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Geology topics

S. D. McCormick

Publications and source records attributed to S. D. McCormick.

64 records · Page 4Linked to original sources
USGS1994

Ontogeny and evolution of salinity tolerance in anadromous salmonids: Hormones and heterochrony

Use of estuaries and oceans by salmonids varies greatly, from no use in nonanadromous species, to movement toward the sea soon after hatching and emergence in some Pacific salmon. This variation is accompanied by large differences in the ontogeny of salinity tolerance among salmonids. Some species acquire increased salinity tolerance early in development, whereas others develop this characteristic much later, indicating there is a heterochrony (change in timing) in the development of salinity tolerance in salmonids. The basic physiological mechanisms for ion regulation in seawater (such as increased gill chloride cells, gill Na + ,K + -ATPase activity, membrane permeability, and drinking rate) are common to all salmonids. What determines the differences in salinity tolerance among the salmonids is not the basic mechanisms for salt secretion but the environmental and ontogenetic control of these mechanisms. In salmonids such as pink and chum salmon that enter seawater soon after emergence, acclimation to seawater may be controlled largely by internal (ontogenetic) information. In smolting salmonids that acquire increased salinity tolerance 1–2 yr after hatching, photoperiod is the dominant environmental cue. In nonsmolting species that migrate 2–3 yr after hatching, salinity itself may be the primary stimulus for salt secretory mechanisms. Physiological changes triggered by developmental and environmental cues are mediated by endocrine factors. Treatments with cortisol, growth hormone, and insulin-like growth factor I have been shown to increase seawater tolerance of salmonids, whereas prolactin is inhibitory. Differences in developmental patterns of endocrine activity (such as secretion, binding proteins, and receptors) are hypothesized to be responsible for the differences in timing (heterochrony) of increased salinity tolerance among and within salmonid species.

Estuaries↗
USGS1993

Effects of salinity on chloride cells and Na+ K+-ATPase activity in the teleost Gillchthys mirabilis

1. Longjawed mudsuckers, Gillichthys mirabilis , in 30ppt seawater (SW) were transferred to 1.5, 30 and 60ppt SW. 2. In the first 1–3 days after transfer, plasma chloride level and plasma osmolarity rose in the 60ppt SW fish, and decreased in the 1.5ppt SW fish. 3. By day 21, however, plasma chloride and osmolarity were at or near the levels seen in the controls (30ppt). 4. Branchial and jawskin Na + , K + -ATPase activities were high in all salinities, and did not differ significantly among treatments. 5. The vital fluorescent stains DASPEI and anthroylouabain were used to detect mitochondria and Na + , K + -ATPase, respectively, in chloride cells. 6. Both stains indicated that jawskin chloride cell density did not differ among treatment groups. 7. In contrast, chloride cell size increased significantly with increasing salinity. 8. The chloride cells of fish in 60 ppt SW were noticeably angular in outline, whereas those of both the 1.5 and 30ppt SW fish were circular. 9. The results are discussed in relation to the ion transport requirements encountered in the intertidal habitat of the mudsucker.

Comparative Biochemistry and Physiology, Part A: P↗
USGS1992

Stimulation of coho salmon growth by insulin-like growth factor I

The effect of insulin-like growth factor I on growth rate of coho salmon ( Oncorhynchus kisutch ) was examined. Juvenile coho salmon received implants of osmotic minipumps containing recombinant bovine insulin-like growth factor I (rbIGF-I) or saline for a period of 3 to 4 weeks. High doses of rbIGF-I (>0.13 μg · g −1 · d −1 ) resulted in hypoglycemia and death. In 2-year-old coho salmon, 0.09 μg · g −1 · d −1 rbIGF-I administered for 25 days doubled linear growth rate and increased growth rate in weight by 40%. In rapidly growing, 1-year-old coho salmon, growth rate was not altered by rbIGF-I at 0.01 or 0.05 μg · g −1 · d −1 for 31 days. In ration-limited fish exhibiting slow growth in the control group, rbIGF-I (0.02 to 0.12 μg · g −1 · d −1 ) increased linear growth rate by up to threefold and growth rate in weight by up to fourfold. The results indicate that exogenous treatment with mammalian IGF-I can stimulate coho salmon growth under some conditions, and that endogenous IGF-I may be an important factor in regulating growth of teleosts.

General and Comparative Endocrinology↗
USGS1991

Effects of prolacton chloride cells opercular membrane of seawater-adapted tilapia

Effects of prolactin on morphology and numbers of chloride cells in the opercular membrane of seawater-adapted tilapia ( Oreochromis mossambicus ) have been examined. Following five daily injections of ovine prolactin at a dose of 10 μg · g body wt −1 , blood samples were taken and opercular membranes were removed and stained with a fluorescent mitochondrial dye (dimethylaminostyrylethylpyridiniumiodine), a fluorescent derivative of ouabain (anthroylouabain), and a histological stain specific for the extensive tubular system of chloride cells (zinc-osmium-iodine). Mean plasma osmolarity and sodium increased 23–24% following prolactin injection. An increase in the relative frequency of chloride cells between 20 and 180 μm 2 in cross-sectional area and a decrease in the relative frequency of chloride cells greater than 180 μm 2 were observed following prolactin injections. Average cell size decreased 46–70% and cell height decreased 26–38% following prolactin injections. There was no significant change in cell density. Anthroylouabain staining was observed in both prolactin- and saline-injected fish, and no significant effect on Na + ,K + -adenosinetri-phosphatase activity was seen in either opercular membrane or gill tissue. The results demonstrate an effect of prolactin on chloride cell size and provide a morphological correlate for decreased secretory activity of chloride cells following prolactin injections.

General and Comparative Endocrinology↗
USGS1991

Developmental differences in the responsiveness of gill Na+, K+ and -ATPase to cortisol salmonids

The ability of cortisol to increase gill Na + , K + -ATPase activity was examined in several salmonid species during development. Coho salmon ( Oncorhynchus kisutch ) parr were unresponsive to cortisol in vitro (10 μg/ml for 2 days) in November. Responsiveness was significant from January to March, peaking in January just prior to seasonal increases in gill Na + , K + -ATPase activity. Gill tissue became unresponsive to in vitro cortisol in April when in vivo gill Na + , K + -ATPase activity peaked. The ability of cortisol to stimulate gill, Na + , K + -ATPase activity in postemergent fry (2–3 months after hatching) was examined in chum ( O. keta ), chinook ( O. tschawytscha ), coho, and Atlantic salmon ( Salmo salar ). Initial levels of gill Na + , K + -ATPase activity were elevated in chum salmon, which normally migrate as fry. Cortisol (10 μg/ml for 4 days in vitro ) increased gill Na + , K + -ATPase activity in chum salmon fry (48% above initial levels), had a limited but significant effect in chinook salmon fry, and had no effect in coho and Atlantic salmon fry. In an in vivo experiment, Atlantic salmon previously exposed to simulated natural photoperiod (SNP) and continuous light (L24) received four cortisol injections of 2 μg · g −1 every third day. SNP fish responded with increased gill Na + , K + -ATPase activity (+66%), whereas L24 fish were not affected. Atlantic salmon presmolts with initially low levels of gill Na + , K + -ATPase activity responded to cortisol in vitro , whereas smolts with initially high levels of gill Na + , K + -ATPase activity were unresponsive. Triiodothyronine (0.01–10 μg/ml), prolactin (0.1–10 μg/ml), growth hormone (0.1–10 μg/ml), insulin (0.01–10 μg/ml), and bovine insulin-like growth factor I (0.01–1 μg/ml) did not affect gill Na + , K + -ATPase activity in vitro , individually or with cortisol (1–10 μg/ml). Thus, changes in responsiveness to cortisol occur during salmonid development, vary among species, and may be important in the heterochrony that characterizes the parr-smolt transformation.

General and Comparative Endocrinology↗
USGS1991

Osmoregulatory actions of insulin-like growth factor-I in rainbow trout (Oncorhynchus mykiss)

The ability of insulin-like growth factor-I (IGF-I), insulin and GH to promote hypoosmoregulatory ability was examined in juvenile rainbow trout ( Oncorhynchus mykiss ). Following adaptation to 12 parts per thousand (p.p.t.) seawater for 5 days, fish were given a single injection of hormone or vehicle, then exposed to 29 p.p.t. for 24 h and examined for changes in plasma osmolarity, ions and glucose. Ovine GH (oGH; 0·2 μg/g) significantly improved the ability of rainbow trout to maintain plasma osmolarity and sodium levels following transfer to 29 p.p.t. seawater. Recombinant bovine IGF-I (0·01, 0·05 and 0·2 μg/g) also improved the hypoosmoregulatory ability of trout; the effect being dose-dependent and greater than that of oGH. Bovine insulin (0·01, 0·05 and 0·2 μg/g) had no statistically significant effect on plasma ions. The results indicate that IGF-I is a potential mediator of the action of GH in seawater adaptation of salmonids.

Journal of Endocrinology↗