| Popis: |
Many physoclist fish have physostomous larvae, initially inflating the swim bladder by ingesting air at the water surface during a brief, finite period. Failed initial swim bladder inflation has been predominantly linked to abiotic factors and larvae which fail to complete initial swim bladder inflation exhibit reduced survival and growth. This study investigates the effects of temperature on initial swim bladder inflation, survival and post-inflation viability (surviving larvae with inflated swim bladders) in striped trumpeter ( Latris lineata ) larvae. Growth, developmental stages and stage-specific larval size are examined in relation to initial swim bladder inflation. Larvae were reared at 12, 14, 16 or 18 °C (Experiment 1) or at 15, 17, 19 or 21 °C (Experiment 2) from day 1 posthatching in replicated 200-l tanks. Initial swim bladder inflation was significantly affected by temperature, with highest initial swim bladder inflation at 14 °C (67.8±5.9% S.E., n =3) to 16 °C (71.1±4.8%) and 15 °C (72.2±1.1%) to 17 °C (76.6±12.0%) in Experiments 1 and 2, respectively. Survival was also significantly influenced by temperature, with the highest survival at 16 °C (31.2±4.9%) to 18 °C (30.6±4.0%) in Experiment 1, and 17 °C (12.4±2.4%) to 19 °C (9.6±2.8%) in Experiment 2. In both experiments, the highest post-inflation viability occurred through a combination of maximum initial swim bladder inflation and survival, at 16 °C (21.3±2.1%) and 17 °C (9.5±1.8%) in Experiments 1 and 2, respectively. Reduced post-inflation viability at 18 and 19 °C was due to decreased initial swim bladder inflation, not survival. The reverse trend was apparent at lower temperatures where survival was significantly lower at 14 and 15 °C, but initial swim bladder inflation remained high. Overlapping optimal temperature ranges for survival and swim bladder inflation narrowed the thermal optima for post-inflation viability to 16–17 °C. Mean size of larvae at initial swim bladder inflation decreased at higher temperatures. Larger larval size at initial swim bladder inflation was positively correlated to increased initial swim bladder inflation at termination in both Experiment 1 ( r =0.780) and Experiment 2 ( r =0.866). It is suggested that this relationship is a key mode of influence of temperature on initial swim bladder inflation. |
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