Graham Worthy | University of Central Florida (original) (raw)
Papers by Graham Worthy
Journal of Archaeological Science, 2016
Several techniques have been used to sample annual dentin layers in mammalian teeth for stable is... more Several techniques have been used to sample annual dentin layers in mammalian teeth for stable isotope analysis. However tooth size in smaller animals and the conical arrangement of the dentin layers have constrained precision of subsampling and collection of adequate sample from each annual growth layer. We tested an alternative subsampling technique using teeth from Risso's dolphins (n ¼ 15) that involved cutting out the annual dentin growth layer groups (GLGs) from 300 to 500 mm longitudinal sections from one half of a demineralized tooth and comparing the results to those obtained using a standard micromilling process on the other half of the same tooth. Subsamples were analyzed for elemental C and N content and for stable C and N isotopes. Subsamples obtained from cutting out the GLGs showed more consistent wt%N, wt%C, and atomic C/N ratios that were significantly different (P<0.0001) from those obtained by micromilling. Consequently, the d15N and d13C values differed significantly between methods with values from the former method being more concordant with the expected variations in the early years of Risso's dolphins. Deviations in d13C values in the micromilled subsamples were large enough to create possible errors in interpretation of dietary sources. Cutting out the dentin layers reduced sample processing time by 90% and yielded ~10% more collagen than micromilling. These results suggest that cutting out the annual dentin layers can produce greater yield of samples of better collagen quality with a much shorter processing time than the micromilling process and is, therefore, an effective method to subsample small mammalian teeth.
Several techniques have been used to sample annual dentin layers in mammalian teeth for stable is... more Several techniques have been used to sample annual dentin layers in mammalian teeth for stable isotope
analysis. However tooth size in smaller animals and the conical arrangement of the dentin layers have
constrained precision of subsampling and collection of adequate sample from each annual growth layer.
We tested an alternative subsampling technique using teeth from Risso's dolphins (n ¼ 15) that involved
cutting out the annual dentin growth layer groups (GLGs) from 300 to 500 mm longitudinal sections from
one half of a demineralized tooth and comparing the results to those obtained using a standard
micromilling process on the other half of the same tooth. Subsamples were analyzed for elemental C and
N content and for stable C and N isotopes. Subsamples obtained from cutting out the GLGs showed more
consistent wt%N, wt%C, and atomic C/N ratios that were significantly different (P<0.0001) from those
obtained by micromilling. Consequently, the d15N and d13C values differed significantly between methods
with values from the former method being more concordant with the expected variations in the early
years of Risso's dolphins. Deviations in d13C values in the micromilled subsamples were large enough to
create possible errors in interpretation of dietary sources. Cutting out the dentin layers reduced sample
processing time by 90% and yielded ~10% more collagen than micromilling. These results suggest that
cutting out the annual dentin layers can produce greater yield of samples of better collagen quality with a
much shorter processing time than the micromilling process and is, therefore, an effective method to
subsample small mammalian teeth.
Gulf and Caribbean Research, 2005
Reports of West Indian manatees (Trichechus manatus) in the US Gulf of Mexico west of Florida hav... more Reports of West Indian manatees (Trichechus manatus) in the US Gulf of Mexico west of Florida have increased during the last decade. We reviewed all available manatee sighting, capture, and carcass records (n = 377) from Alabama, Louisiana, Mississippi, and Texas since the early 1900s; only 40 of these were previously published. Manatees were reported most often in estuarine habitats, usually either near a freshwater source or natural or industrial warm-water springs/runoffs during winter months. The recent increase in manatee records may be due to a combination of increased public awareness and dispersal of manatees, most likely seasonal migrants from Florida. We caution that the presence of artificial warm-water sources outside of the manatee's traditional range may attract an increasing number of manatees and could increase the incidence of cold-related mortality in this region.
Journal of Experimental Biology
volumes of water, which may make them susceptible to hyponatremia if access to a source of Na + i... more volumes of water, which may make them susceptible to hyponatremia if access to a source of Na + is not provided.
Journal of Experimental Biology
Because thyroid hormones play a critical role in the regulation of metabolism, the low metabolic ... more Because thyroid hormones play a critical role in the regulation of metabolism, the low metabolic rates reported for manatees suggest that thyroid hormone concentrations in these animals may also be reduced. However, thyroid hormone concentrations have yet to be examined in manatees. The effects of captivity, diet and water salinity on plasma total triiodothyronine (tT(3)), total thyroxine (tT(4)) and free thyroxine (fT(4)) concentrations were assessed in adult West Indian manatees (Trichechus manatus). Free-ranging manatees exhibited significantly greater tT(4) and fT(4) concentrations than captive adults, regardless of diet, indicating that some aspect of a captive existence results in reduced T(4) concentrations. To determine whether this reduction might be related to feeding, captive adults fed on a mixed vegetable diet were switched to a strictly sea grass diet, resulting in decreased food consumption and a decrease in body mass. However, tT(4) and fT(4) concentrations were sign...
In "Digestive Efficiencies of Ex Situ and In Situ West Indian Manatees (Trichechus manatus latiro... more In "Digestive Efficiencies of Ex Situ and In Situ West Indian Manatees (Trichechus manatus latirostris)" , in six instances, values noted in the Discussion are incorrect and do not match the corresponding values in table 6. The corrected values are indicated in bold below. is correct, and the conclusions of the article are unchanged. The authors regret the error.
Health, Disease, and Rehabilitation, Second Edition, 2001
The Journal of experimental biology, 1999
The ability of West Indian manatees (Trichechus manatus) to move between fresh and salt water rai... more The ability of West Indian manatees (Trichechus manatus) to move between fresh and salt water raises the question of whether manatees drink salt water. Water turnover rates were estimated in captive West Indian manatees using the deuterium oxide dilution technique. Rates were quantified in animals using four experimental treatments: (1) held in fresh water and fed lettuce (N=4), (2) held in salt water and fed lettuce (N=2), (3) acutely exposed to salt water and fed lettuce (N=4), and (4) chronically exposed to salt water with limited access to fresh water and fed sea grass (N=5). Animals held in fresh water had the highest turnover rates (145+/-12 ml kg-1 day-1) (mean +/- s.e.m.). Animals acutely exposed to salt water decreased their turnover rate significantly when moved into salt water (from 124+/-15 to 65+/-15 ml kg-1 day-1) and subsequently increased their turnover rate upon re-entry to fresh water (146+/-19 ml kg-1 day-1). Manatees chronically exposed to salt water had signific...
Aquatic Mammals, 2006
A non-invasive photographic technique was developed to estimate the body mass of Hawaiian monk se... more A non-invasive photographic technique was developed to estimate the body mass of Hawaiian monk seals (Monachus schauinslandi). Newly weaned monk seal pups (n = 31) were photographed and measured at Kure Atoll in the northwestern Hawaiian Islands. Length, side area, anterior/posterior area, and perimeter were measured from photographs to establish predictive relationships with body mass using regression analyses. Photographs were subjectively ranked in terms of quality, based on the degree to which the seal's body position deviated from the ideal position used to obtain standardized photographs. Results indicated that deviations in body positioning (e.g., a seal rolled on its side) did not significantly alter photogrammetric (surface area or perimeter) values compared to those obtained in a standardized position.
Comparative biochemistry and physiology. A, Comparative physiology, 1991
1. Harp and grey seal pups were examined during the post-weaning period to quantify their thermor... more 1. Harp and grey seal pups were examined during the post-weaning period to quantify their thermoregulatory abilities and thermal limits. 2. Deep body temperatures of harp seals (37.8 +/- 0.8 degrees C) were not significantly different from those of grey seals (38.9 +/- 0.4 degrees C). 3. As blubber depth declined during the fast, temperature gradients extended increasingly deeper into the muscle layer potentially decreasing heat loss. 4. Blubber conductivity (approximately 0.18 W/m/degrees C) did not vary regionally within an animal, or between animals or species. 5. Calculated lethal cold limits in air were between -85.4 degrees C and -116.1 degrees C, suggesting that fasting, weaned pups can easily cope with temperatures they would normally experience.
New Perspectives: Toxicology and the Environment, 2002
Diseases of aquatic organisms, Jan 2, 2014
An unusual mortality event (UME) was declared for cetaceans in the northern Gulf of Mexico (GoM) ... more An unusual mortality event (UME) was declared for cetaceans in the northern Gulf of Mexico (GoM) for Franklin County, Florida, west through Louisiana, USA, beginning in February 2010 and was ongoing as of September 2014. The 'Deepwater Horizon' (DWH) oil spill began on 20 April 2010 in the GoM, raising questions regarding the potential role of the oil spill in the UME. The present study reviews cetacean mortality events that occurred in the GoM prior to 2010 (n = 11), including causes, durations, and some specific test results, to provide a historical context for the current event. The average duration of GoM cetacean UMEs prior to 2010 was 6 mo, and the longest was 17 mo (2005-2006). The highest number of cetacean mortalities recorded during a previous GoM event was 344 (in 1990). In most previous events, dolphin morbillivirus or brevetoxicosis was confirmed or suspected as a causal factor. In contrast, the current northern GoM UME has lasted more than 48 mo and has had mor...
Journal of Experimental Biology, 2014
Diet-tissue discrimination factors (Δ 15 N or Δ 13 C) and turnover times are thought to be influe... more Diet-tissue discrimination factors (Δ 15 N or Δ 13 C) and turnover times are thought to be influenced by a wide range of variables including metabolic rate, age, dietary quality, tissue sampled and the taxon being investigated. In the present study, skin samples were collected from ex situ dolphins that had consumed diets of known isotopic composition for a minimum of 8 weeks. Adult dolphins consuming a diet of low fat (5-6%) and high δ 15 N value had significantly lower Δ 15 N values than animals consuming a diet with high fat (13.9%) and low δ 15 N value. Juvenile dolphins consuming a diet with low fat and an intermediate δ 15 N value had significantly higher Δ 15 N values than adults consuming the same diet. Calculated half-lives for δ 15 N ranged from 14 to 23 days (17.2±1.3 days). Half-lives for δ 13 C ranged from 11 to 23 days with a significant difference between low fat (13.9±4.8 days) and high fat diets (22.0±0.5 days). Overall, our results indicate that while assuming a Δ 13 C value of 1‰ may be appropriate for cetaceans, Δ 15 N values may be closer to 1.5‰ rather than the commonly assumed 3‰. Our data also suggest that understanding seasonal variability in prey composition is another significant consideration when applying discrimination factors or turnover times to field studies focused on feeding habits. Isotope retention times of only a few weeks suggest that, in addition, these isotope data could play an important role in interpreting recent fine-scale habitat utilization and residency patterns.
Journal of Experimental Biology, 2009
The Florida manatee (Trichechus manatus latirostris) is a herbivorous marine mammal that occupies... more The Florida manatee (Trichechus manatus latirostris) is a herbivorous marine mammal that occupies freshwater, estuarine and marine habitats. Despite being considered endangered, relatively little is known about its feeding ecology. The present study expands on previous work on manatee feeding ecology by providing critical baseline parameters for accurate isotopic data interpretation. Stable carbon and nitrogen isotope ratios were examined over a period of more than 1 year in the epidermis of rescued Florida manatees that were transitioning from a diet of aquatic forage to terrestrial forage (lettuce). The mean half-life for 13 C turnover was 53 and 59 days for skin from manatees rescued from coastal and riverine regions, respectively. The mean halflife for 15 N turnover was 27 and 58 days, respectively. Because of these slow turnover rates, carbon and nitrogen stable isotope analysis in manatee epidermis is useful in summarizing average dietary intake over a long period of time rather than assessing recent diet. In addition to turnover rate, a diet-tissue discrimination value of 2.8‰ for 13 C was calculated for long-term captive manatees on a lettuce diet. Determining both turnover rate and diet-tissue discrimination is essential in order to accurately interpret stable isotope data.
Journal of Archaeological Science, 2016
Several techniques have been used to sample annual dentin layers in mammalian teeth for stable is... more Several techniques have been used to sample annual dentin layers in mammalian teeth for stable isotope analysis. However tooth size in smaller animals and the conical arrangement of the dentin layers have constrained precision of subsampling and collection of adequate sample from each annual growth layer. We tested an alternative subsampling technique using teeth from Risso's dolphins (n ¼ 15) that involved cutting out the annual dentin growth layer groups (GLGs) from 300 to 500 mm longitudinal sections from one half of a demineralized tooth and comparing the results to those obtained using a standard micromilling process on the other half of the same tooth. Subsamples were analyzed for elemental C and N content and for stable C and N isotopes. Subsamples obtained from cutting out the GLGs showed more consistent wt%N, wt%C, and atomic C/N ratios that were significantly different (P<0.0001) from those obtained by micromilling. Consequently, the d15N and d13C values differed significantly between methods with values from the former method being more concordant with the expected variations in the early years of Risso's dolphins. Deviations in d13C values in the micromilled subsamples were large enough to create possible errors in interpretation of dietary sources. Cutting out the dentin layers reduced sample processing time by 90% and yielded ~10% more collagen than micromilling. These results suggest that cutting out the annual dentin layers can produce greater yield of samples of better collagen quality with a much shorter processing time than the micromilling process and is, therefore, an effective method to subsample small mammalian teeth.
Several techniques have been used to sample annual dentin layers in mammalian teeth for stable is... more Several techniques have been used to sample annual dentin layers in mammalian teeth for stable isotope
analysis. However tooth size in smaller animals and the conical arrangement of the dentin layers have
constrained precision of subsampling and collection of adequate sample from each annual growth layer.
We tested an alternative subsampling technique using teeth from Risso's dolphins (n ¼ 15) that involved
cutting out the annual dentin growth layer groups (GLGs) from 300 to 500 mm longitudinal sections from
one half of a demineralized tooth and comparing the results to those obtained using a standard
micromilling process on the other half of the same tooth. Subsamples were analyzed for elemental C and
N content and for stable C and N isotopes. Subsamples obtained from cutting out the GLGs showed more
consistent wt%N, wt%C, and atomic C/N ratios that were significantly different (P<0.0001) from those
obtained by micromilling. Consequently, the d15N and d13C values differed significantly between methods
with values from the former method being more concordant with the expected variations in the early
years of Risso's dolphins. Deviations in d13C values in the micromilled subsamples were large enough to
create possible errors in interpretation of dietary sources. Cutting out the dentin layers reduced sample
processing time by 90% and yielded ~10% more collagen than micromilling. These results suggest that
cutting out the annual dentin layers can produce greater yield of samples of better collagen quality with a
much shorter processing time than the micromilling process and is, therefore, an effective method to
subsample small mammalian teeth.
Gulf and Caribbean Research, 2005
Reports of West Indian manatees (Trichechus manatus) in the US Gulf of Mexico west of Florida hav... more Reports of West Indian manatees (Trichechus manatus) in the US Gulf of Mexico west of Florida have increased during the last decade. We reviewed all available manatee sighting, capture, and carcass records (n = 377) from Alabama, Louisiana, Mississippi, and Texas since the early 1900s; only 40 of these were previously published. Manatees were reported most often in estuarine habitats, usually either near a freshwater source or natural or industrial warm-water springs/runoffs during winter months. The recent increase in manatee records may be due to a combination of increased public awareness and dispersal of manatees, most likely seasonal migrants from Florida. We caution that the presence of artificial warm-water sources outside of the manatee's traditional range may attract an increasing number of manatees and could increase the incidence of cold-related mortality in this region.
Journal of Experimental Biology
volumes of water, which may make them susceptible to hyponatremia if access to a source of Na + i... more volumes of water, which may make them susceptible to hyponatremia if access to a source of Na + is not provided.
Journal of Experimental Biology
Because thyroid hormones play a critical role in the regulation of metabolism, the low metabolic ... more Because thyroid hormones play a critical role in the regulation of metabolism, the low metabolic rates reported for manatees suggest that thyroid hormone concentrations in these animals may also be reduced. However, thyroid hormone concentrations have yet to be examined in manatees. The effects of captivity, diet and water salinity on plasma total triiodothyronine (tT(3)), total thyroxine (tT(4)) and free thyroxine (fT(4)) concentrations were assessed in adult West Indian manatees (Trichechus manatus). Free-ranging manatees exhibited significantly greater tT(4) and fT(4) concentrations than captive adults, regardless of diet, indicating that some aspect of a captive existence results in reduced T(4) concentrations. To determine whether this reduction might be related to feeding, captive adults fed on a mixed vegetable diet were switched to a strictly sea grass diet, resulting in decreased food consumption and a decrease in body mass. However, tT(4) and fT(4) concentrations were sign...
In "Digestive Efficiencies of Ex Situ and In Situ West Indian Manatees (Trichechus manatus latiro... more In "Digestive Efficiencies of Ex Situ and In Situ West Indian Manatees (Trichechus manatus latirostris)" , in six instances, values noted in the Discussion are incorrect and do not match the corresponding values in table 6. The corrected values are indicated in bold below. is correct, and the conclusions of the article are unchanged. The authors regret the error.
Health, Disease, and Rehabilitation, Second Edition, 2001
The Journal of experimental biology, 1999
The ability of West Indian manatees (Trichechus manatus) to move between fresh and salt water rai... more The ability of West Indian manatees (Trichechus manatus) to move between fresh and salt water raises the question of whether manatees drink salt water. Water turnover rates were estimated in captive West Indian manatees using the deuterium oxide dilution technique. Rates were quantified in animals using four experimental treatments: (1) held in fresh water and fed lettuce (N=4), (2) held in salt water and fed lettuce (N=2), (3) acutely exposed to salt water and fed lettuce (N=4), and (4) chronically exposed to salt water with limited access to fresh water and fed sea grass (N=5). Animals held in fresh water had the highest turnover rates (145+/-12 ml kg-1 day-1) (mean +/- s.e.m.). Animals acutely exposed to salt water decreased their turnover rate significantly when moved into salt water (from 124+/-15 to 65+/-15 ml kg-1 day-1) and subsequently increased their turnover rate upon re-entry to fresh water (146+/-19 ml kg-1 day-1). Manatees chronically exposed to salt water had signific...
Aquatic Mammals, 2006
A non-invasive photographic technique was developed to estimate the body mass of Hawaiian monk se... more A non-invasive photographic technique was developed to estimate the body mass of Hawaiian monk seals (Monachus schauinslandi). Newly weaned monk seal pups (n = 31) were photographed and measured at Kure Atoll in the northwestern Hawaiian Islands. Length, side area, anterior/posterior area, and perimeter were measured from photographs to establish predictive relationships with body mass using regression analyses. Photographs were subjectively ranked in terms of quality, based on the degree to which the seal's body position deviated from the ideal position used to obtain standardized photographs. Results indicated that deviations in body positioning (e.g., a seal rolled on its side) did not significantly alter photogrammetric (surface area or perimeter) values compared to those obtained in a standardized position.
Comparative biochemistry and physiology. A, Comparative physiology, 1991
1. Harp and grey seal pups were examined during the post-weaning period to quantify their thermor... more 1. Harp and grey seal pups were examined during the post-weaning period to quantify their thermoregulatory abilities and thermal limits. 2. Deep body temperatures of harp seals (37.8 +/- 0.8 degrees C) were not significantly different from those of grey seals (38.9 +/- 0.4 degrees C). 3. As blubber depth declined during the fast, temperature gradients extended increasingly deeper into the muscle layer potentially decreasing heat loss. 4. Blubber conductivity (approximately 0.18 W/m/degrees C) did not vary regionally within an animal, or between animals or species. 5. Calculated lethal cold limits in air were between -85.4 degrees C and -116.1 degrees C, suggesting that fasting, weaned pups can easily cope with temperatures they would normally experience.
New Perspectives: Toxicology and the Environment, 2002
Diseases of aquatic organisms, Jan 2, 2014
An unusual mortality event (UME) was declared for cetaceans in the northern Gulf of Mexico (GoM) ... more An unusual mortality event (UME) was declared for cetaceans in the northern Gulf of Mexico (GoM) for Franklin County, Florida, west through Louisiana, USA, beginning in February 2010 and was ongoing as of September 2014. The 'Deepwater Horizon' (DWH) oil spill began on 20 April 2010 in the GoM, raising questions regarding the potential role of the oil spill in the UME. The present study reviews cetacean mortality events that occurred in the GoM prior to 2010 (n = 11), including causes, durations, and some specific test results, to provide a historical context for the current event. The average duration of GoM cetacean UMEs prior to 2010 was 6 mo, and the longest was 17 mo (2005-2006). The highest number of cetacean mortalities recorded during a previous GoM event was 344 (in 1990). In most previous events, dolphin morbillivirus or brevetoxicosis was confirmed or suspected as a causal factor. In contrast, the current northern GoM UME has lasted more than 48 mo and has had mor...
Journal of Experimental Biology, 2014
Diet-tissue discrimination factors (Δ 15 N or Δ 13 C) and turnover times are thought to be influe... more Diet-tissue discrimination factors (Δ 15 N or Δ 13 C) and turnover times are thought to be influenced by a wide range of variables including metabolic rate, age, dietary quality, tissue sampled and the taxon being investigated. In the present study, skin samples were collected from ex situ dolphins that had consumed diets of known isotopic composition for a minimum of 8 weeks. Adult dolphins consuming a diet of low fat (5-6%) and high δ 15 N value had significantly lower Δ 15 N values than animals consuming a diet with high fat (13.9%) and low δ 15 N value. Juvenile dolphins consuming a diet with low fat and an intermediate δ 15 N value had significantly higher Δ 15 N values than adults consuming the same diet. Calculated half-lives for δ 15 N ranged from 14 to 23 days (17.2±1.3 days). Half-lives for δ 13 C ranged from 11 to 23 days with a significant difference between low fat (13.9±4.8 days) and high fat diets (22.0±0.5 days). Overall, our results indicate that while assuming a Δ 13 C value of 1‰ may be appropriate for cetaceans, Δ 15 N values may be closer to 1.5‰ rather than the commonly assumed 3‰. Our data also suggest that understanding seasonal variability in prey composition is another significant consideration when applying discrimination factors or turnover times to field studies focused on feeding habits. Isotope retention times of only a few weeks suggest that, in addition, these isotope data could play an important role in interpreting recent fine-scale habitat utilization and residency patterns.
Journal of Experimental Biology, 2009
The Florida manatee (Trichechus manatus latirostris) is a herbivorous marine mammal that occupies... more The Florida manatee (Trichechus manatus latirostris) is a herbivorous marine mammal that occupies freshwater, estuarine and marine habitats. Despite being considered endangered, relatively little is known about its feeding ecology. The present study expands on previous work on manatee feeding ecology by providing critical baseline parameters for accurate isotopic data interpretation. Stable carbon and nitrogen isotope ratios were examined over a period of more than 1 year in the epidermis of rescued Florida manatees that were transitioning from a diet of aquatic forage to terrestrial forage (lettuce). The mean half-life for 13 C turnover was 53 and 59 days for skin from manatees rescued from coastal and riverine regions, respectively. The mean halflife for 15 N turnover was 27 and 58 days, respectively. Because of these slow turnover rates, carbon and nitrogen stable isotope analysis in manatee epidermis is useful in summarizing average dietary intake over a long period of time rather than assessing recent diet. In addition to turnover rate, a diet-tissue discrimination value of 2.8‰ for 13 C was calculated for long-term captive manatees on a lettuce diet. Determining both turnover rate and diet-tissue discrimination is essential in order to accurately interpret stable isotope data.