Inter lake comparison of liver morphology and in vitro hepatic monodeiodination of L-thyroxine in sexually mature coho salmon, Oncorhynchus kisutch Walbaum, from Lakes Erie, Ontario, Michigan and Superior

The hepatosomatic index (HS1) of female sexually mature coho salmon, Oncorhynchus kisutch , from Lake Superior was significantly higher (P<0.01) than in males, whereas that of females from Lake Erie was significantly lower (P<0.05) than in males; there was no significant sex differences in coho salmon from Lakes Ontario or Michigan. Hepatic nuclear areas (HNA) were significantly higher ( P <0.01) in males compared with females in fish collected from Lakes Ontario and Erie, but there was no sex differences in HNA of coho salmon from Lakes Superior or Michigan. In all four lakes, hepatocyte cytoplasmic volume was significantly higher ( P <0.01) in males than in females from the same lake, and the cytoplasmic volume: nuclear volume ratio of males was corresponding significantly higher ( P < 0.05) than in females from the same lake.
Two hepatocytic cell types were evident, termed' light and dark cells, based on the electron density of their cytoplasmic matrix. There were considerable intersex and interlake differences in the relative populations of light 'and dark' cells in coho salmon from Lakes Ontario, Michigan, Erie and Superior, and also in the hepatocytic content of lipid, glycogen, mitochondria and ribosomal and smooth endoplasmic reticulum.
There were no sex differences with regard to in vitro hepatic monodeiodination of L-thyroxine (T4) to triiodo-L-thyronine (T3) in salmon from any of the lakes. However, T4 to T3 conversion was significantly lower (P < 0.05) in liver homogenates prepared from Lake Ontario coho salmon than in comparable preparations of liver from Lake Superior, Lake Erie, or Lake Michigan salmon.     

Seasonal changes in thyroid hyperplasia, serum thyroid hormone and lipid concentrations, and pituitary gland structure in Lake Ontario coho salmon, Oncorhynchus kisutch Walbaum and a comparison with coho salmon from Lakes Michigan and Erie

A progressive fall in serum thyroid hormone levels was found in Lake Ontario coho salmon, Oncorhynchus kisutch , between May 1978 and January 1979 concomitant with an increase in goitre frequency and thyroid hyperplasia. Despite marked differences in overt goitre frequency in sexually mature adult salmon collected from Lakes Ontario (43.7%), Erie (93.5%), or Michigan (0%), serum thyroid hormone levels and thyroid histology were similar in fish from the three lakes. Two gonadotrop-like basophil cells ('globular'and'vacuolar') were found in the pituitary, particularly in sexually maturing and mature adults and'jacks'. Whereas in salmon from Lakes Ontario or Michigan, the globular cells were vacuolated in Lake Erie salmon they were not; this observation may be correlated with the absence of obvious secondary sexual characteristics in Lake Erie salmon. Serum free fatty acids serum, triglycerides and cholesterol concentrations in Lake Ontario salmon fell progressively from the condition in fish collected from the Lake in May 1978, to that of fish collected during their potamodrous migration in November 1978 and January 1979.     

Thyroid function, pituitary structure and serum lipids in Great Lakes coho salmon, Oncorhynchus kisutch Walbaum, 'jacks' compared with sexually immature spring salmon

Whereas spring salmon, Oncorhynchus kisutch , from Lake Ontario had no overt thyroid goiters, comparable Lake Erie spring salmon had a 44% goitre incidence. Goitre incidence in sexually precocious 'jacks' from Lakes Ontario and Michigan was 43–45% and 100% in 'jacks' from Lake Erie.
All fish displayed thyroid hyperplasia. The degree of hyperplasia (as indicated by thyroid follicle colloid content, thyroid follicle size and shape and thyroid follicle epithelial cell size) in Lake Ontario fish tended to be greater in the 'jacks' than in the spring fish; the reverse was true in Lake Erie fish. Serum total L-thyroxine (T4) concentrations in Lake Ontario spring fish were higher than in any other group. There were no differences in serum T, levels between the groups of 'jacks', nor were serum T, levels in 'jacks' and spring salmon from Lake Ontario significantly different. Serum total triiodo-thyronine (T) concentrations in Lake Ontario spring salmon were significantly higher than in all other groups and that in Lake Erie spring salmon greater than in all groups of 'jacks'. Serum T, levels in Lake Ontario 'jacks' were higher than in Lake Erie 'jacks'. Serum free fatty acid (FFA) and cholesterol levels showed significant interlake differences with lower levels present in Lake Erie salmon. Lake Erie 'jacks' appeared to have fewer and less well vacuolated pituitary gonadotropic basophils than 'jacks' from Lakes Michigan and Ontario. Putative thyrotrop cells appeared to be more numerous and more active in the Lake Erie spring salmon compared with Lake Ontario spring salmon. Prolactin, corticotrop and melanotrop cells appeared less active in spring salmon than in the 'jacks'.     

Bioaccumulation of organochlorines by yearling coho salmon (Oncorhynchus kisutch walbaum) fed diets containing Great Lakes' coho salmon, and the pathophysiological responses of the recipients

1. Yearling coho salmon were fed diets containing the flesh of sexually mature adult coho salmon from Lakes Ontario, Erie and Michigan; Pacific Ocean coho salmon and a commercial trout chow were used to prepare control diets. The fish were fed the experimental diets for 27 weeks. Samples were taken of fed fish and fish fed for 27 weeks and then food deprived for 4 weeks. 2. Total accumulated organochlorine in the recipient was directly proportional to dietary total organochlorine levels, although there were considerable interlake differences in the degree of clearance of specific organochlorine compounds. 3. There was evidence of changes in thyroid physiology, hematocrit, liver structure and inter-renal gland activity in recipients fed the Great Lakes' coho salmon, apparently correlated with organochlorine bioaccumulation.     

Individual and seasonal variation in fecal testosterone and cortisol levels of wild male tufted capuchin monkeys, Cebus apella nigritus

This study tested the "challenge hypothesis" and rank-based predictions for temporal steroid production in male tufted capuchin monkeys, Cebus apella. Fecal samples (n = 209) collected from six wild males were analyzed for testosterone and cortisol concentration by enzyme immunoassay. The temporal pattern in male steroid production was compared to female sexual activity and rates of male aggression. The top-ranking adult male did not differ from other adult males in testosterone or cortisol concentration. Mean adult testosterone was significantly higher than mean subadult testosterone throughout the year. There was a clear elevation of testosterone and cortisol in both adult and subadult males during the peak of adult female sexual activity after the birth season. In fact, the magnitude of increase in testosterone was higher than predicted for a species with low male-male aggression. However, there was no difference between nonbreeding baseline testosterone levels during the birth season, and the "breeding" baseline of testosterone in males found during asynchronous female sexual activity. Of all behavioral indices examined, the distribution of female-maintained consortships was the best predictor of mean adult male testosterone concentrations. Although in many species, elevated testosterone coincides with increased male-male aggression, in the present study, the sustained high-magnitude increase in steroids during the peak of adult female sexual activity was associated with a relatively low rate of male-male intragroup aggression.     

Biogenic silica as an estimate of siliceous microfossil abundance in Great Lakes sediments

Biogenic silica concentration (BSi) in sediment cores from the Great Lakes is evaluated as an estimate of siliceous microfossil abundance. A significant linear relationship was found between measured BSi and diatom valve abundance for sediment cores from the Bay of Quinte, Lake Ontario, Lake Erie, Lake Michigan and Lake Superior and between measured BSi and diatom biovolume for Lake Erie, Lake Michigan, and Lake Superior but not for Lake Ontario. Diatom silica predicted from diatom species abundance and an estimated silica content per cell in the Lake Erie cores accounted for 117% and 103% of measured BSi, respectively. By contrast, predicted diatom silica could only account for 28% of measured BSi in the Lake Michigan core and only 25% in the Lake Superior core. A few large diatoms with a large silica content per cell comprised a major portion of predicted diatom silica in all cores. The discrepancy between chemically measured BSi and the silica predicted from diatoms in the Lake Michigan and Lake Superior cores was partially due to the inability of the regression model, used to estimate diatom silica content, to account for different degrees of silicification in the diatom asemblages from the more dissolved silica rich Lake Michigan and Lake Superior.     

Genetic discrimination of wild and hatchery populations of brook charr, Salvelinus fontinalis (Mitchill), in Ontario using mitochondrial DNA analysis

Two brood stocks of brook charr, Sulvelinus fontinalis , are currently maintained by the Ontario Ministry of Natural Resources. The Nipigon brood stock originated from Lake Nipigon, in north-central Ontario, while the Hills Lake stock is believed to have been produced by hybridizing several strains (including charr from a Pennsylvania hatchery as well as charr from Ontario) in the past. The mitochondrial DNA (mtDNA) variability of these brood stocks was characterized using 51 hexanucleotide restriction enzymes. Eleven restriction enzymes, Acc I, Am I, Bun I, Bun II, Hind III, Nco I, Nde I, Nhe I, Nsi I, Pst I and Sph I, were polymorphic between the two brood stocks. Eight hatchery mtDNA haplotypes were detected showing a maximum of 0.41 % sequence divergence. Seven haplotypes are present in the Hills Lake strain, and two in the Nipigon strain. These mtDNA haplotypes are useful markers to determine the degree of reproductive success between planted and native fish. In one comparison in southern Ontario, less than 20% of the wild fish sampled from the head water regions of a small drainage entering Lake Erie could have resulted from random introgression with hatchery fish planted further downstream, because most of these fish possessed a unique Acc 1 cut site. This is one of the few examples in stock analysis studies where such a high degree of genetic discrimination is evident between hatchery and native fish.     

Interspecific habitat associations of juvenile salmonids in Lake Ontario tributaries: implications for Atlantic salmon restoration

Diel variation in habitat use of subyearling Chinook salmon (Oncorhynchus tshawytscha), subyearling coho salmon (O. kisutch), yearling steelhead (O. mykiss), and yearling Atlantic salmon (Salmo salar) was examined during the spring in two tributaries of Lake Ontario. A total of 1318 habitat observations were made on juvenile salmonids including 367 on steelhead, 351 on Chinook salmon, 333 on Atlantic salmon, and 261 on coho salmon. Steelhead exhibited the most diel variation in habitat use and Chinook the least. Juvenile salmonids were generally associated with more cover and larger substrate during the day in both streams. Interspecific differences in habitat use in both streams occurred with Atlantic salmon (fast velocities) and coho salmon (pools) using the least similar habitat. Chinook salmon and Atlantic salmon used similar habitat in both streams. These findings should help guide future management actions specific to habitat protection and restoration of Atlantic salmon in Lake Ontario tributaries.     

Minisatellite DNA variation and stock identification of coho salmon

Geographic variation in minisatellite DNA variation was examined in 18 stocks of coho salmon Oncorhynchus kisutch from British Columbia and three stocks from Kamchatka or Western Alaska. Genomic DNA was restricted with Mbo I or Hae III and hybridized with two minisatellite probes (p Ssa -A34, Ots PBS-1). Allele frequencies and DNA band counts derived from the two probes were combined with band counts from the probe Ssa to show a regional stock structure. In British Columbia, stocks from the Fraser River were distinct from those on Vancouver Island, and all were differentiated from those on the mainland of British Columbia. Average heterozygosity at the Ssa -A34 locus was 71%. Compared with a previous study of British Columbia coho salmon population structure in which variation at 26 allozyme loci was examined, greater population differentiation and higher heterozygosity were observed at minisatellite loci. Estimated stock compositions of simulated mixtures of fishery samples from British Columbia stocks were accurate and precise, with the potential of identifying stocks within the drainage basin of a major river, the Fraser River. Minisatellite DNA variation may provide accurate and precise estimates of stock composition in actual fishery applications, and has the potential of identifying individual fish to region or stock of origin.     

Androgens and male mating behavior in rough-skinned newts, Taricha granulosa

Cyproterone acetate was administered either orally or intraperitoneally to intact, adult male newts, Taricha granulosa. The number of males that exhibited the courtship behavior of clasping when tested with nuptial females was not altered by the antiandrogen treatments. In males which were unresponsive to nuptial females, the occurrence of clasping was not evoked by injections for 4 days of testosterone, dihydrotestosterone, or 11-ketotestosterone. Further, the incidence of clasping was not significantly elevated by injections of prolactin and/or testosterone for 30 days. The effect of sexual activity on testosterone and dihydrotestosterone levels in male newts was determined by radioimmunoassay of plasma collected from males which were: (1) isolated from females; (2) allowed to clasp a female for 2 min; or (3) allowed to clasp a female for 1 hr. The testosterone and dihydrotestosterone levels were unchanged during this period of clasping. In February and again in June, plasma androgen concentrations were measured in males which differed in their propensity to initiate courtship when paired with females. Androgen levels were similar for males that clasped a female and males that never attempted to clasp a female. Plasma androgen levels in the male newt are apparently not correlated with sexual responsiveness.     

Biogenic silica and phosphorus accumulation in sediments as indices of eutrophication in the Laurentian Great Lakes

Biogenic silica (BSi), total phosphorus (TP), and biologically available phosphorus (AVP) were measured in short cores from Lake Michigan, Lake Erie, and Lake Ontario. Peaks in BSi concentration and peaks in BSi:TP or BSi:AVP ratios provided stratigraphic signals of water column silica (Si) depletion as a response of increased diatom production to P enrichment and decreased diatom production resulting from silica depletion. By contrast the stratigraphic record of P accumulation provided very weak signals of the historical nutrient enrichment in the water column. These results indicate that system P recycling has a higher rate constant than Si recycling and, as a consequence, that relatively small levels of P enrichment can increase diatom production and sedimentation eventually causing Si depletion and Si-limited diatom production in the water mass.     

A preliminary investigation of urinary testosterone and cortisol levels in wild male mountain gorillas

Urinary steroid hormone levels were measured in wild male mountain gorillas (Gorilla gorilla beringei) to determine how levels of testosterone and cortisol corresponded with age and social rank. Urine samples were collected noninvasively from 18 males, ranging in age from 3–26 years, in three groups of wild mountain gorillas at the Karisoke Research Center, Rwanda, Africa, and samples were analyzed using radioimmunoassay procedures. Males were classified as being immature (<7 years), maturing (10–13 years), or adult (+13 years of age). Immature males had significantly lower levels of testosterone and higher levels of cortisol than both maturing and adult males. No differences in testosterone or cortisol levels were found between maturing and adult males. Dominant males exhibited a trend toward significantly higher levels of testosterone than subordinate males, but no difference was found between cortisol levels of dominant and subordinate males. These results suggest that the increase in testosterone associated with puberty occurs prior to any outward sign of development of secondary sexual characteristics. Within-group male–male competition may affect testosterone levels, but the lack of difference in cortisol levels between dominant and subordinate males suggests that subordinate males are not socially stressed, at least as measured by cortisol. Am. J. Primatol. 43:51–64, 1997. © 1997 Wiley-Liss, Inc.     

The involvement of gonadotrophin and sex steroids in the control of reproduction in the parr and adults of Atlantic salmon, Salmo salar L.

Early sexual maturity occurred in the majority of male Atlantic salmon parr. Levels of the plasma androgens testosterone and 11-ketotestosterone rose steadily as the male parr matured, and decreased as the testes regressed. No such progressive changes were observed in the plasma gonadotrophin (GTH) levels, although the pituitary GTH levels were much higher in mature than in immature male parr; reasons for this, incluiding the possibility that the GTH radioimmunoassay employed is inadequate, are discussed. All female parr remained immature throughout the year, although the gonadosomatic index did show an annual cycle. Adult salmon had higher GTH and sex steroid levels than parr at the same stage of sexual maturity, the levels corresponding to the degree of sexual development of the adult fish.     

Physiological stress responses to confinement in diploid and triploid Atlantic salmon

Confinement of juvenile Atlantic salmon Salmo salar from four different populations (all–female diploids, all–female triploids, mixed sex diploids and mixed sex triploids) either before (FW parr) or after (SW smolts) transfer to sea elevated plasma cortisol and plasma lactate from control levels irrespective of ploidy status. Both before and after confinement, plasma cortisol levels in SW smolts (6–174 ng ml^–1) were higher than those in FW parr (4–58 ng ml^–1), which possibly reflected the physiological challenge of acclimation to SW. Mixed sex populations of SW smolts had higher cortisol levels than all–female populations. The duration of confinement (1, 3 or 6 h) affected the magnitude of the plasma cortisol and lactate responses in SW smolts. Plasma cortisol levels in diploid and triploid SW smolts subjected to 2 h of confinement decreased to pre–stress levels within 6 h post–confinement. Plasma lactate levels were not significantly different from pre–stress levels 48 h after confinement. As no difference exists in primary and secondary stress responses of Atlantic salmon of differing ploidy status, it is unlikely that differences in mortality rates between diploid and triploid populations under commercial conditions can be attributed to differences in their physiological responses to periods of stress lasting up to 6 h.     

Genetic analysis of growth and maturity in pink salmon (Oncorhynchus gorbuscha)

Variation in growth and sexual maturity was examined for five stocks of pink salmon (Oncorhynchus gorbuscha) spawning at different times in British Columbia. In each stock, four males were mated with eight females in a nested breeding design, and the juveniles were reared for 500 d after fry emergence. Adults in early-spawning northern stocks were smaller than those in late-spawning southern ones, but pink salmon from northern stocks had faster growth rates than those from southern ones. The relative ranking within stocks of family weight remained constant after late winter in the year of maturity. Heritability of weight based upon sire variance components was usually greater than 0.9 after 150 d of rearing. Pink salmon from the earlier-spawning stocks were in a more advanced state of sexual maturity when the experiment was terminated than were those from later-spawning stocks, indicative of a significant genetic component in timing of sexual maturity.     

Sex steroids in plasma of lake whitefish Coregonus clupeaformis during spawning in Lake Erie

Lake whitefish, Coregonus clupeaformis, were collected from the Western basin of Lake Erie during spawning. Free and conjugated (sulfated and glucuronidated) steroids including testosterone (T), 11-ketotestosterone (11-kT), estradiol-17beta (E2) and 17,20beta-dihydroxy-4-pregnen-3-one (17,20betaP) were measured in the plasma by radioimmunoassay. In males, the progression of spermiation was characterized by a significant decrease in plasma free steroids, whereas the levels of conjugated steroids remained similar and low, except for sulfated and glucuronidated testosterone. Plasma sex steroids did not correlate with the density or the motility of the spermatozoa. In females, the concentration of plasma T was significantly higher in preovulating than in ovulating females. The levels of E2 and 17,20betaP in ovulating lake whitefish exhibited large variations ranging from below detection limit to 0.9 ng ml(-1) and from 0.2 to 13 ng ml(-1), respectively. Analysis of conjugated steroids revealed high levels of glucuronidated and sulfated 17,20betaP and glucuronidated T in females ovulating in December. However, no significant differences in the proportion of the conjugated steroids were observed.     

Pelagic zonation of water quality and phytoplankton in the Great Lakes

Analysis of aquatic ecosystem data collected from large water bodies must consider spatial variations. A suite of pelagic survey stations exists for the Laurentian Great Lakes, but little is known about their redundancy. We present a strategy to delineate the lakes into zones based on water quality and phytoplankton biovolume. Water samples were collected from 72 sites in two seasons (spring and summer) from 2007 to 2010 in all five lakes. Integrated samples were analyzed for phytoplankton biovolume and nine water quality parameters. We conducted cluster analysis, principal components analysis and non-metric multidimensional scaling methods for water quality and phytoplankton taxon-specific biovolume for the Great Lakes basin and for each lake separately. There were significant lake-to-lake differences, and based on lake-specific analyses, Lake Superior, Lake Michigan and Lake Erie were each divided into three zones; Lake Huron and Lake Ontario were each grouped into two zones. The zones identified by water quality and phytoplankton provide an understanding of spatial distributions for evaluating monitoring data.     

Seasonal and social correlates of fecal testosterone and cortisol levels in wild male muriquis (Brachyteles arachnoides)

Fecal testosterone and cortisol levels were analyzed from six wild male muriquis (Brachyteles arachnoides) over a 19-month period at the Esta??o Biológica de Caratinga in Minas Gerais, Brazil, to investigate the hormonal correlates of seasonal sexual behavior and environmental conditions. Group mean testosterone levels based on weekly samples from the six males did not differ between copulatory and noncopulatory periods or between rainy and dry seasons. Cortisol levels did change with copulatory periods, and were significantly higher during the second dry season, when mating continued following an exceptionally heavy rainy season, than during the first dry season, when mating ceased. Males exhibited individual variation in the timing of their hormone shifts relative to their sexual activity, but neither hormone levels nor sexual activity were related to male age. Despite individual differences in the timing of testosterone fluctuations around the onset and offset of the copulatory season, all males exhibited elevated cortisol concentrations following a slight increase in testosterone at the beginning of the copulatory season. Both the lack of significant changes in testosterone levels with the onset of the rainy and copulatory season and the lack of prebreeding increases in cortisol may be related to the low levels of overt aggression displayed by male muriquis over access to mates.     

Distribution,prevalence and severity of Parvicapsula minibicornis infections among anadromous salmonids in the Fraser River,British Columbia,Canada

Polymerase chain reaction (PCR) and microscopic examination of stained kidney sections were used to diagnose infections with the myxozoan parasite Parvicapsula minibicornis in maturing Fraser River salmon. In 2 series of collections, the parasite was detected in 109 of 406 migrating sockeye salmon Oncorhynchus nerka belonging to Early Stuart, Early Summer and Summer run-timing groups, mainly upper Fraser River stocks. However, the parasite was detected neither in fish at sea nor once they had migrated several 100 km upstream. Prevalence then increased to 95% or greater at the spawning grounds. Histological examination of kidney was less sensitive than PCR in detecting the parasite in salmon collected from the earliest sites in both collections found positive by PCR. Severity of infection was greatest at the spawning grounds. Development of infection in sockeye, measured by prevalence, severity or by the rate of false-negative histological diagnoses, appeared to be a useful estimate of in-river residence time. Prevalence and severity of infections in sequential samples of Harrison River and Weaver Creek sockeye stocks collected from the Harrison River indicated that more time had elapsed since parasite transmission than would be predicted based on migration distance alone. Pink salmon Oncorhynchus gorbuscha, coho salmon O. kisutch and chinook salmon O. tshawytscha were found to be infected with the parasite. Development of P. minibicornis in pink salmon was most similar to that in sockeye. Pink and coho salmon may be at risk to the pathological consequences of P. minibicornis infection.     

Contrasting seasonal modulation of the stress response in male and female rainbow trout

Between June and September the magnitude of the plasma cortisol response of maturing male and female rainbow trout to confinement was indistinguishable. A progressive increase in confinement-induced cortisol levels in both sexes occurred during May to September, associated with the seasonal rise in water temperature. Between September and January a reduction of >50% in the magnitude of the cortisol response to confinement in male fish (but no decline in females) coincided with declining water temperature and significant increases in plasma 11-ketotestosterone and elevated plasma testosterone levels. Plasma oestradiol-17β levels were significantly greater in females than males throughout the study period and this difference was maximal between September and January. However, plasma testosterone was also elevated in females during this period and levels overall were higher than those in male fish. Previous studies have shown oestradiol-17β and testosterone to have diametrically opposed effects on stress responsiveness in trout, with the former enhancing, and the latter suppressing, the cortisol response to a stressor. The relative roles of androgens, estrogen and water temperature in modulating the stress responsiveness of rainbow trout are discussed.