The biliary bile acids of the channel catfish, Ictalurus punctatus, and the blue catfish, Ictalurus furcatus.
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Animals↗
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Evidence of genome-wide relaxed selection on mildly deleterious mutations in an ancient subterranean catfish.
About one hundred subterranean catfish species have been described, resulting from repeated colonization of cave environments by multiple surface lineages. Most cave-dwelling species are found in the Americas, in particular in South America, but a few species also live in Central and North America. Despite the availability of high-quality genome assemblies for two cave species, the Mexican blind catfish Prietella phreatophila and the Colombian blind catfish Trichomycterus rosablanca, genomic approaches to investigate genetic changes associated with subterranean life or to estimate cave colonization times remain largely unexplored. To fill this gap, we additionally sequenced the genomes of four blind and depigmented subterranean catfishes from Peru (three Trichomycterus and one Astroblepus), as well as the genomes of four close surface relatives. We first extracted a large set of light-related genes, such as phototransduction and crystallin genes, and found contrasting decays of these sequences in different cave species, from 1% of pseudogenes in T. rosablanca to 48% in P. phreatophila. Two independent molecular dating methods gave congruent ages, indicating that these catfishes colonized subterranean habitats at different times, ranging from Early Pliocene to Late Pleistocene, supporting the hypothesis that surface catfishes repeatedly and rapidly adapted to subterranean habitats. The oldest cave species, P. phreatophila, appears to have been thriving in the dark for over 3.5 million years. Moreover, a genome-wide analysis of protein-coding genes suggests weaker purifying selection on mildly deleterious mutations in this cavefish than in other catfish lineages, likely reflecting a long-term small effective population size.
cavefishes↗
Accumulation and elimination of dieldrin in muscle tissue of channel catfish.
Dieldrin accumulation and elimination in muscle tissue of channel catfish (Ictalurus punctatus) from water and food was determined in the laboratory. Twenty-eight-day exposure of fish 150-225 mm and 350-400 mm long to 75 parts per trillion (ng/liter) dieldrin resulted in the larger catfish consistently accumulating more dieldrin than the smaller fish. After 28 days of elimination, dieldrin levels in both size groups were nearly equal. Catfish exposed to 2 ppm (mg/kg) dieldrin through their diets accumulated significantly more dieldrin in muscle than did fish exposed to 75 pptr in water. When fish were exposed to dieldrin both in food and water, dieldrin from both sources contributed to the total dieldrin load. Large catfish accumulated more dieldrin from food and water than did smaller catfish. After 28 days of elimination, levels of dieldrin were not significantly different in muscles of 150-225 mm and 350-440 mm catfish exposed via both food and water.
Animal Feed↗
Questioning inbreeding: Could outbreeding affect productivity in the North African catfish in Thailand?
The North African catfish (Clarias gariepinus) is a significant species in aquaculture, which is crucial for ensuring food and nutrition security. Their high adaptability to diverse environments has led to an increase in the number of farms that are available for their production. However, long-term closed breeding adversely affects their reproductive performance, leading to a decrease in production efficiency. This is possibly caused by inbreeding depression. To investigate the root cause of this issue, the genetic diversity of captive North African catfish populations was assessed in this study. Microsatellite genotyping and mitochondrial DNA D-loop sequencing were applied to 136 catfish specimens, collected from three populations captured for breeding in Thailand. Interestingly, extremely low inbreeding coefficients were obtained within each population, and distinct genetic diversity was observed among the three populations, indicating that their genetic origins are markedly different. This suggests that outbreeding depression by genetic admixture among currently captured populations of different origins may account for the low productivity of the North African catfish in Thailand. Genetic improvement of the North African catfish populations is required by introducing new populations whose origins are clearly known. This strategy should be systematically integrated into breeding programs to establish an ideal founder stock for selective breeding.
Animals↗
Edwardsiella tarda in freshwater catfish and their environment.
Edwardsiella tarda was isolated from 47, 88, and 79% of skin, visceral, and dressed-fish samples, respectively. This species was also isolated from 30% of imported dressed fish, 75% of catfish pond water samples, 64% of catfish pond mud samples, and 100% of frogs, turtles, and crayfish from catfish ponds. The incidence of Edwardsiella increased during the summer months, as water temperatures increased. Of several isolation media evaluated, the most effective was selective enrichment in double-strength Salmonella-Shigella broth and subsequent plating on single-strength Samonella-Shigella agar. The significance of the incidence of Edwardsiella in catfish, catfish disease, and public health could not be substantiated.
Animals↗
Identification and properties of J chain isolated from catfish macroglobulin.
After the cleavage of disulfide bonds of macroglobulin isolated from channel catfish (Ictalurus punctatus), an electrophoretically fast-moving polypeptide, which resembled human J chain, was released. On a Sephadex G-200 column equilibrated in 5 M guanidine, the elution position of the J chain overlapped with the descending part of the L chain peak. Further purification was achieved by DEAE ion-exchange chromatography. The isolated polypeptide, which had a molecular weight of 14,800 +/- 500, as determined ultracentrifugally by sedimentation equilibrium in 5 M guanidine, contained 7% carbohydrate with one residue of fucose, two of mannose, one of galactose, two of glucosamine, and one of sialic acid per chain. A comparison of catfish and human J chain amino acid analyses showed the former to have a higher content of serine, glycine, and phenylalanine and a lower content of aspartic acid, isoleucine, and arginine. Tryptic peptide maps of catfish and human J chains revealed very few common peptides. Rabbit and guinea pig antisera to human J chain did not cross-react with catfish J chain. Untreated, resuced and alkylated, S-sulfonated, or cyanogen bromide cleaved macroglobulin from the gar (Lepisosteus osseus) contained no polypeptide analogous to either catfish or human J chain by the criteria employed in this study.
Acetates↗
Lipogenic activity of catfish liver. Lack of response to dietary changes and insulin administration.
1. Some of the physical, chemical and kinetic properties of catfish liver lipogenic enzymes (acetyl-CoA carboxylase and fatty acid synthetase) were investigated. 2. The liver lipogenic enzymes of catfish exhibited maximal activity at 37 degrees C, even though these fish usually live at temperatures not above 24 degrees C. 3. The activity of the lipogenic enzymes of catfish liver was always low, regardless of the proportions of lipids or carbohydrates in the diet and could not be raised by insulin administration. 4. Under the conditions of the experiments, catfish liver fatty acid synthetase produced more stearate than palmitate and no myristate.
Acetyl-CoA Carboxylase↗
Adaptive Evolution of the PFK Gene Family in Chinese Longsnout Catfish, Leiocassis longirostris.
The Chinese longsnout catfish is a typical carnivorous fish with a relatively weak ability to utilize glucose. However, the genomic basis for its glucose metabolic adaptation remains unclear. In this study, we used comparative genomics methods to systematically analyze the evolutionary characteristics of glucose metabolism-related genes in the Chinese longsnout catfish, focusing on gene family evolution, patterns of expansion and contraction, and selective pressures. The results indicate that glucose metabolism-related genes have undergone significant reshaping during evolution. Genes involved in glucose digestion, absorption, and insulin signaling pathways demonstrate a tendency toward contraction, while those associated with protein and lipid metabolism exhibit expansion. This pattern is consistent with the species' long-term adaptation to a high-protein, high-fat diet. Comparative analysis further revealed that, compared to fish with different dietary habits, certain key genes involved in glycolysis in the Chinese longsnout catfish exhibit a reduction in copy number. Molecular evolutionary analysis showed that key genes involved in glycolysis and gluconeogenesis (including hexokinase 2 (hk2), phosphofructokinase, muscle/platelet (pfkm/p)) exhibit signs of accelerated evolution or positive selection. Notably, the PFK gene family exhibits complex evolutionary characteristics resulting from the combined effects of gene contraction, rapid evolution, and positive selection. In summary, this study reveals the genomic evolutionary basis for the glucose metabolic adaptation of the Chinese longsnout catfish and identifies the PFK gene family as a key candidate for elucidating its unique glucose metabolic characteristics.
Leiocassis longirostris↗
Isolation and partial purification of catfish pancreatic islet messenger RNA.
Poly(a)-rich mRNA has been isolated from catfish pancreatic islet total nucleic acid. Cell-free translation of the mRNA by wheat germ extracts yielded a protein of 11 000-12 000 molecular weight, estimated by sodium dodecyl sulfate-urea polyacrylamide gel electrophoresis. This peptide is larger than catfish proinsulin, but contains tryptic peptides of proinsulin. Its synthesis comprises up to 23% of the cell-free product, depending on the conditions of cell-free synthesis. Synthesis is inhibited by 7-methylguanosine 5'-monophosphate suggesting the presence of a 7-methylguanosine cap on the 5' end of catfish proinsulin mRNA. Sucrose gradient centrifugation of the islet poly(A)-rich mRNA yielded 8S and 12S peaks. These fractions were translated with wheat germ extracts and it was determined that over 60% of the islet mRNA-dependent protein from the 8S fraction was preproinsulin. The 8S mRNA fraction was electrophoresed on 3% agarose-6 M urea gels and demonstrated to be several bands, ranging from 100 000-200 000 molecular weight.
Animals↗
gamma-Aminobutyric acid: a neurotransmitter candidate for cone horizontal cells of the catfish retina.
In the catfish retina, horizontal cells that receive inputs exclusively from red-sensitive cones are the only neurons that accumulate exogenous gamma-aminobutyric acid under our experimental conditions. When isolated eyecups are perfused with bicuculline methochloride, an antagonist of postsynaptic gamma-aminobutyric acid receptors, responses of cone photoreceptors to a field of light (3 mm in diameter) become much slower and approach those to a small spot of light (0.3 mm). In addition, bicuculline methochloride decreases the frequency responses of cone horizontal cells to a field of light. These findings indicate that, in the catfish retina, feedback synapses from cone horizontal cells to cones are chemically mediated and may use gamma-aminobutyric acid as a neurotransmitter. Our results also confirm the hypothesis that, in the catfish retina, a function of the negative feedback is to improve the frequency responses of the system.
Action Potentials↗
Residue studies with [14C]fosamine ammonium in channel catfish.
The active ingredient in du Pont Krenite brush control agent is ammonium ethyl carbamoylphosphonate (fosamine ammonium salt, formerly known as DPX-1108). Residues in channel catfish exposed to 1.1 ppm 14C-carbonyl-labeled fosamine ammonium in water for 4 wk were found to plateau in 2-3 wk with an accumulation factor (ratio of residue in fish to residue in water) of less than 1. In a separate experiment channel catfish were placed for 4 wk in a tank containing [14C]fosamine ammonium-treated soil (15 ppm) that had been aged for 30 d prior to flooding and initiation of fish exposure. The residue levels in this latter group of catfish also plateaued in 2-3 wk with an accumulation factor of less than 1. In both experiments, after the 4-wk exposures, the fish were transferred to fresh water for 2-wk depuration periods, during which residue levels dropped 50--90%. No effects on the fish were observed during these experiments.
Animals↗
The influence of dietary fat levels and environmental temperature on digestible energy and absorbability of animal fat in catfish diets.
A study was conducted on the effects of three dietary levels of animal fat (5%, 10%, and 15%) and two environmental temperatures (23 and 28 degrees) on the digestible energy (DE) and apparent absorbability (AA) of animal fat in diets of 150 g catfish. Results obtained by the use of the chromic oxide indicator technique demonstrated that at 28 degrees and substitution levels up to 10% of diet, animal fat had a DE value of 7,000 kcal/kg and an AA of 94%. At the 15% level of substitution, both DE and AA were substantially reduced. At each level of substitution, DE and AA values were considerably lower in fish reared at 23 degrees. At supplemental levels up to 10% of diet, the DE and AA values for catfish at 23 degrees were 6,130 kcal/kg and 70%, respectively. Results from this study reconfirmed previous growth data which indicated that animal fat is an excellent dietary energy source for catfish which are reared at optimum temperatures.
Absorption↗
Morphological and functional identifications of catfish retinal neurons. I. Classical morphology.
The morphology of the catfish horizontal cells is comparable to that in other fish retinas. The external horizontal cells contact cone receptors and are stellate in shape; the intermediate horizontal cells are even more so and contact rod receptors. The internal horizontal cells constitute the most proximal layer of the inner nuclear layer and may possibly be, in reality, extended processes from the other two horizontal cell types. Bipolar cells resemble those in other teleost retinas: the size and shape of their dendritic tree encompass a continuous spectrum ranging from what is known as the small to the large bipolar cells. The accepted definition of amacrine cells is sufficiently vague to justify our originating a more descriptive and less inferential name for the (axonless) neurons in the inner nuclear layer which radiate processes throughout the inner synaptic layer. These starbust and spaghetti cells vary considerably in the character and extent of their dendritic spread, but correlates exist in other vertebrate retinas. Ganglion cells are found not only in the classical ganglion layer but displaced into the inner nuclear layer as well. Several types can be distinguished on the basis of cell geometry and by the properties of their dendritic tree. Not all of the categorization corresponds with previous descriptions; our findings suggest that some reorganization may be necessary in the accepted classification of cells in the proximal areas of the vertebrate retina. A subtle yet remarkable pattern underlies the entire structure of the catfish retina; there exists a definite gradient of size within a particular class of cells, and of configuration among the subclasses of a specific cell type. It remains to be seen if these morphological spectra bear any functional consequences. The fact that the structure of the catfish retina most closely resembles those of other phylogenetically ancient animals, such as the skate and the dogfish shark, testifies to its primitive organization; morphological and functional mechanisms discernible in this simple system may, therefore, be applicable to the retinas of higher ordered vertebrates.
Animals↗
[Orientation of the catfish in uniform and nonuniform electric fields].
Experiments with conditioning revealed that catfish showed compass orientation with precision about 20 degrees using a direction of homogeneous horizontally directed weak electric field with current density of 1.5 . 10(-11) A/mm2 in water with a specific resistance of 15 Ohm-m. Similar fields occur in their habitat. The catfish used the current density gradient for directed movements in the unhomogenous field. The lowest current density gradient in which the catfish showed the orientation behaviour proved to be 3.6 x 10(-12) A/mm2 per 1-mm distance. The possible mechanism of electro-orientation and its functional significance, are discussed.
Animals↗
Genome-wide identification, structural characterization, and evolutionary analysis of growth-related gene families in African catfish (Clarias gariepinus).
The somatotropic axis encompassing growth hormone (GH), insulin-like growth factor (IGF), myostatin (MSTN), and prolactin (PRL) signalling cascades is the master regulator of somatic growth, metabolism, and development in vertebrates. African catfish (Clarias gariepinus), a commercially pivotal aquaculture species, now possesses a chromosome-level reference genome (CGAR_prim_01v2); however, a systematic, genome-wide characterization spanning all five interconnected growth-related gene families has not previously been undertaken in this species. Here, we identified and characterized 15 growth-related genes spanning gh1, ghra, ghrb, Igf1, Igf2a, Igf2b, igf1ra, Igf1rb, Igf2r, Mstna, Mstnb, prl, prlra, prlrb, and smtlb distributed across 13 chromosomes. Complete one-to-one orthology with zebrafish confirmed strong dosage-balance conservation across >120 million years of teleost divergence. Physicochemical analysis resolved a clear biochemical dichotomy between compact, basic secreted ligands (19.88-45.81 kDa; pI up to 10.02) and large, acidic, heavily glycosylated membrane receptors (56.82-270.80 kDa; pI 4.85-5.97). Phylogenetic analysis confirmed 3R whole-genome duplication origins for all paralog pairs, while synteny analysis revealed a disruption of the ancestral gh1-prl chromosomal block in C. gariepinus, a finding that warrants further comparative and functional investigation. This genomic atlas provides the sequence and structural information including exon-intron boundaries, domain architecture, and chromosomal coordinates needed as a prerequisite for future marker-assisted selection and CRISPR-based myostatin-editing efforts in African catfish aquaculture, though translation into applied breeding outcomes will require subsequent functional and expression studies.
Animals↗
The distribution of the olfactory tracts in the bullhead catfish, Ictalurus nebulosus.
Using degeneration staining methods, central projections of the olfactory tracts in the bullhead catfish, Ictalurus nebulosus were studied. Seporate lesions were made of the lateral and medial olfactory tracts in an attempt to separate their zones of projection. Three major terminal fields were found: lateral, medial and central-posterior complex. Two additional minor projections were seen: interbulbar and hypothalamic. The lateral division of the olfactory tract terminates in lateral, central and hypothalamic terminal fields. The medial tract projects to lateral, meedial, posterior and hypothalamic fields. All terminal fields were found bilaterally; the lateral tract partly crossing in both the anterior commissure. A small intellbulbar commissure was also found to contain medial tract fibers. Evidence is given to show that the anterior olfactory nucleus, if present in catfish, may be located within the olfactory bulb itself. Similarities between mammalian and teleost olfactory systems are also discussed.
Animals↗
Biochemical studies of taste sensation. VII. Enhancement of taste stimulus binding to a catfish taste receptor preparation by prior exposure to the stimulus.
The taste receptor membrane fraction (Fraction P2) was prepared from a homogenate of the taste tissue of the channel catfish Ictalurus punctatus. This included the rostral, dorsal, and dorsolateral surfaces of the catfish in addition to those of the barbels. The yield of Fraction P2 is 4-7 mg protein from an individual fish, with a purification averaging 8- to 15-fold over that of the crude whole homogenate and essentially quantitative recovery of binding activity in Fraction P2. Treatment of Fraction P2 in vitro with a high concentration of the taste stimulus molecule L-alanine led to a several-fold enhancement of binding activity. Enhancement of the binding of 3H L-alanine was observed after treatment with unlabeled 10 mM L-alanine and removal of the L-alanine by washing. Enhancement occurred whether the preparation was stored frozen (-65 degrees C) for an extended period in the presence of the L-alanine, or merely exposed to it in the cold without freezing. D-Alanine enhanced the binding activity of 3H L-alanine to about 60% of the level induced by L-alanine. Nonspecific binding of 3H L-alanine was unaffected by the treatment. Scatchard analyses of saturation curves for binding of 3H L-alanine to freshly prepared Fraction P2 and to L-alanine-treated Fraction P2 revealed no change in the KD value, but a several-fold increase occurred in the amount bound. Binding activity is operationally defined. Because the enhancement observed here is reminiscent of an increase in transport due to a countertransport effect, further studies were carried out to examine whether the phenomenon reflects transport or true binding. The measured binding was not increased in the presence of Na+, indicating that it is not due to an Na+-coupled transport of L-alanine. When Fraction P2 was preloaded with L-alanine (10(-6)--10(-2) M) prior to assay, no stimulation of binding was observed; instead, binding decreased. This result is consistent with a true binding phenomenon but not with a carrier-mediated transport process to explain the enhancement phenomenon. Binding assays carried out over a range of osmolarities revealed decreased binding at high osmotic strengths, suggesting that a significant portion of the ligand might be contained in vesicles. It is postulated that "hidden" or "buried" receptor sites exist in the Fraction P2 as isolated, and that these are exposed upon perturbation of the membrane structure by a high ligand concentration.
Alanine↗
Optimum dietary protein to energy ratio for channel catfish fingerlings, Ictalurus punctatus.
Twenty-one semipurified diets were formulated to determine the optimum protein:energy ratio (P/E) for channel catfish fingerlings. Seven crude protein levels and three energy levels at each protein level were utilized. The protein, lipid, and digestible carbohydrate sources were hexane-extracted whole egg powder, salmon-corn oil mixture, and white dextrin, respectively. After an initial 2 week conditioning period, the experimental diets were fed in triplicate to groups of 30 +/- 3 channel catfish fingerlings weighing 205 +/- 10 g and kept in 110 liter flow-through aquaria at 26.7 +/- 1.1 degrees. The diets were fed at a rate equalling 3% of the total wet body weight/day divided into three equal feedings and adjusted weekly for 9 weeks. An approximate fivefold increase in body weight was observed. These data indicate that the concept of P/E ratios must be restricted to diets containing adequate levels of protein and total energy. Based on average daily gain, diets containing energy levels between 275 and 341 kcal/100 g had an optimum P/E ratio of approximately 88 (24-36% crude protein). Diets containing 24% crude protein and 275 kcal/100 g diet appeared to be utilized more efficiently in terms of percent protein deposited than diets containing higher crude protein levels.
Animals↗