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Geology topics

K. B. Davis

Publications and source records attributed to K. B. Davis.

17 recordsLinked to original sources
USGS2007

Induction of triploidy and tetraploidy in Nile tilapia, Oreochromis niloticus (L.)

Induction of triploidy and tetraploidy in Nile tilapia, Oreochromis niloticus , was investigated by heat shock, cold shock, hydrostatic pressure, and/or chemicals (cytochalasin A, B, and D). Additionally, efficacy of combined protocols was determined. Heat shock 10 min after fertilization induced triploidy when incubation temperature was 24 C but not when incubation temperature was 31 C. Heat shock of 40–41 C at 4–6 min after fertilization was effective in inducing up to 100% triploidy with hatchability similar to controls. Cold shock at 13 C for 45 min five min after fertilization induced 85–100% triploids. Heat shock and multiple heat shocking were the most effective treatments for the induction of tetraploidy. Two heat treatments of 41 C applied at 65 and 80 min after fertilization for 5 min each produced approximately 80% tetraploidy in hatched fry. Immersion of fertilized eggs in cytochalasin A, B, or D at concentrations up to 10 μg/L applied at various times and durations was ineffective in inducing triploidy or tetraploidy.

Journal of the World Aquaculture Society↗
USGS2006

Growth, body composition and hepatic tyrosine aminotransferase activity in cortisol-fed channel catfish, Ictalurus punctatus Rafinesque

Metabolic consequences of chronic elevation of cortisol in the diet of yearling channel catfish, Ictalurus punctatus , were studied. Cortisol was incorporated into the diet in concentrations of 1, 10, 50 and 100 μg/g of food. This diet was offered at 3% of the body weight per day for 10 weeks. Fish were individually weighed and measured at 2-week intervals and feeding rates were adjusted. Body weight, liposomatic index and condition factor were significantly lower and food conversion was significantly higher in fish fed 50 or 100 μng cortisol/g of food when compared with controls. The hepatosomatic index of fish fed cortisol at the rate of 100 μg/g of food decreased significantly. Specific activity of hepatic tyrosine aminotransferase was significantly higher at the two highest cortisol doses. Long-term cortisol administration can reduce growth and condition factor by activating gluconeogenic mechanisms in which lipids and amino acids, rather than carbohydrates, are used for energy production. The metabolic effects of exogenous cortisol in this study offer an explanation for the decreased growth of fish under conditions that activate the secretion of endogenous cortisol.

Journal of Fish Biology↗
USGS1986

Environmental regulation and influence of the eyes and pineal gland on the gonadal cycle and spawning in channel catfish (Ictalurus punctatus)

Blinded, pinealectomized, or blinded and pinealectomized female channel catfish ( Ictalurus punctatus ) were placed with normal (unoperated on) control fish in outdoor tanks at constant temperature (21 ± 2 C) or earthen ponds (ambient conditions) in February or August, when they were 21 or 27 mo old. Fish were sampled through the following reproductive season. The gonadosomatic index (GSI) and plasma estrogen concentration changed seasonally in 3-yr-old fish, but the changes were less marked or lacking in 2-yr-olds. The GSI levels of sexually mature (≥3 years old) fish peaked about a month earlier in the tanks than in the ponds; the estrogen peak for fish in the tanks was lower than that for pond fish. All experimental fish (both ages) in ponds delayed ovarian resorption for about 1 mo, compared with normal control fish. Exposure to constant 21 C water allowed earlier gonadal recrudescence. All groups of sexually mature fish that were surgically altered in August spawned during the following spring. Fish with eyes spawned earlier and had higher spawning percentages (control 68%, pinealectomized 75%) than did fish without eyes (blinded 50%, blinded and pinealectomized 56%). Neither the eyes nor the pineal is essential for spring gonadal maturation or for spawning in channel catfish, but one or both may have a role in timing these events. An annual internal oscillator that may be modified by environmental temperature is suggested as the primary control of reproductive cycling in the species. Light information obtained through the pineal, eyes, or both appears to affect the time of gonadal resorption.

Ecological and Evolutionary Physiology↗
USGS1986

Plasma corticosteroid stress response of fourteen species of warmwater fish to transportation

Plasma corticosteroid concentrations were measured in 14 species of fish immediately after they were electrofished from reservoirs on the Alabama River and after they had been transported for 2 h. There was no corticosteroid response in spotted gars Lepisosteus oculatus. Bowfins Amia calva, longnose gars Lepisosteus osseus, and freshwater drums Aplodinotus grunniens had only small corticosteroid increases (14–39 ng/mL) during transportation. Corticosteroids increased by intermediate amounts (59–184 ng/mL) during transportation in blue catfish Ictalurus furcatus, paddlefish Polyodon spathula, largemouth bass Micropterus salmoides, channel catfish Ictalurus punctatus, river carpsuckers Carpiodes carpio, white bass Morone chrysops, striped bass Morone saxatilis, and crappies Pomoxis sp. The greatest increases were 223 ng/mL in gizzard shad Dorosoma cepedianum and 286 ng/mL in common carp Cyprinus carpio. Spotted and longnose gars, largemouth bass, and common carp also were held in tanks for about 2 months at 21°C and then stressed by confinement in a dip net for 30 min. The confinement caused significant increases (P < 0.01) of plasma corticosteroid concentration in all four species. Dip‐net confinement appears to be a useful method for comparing corticosteroid responses among species of warmwater fish.

Transactions of the American Fisheries Society↗
USGS1984

Biotic and abiotic influences on corticosteroid hormone rhythms in channel catfish

Plasma‐corticosteroid concentrations in resting channel catfish Ictalurus punctatus held at 21 C varied only slightly during a 24‐hour period; further, increases in hormone concentrations induced by confinement stress were independent of time of day and photoperiod. Temperature strongly affected both resting corticosteroid concentrations and the dynamics of hormone secretion when fish were stressed. Resting concentrations were greatest in fish acclimated to 5 and 10 C (25–29 ng/ml), sharply lower in fish held at 15, 20, or 21 C (5–9 ng/ml), and intermediate in fish maintained at 25, 30, or 35 C (12–13 ng/ml). Hormone concentrations increased when fish were stressed by confinement. Corticosteroid concentrations hardly changed in fish held at 5 or 10 C, but increased markedly in fish at higher temperatures; in addition the response was more delayed at the lower temperatures.

Transactions of the American Fisheries Society↗
USGS1983

Plasma corticosteroid and chloride dynamics in rainbow trout, Atlantic salmon, and lake trout during and after stress

Levels of plasma corticosteroids and chloride were studied in rainbow trout ( Salmo gairdneri ), lake trout ( Salvelinus namaycush ), and Atlantic salmon ( Salmo salar ) after 6 h of confinement in a shallow dipnet. Plasma corticosteroids increased more sharply in rainbow trout than in the other species during the confinement, and returned to resting levels more slowly. Plasma chloride levels decreased significantly from resting levels in both rainbow trout and Atlantic salmon confined for 6 h and had not recovered 12 h after release from the dipnet; very little effect was observed in lake trout. Both plasma corticosteroid and chloride dynamics appear to vary widely in closely related species. The differences do not appear to be related to ease of maintaining the species in captivity.

Aquaculture↗
USGS1983

Feminization of channel catfish by oral administration of steroid sex hormones

Oral administration of 17‐β‐estradiol or 17‐α‐ethynyltestosterone to sexually undifferentiated channel catfish Ictaturus punctatus during the first 21 days after yolk‐sac absorption resulted in the production of 100% females. The androgen was effective at doses of 6 to 600 μg/g of feed, but not at 0.6 μg/g.

Transactions of the American Fisheries Society↗
USGS1982

Plasma corticosteroids and chlorides in striped bass exposed to tricaine methanesulfonate, quinaldine, etomidate, and salt

Plasma chloride and corticosteroid concentrations were measured in yearling striped bass (Morone saxatilis) exposed to 25 mg/L tricaine methanesulfonate, 2.5 mg/L quinaldine, or 0.1 mg/L etomidate (an experimental drug), alone and in combination with 10 g/L salt (NaCl). Plasma chloride levels were unaffected in all treatments during a 15‐min exposure and during a 10‐min period of close confinement in a dipnet. Plasma corticosteroids increased in fish exposed to salt alone and in fish exposed to tricaine methanesulfonate or quinaldine, either alone or in combination with salt. Etomidate alone or combined with salt limited the increase in plasma corticosteroids during exposure and confinement. Etomidate appears to be a useful drug for suppressing physiological changes during the handling and transportation of striped bass.

Progressive Fish-Culturist↗
USGS1980

Effects of environmental pH and calcium on ammonia toxicity in channel catfish

The twenty-four-hour median lethal concentrations (24-hour LC50) of total ammonia nitrogen (TA-N) to channel catfish (Ictalurus punctatus) at pH 7, 8, and 9 (total hardness, 40 mg/liter; temperature, 21&ndash;25 C) were 263.6 &plusmn; 11.3 (SE), 38.8 &plusmn; 1.8, and 4.5 &plusmn; 0.2 mg/liter, respectively. The 24-hour LC50 of un-ionized ammonia nitrogen (UIA-N) concentration at pH 8 was significantly higher (1.82 &plusmn; 0.06 mg/liter) than at pH 7 or 9 (1.39 &plusmn; 0.06 and 1.49 &plusmn; 0.12 mg/liter). Enrichment of the water to 440 mg/liter total hardness at pH 7 significantly increased the 24-hour LC50 of TA-N and UIA-N (356.3 &plusmn; 16.4 and 1.79 &plusmn; 0.07). Fish exposed to 25 mg/liter TA-N for 12 hours at pH 7 and 8 showed no differences from control fish in hematocrit, percent total plasma protein, or plasma and muscle chloride. Plasma sodium showed no difference between control and experimental groups at pH 7; however, a significant decrease occurred in fish exposed to 25 mg/liter TA-N at pH 8. No differences in blood pH were found between the control groups and fish exposed to 100 and 200 mg/liter TA-N at pH 7, and to 10 and 25 mg/liter TA-N at pH 8. Plasma sodium depletion is suggested as a contributing mechanism of ammonia toxicity.

Transactions of the American Fisheries Society↗
USGS1980

Inhibition of nitrite-induced toxicity in channel catfish by calcium chloride and sodium chloride

Environmental chloride has been shown to inhibit methemoglobin formation in fish, thereby offering a protective effect against nitrite toxicity. Channel catfish (Ictalurus punctatus) were simultaneously exposed to various environmental nitrite and chloride levels (as either CaCl 2 or NaCl) in dechlorinated tap water (40 mg/L total hardness, 47 mg/L alkalinity, 4 mg/L chloride, pH = 6.9-7.1, and temperature 21-24&deg;C). Methemoglobin levels in fish simultaneously exposed to 2.5 mg/L nitrite and up to 30 mg/L chloride as either CaCl 2 or NaCl were similar but significantly lower than in unprotected fish. Exposure to 10 mg/L nitrite and 60 mg/L chloride resulted in methemoglobin levels similar to those of the controls; most unprotected fish died. Fish exposed to 10 mg/L nitrite had significantly lower methemoglobin levels when protected with 15.0 mg/L chloride as CaCl 2 than with NaCl. Fish exposed to nitrite in the presence of 60 mg/L chloride (as either CaCl 2 or NaCl) had similar 24-h LC50 values that were significantly elevated above those obtained in the absence of chloride. Calcium had little effect on tolerance to nitrite toxicity in channel catfish in contrast to its large effect reported in steelhead trout (Salmo gairdneri).

Progressive Fish-Culturist↗
USGS1979

Chloride inhibition of nitrite-induced methemoglobinemia in channel catfish (Ictalurus punctatus)

Exposure of channel catfish (Ictalurus punctatus) fingerlings for 24?h to 1.0, 2.5, and 5.0?mg/L nitrite (pH?=?7; hardness?=?40?mg/L; temperature?=?22&ndash;25 &deg;C) produced methemoglobin levels of 20.7?&plusmn;?1.9%, 59.8?&plusmn;?1.9%, and 77.4?&plusmn;?1.4% (SE), respectively. However, methemoglobin levels were not elevated when fish were simultaneously exposed to 1.0, 2.5, and 5.0?mg/L nitrite and 25, 50, and 100?mg/L sodium chloride, respectively. Acclimation to sodium chloride for 24?h before exposure to nitrite did not enhance the inhibitory action of sodium chloride. Fish exposed to 5?mg/L nitrite for 5?h developed 42.5?&plusmn;?3.8% methemoglobin. When transferred to water containing 5?mg/L nitrite and 250?mg/L sodium chloride, methemoglobin levels returned to normal within 24?h. Environmental chloride probably inhibits methemoglobin formation by competing with nitrite for entrance into the gills of the fish. An ionic ratio of 16 Cl - to 1 NO 2 - is capable of complete suppression of nitrite-induced methemoglobin formation. Bicarbonate ion present in the test water (1?meq/L) may also have contributed to the inhibitive action of chloride.

Journal of the Fisheries Research Board of Canada↗