EFFECTIVENESS OF THE ANESTHETIC AQUI-S® 20E IN MARINE FINFISH AND ELASMOBRANCHS
Abstract Immersion anesthetics are used in hatchery settings by veterinarians, field biologists, and laboratory researchers to aid in handling finfish for medical procedures, research purposes, and moderating perceived stress responses. The only Food and Drug Administration– (FDA) approved anesthetic for food fish, tricaine methanesulfonate, requires a 21-d withdrawal period prior to harvest. Ten percent eugenol (AQUI-S® 20E) has been gaining momentum for FDA approval because of its 0-d withdrawal time if fish are not of harvestable size within 72 h of exposure. We performed two trials to determine appropriate anesthetic doses for two cultured marine finfish: Atractoscion nobilis (white seabass, WSB) and Seriola lalandi (California yellowtail, YT). Fish were held in a treated water bath for 10 min or until opercular beat rate slowed to a rate of <2 beats/min. Based on these results, we conducted a field trial with wild Paralabrax maculatofasciatus (spotted bay bass), Paralabrax nebulifer (barred sand bass), Paralichthys californicus (California halibut), Triakis semifasciata (leopard shark), and Mustelus californicus (grey smooth-hound) at a single dosing regime, with animals held 5–10 min in anesthetic baths. Anesthetic dosing of 35–55 mg L−1 provided relatively fast induction and good anesthetic maintenance in cultured and wild finfish. Anesthetic induction times were comparable among S. lalandi and A. nobilis at 35–mg L−1 to 75–mg L−1 doses, but recovery times were variable. Mortality rates of 20-90% were observed at higher doses (75 mg L−1 and 100 mg L−1, A. nobilis; 55 mg L−1 and 75 mg L−1, S. lalandi). The apparent increase in sensitivity of S. lalandi may have been associated with nutritional stress in the fish tested. There were no differences in time to anesthesia or recovery among wild finfish species tested at a single dose. Anesthetic induction, maintenance, and recovery were less predictable in the elasmobranch species tested and additional trials are needed to determine optimal dosing.
Research and development of stock management strategies to optimise growth potential in on-growing of Atlantic cod, Gadus morhua, and Atlantic halibut, Hippoglossus hippoglossus
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Molecular characterization and expression of FSHbeta, LHbeta, and common alpha-subunit in male Atlantic halibut (Hippoglossus hippoglossus).
To elucidate the role of the gonadotropins in the multiple spawner Atlantic halibut (Hippoglossus hippoglossus) full length cDNAs encoding FSHbeta, LHbeta, and the common alpha-subunit were cloned from pituitary glands by RACE-PCR. The three cDNAs consisted of 614, 595, and 666 nucleotides encoding peptides of 131, 146, and 124 amino acids, respectively. Halibut FSHbeta and LHbeta showed unique structural features among the vertebrate glycoprotein hormones. First, in contrast to all known FSHbeta, which contain either one or two conserved N-glycosylation sites, no potential binding site was found in Atlantic halibut FSHbeta. Second, the conserved glycosylation site in the N-terminus of all vertebrate LHbeta has been substituted with a unique C-terminal binding site in Atlantic halibut LHbeta. Furthermore, a specific cysteine residue of importance for the folding and heterodimerization of mammalian FSH is lacking in the FSHbeta from Atlantic halibut as well as many other teleosts. However, teleost FSHbeta is characterized by an additional N-terminal cysteine, which has likely replaced the missing residue, implicating a modified folding pattern of this subunit. In situ hybridization of mature male pituitaries revealed that FSHbeta and LHbeta mRNA were expressed in distinct cell types throughout the proximal pars distalis of the adenohypophysis, while alpha-subunit mRNA was identified in all parts of the proximal pars distalis, and also along the periphery of pars intermedia. Consistently, Northern blot analysis of pituitary RNA from mature males showed that FSHbeta, LHbeta, and alpha-subunit mRNAs were highly expressed. In juvenile male pituitaries very few cells containing FSHbeta, LHbeta, and alpha-subunit mRNA were identified by in situ hybridization. Low mRNA levels encoding LHbeta and the alpha-subunit were also demonstrated by Northern blot analysis of the juvenile pituitaries, while no FSHbeta mRNA was detected using this less sensitive technique. The results suggest that both FSH and LH play a role during both the very early and the final reproductive stages in Atlantic halibut males.