Mississippi State University - Global Center for Aquatic Health and Food Security
Mississippi State University - Global Center for Aquatic Health and Food Security
Dr. Beth Peterman
Program overview
Jill B. Hudnall1.2, Thomas G. Rosser3, Beth Peterman1,2, Kaylin McNulty1,2,
Justin M. Stilwell1,2, Ethan T. Woodyard2, Stephen R. Reichley1,2
1. Global Center for Aquatic Health and Food Security, Mississippi State University, Mississippi State, Mississippi, USA; 2. Department of Pathobiology and Population Medicine, College of Veterinary Medicine, Mississippi State University, Mississippi State, Mississippi, USA; 3. Department of Comparative Biomedical Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, Mississippi, USA
The bottlenose dolphin, Tursiops truncatus, is one of the top predators in marine ecosystems and is considered a keystone species. As apex predators, they play a vital role in the regulation of prey species populations and have been utilized as a bioindicator of marine ecosystem health. Diagnostic investigations into mortality events and strandings provide researchers with valuable information to bolster conservation efforts and understand disease transmission. As part of the Marine Mammal and Sea Turtle Health Program performed in collaboration with the Institute of
Marine Mammal Studies (IMMS), necropsies of bottlenose dolphins stranding in the Mississippi Sound have been conducted since 2018. While many of the bacterial, viral, and fungal pathogens have been examined, limited work has been done examining the impacts of endoparasitic helminths of bottlenose dolphins. One such helminth is the diplostomoidean trematode Braunina cordiformis found rigidly affixed to the mucosa of the pyloric stomach and duodenal ampulla. First described in the early 1900s, initial accounts provide limited descriptions of parasite morphology and host-parasite interactions. Currently molecular data suggests the biodiversity of Braunina spp. is greater than previously estimated and possibly novel species remain to be described in dolphins. Adult Braunina sp. were excised from eleven dolphins ranging in age from calf to adult that were necropsied between 2019-2024 and preserved in ethanol, 10% formalin, and frozen in -20C. Genomic DNA was extracted from a subsample of adult trematodes for molecular analysis using next generation sequencing via Oxford Nanopore and Illumina sequencing to generate a complete mitochondrial genome and the entire nuclear ribosomal regions. An excised piece of tegumental tissue was used to produce hologenophores. Mitochondrial cytochrome oxidase c subunit 1 gene comparisons with publicly available data in Genbank suggest our species to be an undescribed Braunina sp. These molecular data will be used to supplement morphological data, infer evolutionary histories of the genus via phylogenetic analyses and link together larval stages sampled from intermediate hosts. While the life cycle is currently unknown, putative intermediate host species consumed as prey by bottlenose dolphins in the Mississippi Sound include marine catfish, pinfish, pigfish, and mullet. Several of these fish utilize sea grass beds found off the barrier islands of the Mississippi Sound where possible molluscan intermediate hosts may be found. Future efforts consist of examining fishes, aquatic vegetation, and snails to determine intermediate hosts for life cycle elucidation. Our current hypothesis is that soniferous fishes found in sea grass beds located on the barrier islands act as intermediate hosts and harbor metacercariae. Evaluation of stomach contents will be used to establish a baseline of fish families preyed upon by dolphins infected with Braunina. Understanding the broad array of endoparasites affecting dolphins is of utmost importance to understand any roles parasites may play in impacting overall health.
Ryanne Murray1,2 , Barbara Kaplan1,3 , Beth Peterman1,2 , Kaylin McNulty1,2 , Debra Moore1,2
1. Global Center for Aquatic Health and Food Security, Mississippi State University, Mississippi State, Mississippi, USA; 2. Department of Pathobiology and Population Medicine, College of Veterinary Medicine, Mississippi State University, Mississippi State, Mississippi, USA ; 3. Department of Comparative Biomedical Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, Mississippi, USA
Bottlenose dolphins (Tursiops truncatus) are native to the Mississippi Sound, a region characterized by significant human activity that can contribute to elevated levels of environmental pollutants such as polychlorinated biphenyls (PCBs) and polyaromatic hydrocarbons (PAHs). As apex predators, bottlenose dolphins bioaccumulate these contaminants in their tissues over time as they grow and age. Straight-length measurements can be used to estimate the age class of dolphins. For this research, we divided the dolphins into three age classes based on straight length: perinates (<115 cm), sub-adults (116-199 cm) and adults (>200 cm). Along with the size of the animal, sex can also influence contaminant levels, as females transfer contaminants to their offspring during pregnancy, resulting in lower contaminant levels in adult females compared to males.
Our research focused on detecting PAHs and PCBs in tissues of 138 bottlenose dolphins that stranded in the Mississippi Sound from 2010 to 2021. Tissue samples (blubber, kidney, liver, and muscle) were collected from necropsies performed at the Institute for Marine Mammal Studies in Gulfport, Mississippi and analyzed for 24 PAHs and 7 PCBs at the Mississippi State Chemical Laboratory in Starkville.
Results indicated that 9 out of 24 PAHs were detected, with naphthalene being the most frequently found, particularly in blubber and liver tissues. All PCBs were consistently detected across these tissues from 2010-2021. To examine contaminant levels on age, we focused on PCB 153 and naphthalene in blubber, as these were the most common contaminants present. PCB 153 levels in blubber showed a positive trend, increasing in older animals, while naphthalene levels exhibited a negative trend, with younger animals having higher values. Adult males had a higher level of PCB 153 in the blubber tissue compared to adult females, this can be explained by the offloading of toxins by females during pregnancy.
The presence of these contaminants may impact the overall health of this dolphin population, highlighting the importance of long-term surveillance. Our next step for this project is to compare the contaminant levels in dolphin tissues with those in the tissues of their common prey items. This comparison will help us better understand the sources and bioaccumulation of these contaminants.