Fine structure of taste buds in the barbel of the catfish,Ictalurus punctatus

Summary Taste buds occur in the epithelium of the catfish barbel along its entire length. Two major cell types, light and dark cells, occupy the upper two-thirds of the taste bud. A third cell type, the basal cell, lies on the basal lamina and is essentially separated from the light and dark cells by a plexus of unmyelinated nerve fibers. The dark cells have branching processes, both apically and basally whereas the light cells have a single apical process and many basal processes. The apical processes of dark cells contain secretory granules, while the apical processes of light cells contain an abundant agranular endoplasmic reticulum. Light cell nuclei contain bundles of 10 nm filaments, often arranged in the shape of a cup or ring, but nucleoli are rarely seen. It is suggested that this morphology indicates a low degree of RNA synthesis by light cells. The basal cells contain large numbers of vesicles, about 60 nm in diameter, which are sometimes seen in clumps in relation to an adjacent nerve fiber in a configuration resembling a synapse. Curiously, although basal cells present a large surface to the basal lamina, there are no hemidesmosomes. This suggests that the basal cell does not originate from the epidermis.Supported by grant#NS-06181 from the National Institute of Neurological Diseases and Stroke, U.S. Public Health Service     

Organization of the telencephalon in the channel catfish,Ictalurus punctatus

The cytoarchitectonics of the telencephalon of the channel catfish, Ictalurus punctatus, are described as a basis for experimental analysis of telencephalic afferents and efferents. The olfactory bulb comprises: (1) an outer layer of olfactory nerve fibers, (2) a glomerular layer, (3) an external cell layer, (4) an inner fiber layer, and (5) an internal cell layer. The telencephalic hemispheres comprise the areas ventralis and dorsalis telencephali. The area ventralis consists of: (1) a precommissural, periventricular zone including nucleus 'nother (Vn), the ventral nucleus (Vv), and the dorsal nucleus (Vd); (2) a precommissural, migrated zone of central (Vc) and lateral (VI) nuclei; (3) a supracommissural nucleus (Vs); (4) a caudal commissural zone of postcommissural (Vp) and intermediate (Vi) nuclei; and (5) a preoptic area (PP). The area dorsalis comprises: (1) medial (DM), (2) dorsal (Dd), (3) lateral [DL, containing dorsal (DLd), ventral (DLv), and posterior (DLp) regions], (4) posterior (DP), and (5) central (DC-1, -2, -3) areas. Nucleus taeniae (NT) is transitional between areas dorsalis and ventralis.     

Density-independent growth of floodplain river channel catfish Ictalurus punctatus

This study investigated the relative influence of biotic and abiotic factors on the growth of channel catfish Ictalurus punctatus in seven Mississippi floodplain rivers. The results indicate that growth was density-independent, being defined largely by abiotic conditions.     

Histology of cultured channel catfish, Ictalurus punctatus (Rafinesque)

Dissolved oxygen and un-ionized ammonia concentrations were monitored in 12 0.04 ha earthen ponds stocked with 10 000 channel catfish, Ictalurus punctatus ,/ha. Gill, liver and trunk kidney tissue samples were removed periodically for histological examination. Total ammonia and dissolved oxygen levels were in the ranges reported for catfish culture at this level of intensity. Average un-ionized ammonia nitrogen concentrations ranged from 20 to 67 μgh⁻¹ and average daily maxima ranged from 63 to 183 μgh⁻¹. Gill lesions characteristic of un-ionized ammonia exposure were common in fish from all ponds.     

Immune hypersensitivity in the channel catfish, Ictalurus punctatus (Rafinesque)

Channel catfish, Ictalurus punctatus , exhibited passive cutaneous anaphylaxis (PCA) when sensitized with Flexibacter columnaris antiserum produced in channel catfish (the first record of PCA in any fish), but not when sensitized with homologous antiserum against channel catfish virus. Channel catfish did not give delayed skin hypersensitivity responses after immunization with either channel catfish virus or F. columnaris .     

A microsatellite-based genetic linkage map for channel catfish, Ictalurus punctatus

Microsatellite loci were identified in channel catfish gene sequences or random clones from a small insert genomic DNA library. Outbred populations of channel catfish contained an average of eight alleles per locus and an average heterozygosity of 0.70. A genetic linkage map of the channel catfish genome (N = 29) was constructed from two reference families. A total of 293 microsatellite loci were polymorphic in one or both families, with an average of 171 informative meioses per locus. Nineteen type I loci, 243 type II loci, and one EST were placed in 32 multipoint linkage groups covering 1958 cM. Nine more type II loci were contained in three two-point linkage groups covering 24.5 cM. Twenty-two type II loci remained unlinked. Multipoint linkage groups ranged in size from 11.9 to 110.5 cM with an average intermarker distance of 8.7 cM. Seven microsatellite loci were closely linked with the sex-determining locus. The microsatellite loci and genetic linkage map will increase the efficiency of selective breeding programs for channel catfish.     

Hepatic drug metabolizing enzyme activity in the channel catfish, Ictalurus punctatus

1. Several pathways of drug metabolizing enzymic activity were measured in hepatic fractions of the channel catfish and rat using model substrates. The pathways examined included the O-demethylation of p-nitroanisole, microsomal ester hydrolysis of procaine and glucuronidation of p-nitrophenol, and the cytosolic acetylation of sulfamethazine and sulfation of 2-naphthol. Catfish liver preparations were incubated at both 25 degrees C and 37 degrees C. 2. The oxidative metabolism of p-nitrophenol was only one-eighth that of the rat at 37 degrees C and one-twelfth that of the rat at 25 degrees C. 3. Procaine ester hydrolysis was negligible in catfish microsomal preparations. 4. At 37 degrees C, p-nitrophenol glucuronidation was equivalent in catfish and rat microsomes. 5. Catfish cytosolic preparations exhibited N-acetyltransferase and arylsulfotransferase nearly comparable to those of the rat. 6. Rates of glucuronidation and sulfation were higher at 37 degrees C than at 25 degrees C in hepatic fractions of catfish.     

Structure and expression of transferrin gene of channel catfish,Ictalurus punctatus

Transferrin is important in iron metabolism and has been reported to be involved in disease defence responses after bacterial infection. In this study, we identified, sequenced, and characterized the transferrin gene from channel catfish, Ictalurus punctatus. The catfish transferrin gene was similar to those of other vertebrate species with 17 exons and 16 introns. Sequence analysis indicated the presence of the two duplicated lobes, each containing two sub-domains separated by a cleft harboring the iron-binding site, suggesting their structural conservation. The channel catfish transferrin cDNA encodes 679 amino acids with 42–56% similarity to known transferrin genes from various species. Southern blot analysis suggested the presence of two copies of the transferrin gene in the catfish genome, perhaps arranged in a tandem fashion. The catfish transferrin gene was mapped to a catfish BAC-based physical map. The catfish transferrin gene was highly expressed in the liver, but expression was low in most other tested tissues. Transferrin expression was significantly up-regulated after infection with Edwardsiella ictaluri, the causative agent of enteric septicemia of catfish. Such induction was also found with co-injection of iron-dextran and E. ictaluri, while transferrin expression was not significantly induced with the injection of iron-dextran alone.     

Afferent connections of the optic tectum in channel catfish Ictalurus punctatus

Summary Horseradish peroxidase was injected unilaterally into the optic tectum of the channel catfish, Ictalurus punctatus. The sources of tectal afferents were thereby revealed by retrogradely labeled neurons in various brain centers. Retrogradely labeled cells were seen in both the ipsilateral and contralateral telencephalon. The superficial pretectal area was labeled on both sides of the brain. Ipsilateral projections were also observed coming from the entopeduncular nucleus. Both the anterior thalamic nucleus and the ventro-medial thalamic nucleus projected to the ipsilateral optic tectum. Cells in the ipsilateral nucleus of the posterior commissure were seen to project to the tectum. Labeled fibers were visualized in the lateral geniculate nucleus ipsilateral to the injected tectum, however, no labeled cell bodies were observed. Therefore, tectal cells project to the lateral geniculate nucleus, but this projection is not reciprocal. No labeled cells were found in the cerebellum. Labeled cells occurred in both the ipsilateral and contralateral medial reticular formation; they were also observed in the ipsilateral nucleus isthmi. A projection was seen coming from the dorsal funicular nucleus. Furthermore, labeled cells were shown in the inferior raphe nucleus.Abbreviations AP Area pretectalis - C Cerebellum - DPTN Dorsal posterior tegmental nucleus - H Habenula - IRF Inferior reticular formation - LI Inferior lobe - LGN Lateral geniculate nucleus - LR Lateral recess - MB Mammillary body - MRF Medial reticular formation - MZ Medial zone of the telencephalon - NC Nucleus corticalis - NDL-M Nucleus opticus dorsolateralis/pars medialis - NI Nucleus isthmi - NPC Nucleus of the posterior commissure - OPT Optic tectum - OT Optic tract - PC Posterior commissure - PN Pineal organ - PrOP Preoptic nucleus - PT Pretectum - TBt Tectobulbar tract - TEL Telencephalon - TL Torus longitudinalis - TS Torus semicircularis - VC Valvula cerebelli - VLTN Ventrolateral thalamic nucleus - VMTN Ventromedial thalamic nucleus     

Cloning and characterization of microsatellite loci in channel catfish, Ictalurus punctatus

Short tandem repeat (microsatellite) loci were cloned from the channel catfish, Ictalurus punctatus , genome for use as molecular markers for genetic improvement of this important agricultural species. Plasmid clones containing catfish genomic DNA inserts were identified, by hybridization with tandem repeat DNA probes, and sequenced using automated laser fluorescence. A feral population of catfish displayed levels of heterozygosity greater than 0·7 for 13 of 22 loci and heterozygosity greater than 0·5 for 20 of 22 loci. Allelic polymorphism ranged from three to 17 alleles per locus in the feral population. Populations of domestic, farm-raised catfish and a research strain displayed levels of heterozygosity similar to the feral population. Non-invasive tissue sampling provided abundant material for the polymerase chain reaction-based genotype assay. The microsatellite loci will be useful in the molecular characterization and genetic improvement of channel catfish populations.     

Methylmercury accumulation and fluxes across the intestine of channel catfish,Ictalurus punctatus

The excised intestines of channel catfish, Ictalurus punctatus, were perfused at 20 or 4 degrees C for 1 h 45 min, with methylmercury (CH(3)HgCl) alone, or in the presence of excess L-cysteine (L-Cys), D-cysteine (D-Cys), L-methionine (L-Met); or with ouabain or probenecid to identify the potential CH(3)Hg(II) uptake pathways in fish intestines. A temperature effect was noted, with CH(3)Hg(II) concentrations in tissues perfused at 20 degrees C being higher than at 4 degrees C, substantiating the idea that mechanisms requiring metabolic energy are involved in CH(3)Hg(II) uptake in fish intestines. The results indicate that, when CH(3)Hg(II) is complexed as the CH(3)Hg-L-Cys complex, it is taken up via an L-neutral amino acid carrier and rapidly transported to the serosal side of the intestine. Methylmercury uptake could be inhibited by probenecid and ouabain, although probenecid had less impact on CH(3)Hg(II) uptake than ouabain. Our results for CH(3)Hg(II) uptake in the presence of D-Cys, L-Met in excess of L-Cys, or with a metal mixture further established that CH(3)Hg(II) uptake across fish intestines occurs via a variety of pathways, including an energy-dependent L-neutral amino acid carrier, and that the route and amount of accumulation were a function of CH(3)Hg(II) speciation in the digestive tract of the fish.     

Assignment of immune-related genes to the channel catfish, Ictalurus punctatus, genetic map

Eighteen new genes, adenosine A1 receptor (ADORA1), complement component 4-beta (C4b), complement component 8-beta (C8b), chemokine ligand 19 (CCL19), chemokine ligand 21 (CCL21), chemokine ligand 25 (CCL25), chemokine receptor 2 (CCR2), chemokine receptor 5 (CCR5), chemokine receptor 4 (CCR4), chemokine receptor 7 (CCR7), chemokine receptor 9 (CCR9), interleukin 1-beta (IL1B), integrin II-beta (ITGB2), novel immune type receptor 2 (NITR2), novel immune type receptor 4 (NITR4), natural killer cell lysin (NKLYSIN), nucleotide excision repair (RAD23B) and tumour necrosis factor-alpha (TNF), were assigned to the channel catfish (Ictalurus punctatus) genetic linkage map. Polymorphic microsatellite markers were developed for NITR2, NITR4 and RAD23B from short-tandem repeats in the available sequence. Polymorphic microsatellite markers were developed for the remaining 15 genes by short-tandem repeat-anchored primer sequencing of catfish bacterial artificial chromosomes. Two gene clusters (MYOG-NRAMP-ADORA1) and (CCR4-CCR2-CCR5) displayed conservation of synteny between catfish and mammals. Assignment of 18 new genes to the catfish linkage map will further advance integration of genetic and physical maps and comparative mapping between channel catfish and map rich species.     

Gastrointestinal torsion in a channel catfish (Ictalurus punctatus)

A case of gastrointestinal torsion with dilatation in a farm-raised channel catfish (Ictalurus punctatus) was examined at the Thad Cochran National Warmwater Aquaculture Center (Stoneville, Mississippi, USA). The affected fish was a gravid female broodfish, which displayed pale gills and a markedly distended abdomen. Internal examination revealed that the gastrointestinal tract and ovaries were rotated around each other four times in a counterclockwise direction as viewed in right lateral recumbency. The catfish had a markedly distended gastrointestinal tract, pale liver, hypoplastic spleen, hypoplastic swim bladder, and high volume of ascitic fluid. Blood analysis indicated multiple abnormalities, including severe anemia and metabolic acidosis. The etiology of the torsion was uncertain; however, the presence of a hypoplastic swim bladder most likely allowed for increased movement of the gastrointestinal tract and ovaries. When examining cases of abdominal distention in fish, gastrointestinal torsion can be considered among the differential diagnoses.     

Environmental stress and bacterial infection in channel catfish, Ictalurus punctatus Rafinesque

Channel catfish, Ictalurus punctatus , were injected intraperitoneally with a sublethal dose of Aerornonas hydrophila and then stressed for 144 h by being maintained either in a dissolved oxygen concentration of 1·5 mg/1, 1·2 mg/1 total ammonia, and/or 6·5 mg/1 free CO₂ with a continuous inflow of water. A significant difference in percentage of mortality was noted between treatments ( P < 0·05). The trunk kidneys of surviving stressed fish had significantly higher total bacterial counts than non-stressed controls. A. hydrophila was isolated from 67% of the stressed fish and 9% of the control fish. Edwardsiella tarda , apparently endemic in the population, was isolated from 43% of the stressed fish and 7% of the control fish. Histopathological lesions were in the gills, liver, spleen, trunk kidney, and head kidney of stressed fish, but not control fish.     

Respiratory-cardiovascular physiology and chloroethane gill flux in the channel catfish, Ictalurus punctatus

A fish respirometer-metabolism chamber was used to obtain in vivo respiratory-cardiovascular and chloroethane gill flux data on transected channel catfish (Ictalurus punctatus). Methods used for spinal transection, attachment of an oral membrane (respiratory mast), placement and attachment of blood cannulas and urine catheters are described. Respiratory physiology, cardiac output and chemical extraction efficiencies for 1,1,2,2-tetrachloroethane (TCE), pentachloroethane (PCE), and hexachloroethane (HCE) were determined on 419–990 g catfish. The overall mean values (± s.d.) for ventilation volume (Q_v), effective respiratory volume (Q_w), oxygen consumption (Vo₂ and percentage utilization of oxygen (U) were 17-3 ±4–71 h^?1 kg^?1, 9·8±l·71 h^?1 kg^?1, 71·6±12·5mg h^?1 kg^?1, and 49± 10%, respectively, while cardiac output calculated via the Fick Method was 2·4±0·61 h^?1 kg^?1. Additional measurements were made on ventilation rate (V_r), total plasma protein, haematocrit (Hct), and urine volume; while both arterial and venous blood were analysed for pH, oxygen partial pressure (P02), carbon dioxide partial pressure (Pco₂), total oxygen (To₂), total carbon dioxide (Tco₂) and total ammonia (TAMM). Physiological measurements taken at 24 h were not significantly different from those taken at 48 h and indicated no deterioration of the in vivo preparation. All of these values agreed well with literature values on UTitransected channel catfish, except for Hct which was lower for cannulated animals used in this study. Overall, these data provide strong support for the use of transected channel catfish for in vivo collection of physiological and chemical gill flux data. The mean initial chemical extraction efficiencies for TCE, PCE and HCE were 41, 61 and 73%, respectively. Chemical clearances (Cl_X) for these same three chemicals were 5·9, 9·3 and 10·8 1 h^?1 kg^?1, respectively. The approximate 1: 1 relationship between effective respiratory volume (Q_w) and chemical clearance (Cl_x) indicated that branchial uptake of PCE and HCE was water flow-limited. Chemical gill flux observed for channel catfish and chloroethanes was similar to that observed for rainbow trout in previous studies and provided further support for the flow-limited model of chemical flux across fish gills.     

Histophathology and electron microscopy of channel catfish virus in infected channel catfish,Ictalurus punctatus (Rafinesque)*

A histologic and electron microscopic study was made on selected organs from channel catfish Ictalurus punctatus (Rafinesque) fingerlings that were experimentally infected with channel catfish virus (CCV). Histopathology was characterized by necrosis and haemorrhage in kidney and liver, and haemorrhage in the spleen and gastrointestinal tract. Virus replication occurred in nuclei of cells in the kidney, liver and spleen. Intranuclear inclusion bodies consisting of geometric crystalline arrays and lamellar structures were associated with virus replication.