Abdominal ultrasonography in Lahille's bottlenose dolphin (Tursiops truncatus gephyreus): Description and reference values

Abstract

The Lahille's bottlenose dolphin (Tursiops truncatus gephyreus) is endemic to coastal waters from southern Brazil to northern Argentina and is listed as Vulnerable, yet veterinary information remains limited and abdominal ultrasonographic reference values are unavailable. Nine clinically healthy dolphins (two females, seven males) under human care were examined using portable ultrasonography. Individuals participated voluntarily following positive reinforcement training. The liver, bile duct, stomachs, intestines, pancreas, spleen, kidneys, urinary bladder, and reproductive organs were evaluated, and standardized measurements were recorded. The pancreas was consistently identified, and the pancreatic duct was visualized and measured in six individuals, representing the first ultrasonographic description of this structure in dolphins. Strong correlations between testicular volume and body weight, total length, and age confirmed its value for assessing reproductive maturity. Renal lithiasis of varying severity was detected in five dolphins. The spleen, however, could only be clearly visualized in two individuals. Regarding the stomach, significant differences were found in specific wall measurements when compared with Tursiops truncatus truncatus, while other parameters were comparable between subspecies. These results provide the first systematic ultrasonographic reference for Tursiops truncatus gephyreus, supporting veterinary care, reproductive monitoring, and conservation efforts. Keywords: Tursiops truncatus gephyreus; Bottlenose dolphin; Abdominal ultrasonography; Pancreatic duct; Testicular biometry; Nephrolithiasis; Gastric wall thickness