Open Access. Powered by Scholars. Published by Universities.®
- Keyword
-
- Direct development (6)
- E. coqui (3)
- Frogs (3)
- Skeletal development (3)
- Symbiosis (3)
-
- Development (2)
- Endosymbiosis (2)
- Evolution (2)
- Evolution and development (2)
- Life history evolution (2)
- Limb development (2)
- Plethodontidae (2)
- Xenopus (2)
- Xenopus laevis (2)
- Ambystoma (1)
- Amphibian (1)
- Anura (1)
- Bone (1)
- Cartilage (1)
- Cartilage formation (1)
- Chlorophyte (1)
- Chondrocyte (1)
- Col2a1 (1)
- Cranial patterning (1)
- Dollo's law (1)
- Dollo’s Law (1)
- Embryology (1)
- Evolutionary developmental biology (1)
- Gigantism (1)
- Green algae (1)
- File Type
Articles 1 - 12 of 12
Full-Text Articles in Life Sciences
Do Larval Traits Re-Evolve? Evidence From The Embryogenesis Of A Direct-Developing Salamander, Plethodon Cinereus, Ryan Kerney, David Blackburn, Hendrik Muller, James Hanken
Do Larval Traits Re-Evolve? Evidence From The Embryogenesis Of A Direct-Developing Salamander, Plethodon Cinereus, Ryan Kerney, David Blackburn, Hendrik Muller, James Hanken
Ryan Kerney
Recent molecular phylogenies suggest the surprising reacquisition of posthatching metamorphosis within an otherwise directdeveloping clade of lungless salamanders (family Plethodontidae). Metamorphosis was long regarded as plesiomorphic for plethodontids, yet the genus Desmognathus, which primarily includes metamorphosing species, is now nested within a much larger clade of direct-developing species. The extent to which the putative reacquisition of metamorphosis in Desmognathus represents a true evolutionary reversal is contingent upon the extent to which both larva-specific features and metamorphosis were actually lost during the evolution of direct development. In this study we analyze development of the hyobranchial skeleton, which is dramatically remodeled during …
Intracellular Invasion Of Green Algae In A Salamander Host, Ryan Kerney, Eunsoo Kim, Roger Hangater, Aaron Heiss, Cory Bishop, Brian Hall
Intracellular Invasion Of Green Algae In A Salamander Host, Ryan Kerney, Eunsoo Kim, Roger Hangater, Aaron Heiss, Cory Bishop, Brian Hall
Ryan Kerney
The association between embryos of the spotted salamander (Ambystoma maculatum) and green algae (“Oophila amblystomatis” Lamber ex Printz) has been considered an ectosymbiotic mutualism. We show here, however, that this symbiosis is more intimate than previously reported. A combination of imaging and algal 18S rDNA amplification reveals algal invasion of embryonic salamander tissues and cells during development. Algal cells are detectable from embryonic and larval Stages 26–44 through chlorophyll autofluorescence and algal 18S rDNA amplification. Algal cell ultrastructure indicates both degradation and putative encystment during the process of tissue and cellular invasion. Fewer algal cells were detected in later-stage larvae …
Symbioses Between Salamander Embryos And Green Algae, Ryan Kerney
Symbioses Between Salamander Embryos And Green Algae, Ryan Kerney
Ryan Kerney
The symbiosis between Ambystoma maculatum (spotted salamander) embryos and green algae was initially described over 120 years ago. Algae populate the egg capsules that surround individual A. maculatum embryos, giving the intracapsular fluid a characteristic green hue. Early work established this symbiosis to be a mutualism, while subsequent studies sought to identify the material benefits of this association to both symbiont and host. These studies have shown that salamander embryos benefit from increased oxygen concentrations provided by their symbiotic algae. The algae, in turn, may benefit from ammonia excreted by the embryos. All of these early studies considered the associ- …
Molecular Anatomy Of The Developing Limb In The Coqu ́I Frog, Eleutherodactylus Coqui, Joshua Gross, Ryan Kerney, James Hanken, Clifford Tabin
Molecular Anatomy Of The Developing Limb In The Coqu ́I Frog, Eleutherodactylus Coqui, Joshua Gross, Ryan Kerney, James Hanken, Clifford Tabin
Ryan Kerney
The vertebrate limb demonstrates remark- able similarity in basic organization across phylogenetically disparate groups. To gain further insight into how this mor- phological similarity is maintained in different developmental contexts, we explored the molecular anatomy of size-reduced embryos of the Puerto Rican coqu ́ı frog, Eleutherodactylus coqui. This animal demonstrates direct development, a life- history strategy marked by rapid progression from egg to adult and absence of a free-living, aquatic larva. Nonethe- less, coqu ́ı exhibits a basal anuran limb structure, with four toes on the forelimb and five toes on the hind limb. We in- vestigated the extent to …
Levels Of Biological Organization And The Origin Of Novelty, Brian Hall, Ryan Kerney
Levels Of Biological Organization And The Origin Of Novelty, Brian Hall, Ryan Kerney
Ryan Kerney
The concept of novelty in evolutionary biology pertains to multiple tiers of biological organization from behavioral and morphological changes to changes at the molecular level. Identifying novel features requires assessments of similarity (homology and homoplasy) of relationships (phylogenetic history) and of shared developmental and genetic pathways or networks. After a brief discussion of how novelty is used in recent literature, we discuss whether the evolutionary approach to homology and homoplasy initially formulated by Lankester in the 19th century informs our understanding of novelty today. We then discuss six examples of morphological features described in the recent literature as novelties, and …
Embryonic Staging Table For A Direct- Developing Salamander, Plethodon Cinereus (Plethodontidae), Ryan Kerney
Embryonic Staging Table For A Direct- Developing Salamander, Plethodon Cinereus (Plethodontidae), Ryan Kerney
Ryan Kerney
This work presents a refined staging table for the direct-developing red-backed salamander Plethodon cinereus, which is based on the incom- plete staging system of James Norman Dent (J Morphol 1942; 71:577– 601). This common species from eastern North America is a member of the species-rich lungless salamander family Plethodontidae. The stag- ing table presented here covers several stages omitted by Dent and reveals novel developmental features of P. cinereus embryos. These include putative Leydig cells and open gill clefts, which are found in lar- vae of metamorphosing species but were previously reported as absent in direct-developing Plethodon. Other features found …
Early Cranial Patterning In The Direct-Developing Frog Eleutherodactylus Coqui Revealed Through Gene Expression, Ryan Kerney, Joshua Gross, James Hanken
Early Cranial Patterning In The Direct-Developing Frog Eleutherodactylus Coqui Revealed Through Gene Expression, Ryan Kerney, Joshua Gross, James Hanken
Ryan Kerney
Genetic and developmental alterations associated with the evolution of amphibian direct development remain largely unexplored. Specifically, little is known of the underlying expression of skeletal regulatory genes, which may reveal early modifications to cranial ontogeny in direct-developing species. We describe expression patterns of three key skeletal regulators (runx2, sox9, and bmp4) along with the cartilage-dominant collagen 2a1 gene (col2a1) during cranial development in the direct- developing anuran, Eleutherodactylus coqui. Expression patterns of these regulators reveal transient skeletogenic anlagen that correspond to larval cartilages, but which never fully form in E. coqui. Suprarostral anlagen in the frontonasal processes are detected through …
Regulatory Elements Of Xenopus Col2a1 Drive Cartilaginous Gene Expression In Transgenic Frogs, Ryan Kerney, Brian K. Hall, James Hanken
Regulatory Elements Of Xenopus Col2a1 Drive Cartilaginous Gene Expression In Transgenic Frogs, Ryan Kerney, Brian K. Hall, James Hanken
Ryan Kerney
This study characterizes regulatory elements of collagen 2α1 (col2a1) in Xenopus that enable transgene expression in cartilage-forming chondrocytes. The reporters described in this study drive strong cartilage-specific gene expression, which will be a valuable tool for further investigations of Xenopus skeletal development. While endogenous col2a1 mRNA is expressed in many embryonic tissues, its expression becomes restricted to tadpole and adult chondrocytes. This chondrocyte-specific expression is recapitulated by col2a1 reporter constructs, which were tested through I-SceI meganuclease-mediated transgenesis. These constructs contain a portion of the Xenopus tropicalis col2a1 intron, which aligns to a cartilage-specific intronic enhancer that has been well characterized …
Skeletal Advance And Arrest In Giant Non-Metamorphosing African Clawed Frog Tadpoles (Xenopus Laevis: Daudin), Ryan Kerney, Richard Wassersug, Brian Hall
Skeletal Advance And Arrest In Giant Non-Metamorphosing African Clawed Frog Tadpoles (Xenopus Laevis: Daudin), Ryan Kerney, Richard Wassersug, Brian Hall
Ryan Kerney
This study examines the skeletons of giant non-metamorphosing (GNM) Xenopus laevis tadpoles, which arrest their development indefinitely before metamorphosis, and grow to excessively large sizes in the absence of detectable thyroid glands. Cartilage growth is isometric; however, chondrocyte size is smaller in GNM tadpoles than in controls. Most cartilages stain weakly with alcian blue, and several cartilages are calcified (unlike con- trols). However, cartilages subjacent to periosteum-derived bone retain strong affinities for alcian blue, indicat- ing a role for periosteum-derived bone in the retention of glycosaminoglycans during protracted larval growth. Bone formation in the head, limb, and axial skeletons is …
Gene Expression Reveals Unique Skeletal Patterning In The Limb Of The Direct-Developing Frog, Eleutherodactylus Coqui, Ryan Kerney, James Hanken
Gene Expression Reveals Unique Skeletal Patterning In The Limb Of The Direct-Developing Frog, Eleutherodactylus Coqui, Ryan Kerney, James Hanken
Ryan Kerney
The growing field of skeletal developmental biology provides new molecular markers for the cellular pre- cursors of cartilage and bone. These markers enable resolution of early features of skeletal development that are otherwise undetectable through conventional staining tech- niques. This study investigates mRNA distributions of skeletal regulators runx2 and sox9 along with the cartilage-dominant collagen 2a1 (col2a1) in embryonic limbs of the direct- developing anuran, Eleutherodactylus coqui. To date, distri- butions of these genes in the limb have only been examined in studies of the two primary amniote models, mouse and chicken. In E. coqui, expression of transcription factors runx2 …
Runx2 Is Essential For Larval Hyobranchial Cartilage Formation In Xenopus Laevis, Ryan Kerney, Joshua Gross, James Hanken
Runx2 Is Essential For Larval Hyobranchial Cartilage Formation In Xenopus Laevis, Ryan Kerney, Joshua Gross, James Hanken
Ryan Kerney
The vertebrate transcription factor protein Runx2 is regarded as a “master regulator” of bone formation due to the dramatic loss of the osseous skeleton in the mouse homozygous knockout. However, Runx2 mRNA also is expressed in the pre-hypertrophic cartilaginous skeleton of the mouse and chicken, where its developmental function is largely unknown. Several tiers of Runx2 regulation exist in the mouse, any of which may account for its seeming biological inactivity during early stages of skeletogenesis. Unlike mouse and chicken, zebrafish require Runx2 function in early cartilage differentiation. The present study reveals that the earlier functional role of Runx2 in …
Cranial Ontogeny In Philautus Silus (Anura: Ranidae: Rhacophorinae) Reveals Few Similarities With Other Direct-Developing Anurans, Ryan Kerney, Madhava Meegaskumbura, Kelum Manamendra-Arachchi, James Hanken
Cranial Ontogeny In Philautus Silus (Anura: Ranidae: Rhacophorinae) Reveals Few Similarities With Other Direct-Developing Anurans, Ryan Kerney, Madhava Meegaskumbura, Kelum Manamendra-Arachchi, James Hanken
Ryan Kerney
Direct development has evolved in rhaco- phorine frogs independently from other anuran lineages, thereby offering an opportunity to assess features associ- ated with this derived life history. Using a developmen- tal series of the direct-developing Philautus silus (Ranidae: Rhacophorinae) from Sri Lanka, we examine features of cranial morphology that are part of a suite of adaptations that facilitate feeding in free-living tadpoles, but have been changed or lost in other direct-developing lineages. Larval-specific upper jaw cartilages, which are absent from many non-rhacophorine direct-developing species (such as Eleutherodactylus coqui), develop in embryos of P. silus. Similarly, lower jaw cartilages ini- tially …