Field metabolic rates – exhalation sampling technique

A device is placed over this dolphin’s blow hole in order to measure oxygen concentrations as the dolphin inhales and exhales. These data can then be used to determine the animal’s metabolic rate.
A device is placed over this dolphin’s blow hole in order to measure oxygen concentrations as the dolphin inhales and exhales. These data can then be used to determine the animal’s metabolic rate.

Dolphins, like all mammals, have lungs and breathe air. Metabolic rate, an indication of the energy used by an organism, can be described from counting how many molecules of oxygen are consumed over a given period of time. We recently developed a device that can be used to estimate the metabolic rate in dolphins in the field (such as from a boat). The device consists of a flow-meter that measures the amount of air they inhale and exhale, and also measures the concentration of oxygen when they exhale. Together, the flow and gas concentration are used to determine the metabolic rate. In addition to metabolic rate, these measurements can be used to look at other things, like lung health. Human doctors use similar equipment and measurements, in a process called pulmonary function testing, to look at lung health in people. Respiratory disease is very serious for dolphins and can be life threatening. If an unusually large number of dolphins have respiratory disease, this may indicate that there is an infectious disease spreading (this was recently the case with morbillivirus on the east coast of the U.S.) or that there is a problem in the ecosystem. By comparing respiratory health in different populations of dolphins, we can learn more about the health of those populations, and the marine environment in which they live.

We are also using this equipment to study how dolphins and whales dive to extreme depths and hold their breath for such a long time. For example, the dolphins in Sarasota Bay generally dive to depths up to a maximum of 6 meters, while members of the same species of dolphins in Bermuda dive to depths over 900 meters. Working with the SDRP and Dolphin Quest has allowed us to collect respiratory data from free-ranging dolphins in order to learn more about their incredible physiology and diving ability, their health, and the ecosystem we all share with these amazing animals.

This article appeared on page 16 in the December 2015 issue of Nicks n Notches.

 

Bottlenose dolphin immunology

The immune system is very important in an individual’s defense against pathogenic microorganisms that live in one’s environment. Our work with Sarasota Bay dolphins has helped us better understand the normal immune system of bottlenose dolphins and establish reference intervals that can be used to assess the potential effects of man-made or natural stressors, such as the Deepwater Horizon oil spill in the northern Gulf of Mexico.

Using blood samples collected during bottlenose dolphin health assessments, our University of Connecticut lab has measured the function of different white blood cell types using functional assays. These assays include the ability of neutrophils and monocytes to engulf foreign particles approximately the size of bacteria (phagocytosis), as well as their ability to produce oxygen free radicals to kill such ingested microorganisms (respiratory burst). We also measure the ability of B and T lymphocytes to proliferate upon stimulation, which mimics the early phase of an immune response. Further, following preliminary results obtained in previous years, we validated the quantification of serum cytokines, which are small messenger molecules that direct the magnitude and direction for an appropriate immune response. The results obtained with Sarasota Bay dolphins have allowed, for the first time, the determination of confidence intervals (“normal values”) for some of those functions for which sufficient numbers of animals have been sampled. Building on past year successes, samples from May 2015 will help fill the gaps and determine reference intervals for additional immune functions. Those results in a relatively healthy population are currently used to assess the potential health effects of the recent exposure of dolphins to oil following the Deepwater Horizon spill.

This work has been supported in part by the Chicago Zoological Society, who provided logistical support and access to dolphin samples in Sarasota Bay over many years, as well as continued support from NOAA for similar analyses at different locations in the Gulf of Mexico.

This article appeared on pages 13-14 in the December 2015 issue of Nicks n Notches.

 

Could a Sarasota Bay dolphin’s diet help reverse diabetes?

Bottlenose dolphins in the wild and under human care can develop metabolic syndrome, which is similar to prediabetes in humans. Nutrition research led by the National Marine Mammal Foundation (NMMF) and in collaboration with the SDRP resulted in the discovery of a saturated fatty acid in fish that appears to reverse metabolic syndrome in dolphins.

Metabolic syndrome is a subclinical condition involving blood changes, including elevated insulin, lipids, and ferritin. Today in the U.S., one in every three adults has metabolic syndrome. Because of the increasing human health interest in fish-based omega-3 fatty acids, we measured 55 fatty acids in 49 dolphins (19 from Sarasota Bay and 30 from the U.S. Navy Marine Mammal Program), as well as in their different dietary fish types. Dolphins with higher blood levels of C17:0 (also called heptadecanoic acid) were more likely to have lower, healthier insulin and ferritin. Interestingly, fish types commonly eaten by Sarasota Bay dolphins (pinfish and mullet) had relatively high C17:0 content compared to other fish types. When we fed dolphins a diet higher in C17:0, their serum ferritin decreased within 3 weeks, insulin sensitivity increased within 12 weeks, and insulin, glucose, and lipids normalized within 6 months. This Office of Naval Research funded discovery was published in PLOS ONE during July 2015 and was highlighted on National Public Radio’s Science Friday. While continuing to understand how changes in the ocean and prey influence C17:0 availability in fish, NMMF is also collaborating with children’s hospitals to assess the ability to reverse metabolic syndrome in children by providing a diet higher in C17:0.

This article appeared on page 13 in the December 2015 issue of Nicks n Notches.

 

Sarasota Bay dolphins shine a light on kidney stone disease

 

Dr. Cynthia Smith and Dr. Jen Langan performing an ultrasound examination.
Dr. Cynthia Smith and Dr. Jen Langan performing an ultrasound examination.

Kidney stone disease is known to affect bottlenose dolphins and can lead to kidney obstruction, failure, and organ death. Certain populations or collections of dolphins appear to be more at risk than others for kidney stone formation. To better understand the problem, we set out to study kidney health in Sarasota Bay dolphins to determine whether or not this population is afflicted with the disease.

Ultrasound provides a rapid assessment of organ health in humans and animals, including bottlenose dolphins. During 2011-2013, we gathered ultrasound data on Sarasota Bay dolphin kidneys to look for evidence of kidney stones. Thirty-nine dolphins were screened for the disease, and none of the dolphins had evidence of stone formation, which is great news for the population.

Sarasota Bay dolphins now serve as an unaffected, control population for kidney stone disease. Studying their urine physiology can help us determine how they are protecting themselves from stone formation. In 2014, we conducted ultrasound exams to confirm that the dolphins being examined had no evidence of stone disease. We also collected urine from as many of the study dolphins as possible, and then performed sophisticated analyses on the urine samples.

We discovered that Sarasota Bay dolphins have similar urine chemistry to dolphins that form stones, however some key differences exist. First, Sarasota Bay dolphins have higher levels of citrate in their urine, therefore citrate may be playing a role in inhibition of stone formation. Second, Sarasota Bay dolphin urine is supersaturated with ammonium urate, which is the stone type most commonly diagnosed in dolphins. However, the level of supersaturation is greater in a collection of animals with a high prevalence of stone formation. The difference in supersaturation indices may prove critical and is likely related to foraging behavior and prey types. Future studies will focus both on inhibitory factors and the influence of foraging behavior on the risk of stone formation, continuing to utilize Sarasota Bay as a healthy, control population of dolphins. Our collaborators for this project include SDRP, Dolphin Quest, and the University of Florida. We thank the Office of Naval Research for their continued support of this project.

This article was published on page 13-14 in the November 2014 issue of Nicks n Notches

Influence of genetic variation on susceptibility to harmful algal blooms

 Map of study areas in the Florida Panhandle (A) and central-west Florida (B) indicating the location of sample collection for live coastal (blue stars) and estuarine (black circles) bottlenose dolphins and dolphin strandings during UMEs in the Panhandle in 1999 (blue circles) and 2004 (black stars) and during HABs between 1992 and 2006, including a UME in 2005-2006, in central-west Florida (blue circles).
Map of study areas in the Florida Panhandle (A) and central-west Florida (B) indicating the location of sample collection for live coastal (blue stars) and estuarine (black circles) bottlenose dolphins and dolphin strandings during UMEs in the Panhandle in 1999 (blue circles) and 2004 (black stars) and during HABs between 1992 and 2006, including a UME in 2005-2006, in central-west Florida (blue circles).

This past year marks the successful completion of my dissertation research on bottlenose dolphin susceptibility to harmful algal blooms (HABs), otherwise known as red tides. Over the past five years, through collaboration with the Sarasota Dolphin Research Program and NOAA Fisheries, I have used genetic techniques to investigate apparent differences in red tide resistance among bottlenose dolphins from central-west Florida and the Florida Panhandle.

Red tides in the Gulf of Mexico refer to naturally occurring dense blooms of the dinoflagellate algae, Karenia brevis, which produce neurotoxins. Exposure to these toxins can be lethal to fish, sea birds, sea turtles, and marine mammals, and can cause illness in humans. Several unusual mortality events (UMEs) of dolphins in Florida have been attributed to red tides. The goal of my research was to investigate if dolphins that have been frequently exposed to red tides historically have evolved resistance to the algal toxins. To test this hypothesis, I compared genetic variation between dolphins that died due to red tides and dolphins that survived red tide exposure, looking for a genetic signal that was more commonly observed in one group over the other. I included dolphins from both estuarine and coastal populations of bottlenose dolphins in central-west Florida (including Sarasota Bay) and the Florida Panhandle (see map).

I found that the frequency of some genetic markers varied significantly between live and dead dolphins, suggesting there may be some genetic basis to red tide resistance. The significant genetic markers were found within the dolphin genome nearby to genes involved in immune, nervous, and detoxification systems. A closer look at dolphin sodium channel genes, which encode the biological binding site of the toxin, revealed no significant differences. Unlike other neurotoxin-resistant systems (e.g., garter snakes that prey on toxic newts and clams exposed to HABs in New England), bottlenose dolphins have not adapted to red tide exposure via adaptations to the toxin binding site. Instead, the dolphin immune system, particularly the major histocompatibility complex, may play a previously undescribed role in red tide resistance. Overall, I conclude that genetics is likely one of several factors that influence the susceptibility of individual bottlenose dolphins to red tide exposure.

This research was supported by the Duke University Marine Lab, the American Fisheries Society, the PADI Foundation, and a Katherine Goodman Stern Fellowship. Samples were generously provided by the NOAA Fisheries SEFSC DNA Archives and the Sarasota Dolphin Research Program.

This article was published on page 15 in the November 2014 issue of Nicks n Notches