunteri has a weakly ossified skeleton with considerable cartilage in the skull. It has a partially persistent notochord and reduced amounts of bone in the vertebral column since the centra are incompletely constricted. Its weight in seawater averages only 1.28% of its weight in air and, as one of the lightest notothenioids, D. hunteri is probably a permanent inhabitant of the water column. The diet consists of relatively large specimens of the pelagic nototheniid fish Pleuragramma antarcticum. Accepted: 27 September 1998     

Ossified meniscus and cyamo-fabella in some fossil sloths: a morpho-functional interpretation

An articulated skeleton of Thalassocnus natans (Xenarthra : Nothrotheriidae) and a review of some other fossil sloths provide new information on sesamoid bones located at the knee joint. A sesamoid bone and an ossified meniscus have been identified at this joint. The cyamo-fabella (posterior sesamoid of the tibio-femoral articulation) of T. natans may act like a pulley through which the tendon of the m. gastrocnemius would have passed. The ossified meniscus, which is also present in Megatheriidae and Mylodontidae, could be related to the pedolateral stance and a large rotation of the knee joint during locomotion.