Characterisation of chitin in the cuticle of a velvet worm (Onychophora)

*Kaya, Murat ( Aksaray, Yazar ) *Baran, Talat ( Aksaray, Yazar )We characterize the trunk cuticle of velvet worms of the Peripatoides novaezealandiae-group (Onychophora) using SEM, TEM, Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA). TEM and SEM revealed a relatively uniform organization of the delicate cuticle that is covered by numerous bristled and nonbristled papillae with ribbed scales arranged in transverse rows. The cuticle consists of a very thin multilayered epicuticle of varying appearance followed by the largely fibrous procuticle. The irregularly arranged nanofibres of isolated cuticular chitin seen by SEM are considered as bundles of chitin fibres. FT-IR and TGA showed that the chitin is of the α-type. This confirms and broadens the single previous study in which the presence of α-chitin in a velvet worm was demonstrated with a single analysis (X-ray diffraction)...

Parental investment by skin feeding in a caecilian amphibian

Although the initial growth and development of most multicellular animals depends on the provision of yolk, there are many varied contrivances by which animals provide additional or alternative investment in their offspring(1). Providing offspring with additional nutrition should be favoured by natural selection when the consequent increased fitness of the young offsets any corresponding reduction in fecundity(2). Alternative forms of nutrition may allow parents to delay and potentially redirect their investment. Here we report a remarkable form of parental care and mechanism of parent-offspring nutrient transfer in a caecilian amphibian. Boulengerula taitanus is a direct-developing, oviparous caecilian(3), the skin of which is transformed in brooding females to provide a rich supply of nutrients for the developing offspring. Young animals are equipped with a specialized dentition, which they use to peel and eat the outer layer of their mother's modified skin. This new form of parental care provides a plausible intermediate stage in the evolution of viviparity in caecilians. At independence, offspring of viviparous and of oviparous dermatotrophic caecilians are relatively large despite being provided with relatively little yolk. The specialized dentition of skin-feeding (dermatophagous) caecilians may constitute a pre-adaptation to the fetal feeding on the oviduct lining of viviparous caecilians.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62957/1/nature04403.pd

Sex dimorphic dentition and notes on the skull and hypbranchium in the hynobiid salamander Pachyhynobius shangchengensis FEI, QU & WU, 1983 (Urodela: Amphibia)

A noticeable sex-dimorphic dentition is described in the hynobiid salamander Pachyhynobius shangchengensis. In the upper and lower jaw, the male possesses pedicellate teeth with a chisel- or spearhead-like crown, i.e. secondary (labial) cusps of teeth are largely reduced, whereas the primary (lingual) cusps are fl attened antero-posteriorly and exhibit sharp edges. In contrast, females have pedicellate, somewhat fl attened teeth more variable in shape, but with small bladed labial and large bladed lingual cusps. Vomeres of both sexes bear typical bicuspid, pedicellate teeth. Skulls including the hyobranchium are largely ossifi ed with some minor differences between males and females. However, females appear to lack the pars hypohyalis in the hyobranchial apparatus

Remodelling of the palate: an additional tool to classify larval salamandrids through metamorphosis

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

Organisation of the palate in a spontaneously transforming Mexican axolotl (Ambystoma mexicanum): a case report

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

Long-term effects of arrested metamorphosis on dental systems in Salamandra salamandra (Salamandridae: Urodela)

We describe the dental systems of six larvae of Salamandra salamandra hypophysectomized in 1976 under an earlier project to arrest metamorphosis. Larvae cover roughly three developmental stages from early (intrauterine) larval stage to early metamorphosis. Animals survived surgery and lived up to 16 months until fixation. One specimen was studied by histological serial sections. In the period until fixation larvae grew from approximately 3 cm to 7 cm in length (dependent on the developmental stage before surgery) retaining their larval appearance. Changes in the dental systems depended on the stage the larvae had reached before surgery. Generally, after surgery some traits had started or continued development, such as appearance of maxillae as well as resorption of the palatinal tooth patches and the coronoids in the youngest larva examined, whereas other traits had been largely retained and even continued to grow (e. g. larval dentate vomers). In three larvae, the anterior part of the palatines was covered by the posterior margin of the vomer giving the impression of a ‘vomeropterygopalatinum’, known from some newts as temporary fusion of vomer and palatine in consequence of a delayed metamorphosis. However, in the Salamandra-larvae both elements appeared to be connected syndesmotically rather than to be fused by bone tissue The oldest larva (metamorphic stage IV, approximately at the onset of metamorphosis), had lost the palatinal portion of pterygopalatina and had reduced the tooth patches of the vomers to a single row, but outgrowth of the vomerine bar had not taken place

Early tooth transformation in the paedomorphic Hellbender Cryptobranchus alleganiensis (DAUDIN, 1803) (Amphibia: Urodela)

Dentition of the upper and lower jaws and the palate of three larvae of different sizes (29 mm, 47 mm, 53 mm long) and one adult specimen of the paedomorphic Cryptobranchus alleganiensis is described. The 29 mm larvae had ossifi ed, but not fully developed premaxillae and vomeres, partly ossifi ed incomplete palatines, dentaries and still developing coronoids. Teeth were present only on the premaxillae, dentaries and vomeres, but were still not ankylosed to the bones; they were monocuspid and non-pedicellate. However, in the 47 mm larva teeth on all dentigerous bones were bicuspid and pedicellate as typical for urodele teeth after metamorphosis. Thus, paedomorphosis infl uences dentition already in a relatively early time in ontogeny in C. alleganiensis. Such heterochronous effects on dentition obviously occur in different degrees within paedomorphic Urodela and deserve closer attention. Presently, however, knowledge of them is still fragmentary. With the exception of the palatines and the coronoids, which were toothless, praemaxillae, vomeres and dentaries bore a single row of established teeth. Course and number of dental laminae was consistent with the conditions found in other Urodela (a continuous dental lamina in the upper jaw arcade; a discontinuous in the lower jaw arcade and two vomerine dental laminae). However, in contrast to other Urodela we found no signs of dental laminae accompanying the coronoids and the palatines, which explains the total absence of teeth on these bones

The "nasal barbel" of the halfbeak Dermogenys pusilla (Teleostei: Zenarchopteridae) - an organ with dual function

Members of the taxon Zenarchopteridae (Beloniformes) possess external paired olfactory organs each consisting of a small cone-like papillae also called nasal barbel. We examined the structure of these barbels in the viviparous halfbeak Dermogenys pusilla using scanning (SEM) and transmission electron microscopy (TEM). Nasal barbels are covered by a typical epidermis characterized by ridged surface cells. Further, the epidermis contains goblet cells and small taste buds. The epidermis is interspersed with small depressions or pits (sensory islets) which contain the olfactory epithelium. Typically, taste buds consist of spindle-shaped dark cells with numerous apical microvilli, light cells with a thick microvillus each, basal cells and a rich nerve fiber plexus between receptor and basal cells. The olfactory epithelium at least contains two types of receptor cells, i.e. ciliated cells with a strikingly variable microtubular pattern and microvillous cells, and supporting and basal cells. An olfactory organ with an open groove and an elongated papilla is considered as synapomorphy of the Beloniformes (does not hold for the Adrianichthyoidei). Comparison of these olfactory organs suggests that D. pusilla and very probably all Zenarchopteridae may have the most uniform and least elaborated olfactory organs

Histology and fine structure of epidermal papillomas in the Alpine newt Ichthyosaura alpestris (Urodela: Salamandridae)

Epidermal papillomas of alpine newts (Ichthyosaura alpestris) collected in the field (Germany, Austria) were studied by histology (LM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Papillomas were found on the head, the trunk and the tail, with the most and largest on the head of males. They protruded beyond the body surface exhibiting an appearance like a cauliflower. The head of one specimen studied by SEM had a large papilloma and was densely populated with bacteria, fungi and sessile ciliates. The surface of papillomas was covered either by stratum corneum cells, or by deeper cell layers that may be exposed by injuries. Histology revealed that papillomas consisted of compact bulbous extensions that were deeply embedded into the dermis and separated from each other by small septa (papillae) of connective tissue. Bulbs were distinctly demarcated by a thin basal lamella that was continuous with the basal lamella of the adjacent non-altered epidermis. An invasion of papilloma-cells through the basal lamella in the underlying connective tissue could not be unequivocally demonstrated; only once we found an area by TEM, which could be interpreted in this way. Bulbs may have two types of cavities or cysts. One type contained masses of keratinized cell layers, the other appeared either largely empty, or contained cellular debris and/or PAS-positive substances discharged by secretory cells lining the cyst. Tumor cells within a bulb are offen arranged in clusters or nests. Generally, cells appeared relatively undifferentiated having large euchromatic or heterochromatic nuclei, prominent nucleoli, and a moderate amount of cell organelles. Also the amount of tonofilamets and number and size desmosomes (macuale adhaerentes) seemed to be reduced. Virus-like particles were found neither in the cytoplasm nor in the nucleus. Compared to the unaltered epidermis, in which no mitoses were seen, mitotic cells occurred in all papillomas examined. In addition, the neoplastic tissue always contained macrophages and further ‘leucocytes’, but necrotic areas were rare. Dermal papillae separating the bulbs from each other and the dermal tissue immediately beneath the basal lamina of papillomas contained a high number of cells (e.g., fibroblasts and cells of the immune system)

Coxal organs of chilopoda : the exocrine glands in Lithobius forficatus

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