Ceratophrys Cranwelli Research Articles

Surgically Treated Hind-Limb Fibromyxochondroma in a Cranwell’s Horned Frog (Ceratophrys cranwelli)

Ceratophrys cranwelli, commonly known as the Cranwell’s horned frog or Pacman frog, is an amphibian species native to South America. This species has gained interest both as a pet among hobbyists and as a subject of scientific inquiry in veterinary medicine. A two-year-old pet male albino Ceratophrys cranwelli was presented exhibiting lethargy, weight loss, and anorexia, persisting for two months. Clinical examination revealed a fracture localized to the proximal third of the left femur accompanied by an osteolytic process. The patient was discharged with a treatment regimen for suspected secondary nutritional hyperparathyroidism and an ulcerative skin lesion. Nevertheless, due to the progressive deterioration of the left thigh, amputation of the affected limb was proposed and performed at the coxofemoral joint. Histopathological analysis of the excised mass revealed an atypical mesenchymal mass consistent with a fibromyxochondroma. The surgical procedure was conducted under anesthesia induced by a combination of alfaxalone, ketamine, medetomidine, and butorphanol, with postoperative treatment consisting of enrofloxacin, meloxicam, and butorphanol. The patient showed good post-surgical recovery, exhibiting normal physiological and behavioral activities. This report highlights the management and the diagnostic challenges of a progressive limb lesion in a Ceratophrys cranwelli, offering insights into potential therapeutic approaches for similar cases in amphibians.

Reference intervals for hematology, plasma biochemistry, and bone mineral density in captive Ceratophrys cranwelli (Anura: Ceratophryidae)

Hematology, plasma biochemistry, body composition, and bone mineral density (BMD) were analyzed for 30 captive Ceratophrys cranwelli (C. cranwelli) to establish the reference intervals. There was no significant difference between males and females in all blood routine tests. Blood biochemistry included 17 analytes, and only total bile acid (TBA), calcium (CA), and phosphorus (PHOS) showed significant differences. Male TBA levels were higher than females, while female CA and PHOS levels were higher than males. The body composition and BMD of males and females were similar, except for bone area, which showed a significant gender difference, with females having higher values than males. The data obtained in this study can help with the medical management of diseased individuals and serve as a reference for health assessments of future populations.

Vascularization inside the epidermis of Neotropical anurans (Nobleobatrachia).

Anuran skin is a dynamic organ involved in essential functions that strongly correlate with specific morphological traits. Particularly, gas exchange has been associated with epidermal modifications, such as reduced cell layers and increased vascularization. Here, we describe the epidermal morphology and its association with capillary networks in the dorsal skin of 103 Neotropical anurans (Nobleobatrachia) from different ecomorphs and habitats. Additionally, we examined the lateral and ventral skin for a subset of these species. We report intraepidermal capillaries in (i) dorsal skin of Lepidobatrachus laevis and Lepidobatrachus llanensis (burrowing and semi-aquatic Chacoan species), Hyloscirtus colymba and Hyloscirtus palmeri (arboreal species from humid forests), and Alsodes neuquensis and 15 Telmatobius spp. (aquatic and semi-aquatic species from cold environments); (ii) lateral skin of Boana benitezi and H. colymba (arboreal species from humid forests), and (iii) ventral skin of B. benitezi, H. colymba, Atelognathus patagonicus (aquatic species from cold environments), and four Chacoan species, Chacophrys pierottii, Ceratophrys cranwelli (burrowing/terrestrial species), and Lepidobatrachus asper and L. llanensis (burrowing/semi-aquatic species). Also, verrucae hydrophilicae were observed exclusively in the ventral skin of Leptodactylus fuscus, Leptodactylus laticeps (terrestrial and Chacoan species), and B. benitezi. Regardless of the skin region, the capillaries always penetrate the epidermis from the dermis, while epidermal cell layers are flattened. Our findings support previous hypotheses stating that the environment where species occur influences skin changes related to cutaneous respiration (intraepidermal capillaries in different body regions) and water absorption (intraepidermal capillaries associated with verrucae hydrophilicae within ventral skin). Also, phylogeny might influence the development of these structures, as revealed by the presence of intraepidermal capillaries in almost all analyzed species of Telmatobius. Finally, the co-occurrence of verrucae hydrophilicae in the ventral skin of hylids from humid forests, and leptodactylids from the subhumid Chacoan region suggest an independent origin.

Sustained force production by the jaw-adductor muscles of a megalophagous frog, Ceratophrys cranwelli.

Most frogs have weak jaws that play a relatively minor role in tongue-mediated prey capture. Horned frogs (Ceratophrys spp.), however, follow the projection of a large tongue with a vice-like grip of their jaws to hold and immobilize prey. Prey include relatively large vertebrates, which they may restrain for minutes to possibly hours. High endurance behaviors, such as prolonged biting, require that muscles be capable of sustained force production. The feeding behavior of Ceratophrys suggests that their jaw-adductor muscles may be capable of powering sustained bites for long periods. We examined the capacity for sustained bite force by conducting an in situ experiment during which we measured bite force while bilaterally and supramaximally stimulating the jaw-adductor muscles of euthanized Cranwell's horned frogs (C. cranwelli). Muscles were stimulated for at least 60 min with a series of tetanic trains, with one experiment lasting over 6 h. We found that a significant sustained force develops during the first few minutes of the experiment, and this force is present between tetanic trains when the muscles are not being stimulated. The sustained force persists long after tetanic forces are barely detectable. The observed sustained force phenomenon parallels that observed for the jaw-adductor muscles of alligator lizards (Elgaria), another animal capable of sustained biting. The ability to bite with sustained and significant force by C. cranwelli may be facilitated by a configuration of different muscle fiber types, such as slow tonic fibers, as well as specializations in the muscle fibers that mitigate the effects of fatigue.

Influence of Prey Availability in the Dissimilarity of Predator–Prey Interactions

Photo 1. Majority of anurans feed on arthropods, like the Oval Frog (Elachistocleis matogrosso), an ant specialist. Photo credit: Karoline Ceron. Photo 2. But there are some exceptions, such as the Cranwell's horned frog (Ceratophrys cranwelli), a voracious predator, attempting predation upon a Pigmy Toad (Rhinella bergi) in Brazilian Chaco. Photo credit: Karoline Ceron. Photo 3. Anuran diet can vary throughout space, for example, between ecoregions. Nhecolândia, a subregion of the Pantanal, is characterized by the coexistence of thousands of lakes called baías (freshwater) and salinas (waters of alkaline composition; upper panel), in contrast, the Chaco ecoregion has a flat topography, a semiarid climate, and distinct plant formations (lower panel). Photo credit: Karoline Ceron. Photo 4. Also, the anuran diet can vary throughout time, for example, between seasons. Brazilian Cerrado, a seasonal ecoregion, at the RPPN Estância Mimosa, Mato Grosso do Sul, Brazil, during the rainy season (upper panel) and the dry season (lower panel). Photo credit: Karoline Ceron. Photo 5. Studying these variations in time and space, we found that the dissimilarity of the anuran-prey network between ecoregions and seasons is primarily driven by interaction rewiring, which is determined by the variation in prey availability. A waxy monkey frog (Phyllomedusa sauvagii) in the RPPN Estância Mimosa, Mato Grosso do Sul, Brazil. Photo credit: Karoline Ceron. These photographs illustrate the article “Differences in prey availability across space and time lead to interaction rewiring and reshape a predator–prey metaweb” by Karoline Ceron, Diogo B. Provete, Mathias M. Pires, Andrea C. Araujo, Nico Blüthgen, and Diego J. Santana published in Ecology. https://doi.org/10.1002/ecy.3716

Contributions to the knowledge of parasitic nematodes of amphibians from the Dry Chaco ecoregion of Argentina

In the Argentinean Gran Chaco, numerous investigations have dealt with the diversity of vertebrates, including herps. As for the parasitofauna of these organisms, some groups, such as amphibians, have been more studied; however, from a biogeographic perspective, most of these studies were carried out in a different area, the Humid Chaco. The goal of this work is to present the nematofauna found in six species of amphibians, namely Rhinella diptycha , Chacophrys pierottii , Ceratophrys cranwelli , Scinax nasicus , Leptodactylus bufonius , and Odontophrynus lavillai , collected in different locations within the Dry Chaco, in the department of Matacos, Formosa, Argentina. In a total of 34 amphibians analyzed, we found 1,526 nematode parasites (total prevalence: 61.7%; total mean intensity: 72.6±90.3; total mean abundance: 46.2±79.7), belonging to 9 taxa: adults of Rhabdias sp., Oswaldocruzia sp., O. subauricularis , Schulzia travassossi , Aplectana hylambatis , Cosmocerca podicipinus , Oxyascaris caudacutus , Schrankiana formosula , and larvae of Physaloptera sp. These nematodes were collected from the lungs, small intestine, large intestine, gastric mucosa, and gallbladder of hosts. This work is the first record of helminths from C. pierottii and O. lavillai and the first record of nematodes from Ce. cranwelli throughout its geographical range. The species Oswaldocruzia subauricularis (Molineidae) and Schrankiana formosula (Atractidae) are recorded for the first time in Argentinean amphibians. Thus, we expand the knowledge of the biological diversity of helminth parasites of amphibians; this information, integrated into future and more comprehensive studies, will allow us to understand the factors that influence the patterns of host and geographic distribution, in an area with such extreme characteristics as the Dry Chaco.

Evolutionary and developmental considerations of the diet and gut morphology in ceratophryid tadpoles (Anura)

BackgroundBefore metamorphosis, almost all anuran tadpoles are omnivores. Larval carnivory occurs in some species and, it is associated with distinctive morphotypes. Obligatory carnivorous tadpoles exhibit structural changes in the gastrointestinal tract compared to larvae that are predominately omnivores. The most distinctive feature of the anuran family Ceratophyridae (three genera) overall is the enormous gape of adults. This feature increases their ability to capture extremely large and active prey. The larvae of Ceratophyrid genera are remarkably distinct from each other and carnivory has diversified in a manner unseen in other anurans. The larvae of one genus, Lepidobatrachus, has a massive gape like the adult. Herein, we report on larval developmental variation, diet, gross morphology of the gastrointestinal tract, and histology of the cranial segment of the gut before, during and after metamorphosis in larval series for the following ceratophryid species: Chacophrys pierottii, Ceratophrys cranwelli, Lepidobatrachus laevis and Lepidobatrachus llanensis.ResultsWe described patterns of larval development with variation in growth with consequence to the final size at the end of metamorphosis. These patterns seem to be influenced by food quantity/quality, and most predominant by animal protein. Prey items found in pre and post-metamorphic Lepidobatrachus spp. are similar. Tadpoles of Ceratophrys and Chacophrys (and other anurans) share a short cranial segment of the gut with an internal glandular, mucous secreting epithelium, a double coiled intestine and the sequence of metamorphic changes (tract is empty, the stomach differentiates and the intestine shortens abruptly). In contrast, Lepidobatrachus tadpoles have a true stomach that acquires thickness and increased glandular complexity through development. As larvae they have a short intestine without double coils, and the absence of intestine shortening during metamorphosis.ConclusionsThe larval development of the gastrointestinal tract of Lepidobatrachus is unique compared with that of other free-living anuran larvae. An abrupt metamorphic transformation is missing and most of the adult structural features start to differentiate gradually at the beginning of larval stages.

Comparative and functional analysis of the digital mucus glands and secretions of tree frogs

BackgroundMucus and mucus glands are important features of the amphibian cutis. In tree frogs, the mucus glands and their secretions are crucial components of the adhesive digital pads of these animals. Despite a variety of hypothesised functions of these components in tree frog attachment, the functional morphology of the digital mucus glands and the chemistry of the digital mucus are barely known. Here, we use an interdisciplinary comparative approach to analyse these components, and discuss their roles in tree frog attachment.ResultsUsing synchrotron micro-computer-tomography, we discovered in the arboreal frog Hyla cinerea that the ventral digital mucus glands differ in their morphology from regular anuran mucus glands and form a subdermal gland cluster. We show the presence of this gland cluster also in several other—not exclusively arboreal—anuran families. Using cryo-histochemistry as well as infrared and sum frequency generation spectroscopy on the mucus of two arboreal (H. cinerea and Osteopilus septentrionalis) and of two terrestrial, non-climbing frog species (Pyxicephalus adspersus and Ceratophrys cranwelli), we find neutral and acidic polysaccharides, and indications for proteinaceous and lipid-like mucus components. The mucus chemistry varies only little between dorsal and ventral digital mucus in H. cinerea, ventral digital and abdominal mucus in H. cinerea and O. septentrionalis, and between the ventral abdominal mucus of all four studied species.ConclusionsThe presence of a digital mucus gland cluster in various anuran families, as well as the absence of differences in the mucus chemistry between arboreal and non-arboreal frog species indicate an adaptation towards generic functional requirements as well as to attachment-related requirements. Overall, this study contributes to the understanding of the role of glands and their secretions in tree frog attachment and in bioadhesion in general, as well as the evolution of anurans.

The ontogeny of the olfactory system in ceratophryid frogs (Anura, Ceratophryidae).

The aquatic-to-terrestrial shift in the life cycle of most anurans suggests that the differences between the larval and adult morphology of the nose are required for sensory function in two media with different physical characteristics. However, a better controlled test of specialization to medium is to compare adult stages of terrestrial frogs with those that remain fully aquatic as adults. The Ceratophryidae is a monophyletic group of neotropical frogs whose diversification from a common terrestrial ancestor gave rise to both terrestrial (Ceratophrys, Chacophrys) and aquatic (Lepidobatrachus) adults. So, ceratophryids represent an excellent model to analyze the morphology and possible changes related to a secondary aquatic life. We describe the histomorphology of the nose during the ontogeny of the Ceratophryidae, paying particular attention to the condition in adult stages of the recessus olfactorius (a small area of olfactory epithelium that appears to be used for aquatic olfaction) and the eminentia olfactoria (a raised ridge on the floor of the principal cavity correlated with terrestrial olfaction). The species examined (Ceratophrys cranwelli, Chacophrys pierottii, Lepidobatrachus laevis, and L. llanensis) share a common larval olfactory organ composed by the principal cavity, the vomeronasal organ and the lateral appendix. At postmetamorphic stages, ceratophryids present a common morphology of the nose with the principal, middle, and inferior cavities with characteristics similar to other neobatrachians at the end of metamorphosis. However, in advanced adult stages, Lepidobatrachus laevis presents a recessus olfactorius with a heightened (peramorphic) development and a rudimentary (paedomorphic) eminentia olfactoria. Thus, the adult nose in Lepidobatrachus laevis arises from a common developmental 'terrestrial' pathway up to postmetamorphic stages, when its ontogeny leads to a distinctive morphology related to the evolutionarily derived, secondarily aquatic life of adults of this lineage.

Bite force in the horned frog (Ceratophrys cranwelli) with implications for extinct giant frogs

Of the nearly 6,800 extant frog species, most have weak jaws that play only a minor role in prey capture. South American horned frogs (Ceratophrys) are a notable exception. Aggressive and able to consume vertebrates their own size, these “hopping heads” use a vice-like grip of their jaws to restrain and immobilize prey. Using a longitudinal experimental design, we quantified the ontogenetic profile of bite-force performance in post-metamorphic Ceratophrys cranwelli. Regression slopes indicate positive allometric scaling of bite force with reference to head and body size, results that concur with scaling patterns across a diversity of taxa, including fish and amniotes (lizards, tuatara, turtles, crocodylians, rodents). Our recovered scaling relationship suggests that exceptionally large individuals of a congener (C. aurita) and extinct giant frogs (Beelzebufo ampinga, Late Cretaceous of Madagascar) probably could bite with forces of 500 to 2200 N, comparable to medium to large-sized mammalian carnivores.

Exploring Antipredator Mechanisms: New Findings in Ceratophryid Tadpoles

Abstract Previous studies found that two larvae of the family Ceratophryidae, Ceratophrys ornata (Ornate Horned Frogs) and Ceratophrys cranwelli (Cranwell's Horned Frogs), are able to produce underwater sounds as an antipredator strategy. Here, we determined whether tadpoles of another ceratophryid, Lepidobatrachus llanensis (Llanos Frogs), also produce underwater sounds in similar contexts of intraspecific interactions. Moreover, to compare the mechanism displayed by Ceratophrys spp. with related species, we tested the existence of an antipredator mechanism (= behavior) in L. llanensis tadpoles that diminishes the frequency of predation between conspecifics in the presence of heterospecific prey. Lepidobatrachus llanensis tadpoles exhibited an antipredator mechanism that is displayed on intraspecific interactions. Extensive trials failed to reveal sound production (in the 20 hertz [Hz]–20 kilohertz [kHz] range) in L. llanensis, contrasting our observations on Ceratophrys spp. Nevertheless, L. llanensis t...

Ontogenetic shifts in ambush-site selection of a sit-and-wait predator, the Chacoan Horned Frog (Ceratophrys cranwelli)

Ontogenetic shifts in habitat use are widespread among vertebrates. These niche shifts are often attributed to age-specific patterns of resource use, which are correlated with changes in morphology, diet, and habitat. We examined the ontogeny of ambush-site selection in a sit-and-wait predator, the Chacoan Horned Frog (Ceratophrys cranwelli Barrio, 1980), in the Gran Chaco ecoregion of Bolivia. We quantified covariation in microhabitat and morphological variables and tested for microhabitat selection against randomly selected points. We identified an ontogenetic shift in ambush-site selection between adult and metamorph frogs. When compared with random points, metamorphs selected a subset of available habitat, whereas adult frogs did not appear to select ambush sites. Metamorphs, compared with adults, selected ambush sites farther from a pond’s edge with a greater proportion of dry mud. The metamorph of C. cranwelli may have selected ambush sites based on spatial distribution of certain size classes of prey. Alternatively, metamorphs could have selected sites to minimize asymmetric agonistic intraspecific interactions with adults. These mechanisms are not mutually exclusive and probably occur in concert. Habitat selection and ontogenetic niche shifts by these organisms provide insights to the trade-offs between foraging strategy and mortality risk.

Underwater sound emission as part of an antipredator mechanism in Ceratophrys cranwelli tadpoles

AbstractWe report the emission of underwater sounds in the tadpoles of a second member of the family Ceratophryidae, Ceratophrys cranwelli. These tadpoles produce a short metallic‐like sound, which consists of short trains of pulses at Gosner stages 25, 28, and 37. Experiment I was designed to record underwater sounds and their characteristics. Experiment II was designed to test: (i) if at higher densities (total number of tadpoles/L) but fixed predator–prey proportions C. cranwelli larvae are cannibalistic, (ii) if cannibalism increases at higher proportions of predators at a fixed density, and (iii) if tadpoles display a mechanism of intraspecific recognition that may diminish the frequency of cannibalism. Each treatment combines larvae of C. cranwelli (predator) with those of Rhinella arenarum (prey). The number of live and dead individuals was recorded during 72 h, and the following variables were calculated: time to eat the first and second prey, time without eating, time to eat a congener, and number of events of cannibalism. The results indicate that relative predator–prey availability affects the frequency of predation between conspecifics. We consider that an antipredator mechanism exists in C. cranwelli tadpoles and that the underwater sound is part of it.

Developmental origins of a novel gut morphology in frogs.

Phenotypic variation is a prerequisite for evolution by natural selection, yet the processes that give rise to the novel morphologies upon which selection acts are poorly understood. We employed a chemical genetic screen to identify developmental changes capable of generating ecologically relevant morphological variation as observed among extant species. Specifically, we assayed for exogenously applied small molecules capable of transforming the ancestral larval foregut of the herbivorous Xenopus laevis to resemble the derived larval foregut of the carnivorous Lepidobatrachus laevis. Appropriately, the small molecules that demonstrate this capacity modulate conserved morphogenetic pathways involved in gut development, including downregulation of retinoic acid (RA) signaling. Identical manipulation of RA signaling in a species that is more closely related to Lepidobatrachus, Ceratophrys cranwelli, yielded even more similar transformations, corroborating the relevance of RA signaling variation in interspecific morphological change. Finally, we were able to recover the ancestral gut phenotype in Lepidobatrachus by performing a reverse chemical manipulation to upregulate RA signaling, providing strong evidence that modifications to this specific pathway promoted the emergence of a lineage-specific phenotypic novelty. Interestingly, our screen also revealed pathways that have not yet been implicated in early gut morphogenesis, such as thyroid hormone signaling. In general, the chemical genetic screen may be a valuable tool for identifying developmental mechanisms that underlie ecologically and evolutionarily relevant phenotypic variation.

Developmental origins of novel gut morphology in frogs

Phenotypic variation is a prerequisite for evolution by natural selection, yet the processes that give rise to the novel morphologies upon which selection acts are poorly understood. We employed a chemical genetic screen to identify developmental changes capable of generating morphological variation as observed among extant species. Specifically, we assayed for small molecules capable of transforming the ancestral larval foregut of the herbivorous Xenopus laevis to resemble the derived foregut of the carnivorous Lepidobatrachus laevis. Appropriately, the small molecules that demonstrate this capacity modulate morphogenetic pathways involved in gut development, including retinoic acid (RA) signaling. Identical manipulations in a species more closely related to Lepidobatrachus, Ceratophrys cranwelli, yielded even more similar transformations, corroborating the relevance of RA signaling variation in interspecific morphological change. Finally, we were able to recover the ancestral gut phenotype in Lepidobatrachus by performing a reverse chemical manipulation to upregulate RA signaling, providing strong evidence that modifications to this specific pathway promoted the emergence of a lineage‐specific phenotypic novelty. Small molecule screening may be valuable for identifying developmental mechanisms that underlie ecologically and evolutionarily relevant phenotypic variation.

Effects of prey type on specific dynamic action, growth, and mass conversion efficiencies in the horned frog, Ceratophrys cranwelli

To be most energetically profitable, predators should ingest prey with the maximal nutritional benefit while minimizing the cost of processing. Therefore, when determining the quality of prey items, both the cost of processing and nutritional content must be considered. Specific dynamic action (SDA), the increase in metabolic rate associated with feeding in animals, is a significant processing cost that represents the total cost of digestion and assimilation of nutrients from prey. We examined the effects of an invertebrate diet (earthworms) and a vertebrate diet (newborn mice) on mass conversion efficiencies, growth, and SDA in the Chacoan horned frog, Ceratophrys cranwelli. We found the earthworm diet to be significantly lower in lipid, protein, and energy content when compared to the diet of newborn mice. Growth and mass conversion efficiencies were significantly higher in frogs fed newborn mice. However, mean SDA did not differ between frogs fed the two diets, a finding that contradicts many studies that indicate SDA increases with the protein content of the meal. Together, our results indicate that future studies evaluating the effect of meal type on bioenergetics of herpetofauna are warranted and may provide significant insight into the underlying factors driving SDA.

Specific Dynamic Effect in the Horned Frog Ceratophrys cranwelli

Animals exhibit an increase in resting metabolic rate after feeding while they process the ingested food, a response that has been termed the specific dynamic effect. This postprandial rise in metabolism is due in part to the cost of processing absorbed nutrients, especially amino acids, and is particularly pronounced in animals such as large snakes that consume large prey on an infrequent basis. To increase our understanding of the specific dynamic effect in amphibians, we measured the metabolic rates of horned frogs, Ceratophrys cranwelli, before and after they consumed mice or an amino acid solution. After the frogs consumed mice at 20, 25, and 30 C, their oxygen consumption increased within 48 h to a peak that was twoto fivefold greater than the fasting level. The total energy expended depended on the mass of the mice consumed and was not significantly related to variation in frog mass or temperature. Of the energy ingested, 9-15% was expended during the processing of the food. These frogs were as efficient in processing a meal as other vertebrates. After the frogs consumed an amino acid solution, their excess postprandial energy expenditure was less than 25% of the value when they consumed mice of the equivalent amino acid composition. The cost of processing absorbed amino acids cannot be responsible for the majority of the specific dynamic effect in these frogs.

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 leptodactylid frog, Ceratophrys cornuta (Ceratophryinae), are described in detail, including the ontogenetic development of the chondrocranium 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.

Chromosome banding in Amphibia. IX. The polyploid karyotypes of Odontophrynus americanus and Ceratophrys ornata (Anura, Leptodactylidae).

The somatic and meiotic chromosomes of the South American leptodactylid toads Odontophrynus americanus, Ceratophyrys ornata, and C. cranwelli were analysed both with conventional staining and differential banding techniques. The karyotypes of O. americanus were tetraploid; those of C. ornata octaploid. Ceratophrys cranwelli is a diploid species whose karyotype displays great similarities with that of C. ornata. The high frequency of multivalent pairing configurations in the meioses of O. americanus and C. ornata indicate that these animals were of autopolyploid origin. The conventionally stained somatic chromosomes of O. americanus can be arranged into sets of four similar chromosomes (quartets); those of C. ornata, into sets of eight similar chromosomes (octets). The banding patterns revealed heterogeneity within some quartets of O. americanus, dividing each of them into two pairs of homologous chromosomes. In analogy, some octets of C. ornata can be subdivided into two quartets of chromosomes with homologous bands. These structural heterogeneities within the quartets and octets are interpreted as a "diploidization" of the polyploid karyotypes. Diploidization leads to genomes that are polyploid with respect to the amount of genetic material and diploid with respect to chromosomal characteristics and the level of gene expression. In tetraploid O. americanus, the number of nucleolus organizer regions (NORs) and their DNA content is proportional to the degree of ploidy. In contrast, up to eight NORs have been deleted in the octoploid C. ornata. These NOR losses are discussed as a possible reason for the reduction of genetic activity in polyploid genomes.

Chromosome pairing in female and male diploid and polyploid anurans (Amphibia) from South America.

Chromosome pairing in females and males of diploid (2n = 22) and tetraploid (2n = 44) Odontophrynus americanus and diploid Ceratophrys cranwelli (2n = 26) and tetraploid C. ornata (2n = 104) showed that diploid females formed more chiasmata per paired arm than diploid males and polyploids of both sexes. There was a reduction in the level of recombination in female polyploids by forming multivalents with terminal chiasmata. The reduction reflected a change in the genetic control of pairing in females after polyploidization.