Visual pigment absorbance and scotopic spectral sensitivity in the goldfish, Carassius auratus

Factors relating to the comparison of the absorbance spectra of visual pigments to experimentally determined relative spectral sensitivities of the eye are discussed with specific reference to the goldfish. It is concluded that the experimentally determined scotopic sensitivity of the goldfish can be directly related to the absorbance of goldfish porphyropsin without the need to infer input from long wavelength-sensitive cones.     

PCR survey of hox genes in the goldfish Carassius auratus auratus

A tetraploidization event took place in the cyprinid lineage leading to goldfishes about 15 million years ago. A PCR survey for Hox genes in the goldfish Carassius auratus auratus (Actinopterygii: Cyprinidae) was performed to assess the consequences of this genome duplication. Not surprisingly, the genomic organization of the Hox gene clusters of goldfish is similar to that of the closely related zebrafish (Danio rerio). However, the goldfish exhibits a much larger number of recent pseudogenes, which are characterized by indels. These findings are consistent with the hypothesis that dosage effects cause selection pressure to rapidly silence crucial developmental regulators after a tetraploidization event.     

Gill sphaerosporosis in goldfish (Carassius auratus)

Infections caused by a Sphaerospora sp. resembling S. chinensis are reported for the first time in goldfish (Carassius auratus) from North America. The myxosporean was found in the respiratory epithelium of the gill of pond-reared fish. Spores from stained tissue sections were spherical with an equal mean length and width of 6.3 microns. Spore valves were thickened at the suture which lies in a plane perpendicular to two prominent pyriform polar capsules. The polar capsules were 4.0 x 2.8 microns in length and width. Both monosporous and disporous development within a surrounding "pseudoplasmodium" was detected. Infections caused moderate hyperplasia and occasional necrosis of the respiratory epithelial cells of the gill.     

Cd-metallothionein and metal-enzymes interactions in the goldfish Carassius auratus

Goldfish injected with cadmium chloride synthesized metallothionein. Ten days after the first injection, cadmium reached a maximum in the metallothionein peak (2 micrograms/ml) obtained after gel filtration of liver cytosol. Pyruvate kinase activity was inhibited from the beginning of the experiment; after the fourth day, the enzyme activity again started to increase but did not reach the control level. Alkaline phosphatase and fructose biphosphatase did not show any apparent inhibition. From the results here reported, a detoxifying role of metallothionein could be suggested.     

Fine-structural study of leucocytes in the goldfish, Carassius auratus

An electron microscopic study was performed on leucocytes from circulating blood of the goldfish. The leucocytes were divided into eight types: neutrophil, eosinophil, large granular leucocyte (LGL), medium-sized granular leucocyte (MGL), small granular leucocyte (SGL), fine granular leucocyte (FGL), lymphocyte, and monocyte. In this report the thrombocyte was excluded from leucocytes, and LGL, MGL, SGL and FGL were tentatively classified based on the size of intracytoplasmic granules possessed by each cell. The existence of goldfish monocytes was electron microscopically demonstrated for the first time in the present report.     

A new myxozoan from feral goldfish (Carassius auratus)

In February 2004, a mass die-off of common goldfish Carassius auratus L., presumptively caused by bacterial coldwater disease (Flavobacterium psychrophilum), occurred at Fern Ridge Reservoir, Oregon. A range of size classes was affected, but all mature fish were female and all fish were infected with a single myxozoan, Chloromyxum auratum n. sp. No histological changes were observed associated with the parasite. Infection was represented by mictosporic plasmodia and free-floating spores in the gall bladder. Parasite spores were nearly spherical, 13.6 microm long x 12.6 microm wide x 13.1 microm thick, and possessed 4 equal-sized polar capsules. Spores had a coglike appearance in apical view because of distinct ridges 2.1 microm high protruding from the valve cells. There were 6-9 extrasutural ridges per valve (15-20 ridges per spore), aligned along the longitudinal axis, with some branching, and convergence at both poles. Morphologically, spores identified most closely with Chloromyxum cristatum Léger, 1906; however, 18S rDNA sequence data indicated only 97.5% similarity over 2,076 bp with Chloromyxum cyprini, the only synonym of C. cristatum for which DNA data are available; additional sequence data may reveal the other synonyms to be distinct species. This is the first record of a species of Chloromyxum from goldfish.     

Globins and hypoxia adaptation in the goldfish, Carassius auratus

Goldfish (Carassius auratus) may survive in aquatic environments with low oxygen partial pressures. We investigated the contribution of respiratory proteins to hypoxia tolerance in C. auratus. We determined the complete coding sequence of hemoglobin alpha and beta and myoglobin, as well as partial cDNAs from neuroglobin and cytoglobin. Like the common carp (Cyprinus carpio), C. auratus possesses two paralogous myoglobin genes that duplicated within the cyprinid lineage. Myoglobin is also expressed in nonmuscle tissues. By means of quantitative real-time RT-PCR, we determined the changes in mRNA levels of hemoglobin, myoglobin, neuroglobin and cytoglobin in goldfish exposed to prolonged hypoxia (48 h at Po(2) ~ 6.7 kPa, 8 h at Po(2) ~ 1.7 kPa, 16 h at Po(2) ~ 6.7 kPa) at 20 degrees C. We observed small variations in the mRNA levels of hemoglobin, neuroglobin and cytoglobin, as well as putative hypoxia-responsive genes like lactate dehydrogenase or superoxide dismutase. Hypoxia significantly enhanced only the expression of myoglobin. However, we observed about fivefold higher neuroglobin protein levels in goldfish brain compared with zebrafish, although there was no significant difference in intrinsic myoglobin levels. These observations suggest that both myoglobin and neuroglobin may contribute to the tolerance of goldfish to low oxygen levels, but may reflect divergent adaptive strategies of hypoxia preadaptation (neuroglobin) and hypoxia response (myoglobin).     

Diurnal variations in the physiology of the goldfish,Carassius auratus

Abstract

Liver glycogen, liver lipid, liver triglycerides, plasma glucose, plasma total lipid, plasma cholesterol, plasma corticoids, hypothalamic serotonin and pituitary pro‐lactin levels were assayed at five times over a 24‐h period in Carassius auratus maintained under a specific photoperiod regime at various times throughout the year. Diurnal variations were observed in all parameters monitored. Daily variations of liver glycogen, plasma glucose, plasma lipid, plasma corticoids and hypothalamic serotonin were affected by time of feeding. Liver glycogen, plasma lipid and plasma corticoid levels were also affected by time of feeding. Diurnal variations of liver glycogen, plasma glucose and plasma lipid were influenced by light‐dark cycles. These data illustrate that feeding time, photoperiod and time of sacrifice are important considerations in the study of metabolic and hormonal parameters in fishes.     

Effect of LED light spectra on exogenous prolactin-regulated circadian rhythm in goldfish,Carassius auratus

We investigated the effect of light spectra on circadian rhythm by exogenous prolactin (PRL) using light-emitting diodes (LEDs): red, green and purple. We injected PRL into live fish or treated cultured brain cells with PRL. We measured changes in the expressions of period 2 (Per2), cryptochrome 1 (Cry1), melatonin receptor 1 (MT1) mRNAs, and MT1 proteins, and in the plasma PRL, serotonin and melatonin levels. After PRL injection and exposure to green light, MT1 expression and plasma melatonin levels were significantly lower, but the expressions of Per2 and Cry1 were significantly higher than the others. Plasma serotonin after PRL injection and exposure to red light was significantly lower than others. These results indicate that injection of high concentration PRL inhibits melatonin, and inhibited melatonin regulates circadian rhythm via clock genes and serotonin. Thus, exogenous PRL regulates the circadian rhythm and light spectra influence the effect of PRL in goldfish.     

Organization of the superficial neuromast system in goldfish, Carassius auratus

Distribution, morphology, and orientation of superficial neuromasts and polarization of the hair cells within superficial neuromasts of the goldfish (Carassius auratus) were examined using fluorescence labeling and scanning electron microscopy. On each body side, goldfish have 1,800-2,000 superficial neuromasts distributed across the head, trunk and tail fin. Each superficial neuromast had about 14-32 hair cells that were arranged in the sensory epithelium with the axis of best sensitivity aligned perpendicular to the long axis of the neuromast. Hair cell polarization was rostro-caudal in most superficial neuromasts on trunk scales (with the exception of those on the lateral line scales), or on the tail fin. On lateral line scales, the most frequent hair cell polarization was dorso-ventral in 45% and rostro-caudal in 20% of the superficial neuromasts. On individual trunk scales, superficial neuromasts were organized in rows which in most scales showed similar orientations with angle deviations smaller than 45 degrees . In about 16% of all trunk scales, groups of superficial neuromasts in the dorsal and ventral half of the scale were oriented orthogonal to each other. On the head, most superficial neuromasts were arranged in rows or groups of similar orientation with angle deviations smaller than 45 degrees . Neighboring groups of superficial neuromasts could differ with respect to their orientation. The most frequent hair cell polarization was dorso-ventral in front of the eyes and on the ventral mandible and rostro-caudal below the eye and on the operculum.     

Carbohydrate metabolism of goldfish (Carassius auratus L.)

Summary The effect of hypoxia was studied in cold (15°C) and warm (30°C) acclimated goldfish. The hypoxic thresholds, defined as the lowest sustainablePO₂ were found to be 1.6 and 4.0 kPa O₂ at, respectively, 15°C and 30°C. At these levels the fish did not loose either weight or appetite over a 2-months period. While during starvation under normonic conditions a significant weight loss and breakdown of lactate dehydrogenase (90%) was observed, no such changes were found in fed hypoxic animals. In red lateral muscle, white epaxial muscle and liver of goldfish from 4 differently acclimated groups the maximal activities were measured of: glycogen phosphorylase, hexokinase, malate dehydrogenase, glycerol-3-P dehydrogenase, glucose-6-P dehydrogenase, malic enzyme, succinate oxidase, pyruvate carboxylase, phosphoenol-pyruvate carboxykinase, fructose-bisphosphatase and glucose-6-phosphatase. Thermal compensation, according to Precht's typology, was predominantly observed in red muscle and to a lesser extent in white muscle. The liver glucose-6-P dehydrogenase showed a strong inverse response, which points to enhanced synthetic activity at the higher temperature. Hypoxia acclimation exerted weaker responses at 15°C than at 30°C. Changes in liver enzyme activities suggest depressed protein synthesis and enhanced gluconeogenesis in hypoxic animals. In muscle of 30°C-acclimated goldfish hypoxia induces a significant increase of succinate oxidase activity, indicating adaptation of the aerobic energy metabolism. The occurrence of pyruvate carboxylase, never before observed in vertebrate muscle, probably plays an important role in pyruvate catabolism. Because its action produces oxalo-acetate, the enzyme may stimulate pyruvate oxidation and thus prevent early lactate accumulation. Since all gluconeogenic enzymes were shown to be active in goldfish muscle, the possible occurrence of gluconeogenesis in muscle (albeit at low rate) must be accepted. Enzyme activities in goldfish muscle were compared with literature data for a number of other fish species. This comparison indicates that maximal glycolytic flux in goldfish muscle tissue is rather low, although muscular glycogen levels are very high. It is suggested that this is part of the gold-fish's strategy to cope with hypoxia.     

Ultrastructure of the swim bladder of the goldfish,Carassius auratus

Summary The swim bladder of the cyprinid Carassius auratus (goldfish) is a two-chambered organ connected to the esophagus by a pneumatic duct. The anterior chamber is lined by a single type of squamous epithelial cell. Two types of epithelial cells are present in the posterior chamber. Flattened cells with differences in the electron density of the cytoplasm line most of the chamber. Darker cells generally contain large amounts of glycogen. Cuboidal epithelial cells also occur in the posterior chamber. A glandular layer external to the muscularis in the posterior chamber is composed of large cells containing little glycogen, an extensive Golgi apparatus, and numerous mitochondria with single large granules. Capillaries and nerves are present in large numbers in this layer. Blood vessels form micro-retia mirabilia in the submuscular layer external to the glandular layer. Vessels are of two distinct types with wide lumina and flattened endothelium characterizing the venous vessels. Arterial vessels have smaller lumina, thick endothelial cells with prominent pinocytotic vesicles, and surrounding pericytes. Collagen is present in three forms in this swim bladder — large tactoids in the tunica externa of the anterior chamber, smaller tactoids in the lamina propria of the posterior chamber, and small fibrils in all other areas.Supported by a Young Investigator Pulmonary Research Grant # 1 R23 HL 19593-01 and by HL 23338-01 from the National Institutes of Health     

Afferent projections of the trigeminal nerve in the goldfish,Carassius auratus

The horseradish peroxidase (HRP) histochemical technique was used to examine the peripheral distribution and afferent projections of the trigeminal nerve in the goldfish, Carassius auratus. Sensory fibers of the trigeminal nerve distribute over the head via four branches. The ophthalmic branch distributes fibers to the region above the eye and naris. The maxillary and mandibular branches innervate the regions of the upper and lower lip, respectively. A fourth branch of the trigeminal nerve was demonstrated to be present in the hyomandibular trunk. Upon entering the medulla the trigeminal afferent fibers divide into a rostromedially directed bundle and a caudally directed bundle. The rostromedially directed bundle terminates in the sensory trigeminal nucleus (STN) located within the rostral medulla. The majority of fibers turn caudally, forming the descending trigeminal tract. Fibers of the descending trigeminal tract terminate within three medullary nuclei: the nucleus of the descending trigeminal tract (NDTV), the spinal trigeminal nucleus (Spv), and the medial funicular nucleus (MFn). All projections, except for those to the MFn, are ipsilateral. Contralateral projections were observed at the level of the MFn following the labeling of the ophthalmic and maxillomandibular branches. All branches of the trigeminal nerve project to all four of the trigeminal medullary nuclei. Projections to the STN and MFn were found to be topographically organized such that the afferents of the ophthalmic branch project onto the ventral portion of these nuclei, while the afferents of the maxillo- and hyomandibular branches project to the dorsal portion of these nuclei. Cells of the mesencephalic trigeminal nucleus were retrogradely labeled following HRP application to the ophthalmic, maxillary, and mandibular branches of the trigeminal nerve. In addition to demonstrating the ascending mesencephalic trigeminal root fibers, HRP application to the above-mentioned branches also revealed descending mesencephalic trigeminal fibers. The descending mesencephalic trigeminal fibers course caudally medial to the branchiomeric motor column and terminate in the ventromedial portion of the MFn.