Helge Hilgers

Fine structure of the dorsal lingual epithelium of Trachemys scripta elegans (Chelonia: Emydidae)

Turtles are adapted to different environments, such as freshwater, marine, and terrestrial habitats. Examination of histological and ultrastructural features of the dorsal lingual epithelium of the red‐eared turtle, Trachemys scripta elegans, and comparison of the results with those of other turtles should elucidate the relationship between the morphology of tongues as well as the fine structure of lingual epithelia and chelonian feeding mechanisms.

Three Types of Cutaneous Glands in the Skin of the Salamandrid Pleurodeles waltl. A Histological and Ultrastructural Study

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 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 very large (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 features including size, shape, cellular organization and vesicle distribution, vesicle size and vesicle shape. Both GGI and GGII are especially concentrated in body parts that are presented to an attacking predator and are hypothesized to produce repellent to poisonous substances to thwart potential aggressors. J. Morphol., 2009.

FEEDING MECHANISM OF TESTUDO HERMANNI BOETTGERI (CHELONIA, CRYPTODIRA)

Feeding of Testudo hermanni boettgeri was studied by film analysis and anatomical examination of the musculature and skeleton elements involved. Film sequences were analysed to describe the movements of food item, neck, jaws, and tongue. The feeding cycle is divided into food uptake (ingestion), followed by several transport and manipulation cycles (intraoral transport), and finally swallowing of the food (deglutition). The results show that in Testudo hermanni boettgeri the tongue is the main tool for food uptake and intraoral manipulation. The hyoid apparatus supports the floor of the mouth and is adapted to the highly movable tongue. Compared to aquatic species the hyoid is smaller, more flexible, and less ossified. Skull shape and arrangement of jaw muscles also demonstrate adaptation to terrestrial life. The jaw muscles are less developed, their insertion areas are smaller and do not extend as much caudally as in aquatic species. The organisation of the feeding mechanism in tetrapods depends on biophysical constraints imposed by the surrounding medium. In this organisation the hyolingual complex plays an important role. The tongue of terrestrial turtles tends to be larger, more muscular, more mobile, and tends to have a more complex surface than in aquatic forms. The feeding mechanism of Testudo hermanni boettgeri shows the typical situation of a turtle that is fully adjusted to terrestrial life.

Histomorphology of the Penis Bone (Baculum) in the Gray Long-Eared Bat Plecotus austriacus (Chiroptera, Vespertilionidae)

For the first time, the histomorphology of the penis bone of a bat (Plecotus austriacus) was examined in detail. From Plecotus austriacus, 14 whole penes and 11 isolated bacula were studied and compared to bacula of Plecotus auritus and Plecotus macrobullaris. The baculum was located on specimen microradiographs and in micro‐CT images in the tip of the penis. Using serial semithin sections and surface‐stained, undecalcified ground sections, the types of bone and other tissues constituting the baculum were examined by light microscopy. 3D reconstructions were generated from the serial semithin sections and from micro‐CT images. The shaft and the proximal branches of the Y‐shaped baculum form a tubular bone around a medullary cavity. Since the small diameter of this channel and the main lamellar bone around it resemble a Haversian canal, the baculum is equivalent to a single‐osteon bone. Several oblique nutrient canals enter this medullary cavity in the shaft and branches. All ends of the baculum consist predominantly of woven bone. The collagen fiber bundles of the tunica albuginea of both corpora cavernosa insert via fibrocartilage into the woven bone of the branches. Thus, the microscopic structures support the hypothesis that the baculum functions as a stiffening element in the erect penis. In this study, several microscopic imaging techniques were evaluated for displaying the microscopic structures of the baculum. Specimen microradiography, but especially micro‐CT proved to be suitable nondestructive methods for accurate and reproducible demonstration and comparison of the three‐dimensional structures of the baculum in different bat species. Anat Rec 293:1248–1258, 2010.

Correlative 3D‐imaging of Pipistrellus penis micromorphology: Validating quantitative microCT images with undecalcified serial ground section histomorphology

Detailed knowledge of histomorphology is a prerequisite for the understanding of function, variation, and development. In bats, as in other mammals, penis and baculum morphology are important in species discrimination and phylogenetic studies. In this study, nondestructive 3D‐microtomographic (microCT, µCT) images of bacula and iodine‐stained penes of Pipistrellus pipistrellus were correlated with light microscopic images from undecalcified surface‐stained ground sections of three of these penes of P. pipistrellus (1 juvenile). The results were then compared with µCT‐images of bacula of P. pygmaeus, P. hanaki, and P. nathusii. The Y‐shaped baculum in all studied Pipistrellus species has a proximal base with two club‐shaped branches, a long slender shaft, and a forked distal tip. The branches contain a medullary cavity of variable size, which tapers into a central canal of variable length in the proximal baculum shaft. Both are surrounded by a lamellar and a woven bone layer and contain fatty marrow and blood vessels. The distal shaft consists of woven bone only, without a vascular canal. The proximal ends of the branches are connected with the tunica albuginea of the corpora cavernosa via entheses. In the penis shaft, the corpus spongiosum‐surrounded urethra lies in a ventral grove of the corpora cavernosa, and continues in the glans under the baculum. The glans penis predominantly comprises an enlarged corpus spongiosum, which surrounds urethra and baculum. In the 12 studied juvenile and subadult P. pipistrellus specimens the proximal branches of the baculum were shorter and without marrow cavity, while shaft and distal tip appeared already fully developed. The present combination with light microscopic images from one species enabled a more reliable interpretation of histomorphological structures in the µCT‐images from all four Pipistrellus species. J. Morphol. 276:695–706, 2015.

Struktur- und Funktionsanalyse ophiocephaler Pedizellarien vonSphaerechinus granularis Lam.,Echinus acutus Lam. undParacentrotus lividus Lam. (Echinodermata, Echinoidea)

SummaryThe ophiocephalous pedicellariae of three adratic species of sea urchins have been investigated by the aid of scanning electron microscope regarding the structure of the skeletal ossicles and by the aid of light microscope to elucidate the function of muscles und connective tissue structures. Each valve bears a double central and 2 simple peripheric articulations. Their interactions cause synchronous movements of the 3 valves as well as they enable the peripheral gripping teeth to meet exactly whilst the jaws are closing. Beside the basic handles, which pass over each other when the valves are moving, so-called Innenbügel are arranged at the base of the central articulation of 2 valves. They bear the insertions of the 2 collagen ligaments, which connect the neck with the head of the pedicellariae, without hampering movements of jaws. In the region of the handles, the connective tissue consists of 2 collagen ligaments, which run loop-like over the edges of the handles. Position and structure allow them to increase the gripping power and to lock the articulations for a longer period without the aid of the muscles. The movements of the flexible neck, necessary for the function of the whole pedicellariae are produced by interplaying of the Mm. flexores and the connective tissue stem, which is acting like a hydroskeleton.ZusammenfassungDie ophiocephalen Pedizellarien dreier adriatischer Seeigelarten wurden hinsichtlich ihres Skelettaufbaues mit dem Rasterelektronenmikroskop, zur funktionellen Analyse der Muskulatur und des Bandapparates lichtoptisch untersucht. Jede Skelettklappe verfügt über ein doppeltes zentrales Gelenk und 2 einfachere periphere Gelenke, die nach dem Prinzip einer doppelten Dreiecksführung sowohl die Synchronbewegung der 3 Klappen als auch das präzise Ineinandergreifen der nur wenige μm großen Randzähnchen ermöglichen. Neben den bekannten basalen Bügelbildungen, die bei der Bewegung ineinandergleiten, tragen 2 Klappen sog. Innenbügel, die dem zentralen Ansatz des Bandapparates dienen. Dieser verbindet das Köpfchen, ohne dessen freie Beweglichkeit zu behindern, mit dem beweglichen Halsabschnitt. Im Bereich der Bügel ist der Bandapparat in 2 Bänder aufgelöst, die schlaufenartig diese Bügel umgreifen. Zufolge ihrer Lage und ihrer Struktur können sie einerseits die Beißwirkung verstärken, andererseits die Gelenke längere Zeit sperren ohne Dauerbelastung der Muskulatur. Die für die Funktion erforderlichen Bewegungen des Halsabschnittes erfolgen im Zusammenspiel der Mm. flexores mit dem als Hydroskelett wirksamen achsialen Bindegewebeschlauch.

MicroCT Imaging Reveals Morphometric Baculum Differences for Discriminating the Cryptic Species Pipistrellus pipistrellus and P. pygmaeus

With the recent and continuing discovery of further cryptic bat species, it is essential to find morphological species discriminating characters. Pipistrellus pipistrellus (common pipistrelle) and Pipistrellus pygmaeus (soprano pipistrelle) have been recognized as separate species since 1997, but no reliable morphological species discriminating trait has yet been found. The most commonly used morphological species discrimination traits are ‘wing vein’ pattern and shape and color of the penis, but these have not been validated on sets of genetically identified specimens. The baculum (os penis) has long been used successfully in species discrimination in bats and other mammals. In this study, we tested the reliability of the established traits and demonstrated how to reliably separate the common pipistrelle and the soprano pipistrelle by simple baculum measurements. The bacula of museum specimens of these two species and of Pipistrellus hanaki were imaged with high-resolution microCT. Several measurements were taken on the size-calibrated volume images, and their value for species discrimination was tested by discriminant analysis with leave-one-out cross validation. We showed that P. pipistrellus and P. pygmaeus specimens can be discriminated by measuring the projected length, height, and width of the baculum (n = 48; all but one classified correctly). Geometric morphometrics was used to analyze and locate variations in baculum shape. Principal component analysis of baculum variation was not sufficient to separate these species. Most of the interspecific variation in baculum shape can be found in the proximal third (the base) of the baculum, and most individual variation can be observed in lateral view, especially in the dorsoventral curve. Quantitative details of morphology are becoming more important to distinguish cryptic species and understand their phylogeographic distributions. The simple baculum measurements can be used to classify single specimens and could be taken without microCT, on a resected baculum.

Zur Feinstruktur ophiocephaler Pedizellarien von Arbacia lixula (Linné) (Echinodermata, Echinoidea)

SummaryThe stalk of the pedicellariae from Arbacia lixula was investigated by the aid of light- and electron microscope and analysed regarding to its function. It consists of a bundle parallel arranged calcite rods concentrated distally in the head of the stalk, which is of trabecular construction; toward the corona they terminate freely without forming a joint surface. Inside, between the calcite rods and also as a distinct mantle around them, there are collagenous fibers of various thickness in parallel and spiral arrangement. In the lower part of the stalk the collagenous fibers pass over more and more to the peripheric mantle, which envelops the broader base of the stalk in constant thickness. Inside of the skeleton-collagen cylinder there appears now distinct accumulation of cells; their processes are to be find at the outer surface of the calcite fibers and their nuclei are arranged in a clear layer just above the joint region. In the area between the free ends of the calcite rods and the tubercle of the corona there is a cushion built up by fine fibrils. Its special function is given by the fact, that in any case of movement of the stalk, the calcite fibers are able to dip into this cushion more or less. Concerning the innervation, the separation of a series of nerves from the basal nerve ring, their free course in the stalk and their passing to the Mm. flexores of the head of pedicellaria is described. Based on all findings a functional interpretation for the special combination of skeleton and organic fibers is given.ZusammenfassungDer Stiel der Pedizellarien von Arbacia lixula wurde lichtund elektronenoptisch untersucht und hinsichtlich seiner Funktion analysiert. Er besteht aus einem Bündel parallel angeordneter Calcitfasern, die distal von dem trabekulär aufgebauten Stielköpfchen zusammengefaßt werden; proximal enden sie frei. Zwischen den Skelettfasern im Inneren und als deutliche Ummantelung derselben finden sich parallel, sowie auch schraubig angeordnete Kollagenfasern unterschiedlicher Dicke. In den Raum zwischen den freien Enden der Calcitfasern und dem Gelenkhöcker der Corona schiebt sich ein funktionell wesentlicher Polster feiner Fibrillen, in den die Skelettfasern bei der Bewegung verschieden tief eintauchen können. Hinsichtlich der Innervation wird die Abspaltung einer Reihe von Nerven aus dem basalen Ringnerv, ihr freier Verlauf im Stiel und ihr Übertritt in die Mm. flexores des Pedizellarienköpfchens dargestellt. Aufgrund der erhobenen Befunde wird eine funktionelle Deutung dieser für Echinodermen besonderen Kombination von Skelett und organischem Fasermaterial gegeben.

Osteology and dentition of two Mediterranean Gobius species (Teleostei, Gobiidae)

Osteological examinations of the two gobiid species Gobius fallax and the recently described colour morph of G. auratus from the northern Adriatic Sea revealed interspecific conformity in most features. These closely related species only show slight trends of osteological differentiation; clear discriminating features were hardly determined also due to high intraspecific variations. Both the metapterygoid bridge to the quadrate and the tail skeleton exhibit a somewhat stronger development in G. fallax. Although the counts of teeth in jaws and pharynx show differences, the high intraspecific variation in G. fallax did not enable discrimination between the two species. G. fallax and G. auratus exhibit skeletal features, which are common and rather primitive among the Gobiinae such as a pterygiophore formula of 3‐22110, a metapterygoid bridge to the quadrate that is variable in its extension, a well‐developed connection between preopercle and symplectic, and a scapula with only the dorsal part of the foramen ossified.

Die Entwicklung ophiocephaler Pedizellarien vonSphaerechinus granularis (Echinodermata, Echinoidea)

SummaryThe development of the ophiocephalous pedicellariae ofSphaerechinus granularis was investigated by means of a continuous series of regenerating pedicellariae with the aid of a scanning electron and light microscope. The anlagen of the three valves appears in the form of isolated triradiate skeleton rudiments; the central axis arises from their center. At the deepest level, the basal plate develops from this horizontal structure, which at last forms the handle segment of the valve. Two more horizontal plates are built above this basal plate, which are supported by spool-shaped elements; around these skeletal elements the connecting collagenous fibers are arranged. Starting from the central axis, five parallel skeletal rods arise under regular ramification and arrangement; they are connected to one another by a meshwork forming the central stem (axis tube). In a similar way, the muscle baskets on both sides of the axis tube are built up, arising from the level of the first horizontal plate. As a median support of the axis tube against the horizontal plate, a vertical, perforated plate develops with the differentiation of the central articulations at its free margin. This middle segment of the valve, as well as the handle segment, proceeds in its development, while the distal, biting segment is more retarded in its increase. Both facts can be proved by function. The final differentiation of the margins of the distal valve segment with regard to the precise meeting of the gripping teeth takes place under the influence of the beginning movements of the valves. Therefore, full differentiated articulations and adequate muscle systems are necessary.Coincidently, reorganization takes place as long as the central articulations and the distal, biting valve segment are joined to a functional unit, with the muscle baskets for the Mm. adductores at both sides. In the same way, the handle segment, the superstructure of the insertions of the Mm. abductores at the outside of the valve, and the supporting structures of the distal segment of the valve all evolve into a functional unit. The primary, rather descriptive formation of a valve into a distal, middle, and handle-bearing segment gets partly lost from this point of view.This reconstruction also becomes clear by the decrease of the perforated plate structure for the benefit of a framework construction by apposition of compact material at stronger loaded zones; highly stressed structures as articulations receive a layer of polycrystalline calcite. A similar allometry, also based on functional conditions, can be seen in the three segments of the entire pedicellariae — head, neck, and stalk — because the neck, which is the essential part for the later high mobility of the head, does not start growing before the final organization of both other segments.ZusammenfassungDie Entwicklung ophiocephaler Pedizellarien beiSphaerechinus granularis wurde anhand einer kontinuierlichen Reihe von Regeneraten rasterelektronenoptisch und lichtmikroskopisch studiert. Nach Anlage der skelettogenen Grundelemente zeigt sich eine deutliche Wachstumsallometrie der 3 Klappenabschnitte, indem der Bügelabschnitt und besonders der mittlere Klappenteil in der Entwicklung gegenüber dem distalen beißenden Teil vorauseilen. Die Enddifferenzierung der Klappenränder mit der genauen Passung ihrer Zähnchen, das Einschleifen der Gelenke und die endgültige Ausgestaltung der Bügel erfolgen unter dem formenden Einfluß der beginnenden Bewegung. Die ursprüngliche deskriptive Gliederung in distalen, mittleren und bügeltragenden Abschnitt wird mehr und mehr durch funktionelle Einheiten ersetzt; gleichzeitig wird auch die anfängliche Lochplattenstruktur von einer Rahmenkonstruktion abgelöst. Eine gleichfalls funktionell begründbare Allometrie ergibt sich in der Entwicklung von Köpfchen, Hals und Stiel des gesamten Pedizellars.