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Abstract. First culture results are presented from four major experiments (lasting up to 478 days) on the commercially important squid species, Lotigo forbesi Steenstrup, Details are provided on eggs, hatching, feeding, growth, survival, behaviour and sexual maturation. Best survival during the critical first 75 days was 15%. The hatchlings (up to 4 9 mm mantle length, ML) are the largest among the genus Loligo, and the largest squid grown was a male 155mm ML and I24g. First schooling was observed only 40-50 days post-hatching. Spawning was not achieved although males reached maturity, females had maturing ova and mating was observed. The largest giant axon measured was 425^l.m in diameter (from a female 130mm ML), a size suitable for most biomedical applications. Laboratory data suggest a 2-year life cycle compared to fishery data which suggest a 1-year cycle.

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Brief squid Lolliguncula brevis are regularly exposed to fluctuating oxygen levels in their shallow coastal environment. To assess hypoxia resistance, animals were exposed for two hours to ambient oxygen partial pressures (P ) between 19.3 kPa (normoxia) and 6.6 kPa (34.2% air O 2 saturation) at 20618C. In a second set of experiments, the animals were subjected to a low P of O 2 2.860.3 kPa (14.561.6% air saturation) for 15 to 60 min. Subsequently, metabolic, energy and acid-base status were analysed in the mantle tissue. Onset of anaerobic metabolism was observed between 9.4 and 7.9 kPa (48.7 and 40.9% air saturation), reflecting the critical oxygen tension for this species. The formation of octopine and acetate indicates a simultaneous onset of anaerobic metabolism in both the cytosol and the mitochondria during progressive hypoxia. Concomitantly, an intracellular acidosis developed. During exposure to oxygen partial pressures between 19.3 and 6.6 kPa, aerobic and anaerobic processes were sufficient to maintain energy status in the mantle musculature. No significant changes in ATP and phospho-L-arginine (PLA) concentrations were observed. In contrast, both ATP and PLA levels declined significantly after 15 min at an ambient P of 2.860.3 kPa. Concomitantly, the Gibb's free energy change of ATP hydrolysis fell to a O 2 21minimum value of about 244 kJ?mol , a level suggested to reflect limiting energy availability for cellular ATPases. These results indicate that hypoxia at 2.8 kPa (14.5% air saturation) rapidly takes Lolliguncula brevis to the limits of performance. However, it is probably capable of withstanding longer periods of moderate hypoxia close to 50% air saturation (9.7 kPa), enabling the squids to cope with oxygen fluctuations in their shallow estuarine environment or to dive into hypoxic waters by use of their economic jetting strategy. Nonetheless, the critical P is O 2 considered to be high compared to other hypoxia tolerant animals, an observation likely related to the high metabolic rate of these squids.

Lolliguncula brevis Blainville is a small euryhaline squid found at temperatures between 11 and 31 °C. Changes in VO2, heartbeat and ventilation frequencies were observed throughout this temperature range and under a variety of conditions, including acute hypoxia and swimming by jet propulsion in a tunnel respirometer. Resting VO2 showed a Q10 of 1.47, and heart rate and ventilation rate Q10 values of 1.92 and 1.73, respectively; oxygen uptake could exceed 1.01kg−1h−1 at 30°C even at rest. The squids regulated their oxygen uptake at all temperatures. Oxygen extraction rates were in the region of 5–10% in saturated water, increasing to 15–20% in hypoxic water or after exercise. One effect of this variability is that ventilation stroke volume can remain constant throughout the range of temperatures and oxygen concentrations that the animal is likely to encounter, a necessary condition since the ventilation stream is also the principal mode of locomotion by jet propulsion. Blood oxygen-carrying capacity (from the copper concentration) was 4.6 ± 1.8vols%. Cardiac output and stroke volume were estimated from the observed VO2 values and heartbeat frequencies. Resting at 25°C, the output was close to 11.51kg−1 body mass h−1. The systemic heart of Lolliguncula weighed only 2.06 ± 0.62 g kg−1. In exercise the cardiac output must exceed 14×103 1kg−1 heart mass h−1, pumping more than the heart's own mass of blood at each stroke.