Essential oil of Ocimum basilicum and Eugenol as Sedatives for Nile Tilapia

This study evaluated the modulation of the ventilatory frequency of Nile tilapia sedated with essential oil of Ocimum basilicum and eugenol. The fish were exposed to the following treatments: control (water only); ethanol 200 µl L-1 (concentration used to dilute the anesthetic); eugenol 10 µl L-1 and 20 µl L-1; essential oil of O. basilicum at the concentration of 10 µl L-1 and 20 µl L-1. After 90 minutes of exposure to the treatments, water quality, mortality and respiratory rate were determined. The concentration of 20 µl L-1 of the essential oil of O. basilicum and eugenol showed a sedative effect and reduced the excretion of metabolic ammonia in Nile tilapia. There was no mortality in fish exposed to the treatments. The respiratory rate did not differ between the different treatments. It is concluded that the concentration of 20 µl L-1 of the essential oil of O. basilicum and eugenol shows the best result in the inducing sedative effect for Nile tilapia, and that the essential oil of O. basilicum and eugenol in the concentrations of 10 µl L-1 and 20 µl L-1 in an exposure period up to 90 minutes do not alter the ventilatory frequency of Nile tilapia.

Control of breathing in craniotes

Craniote gills are arranged sequentially along the pharynx and accordingly are ventilated from anterior to posterior by a wave of muscle contraction, beginning with the mouth. Each gill pair appears to have its own set of neurons in the brainstem that coordinate the muscle activity and stimulate the next gill pair in the sequence. This system appears to have been maintained from hagfish to teleosts. In tetrapods, on the other hand, various centres in the brainstem coordinate different phases of breathing: expiration, inspiration, and post-inspiration. The location of these centres in the brainstem is similar in amphibians and mammals. The stimulus for regulating ventilatory frequency in water-breathing species is oxygen, whereas for air-breathing species it is blood pH/PCO2—just as in invertebrates.

Anesthetic potential of the essential oils of Lippia alba and Lippia origanoides in Tambaqui juveniles

ABSTRACT: The aim of this study was to investigate the anesthetic effect of the essential oils (EOs) of Lippia alba (citral and linalool chemotypes, EOLA-C and EOLA-L respectively) and Lippia origanoides (chemotype carvacrol, EOLO-Ca) on tambaqui (Colossoma macropomum) juveniles. The tested concentrations of the L. alba and L. origanoides EOs were: 25, 50, 100, and 200 μL/L. Time required to reach the stages of sedation, deep anesthesia, and recovery, as well as ventilatory frequency, were monitored for each EO concentration. The results indicated that all EO concentrations tested induced tambaqui anesthesia and that the ventilatory frequency was altered by the EOs. L. origanoides showed the shortest time to induce sedation and anesthesia, but had long recovery times. L. alba EO (citral 100 μL/L and linalool 200 μL/L) can be used to efficiently anaesthetise tambaqui juveniles with an efficient recovery.

Ventilatory frequency as a measure of the response of tammar wallabies (Macropus eugenii) to the odour of potential predators

This study uses changes in ventilatory frequency to quantify the physiological response of an Australian terrestrial herbivore, the tammar wallaby (Macropus eugenii), to olfactory cues suggesting the presence of potential predators. Ventilatory frequency proved to be a quantifiable measure to assess the response of this macropod marsupial to olfactory cues. Ventilatory frequency increased from mean resting levels of 45 ± 5.1 breaths min–1 to 137 ± 11.2 breaths min–1 during the first minute of exposure to all odours. These physiological responses diminished over time, with ventilatory frequency in the first minute after introduction of the scents greater than that during the subsequent four, suggesting that the initial reaction was due to disturbance and was investigative in nature. However, the ratio of ventilatory frequency in the remaining 4 min after introduction of the odours compared with before was greater for fox (3.58 ± 0.918) and cat (2.44 ± 0.272) odours than for snake (2.27 ± 0.370), distilled water (1.81 ± 0.463) and quoll (1.71 ± 0.245) odours, suggesting that fox and cat odour provoked a greater response. However, the wallabies’ response to the odour of these introduced predators and to horse odour (2.40 ± 0.492) did not differ. Our study indicates that a long period of co-history with particular predators is not a prerequisite for detection of potentially threatening species. We do not find any support for the hypothesis that an inability to interpret olfactory cues to detect and respond to potential predation by introduced predators is responsible for the decline of these macropod marsupials.