Gynogenetic diploids, tetraploids, or octoploids, and a path to polyploidy in Anuran Amphibians

Unreduced gametes have been implicated in the evolution of polyploid species of plants and animals and are normally produced by female anuran amphibians. Such eggs may initiate the evolution of polyploid species that have independently arisen in several anuran families. Polyploid females could also produce unreduced eggs that might lead to species with higher ploidy levels or their eggs may develop gynogenetically to reduce the ploidy level. Diploid Hyla chrysoscelis (2n=24) and tetraploid H. versicolor (4n=48) are sibling cryptic species of North American Grey Treefrogs. Artificial crosses using H. versicolor females and genetically distant diploid males were performed to produce haploid H. versicolor and to assess the production of unreduced eggs in this tetraploid species. Gynogenetic diploid (haploid H. versicolor), allotriploid, gynogenetic tetraploid, allopentaploid, autohexaploid, and gynogenetic octoploid tadpoles were confirmed using chromosome counts from tadpole tail tip squashes. Transformation and survival of the different ploidies varied. Gynogenetic diploids transformed but expressed aspects of the haploid syndrome and died before or shortly after transformation.

Studi Osifikasi dan Morfokinetik Berudu Katak Rana catesbeiana Shaw. dengan Alizarin Red

Tadpole is a phase of frog metamorphosis. The frog tadpoles live in water, before the anterior extremities and posterior extremities are formed. Posterior limb growth is accompanied by calcifications and the anterior extremity followed by shortening of the tadpole tail. The aim research was to determine the ossification and morphokinetics of tadpoles in the posterior extremities, anterior limbs and tadpole tail shrinkage. The frog tadpoles do not have legs and move using tails. The research method uses descriptive quantitative techniques. The tadpoles were used a 4-month-old metamorphosis result. The bones have happened ossification that are marked by a change in the color of the bone to purplish red. The frog tadpoles develop in two phases, including the embryonic phase and the larval phase. The formation of hind limbs occurs in stages of 26-30, followed by toe development in stages of 31-37. The anterior extremities are corroded: the humerus os, the radio –ulna os, the os metacarpal and the falangs os, the posterior limb: the femoral os, the tibio-fibular os, the tarsal os and the metatarsal os. Keywords: Tadpoles, Ossification, extremities ABSTRAK Berudu merupakan salah satu fase dari metamorfosis katak. Berudu katak hidup di air, sebelum ekstremitas anterior dan ekstremitas posterior terbentuk. Pertumbuhan ekstremitas posterior dibarengi dengan kalsifikasi dan ekstremitas anterior diikuti dengan memendeknya ekor berudu. Tujuan penelitian ini untuk mengetahui osifikasi dan morfokinetik berudu bagian ekstremitas posterior, ekstremitas anterior dan penyusutan ekor berudu. Berudu katak tidak memiliki kaki dan bergerak menggunakan ekor. Metoda penelitian menggunakan Teknik kuantitatif deskriptif. Berudu yang digunakan adalah hasil metamorfosis usia 4 bulan. Tulang yang telah mengalami osifikasi ditandai dengan adanya perubahan warna pada tulang menjadi merah keunguan. Berudu katak mengalami perkembangan dalam dua fase, meliputi fase embrio dan fase larva. Terbentuknya kaki belakang terjadi pada tahap 26-30, dilanjutkan dengan terbentuknya jari kaki (toe development) pada tahap 31-37. Ekstremitas anterior yang terosifikasi : os humerus, os radio-ulna, os metacarpal dan os falangs, ekstremitas posterior : os femur, os tibio-fibula, os tarsal dan os metatarsal. Kata Kunci : Berudu, Osifikasi, Ekstremitas

Simulated predation pressure in Pelobates cultripes tadpoles modulates morphology at the metamorphic stage

Studies on the impacts of variation of biotic interactions at key life cycle stages are crucial to understand the interface between ecological and developmental processes. Predators exert a major impact on prey fitness. Although direct consumption entails the greatest effect, predators can affect prey by means of other mechanisms. For instance, injuries inflicted by failed predation attempts can jeopardize prey fitness, even beyond the short-term. In anuran tadpoles, failed predation typically results in partial tail loss, which is known to reduce swimming speed. However, the potential consequences of tadpole partial tail loss after metamorphosis remain understudied. Because tail materials could be important in conforming metamorph body, we assess the effects of tadpole partial tail loss on metamorph body size in Iberian spadefoot toads Pelobates cultripes. We clipped 55% tail length of pre-tail-resorption stage anesthetized tadpoles, and compared their body size as metamorphs with anesthetized and non-anesthetized non-tail-clipped controls. Also, we tested whether tail length correlated with metamorph body size of individuals of the control groups. Tail-clipped tadpoles produced smaller metamorphs than both controls (the bdy size of metamorphs from both controls was similar), which could incur costs in mid-term survival or time to first reproduction. This effect could be particularly important in areas with introduced predators, if autochthonous tadpoles lack defenses against them. Results suggest that materials resorbed from tadpole tail tissues might be reallocated into metamorph body, according to the negative effect of shorter tails in a correlational analysis, and clipped tails in an experimental test, on metamorph body size.

Bacteria are required for regeneration of the Xenopus tadpole tail

The impressive regenerative capabilities of amphibians have been studied for over a century. Although we have learnt a great deal about regenerative processes, the factors responsible for the initiation of regeneration have remained elusive. A previous study implicated reactive oxygen species (ROS) and the ROS-generator, NADPH oxidase (Nox), in Xenopus tadpole tail regeneration. In this study we suggest that Nox is expressed as a consequence of NF-κB transcription factor activity and that ROS produced by Nox, in turn, help to maintain the activity of NF-κB, forming a positive-feedback loop. Microorganisms were found to be required for regeneration through binding to toll-like receptors (TLR). NF-κB is a downstream component of TLR pathways and its activation through TLR stimulation could jump-start the positive-feedback loop. These findings provide potential targets for the activation of regeneration in non-regenerative animals.