Chondrocranial Morphology Research Articles

A dysmorphic mouse model reveals developmental interactions of chondrocranium and dermatocranium.

The cranial endo and dermal skeletons, which comprise the vertebrate skull, evolved independently over 470 million years ago and form separately during embryogenesis. In mammals, much of the cartilaginous chondrocranium is transient, undergoing endochondral ossification or disappearing, so its role in skull morphogenesis is not well studied and it remains an enigmatic structure. We provide complete 3D reconstructions of the laboratory mouse chondrocranium from embryonic day (E) 13.5 through E17.5 using a novel methodology of uncertainty-guided segmentation of phosphotungstic enhanced 3D micro-computed tomography images with sparse annotation. We evaluate the embryonic mouse chondrocranium and dermatocranium in 3D, and delineate the effects of a Fgfr2 variant on embryonic chondrocranial cartilages and on their association with forming dermal bones using the Fgfr2cC342Y/+ Crouzon syndrome mouse. We show that the dermatocranium develops outside of and in shapes that conform to the chondrocranium. Results reveal direct effects of the Fgfr2 variant on embryonic cartilage, on chondrocranium morphology, and on the association between chondrocranium and dermatocranium development. Histologically, we observe a trend of relatively more chondrocytes, larger chondrocytes, and/or more matrix in the Fgfr2cC342Y/+ embryos at all timepoints before the chondrocranium begins to disintegrate at E16.5. The chondrocrania and forming dermatocrania of Fgfr2cC342Y/+ embryos are relatively large, but a contrasting trend begins at E16.5 and continues into early postnatal (P0 and P2) timepoints, with the skulls of older Fgfr2cC342Y/+ mice reduced in most dimensions compared to Fgfr2c+/+ littermates. Our findings have implications for the study and treatment of human craniofacial disease, for understanding the impact of chondrocranial morphology on skull growth, and potentially on the evolution of skull morphology.

Differential Effects of the Fgfr2c C342Y Mutation on Developing Cranial Cartilage

Crouzon syndrome is an autosomal dominant condition characterized by craniofacial anomalies in the absence of major hand and foot abnormalities. Although premature closure of the coronal suture is the focus of most studies of Crouzon syndrome, cartilage elements have also been described as anomalous. The Fgfr2cC342Y/+ Crouzon syndrome mouse model carries a cysteine to tyrosine substitution at amino acid position 342 (Cys342Tyr; C342Y) in Fgfr2, equivalent to one of the FGFR2 mutations commonly associated with Crouzon syndrome. This mutation results in constitutive activation of the receptor and is associated with up‐regulation of osteogenic differentiation and consequent skull deformities. Development of the bony skull of these mice is known to be affected, but is preceded by development of the chondrocranium, a cartilaginous skull whose elements either disappear, remain as cartilage, or ossify endochondrally. In conjunction with identified disparities in the size and shape of the chondrocranium between Fgfr2cC342Y/+ mice and unaffected Fgfr2c+/+ littermates throughout development, we analyzed the morphology and proliferative activity of chondrocytes of the nasal septum (mostly remains as cartilage), braincase floor (ossifies endochondrally), and lateral walls (disappears) of the chondrocranium at embryonic day 14.5 (E14.5) and E15.5 to determine the effects of the mutation on cartilage cells. Consistent with a larger chondrocranium, Fgfr2cC342Y/+ mice had relatively more chondrocytes in the nasal septum (p≤0.01) and lateral wall (p≤0.001) at E14.5. At E15.5 there were more chondrocytes in the lateral wall (p≤0.001) of Fgfr2c+/+ chondrocrania, but the cells of the lateral wall in Fgfr2cC342Y/+ mice were larger (p≤0.001) than in control (Fgfr2c+/+) mice at both timepoints. There were no differences between genotypes in either chondrocyte number or size in the braincase floor, however more proliferative activity was identified in Fgfr2c+/+ braincase floors at E14.5 (p≤0.001). No differences in proliferation were identified between genotypes in either the nasal septum or the lateral walls. Our data indicate that regions of the chondrocranium are differentially affected by the Fgfr2c C342Y mutation, potentially based on the fate of each cartilage. Disruption to the tightly regulated developmental processes of the chondrocranium including cell proliferation and hypertrophy can have significant and lasting effects on craniofacial development through direct effects on cartilage formation and the indirect effects of chondrocranial morphology on development of bone.

Is it heterochrony? Populational differences in tadpole of Corythomantis greeningi Boulenger, 1896 (Anura: Hylidae)

Abstract Corythomantis greeningi is a hylid widely distributed in the xerophilic and sub-humid morphoclimatic regions of northeastern Brazil. The morphology of C. greeningi tadpoles were described from specimens collected in the Bahia, however, we observed some differences in morphology of individuals from Piauí, northeastern Brazil. The tadpoles were collected during the 2019 rainy season and 14 individuals were used to compare the larval characters. We observed differences in external, internal oral and chondrocranial morphology in relation to specimens previously described, especially in oral disc, number and shape of oral cavity papillae and some chondrocranium structures, suggesting a heterochrony in the development of the species. Further studies involving a greater number of tadpoles at different stages, combined with genetic, acoustic, and morphological factors of adult may establish the variation degree of C. greeningi in different regions of northeastern Brazil.

Description of the chondrocranium of the silky shark Carcharhinus falciformis with comments on the cranial terminology and phylogenetic implications in carcharhinids (Chondrichthyes, Carcharhiniformes, Carcharhinidae).

The definition and scope of the genus Carcharhinus has undergone several changes over the years and recent molecular studies have questioned its monophyly by the inclusion of other carcharhinid genera. Although many descriptions of chondrocranium are available for Carcharhinus species, some inconsistences and divergences are found in the literature, mainly regarding the foramina of the orbital region. In this study, the chondrocranium of the silky shark, Carcharhinus falciformis, from specimens caught at the Brazilian coast and the terminology of its components is revised has been described. Chondrocrania of other Carcharhinus species and carcharhinid genera are also examined in order to investigate the phylogenetic significance of chondrocranial morphology. Three new anatomical terms and nine chondrocrania characters are proposed and described in detail. The chondrocranial morphology varies widely among Carcharhinus species mainly regarding the rostrum and nasal capsules. The chondrocrania of Prionace, Nasolamia, and Negaprion are similar to Carcharhinus species and reveal the need to further explore the relationships among these genera. Characters potentially informative for systematics are the shape of rostral node, the preorbital process, and the subethmoidal fossa, and the occurrence of an epiphyseal notch and foramen, and must be included in phylogenetic studies encompassing other carcharhiniforms.

Larval anatomy of Dendropsophus decipiens (A. Lutz 1925) (Anura: Hylidae: Dendropsophini) with considerations to larvae of this genus.

The Dendropsophus decipiens clade comprises four species: D. berthalutzae, D. decipiens, D. haddadi, and D. oliveirai. Tadpoles of these species were described, but data on their internal morphology are lacking. We provide the first description of the buccopharyngeal anatomy, chondrocranial morphology, and cranial, hyoid and hyobranchial musculature of the tadpole of D. decipiens. Larvae of D. decipiens are characterized by the absence of lingual papillae, presence of fan-like papilla on the buccal floor, presence of a single-element suprarostral cartilage, presence of a small triangular process at the basis of the processus muscularis, m. levator mandibulae lateralis inserted on the nasal sac, and m. subarcualis rectus II-IV with a single, continuous slip. Tadpoles are likely macrophagous, although not as specialized as those of other species of the genus, suggesting some degree of diversification on the feeding habits within Dendropsophus.

Internal Larval Morphology of Two Species of Shining Leaf Frogs (Anura: Phyllomedusidae: Phasmahyla)

We describe the buccal cavity and chondrocranial morphology of Phasmahyla cruzi tadpoles in comparison to P. guttata. We also provide a review of some characters for larval phyllomedusids and discuss some evolutionary aspects related to the funnel-mouthed configuration. Our discussion highlights that several characters evolved independently in several taxa with umbelliform oral discs. Nevertheless, we suggest that the dorsal orientation of the suprarostral cartilage and the presence of a prenarial ridge on the buccal roof may represent synapomorphic character states for the genus Phasmahyla.

Chondrocranium and internal oral morphology of the tadpole of Corythomantis greeningi (Anura: Hylidae)

Corythomantis greeningi is a casque-headed frog that occurs in xeric and sub-humid regions of northeastern Brazil. Individuals are often found on rocks on banks of temporary streams or in ponds upon “lajedos”. Suctorial tadpoles are often found clasping to the rocks in the streams so as not to be dragged by the current; therefore, they have modified external and internal morphology. Here, we describe the internal oral anatomy and the chondrocranium of the tadpole of C. greeningi and compare it to the available descriptions of Lophyohylinae and other suctorial tadpoles. The internal oral morphology in C. greeningi resembles pond-dwelling casque-headed frogs, although it has been found in temporary lotic environments. Corythomantis greeningi has unusual chondrocranial morphology relative to that of other described Lophyohylinae, including marked differences at the cornua trabeculae and palatoquadrate. Apparently, the chondrocranial morphology is related to its ecomorphology, because it is structurally more similar to other suctorial tadpoles that inhabit lotic environments than to phylogenetically related species such as Trachycephalus typhonius and Phyllodytes gyrinaethes

Chondrocranial Morphology of the Salmon Shark,Lamna ditropis, and the Porbeagle,L. nasus(Lamnidae)

Adult chondrocranial morphology is poorly documented in modern lamniform sharks. Here it is described for the two extant species of Lamna, L. nasus and L. ditropis. Several features are noted and discussed, including hypercalcification of the rostral cartilages, the ethmoidal region associated with ligamentous jaw attachments, and the configuration of the postorbital region. The small polygonal blocks of calcified cartilage (tesserae) that typically line the chondrichthyan endoskeleton are greatly thickened in the rostral bars of Lamna, forming radial columns; furthermore, concentric banding of the columnar calcification in the rostrum of L. ditropis suggests periodic accretion of new calcified tissue below the perichondrium. The postorbital region in Lamna is notable for lacking a postorbital process, and in having the supraorbital shelf continuing posteriorly as a supra-otical shelf, which extends as far as the hyomandibular fossa. The orbit in Lamna is apparently not drained in the usual elasmobranch m...

External morphology, chondrocranium, hyobranchial skeleton, and external and internal oral features of <i>Rhinoderma rufum</i> (Anura, Rhinodermatidae)

The species of Rhinoderma Duméril & Bibron are endemic to the temperate forests of South America in southern Chile and Argentina (Formas et al. 1975). Both have specialized reproductive modes, Rhinoderma darwinii Duméril & Bibron undergoes complete embryonic and larval development in the mouth of the male: newly metamorphosed frogs are expelled into the terrestrial environment (Jorquera et al. 1972). In contrast, embryos of R. rufum (Philippi) do not remain in the male's mouth, but instead are expelled into the water as larvae (Jorquera et al. 1974). Jorquera et al. (1972, 1974) described the normal development of both species. The chondrocranial morphology and visceral skeleton of R. darwinii was described by Lavilla (1987) and its internal oral features by Wassersug & Heyer (1988). The table of normal development of R. rufum (Jorquera et al. 1974) emphasized the duration of each stage of development: however, some features currently used for comparative purposes in tadpole morphological studies were not included or described only briefly. In this work, I include a detailed description of the morphology, particularly of the mouthparts, of the tadpoles of R. rufum, and describe the chondrocranium, hyobranchial skeleton, and the internal features of the oral cavity in this species. In addition, I compare the morphology of the mouth, chondrocranium, and hyobranchial skeleton of the congeneric tadpoles, considering different modes of feeding (endotrophic in R. darwinii versus exotrophic in R. rufum). Last, I present some thoughts about the evolution of larvae of Rhinoderma.

Morphology and ecology of tadpoles of <i>Ramanella obscura</i> (Anura: Microhylidae)

External, buccal and chondrocranial morphology, bone development and ecology of the tadpoles of Ramanella obscura, a narrow-mouthed frog species endemic to Sri Lanka is described. The tadpoles have a dorsoventrally flattend body, keratinous ridge on lower lip, a postnarial ridge that extends anteriorly between narial papillae and an expanded fenestrated sheet of cartilage associated with the larval otic process and processus lateralis posterior. But they do not possess a medial preglottal papilla in ventral buccal floor as in Microhyla. At Gosner stage 25, there is no bone development; but by stage 35, exoccipitals, parasphenoid, frontoparietals and prootics are developed. By stage 40, in addition to the bones at stage 35, nasals are formed. The tadpoles are tree-hole or small-ground-pool dwellers that feed on particulate matter and infusoria both in the substratum and the water column, for which they have morphological adaptations. No other anuran tadpoles were observed in syntopy with R. obscura tadpoles. Key words: Chondrocranium; buccal morphology; tadpole ecology; endemic; Sri Lanka DOI: http://dx.doi.org/10.4038/cjsbs.v40i2.3927 CJSBS 2011; 40(2): 109-120

Osteologia e morfologia do condrocrânio de Gastrophryne carolinensis (Anura: Microhylidae), com uma revisão da diversidade osteológica dos Microhylidae do Novo Mundo.

Osteology and chondrocranial morphology of Gastrophryne carolinensis (Anura: Microhylidae), with a review of the osteological diversity of New World microhylids. Microhylidae is a large, cosmopolitan anuran family. Recent molecular analyses have demonstrated the monophyly of the family—a conclusion that is supported by the larval morphology, coupled with the unique mode of tongue protrusion in adults, and a suite of osteological and myological characters seemingly associated with this innovation in feeding. Despite this functional constraint, osteological diversity probably exceeds that of any other anuran family, and this diversity is especially evident in the New World microhylids that comprise two clades, Gastrophryninae and Otophryninae. To facilitate comparisons among these clades, we describe the larval chondrocranium, skeletal development, and adult osteology of Gastrophryne carolinensis. We provide a phylogenetic context for these comparisons through a novel phylogenetic analysis of 45 microhylid genera based on data for one mitochondrial and three nuclear loci from previously published studies. Nearly all relationships within the monophyletic Gastrophryninae are resolved with robust support. Based on these results, we found that the larval chondrocrania of gastrophrynines share morphological features that distinguish them from Otophryne and other anurans. Among the adults, all gastrophrynines show evidence of an anterior shift of the jaws that is correlated with specializations in the otic region, and with the alignment of the planum antorbitale, the cartilage wall separating the nasal capsule from the orbits. The

The chondrocrania of North American Rana larvae (Anura: Ranidae): a morphological comparison

AbstractA detailed morphological description of the chondrocranium is provided for the larvae of six species of North American Rana. Results indicated that although qualitative variation in chondrocranial morphology was limited among the larval Rana examined here, R. sylvatica is clearly distinguishable from other species based on the presence of a shorter articular process of the palatoquadrate, a wider muscular process of the palatoquadrate, and a more posterior position of attachment of the larval otic process to the palatoquadrate. These conditions are similar to those found in the Eurasian R. temporaria. Rana clamitans and R. catesbeiana are distinguished by a considerably narrower palatoquadrate in the region posterior to the anterior quadratocranial commissure, a more anterior position of attachment of the larval otic process to the palatoquadrate, and the presence of a lateral trabecular process in some specimens. These characters may represent larval synapomorphies for the traditional R. catesbeiana group (=Aquarana).

Ontogeny, phylogeny, and morphology in anuran larvae: Morphometric analysis of cranial development and evolution inRana tadpoles (Anura: Ranidae)

Comparative studies of chondrocranial morphology in larval anurans are typically qualitative in nature, focusing primarily on discrete variation or gross differences in the size or shape of individual structures. Detailed data on chondrocranial allometry are currently limited to only two species, Rana sylvatica and Bufo americanus. This study uses geometric morphometric and multivariate statistical analyses to examine interspecific variation in both larval chondrocranial shape and patterns of ontogenetic allometry among six species of Rana. Variation is interpreted within the context of hypothesized phylogenetic relationships among these species. Canonical variates analyses of geometric morphometric datasets indicate that species can be clearly discriminated based on chondrocranial shape, even when whole ontogenies are included in the analysis. Ordinations and cluster analyses based on chondrocranial shape data indicate the presence of three primary groupings (R. sylvatica; R. catesbeiana + R. clamitans; and R. palustris + R. pipiens + R. sphenocephala), and patterns of similarity closely reflect phylogenetic relationships. Analysis of chondrocranial allometry reveals that some patterns are conserved across all species (e.g., most measurements scale with negative allometry, those associated with the posterior palatoquadrate tend to scale with isometry or positive allometry). Ontogenetic scaling along similar allometric trajectories, lateral transpositions of individual trajectories, and variable allometric relationships all contribute to shape differences among species. Overall patterns of similarity among ontogenetic trajectories also strongly reflect phylogenetic relationships. Thus, this study demonstrates a tight link between ontogeny, phylogeny, and morphology, and highlights the importance of including both ontogenetic and phylogenetic data in studies of chondrocranial evolution in larval anurans.

The tadpoles of Alsodes vanzolinii and A. verrucosus (Anura: Leptodactylidae) with descriptions of their internal oral and chondrocranial morphology

AbstractThe tadpoles of Alsodes vanzolinii and A. verrucosus are described. The descriptions include external, oral cavity, and chondrocranial morphology. The external characteristics, and those of the internal oral morphology, are useful in the specific diagnosis.

Chondrocranial morphology and ontogenetic allometry in larval Bufo americanus (Anura, Bufonidae)

Available descriptions of chondrocranial morphology among larvae of Bufo species are inconsistent, the range of variation in chondrocranial structure is not well defined, and no detailed quantitative descriptions of cranial ontogeny currently exist for any species of the genus. This study describes chondrocranial morphology in larval Bufo americanus based on three samples of tadpoles and provides comparisons with other species of Bufo. Additionally, this study provides the first data on ontogenetic allometry of the chondrocranium in Bufo and demonstrates fine-scale intraspecific shape variation among samples of B. americanus larvae. Chondrocranial morphology in B. americanus is overall similar to that reported for larvae of other members of the genus. Morphometric analyses indicate that although chondrocranial shape differs consistently among samples from three localities, patterns of ontogenetic allometry are conserved. Common principal components analysis of the chondrocranial measurements indicates a mixture of allometric and isometric scaling. Measurements associated with the oral region, braincase, and otic capsule tend to scale with negative allometry, whereas those associated with the posterior palatoquadrate and insertion sites for the major jaw and buccal muscles scale with isometry or positive allometry. These data provide further evidence that the anuran chondrocranium is not a static structure during premetamorphic stages. Furthermore, these patterns are similar to those previously reported for Rana sylvatica, suggesting the hypothesis that these allometries may represent a general pattern in larval anurans.

Chondrocranial, hyobranchial and internal oral morphology in larvae of the basal bufonid genus Melanophryniscus (Amphibia: Anura)

Abstract Melanophryniscus is a genus of small toads inhabiting the southern portion of South America. This genus is considered basal within the family Bufonidae. Data on larval chondrocranial morphology do not exist for the genus and larval internal oral anatomy has only been described for a single species. Here, we describe chondrocranial and internal oral morphology in Melanophryniscus montevidensis , M. orejasmirandai and M. sanmartini . Chondrocranial morphology is similar among the species examined. Comparisons with other bufonids and with outgroup taxa suggest that the following chondrocranial characters may represent synapomorphies for the Bufonidae: free (or absent) ceratobranchial IV, a reduced or absent larval crista parotica, the lack of a larval otic process, and late development of thin, poorly chondrified orbital cartilages. The presence of an elongated processus anterior dorsalis of the suprarostral alae and the absence of a chondrified commissura quadratoorbitalis appear to be unique in Melanophryniscus among bufonids. Internal oral anatomy is conserved in Melanophryniscus , and among bufonids in general.

Chondrocranial morphology of Leptodactylus larvae (Leptodactylidae: Leptodactylinae): Its utility in phylogenetic reconstruction.

Chondrocranial morphology of leptodactylid frogs is scarcely known and has not been completely described for any species of Leptodactylus. We describe the diversity of chondrocranial morphology in the genus Leptodactylus based on the analysis of 22 species, representing the four species groups: the fuscus Group, ocellatus Group, melanonotus Group, and pentadactylus Group. Furthermore, 26 characters are identified and used in a phylogenetic analysis. The phylogenetic analysis using Physalaemus, Crossodactylus, and Hylodes as outgroups suggests two monophyletic clades within Leptodactylus: the melanonotus-ocellatus clade and the pentadactylus-fuscus clade. However, it does not support the monophyly of the species groups as currently recognized and it suggests a paraphyletic Leptodactylus. Enforcing the monophyly of the ingroup, i.e., Leptodactylus, results in the same major two clades of Leptodactylus. Leptodactylus riveroi, a taxon previously unassigned to any species group, appears most closely related to the melanonotus-ocellatus clade based on chondrocranial characteristics. J. Morphol. 238:287-305, 1998. © 1998 Wiley-Liss, Inc.

Some Consequences of Transformations in Siluriform Chondrocrania: a Case Study of Clarias Gariepinus (Burchell, 1822) (Siluriformes: Clariidae)

Several catfishes, or siluriforms, have become adapted to a benthic and nocturnal life style. Eyes have become small, whereas oral barbels and the Weberian apparatus compensate for the loss in visibility. The head has become dorso-ventrally flattened, which improves benthic stability. To give an idea of the network of consequences of such adaptations, which arise early during ontogeny, four topics are discussed. (1) Siluriformes have a platybasic skull instead of a tropibasic skull, found in most teleosts. This difference seems to be the result of a reduction in eye diameter, and has some consequences on the general form of the head, the ethmoid region and the functionality of the adductor arcus palatini muscle. (2) In Siluriformes, some general trends seem to occur in the chondrocranial roof morphology, which influence the path of some nerves. (3) Some transformations of existing structures have become part of a palatine-maxillary mechanism, which enables controlled movements of the maxillary barbels. (4) The interhyal frequently disappears during ontogeny in catfishes, which seems to be of some functional significance, again as an adaptation to a benthic life style.

Galeus gracilis n.sp., a new sawtail catshark from Australia, with comments on the systematics of the genus Galeus Rafinesque, 1810 (Carcharhiniformes: Scyliorhinidae)

Galeus gracilis n.sp. (Scyliorhinidae: Pentanchinae: Galeini) is described from the uppermost slope of Western Australia and the Northern Territory. It is the second recognised member of its genus from Australian waters. This small, slender-bodied Galeus is distinguished from the 12 other species in the genus by a combination of proportional dimensions, tooth-row counts, clasper morphology, pectoral-fin radial counts, vertebral counts, intestinal valve counts, chondrocranial morphology, and colouration. It is closest to three Japanese species: G. eastmani, G. longirostris and G. nipponensis. Galeus gracilis is compared in detail to G. boardmani from southern Australia, which differs from it in numerous features.

Hemitriakis falcata n.sp. and H. abdita n.sp., two new houndsharks (Carcharhiniformes: Triakidae) from Australia

Two new species of the genus Hemitriakis Herre, 1923 (Carcharhiniformes: Triakidae) are described from tropical Australia. Hemitriakis falcata is described from ten specimens from the outer continental shelf of Western Australia at depths of 146 to 197 m. Hemitriakis abdita is described from five specimens from the Coral Sea Plateau off north-eastern Queensland at 225 to 401 m. Hemitriakis falcata and H. abdita are separable from their two named congeners H. leucoperiptera, from the Philippine Islands, and H. japanica, from Japan, Taiwan, China and Korea, by a combination of vertebral counts, first dorsal position, fin and eye shape, and juvenile colouration. Hemitriakis falcata additionally differs from H. japanica in chondrocranial morphology. Hemitriakis falcata and H. abdita are sibling species separated by wide, non-overlapping differences in vertebral counts as well as by slight differences in morphometrics, tooth counts, colouration, and cranial morphology. These species represent the first record of Hemitriakis from Australia. A nominal record of H. japanica from Ambon is uncertain while another record of H. japanica from New Caledonia may be based on H. abdita. A key to species of Hemitriakis is presented.