We immersed southern pygmy squid, Idiosepius notoides Berry 1921 (hereafter squid), in three anesthetics (cold seawater, magnesium chloride [MgCl 2 ], and ethanol [EtOH]). Anesthesia was important for inducing both immobility and body transparency, conditions that were required for measuring extracellular lipid droplets. Cold anesthesia (4°C, day 1) led to frequent inking and some mortality. The MgCl 2 treatment (1-5%, day 18) did not induce body transparency and was often lethal. The 2% EtOH anesthesia (12-15°C, days 1-12) was most successful: it induced no inking and was followed by 100% recovery and postanesthetic survival (>7 days). There was no difference in induction times for squid anesthetized on day 1 versus day 2 after collection, with loss of body color patterns in -12 sec followed by loss of mobility at -30 sec. Time to immobility was related to time to transparency. Size (dorsal mantle length) was not related to time to induction or recovery. Although all squid survived three anesthesias with 2% EtOH, third inductions were significantly slower than first inductions. Anesthesia greatly improved accuracy of locating, counting, and measuring lipid droplets. With sublethal anesthesia, we detected extracellular lipid droplets in the digestive system of all 42 freshly collected squid. Without anesthesia, we failed to see cecal droplets in 20 of 41 squid that had them, and we failed to see digestive gland droplets in five of 23 squid that had them. Light EtOH anesthesia, including repeated treatments, did not seem to move droplets between the digestive cecum and the digestive gland or to induce expulsion of these droplets from the digestive tract.
|Number of pages||14|
|Publication status||Published - 16 Nov 2012|