Ultrasound-guided sampling of the lateral abdominal vein in the grey nurse shark (Carcharias taurus, Rafinesque 1810)

The Establishment of an Optimal Protocol for Contrast-Enhanced Micro-Computed Tomography in the Cloudy Catshark Scyliorhinus torazame

The purpose of this study was to determine the optimal imaging protocol for contrast-enhanced computed tomography (CECT) using micro-CT (μ-CT) for the posterior cardinal vein (PCV), dorsal aorta (DA), hepatic portal vein (HPV), kidney, liver, cephalic arteries (CAs), and gills of Cloudy Catsharks Scyliorhinus torazame. Additionally, we examined the availability of CECT screening for the coelomic organs. Different doses of iopamidol (100, 300, 500, and 700 mg iodine [mgI]/kg) were administered intravenously for 20 s in six sharks. The CT scans from the pectoral girdle to the pelvic girdle were performed at 0-600 s after administration. Contrast-enhanced CT imaging of the CAs, gills, and coelomic organs was examined. Assessment of the signal enhancement value revealed that the PCV was easily visualized with all contrast doses at 25 s. The CAs, gills, and DA were visible at a slightly higher dose (CAs and gills: 200 mgI/kg at 40 s; DA: 300 mgI/kg at 50 s). The HPV was obvious at a dose of at least 500 mgI/kg after a 150-s delay. The parenchyma of the kidney had a contrast effect at 300 mgI/kg, 150 s after the contrast effect of the renal portal system disappeared. The liver, which stores a lot of lipids, had poor overall contrast enhancement that was optimized at the highest dose of 700 mgI/kg. Contrast-enhanced CT screening at 700 mgI/kg and 150 s is likely to obtain the optimal imaging of the reproductive organs, such as the ovary, oviducal gland, uterus, and testis. The present findings can be applied not only to clinical practice but also to academic research and education on elasmobranchs in aquariums.

Ultrasound-guided sampling of the lateral abdominal vein in the grey nurse shark (Carcharias taurus, Rafinesque 1810)

The paired lateral abdominal veins (LAV) provide alternative venipuncture sites in grey nurse sharks (Carcharias taurus, Rafinesque 1810) and their efficacy was assessed using morphometrics, necropsies, ultrasound-guided blood sampling and by comparing serum biochemistry between the LAV and caudal vein (CV) with values from the latter published previously. The mean length of the CV was 2.8% of total length (TL) whereas each LAV was 22.4% of TL and, when combined, was approximately 16 times longer than the CV. The mean tissue thickness overlying each LAV increased significantly (p < .001) with increasing TL and ranged from 3.5 to 33.8 mm in the smallest to largest shark. The mean internal diameter of the paired LAV also increased significantly (p < .001) with increasing TL and was equal to or exceeded the CV. Experienced SCUBA divers captured 56 free-living grey nurse sharks and 46 healthy animals were sampled for blood from the LAV and CV with minimal risk to the animals or staff. Venipuncture of the LAV (n = 16) was easily accomplished using ultrasound guidance with a 38 mm/18-gauge needle, whereas standard methods were used with the CV (n = 30). Serum biochemistry was compared (t-tests) and none of the biochemical analytes differed significantly between the LAV and CV. The paired LAV produced representative blood samples and could also be used for fluid therapy and/or intravenous anaesthesia as has been done in other sharks. It is recommended that veterinary/husbandry staff familiarize themselves with the paired LAV and consider their use in the future.