Ovoid Shape Research Articles

Growth behavior of Cu 6Sn 5 grains formed at an Sn3.5Ag/Cu interface

The growth behavior of Cu 6Sn 5 grains formed at an Sn3.5Ag/Cu interface was investigated. During soldering, Cu 6Sn 5 grains formed at the interface, showing a flattened ovoid shape. During solidification, Cu precipitated from molten solder in the form of Cu 6Sn 5, forming faceted surfaces on existing interfacial grains. The interfacial Cu 6Sn 5 morphology was unrelated to its crystal orientation, which was primarily dependent on reaction temperature. A reaction temperature of 240 °C led to an increase in (002) growth and a decrease in (101) growth with time. However, the (002) plane peak was not detected in the interfacial grains formed at a higher reaction temperature (280 °C).

Sperm competition does not influence sperm hook morphology in selection lines of house mice

Sperm show a remarkable degree of variation in size, shape and complexity. Murine rodents exhibit a sperm head morphology that differs greatly from the ovoid shape that is characteristic of most mammals. These rodents have sperm that bear one or more apical hooks, the function of which is currently surrounded by much controversy. It has been suggested that the hook serves to facilitate the formation of sperm groups, which in some species exhibit relatively faster velocities than single cells and thus, may provide an advantage when ejaculates are competing for fertilisations. In support of this hypothesis, a comparative study reported a positive association between the strength of sperm competition (estimated from testes size) and the curvature of the sperm hook amongst 37 murine species. Here, we assessed whether sperm competition influences sperm hookedness at the intra-specific level. Following 16 generations of selection, we used geometric morphometry (GM) to describe sperm head morphology in selection lines of house mice evolving with (polygamous) and without (monogamous) sperm competition. Although the GM analysis returned two relative warps that described variation in the curvature of the sperm hook, we found no evidence of divergence between the selection lines. Thus, we can conclude that sperm competition does not influence the degree of sperm hookedness in house mice.

A new morphogenesis pathway in bacteria: unbalanced activity of cell wall synthesis machineries leads to coccus-to-rod transition and filamentation in ovococci

Bacteria display a variety of shapes, which have biological relevance. In most eubacteria, cell shape is maintained by the tough peptidoglycan (PG) layer of the cell wall, the sacculus. The organization of PG synthesis machineries, orchestrated by different cytoskeletal elements, determines the specific shapes of sacculi. In rod-shaped bacteria, the actin-like (MreB) and the tubuline-like (FtsZ) cytoskeletons control synthesis of the sidewall (elongation) and the crosswall (septation) respectively. Much less is known concerning cell morphogenesis in cocci, which lack MreB proteins. While spherical cocci exclusively display septal growth, ovococci additionally display peripheral growth, which is responsible of the slight longitudinal expansion that generates their ovoid shape. Here, we report that the ovococcus Lactococcus lactis has the ability to become rod-shaped. L. lactis IL1403 wild-type cells form long aseptate filaments during both biofilm and planktonic growth in a synthetic medium. Nascent PG insertion and the division protein FtsK localize in multiple peripheral rings regularly spaced along the filaments. We show that filamentation results from septation inhibition, and that penicillin-binding proteins PBP2x and PBP2b play a direct role in this process. We propose a model for filament formation in L. lactis, and discuss the possible biological role of such morphological differentiation.

Micromorpho-Anatomical Examination of 2,4-D Phytotoxicity in Grapevine (Vitis vinifera L.) Leaves

The anatomical and micro-morphological alterations as induced by the auxinic herbicide, 2,4-D (2,4-dichlorophenoxy acetic acid) have not yet been elucidated for a commercially important fruit crop such as grapevine despite its super sensitivity to 2,4-D. Light and scanning electron microscopy techniques were employed to examine 2,4-D induced internal and external structural abnormalities in Merlot grapevines (Vitis vinifera L.). Healthy leaves were dorsiventrally flattened with well developed patterns of cellular structure and composition involving adaxial palisade parenchyma and abaxial spongy mesophyll. Dorsiventral variations in epidermal features involved large epidermal cells on the adaxial surface, and trichomes and stomata with turgid elliptical guard cells on the abaxial surface. The 2,4-D injured leaves were small and enated; the veins were fasciated with rugose bands of lamina existing between fasciated veins. The epidermal cells aggregated instead of being positioned coplanar to the epidermal plane. The adaxial elongated palisade parenchyma cells were transformed into an ovoid shape with intercellular spaces. An extensive development of replacement tissues took place on the abaxial surface wherein the stomata became roundish and were either raised or sunken with collapsed and cracked guard cells that developed abnormal outer stomatal ledges. These abnormalities are expected to severely perturb the vital functions of photosynthesis and transpiration ultimately leading to vine death attributable, at least in part, to the injured leaves.

Pollen morphology of the tribe Lithospermeae of Boraginoideae in China and its taxonomic significance

The pollen morphology in 15 species representing five genera in the tribe Lithospermeae of Boraginoideae (Boraginaceae) has been investigated and illustrated using light microscopy and scanning electron microscopy. The tribe Lithospermeae is very diverse in pollen morphology. The pollen grains are 10.4–41.8 × 7–33.1 μm in size with subspheroidal, prolate, cocoon, dumbbell, and ovoid shapes. The pollen apertures are of five types: 3-colporate, 3-syncolporate, 4-8-colporate, 4-6-syncolpate, and 6-7-colpate types. The exine ornamentations are generally smooth or rugulose, sparsely echinulate, and rarely rugulate. Based on pollen morphology, we developed a key to identify the genera of the tribe Lithospermeae, compared the pollen apertures among tribes of Boraginoideae, explained the evolutionary trends of the pollen grains, and discussed the taxonomic position of the tribe Lithospermeae. The palynological data suggest pollen of the eurypalynous type and support the proposal that the tribe Lithospermeae is in the primitive position of the subfamily Boraginoideae, and Echium Linn. is in the tribe Lithospermeae rather than in a novel tribe. Our observations have application potential for identification of pollen fossils of the tribe Lithospermeae.

Phylogeny of the genus Pythium and description of new genera

Phylogeny of the genus Pythium is analyzed based on sequences of the large subunit ribosomal DNA D1/D2 region and cytochrome oxidase II gene region of Pythium isolates and comprehensive species of related taxa belonging to the Oomycetes. The phylogenetic trees show that the genus Pythium is a highly divergent group and divided into five well- or moderately supported monophyletic clades. Each clade is characterized by sporangial morphology such as globose, ovoid, elongated, or filamentous shapes. Based on phylogeny and morphology, the genus Pythium (s. str.) is emended, and four new genera, Ovatisporangium, Globisporangium, Elongisporangium, and Pilasporangium, are described and segregated from Pythium s. lato.

Lac Télé structure, Republic of Congo: Geological setting of a cryptozoological and biodiversity hotspot, and evidence against an impact origin

Lac Télé is a large lake, ∼5.6 km in diameter, with an ovoid shape, situated at 17°10′E, 1°20′N, in the great tropical rain forest region of the Republic of Congo. This lake has attracted widespread attention, mainly because of the legends among the local people that it harbours a strange animal known as the Mokele-Mbembe, but also because it is situated in a region that is a hotbed of biodiversity and conservation efforts with respect to various endangered mammalian species, including gorillas and chimpanzees. Because of its appearance, Lac Télé has been regarded as a possible meteorite impact structure. Various expeditions, studying cryptozoology, conservation ecology, biodiversity, and the impact hypothesis, have visited Lac Télé in the past several decades. The Lac Télé structure is located in the NW part of the intracratonic Congo Basin, in a region dominated by Holocene alluvium, dense tropical rain forest, and swamps which form part of the basin of the Likouala aux Herbes, a multi-branched meandering river flowing over very low gradients into the Sangha river, a major tributary of the Congo river. Previous bathymetric studies have shown that the average depth of Lac Télé is only 4 m, including organic-rich silty sediments. The structure is that of a flat-bottomed dish. Modelling of the Lac Télé as an impact structure indicates a number of features which ought to be present. The absence of any of these features, coupled with the irregular ovoid shape, the palynological record, and the location of the structure at the intersection of major regional lineaments, is regarded as evidence against the impact hypothesis. Lac Télé as an isolated lake ecosystem is not unique in the Congo Basin, and there are several other similar small shallow isolated lakes surrounded by rain forest and marshes, some of which formed by damming of drainage systems by neotectonic faults. It is suggested that the formation of Lac Télé may be related to its location over neotectonically reactivated regional lineaments, which are also seismically active. Lac Télé and other similar hydrologic systems may be biodiversity hotspots because they acted as refugia following neotectonic hydrological re-organization of the Congo Basin.

Anterosuperior Calcaneal Process Fracture or OS Calcaneus Secundarius?

A 36-yr-old woman was admitted to our emergency department after having sustained an inversion injury of her right ankle. On physical examination, there was diffuse swelling and ecchymosis on the dorsolateral aspect of her foot. The ankle joint movements were in normal range without laxity. The anteroposterior and lateral x-rays of the right foot were considered to be normal by the emergency physician. The patient was diagnosed with simple ankle sprain and was treated accordingly with classical RICE protocol and a nonsteroidal antiinflammatory drug. Four weeks after the initial trauma, the patient presented to our orthopedic outpatient clinic with persistent complaint of right foot pain on weight bearing. On physical examination, severe pain on the dorsal part of the calcaneocuboid joint was present. The initial anteroposterior and lateral x-rays were reevaluated, and a fracture was suspected at the anterior calcaneal process (Fig. 1A). Medial oblique foot x-ray revealed a bony fragment located between the anterosuperior calcaneal process and the cuboid (Fig. 1B). In the differential diagnosis, anterosuperior calcaneal process fracture and OS calcaneus secundarius were considered. Further computed tomography imaging delineated the anatomy of the fragment better, while the ovoid shape, well corticated margins, regular interface, and blunt edges of the fragment supported the diagnosis of OS calcaneus secundarius, wide proximal base and considerably large size favored the anterosuperior calcaneal process fracture. Magnetic resonance imaging was eventually performed and, with the presence of bone marrow edema adjacent to the fracture line, an anterosuperior calcaneal process fracture rather than an OS calcaneus secundarius was confirmed at diagnosis (Fig. 2). She was treated with a medial longitudinal arc support, and after 1 mo, she was free of pain during mobilization.FIGURE 1: A, Medial oblique x-ray of the right foot demonstrating a suspective diagnosis of either OS calcaneus secundarius or an anterosuperior calcaneal process (ASCP) fracture (upper left). B, Computed tomography of the patient demonstrating the lesion with a wide proximal base (upper right).FIGURE 2: Magnetic resonance imaging demonstrating the bone marrow edema (bottom).OS calcaneus secundarius and anterosuperior calcaneal process fractures are two similar clinical syndromes, both of which present with anterior ankle pain.1 The differentiation of these two entities may be quite challenging only with physical examination or classical x-rays.2 Herewith, we imply that the distinction may be possible when oblique x-rays or, even better, magnetic resonance imaging is performed.3 This is important because the treatment of each syndrome is different.

Plasmodium carmelinoin. sp. (Haemosporida: Plasmodiidae) of the lizardAmeiva ameiva(Squamata: Teiidae) in Amazonian Brazil

Plasmodium carmelinoi n. sp. is described in the teiid lizard Ameiva ameiva from north Brazil. Following entry of the merozoites into the erythrocyte, the young, uninucleated trophozoites are at first tear-shaped and already possess a large vacuole: with growth, they may assume an irregular shape, but eventually become spherical or broadly ovoid. The vacuole reduces the cytoplasm of the parasite to a narrow peripheral band in which nuclear division produces a schizont with 8-12 nuclei. At first the dark, brownish-black pigment granules are restricted to this rim of cytoplasm but latterly become conspicuously concentrated within the vacuole. The mature schizonts are spherical to ovoid and predominantly polar in their position in the erythrocyte. They average 5.4 x 4,9 microm (4.4 x 4.4 - 6.6 x 5,9 microm), shape index 1.1, n = 50: 8-12 merozoites are produced and measure approximately 2.0 x 1,0 microm. Mature gametocytes are also polar in position, and spherical to subspherical. The macrogametocytes measure 5.7 x 5,2 microm (4.4 x 4.0- 5.9 x 5,1 microm), shape index 1.1, n = 50 and, following staining by Giemsa's method, possess a compact, pink-staining nucleus and a clear blue, faintly stained cytoplasm. Microgametocytes are slightly larger, 6.0 x 5,0 microm (5.2 x 4.4 - 6.2 x 5,2 microm), shape index 1.2, n = 45. They stain an over-all pink colour due to the dispersed nuclear chromatin. The vacuoles in both the macro- and microgametocytes are considerably smaller than those of the schizonts and of ovoid or spindle shape: they contain most of the pigment granules. The sex ratio, as seen in an inicial intense infection, was 1 male to 2.2 females. Prevalence of infection was low (5%) but, due to the very low parasitaemia which may result in a failure to detect parasites, it is probably higher than this.

Protonophores as inducers of energy-dependent changes of ultrastructure of mitochondria in wheat root cells

The membrane potential of plasmalemma, the release of K+ ions into incubation medium, respiratory gas exchange, the ATP content, and changes in the ultrastructure in cells of excised roots of wheat seedlings have been studied under the effect of protonophores 2,4-DNP (2,4-dinitrophenol) and CCCP (carbonyl cyanide m-chlorophenylhydrazone). After 1–4 h, a drop occurred in the plasmalemma membrane potential, as well as the release of K+ ions into incubation solution and the suppression of the intensity of oxygen absorption by cells. Mitochondria were of ovoid shape and had numerous and clearly outlined, slightly swollen cristae, which corresponds to the condensed type of the organelles. Additionally, a peculiar spatial arrangement of cristae in mitochondria has been revealed (as piles parallel to each other, as well as in the form of fans and of propellers) under the effects of protonophores. After 5 h of the action of protonophores against a background of the significant stimulation of oxygen consumption, low membrane potential, and a decrease in the functional activity of mitochondria, the destruction of the cell ultrastructure began. It is suggested that the revealed conformational transitions of mitochondria reflect gradual changes in their functional activity and the functional state of the cells under the long action of protonophores.

Homeobox genes d11–d13 and a13 control mouse autopod cortical bone and joint formation

The molecular mechanisms that govern bone and joint formation are complex, involving an integrated network of signaling pathways and gene regulators. We investigated the role of Hox genes, which are known to specify individual segments of the skeleton, in the formation of autopod limb bones (i.e., the hands and feet) using the mouse mutant synpolydactyly homolog (spdh), which encodes a polyalanine expansion in Hoxd13. We found that no cortical bone was formed in the autopod in spdh/spdh mice; instead, these bones underwent trabecular ossification after birth. Spdh/spdh metacarpals acquired an ovoid shape and developed ectopic joints, indicating a loss of long bone characteristics and thus a transformation of metacarpals into carpal bones. The perichondrium of spdh/spdh mice showed abnormal morphology and decreased expression of Runt-related transcription factor 2 (Runx2), which was identified as a direct Hoxd13 transcriptional target. Hoxd11-/-Hoxd12-/-Hoxd13-/- triple-knockout mice and Hoxd13-/-Hoxa13+/- mice exhibited similar but less severe defects, suggesting that these Hox genes have similar and complementary functions and that the spdh allele acts as a dominant negative. This effect was shown to be due to sequestration of other polyalanine-containing transcription factors by the mutant Hoxd13 in the cytoplasm, leading to their degradation. These data indicate that Hox genes not only regulate patterning but also directly influence bone formation and the ossification pattern of bones, in part via Runx2.

Morfologia dos órgãos genitais masculinos do Jurará Kinosternon scorpioides (Chelonia: Kinosternidae)

Kinosternon scorpioides é uma pequena tartaruga semi-aquática, típica de água doce, de distribuição geográfica bastante diversificada, encontrada no estado do Maranhão, onde é denominada de jurará ou muçuã. Sua carne é uma excelente fonte de proteína e a despeito da legislação vigente, é comercializado nas praias e feiras da cidade de São Luís e consumido nos restaurantes sob a forma de farofa servida em casquinha. Os órgãos genitais do macho foram estudados visando fornecer dados morfológicos da própria espécie, que poderão ser utilizados na biologia reprodutiva voltada para ações de preservação em cativeiro. Compõe-se a amostra de 10 machos adultos, obtidos mediante apreensões do IBAMA-MA (Proc. nº 020.12.002400/99-31, licença nº 002/01), os quais foram eutanaziados conforme normas do Comitê de Ética do Curso de Medicina Veterinária, Universidade Estadual do Maranhão. A cavidade celomática foi aberta e os órgãos fixados em solução aquosa de formaldeído 10%, e posteriormente dissecados. Os testículos possuem formato ovóide e coloração amarelo-ouro. Os epidídimos convolutos estavam aderidos dorsalmente à superfície medial dos testículos, terminando em um pequeno ducto deferente. Os ductos deferentes não forma-ram nenhuma ampola distinta, abrindo-se na cloaca. O pênis sulcado, localizado no assoalho da cloaca, estendeu-se até a cauda, composto de raíz, corpo e glande. A morfologia dos órgãos reprodutivos destes animais assemelha-se aos de outras tartarugas, sugerindo uma morfologia conservada entre as tartarugas.

MORPHOLOGY AND MOLECULAR PHYLOGENY OF PROROCENTRUM CONSUTUM SP. NOV. (DINOPHYCEAE), A NEW BENTHIC DINOFLAGELLATE FROM SOUTH BRITTANY (NORTHWESTERN FRANCE)1

A new marine benthic Prorocentrum species from sandy habitats of South Brittany (northwestern France), P. consutum sp. nov., is described using LM and SEM and molecular phylogenetic analyses. Cells have a subcircular to broadly ovoid shape and are plainly flattened. They are 57-61 lm long and 52-55 lm wide. A central pyrenoid is present, and the kidney-shaped nucleus is positioned in the posterior region. In right valve view, the periflagellar area is deeply excavated, and the left valve forms a prominent apical ridge. The periflagellar area consists of nine platelets, and a small narrow collar is present around the flagellar pore. The ornamentation of this new species is very peculiar and is characterized by a ring of round areolae located at the periphery of the valves, each areola containing three or four pores. Apart from this ring of areolae, the cell surface is smooth and with scattered pores. Pores are not present in the center of the right or left valve. The intercalary band is generally narrow and faintly striated horizontally. The molecular phylogenetic position of P. consutum sp. nov. was inferred using SSU and LSU rDNA. In both analyses, this species branched with high support in the clade comprising species with a symmetric shape and appeared to be a sister group to that formed by P. lima and other tropical benthic species, such as P. arenarium, P. belizeanum, P. hoffmannianum, and P. maculosum.

Criteria for the safe avoidance of needle sampling in young women with solid breast masses

To establish clinical and ultrasonic criteria by which needle sampling can be safely avoided in young women with solid breast masses. The databases of a large hospital were searched for breast cancers, phyllodes tumours, and papillomas diagnosed in women below the age of 30 years. In addition, the clinical and sonographic findings in female patients less than 25 years of age presenting with a solid breast mass over a 1-year period were reviewed. Nine women with breast cancer, seven with phyllodes, and six with papillomas were found. No delayed diagnoses in those who had ultrasound would have been made if the following criteria had been applied to avoid needle sampling: age less than 25 years; no known risk factors for breast malignancy; mass not rapidly enlarging; smooth discrete mobile mass on clinical examination, or lesion impalpable; well-defined homogeneously isoechoic or mildly hypoechoic solid mass; less than 3 cm in greatest dimension; ovoid shape, aligned parallel to the skin surface; smooth or gently lobulated contour (two or three lobulations only; no microlobulation); thin echogenic pseudocapsule; no calcification; no acoustic shadowing. Needle sampling could have been safely avoided in approximately two-thirds of the women reviewed below the age of 25 with a solid breast mass. Application of the proposed criteria would spare a significant number of young women unnecessary needle sampling.

On the presence of taste buds close to the vomeronasal organs in Gekkonidae

AbstractExamination of four different species of the squamate family Gekkonidae revealed a well developed paired vomeronasal organ (VNO) in each of them. The organs display a globular or ovoid shape and are situated underneath the nasal cavity within the rostral palate. They are in contact with the oral cavity by short, laterally curved vomeronasal ducts. In all species investigated in this study taste buds were found close to the oral orifices of the ducts, embedded into the epithelium of the area in between them. These taste buds are very likely to be involved in the function of the VNO. This conclusion is supported by similar findings in various mammals.

Dorsal spinal epidural cavernous hemangioma

A 61-year-old female patient presented with diffuse pain in the dorsal region of the back of 3 months duration. The magnetic resonance imaging showed an extramedullary, extradural space occupative lesion on the right side of the spinal canal from D5 to D7 vertebral levels. The mass was well marginated and there was no bone involvement. Compression of the adjacent thecal sac was observed, with displacement to the left side. Radiological differential diagnosis included nerve sheath tumor and meningioma. The patient underwent D6 hemilaminectomy under general anesthesia. Intraoperatively, the tumor was purely extradural in location with mild extension into the right foramina. No attachment to the nerves or dura was found. Total excision of the extradural compressing mass was possible as there were preserved planes all around. Histopathology revealed cavernous hemangioma. As illustrated in our case, purely epidural hemangiomas, although uncommon, ought to be considered in the differential diagnosis of spinal epidural soft tissue masses. Findings that may help to differentiate this lesion from the ubiquitous disk prolapse, more common meningiomas and nerve sheath tumors are its ovoid shape, uniform T2 hyperintense signal and lack of anatomic connection with the neighboring intervertebral disk or the exiting nerve root. Entirely extradural lesions with no bone involvement are rare and represent about 12% of all intraspinal hemangiomas.

Phylogeny of the genus <i>Pythium</i> and description of new genera

Phylogeny of the genus Pythium is analyzed based on sequences of the large subunit ribosomal DNA D1/D2 region and cytochrome oxidase II gene region of Pythium isolates and comprehensive species of related taxa belonging to the Oomycetes. The phylogenetic trees show that the genus Pythium is a highly divergent group and divided into five well- or moderately supported monophyletic clades. Each clade is characterized by sporangial morphology such as globose, ovoid, elongated, or filamentous shapes. Based on phylogeny and morphology, the genus Pythium (s. str.) is emended, and four new genera, Ovatisporangium, Globisporangium, Elongisporangium, and Pilasporangium, are described and segregated from Pythium s. lato.

Esthetic perception towards different combinations of facial contours and upper incisor shape

Aim: The aim of this study was to assess the esthetic perception of adults with primary, secondary and higher education and recent dental graduates towards different combinations of facial contours and upper central incisor shapes. Methods: Photographs of 6 individuals with square, tapered and ovoid facial contours (2 per type) were modified to have the 3 different types of tooth shapes (square, tapered and ovoid) in each facial contour (total of 18 photographs). The 195 participants rated each photograph using visual analogue scales. Comparison between groups was performed using the Chi-square t-test (a=0.05). Results: No statistically significant differences (p>0.05) were found in the esthetic perception towards the frontal facial outline and upper incisor shape by participants′ educational level. In addition, the shapes of teeth perceived as the most esthetically pleasing were not always similar to the form of frontal facial outline evaluated. Conclusions: No general agreement was found in the esthetic perception towards the frontal facial outline and upper incisor shape by educational level. Dentists tend to prefer ovoid shape tooth for almost all frontal facial outline.

Hypertrophic cardiomyopathy in the elderly

Hypertrophic cardiomyopathy (HCM) is a relatively common genetic cardiac disorder with heterogeneous morphological, functional and clinical features. Although the risk of sudden death and incapacitating symptoms in young patients has been focused upon, the disease has been found with increasing frequency in elderly patients. However, there have been few studies on clinical features of HCM in the elderly. We established a cardiomyopathy registration study in Kochi Prefecture, which is one of the most aged communities in Japan, to provide detailed descriptions of the clinical features of HCM in a community-based patient cohort. The unselected regional HCM population consisted largely of elderly patients (70% of the study cohort being >or=60 years of age at registration), although HCM has been regarded largely as a disease of the young. Cardiac hypertrophy that becomes clinically apparent late in life can be a genetic disorder, and mutations in the cardiac myosin-binding protein C gene are the most common cause of late-onset or elderly HCM. In the morphological features, sarcomere gene defects seem to have a predilection for a crescent-shaped left ventricular cavity with reversed septal curvature even in elderly patients, although an ovoid left ventricular shape was frequently seen in elderly patients in previous clinical studies on morphological characteristics of HCM. In middle-aged or elderly patients with HCM, heart failure and embolic events, which were strongly associated with atrial fibrillation, were very important. It is important to manage HCM patients from the standpoint of longitudinal evolution in order to prevent those clinical complications.

Fine structure of spermatozoa of Chondrostoma nasus and Rutilus meidingerii (Teleostei, Cyprinidae), as revealed by scanning and transmission electron microscopy

AbstractFürböck, S., Patzner, R.A. and Lahnsteiner, F. 2008. Fine structure of spermatozoa of Chondrostoma nasus and Rutilus meidingerii (Teleostei, Cyprinidae), as revealed by scanning and transmission electron microscopy. — Acta Zoologica (Stockholm) 91: 88–95The fine structure of spermatozoa of sneep or nase, Chondrostoma nasus, and lake chub, Rutilus meidingerii, was investigated by means of scanning and transmission electron microscopy. The uniflagellate spermatozoa of C. nasus lacked an acrosome. The flagellum contained the conventional nine peripheral doublets and one central pair of microtubules (9 + 2 pattern) and lacked lateral fins. The uniflagellate spermatozoa of R. meidingerii were made up of a head, also without an acrosome. For both species the sperm tail was covered by a plasma membrane. The midpiece of C. nasus contained five or six mitochondria on average, vesicles and glycogen granules, whereas the midpiece of R. meidingerii had seven mitochondria of a spherical or ovoid shape. The centriolar complex was located caudolaterally with respect to the nucleus. In C. nasus, the centrioles were orientated at an angle of 125° to each other, whereas the centrioles of R. meidingerii were at an angle of 110°. The fine structure of C. nasus and R. meidingerii spermatozoa showed species‐specific differences in the position of the proximal centriole relative to the distal centriole, the position and number of mitochondria, size of the head and the length of the flagellum. (Correction added on 11 June 2009, after first online publication: The word ‘axoneme’ was deleted from the sentence ‘The flagellum contained the conventional nine peripheral doublets and one central pair of microtubules (9 + 2 pattern) axoneme and lacked lateral fins.’)