Das Menschenfischlein und der Mensch – was uns der Grottenolm Proteus anguinus (Laurenti, 1768) über Langlebigkeit und Bevölkerungswachstum lehrt

Grottenolme Proteus anguinus (Laurenti, 1768) zeigen eine sehr geringe Fortpflanzungsrate, werden sehr alt und haben eine im Vergleich zum Menschen verzögerte Generationenfolge. Damit sind Olme Lebewesen für spannende evolutionsbiologische Fragestellungen, die sich um Populationswachstum drehen. Die vorliegende Arbeit zeigt auf, dass eine stabile Umwelt, wenig Krankheiten, das Fehlen von Fressfeinden und ausreichende Nahrungsressourcen evolutiv einen starken Einfluss auf das fehlende Populationswachstum beim Olm haben. Ein Vergleich mit dem Menschen eröffnet, neben der Bildung und dem Aufbrechen von Bräuchen, auch Wege naturgegebener Mechanismen, wie das Wachstum der Weltbevölkerung sich stabilisieren ließe. Der verzögerte Eintritt in die Reproduktion zeigt beim Grottenolm zudem einen positiven Effekt auf die Langlebigkeit. Human fish and human beings – European Cave Salamander Proteus anguinus (Laurenti, 1768) explains longevity and population growth Abstract: European Cave Salamanders, more specifically olms, show a low reproduction rate, reach methuselah ages and exhibit extended generation frequencies in comparison to humans. Olms are therefore considered an interesting study object for evolutionary questions about population growth. The paper discusses stable environment, good health, top predator position and continuous basic food supply as the key factors for stagnation of population growth in olms as well, if combined with education, as in humans. A late start of reproduction triggers in turn a positive impact on longevity.

Inferring predator–prey interaction in the subterranean environment: a case study from Dinaric caves

Predator–prey interactions are among the most important biotic interactions shaping ecological communities and driving the evolution of defensive traits. These interactions and their effects on species received little attention in extreme and remote environments, where possibilities for direct observations and experimental manipulation of the animals are limited. In this paper, we study such type of environment, namely caves of the Dinarides (Europe), combining spatial and phylogenetic methods. We focused on several species of Niphargus amphipods living in phreatic lakes, as some of them use the dorsal spines as putative morphological defensive traits. We predicted that these spines represent a defense strategy against the olm (Proteus anguinus), a top predator species in the subterranean waters. We tested for spatial overlap of the olm and Niphargus species and showed that spined species live in closer proximity to and co-occur more frequently with the olm than non-spined species. Modeling of the evolution of the spines onto Niphargus phylogeny implies coevolution of this trait in the presence of olm. We conclude that these spines likely evolved as defensive traits in a predator–prey arms race. Combining multiple analyses, we provide an example for a methodological framework to assess predator–prey interactions when in-situ or laboratory observations are not possible.

An underworld tailored to tourists: A dragon, a photo-model, and a bio-indicator

The history of studies of a subterranean tailed amphibian, known as the olm or proteus (Proteus anguinus), is a colorful indicator of the changing view of the world beneath our feet. Throughout history, the underground has been presented as other worldly inhabited by life not of this world. At first, caves were the habitat of ghosts and spirtits, and then as a symbol for hell with all its attributes. The olm, in light of this prominant worldview, is discussed here, in which its status changed from that of a mythical dragon, to a photo-model, to a biological indicator of environmental health. The mix of these roles, with which the modern notion of this animal is presented, is mostly generated by the experience of tourguides in Postojna Cave in Slovenia. For a long time, Postojna was the only place that the wider public recognized as a home for proteus. This clearly shows the need to analyze the popular media constructions of environment.

Alternative Animal Models of Aging Research

Most research on mechanisms of aging is being conducted in a very limited number of classical model species, i.e., laboratory mouse (Mus musculus), rat (Rattus norvegicus domestica), the common fruit fly (Drosophila melanogaster) and roundworm (Caenorhabditis elegans). The obvious advantages of using these models are access to resources such as strains with known genetic properties, high-quality genomic and transcriptomic sequencing data, versatile experimental manipulation capabilities including well-established genome editing tools, as well as extensive experience in husbandry. However, this approach may introduce interpretation biases due to the specific characteristics of the investigated species, which may lead to inappropriate, or even false, generalization. For example, it is still unclear to what extent knowledge of aging mechanisms gained in short-lived model organisms is transferable to long-lived species such as humans. In addition, other specific adaptations favoring a long and healthy life from the immense evolutionary toolbox may be entirely missed. In this review, we summarize the specific characteristics of emerging animal models that have attracted the attention of gerontologists, we provide an overview of the available data and resources related to these models, and we summarize important insights gained from them in recent years. The models presented include short-lived ones such as killifish (Nothobranchius furzeri), long-lived ones such as primates (Callithrix jacchus, Cebus imitator, Macaca mulatta), bathyergid mole-rats (Heterocephalus glaber, Fukomys spp.), bats (Myotis spp.), birds, olms (Proteus anguinus), turtles, greenland sharks, bivalves (Arctica islandica), and potentially non-aging ones such as Hydra and Planaria.

Paul Kammerer and epigenetics – a reappraisal of his experiments

During recent years, the scientific interest in the work of Austrian biologist Paul Kammerer (1880‒1926) has risen again. This development can largely be attributed to advances in the fields of epigenetics and epigenetic inheritance, and it resulted in provocative discussions. This article contributes to enhancing the knowledge about Kammerer’s publications in two respects. First, I provide a brief overview and contextualization of Kammerer’s main works on phenotypic plasticity and its inheritance, some of which seem little known at present. Thereafter, to ensure an accurate transmission of the historical record, I comment on recently published suggestive information about what Kammerer did and wrote, chiefly referring to Kammerer’s original writings on fire salamanders (Salamandra salamandra) and cave salamanders (Proteus anguinus). Although the exact contents of Kammerer’s writings remain controversial and must be regarded with caution, his writings need to be treated objectively and accurately to avoid historical record distortion and to render the performance of adequate replications of his experiments possible.

Welcome to the -omics era of the 21st century: will Proteus anguinus finally reveal all its mysteries?

There are few milestones in speleobiology, and Proteus anguinus, commonly named the olm, proteus or “human fish”, is undoubtedly part of its (hi)story. The animal was first mentioned in 1689 by Johann Weikhard von Valvasor (Janez Vajkard Valvasor) in his The Glory of the Duchy of Carniola (Slava Vojvodine Kranjske). The scientific name Proteus anguinus was given by Josephus Nicolaus Laurenti in 1768. The animal gained the interest of the scientific community later in the 19th century, culminating in 1859 in Charles Darwin's famous monograph On the Origin of Species as an example of evolutionary reduction of body structures through disuse. The study of this remarkable animal intensified in the 20th century. Its longevity, its general peculiarity and the mystery governing the underground world of the Dinaric karst triggered more systematic research. Much interesting data was obtained from study of proteus in captivity in various laboratories worldwide, including Slovenia, France, England, Belgium, Hungary, Germany and Italy. In the 21st century, the year 2019 represents another important milestone in the research of proteus. The draft genome of Proteus anguinus was first publicly presented on 25 November 2019 in Ljubljana, Slovenia. The event coincided with 330 years since proteus was introduced to the scientific community by Valvasor, 160 years since its popularization by Darwin, and the 100th anniversary of Ljubljana University. This is undoubtedly an achievement with many superlatives, starting from excellent collaboration among different international laboratories and the very short period – one year – used to finish the sequencing of the huge proteus genome, which is 15-times larger in size than the human genome. On this occasion, we spoke with the two most important players in the story, prof. Nina Gunde-Cimerman and prof. Rok Kostanjšek, from the University of Ljubljana, Biotechnical Faculty. Prof. Nina Gunde-Cimerman directs research of extremophiles adapted to extreme conditions, in particular fungi, at the Biotechnical Faculty. Prof. Rok Kostanjšek leads a research team that continues the investigation of proteus begun by his predecessors, prof. Lili Istenič and prof. Boris Bulog.

Dampened virulence and limited proliferation of Batrachochytrium salamandrivorans during subclinical infection of the troglobiont olm (Proteus anguinus)

Emerging infections add to existing threats to the survival of amphibians worldwide. The olm (Proteus anguinus) is a vulnerable, troglobiont urodele species with a small European range and restricted to underground karstic systems. Population declines to emerging threats like the chytrid fungus Batrachochytrium salamandrivorans, are likely to go unnoticed due to inaccessibility of the species’ habitat. We here studied the interaction between olms and B. salamandrivorans. Experimental inoculation of olms resulted in low-level, asymptomatic but persistent infections, with limbs as predilection sites. The lack of exponential fungal growth in the olms’ epidermis correlated with limited fungal proliferation and dampened virulence gene expression after exposure to olm skin compounds. The olm is one of few western Palearctic urodeles that is tolerant to B. salamandrivorans infection and may act as a subterranean disease reservoir, yet costs of subclinical infection may compromise olm fitness on the long term.

Switching from mesopredator to apex predator: how do responses vary in amphibians adapted to cave living?

The effective detection of both prey and predators is pivotal for the survival of mesopredators. However, the condition of being a mesopredator is strongly context dependent. Here we focus on two aquatic caudate species that have colonised caves: the Pyrenean newt (Calotriton asper) and the olm (Proteus anguinus). The former maintains both surface and subterranean populations, while only cave-adapted populations of the latter exist. Both species are apex predators in underground waterbodies, while the Pyrenean newt is a mesopredator in surface waterbodies. Shifting to a higher level of the trophic web through colonising caves may promote the loss of anti-predator response against surface apex predators, and an increase in the ability to detect prey. To test these two non-exclusive hypotheses, we integrated classical behavioural characterisations with a novel approach: the assessment of lateralisation (i.e. preference for one body side exposure). Behavioural experiments were performed using laboratory-reared individuals. We performed 684 trials on 39 Pyrenean newts and eight olms. Under darkness and light conditions, we tested how exposure to different chemical cues (predatory fish, prey and unknown scent) affected individuals’ activity and lateralisation. Both cave and surface Pyrenean newts responded to predator cues, while olms did not. In Pyrenean newts, predator cues reduced the time spent in movement and time spent in lateralisation associated with hunting. Our results show that predator recognition is maintained in a species where recently separated populations inhabit environments lacking of higher predators, while such behaviour tends to be lost in populations with longer history of adaptation. Significance statement Predator recognition can be maintained in animals adapted to predator free habitats, but varies with their history of adaptation. Species that are not at the apex of the food web can become top predators if they colonise subterranean environments. We compared the behavioural responses of the olm, a strictly cave species with a long underground evolutionary history, and of the Pyrenean newt, a facultative cave species that also has stream-dwelling populations. Moreover, we integrated a classical behavioural characterisation, such as movement detection, with a novel approach: the assessment of lateralisation. While olms do not respond to external predators scent, cave-dwelling newts still recognise it. This clearly indicates that predator recognition is still maintained in species that have colonised predator-free environments more recently.