Ceratophrys Ornata Research Articles

Habitat loss and distribution of the Ornate Horned Frog (Ceratophrys ornata): implications for its conservation in South American temperate grasslands

Ceratophrys ornata is an iconic and regionally threatened amphibian of the temperate grasslands from Argentina, Brazil, and Uruguay. Conservation assessments suggested that habitat loss is the main threat to the species, although no studies have yet explored the link between grassland replacement and C. ornata decline. Using a robust database with ∼1000 records from herpetological collections, citizen science, and long-term monitoring, we modeled the species' ecological niche to produce a map of suitable areas, where we searched for C. ornata using active and passive techniques. After exhaustive efforts, we failed to obtain recent records from Brazil and Uruguay. We also conducted Generalized Linear Models to explore the relationship between land use/cover, landscape configuration, and current species occurrence. Overall, results showed that C. ornata occurrence is negatively associated with variables related to native grasslands fragmentation and replacement (i.e., Distance to the Nearest Patch, Forest Plantations), suggesting that habitat loss may have driven local extinctions and population declines of the species. Finally, we outline the regional and national conservation needs of C. ornata and recommend focusing on in-situ conservation strategies for the Argentinean populations to ensure the species' viability.

Cutaneous Iridophoroma in an Argentine Horned Frog (Ceratophrys ornata)

A 14-yr-old Argentine horned frog (Ceratophrys ornata) presented for evaluation of a chronic, cutaneous mass. A white, semifirm raised mass was present in the skin on the right cranial dorsum. Excisional biopsy was performed. Fine-needle aspiration cytology and histopathology were consistent with an iridophoroma, a type of chromatophoroma. Recurrence occurred and removal was repeated 4 months and again 2 yr following the initial surgery. The original mass did not have definitive criteria of malignancy but did extend to surgical margins, which may account for repeated local recurrence. Although chromatophoromas are relatively common cutaneous neoplasms in reptiles and amphibians, iridophoromas are rarely reported in amphibians. This is the first report of an iridophoroma in an Argentine horned frog.

Vascular Tumors in Two Argentine Horned Frogs (Ceratophrys ornata)

Two vascular tumors in two Argentine horned frogs (Ceratophrys ornata) are described. Case 1 involved a 7-year-1-month-old Argentine horned frog that had a splenic mass with a sanguineous coelomic effusion. Histologically, the splenic parenchyma was effaced by a poorly-demarcated, invasive mass, consisting of spindle cells with marked nuclear atypia forming irregular blood vessel channels containing blood. Case 2 involved a pedunculated facial mass located at the upper right lip of an over-8-month-old Argentine horned frog. Histologically, the well-demarcated, poorly cellular mass consisted of sparse proliferation of spindle cells forming irregular slits with prominent edema. Immunohistochemically, the neoplastic cells of both cases were positive for anti-CD31 antibody. The diagnoses were hemangiosarcoma in case 1 and lymphangioma in case 2. To the best of the authors’ knowledge, this is the first description of neoplastic diseases in captive Argentine horned frogs.

Brain Reconstruction Across the Fish-Tetrapod Transition; Insights From Modern Amphibians

The fish-tetrapod transition (which incorporates the related fin-limb and water-land transitions) is celebrated as one of the most important junctions in vertebrate evolution. Sarcopterygian fishes (the “lobe-fins”) are today represented by lungfishes and coelacanths, but during the Paleozoic they were much more diverse. It was some of these sarcopterygians, a lineage of the tetrapodomorph fishes, that gave rise to tetrapods (terrestrial vertebrates with limbs bearing digits). This spectacular leap took place during the Devonian Period. Due to the nature of preservation, it is the hard parts of an animal’s body that are most likely to fossilize, while soft tissues such as muscular and brain tissues, typically fail to do so. Thus, our understanding of the adaptations of the hard skeletal structures of vertebrates is considerably greater than that of the soft tissue systems. Fortunately, the braincases of early vertebrates are often ossified and thereby have the potential to provide detailed morphological information. However, the correspondence between brain and endocast (an internal mold of the cavity) has historically been considered poor in most “lower” vertebrates and consequently neglected in such studies of brain evolution. Despite this, recent work documenting the spatial relationship in extant basal sarcopterygians (coelacanth, lungfish, axolotl, and salamander) has highlighted that this is not uniformly the case. Herein, we quantify and illustrate the brain-endocast relationship in four additional extant basal tetrapod exemplars: neobatrachian anurans (frogs) Breviceps poweri and Ceratophrys ornata; and gymnophionans (caecilians) Gegeneophis ramaswamii and Rhinatrema bivittatum. We show that anurans and caecilians appear to have brains that fill their endocasts to a similar degree to that of lungfishes and salamanders, but not coelacanth. Ceratophrys has considerably lower correspondence between the brain and endocast in the olfactory tract and mesencephalic regions, while Breviceps has low correspondence along its ventral endocranial margin. The brains of caecilians reflect their endocasts most closely (vol. ∼70%). The telencephalon is tightly fitted within the endocast in all four taxa. Our findings highlight the need to adequately assess the brain-endocast relationship in a broad range of vertebrates, in order to inform neural reconstructions of fossil taxa using the Extant Phylogenetic Bracket approach and future studies of brain evolution.

Human attitudes as threats in amphibians: the case of the Ornate Horned Frog (Ceratophrys ornata)

ABSTRACT We analyzed the characteristics of the human-animal conflict coming from the attitudes that local communities have toward Ceratophrys ornata, focusing on two threats: aversion and pet trade. Surveys conducted in Argentina, Brazil and Uruguay (n = 194) showed a strong aversion to this species (45% of respondents), causing the death of at least 364 individuals. This aversion was strongly linked to symbolism and folklore beliefs, and also influenced by gender and education level. Pet trade interviews (n = 30) showed that 77% of the specimens kept in captivity were wild-caught (≈178 individuals). The killing of specimens based on aversion might have impacts at local level, especially in populations occurring in recent urbanized areas. Our results also revealed that capture of specimens for pet trade is an ongoing process. Due to the context of illegality in which trade occurs, it is highly challenging to determine/predict the extent of impacts.

A Last Glacial anuran assemblage from the inland Pampas of South America provides insights into climate and environments during marine isotope stage 3

ABSTRACTEnvironmental and climatic conditions of the South American temperate grasslands (Pampas) during the Last Glacial Period have typically been regarded as mostly arid and cold, whereas humid and mild conditions such as those prevailing today may have been established only recently. This hypothesis has been built mostly upon fossil mammals that come from coastal areas and date from the end phase of this period and thus provide both temporally and geographically biased data. Other fossil vertebrates, including anurans, have been overlooked when addressing these conditions in spite of being potentially very informative due to their ecological requirements. Here, we analyze an anuran assemblage from the Last Glacial Period of the inland Pampas. In addition to the description of new records, we discuss the taphonomic settings and the correlation of the fossil-bearing beds with levels referred to the interstadial Marine Isotope Stage (MIS) 3 from other Pampean localities. Based on this evidence, together with what is known for extant anurans, we discuss the environmental and climatic conditions of the Pampas during the Last Glacial Period. The presence of Rhinella arenarum and, particularly, Ceratophrys ornata in the fossil assemblage and their persistence in the Pampas throughout the Quaternary suggest that the range of environmental changes in the region during the Last Glacial Period might have been more limited than has traditionally been acknowledged. In this regard, this study highlights the value of anuran fossil assemblages when addressing environmental and climatic conditions during the Quaternary.

Tadpoles of the horned frog Ceratophrys ornata exhibit high sensitivity to chlorpyrifos for conventional ecotoxicological and novel bioacoustic variables.

Previous studies reported that some species of the family Ceratophryidae are able to produce sounds during premetamorphic tadpole stages. We have now determined the effects of the cholinesterase-inhibiting insecticide chlorpyrifos (CPF) on sounds emitted by tadpoles of Ceratophrys ornata. Tadpoles were exposed individually in order to evaluate the progression of effects. Effects on sound production were complemented with common ecotoxicological endpoints (mortality, behavior, abnormalities and growth inhibition). C.ornata was found to be more sensitive than other native (= 67%, 50%) and non-native species (= 75%, 100%) considering lethal and sublethal endpoints, respectively. Effects on sounds appear along with alterations in swimming, followed by the presence of mild, then severe abnormalities and finally death. Therefore, sound production may be a good biomarker since it anticipates other endpoints that are also affected by CPF. Ceratophrys ornata is a promising new model species in ecotoxicology.

Las colecciones biológicas: Los tesoros escondidos de un país mega-diverso

The gastrula morphology of Ceratophrys stolzmanni (the Pac-man frog) was studied. Its eggs, whose diameter at the beginning of the gastrulation process is 2.2 mm in diameter, develop rapidly. The gastrulation process requires five hours approximately. The embryos were fixed and analyzed in whole-mount, in bisections, and vibratome sections. The eggs of C. stolzmanni were pigmented, as in Xenopus laevis, but their size was bigger. The gastrula morphology of C. stolzmanni is similar to the one described for Ceratophrys ornata (the argentine horned-frog) by other authors. The late gastrula and early neurula stages, studied with vibratome sections stained for cell nuclei, revealed lack of endoderm covering both the posterior notochord and the somites found on this region. This region is called the GRP (Gastrocoel roof plate) and it plays a major role in the development of the left-right axis in amphibians. In this work the GRP of C. stolzmanni was characterized at the morphological level.

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...

Old and new hypotheses about the homology of the compound bones from the cheek and otico-occipital regions of the anuran skull

We studied the larval development of compound bones from the otico-occipital and cheek regions in species of the neobatrachian genera Batrachyla, Hylorina, Leptodactylus, Odontophrynus and Pleurodema. Comparisons were made using a set of Ambystoma spp. (Caudata) and Ceratophrys ornata (Anura; Ceratophryidae) larvae. As suggested by previous studies, we verified the compound nature of the exoccipital (two centers, anurans only), frontoparietal (one center, most anurans and Ambystoma; three centers, some anurans), and squamosal (two centers, all anurans and Ambystoma) bones. We discuss old and new homology hypotheses for each of the compound bone centers in the context of the most widely accepted scenario of lissamphibian origins and relationships, i.e., monophyletic Lissamphibia that includes the clade Batrachia (Caudata+Anura) and the most divergent Gymnophiona. Our findings have a direct impact on our understanding of the composition of the skull in Lissamphibia. We recognized the presence of the following bones: (i) opisthotic (fused to the exoccipital) and tabular (fused to the squamosal) in Batrachia (Anura+Caudata) and (ii) supratemporal (fused to the parietal portion of the frontoparietal) in Anura. Separate centers of the parietal were found only in Pleurodema.

Morfohistología testicular de Ceratophrys ornata (Bell) (Amphibia, Anura, Ceratophryidae)

En el presente trabajo se describen las características morfohistológicas del testículo de individuos adultos (n=5) de Ceratophrys ornata (Bell, 1843) provenientes de humedales del centro de Argentina. Los mismos se procesaron mediante técnicas histológicas de rutina, se cortaron a 8 µm y las láminas obtenidas se tiñeron con hematoxilina-eosina y tricrómico de Masson. Las gónadas son órganos pares, amarillentos, alargados y contorneados de 18,58 ± 0,23 mm de largo por 1,51 ± 0,13 mm de ancho. Histológicamente se observa una delgada túnica albugínea (6,29 ± 0,83 µm) rodeando a los testículos. En su interior se hallan lóculos seminíferos que miden 240,64 ± 38,52 µm de diámetro, en ellos se distinguen cistos con células espermatogénicas en distintas etapas de desarrollo. El tejido intersticial es escaso y en él se destacan las células de Leydig y vasos sanguíneos. Las espermatogonias I son las células más grandes de la serie germinal (20,03 ± 2,27 µm); poseen la cromatina granular y de aspecto multilobular, hallándose comúnmente una por cisto, estas originan a las espermatogonias II, más pequeñas (12,06 ± 1,14 µm). Los espermatocitos I presentan la cromatina levemente condensada y son un poco más chicos que sus precedentes (11,64 ± 0,36 µm). Los espermatocitos II miden 8,85 ± 0,54 µm. Las espermátidas I son esféricas, miden 5,95 ± 0,42 µm y se agrupan en cistos redondeados. Las espermátidas II, en cambio son alargadas y no se hallan dentro de cistos, pero siguen organizadas en paquetes asociadas a células de Sertoli. Los espermatozoides son células libres hacia el centro del lóculo, alargadas, flageladas y con una notable compactación nuclear. La morfohistología de los testículos analizados muestran características macroscópicas e histológicas similares a las observadas en otras especies de anfibios anuros neotropicales, presentando todas las células del linaje espermatogénico en un mismo lóculo, lo que indicaría que presentan ciclos espermatogénicos continuos.

Metabolic responses of the South American ornate horned frog (Ceratophrys ornata) to estivation

We examined the metabolic responses of the South American frog, Ceratophrys ornata, to laboratory-induced estivation. Whole-animal and mass-specific oxygen consumption rates (VO(2)) did not change during fasting or 56days of estivation, despite observing significant decreases in body mass. The maintenance of mass-specific metabolic rate at routine levels during estivation suggests that metabolic rate suppression is not a major response to estivation in this species. There was a significant decline in liver glycogen and a loss of adipose tissue mass during estivation, suggesting that both carbohydrate and lipid pathways are used to fuel metabolism during estivation. The activity of pyruvate dehydrogenase, an important regulator of carbohydrate oxidation, and carnitine palmitoyltransferase and 3-hydroxyacyl-CoA dehydrogenase, regulators of lipid oxidation, showed no significant change in activity in liver, heart, and muscle between estivating and active frogs. There was an increase in plasma osmolality, which is characteristic of estivating animals. Overall, our metabolic analysis of estivation in C. ornata indicates that this species does not employ a dramatic suppression metabolic rate to survive dehydration stress and that both endogenous carbohydrates and lipids are used as metabolic fuels.

Acoustic underwater signals with a probable function during competitive feeding in a tadpole

Acoustic communication is widespread among adult stages of terrestrial animals and fish and has also been observed in insect larvae. We report underwater acoustic communication in the larvae of a frog, Gephyromantis azzurrae, from Isalo, a sandstone massif in western Madagascar. According to our field data, these tadpoles live in streams and prefer habitats characterized by comparatively low temperatures, shallow water depth, and a relatively fast current. Feeding experiments indicated that the tadpoles are carnivorous and macrophagous. They consumed insect larvae and, to a lesser extent, small shrimps, and conspecific as well as heterospecific tadpoles. Calls of these tadpoles consisted either of single click notes or of irregular series of various clicks. Some complex calls have a pulsed structure with three to nine indistinct energy pulses. Production of the pulses coincided with rapid closure of the jaw sheaths and often with an upward movement of the body. Calls were emitted while attacking prey and occurred significantly more often when attacking conspecifics. Tadpoles that had not been fed for some time emitted sounds more frequently than those that had been regularly fed. The spectral frequency of the calls differed in tadpole groups of different size and was higher in groups of smaller tadpoles, suggesting that spectral frequency carries some information about tadpole size which might be important during competitive feeding to assess size and strength of competitors. This report differs from those for the larvae of South American horned frogs, Ceratophrys ornata. These are the only other tadpoles for which sound production has reliably been reported but the calls of Ceratophrys tadpoles occur mainly in a defensive context.

Serous cutaneous glands in the South American horned frog Ceratophrys ornata (Leptodactylformes, Chthonobatrachia, Ceratophrydae): Ultrastructural expression of poison biosynthesis and maturation

Serous cutaneous glands are described in newly metamorphosed and juvenile specimens of the horned frog Ceratophrys ornata using light and transmission electron microscopy. We report patterns of biosynthesis and maturation of the specific product of the gland secretory unit. The syncytial, secretory compartment possesses a complex of endoplasmic reticulum (predominantly smooth endoplasmic reticulum after metamorphosis) and Golgi stacks. The serous product is weak in density and is contained in vesicles involved in repeating merging processes. During this maturation activity, secondary lysosomes are observed, which derive from autophagic processes (crinophagy) involving the secretory materials. Ceratophrys ornata, a species representative of the type genus of the family Ceratophrydae, belongs to the heterogeneous group of anurans that, possibly as the result of convergence, all produce cutaneous poisons consisting of vesicles or faint density granules.

Effects of meal size, meal type, and body temperature on the specific dynamic action of anurans

Specific dynamic action (SDA), the increase in metabolism stemming from meal digestion and assimilation, varies as a function of meal size, meal type, and body temperature. To test predictions of these three determinants of SDA, we quantified and compared the SDA responses of nine species of anurans, Bombina orientalis, Bufo cognatus, Ceratophrys ornata, Dyscophus antongilli, Hyla cinerea, Kassina maculata, Kassina senegalensis, Pyxicephalus adspersus, and Rana catesbeiana subjected to meal size, meal type, and body temperature treatments. Over a three to seven-fold increase in meal size, anurans experienced predicted increases in postprandial rates of oxygen consumption (VO(2)) the duration of elevated VO(2) and SDA. Meal type had a significant influence on the SDA response, as the digestion and assimilation of hard-bodied, chitinous crickets, mealworms, and superworms required 76% more energy than the digestion and assimilation of soft-bodied earthworms, waxworms, and neonate rodents. Body temperature largely effected the shape of the postprandial metabolic profile; peak VO(2) increased and the duration of the response decreased with an increase in body temperature. Variation in body temperature did not significantly alter SDA for four species, whereas both H. cinerea and R. catesbeiana experienced significant increases in SDA with body temperature. For 13 or 15 species of anurans ranging in mass from 2.4 to 270 g, SMR, postprandial peak VO(2) and SDA scaled with body mass (log-log) with mass exponents of 0.79, 0.93, and 1.05, respectively.

Physiological responses to feeding, fasting and estivation for anurans

Anuran estivation is characterized by long episodes of aphagia. To investigate whether estivating anurans downregulate intestinal performance as an adaptive mechanism to reduce energy expenditure, I compared the metabolic and intestinal responses to feeding, fasting and estivation among non-estivating and estivating species of the anuran families Bufonidae, Leptodactylidae and Ranidae. Standard metabolic rates of the estivating Bufo alvarius, Ceratophrys ornata and Pyxicephalus adspersus were significantly less than those of the non-estivating Bufo marinus, Leptodactylus pentadactylus and Rana catesbeiana. Whereas the digestion of rodent meals equaling 15% of anuran body mass generated significant metabolic responses for all species, specific dynamic action was significantly greater for the estivating species. For estivating species, feeding triggered more than a doubling of small intestinal mass and significant upregulation of intestinal nutrient transport rates, resulting in six- to tenfold increases in total intestinal nutrient uptake capacity. The postprandial intestinal responses of the non-estivating species were much more modest, averaging a 50% increase in small intestinal mass and 69% increase in uptake capacities. Following 1 month of laboratory-induced estivation, C. ornata and P. adspersus had further depressed metabolic rates by 20%, intestinal masses by 44%, and total intestinal uptake capacities by 60%. In a fashion similar to infrequently feeding, sit-and-wait foraging snakes, estivating anurans possess the capacity to severely downregulate intestinal performance with fasting and estivation, and subsequently upregulate the gut with feeding. The depression in gut performance during estivation aids in reducing energy expenditure, thereby increasing the duration that the animal can remain dormant while relying solely upon stored energy.

Histology and lectin‐binding patterns in the digestive tract of the carnivorous larvae of the Anuran, Ceratophrys ornata

Larvae of Ceratophrys ornata are carnivorous, have relatively short digestive tracts and continue to feed during metamorphic climax, in contrast to those of more typical herbivorous anuran larvae. The present study describes both histological and histochemical changes in the stomach, small intestine, and large intestine of C. ornata prior to and during metamorphic climax. Modifications in these organs were found to be similar to but less dramatic than those in herbivorous larvae. Luminal epithelial cells in the three regions develop vacuoles, suggesting degeneration, but sloughing of this epithelium, as occurs in herbivorous larvae, was not observed in C. ornata. Multicellular tubular glands develop gradually in the gastric area during the larval stages, gastric pits appear during metamorphic climax, and mucous neck cells are first visible in the juvenile. Goblet cells in the small and large intestine increase in number during larval life, as do the number of folds in the intestinal wall. Increase in diameter and thickness of the wall occurs in the stomach as well as in the small and large intestine. Such changes result in an adult-type digestive tract characteristic of frogs in general. Staining with two horseradish peroxidase conjugated lectins, soybean agglutinin (SBA) and Ulex europaeus agglutinin I (UEA I), demonstrated specific sites along the digestive tract of glycoconjugates with terminal sugars N-acetylgalactosamine and α-fucose, respectively. As metamorphic climax approaches, staining intensities decrease—thus providing evidence for metamorphic changes in the sugar moieties of glycoconjugates present in the digestive tract of carnivorous larvae. J. Morphol. 241:19–32, 1999. © 1999 Wiley-Liss, Inc.

Insulin and Proglucagon-Derived Peptides from the Horned Frog, Ceratophrys ornata (Anura:Leptodactylidae)

Insulin and peptides derived from the processing of proglucagon have been isolated from an extract of the pancreas of the South American horned frog, Ceratophrys ornata (Leptodactylidae). Ceratophrys insulin is identical to the insulin previously isolated from the toad, Bufo marinus (Bufonidae). Ceratophrys glucagon was isolated in two molecular forms with 29- and 36-amino acid residues in approximately equal amounts. Glucagon-29 is identical to glucagon from B. marinus and from the bullfrog, Rana catesbeiana (Ranidae) and contains only 1 amino acid substitution (Thr29→Ser) compared with glucagon from Xenopus laevis (Pipidae). Glucagon-36 comprises glucagon-29 extended from its C-terminus by Lys-Arg-Ser-Gly-Gly-Met-Ser. This extension is structurally dissimilar to the C-terminal octapeptide of mammalian oxyntomodulin and resembles more closely that found in C-terminally extended glucagons isolated from fish pancreata. Ceratophrys glucagon-like peptide-1 (GLP-1) (His-Ala-Asp-Gly-Thr-Tyr-Gln-Asn-Asp-Val10-Gln-Gln-Phe-Leu-Glu- Glu-Lys-Ala-Ala-Lys20-Glu-Phe-Ile-Asp-Trp-Leu-Ile-Lys-Gly- Lys30-Pro-Lys-Lys-Gln-Arg-Leu-Ser) contains 3 amino acid substitutions compared with the corresponding peptide from B. marinus, 8 substitutions compared with GLP-1 from R. catesbeiana, and between 4 and 11 substitutions compared with the three GLP-1 peptides identified in X. laevis proglucagon. GLP-2 was not identified in the extract of Ceratophrys pancreas. The data indicate that, despite its importance in the regulation of glucose metabolism, the primary structure of GLP-1 has been very poorly conserved during evolution, even among a single order such as the Anura.

Histology and lectin-binding patterns in the digestive tract of the carnivorous larvae of the anuran, Ceratophrys ornata.

Larvae of Ceratophrys ornata are carnivorous, have relatively short digestive tracts and continue to feed during metamorphic climax, in contrast to those of more typical herbivorous anuran larvae. The present study describes both histological and histochemical changes in the stomach, small intestine, and large intestine of C. ornata prior to and during metamorphic climax. Modifications in these organs were found to be similar to but less dramatic than those in herbivorous larvae. Luminal epithelial cells in the three regions develop vacuoles, suggesting degeneration, but sloughing of this epithelium, as occurs in herbivorous larvae, was not observed in C. ornata. Multicellular tubular glands develop gradually in the gastric area during the larval stages, gastric pits appear during metamorphic climax, and mucous neck cells are first visible in the juvenile. Goblet cells in the small and large intestine increase in number during larval life, as do the number of folds in the intestinal wall. Increase in diameter and thickness of the wall occurs in the stomach as well as in the small and large intestine. Such changes result in an adult-type digestive tract characteristic of frogs in general. Staining with two horseradish peroxidase conjugated lectins, soybean agglutinin (SBA) and Ulex europaeus agglutinin I (UEA I), demonstrated specific sites along the digestive tract of glycoconjugates with terminal sugars N-acetylgalactosamine and alpha-fucose, respectively. As metamorphic climax approaches, staining intensities decrease--thus providing evidence for metamorphic changes in the sugar moieties of glycoconjugates present in the digestive tract of carnivorous larvae.

Growth and death of rohon-Beard cells in Rana pipiens and Ceratophrys ornata.

Rohon-Beard (R-B) neurons of the medulla oblongata and spinal cord of anurans originate during gastrulation, become distinguishable just after closure of the neural tube, and are present in maximum numbers at the end of the embryonic period, just before feeding begins. Cell deaths are first seen in the earliest larval stages; in Rana pipiens and Ceratophrys ornata, they may not be complete until the very end of larval development or a day or two later, in the juvenile froglet. This is in sharp contrast with Xenopus laevis, in which the last R-B cells die well before the onset of metamorphic climax. Cell losses tend to reach completion in the trunk in a craniocaudal progression, that is, first in the medulla oblongata, then sequentially at brachial, postbrachial, and lumbar levels. Nuclei and cells increase in size through embryonic and early larval stages, reaching maxima at stages X-XIV (of 25 larval stages), then shrinking before cell death occurs. While Ceratophrys produces only two-thirds as many R-B cells as does R. pipiens, its rate of cell death is slower, gauged by attained stage, and at every stage, X-XXIV, Ceratophrys displays a greater number of surviving cells. In hypophysectomized Rana pipiens larvae some 7-15% of the peak numbers of R-B cells are still present after 400 days, more than 4 times the length of the usual larval period. Most or all of these surviving cells are in the tail. The extreme persistence of R-B cells in hypophysectomized larvae is consistent with the view that the R-B cell population can be characterized as being divided into those cells whose death occurs relatively early and those in which cell destruction occurs late, presumably dependent upon different factors. The critical factor for onset of cell death in late larvae may well be the surge in thyroid hormone concentration, which characterizes metamorphic climax.