Apical Pits Research Articles

Development of mitochondrion‐rich cells in the yolk‐sac membrane of embryos and larvae of tilapia, Oreochromis mossambicus, in fresh water and seawater

AbstractThe development and changes in the activity of mitochondrion‐rich (MR) cells in the yolk‐sac membrane of tilapia (Oreochromis mossambicus) embryos and larvae were examined in relation to environmental salinity. Size and density of MR cells were monitored until complete yolk resorption in embryos and larvae spawned and hatched in fresh water (FW) and seawater (SW), and in larvae transferred from FW to SW or from SW to FW. MR cells were present in the yolk‐sac membrane of embryos 2 days after fertilization and were significantly larger in SW than in FW. In embryos and larvae maintained until complete yolk resorption in FW, the size of MR cells tended to decrease as the larvae grew older, whereas in those maintained in SW, the large size of MR cells was maintained. After direct transfer of newly hatched larvae from FW to SW, the size of MR cells markedly increased, and decreased when newly hatched larvae were transferred from SW to FW. MR cell density did not vary appreciably between larvae in FW and those in SW, and was not significantly affected by transfer of larvae from FW to SW or vice versa. Electron‐microscope examination of MR cells in the yolk‐sac membrane revealed the presence of numerous mitochondria, well‐developed tubular system and apical pits, indicating similarity with MR cells in branchial and opercular epithelia of adult fish. In tilapia embryos, in which the gills, gut, and kidney are not yet fully developed, MR cells in the yolk‐sac membrane are potentially important sites for ion exchange in SW. © 1994 Wiley‐Liss, Inc.

Resurrection of the genus Osmundea with an emendation of the generic delineation of Laurencia (Ceramiales, Rhodophyta)

Abstract Vegetative and reproductive development of some European and Californian species of Laurencia Lamouroux (Ceramiales, Rhodophyta), L. obtusa (Hudson) Lamouroux, L. spectabilis Postels et Ruprecht, L. crispa Hollenberg, L. osmunda (S.G. Gmelin) Maggs et Hommersand, L. pinnatifida (Hudson) Lamouroux and L. truncata Kutzing, is investigated on the basis of liquid-preserved and herbarium specimens. The latter five species share several features, but they differ distinctly from L. obtusa, the lectotype of the genus, in essential anatomical characters of vegetative and male reproductive structures and tetrasporangial development. In these five species each vegetative axial segment produces two rather than four pericentral cells, and spermatangial branches (filaments) are produced in apical pits of branchlets from apical and epidermal cells rather than from trichoblasts arising from axial cells. The spermatangial branches are usually branched alternately and usually terminate in a cluster of several larg...

Proton pumps in fish gill pavement cells?

The gill epithelium which comprises several types of cell faces multiple functions (O2/CO2 transfer, acid-base balance and ionic regulation). Little is known of the respective cellular localization of these functions. TEM examination of the catfish gill shows, in pavement cells, cytoplasmic vesicles and apical pits, both ornamented with studs reminiscent of the proton pumps observed in H+ secretory epithelia. Ornamented apical pits are more frequently observed in acidotic fish. Taking together with our previous studies, this finding suggests that pavement cells play an important role, in addition to transfer of gas, by secreting protons. A new model of gill exchanges is proposed.

A re-examination of Laurencia hybrida (Ceramiales, Rhodophyta) from the British Isles: vegetative and reproductive morphology

Developmental morphology of Laurencia hybrida (A.P. de Candolle) Lenormand ex Duby (Ceramiales, Rhodophyta) from the British Isles was re-examined. Each vegetative axial segment produces a trichoblast and two pericentral cells which are characteristic of the subgenus Chondrophycus Tokida et Saito, †† The correct name of this subgenus is Chondrophycus, not Chondrophycae as suggested by McDermid (1988). According to the International Code of Botanical Nomenclature (Greuter 1988), Art. 21.2, the epithet of a subgenus is either of the same form as a generic name, or a plural adjective.Chondrophycus is a noun (like the generic names Hesperophycus and Akkesiphycus) and is consequently correct as it is. but reproductive morphology differs from both the subgenera Chondrophycus and Laurencia. Spermatangial branches are produced in the apical pit of branchlets. They are derived from epidermal cells and apical cells rather than from trichoblasts, and show alternate rather than dichotomous branching. They usually terminate in a cluster rather than in a single large sterile vesicular cell. The fertile segment (suprabasal cell) of the female trichoblast produces six pericentral cells rather than four or five, the sixth becoming the supporting cell of the procarp. Tetrasporangia are randomly produced from epidermal cells near the apical pit of stichidia rather than from particular pericentral cells. Cleavage from the epidermal cells takes place laterally rather than ab- or adaxially. Of these anatomical characters, the presence of procarp-bearing segments with six pericentral cells is so far unique within the genus Laurencia. The spermatangial and tetrasporangial characters suggest that L. hybrida is phylogenetically different from the subgenera Laurencia and Chondrophycus and perhaps belongs to a separate genus.

Structure of the respiratory islets of accessory respiratory organs and their relationship with the gills in the climbing perch, Anabas testudineus (Teleostei, Perciformes).

The epithelial and sub-epithelial organization of the accessory respiratory organs of Anabas testudineus has been compared with that of gills by using light and transmission electron microscopy. The details of vascular supply of respiratory islets (RI) and gill filaments and the presence of venous sinusoids in the two systems suggest that the RI have been derived from gill filaments and lamellae. The biserial arrangement of transverse capillaries (TC) in the respiratory islets (RI) is evident under the scanning electron microscope and their homology with the gill filaments and their secondary lamellae has been established. The two sets of transverse capillaries of respiratory islets have been derived either from embryonic transverse or marginal channels of two sets of lamellae of a gill filament. These capillaries with their endothelial septate valves and tongue-like processes offer resistance to blood flow. Gill filaments have two vascular pathways, arterio-arterial and arterio-venous. However, the RI of accessory respiratory organs contain the arterio-venous pathways. This arrangement as well as the septate transverse capillaries may lower the "pulmonary" blood pressure considerably. Two types of mitochondria-rich cells are identified: i) chloride cells with flat microvilli bearing surfaces, devoid of apical pit and (ii) an elongated cell type with sac-like endoplasmic reticulum, with apical pit that comes into close contact with the complex matrix of macrophages, lymphocytes and other loose cells of the epithelium. These cells may be associated with detoxification of the internal media of fish inhabiting foul waters.

Ultrastructure ofTessellaria volvocina(Synurophyceae)

The ultrastructure of Tessellaria volvocina is described by means of transmission electron microscopy. The large colonies consist of a single peripheral layer of cells with long tails that extend to the centre. The scales making up the colonial investment cover the cell anterior only. No scales are present within the colony. The cell organelles are arranged in a typically synurophycean manner, with the exception of the chloroplasts which lie horizontally within the cell as opposed to vertically in Synura and Mallomonas. The flagellar root system of T. volvocina is simpler than that described for other synurophytes, comprising only one microtubular root which arises from the rhizoplast and encircles the apical flagellar pit. This root is associated with a band of dense material and acts as a microtubule-organizing centre, originating cytoskeletal microtubules in two planes. Tessellaria volvocina possesses several ultrastructural characters typical of the Synurophyceae but differs in its flagellar root syst...

Influence of Photoperiod on the Number and Ultrastructure of Gill Chloride Cells of the Atlantic Salmon (Salmo salar) before and during Smoltification

Atlantic salmon (Salmo salar) larger than 9 cm held under constant light since October had greater numbers of gill chloride cells in February compared with fish held under simulated natural photoperiod. By April, fish raised under simulated natural photoperiod were able to survive salinity tests, had a threefold increase in Na+/K+ATPase activity, and had increased chloride cell numbers. These increases and salinity tolerance did not occur in fish raised under constant light. Only fish reared under constant light developed apical pits with large and numerous microvilli.

Morphological effects of mercury exposure on windowpane flounder gills as observed by scanning electron microscopy

Windowpane flounder, Scophthalmus aquosus Mitchill, were exposed for 60 days to 5 or 10 μg 1−1 mercury and gill samples were examined by scanning electron microscopy. The response of the gill epithelium was different at the two levels of mercury exposure. The number of chloride cell apical pits and gill filaments bearing ‘cratered’ epithelial cells increased at the 5‐μg 1−1 level and decreased at the higher exposure level.Focal swellings demonstrated a dose‐dependent relationship, their numbers being greatest at the higher exposure level. Marked fragmentation of pavement cell microridge patterns and swelling of the respiratory epithelial cells was evident at the 10‐μg 1−1 exposure level.

Bryozoan larvae as mosaics of multifunctional ciliary fields: Ultrastructure of the sensory organs of Bugula solonifera (Cheilostomata: Cellularioidea).

The ultrastructure of ciliated sensory and effector organs has been examined by light microscopy and by scanning and transmission electron microscopy in larvae of the cellularioid cheilostome, Bugula stolonifera. The larval surface is formed by a mosaic of ciliary fields, each distinctive in organization and function. The most extensive ciliary field consists of the motile cilia of the corona, which collectively constitute the primary larval locomotory organ and form most of the larval surface. The corona is innervated basally by a nerve ring that circumscribes the larval equator. A circular field of immotile shorter cilia at the aboral pole arise from bands of radial cells in the apical disc. The radial ciliated cells form chemical synapses with underlying nerves of the paired aboral nerve cords, which extend to an equatorial nerve plexus on the median anterior side of the larva, beneath the pyriform organ. The pyriform organ is a complex of ciliated and glandular regions aligned along the anterior midline of the larva. It consists of, in aboral to oral sequence: the superior glandular field, the vibratile plume, the inferior glandular field, and the ciliated cleft. The vibratile plume is distinctive from the surrounding ciliation by its length and pattern of beating. It consists of four bundles of cilia approximately 64 μm long that beat rhythmically in synchrony into the ciliated cleft. Each bundle of cilia arises from a single cell which is further distinguished by apical pits of stout microvilli. The glandular fields and the vibratile plume are bordered by a variety of previously undescribed ciliated cells, longitudinal myoepithelial cells, and a pair of antero-medial eyespots. Another type of ciliated sensory cell is located between cornal cells. These intercoronal cells form synapses directly with the adjacent coronal cells. On the basis of these ultrastructural observations, the radial ciliated cells of the apical disc and the intercoronal cells are classified as primary sensory cells with different motor pathways. The radial ciliated cells are associated with the various effector organs of the larva via the nervous system. The intercoronal cells may combine sensory and motor functions by synapsing directly with the larval locomotory organ.

Multicellular complex of chloride cells in the gills of freshwater teleosts.

Morphology of branchial chloride cells in the freshwater teleosts Plecoglossus altivelis, Cyprinus carpio, and Oreochromis mossambicus was studied by light and transmission electron microscopy. The chloride cell has an apical membrane directly in contact with the outer medium. Generally, two or more neighboring chloride cells share an apical pit, forming a multicellular complex. The chloride cells form a multicellular complex in which cells differ in cytoplasmic electron density, development of tubular system, and in cell size. Chloride cells are linked by junctions which are shallower than the tight junctions that occur between neighboring pavement cells or between pavement and chloride cells. Multicellular complexes of chloride cells create additional paracellular pathways marked apically by the shallower junctions. Since junctional structure affects transepithelial permeability, development of multicellular complexes of chloride cells in freshwater fishes may be related to the transport of some substances as in the gills of marine fishes.

Histopathological Changes in the Gills of Pearl Dace, Semotilus margarita, and Fathead Minnows, Pimephales promleas, from Experimentally Acidified Canadian Lakes

The gills of pearl dace form experimentally acidified Canadian ELA lakes 223 (pH 5.2) and 114 (pH 5.8) and fathead minnows from Lake 114 were examined microscopically and compared with gills from unacidified waters. The acid-exposed gills exhibited (1) hyperplastic primary lamellar epithelia, (2) diminished respiratory lamellar surface areas, (3) widened respiratory blood-water barriers, and (4) altered cellular composition and morphology, especially greater numbers of chloride (ionoregulatory) cells with and without apical pits. While little can be said about the effects of acid water on fish based on such a small sample of lakes, the present research does not contradict the views expressed by many investigators that very soft water with a low pH and toxic metal ions has a deleterious effect on gills and the physiological processes associated with them.

The taxonomy and life history of Gloiophloea (Galaxauraceae, Rhodophyta)

The red algal genus Gloiophloea J. Agardh (Galaxauraceae, Nemaliales) includes multiaxial, dichotomously branched plants that are composed internally of a filamentous central axis, radiating dichotomously branched medullary filaments, and a loose cortex of spherical, pigmented cells. An examination of the three species presently included has shown that only the type species, G. scinaioides J. Agardh, should be maintained. Gloiophloea articulata Weber-van Bosse from Cargados Carajos, near Mauritius, is known only from a single collection of sterile plants. It differs from G. scinaioides in lacking an apical pit, having periclinal medullary filaments which loosely fill the internal cavity rather than being restricted to a central axis, and producing a cortex composed of files of closely appressing cells, rather than a loose matrix. Gloiophloea articulata appears more closely allied to the family Gymnoploeaceae of the order Gigartinales, in particular the genus Nemastoma J. Agardh. Sexual material needs to be examined, however, before the species can be placed without doubt. Gloiophloea perrinae Levring from southern Australia was distinguished from G. scinaioides in having a firmer texture and in minor differences in its cortical composition and cystocarp shape. Variations in these characters occur within the type species, however, and are probably due to age and growing conditions. Gloiophloea perrinae is therefore reduced to synonymy with G. scinaioides. In culture, carpospores of G. scinaioides give rise to a filamentous tetrasporophyte which produces cruciate tetrasporangia. Tetraspores in turn produce a filamentous protonemal gametophyte which gives rise to the fleshy gametophyte directly. The life history of Gloiophloea is therefore identical to that of the closely related genus Scinaia Bivona-Bernardi.

Two types of chloride cells in the gill epithelium of a freshwater-adapted euryhaline fish: Lebistes reticulatus; their modifications during adaptation to saltwater.

Two types of chloride cells were identified in the gill epithelium of freshwater-adapted guppies. One type, referred to as an "alpha-chloride cell," was a pale, elongated cell located at the base of the secondary lamella in close contact with the arterioarterial pillar capillaries. In its cytoplasm, membranous tubules in continuity with its basolateral plasma membrane formed an extended tridimensional network. The vesiculotubular system (Pisam: Anat. Rec. 200:401-414, 1981) consisted of a few tubules and vesicles located next to the apical plasma membrane. A second type, referred to as a "beta-chloride cell," was a darker, ovoid cell located in the interlamellar region of the primary epithelium facing the central venous sinus. Membranous tubules in continuity with the basolateral plasma membrane were unevenly distributed in the cytoplasm. A prominent vesiculotubular system composed of numerous vesicles and tubules was found between the Golgi apparatus and the apical surface. During seawater adaptation, the alpha-chloride cells increased in size and progressively transformed into characteristic "seawater alpha-chloride cells" with a well-developed, regular, tight tubular network and numerous vesicles and tubules of the vesiculotubular system accumulated below the apical pit. The beta-chloride cells underwent a progressive degeneration and disappeared. Thus, in freshwater-adapted guppies, there are two types of chloride cells, alpha and beta, respectively, related to the arterial and the venous vessels, whereas in seawater-adapted fishes, a single type of cell, the alpha-chloride cell, was related to both the arterial and venous channels.

Pentastomid Nymph From the Brain of a Squirrel Monkey (Saimiri sciureus). II. Morphology of the Host Response

A Porocephalus nymph found in the meninges of a squirrel monkey was encapsulated by connective tissue cells and fibrils presumably derived from the pia mater. The capsule was composed of an inner layer (IL) adjacent to the nymphal integument and an outer layer (OL) adherent to the brain surface. Separating the two layers was a capsular space. The IL was lined by a granular material adjacent to the nymph surface and possessed impressions of annulae and the apical pits of chloride cells. The surface of IL facing the capsular space was characterized by a monolayer of cells possessing extensive anastomosing plasmalemmal processes. The OL was composed of several tiers of fibroblasts and associated collagen fibrils that adhered to the brain surface in the form of a thickened pia mater. It is suggested that the capsule was formed by a modification of the pia that isolated the nymph and created an "intracapsular space" with specialized lining cells to facilitate fluid exchange.

A New Species of Tantilla from Veracruz, Mexico

Holotype:-Herpetological Collection of the Estaci6n de Biologia Tropical Los Tuxtlas, U.N.A.M., No. 1668 (field no. 83101), an adult female from Cerro Chochobi, elevation 800 m, El Acuyal area, 8 km NW Catemaco, Veracruz, Mexico, 17 April (night) 1983, Gonzalo Perez-Higareda. Paratype. No. 1671 in the same collection (to be deposited in the University of Colorado Museum), from Balzapote, elevation 50 m, Municipality of San Andres Tuxtla, Veracruz, 12 Nov. 1983, Marcelo Paxtian. Diagnosis.-Lateral light stripe on scale rows 3 and 4; middorsal light line confined to vertebral scale row; lower third of first scale row mostly light, upper two-thirds uniformly dark, at midbody; light collar complete laterally but interrupted medially; lateral area, between lateral light line and ventral color, all densely pigmented; medial edge of lateral light line also densely pigmented; other areas on dorsum lightly pigmented; 159 ventrals, 56 subcaudals. Description of Holotype (Figs. 1, 2).-Dorsal scale rows 15 throughout body, smooth, lacking apical pits; anal divided; total length 346 mm, tail 69

Lamellated outer dendritic segments of a chemoreceptor within wall-pore sensilla in the labial palp-pit organ of the butterfly, Pieris rapae L. (Insecta, Lepidoptera)

The structure of the sensilla in the apical pit of the third segment of the labial palps in Pieris rapae was investigated in cryofixed and chemically fixed specimens. There is a field of about 80 club-shaped sensilla, 94% of which house a single sensory cell; 6% contain two sensory cells. All sensory cells are of the same type and are characterized by the structure of the dendritic outer segment. This consists of a proximal cylindrical and a distal lamellated section. The lamellae contain a lattice of longitudinally arranged microtubules. Filamentous strands connect the microtubules with the surface membrane of the lamellae. The surface area of the lamellated section amounts to about 40 μm2. Pores and pore tubules are present in the cuticular wall of the peg. Electrophysiological recordings show that the sensory cells are olfactory receptors, which react to a variety of complex plant odors and to the odor of conspecifics. It is shown that (a) the usual modality-specific characteristics of insect olfactory sensilla apply here also; (b) lamellation is not only a characteristic of thermoreceptors, but also of olfactory chemoreceptors; (c) there are pore tubules that are separated from the dendritic membranes by an extended dendritic sheath; and (d) in the labial palppit sensilla only the lamellated dendritic tip region may be involved in sensory transduction.

REPRODUCTION AND LIFE HISTORY OF THE RED ALGA GALAXAURA OBLONGATA (NEMALIALES, GALAXAURACEAE)1

ABSTRACTCulture and morphological studies showed that Galaxaura oblongata (Ellis et Solander) Lamouroux has a triphasic life history with conspicuous gametophytes and small filamentous tetrasporophytes. Development of male and female reproductive structures is very similar and both begin with the enlargement of a terminal cell of a filament branch occupying a normal vegetative position within the apical pit of a thallus branch. In male thalli this modified branch forms a conceptacle in which spermatangia are produced. In female thalli, this modified branch forms a three‐celled carpogonial branch consisting of a carpogonium, hypogynous cell and basal cell. Filament branches from the basal cell form a pericarp and the gonimoblast develops directly from the carpogonium. Carposporangia are produced in conceptacles which resemble the male conceptacles. About the time the first carposporangia are produced, the carpogonium, hypogynous cell and basal cell form a large fusion cell. Released carpospores germinate in a unipolar or bipolar manner and form small filamentous thalli. Under short day conditions, cruciate tetrasporangia are produced in small clusters. Tetraspores germinate similarly to carpospores and also form small filamentous thalli. Under low nutrient conditions, small cylindrical thalli develop on the filaments and these appear similar to gametophytes collected in nature.

Morphological and morphometrical changes in chloride cells of the gills of Pimephales promelas after chronic exposure to acid water.

Fathead minnows, Pimephales promelas, were exposed for 129 days to Lake Superior water acidified with sulfuric acid by means of a flow-through toxicant injection system. The effects of chronic acid stress (pH 6.5, 6.0, 5.5, 5.0) on gill histology were examined. Most of the histological effects were seen at pH 5.5 and 5.0 and were confined primarily to changes in numbers, distribution, and morphology of chloride cells. At low pH levels there tend to be more chloride cells in the gill epithelium and an increased percentage of these cells in the secondary lamellae. In contrast to normal chloride cells, chloride cells from fish exposed to low pH frequently had apical pits while some had bulbous apical evaginations. The occurrence of structural changes in chloride cells during exposure to acid water suggests that chloride cells may be involved in acclimation to acid stress.

Development of apical pits in chloride cells of the gills of Pimephales promelas after chronic exposure to acid water

Groups of 12 fathead minnows were exposed for 129 days to Lake Superior water acidified (pH 5.0, 5.5, 6.0 or 6.5) with reagent grade H2SO4 by means of a multichannel toxicant system for flow-through bioassays. Untreated water (pH 7.5) had the following properties: hardness 45.3 ± 0.3 (95% confidence interval) mg/1 as CaCO3; alkalinity 42.6 ± 0.2 mg/1; Cl- 0.03 meq/1; Na+ 0.05 meq/1; K+ 0.01 meq/1; Ca2+ 0.68 meq/1; Mg2+ 0.26 meq/1; dissolved O2 5.8 ± 0.3 mg/1; free CO2 3.2 ± 0.4 mg/1; T= 24.3 ± 0.1°C. The 1st, 2nd and 3rd gills were subsequently processed for LM (methacrylate), TEM and SEM respectively.Three changes involving chloride cells were correlated with increasing acidity: 1) the appearance of apical pits (figs. 2,5 as compared to figs. 1, 3,4) in chloride cells (about 22% of the chloride cells had pits at pH 5.0); 2) increases in their numbers and 3) increases in the % of these cells in the epithelium of the secondary lamellae.

The Liophis cobella Group of the Neotropical Colubrid Snake Genus Liophis

The Liophis cobella group consists of four species, L. breviceps, L. cobella, L. frenatus, and L. longiventris. The color pattern of the species in this group consists of a dark brown to black ground color with narrow light bands. The banding may be obscure in old adults, but the venter is consistently banded or checkered with black and coral red marks. The average number of dorsal bands, ventrals, subcaudals, maxillary teeth and tail length as a percentage of total length among the species of the group varies from 30-90, 138-189, 50-59, 15-22, and 17.0-20.0 respectively. Num- bers of scale rows are invariably 17-17-15, scales smooth, without apical pits. A brief history of the names of some species and keys to the species and subspecies are presented for the group. The group previously was thought to consist of eight species among 14 named forms, but addi- tional material from other localities have shown overlap of features between some taxa previously regarded as full species, resulting in the reduction to subspecific status of L. canaimus and L. trebbaui; the recognition of L. taeniogaster as a valid subspecies; the description of a new subspecies; and the placement of the currently recognized species L. brazili and L. ingeri as junior subjective synonyms of L. frenatus and L. cobella, respectively. One form, Coluber cinereus Linnaeus, cannot be allocated to any currently recognized colubrid genus.