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S T McMurry

Publications and source records attributed to S T McMurry.

At least 19 recordsLinked to original sources
PubMed2004

Relationship between DDE concentrations and laying sequence in eggs of two passerine species.

Passerine eggs make useful biomonitors of environmental pollutants. Among passerines, it is not known whether organochlorine contaminants in eggs within the same clutch are independent observations or follow a laying order effect. Intraclutch variation of DDE (1,1-dichloro-2,2-bis[(p-chlorophenyl)]ethylene) concentrations was studied in eggs collected from prothonotary warblers (Protonotaria citrea) and European starlings (Sturnus vulgaris) nesting on National Priority List sites in lower Alabama and central Colorado, respectively. All 209 eggs collected for this study contained detectable levels of DDE. Mean concentration of DDE across all prothonotary warbler eggs (mean 8.71 microg/g +/- 1.19, n = 20) was almost two orders of magnitude greater than mean concentrations of DDE in all starling eggs (mean 0.70 microg/g +/- 0.06, n = 189). In both species, there was a large amount of variability among individual eggs of the same clutch and no significant relationship between laying order and DDE concentration. Variation among eggs laid in the same sequential order was high and effectively masked any potential trends in laying order effect. We hypothesized that the variability was caused by the spatial heterogeneity of DDE on our study sites, the nature of egg development within a female passerine, or a combination of these factors. Investigators focusing on lipophilic contaminants should exercise caution when making inferences about contaminant concentrations in an entire clutch of passerine eggs after the collection and analysis of a single egg because our data show that DDE levels in a single egg collected for analysis do not consistently reflect DDE levels in the eggs remaining in the nest.

Animals↗
PubMed2002

Mercury in Morelet's crocodile eggs from northern Belize.

Recent studies have examined mercury accumulation in crocodilians. However, though most researchers have focused on tissue concentrations, few have examined mercury levels in crocodilian eggs. In July 1995, we analyzed mercury in 31 nonviable Morelet's crocodile ( Crocodylus moreletii) eggs collected from eight nests across three localities in northern Belize. All eggs were found to contain mercury. Based on an individual egg basis, mean concentration of mercury for all three localities was among the lowest reported for any crocodilian species. When localities were examined separately, mean concentrations for Laguna Seca and Gold Button Lagoon were comparable to those observed in other studies, and the mean for Sapote Lagoon was the lowest ever reported. Based on mean nest concentrations, mercury in eggs from Laguna Seca was approximately two- and tenfold higher than for Gold Button Lagoon and Sapote Lagoon, respectively. Variability in mercury concentrations among localities is likely the result of site-specific differences in mercury input, bioavailabilty, and bioaccumulation. Mercury concentrations were relatively uniform in eggs from the same nest and among nests from the same localities. The presence of mercury in Morelet's crocodile eggs suggests exposure in adult females, developing embryos, and neonates. However, crocodiles in these areas show no overt signs of mercury toxicity, and no indication of population decline is evident. A paucity of data on the effects of mercury on crocodilians precludes meaningful speculation as to the biological significance of tissue and egg concentrations. Controlled laboratory studies and long-term population monitoring are needed to address these questions.

Alligators and Crocodiles↗
PubMed2001

Ticks from a Morelet's crocodile in Belize.

Parasitism of crocodilians by ticks has rarely been reported, and to our knowledge only seven published accounts exist. On 3 July 1999, we collected four ticks from a subadult Morelet's crocodile (Crocodylus moreletii) captured in northern Belize. These were identified as Amblyomma dissimile (one female), and Amblyomma sp. (two nymphs, one larva). The crocodile was captured on land approximately 100 m from water, and all four ticks were attached to loose skin on the lateral surface of the tail. Crocodilians are most susceptible to terrestrial ectoparasites, including ticks, during overland movements. However, most such movements occur in response to drought, when tick questing activity is suppressed, which likely accounts for the small numbers of tick specimens recorded from crocodilians and the absence of any noticeable impact of parasitism on host fitness.

Alligators and Crocodiles↗
PubMed2001

Accumulation of DDT and mercury in prothonotary warblers (Protonotaria citrea) foraging in a heterogeneously contaminated environment.

Foraging areas of adult prothonotary warblers (Protonotaria citrea) were determined using standard radiotelemetry techniques to determine if soil concentrations of p,p'dichlorodiphenyltrichloroethane (p,p'DDT) and mercury in foraging areas could be used to predict contaminant levels in diets and tissues of nestling warblers. Adult warblers were fitted with transmitters and monitored for approximately 2 d while foraging and feeding 6- to 8-d-old nestlings. Foraging ecology data were integrated with contaminant levels of soil, diets, and tissues into a comprehensive analysis of geographic variation in contaminant exposure and uptake using linear regression. Concentrations of 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) and mercury in nestling tissues varied considerably across the study site. Mean concentration of DDE was greater in eggs than all other tissues, with individual samples ranging from 0.24 to 8.12 microgram/kg. In general, concentrations of DDT in soil were effective in describing the variation of contaminants in adipose samples. Concentrations of mercury in soils accounted for 78% of the variation in kidney samples. This was the best relationship of any of the paired variables. All other relationships showed relatively poor predictive ability.

Animals↗
PubMed2000

Organochlorine contaminants in Morelet's crocodile (Crocodylus moreletii) eggs from Belize.

Non-viable eggs of Morelet's crocodile (Crocodylus moreletii) were collected from Gold Button (GBL) and New River lagoons (NRL) in northern Belize and screened for organochlorine (OC) compounds using gas chromatography (GC) with electron capture detection (ECD). All egg samples from both lagoons (n = 24) tested positive for one or more OCs. Primary contaminants were p,p-DDE and methoxychlor, detected in 100% and 29% of the eggs examined, respectively. Concentrations of individual OC contaminants ranged from 1 ppb (ng chemical/g egg) to > 0.5 ppm (microgram chemical/g egg). Total concentrations of OCs (sum of all OCs) for one egg collected from a nest at GBL reached as high as 0.7 ppm. Sediment samples from both lagoons also tested positive for OCs (lindane, aldrin, methoxychlor, heptachlor epoxide, p,p-DDT, among others). Nest media (soil and plant material) collected from crocodile nests at GBL were positive for p,p-DDT, methoxychlor, aldrin, endosulfan II, and endrin aldehyde. Based on the 24 egg samples analyzed to date, crocodiles from both lagoons are being exposed to OCs. Such exposure may present a health threat to populations of crocodiles in Central America.

Aldrin↗
PubMed2000

DDE in eggs of two crocodile species from Belize.

Organochlorine (OC) residues were recently detected in nonviable Morelet's crocodile (Crocodylus moreletii) eggs from northern Belize. To further the assessment of contaminant exposure in Belizean crocodiles, nonviable Morelet's crocodile eggs (n = 11) from southern Belize and American crocodile (Crocodylus acutus) eggs (n = 12) from the coastal zones of Belize were screened for 20 OCs. Results indicated p,p-DDE to be the most prevalent OC (96% occurrence) in eggs examined, with concentrations ranging from 5 to 372 ng/g. These concentrations are similar to those observed in crocodile eggs (10-180 ng/g) from northern Belize. A general trend toward higher DDE concentrations in Morelet's crocodile eggs (mean = 103 ppb) compared with American crocodile eggs (mean = 31 ppb) was observed. However, this trend may be due to site-specific contamination rather than differences in interspecific susceptibility to chemical exposure. Other OCs detected in crocodile eggs included the parent compound, p,p-DDT, and its metabolite, p, p-DDD.

Alligators and Crocodiles↗
PubMed1999

Indicators of immunotoxicity in populations of cotton rats (Sigmodon hispidus) inhabiting an abandoned oil refinery.

Wildlife species inhabiting contaminated sites are often exposed to complex mixtures of chemicals, many of which have known effects on physiological and biochemical function. Although sensitivity of the immune system to chemical exposure has been documented in laboratory animal and wildlife species, little work has been conducted on feral wildlife populations inhabiting contaminated sites. Immune function was measured in populations of wild cotton rats (Sigmodon hispidus) inhabiting replicated reference and contaminated study sites at an abandoned oil refinery in Oklahoma four times from 1991 to 1992. Several measures of immunocompetence were examined including immune organ mass and cellularity, hematology, in vivo hypersensitivity, macrophage function, killer cell activity, and lymphoproliferative responsiveness. In vitro proliferation of splenocytes, either spontaneous or induced with concanavalin A (Con A), was the most consistent and reliable indicator of immunotoxicity. Spontaneous proliferation of splenocytes was 48 and 24% higher for cotton rats collected from contaminated than reference sites in September 1991 and September 1992, respectively. Likewise, Con A-induced proliferation of splenocytes ranged form 20 to 53% higher in animals collected from contaminated than reference sites in three of four collection periods. The percentage of splenocytes (mean+/-SE) staining positive for Con A receptors was lower on contaminated sites (73.7+/-1.2%) than reference sites (77.0+/-1.4%) in September 1991. Other measures of immune function including macrophage metabolism, hypersensitivity, blood cellularity, and mass and cellularity of immune organs varied between contaminated and reference sites.

Animals↗
PubMed1999

Ectromelia in Morelet's crocodile from Belize.

Two Morelet's crocodiles (Crocodylus moreletii) captured on 21 March 1997 and 20 April 1998 in the New River system, Belize exhibited ectromelia of one forelimb. External and radiograph examination appears to indicate limb agenesis of unknown etiology, as there is no apparent scarring or skeletal trauma. These two individuals represent the only cases of missing limbs from 642 individuals captured in this study and to our knowledge, the first reported cases in Morelet's crocodile. Several factors including age and diet of the reproducing female, extremes in nest conditions (egg incubation temperature and humidity), and exposure to environmental contaminants can cause developmental abnormalities in crocodilians and may have contributed to the condition observed in these animals. Survival rates for hatchling crocodilians are generally low, and embryonic malformations such as ectromelia may constitute an added disadvantage to survival. However, both individuals examined in this study were vigorous and appeared in good condition.

Alligators and Crocodiles↗
PubMed1996

Environmental, age, and sex effects on cotton rat (Sigmodon hispidus) hematology.

We determined the effects of sex, age, and environment (inbred, captive-wild, and wild animals) on selected blood parameters of the cotton rat (Sigmodon hispidus) in central Oklahoma (USA) from 1990 to 1994. Male and female cotton rats had similar blood profiles. Age-related differences were confined to differential white blood cell counts where adults possessed greater numbers of neutrophils and lower numbers of lymphocytes compared to juveniles. Environment had a strong influence on many hematological parameters. Hematocrit, hemoglobin concentration, RBC count, and eosinophil number were generally greater for wild stocks compared to inbred animals, and differences were more pronounced for adults than juveniles.

Aging↗
PubMed1995

Sensitivity of selected immunological, hematological, and reproductive parameters in the cotton rat (Sigmodon hispidus) to subchronic lead exposure.

The effect of lead exposure on cellular immunity, hematology, and reproductive and body condition in mature cotton rats (Sigmodon hispidus) was examined. Two groups of 36 cotton rats each were exposed to 0, 100, or 1,000 ppm lead in drinking water for either 7 or 13 weeks, between 31 August and 2 December 1990. Specific and non-specific cell-mediated immunity was assessed by measuring splenocyte proliferative responses to polyclonal mitogens (Concanavalin A and Pokeweed mitogen), in vivo 24-hr delayed-type hypersensitivity, metabolic activity of peritoneal macrophages, spleen mass and cellularity, and immune organ development. General physiological condition was assessed from hematological, morphological, and reproductive measures. Immune function was sensitive to lead exposure based on depressed proliferative responses of cultured splenocytes, smaller popliteal lymph nodes, and larger spleens among cotton rats receiving 1,000 ppm lead. Spleen mass was reduced in cotton rats receiving 100 ppm lead. Total leukocytes, lymphocytes, neutrophils, eosinophils, total splenocyte yield, packed cell volume, hemoglobin, and mean corpuscular hemoglobin were sensitive to lead exposure. Effects of lead exposure on general condition and reproductive parameters included reduced mass of liver, seminal vesicles, and epididymes in males following a 7-week exposure. Histopathologic changes reflected lead toxicity and included altered renal proximal tubular epithelium, renal intranuclear inclusions, and in some cases, lowered numbers of sperm and developing follicles. In general, lesions were more pronounced with increased lead concentration and longer exposure.

Adrenal Glands↗
PubMed1994

Cellular immune responses of nutritionally stressed juvenile cotton rats (Sigmodon hispidus) during acute benzene exposure.

Wild juvenile cotton rats (Sigmodon hispidus) were used in this study to examine the effects of exposure to cyclophosphamide (CY) or differing levels of benzene on selected measures of cellular immunity following dietary protein restriction. Benzene caused marginal immunotoxicity as indicated by suppressed splenocyte proliferation and total circulating neutrophils. Cyclophosphamide and also crude protein restriction induced severe immune lesions manifested as thymus and spleen atrophy, depressed delayed hypersensitivity response, reduced proliferative capacity of splenocytes, and reduced numbers of total leukocytes, lymphocytes, and splenocytes. Although severe immune modulation resulted from the individual effects of CY exposure and dietary protein restriction, there was little statistically significant toxicant-diet interaction.

Animals↗
PubMed1993

Selected immune responses of adult cotton rats (Sigmodon hispidus) to dietary restriction.

1. We examined the influence of moderate to severe dietary restriction on immune system function in adult cotton rats. Animals (N = 80) were fed ad lib. (controls) or restricted [moderate = 80% ad lib. for 1 or 2 weeks; severe = 80% ad lib. for 1 or 2 weeks followed by 40% ad lib. for one (week 3) or two (week 4) additional weeks] amounts of food for 1-4 weeks. 2. Average body weight loss for severely restricted animals in week 4 was 17%; dietary treatments had no measurable effect on hematological parameters (hematocrit, white blood cell count), lymphoid organ weights (thymus gland, spleen, popliteal lymph nodes), and mononuclear cell yields from lymphoid organs. 3. Cell-mediated immune function was assessed in vitro by a lymphoproliferative response assay and in vivo by a delayed-type hypersensitivity response assay. 4. Proliferative responses of spleen cell cultures stimulated with concanavalin A (Con A, Canavalia ensiformis) and pokeweed (PWM, Phytolacca americana) were normal or significantly greater among moderately restricted than control cotton rats during week 1 and week 2. 5. Lymphoproliferative responses of severely restricted animals were normal or reduced during week 3 and week 4. 6. Delayed-type hypersensitivity responses to the contact antigen oxazolone were significantly depressed among severely restricted animals in week 4 compared to controls. 7. In comparison with laboratory rodent strains, our initial results indicate that immune system function in adult cotton rats is not as sensitive to short term (1-4 weeks) periods of dietary restriction. 8. Immune system function was related to changes in body weight as a result of feed restriction.

Animals↗
PubMed1991

Primary immune responses of selected small mammal species to heterologous erythrocytes.

1. We surveyed the primary humoral immune responsiveness of six small mammal species (Peromyscus leucopus, Microtus pinetorum, Perognathus hispidus, Neotoma floridana, Onychomys leucogaster, Mus musculus) collected from wild populations in central Oklahoma using sheep red blood cells (SRBC) as the immunogen and a splenic plaque-forming cell (PFC) assay. 2. Individuals within each wild species examined produced antibodies to a single intraperitoneal injection of SRBC, however, considerable interspecific and intraspecific variation in responsiveness was indicated. 3. Overall, primary immune responsiveness varied from 0 to 5013 PFC/10(6) cells. Spleen weights, total splenic nucleated cell yields, PFC/spleen, PFC/mg spleen, and PFC/10(6) cells were significantly different among species. 4. Mean cell yield in M. pinetorum was greater than in P. leucopus and CD-1 laboratory mice (included as positive controls). Number of PFC/10(6) cells was greater in CD-1 laboratory mice than P. hispidus and P. leucopus. The coefficient of variation for PFC/10(6) cells in CD-1 laboratory mice was 38% compared to 109, 129, and 56% for M. pinetorum, P. hispidus, and P. leucopus, respectively. 5. Interspecific and intraspecific differences among wild species may be a reflection of disparate life histories and other environmental selection pressures.

Animals↗
PubMed1991

Influence of habitat modification on the community of gastrointestinal helminths of cotton rats.

Dynamics of communities of gastrointestinal helminths of cotton rats (Sigmodon hispidus) were monitored in response to five experimental brush management treatments using herbicide applications with and without prescribed burning on the Cross Timbers Experimental Range in Payne County, Oklahoma (USA). A total of 113 adult cotton rats (68 male and 45 female) was collected from experimental pastures in winter and summer 1986 resulting in the recovery of five species of helminths: Longistriata adunca, Syphacia sigmodontis, Strongyloides sp., Protospirura muris, and Raillietina sp. Prevalences of Raillietina sp. and S. sigmodontis were greater on control than herbicide-treated pastures. Prevalence and abundance of Raillietina sp. and prevalence of S. sigmodontis were significantly lower on annually burned, herbicide-treated pastures compared to unburned herbicide-treated pastures. Triclopyr-treated pastures had greater abundances of L. adunca and lower abundances of Raillietina sp. than those treated with tebuthiuron. Abundances of L. adunca also decreased from winter to summer on annually burned, herbicide-treated pastures while increasing on other pastures. Distribution of all helminths was overdispersed, but distribution of L. adunca showed a significant brush treatment by season interaction as a result of greater overdispersion in summer than winter for cotton rats inhabiting brush-treated pastures. Our results indicate that man-induced habitat modifications can alter host-parasite relationships in the community.

Animals↗
PubMed1990

Influence of habitat modification on the intestinal helminth community ecology of cottontail rabbit populations.

The influence of five brush management treatments using the herbicides tebuthiuron and triclopyr, with or without prescribed burning, on the intestinal helminth community of cottontail rabbits (Sylvilagus floridanus) was studied in 1987 on the Cross Timbers Experimental Range in Payne County, Oklahoma (USA). Six helminth species were found (Dermatoxys veligera, Trichostrongylus calcaratus, Passalurus nonanulatus, Wellcomia longejector, Taenia pisiformis cystercercus, and Mosgovoyia pectinata americana) in 102 rabbits (88 adult and 14 juveniles) collected over two seasons (winter and summer). Prevalence of M. pectinata americana in cottontail rabbits was significantly greater in untreated control pastures than herbicide treated pastures in winter, while prevalence of T. pisiformis was significantly greater in burned than unburned pastures. Abundances of helminth species in the intestinal tract of cottontail rabbits were unaffected by brush treatments. Mosgovoyia pectinata americana abundance demonstrated a highly significant increase from winter to summer; conversely, abundance of all oxyurid pinworms combined (D. veligera, P. nonanulatus, W. longejector) was significantly higher in winter than summer. Helminth community dynamics were significantly influenced by season, but were unaffected by brush treatments. Habitat modification could have influenced cestode transmission by altering the ecology of invertebrate and vertebrate hosts.

Animals↗