bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metamorphosis of the marine bryozoan Membranipora membranacea: An ultrastructural study of rapid morphogenetic movements
Authors: Stricker Stephen A. 
Published: February 2005

AbstractThe colonial marine bryozoan Membranipora membranacea produces a planktotrophic cyphonautes larva that is encased by a triangular bivalved shell. Following a relatively long free‐swimming phase, the cyphonautes larva settles and undergoes a dramatic metamorphosis to become the sessile progenitor of the colony, referred to as the ancestrula. This paper examines the initial morphogenetic movements of metamorphosis that transform the cyphonautes larva into an incipient ancestrula. At the onset of metamorphosis, contractions of the striated median muscles situated along the anterior and posterior margins of the larva cause a retraction of the larval apical organ and a centripetal movement of the anterior and posterior ends of the larva. Concurrently, the ciliated corona at the base of the larva is pulled within the shell by contractions of the striated lateral muscles. As the larva assumes a more spherical shape, the posterior margins of the shell are spread apart, and the internal sac is everted. Eversion of the sac is apparently achieved by contractions of the lateral muscles that cause a buckling of the shell in the apical‐basal direction. The neck region of the everted sac secretes adhesive granules that attach the larva to the substratum. Subsequently, contractions of the nonstriated sac muscles fold the valves of the shell over each other and draw the larva toward the substratum. The initial events of metamorphosis that culminate in the attachment and flattening of the larva are completed in 10–15 seconds. In the subsequent few minutes, the lateral edges of the everted sac fuse with the neighboring margins of the aboral epithelium underlying the shell and thus form the fully sealed body wall of the incipient ancestrula.
Morphology of the exocrine pancreas of the Southern Hemisphere lamprey, Geotria australis, and changes during metamorphosis
Authors: Hilliard R. W. , Potter I. C. 
Published: February 2005

AbstractThe distribution and histology of zymogen cells and the activity of digestive enzymes have been examined in the alimentary canal of larval, metamorphosing (stages 1–7), and adult Geotria australis (Geotriidae). Comparisons of the arrangement of the larval and adult zymogen cells are made with those observed in Mordacia mordax, a representative of the other Southern Hemisphere lamprey family (Mordaciidae), and with those reported elsewhere for holarctic lampreys (Petromyzontidae). In larval G. australis, epithelial zymogen cells are mainly restricted to the prominent pair of tubular diverticula which project forward from the oesophageal/intestinal junction. By contrast, zymogen cells of adults are present in the epithelium of both the anterior intestine and the intestinal caecum, a structure located at the new and more anterior oesophageal/intestinal junction which forms during metamorphosis. Amylolytic activity was greater in the larval divrticula than in the adult caecum, whereas the reverse was true for tryptic activity. This feature presumably reflects the high dietary contribution made by detritus and algae during the filter‐feeding larval phase and by host muscle tissue during the predatory adult phase. The high tryptic activity in the caecum must promote the early breakdown of host tissue and thereby facilitate the digestion of lipids in the anterior intestine where lipolytic activity is high. At the commencement of metamorphosis, digestive activity and the number of zymogen cells declines markedly. By stage 4 the intestine has rotated anticlockwise almost 360°; the two larval diverticula have disappeared; and the new exocrine caecum of the adult has started to develop from a forward proliferation of intestinal mucosal cells. While the exocrine pancreatic tissue of larval M. mordax is unique amongst lampreys in its location within a single, large diverticulum containing an extensive network of mucosal folds, that of the adult is found in the same position as in G. australis and holarctic lampreys.
The morphogenesis of molluscan shells: A mathematical account using biological parameters
Authors: Løvtrup Søren , Løvtrup Michael 
Published: February 2005

AbstractIn attempts to account mathematically for the morphogenesis of biological structures it is important that the parameters chosen for the purpose should be “biological,” that is, they should refer directly to the growth processes through which the structure is formed.Molluscan shells are formed by accretional growth at the mantle edge, and the parameters used for the mathematical description of their formation should therefore refer to events taking place there.In the best of previous attempts to solve this problem, two out of three form parameters have met with this demand, but it was not possible to eliminate β, half the apical angle of the cone on which lie the centers of successive whorls.It is shown here that β may be eliminated for many forms of molluscan shells, and when this is not the case β may indeed be referred to processes taking place at the mantle edge.
Reproduction in the mexican leaf frog, Pachymedusa dacnicolor. IV. Spermatogenesis: A light and ultrasonic study
Authors: Rastogi Rakesh K. , Bagnara Joseph T. , Iela Luisa , Krasovich Margaret A. 
Published: February 2005

AbstractPrimary spermatogonia have highly lobate nuclei and can be distinguished as pale and dark types on the basis of nuclear and cytoplasmic features. Nuclei of secondary spermatogonia are also lobate. Primary spermatocytes have spherical nuclei and display synaptinemal complexes in late zygotene‐pachytene. Spermatocytes are connected by intercellular bridges, which persist through spermiogenesis. During spermiogenesis no acrosomal granule is formed. The acrosomal vesicle is large and forms in the apical part of the cell. A helical system of perinuclear microtubules accompanies the phase of nuclear elongation. Microtubules disappear in late spermatids and there forms a compact bundle of filaments which extends into the subacrosomal area. These filaments probably derive from the breakdown of the microtubules. A mitochondrial sleeve is formed around the proximal portion of the tail and much of it is cast off in the mature spermatid. The tail is composed of a spirally coiled contractile element and a stiff fibrous axial rod connected together by an undulating membrane. The axial rod and the axoneme‐associated rodlet derive from a dense, juxtacentriolar fibrous mass. Sertoli cells surrounding the spermatogonial and spermatocyte cysts are slender and have oblong nuclei. In contrast, those associated with spermatids are columnar and have deeply indented nuclei. They possess many Golgi complexes, elongated mitochondria, cisternae of smooth endoplasmic reticulum, lysosome‐like bodies, masses of glycogen particles, few lipid droplets, and an array of microtubules running longitudinally around the elongating spermatid nuclei. Desmosomes are formed between adjacent Sertoli cells.
Bipolar cells in the chicken retina
Authors: Quesada A. , Prada F. A. , Genis‐Galvez J. M. 
Published: February 2005

AbstractUsing the Golgi staining method with the modification suggested by Colonnier (J. Anat. 98:327, 1964), we have carried out a morphological study of the bipolar cells of the chicken and classified them into various morphological types. In the classification given we have described the existence of seven main groups of bipolar cells that differ in shape and spread of their dendritic network. In addition, within each of these groups we have taken into account other morphological features, such as the presence and position of Landolt' s club, the size of the dendritic field, the presence of an accessory dendritic process, the position of the perikaryon in the INL. The stratification of the axonal ending is demonstrated but cannot be related to the classification based on dendritic morphology that we have chosen.
Ultrastructure of the Drosophila larval salivary gland cells during the early developmental stages. I. Morphological studies
Authors: Thomopoulos George N. 
Published: February 2005

AbstractLarval salivary gland cells of seven Drosophila species from the melanogaster group were studied during the early third‐instar period. Similar cytoplasmic organization was seen in both the distal and proximal parts of the gland. The cytoplasm contained a large number of free ribosomes, but only a few rough endoplasmic reticulum profiles; the nucleolus was very large. Golgi complexes consisted mainly of vesiculated cisternae. Small secretory granules (diameter, 0.23–0.32 μm) are produced during this period and in some species contain both granular and filamentous material. These granules appeared to be secreted by a peculiar “apocrine‐type” secretion after enclosure of granules into microvillar “lacunae.” A digestive function is attributed to the secretory material. During the third instar, a close association between the salivary gland and the fat body also was observed. The physiological significance of this association seems to be related to the transfer of nutrients, enzymes, or membranous materials from fat body to salivary gland.
Organization of the vomeronasal organ in a plethodontid salamander
Authors: Dawley Ellen M. , Bass Andrew H. 
Published: February 2005

AbstractSalamanders in the family Plethodontidae show a unique behavior (nose‐tapping) and have unique structures (nasolabial grooves) that may be used specifically to convey chemicals to the vomeronasal organ. The nasal structure of Plethodon cinereus was studied to determine if there is enhanced development of the vomeronasal organ compared with other salamander families that would correlate with use of these unique features. The vomeronasal organ in salamanders is found in a ventrolateral diverticulum of each main olfactory organ. P. cinereus has a more anteriorly placed vomeronasal organ within the diverticulum, and the posterior limit of each nasolabial groove is adjacent to the anterior limit of the vomeronasal organs. This suggests that the grooves deliver chemicals preferentially to the vomeronasal organs instead of to the main olfactory organs. In addition, the vomeronasal sensory epithelium is thickest anteriorly and is at its thinnest at about the level corresponding to the location of the vomeronasal organ in other salamander families. These adaptations suggest a specific mechanism of odorant delivery to the vomeronasal organ in plethodontid salamanders not found in other salamander families.
Arthropod immune system: I. Comparative light and electron microscopic accounts of immunocytes and other hemocytes of Blattella germanica (Dictyoptera: Blattellidae)
Authors: Chiang A. S. , Gupta A. P. , Han S. S. 
Published: February 2005

AbstractLight microscopy (LM) and scanning (SEM) and transmission electron microscopy (TEM) disclose seven types of hemocytes in adults of the German cockroach, Blattella germanica (Dictyoptera: Blattellidae)—namely, prohemocytes (PR), granulocytes (GR), plasmatocytes (PL), spherulocytes (SP), adipohemocytes (AD), coagulocytes (CO), and oenocytoids (OE). Their shape, size, surface appearance, and internal ultrastructure are characterized here. The shapes and relative sizes of hemocytes noted in vitro have been compared with those flowing through the wing veins (in vivo). The GRs constitute more than 90% of the hemocyte population and have roles in the defense system such as encapsulation and phagocytosis. They are characterized by numerous cytoplasmic granules and marginal microtubular bundles, which are commonly noted in the blood cells of both vertebrates and invertebrates, but have been rarely reported in insect hemocytes. The PRs are characterized by being spherical and small, having a relatively large nucleus and a small area of cytoplasm. The polymorphic PLs have some micropapillae on the cell surface and fewer granules than the GRs. The SPs are characterized by an oblate shape, raspberrylike appearance in SEM, and many spherules in the cytoplasm. The ADs are spherical and have large, refringent fat droplets. The COs possess a distinctive cartwheellike appearance when observed by LM but resemble GRs in TEM preparations. The OEs are opaque and often have an eccentric nucleus. Of the seven types of hemocytes, all, except the COs, can be recognized both in vivo and in vitro by LM; the COs can be recognized only in vitro. SEM does not allow the COs to be distinguished from the GRs, except in samples in which coagulation has occurred. All hemocyte types can be recognized by TEM. Thus, all three types of microscopy allow the various types of hemocytes to be recognized; unequivocal discrimination among the cells is best achieved by combining all the three kinds of microscopy.
Cochlea in old world mice and rats (Muridae)
Authors: Burda Hynek , Ballast Lothar , Bruns Volkmar 
Published: February 2005

AbstractMorphometric analysis of the cochlea was performed in wild and laboratory murids: Mus musculus, Apodemus sylvaticus, Rattus rattus, R. norvegicus, NMRI mouse, and Wistar rat. Results are based on light microscopic examination of surface specimens and serial sections and on three‐dimensional computer reconstruction. The cochleae have 1.75–2.2 coils. The length of the basilar membrane varies from 6.0 to 12.1 mm. Mean density of outer hair cells ranges between 363 and 411, inner hair cells 98 and 121, neurons 1,230 and 1,760 per 1 mm. Following parameters change from base to apex: basilar membrane width 66.0 (±8.2) to 175.0 (±24.7) μm, basilar membrane thickness 17.0 (±2.6) to (±0.1) μm, width of triad of outer hair cells 13.2 (±0.7) to 28.8 (±4.4) μm. The given numbers are mean “murid” values (with respective standard deviations). Maximum of dimensions of scalae is located at 10–15%, that of density of outer hair cells at 65%, density of inner hair cells at 2.8 mm, maximum of innervation density at 40–60% from the base. The following parameters are correlated with pinna size: length and maximum width of basilar membrane, dimensions of scalae, total number of receptors, and probably resolution capabilities. The following parameters are correlated with body size: maximum width of traid of outer hair cells, density and total number of neurons, ratio of neurons to receptors, apicobasal difference in basilar membrane stiffness and width of triad of triad of outer hair cells; inversely proportional is receptor density and ratio of outer to inner hair cells and probably low‐frequency cut‐off. Thickness, and minimum width of basilar membrane and triad of outer hair cells and probably high‐frequency cutoff are species‐specific and independent of pinna or body size. The parameters mentioned indicate that the examined murids are acoustically unspecialized mammals and their cochleae approximate the generalized plan for a mammalian cochlea. Differences between domesticated and wild murids are stated.
Molt staging in artemia adapted to drach's system
Authors: Criel Godelieve R. J. , Walgraeve Hilde R. M. A. 
Published: February 2005

AbstractThe molting cycle of Artemia is described and subdivided in stages A‐D3 according to the system of Drach. Determination of the stages is done in living animals by light microscopic observation of changes in the texture of the setal matrix of the exopodites. A parallel ultrastructural investigation of the integument was carried out to control the proposed staging scheme. The duration of each stage was calculated.
Extracellular matrix of sea urchin and other marine invertebrate embryos
Authors: Spiegel Evelyn , Howard Louisa , Spiegel Melvin 
Published: February 2005

AbstractThe extracellular matrix surrounding the sea urchin embryo (outer ECM) contains fibers and granules of various sizes which are organized in recognizable patterns as shown by ultrastructural studies, particularly stereoimaging techniques. The use of the ruthenium red method for retaining and staining the ECM, with modification of the Luft (Anatomical Record 171:347–368, 1971) method for invertebrate embryos, allows for the clarification of certain structures, particularly fiber compaction in the interzonal region, and microvillus‐associated bodies.The inner ECM in the sea urchin embryo includes the basal lamina and blastocoel matrix. Stereoimages show that the fibers which are loosely distributed in the blastocoel matrix become compacted around the periphery of the blastocoel to form the basal lamina.The ruthenium red method was also used on a number of marine invertebrate embryos and larvae, representing different phyla, to facilitate comparisons between their surface coats. The similarities observed in the specimens shown suggest that ECMs are widely found on marine invertebrate eggs, embryos, and larvae, and that they resemble vertebrate ECMs and may, therefore, have similar functions.
Skeletal muscle architecture of the rabbit hindlimb: Functional implications of muscle design
Authors: Lieber Richard L. , Blevins Field T. 
Published: February 2005

AbstractThe muscle‐fiber architecture of 29 muscles from six rabbits (Oryctolagus cuniculus) was measured in order to describe the muscular properties of this cursorial animal, which possesses several specific skeletal adaptations. Several muscles were placed into one of four functional groups: hamstrings, quadriceps, dorsiflexors, or plantarflexors, for statistical comparison of properties between groups. Antagonistic groups (i.e., hamstrings vs. quadriceps or dorsiflexors vs. plantarflexors) demonstrated significant differences in fiber length, fiber length/muscle length ratio, muscle mass, pinnation angle, and number of sarcomeres in series (P<.02). Discriminant analysis permitted characterization of the “typical” muscle belonging to one of the four groups. The quadriceps were characterized by their large pinnation angles and low fiber length mass ratios, suggesting a design for force production. Conversely, the hamstrings, with small pinnation angles, appeared to be designed to permit large excursions. Similar differences were observed between plantarflexors and dorsiflexors, which have architectural features that suit them for force production and excursion respectively. Although these differences were not absolute, they represented clear morphological distinctions that have functional consequences.
Larval morphology of the bryozoan Watersipora arcuata (Cheilostomata: Ascophora)
Authors: Zimmer Russel L. , Woollacott Robert M. 
Published: February 2005

AbstractThe larva of the ascophoran cheilstome Watersipora arcuata is described on the basis of serial 1‐μ sections, light microscopy of whole mounts, and scanning electron microscopy. Using lightly osmicated specimens, it was possible to map almost every cell on the larval surface. Limited observations on hatching and larval behavior are provided in conjunction with the anatomical description. Tissues of the larva are partitioned between those that function exclusively during the larval period and are degraded at metamorphosis as transitory tissues and those that will have postmetamorphic fates in formation of the ancestrula. Significantly, W. arcuata has two possible anlagen for the ancestrular polypide, the infracoronal cells in the oral hemisphere and the epidermal blastemal cells in the aboral hemisphere, rather than only one or the other of these as reported in other species. Also detailed are the supracoronal flange and groove, which are unique to this genus and are involved in the transmission of mycoplasma‐like organisms between successive generations of adults; two pairs of complex pigment cup ocelli; multiple intercoronal cells that are presumed to have varied sensory and mechanical functions; and the sensory, adhesive, and locomotory components of the pyriform organ. The larval anatomy of W. arcuata is compared with that of the larvae of the ctenostomes Alcyonidium gelatinosum (coronate), Bowerbankia imbricata (coronate), B. gracilis (coronate), and Flustrellidra hispida (shelled lecithotrophic) and of the cheilostomes Bugula neritina (coronate), Electra pilosa (cyphonautes), and Membranipora membranacea (cyphonautes). This study is the first detailed analysis of the larval structure of any ascophoran bryozoan and provides a necessary platform for subsequent analyses of embryology and metamorphosis.
Intercoronal cell complex of larvae of the bryozon Watersipora arcuata (cheilostomata: Ascophora)
Authors: Zimmer Russel L. , Woollacott Robert M. 
Published: February 2005

AbstractThe coronate larva of the ascophoran bryozoan Watersipora arcuata has a ring of 32 large, multiciliated coronal cells that are used for swimming. Fourteen pairs of small cells are intercalated between the lateral margins of adjacent coronal cells. These intercoronal cells are arranged in a precise pattern and are polymorphic: seven pairs have multiple cilia and seven pairs are mono‐ or oligociliated. Three pairs of multiciliated intercoronal cells have their cilia arranged as a whorl that is recessed in a pocket formed between the adjacent coronal cells, and they are thought to be photoreceptors that sense general light intensity. Two other pairs of multiciliated cells with cohesive tufts of cilia may be chemo‐ or mechanoreceptors. Roles of the other intercoronal cells in this species are not evident, but it is proposed that the majority, if not all, of them are sensory. The close proximity of all the intercoronal cells to the equatorial nerve ring is compatible with this interpretation. Analyses of the literature on cleavage patterns, pigment cup ocelli, and flagellar tufts that serve as balancers in coronate larvae lead us to propose that (1) an intercoronal cell is the sensory element of most, if not all, pigment cup ocelli of bryozoan larvae; and (2) intercoronal cells are not modified coronal cells but probably are specialized supra‐ and/or infracoronal ones that have migrated to an intercoronal position.
Embryonic development of the hemipteran insect Rhodnius prolixus
Authors: Kelly Gregory Mitchell , Huebner Erwin 
Published: February 2005

AbstractThe embryonic development of the hemipteran insect Rhodnius prolixus was studied by use of contemporary light and electron microscopy. Embryos were staged according to days postoviposition. Eggs laid on day one complete blastoderm formation and anatrepsis, the first phase of blastokinesis, by day 5. The embryo develops in a cephalocaudal orientation which is 180° to the anteroposterior axis of the egg. Subsequent development, prior to the second phase of blastokinesis (katatrepsis), leads to segmentation of the germ band, evagination of appendages, and histogenesis of germ layers. Concomitantly with these events, the amnion undergoes dramatic change. By day 7 the embryo begins a 180° revolution while migrating to the ventral surface of the yolk. This restores its polarity with respect to that of the egg and facilitates hatching. The serosa contracts, pulling the amnion and embryo anteriorly. Eventually the serosa is internalized at a point dorsal to the head and the lateral walls of the embryo grow up and surround the yolk. Development continues until day 15 when the embryo hatches as a first instar larva.
Scanning electron microscopy of epithelial surfaces of the sea anemone Acontiophorum niveum (Phylum Cnidaria): Class anthozoa
Authors: Eppard Robin A. , Highison Gregory J. , Mead Robert W. 
Published: February 2005

AbstractEpithelium of the sea anemone Acontiophorum niveum is modified into four general arrangements of microappendages: (1) uniform microvilli covering pedal disc and column, (2) an interspersion of microvilli, ciliary cones, and kinocilia on tentacles, (3) flagella among an understory of microvilli from the oral disc, actinopharynx, filaments, and acontia, and (4) sparse flagella among irregular microvilli from endoderm. These arrangements are similar to those described previously in the epithelia of other anthozoans.