Different Stages Of Metamorphosis Research Articles

Ontogenetic characteristics of the intestinal microbiota of Quasipaa spinosa revealed by 16S rRNA gene sequencing.

To analyse the correlation between the intestinal microbiota (IM) and differential development of Quasipaa spinosa across different stages of metamorphosis, we focused on four key developmental periods (15 days post-hatch [dph; Gosner stage, GS23], 60 dph [GS25], 90 dph [GS41] and 150 dph [GS25, GS41, GS42, GS46]) and used 16S rDNA amplicon sequencing. Results showed that IM diversity in Q. spinosa was related to life history. Specifically, there was a significant difference between the aquatic and terrestrial stages, and IM diversity increased with age. Proteobacteria, Bacteroidetes and Firmicutes were the dominant phyla in tadpoles, whereas Bacteroidetes, Proteobacteria, Firmicutes and Fusobacteria were the dominant phyla at the metamorphosis stages. The composition of the IM at different stages and ages varied considerably, but the changes were not substantial among different development stages at 150 dph. This was probably because age has a greater influence than growth factors, and host selective pressure increases with age. This study provides a theoretical reference for subsequent studies on the IM, as well as for the prevention of amphibian endogenous pathogenic microbial diseases.

Accumulation of microplastics in tadpoles from different functional zones in Hangzhou Great Bay Area, China: Relation to growth stage and feeding habits

Microplastics (MPs) are ubiquitous in freshwater ecosystems, including inland small waterbodies (e.g., ponds and ditches), which are unique habitats for tadpoles. The uptake of MPs by tadpoles is influenced by their habitat, life stage, and feeding strategy. In this study, we investigated MP levels in small waterbodies in three different functional zones from the Hangzhou Great Bay Area, China, and resident tadpoles at different stages of metamorphosis with different feeding habits. Our results indicated that MPs in all three sampling areas were predominantly fibers; and the highest abundances of MPs were observed in water (4.70 ± 2.30 items/L) and sediment (728 ± 324 items/kg) from a textile industrial area, likely the result of nearby human activities. There was no significant difference in MP number in tadpoles between areas; however, omnivorous tadpoles with labial teeth and horny beaks ingested more MPs than did filter feeders. Based on their developmental characteristics, the collected tadpoles were categorized as: pre-metamorphosis, pro-metamorphosis, and metamorphic climax. The MP levels exhibited an upward trend, and MP size gradually increased as tadpole development progressed. This suggests that MPs may accumulate in tadpoles as they grow and potentially affect their metamorphosis from larvae to frogs.

Feeding habits of the Cichlid Chromidotilapia guntheri (Sauvage, 1882) in some hydrosystems of Ivory Coast

The feeding habit of Chromidotilapia guntheri was investigated in seven hydrosystems of Ivory Coast. The contents of 156 non-empty stomachs were examined from specimens caught in the rivers Soumié, Eholié, Noé, Ehania and Banco, the Bea rill and the Kpoda lake. Diets composition, feeding strategy and trophic niche width were analyzed among hydrosystems. Stomach content analysis indicated that C. guntheri feeds preferentially on plants and insects debris and secondarily, it consumed insects’ larvae, nymphs and adults in all habitats. This species would be an omnivorous with a detritivorous tendency. As feeding strategy, it practices a generalist strategy even if some individuals displayed specialization intentions on insects at different stages of metamorphosis. Investigations on ontogenetic shift revealed that juveniles and adults of C. guntheri consume substantially the same types of prey with varying amounts depending on the size of the fish. However there is a significant decrease in the proportions of gastropods and oligochaetes ingested when growing.

Metamorphosis Affects Metal Concentrations and Isotopic Signatures in a Mayfly (Baetis tricaudatus): Implications for the Aquatic-Terrestrial Transfer of Metals

Insect metamorphosis often results in substantial chemical changes that can alter contaminant concentrations and fractionate isotopes. We exposed larval mayflies (Baetis tricaudatus) and their food (periphyton) to an aqueous zinc gradient (3-340 μg Zn/l) and measured zinc concentrations at different stages of metamorphosis: larval, subimago, and imago. We also measured changes in stable isotopes (δ15N and δ13C) in unexposed mayflies. Larval zinc concentrations were positively related to aqueous zinc, increasing 9-fold across the exposure gradient. Adult zinc concentrations were also positively related to aqueous zinc, but were 7-fold lower than larvae. This relationship varied according to adult substage and sex. Tissue concentrations in female imagoes were not related to exposure concentrations, but the converse was true for all other stage-by-sex combinations. Metamorphosis also increased δ15N by ∼0.8‰, but not δ13C. Thus, the main effects of metamorphosis on insect chemistry were large declines in zinc concentrations coupled with increased δ15N signatures. For zinc, this change was largely consistent across the aqueous exposure gradient. However, differences among sexes and stages suggest that caution is warranted when using nitrogen isotopes or metal concentrations measured in one insect stage (e.g., larvae) to assess risk to wildlife that feed on subsequent life stages (e.g., adults).

Reactive oxygen species and anti-oxidant defenses in tail of tadpoles, Xenopus laevis

Tail regression in tadpoles is one of the most spectacular events in anuran metamorphosis. Reactive oxygen species and oxidative stress play an important role during this process. Presently, the cell- and tissue-specific localization of antioxidant enzymes such as superoxide dismutase (SOD) and catalase as well as neuronal and inducible nitric oxide synthase isoforms (nNOS and iNOS) responsible for production of nitric oxide (NO) were carried out during different stages of metamorphosis in tail of tadpole Xenopus laevis. NO also has profound effect on the mitochondrial function having its own nitric oxide NOS enzyme. Hence, in situ staining for NO and mitochondria also was investigated. The distribution of nNOS and iNOS was found to be stage specific, and the gene expression of nNOS was up-regulated by thyroxin treatment. In situ staining for NO and mitochondria shows co-localization, suggesting mitochondria being one of the sources of NO. SOD and catalase showed significant co-localization during earlier stages of metamorphosis, but before the tail regression begins, there was a significant decrease in activity as well as co-localization suggesting increased ROS accumulation. These findings are discussed in terms of putative functional importance of ROS and cytoplasmic as well as mitochondrial derived NO in programmed cell death in tail tissue.

Neural system reorganization during metamorphosis in the planula larva of Clava multicornis (Hydrozoa, Cnidaria)

The planula larva of the hydroid Clava multicornis (Forskal, 1775) has a complex nervous system, characterized by the presence of distinct, anteriorly concentrated peptidergic populations of amidated neurons, presumably involved in the detection of environmental stimuli and metamorphic signals. Differently from other hydrozoan larvae in C. multicornis planulae GLW-positive cells with putative sensory role have a peculiar dome-shaped forefront organization, followed by a belt of RF-positive nerve cells. By immunohistochemistry, we investigated the transformation of the peptidergic (GLW-amide and RF-amide) larval neuroanatomy at different stages of metamorphosis and the subsequent development of the primary polyp nervous system. By terminal transferase-mediated dUTP nick end-labeling assay, apoptotic nuclei were first identified in the anterior pole of the settled larva, in the same region occupied by GLW-amide positive putative sensory cells. In primary polyps, GLW-amide positive signals first encircled the hypostome area, later extending downwards along the polyp column or upwards over the hypostome dome, whereas RF-amide positive sensory cells initially appeared at the tentacles base to later extend in the tentacles and the polyp column. In spite of the possession of distinct neuroanatomies, different cnidarian planulae may share common developmental mechanisms underlying metamorphosis, including apoptosis and de novo differentiation. Our data confirm the hypothesis that the developmental dynamics of tissue rearrangements may be not uniform across different taxa.

Energetics of metamorphosis in Drosophila melanogaster

We measured the energetic cost of metamorphosis in the fruitfly, Drosophila melanogaster. Metabolic rates decreased rapidly in the first 24 h and remained low until shortly before eclosion, when the rates increased rapidly, thus creating a U-shaped metabolic curve. The primary fuel used during metamorphosis was lipid, which accounted for >80% of total metabolism. The total energy consumed during metamorphosis was lowest at 25 °C, compared to 18 and 29 °C, due to differences in metabolic rates and the length of pupal development. Temperature differentially affected metabolic rates during different stages of metamorphosis. Prepupal and late pupal stages exhibited typical increases in metabolic rate at high temperatures, whereas metabolic rates were independent of temperature during the first 2/3 of pupal development. We tested two hypotheses for the underlying cause of the U-shaped metabolic curve. The first hypothesis was that pupae become oxygen restricted as a result of remodeling of the larval tracheal system. We tested this hypothesis by exposing pupae to hypoxic and hyperoxic atmospheres, and by measuring lactic acid production during normoxic development. No evidence for oxygen limitation was observed. We also tested the hypothesis that the U-shaped metabolic curve follows changes in metabolically active tissue, such that the early decrease in metabolic rates reflects the histolysis of larval tissues, and the later increase in metabolic rates is associated with organogenesis and terminal differentiation of adult tissues. We assayed the activity of a mitochondrial indicator enzyme, citrate synthase, and correlated it with tissue-specific developmental events during metamorphosis. Citrate synthase activity exhibited a U-shaped curve, suggesting that the pattern of metabolic activity is related to changes in the amount of potentially active aerobic tissue.

Cholangiocyte apoptosis is an early event during induced metamorphosis in the sea lamprey, Petromyzon marinus L

Background Research in biliary atresia has been hindered by lack of a suitable animal model. Lampreys are primitive vertebrates with distinct larval and adult life cycle stages. During metamorphosis the biliary system of the larval lamprey disappears. Lamprey metamorphosis has been proposed as a model for biliary atresia. We have begun to explore cellular events during lamprey metamorphosis by assessing for cholangiocyte apoptosis. Materials and Methods Sea lamprey larvae were housed under controlled environmental conditions. Premetamorphic larvae were induced to undergo metamorphosis by exposure to 0.01% KClO 4. Animals were photographed weekly, and the stage of metamorphosis was assigned based upon external features. Livers were harvested and processed for routine histology and immunohistochemistry. DNA fragmentation was detected using deoxynucleotidyl transferase–mediated dUTP-biotin nick end labeling (TUNEL) assays and cholangiocytes were identified with antibodies to cytokeratin-19. Percent TUNEL+ cholangiocytes at different stages of metamorphosis was determined. Results The percentage of TUNEL+ cholangiocytes was 10% in premetamorphic (stage 0) lamprey (n = 6), 51% at stage 1 (n = 6), 40% at stage 2 (n = 5), 18% at stage 3 (n = 5), and 9% stage 4 (n = 4). Routine hemotoxylin and eosin stained paraffin-embedded tissue sections revealed frequent apoptotic bodies at stages 3 and 4 of metamorphosis without histologic evidence of necrosis. Conclusions DNA fragmentation is identified at the earliest stages of metamorphosis during induced metamorphosis in lampreys. Additional studies are necessary to validate this potentially valuable animal model.

Microdajus tchesunovi sp. n. (Tantulocarida, Microdajidae) – A new crustacean parasite of from the White Sea

A new species of Tantulocarida, Microdajus tchesunovi sp. n., was found on tanaid host, Typhlotanais sp. of the family Nototanaidae, collected from silty sediment in the Kandalaksha Bay in the White Sea. Several tantulus larvae, developing males at different stages of metamorphosis, and early stages of parthenogenetic females were found attached to different sites of their hosts. Ultrastructure of the new species was studied with SEM. Microdajus tchesunovi sp. n. can be easily distinguished from other species of the genus Microdajus Greve by the presence of a pair of longitudinal dorsal lamellae at the anterior end of the cephalon. It is also characterized by the presence of an endopod seta on the sixth thoracopod and the absence of thoracopodal endites. A morphological comparison of species of the family Microdajidae is presented in tabular form.

Dietary Retinoic Acid Induces Hindlimb and Eye Deformities inXenopus laevis

This study investigated the effects of dietary retinoic acid (RA) on frog hindlimb development. Xenopus laevis (African clawed frog) tadpoles were fed a diet supplemented with 0, 1, 10, or 100 microg of RA/g of food for 2 or 5 d at different stages of metamorphosis. Hindlimb deformities were induced in the group fed 100 microg of RA/g of diet for 5 d. Exposures beginning at mid-hindlimb bud development induced bilaterally bent tibiafibula (bony triangles), while exposures later in hindlimb development induced deformities of the feet, including fusion of the 1st and 2nd clawed digits and reduced length of the 4th and 5th digits (due to reduced, missing, or misplaced phalanges). There were also cases of extra phalanges in the 5th digit. The eye was another target of RA exposure. In one experiment, 58% of the tadpoles fed 10 microg of RA/g had a smaller or absent right eye. Additionally, 11% of the tadpoles fed 100 microg of RA/g of diet developed a smaller or absent left eye. Waterborne heavy metals (Zn or Cu) modified RA effects on the hindlimb and eye. Co-exposure to metals and RA resulted in cases of unilateral bony triangles and reduced rates of smaller eyes. There were also cases of extra hindlimb digits in Zn-exposed animals. Dietary RA exposure in tadpoles can cause some deformities that differ from waterborne RA exposures in previous studies. RA also induced deformities that resemble those in affected wild frog populations (bony triangles), although the patterns of other deformities and missing segments (phalanges and metatarsals) are not similar to those documented in the wild.

Neurotrophin receptors and enteric neuronal development during metamorphosis in the amphibian Xenopus laevis.

During metamorphosis, the frog intestine goes through a dramatic shortening with extensive apoptosis and regeneration in the epithelial layer and connective tissue. Our aim was to study changes in the enteric nervous system represented by one inhibitory (vasoactive intestinal polypeptide; VIP) and one excitatory (substance P, neurokinin A; SP/NKA) nerve population and concomitant changes in neurotrophin receptor occurrence during this development in the gut of Xenopus laevis adults and tadpoles at different stages of metamorphosis (NF stages 57-66). Sections were incubated with antibodies against the neurotrophin Trk receptors and p75NTR, and the neurotransmitters VIP and SP/NKA. Trk-immunoreactive nerves increased dramatically but transiently in number during early metamorphic climax. Nerves immunoreactive for p75NTR were present throughout the gut, decreased in number in the middle intestine during climax, and increased in the large intestine during late metamorphosis. The percentage of VIP-immunoreactive nerves did not change during metamorphosis. SP/NKA-immunoreactive nerves were first apparent at NF stages 61-62 in the middle intestine and increased in the stomach and large intestine during metamorphosis. Endocrine cells expressing SP/NKA increased in number in stomach, proximal, and middle intestine during metamorphic climax. Thus, neurotrophin receptors are expressed transiently in neurons of the enteric nervous system during metamorphosis in Xenopus laevis and SP/NKA innervation is more abundant in the intestine of the postmetamorphic frog than in the tadpole.

Cloning of a thyroid hormone‐responsive Rana catesbeiana c‐erbA‐β gene

Two types of thyroid hormone receptor (c-erbA) gene have been identified in mammals and in lower species including chickens and the amphibian Xenopus laevis. The two genes are located on different chromosomes and have been named TR alpha and TR beta. We have described previously the cloning of a TR alpha cDNA from Rana catesbeiana (RC) tissues (RC15) and we now report the cloning of a TR beta cDNA from this species. The cloning strategy employed utilized the polymerase chain reaction (PCR), with primers based on the sequences of the X. laevis TR beta cDNA (XenTR beta) and an RCTR beta genomic clone, which, by analogy with XenTR beta, contains some of the 3' end of the open reading frame together with 3'-untranslated sequences. At the nucleotide and amino acid levels, respectively, the cloned RCTR beta cDNA is 90% and 98% homologous with XenTR beta, and 72% and 76% homologous with RC15. Following in vitro transcription and translation, the cDNA was shown to encode a 48 kilodalton protein which binds 3,5,3'-triiodothyronine (T3) with high affinity (mean Kd: 0.032 nM). Samples of total or poly(A) +RNA from tadpoles at different stages of metamorphosis and from adult frogs were analyzed for the presence of TR beta-specific transcripts by slot blot analysis using as probe a 258 bp section of the RCTR beta cDNA. This section of the cDNA does not hybridize to the corresponding section of RC15. In confirmation of previous findings, beta-specific transcripts were not detected in RNA from tadpole red blood cells (RBCs) and none was found in RBCs from adult frogs.(ABSTRACT TRUNCATED AT 250 WORDS)

Molecular cloning of hepatic mRNAs in Rana catesbeiana responsive to thyroid hormone during induced and spontaneous metamorphosis.

Amphibian metamorphosis affords a useful experimental system in which to study thyroid hormone regulation of gene expression during postembryonic vertebrate development. In order to isolate gene-specific cDNA probes which correspond to thyroid hormone-responsive mRNAs, we employed differential colony hybridization of a cDNA library constructed from poly(A)+ RNA of thyroxine-treated premetamorphic tadpole liver. From an initial screening of about 6000 transformants, 32 "potentially positive" colonies were obtained. The recombinant cDNA-plasmids from 13 of these colonies plus two "potentially negative" colonies were purified for further study. Southern blot analysis of the plasmid DNA was employed to determine whether different cDNAs encoded for the same mRNA. The effect of thyroid hormone on the relative levels of specific mRNA species was examined by Northern analysis of liver RNA from premetamorphic tadpoles, thyroxine-treated tadpoles, and adult bullfrogs. Three independent cDNA clones were obtained which encoded thyroid hormone-enhanced mRNAs. We also obtained two independent cDNA clones encoding thyroid hormone-inhibited mRNAs and three independent clones encoding thyroid hormone-unresponsive mRNAs. The levels of two thyroid hormone-enhanced mRNAs and one thyroid hormone-inhibited mRNA were essentially the same in the thyroid hormone-treated tadpole liver and adult liver, suggesting that thyroid hormone induces stable changes in liver gene expression during spontaneous metamorphosis. Using selected cDNAs, RNA dot blot analysis of liver mRNA from tadpoles at different stages of metamorphosis showed that the level of one thyroid hormone-enhanced mRNA increased during late prometamorphosis and metamorphic climax. Similarly, a mRNA which was strongly inhibited by thyroid hormone treatment was observed to decline during prometamorphosis and reach undetectable levels during metamorphic climax. One mRNA was detected which was reproducibly inhibited by thyroid hormone treatment but which remained essentially unchanged during spontaneous metamorphosis. These results provide the first direct evidence for the coordinate and selective pretranslational regulation by thyroid hormone of several liver genes during the developmental process of metamorphosis.

The complex dielectric constant of snow at microwave frequencies

The complex dielectric constant of snow has been measured at microwave frequencies. New and old snow at different stages of metamorphosis have been studied. The results indicate that the complex dielectric constant is practically independent of the structure of snow. For dry snow, the dielectric constant is determined by the density. For wet snow, the imaginary part and the increase of the real part due to liquid water have the same volumetric wetness dependence. The frequency dependence of the complex dielectric constant of wet snow is the same as that of water. A nomograph for determining the density and wetness of wet snow from its dielectric constant is given. A snow sensor for field measurement of the dielectric constant has been developed. It can be used for determining the density and the wetness of snow by a single measurement.

Beta-Endorphins (beta-EP) in amphibians: higher beta-EP levels during regenerating stages of anuran life cycle and immunocytochemical localization of beta-EP in regeneration blastemata.

Plasma beta-endorphin (beta-EP) levels were measured at different stages of metamorphosis in anuran species, namely Rana catesbeiana, R. pipiens, and Xenopus laevis. The mean levels of beta-EP in tadpoles and postmetamorphic juveniles were significantly higher than adult levels in all three species examined. The pattern of high tadpole levels and low adult levels corresponds with the limb regeneration ability of the tadpole and restriction in the adult. We have also reported plasma beta-EP levels in two urodele species, Ambystoma tigrinum and A. jeffersonianum. Localization of beta-EP by immunocytochemistry shows bright fluorescence to beta-EP antiserum in the wound epithelium of the regeneration blastema. The mesoderm and nuclei of all blastema cells remain nonreactive. It is suggested that receptors to beta-EP reside in the epidermis.

The evagination of the genital imaginal discs ofDrosophila melanogaster : I. Morphogenesis of the female genital disc.

The morphology of the evaginating female genital disc ofDrosophila melanogaster was examined at different stages of metamorphosis. The observations show that the internal genital organs are derived from the anterior half of the disc and that their morphogenesis is mainly a protrusion of the different primordial areas of the disc epithelium. The external genital and anal derivatives originate from the posterior half of the disc, which undergoes complex rearrangements during metamorphosis. The disc opens along the posterior margin and the dorsal and ventral epithelia evert and thereby completely reverse their anteroposterior orientation. Dramatic elongation has been observed during the formation of the seminal receptacle. The cells of the repressed male genital primordium do not form any recognizable structures and are assumed to be eliminated during metamorphosis.

Aktivierungsanalytische Beiträge zur Geochemie der Regionalmetamorphose

In order to investigate the behaviour of elements during the progressive regional metamorphosis 28 elements have been determined by radiochemical and instrumental NAA. The concentrations are determined in different stages of metamorphosis. The results enable us to classify the elements.

Extracellular ribosomes during metamorphosis of the blowfly [formula omitted] R. D. -- A reappraisal of their authenticity

Extracellular ribosomes during adult development of the blowfly Calliphora vicina were previously considered to occur naturally in vivo . A variety of radioisotopic experiments performed at different stages of metamorphosis now demonstrates that the specific activities of extra- and intracellular ribosomes are consistently very similar. Further, in addition to previously described physico-chemical similarities, extra- and intra-cellular ribosomal protein profiles are now shown to be essentially identical. These results vitiate the notion of a natural pool of extracellular ribosomes, the occurrence of which is now ascribed to an experimental artifact, resulting from unusual cell fragility.

Changes in the tail of Ambystoma maculatum at different stages of metamorphosis: observations on tissue remodeling and its relationship to hydrolytic enzymes.

A system for staging A. maculatum during growth and metamorphosis was devised, based on several parameters of body size; body length, tail length and tail width. Animals at various stages of metamorphosis were employed to study the relationship between specific biochemical and histological changes that occur in the tail of this urodele during metamorphosis. The specific and total activity of two hydrolytic enzymes, acid phosphatase and beta-N-acetyl-glucosaminidase, were measured in tail tissues at progressive stages of development. The activities of these enzymes increased in both the fins and muscular portion of the tail during metamorphosis. These activities can be correlated with resorption of the tail fins and the remodeling of tissues in the muscular portion of the tail.

Inhibition of thyroxine induced tail resorption in vitro by pituitary grafts from different stages of metamorphosis

AbstractIt has been previously demonstrated that isolated pieces (discs) from the tail fins of tadpoles (R. pipiens), survive in vitro for several weeks and respond to thyroxine by undergoing resorption. In addition, discs into which tadpole pituitary glands have been implanted or discs that have been injected with either prolactin or growth hormone undergo a delayed pattern of resorption on expsoure to thyroxine when compared to discs treated with thyroxine alone.Pituitaries were taken from early prometamorphic, climax and froglet stages and were implanted into tail discs cut from tadpoles in early prometamorphosis. These discs were maintained in thyroxine solutions. As controls, unimplanted discs were treated with thyroxine or maintained in Hanks solution. In a second series of experiments, tail discs were cut from tadpoles at progressive stages of prometamorphosis and treated with thyroxine solutions.The results demonstrate that pituitaries taken from different stages in the life cycle of this animal differ in their capacity to inhibit thyroxine induced tail resorption. The most effective inhibition is demonstrated by early prometamorphic pituitaries, followed by climax pituitaries. Froglet glands exhibit little activity. The results also demonstrate that the response of tail tissues to thyroxine increases during early prometamorphosis and with increasing rapidity during the last third of this period. These results are in harmony with the concept that amphibian metamorphosis may be dependent upon a bihormonal system in which thyroid hormone promotes while a prolactin‐like hormone counteracts this process.