I’m phD student and working as research assistant at the Department of Theoetical Biology of the University of Vienna. My research focuses on ecomorphological adaptations of lower tetrapods.
Currently, I’m working on feeding behavior in turtles, involving both oropharyngeal specialisations and biomechanical patterns. A second focus of my interest are amphibians, especially salamanders. On salamanders, I’m investigating antipredator adaptations with special emphasis on the role of the skin glands.
 

National & international cooperations:

Prof. Dr. H Plenk jr.
Department of Nuclear and Developmental Biology, Center for Anatomy and Cell Biology,
Medical University of Vienna, Austria.

Mr. Rainer Vallant
Institute of Analytical Chemistry and Radio-Chemistry, University of Innsbruck, Austria.

Mr. Günther Schultschick
Salamanderland, Kaltenleutgeben, Austria.

Institution of Cell Imaging and Ultrastructure Research, University of Vienna

Histological Lab of the “Bernhard Gottlieb” Dental School, Medical University of Vienna, Austria.

Austrian Herpetological Society (ÖGH).

Publications

Heiss E, Plenk H Jr, Weisgram J. (2008).
Functional Microanatomy of the Palatal Mucosa of the Malayan Box Turtle, Cuora amboinensis (Daudin, 1802).
The Anatomical Record Part A 291 (7): 876-885.

Abstract:
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 epithelial cells is dotted with microvilli and sometimes with cilia. Taste buds are present both in lightly keratinized and non-keratinized regions and exhibit a crater-like shape. Light microscopy shows the different tissue layers of the oral mucosa and the different epithelial structures. In keratinized regions, keratinocytes mature from basal to superficial, where they build up keratin layers of varying thickness. In non-keratinized regions, the epithelial cells are arranged in a stratified fashion, and cuboidal to cylindric cells form a superficial layer. Goblet cells appear to be diffusely distributed, but are often organized in goblet cell fields which can be folded into crypts. Taste buds consist of slender epithelial cells, exhibit the typical barrel-like shape and are specially concentrated in the anterior, praechoanal palate. This anterior concentration of taste buds is shown by kinematographic analysis to correlate with the food prehension mode in Cuora amboinensis. The lamina propria of the palatal mucosa consists of loose connective tissue with inflammatory cells between capillaries. All these structures of the oral mucosa act as a functional entity and help determine how successfully an organism adapts ecologically to the environment.

Natchev N, Heiss E, Lemell P, Stratev D, Weisgram J. (2009, in press).
Analysis of prey capture and food transport kinematics in two Asian box turtles, Cuora amboinensis and Cuora flavomarginata (Chelonia, Geoemydidae).
Zoology.

Abstract:
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 of the present study is on the terrestrial feeding strategies in both Asian box turtles, because feeding on land has probably evolved de novo within the ancestrally aquatic genus Cuora. During terrestrial feeding (analysed for both species), the initial food prehension is always done by the jaws, whereas intraoral food transport and pharyngeal packing actions are tongue-based. The food uptake modes in Cuoras differ considerably from those described for purely terrestrial turtles. Lingual food prehension is typical of all tortoises (Testudinidae), but is absent in C. amboinensis and C. flavomarginata. A previous study on Terrapene carolina shows that this emydid turtle protrudes the tongue during ingestion on land, but that the first contact with the food item occurs by the jaws. Both Asian box turtles investigated here have highly movable, fleshy tongues; nonetheless, the hyolingual complex remains permanently retracted during initial prey capture. In aquatic feeding (analysed for C. amboinensis only), the prey is captured by a fast forward strike of the head (ram feeding). As opposed to ingestion on land, in the underwater grasp the hyoid protracts prior to jaw opening. The head morphology of the investigated species differs. In contrast to the Malayan box turtle, C. flavomarginata exhibits a more complexly structured dorsal lingual epithelium, a considerable palatal vault, weaker jaw adductor muscles and a simplified trochlear complex. The differences in the hyolingual morphology reflect the kinematic patterns of the terrestrial feeding transport.

Heiss E, Natchev N, Rabanser A, Weisgram J, Hilgers H. (2009, in press).
Three types of cutaneous glands in the skin of the salamandrid Pleurodeles waltl: A histological and ultrastructural study.
J. Morphol.

Abstract:
Histological and ultrastructural investigations revealed three different multicellular skin gland types in the salamandrid Pleurodeles waltl. The mucus glands are small, with one layer of secretory cells surrounding a central lumen; they produce the viscous and slippery mucus film which has various functions in amphibians. The serous glands can be divided based on their histological and ultrastructural characters into the granular gland type I (GGI) and the granular gland type II (GGII). The first type (GGI) is moderately sized and distributed throughout the body surface, with higher concentrations in the parotoid and back regions. In contrast, the second type (GGII) is of giant dimensions (for Pleurodeles) and was found only in the tail, with highest concentration in the tail dorsum. Both granular gland types contain mainly proteinaceous materials but differ in their morphological patterns, including size, shape, cellular organisation and vesicle distribution, vesicle size and vesicle shape. Both GGI and GGII are specially concentrated in body parts that are presented to an attacking predator and produce repellent to poisonous substances to thwart potential aggressors.

Heiss E, Natchev N, Lemell P, Beisser C, Weisgram J. (2009, subm.).
Feeding and breathing functionality: a trade-off in the oropharynx of the common musk turtle Sternotherus odoratus (Chelonia, Kinosternidae).
J. Exp. Biol.

Abstract:
In tetrapods, the oropharyngeal cavity and its anatomical structures are mainly responsible for the uptake and intraoral transport of food. In this study we propose a second function of the oropharynx in the North American common musk turtle, Sternotherus odoratus. We describe the bifunctionality of the oropharynx in feeding and aquatic gas exchange, analogous to the trade-off found in some soft-shelled turtles.
Using high-speed video, we demonstrate experimentally that S. odoratus practices hydrodynamic feeding underwater but is unable – despite all efforts – to complete the feeding process on land. Scanning electron microscopy and light microscopy reveal that the reason for this inability is the small and weak tongue. Although small, the tongue bears a variety of lobe-like papillae, which wrongly could be interpreted as an adaptation for terrestrial food uptake. These papillae also largely cover the whole oropharynx, are highly vascularized and apparently play an essential role in aquatic gas exchange underwater.
 

Congresses and Meetings

Heiss, E., Plenk, H.Jr., Weisgram, J. (2007).
Structure and Function of the Palatal Oral Mucosa of the Malayan Box Turtle, Cuora amboinensis (Daudin, 1802).
Journal of Morphology 268(12):1081-1082.
(8. International Congress of Vertebrate Morphology; Paris, 16. 08 – 21. 08. 2007)