bluuebunny/crossref_metadata_2025_split huggingface dataset:
Blood Supply to the Interventricular Septum of the Heart in Rodents with Intramyocardial Coronary Arteries
Authors: Durán Ana C. , Sans‐Coma Valentín , Arqué Josep Maria , Cardo Manuel , Fernández Borja , Franco Diego 
Published: April 2010

AbstractThe blood supply to the interventricular septum of the heart was studied in a sample of 1634 specimens belonging to four rodent families, Cricetidae, Arvicolidae, Gliridae, and Muridae. Most specimens (n = 1604) were examined using a corrosion‐cast technique, while the remaining 30 were studied by histological techniques. In 1417 cases the coronary artery pattern was normal, and the interventricular septum was fundamentally supplied by one or rarely two septal arteries arising from the right and/or left coronary arteries. In 72 specimens the right and left coronary arteries were normal, while the septal artery arose from a separate ostium in the aorta, behaving as a third coronary artery. The remaining 145 animals possessed anomalies in the origin of the coronary arteries, and the septum was also principally irrigated by a septal artery. In 5 of these 145 anomalous cases the septal artery originated from a separate ostium in the aorta. In all specimens examined a less important vascularization of the septum was established through thinner penetrating vessels originating from the right and/or left coronary arteries. Existence of one or rarely two septal arteries is the most constant feature of the coronary artery arrangement in rodents with intramyocardial coronary arteries.
Ultrastructure of the Flame Bulbs and Protonephridial Capillaries of Artioposthia sp. (Platyhelminthes, Tricladida, Geoplanidae)
Authors: Rohde Klaus , Watson N. A. 
Published: April 2010

AbstractThe protonephridial terminal complex of Artioposthia is formed by one or two terminal cells, each with a nucleus located in the lateral wall of the flame bulb, and probably two proximal canal cells forming the wall of the protonephridial capillary. The weir is restricted to the proximal parts of the flame bulbs and consists of convoluted slits separated by thick cytoplasmic columns. Cross‐striated ciliary rootlets running parallel with and obliquely or transversely to the longitudinal axis of the flame bulbs strengthen the walls of the flame bulbs and, to a lesser degree, that of the capillary. Numerous cristate mitochondria are present in the terminal and proximal canal cells. Cytoplasmic processes extend from the terminal cells into the adjacent tissue, and narrow internal leptotriches extend from the cytoplasm of the terminal cells into the lumen of the flame bulbs. The wall of the capillary contains many interconnected, liquid filled spaces that communicate with the lumen of the capillary, and two septate junctions. Phylogenetic implications of the findings are discussed.
Comparative Ultrastructural Studies on the Pineal Organ of the Mexican Catfish Rhamdia laticauda Heckel, 1858 and One of its Cave‐dwelling Derivates (Pimelodidae, Teleostei)
Authors: Langecker Thomas G. , Wilkens Horst 
Published: April 2010

AbstractThe pineal organ of the epigean catfish Rhamdia laticauda and of its cave‐dwelling derivate from Cueva del Tunel in Zongolica, Mexico, was examined ultrastructurally. The pineal of the epigean form is relatively small but ultrastructurally well differentiated and characterized as a metabolically active, photoneuroendocrine organ. The outer segments of the sensory cells are composed of 32–55 very regularly arranged sacculi which are obviously functioning in photoreception. Furthermore, the presence of electron‐dense vesicles, free ribosomes, conspicuously well‐developed Golgi bodies, and large amounts of rough and smooth endoplasmic reticulum in the cytoplasm provide evidence for a secretory activity of the sensory cells. The only regressive traits in the pineal of the cave form regard the outer segments: there are few disintegrated, whorl‐like outer segments and the number of sacculi exhibits an increased variability. Compared with other morphological structures dependent on light, for example the eyes, the degree of regression is very low. It is suggested that this is due to a remaining secretory role of the sensory cells, which prevents the functionless, photoreceptive outer segments from rapid degeneration by developmental constraints.
Distribution and Ultrastructure of Ciliated Sensory Receptors in the Posterior Mantle Epithelium of Dentalium rectius (Mollusca, Scaphopoda)
Authors: Reynolds Patrick D. 
Published: April 2010

AbstractThe scaphopod mantle cavity opens posteriorly via the pavilion, a siphon‐like extension of the posterior mantle through which the respiratory currents pass. The pavilion was examined for ciliated sensory cells in Dentalium rectius Carpenter, 1865, using scanning and transmission electron micropscopy. Three types of sensory receptor were distinguished on the basis of number, length and ultrastructure of the associated cilia. Receptors with 2–5 cilia of ˜ 1.7 μm length lined the pavilion edge. A second type, possessing 1–2 cilia, ˜ 8.2 μm in length, was found throughout the internal and on part of the external surface of the pavilion. The third receptor type consisted of a rigid bundle of 16–40 cilia with a length of ˜ 14.4 μm, and was present close to the periphery and at the base of the pavilion near the entrance to the mantle cavity. The structure and distribution of these cells are similar to peripheral chemo‐ and mechanoreceptors which sample respiratory currents and the surrounding environment in other molluscs, but they may assume a greater functional significance in scaphopods due to the absence of an osphradium in this class.
Phylogenetic Significance of the Burgess Shale Crustacean Canadaspis
Authors: Briggs Derek E. G. 
Published: April 2010

AbstractThe crustaceans, like the other major living groups of arthropods, have a long evolutionary history. The earliest examples occur in the Cambrian, and fossils of this age are a critical source of evidence of relationships both within the Crustacea, and between the Crustacea and other major arthropod groups. Canadaspis perfecta, from the Middle Cambrian Burgess Shale, is important as one of the oldest well‐documented crustaceans. The evidence for reconstructing its remarkable combination of primitive and derived characters is reviewed, and its possible phylogenetic significance re‐assessed.
Not Yet Proven Crustacea: the Thylacocephala
Authors: Rolfe W. D. Ian 
Published: April 2010

AbstractThe Thylacocephala is a recently recognized extinct group of uncertain, but probably crustacean, affinity, comprising fossils formerly assigned to many different crustacean groups. Key characters are three anterior pairs of subchelate limbs; at least 8 pairs of radiating gills, situated between the trunk and carapace, the most posterior gill lying subhorizontally; and the large posteriorly tapering battery of 8(–?20) elongated limb protopods with tenuous distal filaments. Thylacocephala bear huge anterior structures, variously identified as compound eyes or as a ‘cephalic sac’. Microsclerites borne on this structure may be external, perhaps setae, but need not imply affinity with cirripedes as has been argued. Internal microsclerites have been compared with crystalline cones of a compound eye. More detailed study of well‐preserved material is required to resolve the nature of these microsclerites, to elucidate details of appendages, to locate antennae, and to ascertain limb homologies. Until that work is done, affinities of the Thylacocephala must remain uncertain as must the group's relevance to evolution of Crustacea. Such recent recognition of a distinctive functional model system (Dahl, E. 1976. Zoologica Scripta 5: 163–166) which persisted for at least 340 million years, shows the fossil record still has much to contribute to understanding the pattern of arthropod evolution.
Reflections on the Phylogenetic Position of the Cephalocarida
Authors: Hessler Robert R. 
Published: April 2010

AbstractThis essay re‐evaluates the phylogenetic position of the Cephalocarida in the light of the recently discovered Orsten (Upper Cambrian) crustaceans, the living Remipedia, and new interpretation of the Paleozoic ‘trilobitomorphs’. The Orsten crustaceans reinforce the belief that cephalocarid external morphology is primitive, except to show that the early crustacean trunk limb was almost surely biramous. The epipod appears to be a synapomorphy of the Cephalocarida, Branchiopoda and Malacostraca, thus justifying the existence of the Thoracopoda, which is coequal to the Maxillopoda and Remipedia. External morphology of the Remipedia is too specialized to support the hypothesis that it approximates that of the urcrustacean. Crustaceans and chelicerates are still best regarded as subgroups of the Schizoramia.
Calcification of Cartilage from the Lamprey Petromyzon marinus (L.) in vitro
Authors: Langille Robert M. , Hall Brian K. 
Published: April 2010

Abstract Adult and larval lamprey cartilage, normally unmineralized, was cultured in a medium meta‐stable for hydroxyapatite for periods of up to 12 days at 20, 30 or 37°C. Histochemical analysis revealed a temperature‐dependent increase over time in calcium phosphate incorporation into the extracellular matrix (ECM) of adult cartilage concomitant with the incorporation of calcium as detected by gravimetric and radioisotopic methods. Ultrastructural analysis revealed the presence of ECM dense bodies (40 nm average) containing crystalline material which increased in number with increased mineral incorporation but were absent from control cartilage. Additionally, electron‐dense particles (15–20 nm) found in close association with the ECM fibrils in some regions of mineralized cartilage may represent sites of amorphous calcium phosphate. Larval cartilage incorporated much less calcium, less uniformly over time than did adult cartilage. Histochemical and ultrastructural analysis revealed that calcium had accumulated in the chondrocytes instead of the ECM and this proved detrimental, leading to the death of the cells.The discovery that adult lamprey cartilage calcifies in vitro under appropriate conditions, suggests that petromyzonids, or their direct agnathan ancestors, may have possessed mineralized skeletons and that this ability is ‘repressed’ in extant lampreys owing primarily to the environment they inhabit.
Regeneration in Gastrotricha—I. Light Microscopical Observations on the Regeneration in Turbanella sp.
Authors: Manylov Oleg G. 
Published: April 2010

AbstractFor the first time, the phenomenon of regeneration is reported for the phylum Gastrotricha. Adult specimens of Turbanella sp. were transected transversely and events of regeneration were observed on the light microscopical level. In both anterior and posterior fragments the wound closure was completed I day after the operation, and in 3 days the epidermis was restored entirely. The dorsal commissure of the Y‐organ was rebuilt soon after wound closure. In anterior fragments cut at any level of the intestine, caudal adhesive tubes were formed anew, following the species‐specific pattern. In posterior fragments, and in both fragments if transected at a pharynx level, regeneration resulted in a complete wound healing, with no new adhesive tubes being observed.
Spermatozoon Ultrastructure in Two Species of Amphibolus (Eutardigrada, Eohypsibiidae)
Authors: Rebecchi Lorena , Guidi Alessandra 
Published: April 2010

AbstractWe examined the ultrastructure of the spermatozoa from two species of eutardigrades, gonochoristic Amphibolus volubilis and hermaphroditic A. weglarskae, by scanning and transmission electron microscopy. The gametes from the two species were morphologically quite similar, each consisting of a short head, neck and tail. The head included a conic, corkscrew‐shaped, bilayered acrosome and a cylindrical nucleus with condensed chromatin. The nucleus is surrounded by cytoplasm organized in ovoid elements with an electron‐dense core. The neck is very simple, containing a centriole and unmodified mitochondria. The flagellum contains a 9+2 axoneme and terminates in a tuft of between eight and 10 microtubules. The spermatozoa of Amphibolus, like those of the other eutardigrades, are of the modified type, but nonetheless maintain some primitive aspects of the gametes from heterotardigrades.
Similarities in Form and Developmental Sequence for Three Larval Shell Muscles in Nudibranch Gastropods
Authors: Page Louise R. 
Published: April 2010

AbstractShell‐anchored muscles that extend into the cephalopodium of five species of planktotrophic nudibranch larvae were studied by ultrastructural examination of sequential larval developmental stages. All species, regardless of larval shell type (inflated or non‐inflated), showed a similar basic pattern of shell muscles. The larval retractor muscle (LRM) differentiates prior to hatching and its fibres insert on epithelia of the velum, apical plate, stomodeal region, or mantle fold. Many fibres also connect with subepithelial intrinsic muscles of the cephalopodium. Most but not all LRM fibres Project to left‐sided targets and are innervated from the left cerebral ganglion. Two pedal muscles, which are innervated from the pedal ganglia, differentiate during the post‐hatching larval stage and both insert primarily on pedal epithelium attached to the operculum. The left pedal muscle is anchored to the shell immediately adjacent to the attachment plaque of the LRM and consists of basal and distal tiers of muscle cells. The right pedal muscle arises on the ventral rim of the shell aperture and consists of a single tier of muscle cells. Ontogenic changes in larval retraction behaviour correlate with developmental change in the muscle effectors. Although some interspecific differences were noted, the presence of a common ground plan for larval shell muscles in these five species contrasts with previous indications of marked variability for nudibranch larval shell muscles.
On the Innervation and Homologues of the Anterior End Appendages of the Eunicea (Polychaeta), with a Tentative Outline of the Fundamental Constitution of the Cephalic Nervous System of the Polychaetes
Authors: Orrhage Lars 
Published: April 2010

AbstractEarlier papers dealing with the architecture of the cephalic nervous system of the Eunicea were studied. Thereby, a re‐investigation appeared necessary: the existing literature proved insufficient for detailed comparisons with other polychaete families and many earlier statements and conclusions turned out to be quite contradictory, especially as concerns the homologues of the anterior end appendages. In the present paper, the microanatomy of the brain and the innervation of, inter alia, the antennae, the nuchal organs and the alimentary canal of Hyalinoecia tubicola, Nothria conchylega, Eunice norvegica and E. pennata are described. The results are summarized in schematic diagrams and tables and compared with corresponding observations in other polychaete families. Thereby, some earlier opinions about the morphological value of the cephalic appendages of the Eunicea are strengthened while others are rejected. On the basis of the present observations and earlier results arrived at by the present author, and as an object for future discussion and criticism, a diagram of the fundamental constitution of the cephalic nervous system of the Polychaeta is tentatively outlined.
Immunohistochemical Localization of Laminin and Cytokeratin in Embryonic Alligator Gonads
Authors: Smith Craig A. , Joss Jean M. P. 
Published: April 2010

AbstractGonadal sex differentiation is temperature‐dependent in Alligator mississippiensis; testis differentiation occurs in embryos incubated at 33°C and ovary differentiation occurs in embryos incubated at 30°C. Laminin and cytokeratin were examined immunohistochemically in the gonads of alligator embryos incubated at these temperatures. The aim of this study was to determine whether these structural proteins show the same sex‐specific expression patterns reported for mammalian embryos, and to assess their usefulness as early markers of gonadal differentiation in species with temperature‐dependent sex determination. Laminin delineated enlarged seminiferous cords in differentiating testes from developmental stage 23 to hatching. Laminin distribution was more diffuse and revealed smaller cords of cells in differentiating ovaries. Cytokeratin was also detected in developing gonads of both sexes. Cytokeratin became concentrated in the basal cytoplasm of differentiating Sertoli cells in developing testes. In developing ovaries, prefollicular cells of the ovarian cortex and cell cords in the medulla stained strongly for cytokeratin. Cytokeratin did not show the same basal distribution in female medullary cord cells as seen in the Sertoli cells of testes, however. These sex‐specific patterns of laminin and cytokeratin distribution in embryonic alligator gonads may serve as early markers of sexual differentiation.
Ontogenetic Torsion and Protoconch Form in the Archaeogastropod Haliotis kamtschatkana: Evolutionary Implications
Authors: Page L. R. 
Published: April 2010

AbstractOntogenetic torsion in archaeogastropods has strongly influenced theories about early gastropod evolution, but the seminal studies by Crofts (1937, 1955) remain the major source of information about tissue movements during this developmental process. Computer‐generated reconstructions of histological sections indicate that the cephalopodium of Haliotis kamtschatkanaJonas, 1845 rotates by a full 180° relative to the shell and visceral lobe during the first quarter of pre‐metamorphic development. However, a portion of pallial epithelium, including some of the shell field, accompanies the rotating cephalopodium; a process facilitated by detachment of the pallium from the apertural rim of the protoconch. Transmission electron microscopy indicates that a tract of the larval retractor muscle, which Crofts (1955) implicated in the mechanism of torsion, inserts on both pedal andpallial cells. A deep invagination of shell field epithelium is a major focus of rotational torque. As a result of pallial deformation during cephalopodial rotation, the anus and gill rudiment are restricted to the right half of the larval body for 2 days after cephalopodial rotation by 180° has been completed. Scanning and transmission electron microscopy indicate that grooves in the lateral flanks of the protoconch correspond to the deep invagination of shell field epithelium. The grooves are not created by a coiling type of accrelionary shell growth or by flexion of the protoconch. A calcareous shelf is secondarily added to the periostracal template of the protoconch along its visceral apertural rim. Morphogenetic movements during ontogenetic torsion in this species are more complex than a simple rotation between cephalopodium and visceropallium and the protoconch shows no evidence of exogastric coiling. © 1997 Published by Elsevier Science Ltd on behalf of The Royal Swedish Academy of Sciences.
The Lateral Line System of Hagfishes (Craniata: Myxinoidea)
Authors: Braun Christopher B. , Northcutt R. Glenn 
Published: April 2010

AbstractThe morphology of the peripheral lateral line system in Eptatretus stoutiiis described using a combination of electron microscopical, histological and immunocytochemical techniques. The epidermis and cranial nerves of Myxine glutinosawere also examined for evidence of a lateral line system. Together with results previously published by other researchers, we conclude that most or all eptatretid hagfish possess a lateral line system composed of shallow trenches, or grooves, lined with a single class of flask‐shaped receptive cells. No species of myxinid hagfish has been shown to possess any component of this system. Three groups of lateral line grooves are present in eptatretids: preoptic, dorsal postoptic, and ventral postoptic groups. The preoptic grooves are innervated by a single pair of ganglionated cranial nerves and the two postoptic series of grooves are innervated by a pair of cranial nerves which each possess two ganglia, possibly as a result of fusion of two pairs of ganglionated nerves. Morphometric analysis indicates that these grooves continue to grow throughout life and that the variability in the distribution of grooves between animals may result from developmental instability in lateral line ontogeny. The morphology of the receptive organs is compared to neuromasts of the vertebrate lateral line system and ciliated receptor cells of other chordates. The morphology of hagfish lateral line receptors may represent the primitive condition for craniate lateral line organs, or more likely, they are highly derived as a result of regressive evolution. © 1997 The Royal Swedish Academy of Sciences. Published by Elsevier Science Ltd.
The Embryonic and Larval Development of Polypterus senegalusCuvier, 1829: its Staging with Reference to External and Skeletal Features, Behaviour and Locomotory Habits
Authors: Bartsch Peter , Gemballa Sven , Piotrowski Tatjana 
Published: April 2010

AbstractThe embryonic and larval development of the Polypteriformes, the presumed sister group of all other living actinopterygians, is poorly known. The main reason is the scarcity of successful breedings in captivity and therefore the lack of developmental series of any one polypterid species. A series of five successful breedings of P. senegalusnow makes it possible to define developmental stages of this species based on numerous closely timed specimens. The staging given here focuses on external embryonic and larval features: epidermal surface structures documented by SEM, colour pattern, development of fins and squamation, larval feeding and locomotory behaviour. The development of P. senegalusis characterized by a long free embryonic phase. Suction feeding is performed from the beginning of larval life (apterolarval phase). The pectoral fins start to become employed for slow locomotion and as supportive structures at around the same time. Olfactorily guided prey capture, however, is observed later in the pterolarval phase. Quantitative kinematic data also demonstrate a change in the mode of undulatory locomotion during this phase. Sustained axial undulation becomes confined to the posterior abdominal and caudal region of the body. At about the same time the paraxial high frequency undulation of the pectoral fin fold is replaced by the characteristic propeller‐like movement of much greater amplitude and wavelength. Surfacing for aerial breathing is not seen before a marked change in colouration has taken place at the beginning of the juvenile period. The external gills slowly become reduced during this period. The definitions of larval and juvenile stages given here may advance understanding of developmental processes in the ontogeny of these primitive actinopterygians, and may serve as a tool for comparison with the ontogeny of Tetrapoda and Dipnoi, as well as to that of some “primitive” groups of Actinopterygii. Judging from its distribution among extant taxa, embryonic and larval ciliation is a character that most probably belongs to the grundplan‡ of Osteognathostomata. Phylogenetic evaluation is not so clear for the two other prominent embryonic and larval specializations found in Polypterus: upper labial attachment glands and opercular external gills. © 1997 The Royal Swedish Academy of Sciences. Published by Elsevier Science Ltd.