TRICAINE METHANESULFONATE (MS-222) SEDATION AND ANESTHESIA IN THE PURPLE-SPINED SEA URCHIN (ARBACIA PUNCTULATA)

Efficacy of anesthetics in an echinoderm based on multifaceted stress biomarkers

Animal care committees remain ambiguous on the need for anesthetics during experimental procedures on invertebrate taxa due to long-standing questioning of their sentience and pain perception. When used, anesthetizing procedures for invertebrates have commonly been adapted from those developed for vertebrates, under the largely unverified assumption that they afford the same benefits. The present study formally tested the efficacy of four common anesthetics of aquatic invertebrates (ethanol, MgCl2, clove oil, MS-222) using behavioural (reaction to physical contact and presence of a predator), physiological (respiration rate), cellular (coelomocytes), and hormonal (cortisol) biomarkers in the holothuroid Cucumaria frondosa (Echinodermata). While subjects recovered from exposures to all anesthetics tested, their responses differed markedly. Ethanol did not immobilize the individuals and concurrently increased their respiration rate, and cellular and hormonal stress markers. MgCl2 and clove oil reduced the behavioural and physiological responses, and decreased the cellular markers, but increased the cortisol levels. Only MS-222 fully immobilized the treated individuals and decreased their respiration rate, both during exposure and throughout ulterior interactions with a predator, while keeping coelomocyte counts and cortisol concentrations at baseline levels. MS-222 thus appears to induce the loss of sensation, representing a promising anesthetic and sedative in soft-bodied aquatic invertebrates.

Effects of seismic water guns on the peristomial membrane of sea urchins (Arbacia lixula, Linnaeus 1758)

The seismic water gun is widely used and plays an important role in seabed imaging acquisition; however, acoustic impacts on marine organisms are currently poorly understood. The aim of this study was to analyse the biochemical responses on the peristomial membrane (PM) of the sea urchin, Arbacia lixula, when exposed to water gun shots in open water. The PM (located around the mouth) is involved in vital functions, such as nutrition and protection. Individuals of sea urchins (n = 7 for each time slot) were sampled before, at the end, and at intervals of 3 h and 24 h after acoustic emission (duration of 20 min). Significant increases in superoxide dismutase, peroxidase, esterase and alkaline were observed immediately after water gun shots, highlighting an increase in the oxidative and inflammatory state of the tissue. Our results showed that acoustic impacts could interfere with PM vital functions, compromising the health, survival and ultimately the conservation of the species. Understanding these effects is crucial to predicting consequences on sea urchin populations and marine ecosystems.

EVALUATION OF IMMERSION IN EMULSIFIED ISOFLURANE OR PROPOFOL AS PART OF A TWO-STEP EUTHANASIA PROTOCOL IN MARBLED CRAYFISH (PROCAMBARUS VIRGINALIS)

The marbled crayfish (Procambarus virginalis) is a parthenogenetic invasive species across much of the world, and when found, euthanasia is often recommended to reduce spread to naïve ecosystems. Euthanasia recommendations in crustaceans includes a two-step method: first to produce nonresponsiveness and then to destroy central nervous tissue. Minimal data exist on adequate anesthetic or immobilization methods for crayfish. A population of 90 marbled crayfish was scheduled for euthanasia due to invasive species concerns. The population was divided into six treatment groups to evaluate whether immersion in emulsified isoflurane or propofol solutions could produce nonresponsiveness. Each group was exposed to one of six treatments for 1 h: isoflurane emulsified at 0.1%, 0.5%, 2%, 5%, and 15% or propofol at 10 mg/L and then increased to 100 mg/L. Crayfish from all treatment groups were moved to nonmedicated water after completion of 1 h and observed for an additional 4 h. All crayfish treated with isoflurane showed lack of a righting reflex at 5 min and loss of movement after 30 min. By 240 min (4 h), none of the crayfish from the isoflurane treatment groups regained movement. None of the crayfish in the propofol treatment achieved loss of reflexes or responsiveness, and all remained normal upon return to nonmedicated water. Isoflurane emulsified in water produces nonresponsiveness that is appropriate for the first step of euthanasia, while propofol was insufficient at these treatment doses.

Practical Euthanasia Method for Common Sea Stars (Asterias rubens) That Allows for High-Quality RNA Sampling

Sea stars in research are often lethally sampled without available methodology to render them insensible prior to sampling due to concerns over sufficient sample quality for applied molecular techniques. The objectives of this study were to describe an inexpensive and effective two-step euthanasia method for adult common sea stars (Asterias rubens) and to demonstrate that high-quality RNA samples for further use in downstream molecular analyses can be obtained from pyloric ceca of MgCl₂-immersed sea stars. Adult common sea stars (n = 15) were immersed in a 75 g/L magnesium chloride solution until they were no longer reactive to having their oral surface tapped with forceps (mean: 4 min, range 2-7 min), left immersed for an additional minute, and then sampled with sharp scissors. RNA from pyloric ceca (n = 10) was isolated using a liquid-liquid method, then samples were treated with DNase and analyzed for evaluation of RNA integrity number (RIN) for assessment of the quantity and purity of intact RNA. Aversive reactions to magnesium chloride solution were not observed and no sea stars regained spontaneous movement or reacted to sampling. The calculated RIN ranged from 7.3-9.8, demonstrating that the combination of animal welfare via the use of anesthesia and sampling for advanced molecular techniques is possible using this low-cost technique.

The effects of tricaine mesylate on arthropods: crayfish, crab and Drosophila

Tricaine mesylate, also known as MS-222, was investigated to characterize its effects on sensory neurons, synaptic transmission at the neuromuscular junction, and heart rate in invertebrates. Three species were examined: Drosophila melanogaster, blue crab (Callinectes sapidus), and red swamp crayfish (Procambarus clarkii). Intracellular measures of action potentials in motor neurons of the crayfish demonstrated that MS-222 dampened the amplitude, suggesting that voltage-gated Na + channels are blocked by MS-222. This is likely the mechanism behind the reduced activity measured in sensory neurons and depressed synaptic transmission in all three species as well as reduced cardiac function in the larval Drosophila. To address public access to data, a group effort was used for analysis of given data sets, blind to the experimental design, to gauge analytical accuracy. The determination of a threshold in analysis for measuring extracellular recorded sensory events is critical and is not easily performed with commercial software.

Establishing a Diagnostic Technique for Coelomocentesis in the Long-Spined Sea Urchin Diadema antillarum

Coelomic fluid aspiration has been utilized in echinoderms in research and clinical settings. Detailed procedural descriptions for coelomic fluid sampling in sea urchins (class Echinoidea) are lacking, and samples are prone to contamination. The objectives of this study were to (1) standardize a technique for coelomic fluid collection in long-spined sea urchin Diadema antillarum that optimizes the diagnostic quality of the sample utilizing diagnostic imaging, (2) identify coelomic fluid bacterial isolates (using Biolog GEN III MicroLog and 16s rDNA sequencing), and (3) compare positive cultures to animal weight, holding time prior to sampling, water temperature, and gross fluid appearance. Seventy Diadema antillarum from the Florida Keys collected in two groups (March and September 2015) were utilized. Positive cultures for bacterial contamination were identified in 5% and 44%, respectively, of animals in the sampling groups. Vibrio spp. was the predominant genus identified. Positive cultures were more frequent in the group with smaller-sized animals, increased holding times, and elevated water temperatures. Deviation from clear-pink gross coelomic fluid appearance did not reliably predict bacterial contamination. A standardized technique for coelomocentesis was defined. The use of the proposed coelomocentesis methodology may facilitate improved health evaluations of sea urchins and may be applicable to research, conservation efforts, and disease investigations.