Evaluation of Egg Incubation Methods and Larval Feeding Regimes for North American Burbot

Incubation methods and larval feeding regimes were investigated for North American burbot Lota lota maculosa over 2 years. Three upwelling incubators were tested: 6.0‐L McDonald‐type jars, 2.0‐L pelagic egg jars, and 1.2‐L Imhoff cones. Larvae were allocated to five feeding regimes in year 1 (trial 1) and three feeding regimes in year 2 (trial 2). In trial 1, a live diet (marine rotifers Brachionus plicatilis and brine shrimp Artemia spp.) was administered from 11 d posthatch (dph) until introduction of a commercial diet at 21, 31, or 41 dph; the fourth treatment applied the commercial diet exclusively starting at 11 dph, and the fifth treatment used only the live diet. Trial 2 examined (1) exclusive use of live feed beginning at 16 dph; (2) use of live feed at 16–50 dph, which was combined with commercial feed at 31–50 dph, and use of only the commercial diet at 51–76 dph; and (3) use of the live diet at 16–50 dph, the addition of frozen brine shrimp at 31–50 dph, and use of the commercial diet at 51–76 dph. Approximate stocking densities for feeding trials were 25 larvae/L in trial 1 and 250 larvae/L in trial 2. Survival and total lengths (TLs) were measured at 52 dph in trial 1 and at 76 dph in trial 2. Incubation trials showed that Imhoff cones or pelagic egg jars significantly improved embryo survival relative to McDonald jars. Larvae fed a live diet for an extended time had significantly higher survival and TLs in both trials. Introduction of a commercial diet at 31 or 41 dph after live‐diet feeding was successful. This study provides a basis for further development of burbot aquaculture

Identifiable neurons inhibited by Earth-strength magnetic stimuli in the mollusc Tritonia diomedea

Diverse animals use the Earth's magnetic field as an orientation cue, but little is known about the sensory, processing and motor elements of the neural circuitry underlying magnetic orientation behavior. The marine mollus

Identification of magnetically responsive neurons in the marine mollusc Tritonia diomedea

Behavioral experiments have demonstrated that the marine mollus

Therapeutic end points for the treatment of atrioventricular node reentrant tachycardia by catheter-guided radiofrequency current

AbstractObjectives. The purpose off this prospective study was to test the hypothesis that the elimination of inducible repetitive atrioventricular (AV) node reentry the persistence of slow AV pathway conduction is a valid end point for radiofrequency catheter ablation procedures in patients with supraventricular tachycardia due to AV node reentry.Background. Although modification of AV node physiology by radiofrequency current can eliminate AV node reentrant tachycardia, therapeutic end points that are definitive of a satisfactory result in patients undergoing modification of the slow AV pathway have not been established. Applications of radiofrequency current at selected sites may eliminate all evidence of slow pathway conduction or sufficiently modify the refractory properties of the slow pathway to preclude sustained arrhythmias. Accordingly, total abolition of dual AV node physiology may not be necessary to prevent arrhythmia recurrence.Methods. Radiofrequency catheter ablation of the slow AV pathway was attempted in 59 patients with typical AV node reentry. Tissue ablation was performed with a continuous wave of 500-kHz radiofrequency current. Twenty-five to 35 W was applied for 60 s at the site selected for destruction.Results. Dual AV node physiology was eliminated completely in 35 patients (59%), persisted without inducible AV node reentry in 13 patients (22%) and persisted with inducible single AV reentrant beats in 11 patients (19%). In patients with persistent dual AV node physiology, the maximal difference between the effective refractory period of the fast and slow pathways was reduced from 104 ± 62 ms before the procedure to 37 ± 37 ms after AV conduction had been modified (p < 0.001). During a mean follow-up interval of 15 months (range 4 to 28), only one patient (2%) had a recurrence of the tachycardia.Conclusions. Resulte demonstrate that when complete elimination of dial AV node physiology is difficult, modification of slow pathway conduction to the extent that repetitive AV node reentry cannot be induced is a definitive end point that portends a good prognosis