Abstract
Background
Lightless caves can harbour a wide range of living organisms. Cave animals have evolved a set of morphological, physiological, and behavioural adaptations known as ...troglomorphisms, enabling their survival in the perpetual darkness, narrow temperature and humidity ranges, and nutrient scarcity of the subterranean environment. In this study, we focused on adaptations of skull shape and sensory systems in the blind cave salamander, Proteus anguinus, also known as olm or simply proteus—the largest cave tetrapod and the only European amphibian living exclusively in subterranean environments. This extraordinary amphibian compensates for the loss of sight by enhanced non-visual sensory systems including mechanoreceptors, electroreceptors, and chemoreceptors. We compared developmental stages of P. anguinus with Ambystoma mexicanum, also known as axolotl, to make an exemplary comparison between cave- and surface-dwelling paedomorphic salamanders.
Findings
We used contrast-enhanced X-ray computed microtomography for the 3D segmentation of the soft tissues in the head of P. anguinus and A. mexicanum. Sensory organs were visualized to elucidate how the animal is adapted to living in complete darkness. X-ray microCT datasets were provided along with 3D models for larval, juvenile, and adult specimens, showing the cartilage of the chondrocranium and the position, shape, and size of the brain, eyes, and olfactory epithelium.
Conclusions
P. anguinus still keeps some of its secrets. Our high-resolution X-ray microCT scans together with 3D models of the anatomical structures in the head may help to elucidate the nature and origin of the mechanisms behind its adaptations to the subterranean environment, which led to a series of troglomorphisms.
An attractive approach in the study of human cancers is the use of transparent zebrafish (Danio rerio) embryos, which enable the visualization of cancer progression in a living animal.
We implanted ...mixtures of fluorescently labeled glioblastoma (GBM) cells and bonemarrow-derived mesenchymal stem cells (MSCs) into zebrafish embryos to study the cellular pathways of their invasion and the interactions between these cells in vivo.
By developing and applying a carbocyanine-dye-compatible clearing protocol for observation of cells in deep tissues, we showed that U87 and U373 GBM cells rapidly aggregated into tumor masses in the ventricles and midbrain hemispheres of the zebrafish embryo brain, and invaded the central nervous system, often using the ventricular system and the central canal of the spinal cord. However, the GBM cells did not leave the central nervous system. With co-injection of differentially labeled cultured GBM cells and MSCs, the implanted cells formed mixed tumor masses in the brain. We observed tight associations between GBM cells and MSCs, and possible cell-fusion events. GBM cells and MSCs used similar invasion routes in the central nervous system.
This simple model can be used to study the molecular pathways of cellular processes in GBM cell invasion, and their interactions with various types of stromal cells in double or triple cell co-cultures, to design anti-GBM cell therapies that use MSCs as vectors.
A major goal of genomic and reproductive biology is to understand the evolution of sex determination and sex chromosomes. Species of the 2 genera of the Salamander family Proteidae - Necturus of ...eastern North America, and Proteus of Southern Europe - have similar-looking karyotypes with the same chromosome number (2n = 38), which differentiates them from all other salamanders. However, Necturus possesses strongly heteromorphic X and Y sex chromosomes that Proteus lacks. Since the heteromorphic sex chromosomes of Necturus were detectable only with C-banding, we hypothesized that we could use C-banding to find sex chromosomes in Proteus. We examined mitotic material from colchicine-treated intestinal epithelium, and meiotic material from testes in specimens of Proteus, representing 3 genetically distinct populations in Slovenia. We compared these results with those from Necturus. We performed FISH to visualize telomeric sequences in meiotic bivalents. Our results provide evidence that Proteus represents an example of sex chromosome turnover in which a Necturus-like Y-chromosome has become permanently translocated to another chromosome converting heteromorphic sex chromosomes to homomorphic sex chromosomes. These results may be key to understanding some unusual aspects of demographics and reproductive biology of Proteus, and are discussed in the context of models of the evolution of sex chromosomes in amphibians.
Magnéli phase titanium suboxides (Magnéli TiO x ) are novel conductive materials with great industrial potential. This is the first comprehensive investigation to provide an extensive dataset for ...hazard characterisation of Magnéli TiO x using six standardised test organisms and two human cell lines. Three Magnéli TiO x particles and three anatase crystalline phase TiO 2 nanomaterials with different primary powder sizes, but similar hydrodynamic diameters in biological media, were investigated. All Magnéli TiO x and TiO 2 nanomaterials induced negligible biological responses in Tetrahymena thermophila , Lemna minor , Artemia franciscana and Danio rerio . Adverse effects were found only at 100 mg L −1 where approximately 50% endpoint inhibition was recorded in the cases of Daphnia magna exposed to two Magnéli TiO x , Pseudokirchneriella subcapitata exposed to all three Magnéli TiO x and HepG2 cells exposed to one type of Magnéli TiO x . This study provides the first evidence that the tested Magnéli TiO x are not acutely hazardous according to existing EU classification for conventional chemicals.
Proteus anguinus
is a neotenic cave salamander, endemic to the Dinaric Karst and a symbol of world natural heritage. It is classified as “vulnerable” by the International Union for Conservation of ...Nature (IUCN) and is one of the EU priority species in need of strict protection. Due to inaccessibility of their natural underground habitat, scientific studies of the olm have been conducted mainly in captivity, where the amphibians are particularly susceptible to opportunistic microbial infections. In this report, we focused on the diversity of cultivable commensal fungi isolated from the skin of asymptomatic and symptomatic animals obtained from nature (20 specimens) and captivity (22 specimens), as well as from underground water of two karstic caves by direct water filtration and by exposure of keratin-based microbial baits and subsequent isolation from them. In total 244 fungal isolates were recovered from the animals and additional 153 isolates were obtained from water samples. Together, these isolates represented 87 genera and 166 species. Symptomatic animals were colonized by a variety of fungal species, most of them represented by a single isolate, including genera known for their involvement in chromomycosis, phaeohyphomycosis and zygomycosis in amphibians:
Acremonium
,
Aspergillus
,
Cladosporium
,
Exophiala
,
Fusarium
,
Mucor
,
Ochroconis
,
Phialophora
and
Penicillium
. One symptomatic specimen sampled from nature was infected by the oomycete
Saprolegnia parasitica
, the known causative agent of saprolegniosis. This is the first comprehensive report on cultivable skin mycobiome of this unique amphibian in nature and in captivity, with an emphasis on potentially pathogenic fungi and oomycetes.
The European blind cave salamander, Proteus anguinus, is a neotenic, permanently aquatic amphibian with a very long life span, late sexual maturity, and the ability to reproduce for at least 30 ...years. Proteus is considered to be vulnerable species, and yet very little is known about its reproductive biology. The objective of this study is to describe the detailed morphology of the testes of adult Proteus and determine the maturation state of the gonads and gametogenesis with respect to body size and seasonality. This research showed that testis size increases with adult male body length, but the shape and meiotic condition of the testes are highly variable and independent of the length of the specimen. The testis of Proteus has a simple cystic type of organization in which cysts are enclosed in lobules, with synchronous maturation of the germ cells within each cyst. Spermatogenesis progresses in a caudocephalic direction within the testis, as in other salamanders, and appears to be seasonal, despite the fact that Proteus is a cave animal living in stable environmental conditions. Surprisingly, the testes of approximately one third of the specimens, regardless oftheir morphology or meiotic condition, contained testis-ova located randomly among groups of spermatogonia and spermatocytes. These testes-ova contained germinal vesicles with lampbrush chromosomes, and thus correspond to primary oocytes. Thepresence of testis-ova may be related to a sex-chromosome turnover involving X-Y translocation that was recently discovered in Proteus.
Neuromasts are mechanosensory organs found in primarily aquatic vertebrates, including many species of amphibians, and are arranged as specific patterns to form the lateral-line system on the head ...and along the body. We used a hair-cell-specific fluorescent dye, DiASP, to analyze the distributional pattern of neuromasts in the lateral line system of live captive-born larvae of the Italian crested newt, Triturus carnifex (Laurenti, 1768). We confirmed that DiASP presents a safe and accurate alternative method for non-destructive studies of neuromast ontogeny and distribution in live amphibians. All newt larvae subjected to analyses survived and no teratogenic effects of DiASP on their further development were observed. We were able to use these data to completely characterize the distribution of neuromasts in this species and to infer the functional significance of this distribution. Cross-species comparison of general topography points to neuromast arrangement as a conserved trait in urodelans.
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