Entity

Time filter

Source Type

Bad Münster am Stein-Ebernburg, Germany

Greven H.,Heinrich Heine University Dusseldorf | Richter H.,Tiestestr. 22 | Clemen G.,Doornbeckeweg 17
Vertebrate Zoology | Year: 2013

Tongue development in several developmental stages of the metamorphosing newt Hynobius leechi (Hynobiidae) and the paedomorphic Ambystoma mexicanum (Ambystomatidae) before and after artificially induced metamorphosis was studied by light microscopy (LM) and scanning electron microscopy (SEM). In H. leechi the anlage of the glandular field (lingual glands) of the secondary tongue appears under the free tip of the primary tongue and is clearly seen in late larvae (developmental stage approx. 65). The epithelium of the primary tongue is stratified and composed of epithelial cells, AB-positive goblet cells, some superficial ciliated cells, very few Leydig cells and typical taste buds. Later more or less radially arranged tubular glands (lingual glands) develop in the anterior portion of the prospective secondary tongue, which open in furrows lined in their upper region by the surface epithelium ("neck portion"). Fully developed glands are variously long, moderately branched and contain columnar secretory cells that are preferably AB-positive in their upper region, but AB- and PAS-negative in their terminal portions. Posteriorly the tubular glands become shorter in favour of the neck portion and then are abruptly replaced by a heavily ciliated area containing indentations of the epithelium interspersed with numerous goblet cells (crypts). This zone is considered as a modified remnant of the former primary tongue. Formation of the secondary tongue, often described as "fusion" of the glandular field with the primary tongue, is considered as a process levelling the free, probably regressive end of the primary tongue and the posterior part of the growing glandular field. The development of the secondary tongue of metamorphosing A. mexicanum follows the same pattern. However, the putative anlage of lingual glands in semiadult paedomorphic specimens may be considered as a further character indicating partial metamorphosis in this species. In the transformed axolotl we demonstrate the secondary tongue with lingual glands, epithelial folds with noticeable numbers of AB-PAS-positive goblet cells at the lower surface of the free tip of the secondary tongue, and, contrary to H. leechi, tubular glands immediately behind the dentary. © 2013 Senckenberg Gesellschaft für Naturforschung.


Clemen G.,Doornbeckeweg 17 | Greven H.,Heinrich Heine University Dusseldorf
Vertebrate Zoology | Year: 2013

Schematic drawings as well as some cleared and stained preparations of the upper jaw and the palate (mouth roof) of larval (before and during metamorphosis) and transformed specimens of the larviparous Salamandra salamandra are presented to illustrate changes especially of the palate through metamorphosis. We distinguished seven stages ranging from early larvae until fully transformed specimens by using characters easily to see in preserved and anesthetized living specimens by means of a dissection microscope at various magnifications and reflected light. Distinctive characters for classification were growth of the maxillae, the anterolateral expansions and posterior outgrowths (vomerine bar) of the vomeres, complete degradation of both, the bony "bridge" connecting the pterygoid, and the palatine and the palatine itself. Larger specimens (length of ca. ≥ 3 cm) can be inspected non-invasively by fixing them in a simple holder. As we used elements that are always present in metamorphic salamanders either exclusively in their larvae (palatine) or in larvae as well as in transformed specimens (premaxillae, maxillae and vomeres), the classification proposed herein appears to be applicable not only to the type form of S. salamandra, but also to other Salamandridae and, appropriately modified, very probably even to urodele taxa that may considerably differ for instance in the shape of the vomeres and dentition. Obviously metamorphic Urodela appear to be constrained by a largely similar developmental sequence with regard of growth and remodelling of the palate, which may be categorized in a standard manner. © 2013 Senckenberg Gesellschaft für Naturforschung.


Clemen G.,Doornbeckeweg 17 | Greven H.,Heinrich Heine University Dusseldorf
Vertebrate Zoology | Year: 2015

We describe the organisation of the palate in a specimen of the Mexican axolotl (Ambystoma mexicanum), which spontaneously started metamorphosis in an advanced age after several breeding cycles, but had not yet completed transformation at an age of > 7 years when it was euthanized. The palate shows a mosaic of paedomorphic (absence of the edentate vomerine plate, monocuspid pedicellate teeth) and transformed traits (separation of palatine and pterygoid, fusion of the vomer and anterior parts of the palatine (vomeropalatinum), bicuspid teeth at least on the upper jaw). The vomeropalatinum has a broad pars palatina along its inner side (typical for paedomorpic specimens). We think that the transformation process has started after the specimen has reached the full paedomorphic status. © Senckenberg Gesellschaft für Naturforschung, 2015.


Greven H.,Heinrich Heine University Dusseldorf | Van De Kamp T.,Karlsruhe Institute of Technology | Dos Santos Rolo T.,Karlsruhe Institute of Technology | Baumbach T.,Karlsruhe Institute of Technology | Clemen G.,Doornbeckeweg 17
Vertebrate Zoology | Year: 2015

A study on the cranial morphology, especially on the tooth bearing (dental) systems of several preserved developmental stages (from early premetamorphic larvae, in which most skull elements were already present and ossified or ossified in part, to transformed adult) of the smooth newt Lissotriton vulgaris (Salamandridae) was undertaken. We used μCT (to visualize the ossified elements in general and their relationships to each other) and an overall Alizarinred staining (to at best visualize teeth, replacement teeth, tooth buds and, after removing the oral mucosa, the course of dental laminae). Specimens cleared and stained with Alzarinred and Alcianblue were shown to be less suitable for our questions. In one case we used histological sections to follow the course of dental laminae, and in a second case scanning electron microscopy to show the structure of teeth in detail. The general sequence, growth, and changes of the bony elements including the "dental systems", especially around metamorphosis, known from several other salamandrids are largely confirmed. Concerning the "tooth systems", metamorphic events include the late appearance of the maxillae, resorption of the coronoids and palatines including their tooth-patches, remodelling of the vomer, i.e. resorption of the vomerine larval tooth-patch, formation of the edentate vomerine plate, and outgrowth of the monstichously dentate vomerine bar (typical for salamandrids). We show evidence that the larval vomer is not completey resorbed and that, unlike what has been described for Salamandra salamandra, the development of the vomerine bar is probably preceded by a shift of the dental lamina towards the middle of the palate, leaving a broad area between larval vomer and dental lamina. We hypothesize that the connective tissue in this area ossifies later and extends posteriorly forming the vomerine bar. It is noteworthy that in nearly all larvae vomer and intact pterygopalatinum were very close together either on one side or on both sides leading in overwintered larvae to the fusion of the vomer and the palatinal portion of the pterygopalatinum, primarily on one side. The zone of fusion is always characterized by a buccal notch. We think that in L. vulgaris the formation of "vomeropterygopalatina" is supported by the close proximity of the two bones and that these bones may fuse due to an imbalance between differentiation- and growth rate (indirectly caused by low temperatures). Approximation and especially fusion of the two bones correspond with the extension of the vomerine dental lamina into the area of the palatine, which temporally provides the latter with teeth. Overwintered larvae show further deviations concerning growth and differentiation of the mouth roof, which can be also interpreted as signs of delayed metamorphosis. They retain, for example, a largely intact dentate palatine, but with some regression of its tooth-patch, while the larval vomer is enlarged anteriorly and posteriorly and its number of teeth has increased; and the largely intact pterygopalatinal bony bridge. Further, maxillae begin to ossify. All larvae obviously have reached a late premetamorphic larval stage before the delay has started.

Discover hidden collaborations