Colour vision in the passeriform bird,Leiothrix lutea: correlation of visual pigment absorbance and oil droplet transmission with spectral sensitivity

The visual receptors in the retina of the passeriform bird Leiothrix lutea were examined microspectro-photometrically. The rods had a maximum absorbance close to 500 nm. Four spectrally different classes of single cone were identified with typical combinations of photopigments and oil droplets: a long-wave sensitive cone with a photopigment P568 and a droplet with a cut-off wavelength at 564 nm, a middle-wave sensitive cone with a P499 and a droplet with a cut-off at 506 nm, a short-wave sensitive cone with a P454 and a droplet with maximum absorbance below 410nm and an ultraviolet sensitive cone with a P355 and a transparent droplet. Double cones possessed a P568 in both the principal and accessory members. A pale droplet with variable absorbance (maximal at about 420 nm) was associated with the principal member whereas the ellipsoid region of the accessory member contained only low concentrations of carotenoid. The effective spectral sensitivities of the different cone classes were calculated from the characteristic combinations of oil droplets and photopigments and corrected for the absorbance of the ocular media. Comparison of these results with the behavioural spectral sensitivity function of Leiothrix lutea suggests that the increment threshold photopic spectral sensitivity of this avian species is mediated by the 4 single cone classes modified by neural opponent mechanisms.Abbreviations LWS long wave sensitive - MWS middle wave sensitive - SWS short wave sensitive (cones)     

Distribution of FMRFamide-like immunoreactivity in the brain,retina and nervus terminalis of the sockeye salmon parr,Oncorhynchus nerka

Summary Neurons displaying FMRFamide(Phe-Met-Arg-Phe-NH₂)-like immunoreactivity have recently been implicated in neural plasticity in salmon. We now extend these findings by describing the extent of the FMRF-like immunoreactive (FMRF-IR) system in the brain, retina and olfactory system of sockeye salmon parr using the indirect peroxidase anti-peroxidase technique. FMRF-IR perikarya were found in the periventricular hypothalamus, mesencephalic laminar nucleus, nucleus nervi terminalis and retina (presumed amacrine cells), and along the olfactory nerves. FMRF-IR fibers were distributed throughout the brain with highest densities in the ventral area of the telencephalon, in the medial forebrain bundle, and at the borders between layers III/IV and IV/V in the optic tectum. High densities of immunoreactive fibers were also observed in the area around the torus semicircularis, in the medial hypothalamus, median raphe, ventromedial tegmentum, and central gray. In the retina, immunopositive fibers were localized to the inner plexiform layer, but several fiber elements were also found in the outer plexiform layer. The olfactory system displayed FMRF-IR fibers in the epithelium and along the olfactory nerves. These findings differ from those reported in other species as follows: (i) FMRF-IR cells in the retina have not previously been reported in teleosts; (ii) the presence of FMRF-IR fibers in the outer plexiform layer of the retina is a new finding for any species; (iii) the occurrence of immunopositive cells in the mesencephalic laminar nucleus has to our knowledge not been demonstrated previously.     

Retinal projections in sockeye salmon smolts (Oncorhynchus nerka)

Summary The retinal projections in 2-year-old salmon smolt (Oncorhynchus nerka) are significantly different from those observed in other teleosts examined to date in that the projections are more extensive. Very noticeable are extensive projections to most of the dorsal thalamus, to all layers of the optic tectum, and into the periaqueductal gray of the torus semicircularis. The salmon smolt has bilateral retinal projections to the diencephalon and pretectum. A small retinal projection to the lateral habenular nucleus has not been described previously. Although these findings suggest striking differences in retinal projections among teleosts, this variation may relate to age differences since the previously studied teleosts were adults.     

Photoreceptor development in the pineal organ and the eye of Plecoglossus altivelis and Paralichthys olivaceus (Teleostei)

Summary The ontogenetic apperance of pineal photo-receptors was compared with that of retinal photoreceptors in the ayu Plecoglossus altivelis and the lefteye flounder Paralichthys olivaceus, which hatched 10 days and 3 days after fertilization, respectively. Despite the disparity in incubation time, the outer segments (containing membranous lamellae) of the pineal photoreceptors first appeared from 3 to 4 days after fertilization in both species. In contrast, the outer segments of the retinal photoreceptors first became visible 5 to 6 days after fertilization, although a characteristic retinal stratification and the optic tract leaving the ganglion cell layer were already found 4 days after fertilization in both species. The functional significance of these temporal disparities and/or similarities in photoreceptor development are discussed with special reference to the timing of daily rhythmic activities during the early developmental period of the teleosts.The results were presented at the Annual Meeting of the Japanese Society of Scientific Fisheries on April 2, 1990 (Tokyo)     

Effects of cortisol on gill chloride cell morphology and ionic uptake in the freshwater trout,Salmo gairdneri

Summary Daily intramuscular injection of cortisol (4 mg kg^–1 body weight) in rainbow trout,Salmo gairdneri, for 10 days caused significant increases in the number and individual apical surface area of gill chloride cells per mm² of filament epithelium. Concomitantly, whole body influxes of sodium (Na⁺) and chloride (Cl^–) increased. Acute (3 h) intra-arterial infusion of cortisol did not affect whole body Na⁺ or Cl^– influx. A significant correlation was observed between both Na⁺ and Cl^– influxes and the fractional apical surface area of filament chloride cells in control, sham (saline-injected) and experimental (cortisol-injected) fish. The chloride cells displayed similar ultrastructural modifications in trout undergoing cortisol treatment as in trout transferred to ion-deficient water. These findings suggest the existence of structure/function relationships in which branchial chloride cell morphology is an important determinant of Na⁺ and Cl^– transport capacity. We conclude that chronic cortisol treatment enhances whole body Na⁺ and Cl^– influxes by promoting proliferation of branchial chloride cells. The results of correlation analysis indicate that the chloride cell is an important site of NaCl uptake in freshwater rainbow trout.     

Pineal-retinal relationships: rhythmic biosynthesis and immunocytochemical localization of melatonin in the retina of the pike (Esox lucius)

Summary The levels of melatonin and the activities of two enzymes of the melatonin biosynthetic pathway, serotonin N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT), were measured throughout the light-dark cycle in the retina of a teleost fish, the pike. HIOMT activity did not display significant variations, whereas NAT activity and melatonin content showed a daily rhythm, high levels occurring during the night. The profiles of the latter two rhythms did not closely match one another and differed from those previously described in the pineal organ of the same species. These results are discussed with respect to a possible paracrine role of retinal melatonin. Melatonin-like immunoreactivity was found in the photoreceptor cell layer and in the Müller cells of the inner nuclear layer. The intensity of the melatonin-like immunoreactivity varied throughout the 24 h light-dark cycle, in good correlation with the variations in the melatonin level as measured by radioimmunoassay.This article is dedicated to the memory of Dr. Klaus Hoffmann     

The role of epithelial remodelling in tooth eruption in larval zebrafish

Based on light and transmission electron-microscopic observations on erupting first-generation teeth in the zebrafish, Danio rerio, we propose a biphasic mechanism for tooth eruption: (1). formation of an epithelial crypt prior to eruption of the tooth, possibly as a result of constraints in the epithelium resulting from the growth of adjacent tooth germs, and (2). detachment of cellular interdigitations both within the pharyngeal epithelium, at the pharyngeal epithelium/enamel organ boundary, and between the outer and inner dental epithelium, resulting in the exposure of the tooth tip in the crypt, immediately after tooth ankylosis. Later, further detachment of interdigitations between the inner and the outer enamel epithelium unfolds the epithelium even more and leads to a more pronounced exposure of the tooth tip. The presence of small patches of non-collagenous matrix on the outer surface of the tooth close to where it merges with the attachment bone is interpreted as a device to prevent complete detachment of the enamel organ. The biphasic nature of the mechanism for tooth eruption is supported by observations on in vitro cultured heads. First-generation teeth develop normally and crypts are formed, as under in vivo conditions, but the teeth fail to erupt. Taken together, our observations suggest that epithelial remodelling plays a crucial role in eruption of the teeth in this model organism.     

Cytoplasmic lipid droplets and mitochondrial distribution in equine oocytes: Implications on oocyte maturation, fertilization and developmental competence after ICSI

Lipid droplets (LDs) and mitochondria in the ooplasm are essential for energy production required for maturation, fertilization and embryo development. This study investigates the correlations between cytoplasmic LDs polar aggregation and: (1) nuclear maturation (Experiment 1); (2) mitochondrial (mt) distribution pattern and localization (Experiment 2); (3) fertilization and embryonic development after intracytoplasmic sperm injection (ICSI; Experiment 3) in equine oocytes recovered from slaughtered mares and matured in vitro. Morphologically normal oocytes were selected after culture and categorized as having polar (P) aggregation or uniform (U) distribution of LDs. In Experiment 1, the maturation rate was significantly higher in P compared with U oocytes (69%, 40/58 vs. 32%, 13/41; P < 0.001). In Experiment 2, it was observed that P and U oocytes showed heterogeneous mt distribution at comparable rates (68%, 25/37 vs. 50%, 2/4 for P and U respectively; NS). Moreover, only in 8/25 (32%) of P oocytes, LDs overlapped with mt aggregates in the area containing meiotic spindle. In Experiment 3, normal fertilization (51%, 19/37 vs. 60%, 6/10, for P and U) and cleavage rates (83%, 20/24 vs. 67%, 4/6, for P and U) did not differ between groups, also in oocytes with LDs located nearby the polar body. Overall, P aggregation of LDs was related to cumulus expansion at collection. In conclusion, in equine matured oocytes, P aggregation of LDs is related with cumulus expansion and nuclear maturation. However, it is not related with heterogeneous mt distribution and cannot be considered a predictive indicator for normal fertilization and embryo development.     

Oil droplets and yolk spheres during development of Medaka embryos

The sizes of oil droplets (globules) and the yolk sphere in the Medaka Oryzias latipes egg were measured in the developmental period from fertilization to hatching. Oil droplets coalesced with one another in the process of shifting toward the vegetal pole, and a single large oil droplet was finally located at the vegetal pole region in most eggs 2 days post-fertilization. The volume of the yolk sphere steeply decreased in the period from 2 to 8 days post-fertilization. The volume of oil droplets also declined linearly from 4 to 10 days post-fertilization. Lipid components exhibited no distinct change during embryogenesis. In order to verify whether oil droplets were required for development of Medaka embryos, oil droplets were artificially removed from the early developing embryos without the chorion (egg envelope). Naked embryos without the oil droplet developed normally to fry in the sterilized incubation medium and grew to the same mature fry as those grown from the control embryos.     

Amacrine cells in the retina of a cyprinid fish: functional characterization and intracellular labelling with horseradish peroxidase

Summary Forty amacrine cells in retinae of a cyprinid fish, the roach, were intracellularly labelled with horseradish peroxidase following electrophysiological identification as sustained depolarizing, sustained hyperpolarizing or transient units. Labelled cells were analysed by light microscopy and compared with a catalogue of amacrine cells established in a previous Golgi study on the same species. About 30% of the cell types characterized by the Golgi method were encountered in the present study. When intracellularly labelled cells were differentiated on the basis of their dendritic organization in the plane of the retina, a given electrophysiological response pattern was found to be generated by different morphological types, and vice versa. However, examination of the ramification patterns of the dendrites within the inner plexiform layer (i.e. in the radial dimension of the retina), showed that this morphological parameter of a given amacrine cell could be correlated with its light-evoked response. Several amacrine cell types were found to possess special distal dendrites which arose from the main dendritic branches and extended well over a mm in the retina. Distal dendrites were oriented tangentially with respect to the optic nerve papilla, but did not appear to be involved in any synaptic connectivity. It is concluded that the Golgi-based classification is a valuable tool for identifying intracellularly labelled amacrine cells. However, although the correlation between layering of dendrites in the inner plexiform layer and electrophysiology was generally good, additional physiological parameters would be required to determine whether more extensive parallels exist between structural and functional characteristics of amacrine cells. Alternatively, the considerable morphological diversity of amacrine cells may be of limited physiological significance.A preliminary account of the present findings was presented to the Physiological Society (Djamgoz et al. 1984)     

Rapid monitoring of cell size, vitality and lipid droplet development in the oleaginous yeast Waltomyces lipofer

The aim of this work was the development of rapid methods suitable for monitoring the growth of the oleaginous yeast Waltomyces lipofer by means of cell size, vitality and the development of internal lipid droplets throughout different growth phases. Oleaginous yeasts are of interest for the industrial production of lipids and therefore precise monitoring of growth characteristics is needed.This paper provides information about both the method development as well as about examples for their use in monitoring applications. Cell size and shape were determined using FPIA (Flow Particle Image Analysis). Vitality and internal lipid droplets were measured using two independent staining methods for Flow Cytometry. Double staining with cFDA & PI was used for the distinction between “vital”, “sublethal” and “dead” subpopulations, whereas Nile Red allowed the monitoring of lipid accumulation. In this approach the method for vitality measurement was optimized focussing on the staining buffer. An addition of 25 mM citric acid and pH 4.8 revealed to be optimal. The cells in the growth experiment showed a constantly high vitality, which was always above 90%, but slowly decreasing over time. In the course of lipid droplet development it could be seen that the cell size and the Nile Red fluorescence intensity increased. It was demonstrated that the tested method combination provides a powerful tool for rapid fermentation monitoring of the oleaginous yeast W. lipofer, which allows gaining information about the desired growth characteristics in less than 45 min. Further applications for the two methods will be discussed in this article.     

An interplexiform cell in the goldfish retina: light-evked response pattern and intracellular staining with horseradish peroxidase

Summary The light-evoked response pattern and morphology of one interplexiform cell were studied in the goldfish retina by intracellular recording and staining. The membrane potential of the cell spontaneously oscillated in the dark. In response to a brief light stimulus, the membrane potential initially gave a slow transient depolarization. During maintained light, the oscillations showed a tendency to be suppressed; the response of the cell to the offset of the stimulus was not so prominent. The perikaryon of the interplexiform cell was positioned at the proximal boundary of the inner nuclear layer. The cell had two broad layers of dendrites; one was diffuse in the inner plexiform layer, the other was more sparse in the outer plexiform layer. The morphological and electrophysiological characteristics of the cell are discussed in relation to dopaminergic interplexiform cells and the light-evoked release pattern of dopamine in the teleost retina.     

Evolution of the monocot gynoecium: evidence from comparative morphology and development in Tofieldia, Japonolirion, Petrosavia and Narthecium

We present new comparative morphological and developmental data on gynoecia of three genera of early-divergent monocots: Tofieldia (Tofieldiaceae, Alismatales), Petrosavia and Japonolirion (Petrosaviaceae, Petrosaviales) and one lilioid monocot: Narthecium (Nartheciaceae, Dioscoreales). Our data show significant differences between the genera examined, and are congruent with the splitting of former Nartheciaceae sensu Tamura (1998) into families Tofieldiaceae, Petrosaviaceae NB-cosistent with later and Nartheciacae (APG II 2003). Our investigation confirms the presence of at least partial carpel fusion in all taxa examined. Previous data indicating apocarpy in Japonolirion, some Petrosavia and Tofieldia could be due to late postgenital carpel fusion in these plants. Syncarpy also characterises other early-divergent monocot lineages such as Acoraceae and Araceae. It is most parsimonious to regard syncarpy as a primitive condition for monocots, but an alternative scenario suggests that apocarpy is plesiomorphic among monocots, involving multiple origins of syncarpy. The latter hypothesis is supported by significant differences between gynoecia of early-divergent monocots, including different modes of carpel fusion.     

Immunocytochemical identification of prolactin cells in the pituitary gland of tilapia larvae (Oreochromis mossambicus: Teleostei)

Summary Using an antiserum to highly purified chum salmon prolactin, prolactin cells were identified in the putative rostral pars distalis of newly hatched tilapia larvae (Oreochromis mossambicus) by the immunogold method for the electron microscope. In the putative rostral pars distalis, some cells had another kind of secretory granule which was much less numerous, much smaller in size, and without immunoreactivity to salmon prolactin antiserum. Controls incubated with salmon prolactin-preabsorbed antiserum or normal serum showed no immunoreactive cells, confirming the specificity of the antiserum. The possible role of prolactin in the osmoregulation of tilapia larvae is discussed.     

Ontogeny of the endocrine pancreas in sea bass (Dicentrarchus labrax): an ultrastructural study. I. The primordial cord and the primitive,single and primordial islets

The primordial cord and the primitive, single and primordial islets present in the 3 earliest stages of the developing endocrine pancreas of sea bass were studied ultrastructurally. The primordial cord consisted of type I and II cells and was included in the gut. Besides these cell types, X cells were seen in the primitive islet. The single islet was made up of type I, II, III and IV cells. A correlation between these endocrine cell-types and cells previously identified immunocytochemically, was established. Type I, II, III and IV cells, correlated respectively with SST-25-, insulin-, SST-14- and glucagon-immunoreactive cells, and could be related to the D₁, B, D₂ and A cells, respectively, of older larvae and adult sea bass. Each cell type shows characteristic secretory granules from its first appearance. A progressive development of the organelles and an increase in the number and size of the secretory granules, whose ultrastructure also varied, was observed in the endocrine cells of the primordial cord and the succeeding islets. In 25-day-old larvae at the beginning of the fourth developmental stage, the primordial islet, the first ventral islet found, was close to a pancreatic duct and blood vessel, and consisted of type I and II cells whose ultrastructure was similar to that of the type I and II cells in the primordial cord. These data suggest a ductular origin for the pancreatic endocrine cells in the ventral pancreas. It is suggested that although endocrine cells undergo mitosis, their increase in number during the earliest development stages is principally due to the differentiation of surrounding cells.     

Ontogenetic changes in the chemistry and morphology of oil glands in Hermannia convexa (Acari: Oribatida)

As a first example for the chemistry of oil gland secretions in the Hermannioidea (one of the three superfamilies of desmonomatan Oribatida), the oil gland secretion of Hermannia convexa was investigated by gas chromatography–mass spectrometry. Hexane extracts of all juvenile stages showed a multicomponent chromatographic pattern, mainly consisting of well-known oil gland secretion components such as neral, geranial, -acaridial and the unsaturated C17-hydrocarbons, 6,9-heptadecadiene and 8-heptadecene. The secretion profiles of juveniles varied slightly between samples of two different collections, namely in the presence of -acaridial and 8-heptadecene. Furthermore, a minor component, identified as 1,8-cineole (= eucalyptol) and hitherto not known from oil gland secretions of other species, was recorded in both juvenile and adult extracts. In adult profiles, 1,8-cineole, in low amounts, represented the only detectable component; thus, their profiles fundamentally differed from those of juveniles. A subsequent histological investigation revealed well developed oil glands in all juvenile stages, but degenerated oil glands in adults, consistent with the chemical data. So far, apart from H. convexa, degeneration of oil glands in the course of ontogenetic development is only known from a brachypylid species; on the other hand, chemical oil gland-polymorphism between juveniles and adults may occur in closely related Nothridae while it does not occur in oil glands of early- and middle-derivative Oribatida (Parhyposomata, Mixonomata, trhypochthoniid Desmonomata), nor in astigmatid mites.This revised version was published online in May 2005 with a corrected cover date.     

The larval development of an Australian limnadiid clam shrimp (Crustacea, Branchiopoda, Spinicaudata), and a comparison with other Limnadiidae

The adult morphology of the Australian Limnadopsis shows some remarkable differences to that of other Limnadiidae. These differences are not reflected in its larval development. In Limnadopsis parvispinus, larval development comprises six stages. In stages I and II only the three naupliar appendages are present: the antennule as a small bud, the biramous antenna as the main swimming organ, and the mandible. The antennal protopod bears two endites, the proximal naupliar process and a more distal endite. In stage III a bifid naupliar process (in earlier stages not bifid) and the first signs of the carapace and trunk limb anlagen (undifferentiated rudiments) appear. In stage IV the carapace anlagen become more pronounced. The number of trunk limb anlagens increases to five, and differentiation has commenced. In stage V the first five pairs of trunk limbs are differentiated to varying degrees. The anterior-most four pairs of trunk limbs are subdivided into five endites, a small endopod, an exopod and an epipod. The bivalved carapace covers the anterior-most limbs. In larval stage VI the carapace is larger and the trunk limbs are further differentiated. A general pattern in the sequence of larval stages is the increasing number of sensilla on the antennules. From the last larval to the first postlarval stage, a significant change in morphology takes place. The trunk limbs are now used for swimming. Typical larval organs are much smaller than in the last larval stage. A comparison with other representatives of the Limnadiidae shows a high degree of correspondence, with most differences explained by the heterochronous appearance of characters during development. Five to seven stages are described for all studied Limnadiidae, including one particular stage in which four fully developed setae, a bifid naupliar process and the first signs of carapace anlagen are present. These characters are found in stage III in L. parvispinus, Limnadia stanleyana, Eulimnadia texana, and Imnadia yeyetta but in stage IV in E. braueriana and L. lenticularis. Based on a comparison of the larval stages of six limnadiid and one cyzicid species, we conclude that at least six naupliar stages belong to the limnadiid ground pattern.     

Cranial meninges of goldfish: age-related changes in morphology of meningeal cells and accumulation of surfactant-like multilamellar bodies

In the optic tectum of goldfish, the outer, middle and inner layers of the endomeninx were evident in animals ranging in age from 1 month to several years. The outer layer in young animals consisted of closely overlapping cells with intertwined processes, whereas in the older animals it contained large extracellular spaces. The intermediate layer cells were always arranged in a single continuous layer, but in young animals they overlapped extensively with one another toward their edges whereas in the oldest animals they became extremely flat and non-overlapping. The inner layer included an outer tier of cells with their bases adhering to the intermediate layer, and an inner tier of cells detached from both the intermediate layer and the basal lamina overlying the brain parenchyma. Inner layer cells contained many large vacuoles that were in continuity with the extracellular space. With age, the extracellular space and the vacuolar system expanded, and the inner layer evolved into a meshwork of attenuated cytoplasmic processes embedded in the granular extracellular matrix. Another age-related feature was the accumulation adjacent to the basal lamina of uniform disc-shaped membranous structures, resembling multilamellar bodies of lung surfactant. These disc bodies were apparently generated by the coalescence of vesicles formed at the surface of the inner layer cells, possibly as a by-product of protein secretion by these cells.