The Eastern oyster (Crassostrea virginica) is a useful, robust model marine organism for tissue metabolism studies. Its relatively few organs are easily delineated and there is sufficient understanding of their functions based on classical assays to support interpretation of advanced spectroscopic approaches. Here we apply high-resolution proton nuclear magnetic resonance (¹H NMR)-based metabolomic analysis to C. virginica to investigate the differences in the metabolic profile of different organ groups, and magnetic resonance imaging (MRI) to non-invasively identify the well separated organs. Metabolites were identified in perchloric acid extracts of three portions of the oyster containing: (1) adductor muscle, (2) stomach and digestive gland, and (3) mantle and gills. Osmolytes dominated the metabolome in all three organ blocks with decreasing concentration as follows: betaine > taurine > proline > glycine > ß-alanine > hypotaurine. Mitochondrial metabolism appeared most pronounced in the adductor muscle with elevated levels of carnitine facilitating ß-oxidation, and ATP, and phosphoarginine synthesis, while glycogen was elevated in the mantle/gills and stomach/digestive gland. A biochemical schematic is presented that relates metabolites to biochemical pathways correlated with physiological organ functions. This study identifies metabolites and corresponding ¹H NMR peak assignments for future NMR-based metabolomic studies in oysters.

Intravascular access in batoid species is commonly achieved using the ventral coccygeal or radial wing vessels. However, these approaches can be difficult because of the presence of cartilage, lack of specific landmarks, species variation, and small vessel size in many species. This study used postmortem contrast radiography and gross dissection to develop landmarks for a new, dependable vascular access in three Myliobatiform species commonly maintained in captivity: Atlantic stingray (Hypanus sabinus), cownose ray (Rhinoptera bonasus), and smooth butterfly ray (Gymnura micrura). The mesopterygial vein provides quick vascular access and is suitable for administration of large fluid volumes and intravascular drugs. It is located immediately ventrolateral to the metapterygium cartilage, which sits adjacent to the coelomic cavity and supports the caudal half of the pectoral fin. Using the pectoral girdle and cranial third of the metapterygium cartilage as landmarks, vascular access can be achieved by directing a needle medially at approximately a 30° (adult cownose rays) or 45° angle (Atlantic stingrays, juvenile cownose rays, smooth butterfly rays) toward the metapterygium cartilage. Differences in the degree of needle direction are due to species and age-specific shapes of the metapterygium cartilage. The mesopterygial vein is an alternate site of quick and reliable venous access in batoid species.

Immersion euthanasia methods reported over the most recent decades for aquatic invertebrates use organic alcohols or halogenated hydrocarbons that can interfere with nuclear magnetic resonance (NMR) analysis. A rolling study design evaluated potassium chloride (KCl), magnesium chloride (MgCl₂), and magnesium sulfate (MgSO₄) as potential ion-based euthanasia methods for moon jellyfish (Aurelia aurita) destined for metabolomic analysis by NMR spectroscopy. Death was defined as the cessation of autonomous bell pulsing and response to external stimulus. MgCl₂ applied at a dose of 142 g/L provided euthanasia within 32 sec of applications without the untoward effects observed with the other two salts. Euthanasia with KCl at the doses tested was associated with abnormal behavior and tissue degradation during dissection. MgSO₄ at the doses tested resulted in abnormal behavior and failed to provide rapid euthanasia.

Seventeen recently trapped opossum, Didelphis virginiana, (median weight 2.45 kg; range = 1.6-5.0 kg; quartiles = 1.8-3.3 kg) were immobilized with either telazol (15 or 30 mg/kg) or a mixture of medetomidine (100 micrograms/kg), butorphanol (0.2 mg/kg), and ketamine HCl (10 mg/kg) based on estimated weights. Anesthetized animals were subjected to cardiac puncture for blood withdrawal and toe pinch. Euthanasia was accomplished by intracardiac administration of 1 ml of concentrated pentobarbital sodium/phenytoin solution. Weights were underestimated for 14 of 17 animals, but were within 0.5 kg of the actual weight. Both drug combinations provided rapid and calm immobilization. Median time to recumbency for the medetomidine-butorphanol-ketamine group (n = 5) was 6 min (range = 4-10 min; quartiles = 6 and 8 min). The median time to recumbency was not statistically different for the low (n = 6) and high dose (n = 6) telazol groups, 3 and 3.5 min respectively (quartiles 3; 3.5 and 4; 5.5 min). The stronger heart beat with telazol immobilization facilitated cardiac puncture. All five animals administered the medetomidine-butorphanol-ketamine mixture and three of six animals given the low telazol dose reacted to cardiac puncture. Only one of six animals given the estimated 30 mg/kg dose of telazol reacted slightly to cardiac puncture. We conclude that 30 mg/kg telazol provides sufficient immobilization and analgesia to allow accurate cardiac puncture of the opossum if the procedure is performed within 5 to 10 min of recumbency. Intracardiac administration of concentrated pentobarbital sodium/phenytoin solution followed by bilateral thoracotomy provides appropriate euthanasia suitable for field situations.