Egon Heiss

Egon Heiss
Ark-Biodiversity

28.43
 · 
Dr.

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48
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427
Citations

Publications

Publications (48)
Article
Full-text available
Many organisms faced with seasonally fluctuating abiotic and biotic conditions respond by altering their phenotype to account for the demands of environmental changes. Here we discovered that newts, which switch seasonally between an aquatic and terrestrial lifestyle, grow a complex adhesive system on their tongue pad consisting of slender lingual...
Article
Full-text available
Transitions between aquatic and terrestrial prey capture are challenging. Trophic shifts demand a high degree of behavioral flexibility to account for different physical circumstances between water and air to keep performance in both environments. The Himalayan newt, T. verrucosus is mostly terrestrial but becomes aquatic during its short breeding...
Preprint
Full-text available
Background: Salamander morphology changes substantially during metamorphosis, prompting the hypothesis that larvae need a different processing mechanism than post-metamorphic adults. Salamandrid newts with facultative metamorphosis are suitable for testing this hypothesis, because paedomorphic and metamorphic adults often coexist in the same popula...
Preprint
Full-text available
Background: The feeding apparatus of salamanders consists mainly of the cranium, mandible, teeth, hyobranchial apparatus and the muscles of the cranial region. The morphology of the feeding apparatus in turn determines the boundary conditions for possible food processing mechanisms. However, the morphology of the feeding apparatus changes substanti...
Article
Full-text available
It is generally accepted that most non-mammal tetrapods have a hinge-like jaw operation restricted to vertical opening and closing movements. Many mammal jaw joints, by contrast, operate in more complex, three-dimensional ways, involving not only vertical, but also propalinal (rostro-caudal) and transverse (lateral) movements. Data on intraoral foo...
Article
Full-text available
Abstract Paedomorphosis describes the retention of larval characters in adult stages and is widespread amongst salamanders. Salamandrid newts exhibit facultative paedomorphosis, where paedomorphic and metamorphic adult forms coexist in the same population. Previous studies have shown that prey capture kinematics do not differ between paedomorphic a...
Chapter
Turtles are one of the oldest known sauropsid orders that appeared about 240 million years ago. Within the vertebrates, they have evolved the most unusual body plan, with most of their body inside a protective box made of bone and keratin. This peculiar morphology has persisted since the late Triassic, but has allowed them to adapt to very diverse...
Article
Full-text available
Food processing refers to any form of mechanical breakdown of food prior to swallowing. Variations of this behaviour are found within all major gnathostome groups. Chewing is by far the most commonly used intraoral processing mechanism and involves rhythmic mandibular jaw and hyobranchial (tongue) movements. Chewing occurs in chondrichthyans (shark...
Article
Full-text available
Background Amphibians have evolved a remarkable diversity of defensive mechanisms against predators. One of the most conspicuous components in their defense is related to their ability to produce and store a high variety of bioactive (noxious to poisonous) substances in specialized skin glands. Previous studies have shown that T. verrucosus is pois...
Article
Full-text available
Transitions to terrestrial environments confront ancestrally aquatic animals with several mechanical and physiological problems owing to the different physical properties of water and air. As aquatic feeders generally make use of flows of water relative to the head to capture, transport and swallow food, it follows that morphological and behavioral...
Article
Full-text available
The European Pond Turtle is a predominantly aquatic species, generally assumed to feed exclusively under water by using hydrodynamic mechanisms. We analysed the kinematics of the aquatic food uptake and food transport by using high-speed videos with 500 fps. The analyses revealed that subadult E. orbicularis use compensatory suction for food uptake...
Article
Full-text available
Salamanders have evolved a wide variety of antipredator mechanisms and behavior patterns, including toxins and noxious or adhesive skin secretions. The high bonding strength of the natural bioadhesives makes these substances interesting for biomimetic research and applications in industrial and medical sectors. Secretions of toxic species may help...
Article
Full-text available
A unique example of phenotypic flexibility of the oral apparatus is present in newts (Salamandridae) that seasonally change between an aquatic and a terrestrial habitat. Newts grow flaps of skin between their upper and lower jaws, the labial lobes, to partly close the corners of the mouth when they adopt an aquatic lifestyle during their breeding s...
Article
Full-text available
Some newt species change seasonally between an aquatic and a terrestrial life as adults, and are therefore repeatedly faced with different physical circumstances that affect a wide range of functions of the organism. For example, it has been observed that seasonally habitat-changing newts display notable changes in skin texture and tail fin anatomy...
Article
Full-text available
Almost all extant testudinids are highly associated with terrestrial habitats and the few tortoises with high affinity to aquatic environments are found within the genus Manouria. Manouria belongs to a clade which forms a sister taxon to all remaining tortoises and is suitable as a model for studying evolutionary transitions within modern turtles....
Article
Full-text available
To capture and swallow food on land, a sticky tongue supported by the hyoid and gill arch skeleton has evolved in land vertebrates from aquatic ancestors that used mouth-cavity-expanding actions of the hyoid to suck food into the mouth. However, the evolutionary pathway bridging this drastic shift in feeding mechanism and associated hyoid motions r...
Article
Full-text available
Biting is an integral feature of the feeding mechanism for aquatic and terrestrial salamanders to capture, fix or immobilize elusive or struggling prey. However, little information is available on how it works and the functional implications of this biting system in amphibians although such approaches might be essential to understand feeding system...
Article
Full-text available
Modern digital high-speed film systems are able to capture sequences by extremely high frame rates – over 100 000 fr/s. The equipment costs for such systems are high but the operational costs are practically zero. An important advantage of digital versus analogue high-speed films is the possibility to automatically "digitize" defined markers. The c...
Article
Full-text available
Transitions between aquatic and terrestrial habitats are significant steps in vertebrate evolution. Due to the different biophysical demands on the whole organism in water and air, such transitions require major changes of many physiological functions, including feeding. Accordingly, the capability to modulate the pre-programmed chain of prey-captu...
Article
Full-text available
Transitions between aquatic and terrestrial environments are significant steps in vertebrate evolution. These transitions require major changes in many biological functions, including food uptake and transport. The Alpine newt, Ichthyosaura alpestris, is known to show a 'multiphasic lifestyle' where the adult shifts from a terrestrial to an aquatic...
Article
Full-text available
During the evolutionary transition from fish to tetrapods, a shift from uni- to bidirectional suction feeding systems followed a reduction in the gill apparatus. Such a shift can still be observed during metamorphosis of salamanders, although many adult salamanders retain their aquatic lifestyle and feed by high-performance suction. Unfortunately,...
Article
Full-text available
The oropharynx as a functional entity plays a fundamental role in feeding. Transitions from aquatic to terrestrial lifestyles in vertebrates demanded major changes of the oropharynx for the required adaptations to a different feeding environment. Extant turtles evolved terrestrial feeding modes in three families (testudinids, emydids, geoemydids)-i...
Article
Full-text available
In tetrapods, the ability to ingest food on land is based on certain morphological features of the oropharynx in general and the feeding apparatus in particular. Recent paleoecological studies imply that terrestrial feeding has evolved secondarily in turtles, so they had to meet the morphological oropharyngeal requirements independently to other am...
Article
Full-text available
The present study examined the kinematic patterns of initial food uptake, food transport, pharyngeal packing and swallowing in the common musk turtle Sternotherus odoratus. These data are supplemented by morphological descriptions of the skull and the hyolingual complex. Although the hyoid is mainly cartilaginous, S. odoratus still use exclusively...
Article
Full-text available
The weberian apparatus of otophysine fishes facilitates sound transmission from the swimbladder to the inner ear to increase hearing sensitivity. It has been of great interest to biologists since the 19(th) century. No studies, however, are available on the development of the weberian ossicles and its effect on the development of hearing in catfish...
Article
Full-text available
In tetrapods, the oropharyngeal cavity and its anatomical structures are mainly, but not exclusively, responsible for the uptake and intraoral transport of food. In this study, we provide structural evidence for a second function of the oropharynx in the North American common musk turtle, Sternotherus odoratus, Kinosternidae: aquatic gas exchange....
Article
Full-text available
The Indochinese box turtle Cuora galbinifrons is regarded as a purely terrestrial species, but our results demonstrate that it can feed both on land and in water. The inverse relationship between the relative development of the hyoid apparatus and the tongue found in the most investigated chelonians is not valid in the Indochinese box turtle. Our m...
Article
Full-text available
The Spanish ribbed newt Pleurodeles waltl shows a bizzare defensive mechanism against predators. X-ray analysis before and after a simulated threat shows that this newt rotates its ribs anteriorly. The maximum measured angle to which the ribs moved was 65°. This forward movement causes the sharply pointed rib tips to lacerate the body wall and proj...
Conference Paper
We investigated the morphology of the feeding apparatus in five testudinid (tortoises) and six geoemydid species using classical dissections and various histological and SEM techniques. The kinematics of the food uptake and the food transport behaviour were studied based on highspeed film recordings and high-speed cineradiography. In our experiment...
Conference Paper
Clash of the titans – Chelydra serpentina versus Chelus fimbriatus Aquatic feeding in turtles shows two possibilities of specialisations: ram feeding and suction feeding. Therefore, two exceptional representatives of each feeding lineage were studied: Chelydra serpentina and Chelus fimbriatus. The feeding kinematics of these two turtles were evalua...
Article
Full-text available
Histological and ultrastructural investigations revealed three different multicellular skin gland types in the salamandrid Pleurodeles waltl. The mucous glands are small, with one layer of secretory cells surrounding a central lumen; they produce the viscous and slippery mucus film that has various functions in amphibians. The serous glands can be...
Article
Full-text available
This study examines the kinematics and morphology of the feeding apparatus of two geoemydid chelonians, the Malayan (Amboina) box turtle (Cuora amboinensis) and the yellow-margined box turtle (Cuora flavomarginata). Both species are able to feed on land as well as in water. Feeding patterns were analysed by high-speed cinematography. The main focus...
Article
Full-text available
Scanning Electron Microscopy (SEM) revealed that the palate of Cuora amboinensis has a flat surface with keratinized and non-keratinized regions. Keratinization is reflected in disc-shaped keratinized dead cells with rough microplicae on the surface, and is concentrated close to the rhamphotheca. The surface of the non-keratinized hexagonal epithel...

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Projects

Projects (6)
Project
Plethodontids have developed “a peculiar mechanism of bite-force enhancement” in order to process their food with the jaws. They combine their atlanto-mandibular ligament and head-tucking behavior to transfer and amplify the force of cranial depression to the lower jaw to inflict a series of powerful bites on prey. This behavior could have freed the tongue from intraoral prey processing and thus licensed the tongue to solve new problems. Indeed, basal plethodontids (lungless salamanders) simply use a muscle-powered tongues to ingest food (lingual prehension) – while more derived plethodontids are known to capture prey using the most enhanced tongue-protrusion mechanisms in amphibians (i.e., ballistic tongue projection). These results support the idea that liberation of the tongue from intraoral prey processing could have licensed plethodontids to developed new tongue-based behaviors; an idea we test using high-speed X-ray imaging, anatomical investigations, and behavioral analysis.
Project
The goal of this study is to analyze the „simple“ arcuate chewing behavior of the common mudpuppy (Necturus maculosus), a neotenic salamander. We implanted 24 tantalum markers in elements of the common mud puppy's feeding apparatus and used XROMM for a complete 3D analysis of the chewing behavior. In addition, a complete analysis of the feeding behavior might be added (i.e. ingestion, transport, processing and swallowing).
Project
We used a force sensor that was connected to a BIOPACK MP100 system* and mounted on a motorized micromanipulator (DC3001R with controller MS314) to press a model tooth vertically into the samples at a constant speed to perforate their outer shell. The associated Acq Knowlegde software was used to monitor force-time curves and calculate the FPF of the various foods. We link these food perforation forces with differences in the feeding behavior of salamanders who eat these foods. *This setup is able to reliably detect forces of a few millinewtons.