Geology topics

J.J. Wiebe

Publications and source records attributed to J.J. Wiebe.

3 recordsLinked to original sources

USGS2004

Umbilical scarring in hatchling American alligators

Umbilical scarring is the presence of excess scar tissue deposited between abdominal dermal layers at the site of yolk sac absorption in hatchling American alligators (Alligator mississippiensis). The presence of this dermal condition plays a key evaluatory role in the overall quality and subsequent value for various commercial leather products. Despite the prevalent nature of this condition, currently the industry has no standardized protocols for its quantification. The objectives of this study were to examine the relationship between hatchling weight and age and incidence of umbilical scarring and to develop a quantifiable and reproducible technique to measure this dermal condition in hatchling American alligators. Thirty eggs from each of nine clutches were incubated in two separate incubators at different facilities and hatchling umbilical scarring was measured at 2 and 10 days of age using digital calipers. Umbilical area was calculated by multiplying umbilical length times umbilical width. There was a significant effect of both age and clutch on umbilical area (overall decline of 64%) by 10 days post-hatch. However, only five of the nine clutches utilized expressed a noticeable decline in the size of this dermal condition (range 67-74%). We had hypothesized that larger hatchlings would have larger umbilical areas and a slower rate of improvement in this condition during the first few days post-hatch. The differences in umbilical area and percent decline with age across clutches, however, were not associated with differences in initial hatchling weights. Within clutches and time periods, hatchling weight had no significant effect on the size and/or rate of decline of this condition. ?? 2004 Published by Elsevier B.V.

Aquaculture↗

USGS2004

Organochlorine pesticides and thiamine in eggs of largemouth bass and American alligators and their relationship with early life-stage mortality

Thiamine deficiency has been linked to early mortality syndrome in salmonids in the Great Lakes. This study was conducted to compare thiamine concentrations in American alligators ( Alligator mississippiensis ) and Florida largemouth bass ( Micropterus salmoides floridanus ) eggs from sites with high embryo mortality and high exposure to organochlorine pesticides (OCPs) (Lakes Apopka and Griffin, and Emeralda Marsh, Florida, USA) to those from sites that have historically exhibited low embryo mortality and low OCPs (Lakes Woodruff and Orange, Florida). During June-July 2000, 20 alligator clutches were collected from these sites, artificially incubated, and monitored for embryo mortality. Thiamine and OCPs were measured in one egg/clutch. During February 2002, 10 adult female bass were collected from Emeralda Marsh and Lake Woodruff and mature ovaries analyzed for thiamine and OCP concentrations. Although ovaries from the Emeralda Marsh bass contained almost 1,000-fold more OCPs compared with the reference site, Lake Woodruff, there were no differences in thiamine concentrations between sites (11,710 vs. 11,857 pmol/g). In contrast, alligator eggs from the reference site had five times the amount of thiamine compared with the contaminated sites (3,123 vs. 617 pmol/g). Similarly, clutches with > 55% hatch rates had significantly higher concentrations of thiamine compared with clutches with <54% hatch rates (1,119 vs. 201 pmol/g). These results suggest that thiamine deficiency might be playing an important role in alligator embryo survival but not in reproductive failure and recruitment of largemouth bass. The cause(s) of this thiamine deficiency are unknown but might be related to differences in the nutritional value of prey items across the sites studied and/or to the presence of high concentration of contaminants in eggs.

Florida↗

USGS2002

Characterization of annual reproductive cycles for pond-reared Florida largemouth bass Micropterus salmoides floridanus

The annual reproductive cycle of hatchery-raised largemouth bass (Florida subspecies Micropterus salmoides floridanus) was characterized over a one-year period. Largemouth bass have a distinct annual reproductive cycle with a spring spawning season (approximately between mid-January and mid-June). Cycle characterization focused on an evaluation of gonadal development and plasma concentrations of several sex steroids and vitellogenin (VTG). Adult largemouth bass (n = 20: 10 females and 10 males) were collected monthly from hatchery ponds for one full calendar year. Plasma samples were analyzed for estradiol-17?? (E2), 11-ketotestosterone (11-KT), testosterone (T), progesterone (P), and VTG. Gonadal tissues were weighed to calculate gonadosomatic index (GSI) and evaluated histologically to characterize reproductive stage. In both sexes, GSI began to increase in November, and peaked in February-March. Increases in gonad weights were correlated with maturation of gonads as evidenced by histological evaluations. Bass exhibited seasonal changes in plasma sex steroids and VTG. In males, 11-KT was the only sex steroid that showed strong seasonality, with highest values in February. In females, although E2 and T concentrations followed a similar annual cycle, with highest and lowest values in February and August, respectively, the strongest pattern was observed with E2. 11-KT concentrations were less variable across months, and values were about half of those observed in males. In females, P peaked two months after E2, with high values still in May and June and decreased thereafter, and VTG began to increase in October, but peaked a month prior to the observed peaked in E2. VTG was also detected in males but at concentrations that were about 1/12 that of females, and no seasonal pattern was evident. This study is the first to fully characterize the seasonal endocrine cycle for largemouth bass. These data will be useful when conducting reproductive evaluations of free-ranging populations of largemouth bass and for assessing potential reproductive effects due to environmental contaminants in this species. ?? 2002 by the American Fisheries Society.

American Fisheries Society Symposium↗