Effect of acclimation temperature on thermoregulatory behaviour,thermal tolerance and respiratory metabolism of Lutjanus guttatus and the response of heat shock protein 70 (Hsp70) and lactate dehydrogenase (Ldh‐a) genes

This study evaluated the effect of different environmental temperatures in the physiology of Lutjanus guttatus juveniles by analysing their thermoregulatory behaviour, thermal tolerance, oxygen consumption rates and thermal metabolic scope. Jointly, the effect of acclimation and critical temperatures on heat shock protein 70 (Hsp70) and lactate dehydrogenase (Ldh‐a) gene expressions were also analysed using acclimation temperatures of 20, 23, 26, 29 and 32°C. The results showed that the final preferred temperature in juvenile snapper was 26°C with a thermal window of 336.5°C², which was related to an optimal temperature for their physiology determined by the routine metabolic rate and thermal metabolic scope. At temperatures from 20 to 26°C, the routine metabolic rate and Hsp70 and Ldh‐a genes had the lowest values related to a basal expression level. At acclimation temperatures from 29 to 32°C and after critical thermal maximum (CT_max) limit, the relative expression of Hsp70 and Ldh‐a genes increased significantly, but the main response at CT_max was the upregulation of Hsp70 gene.     

Effects of temperature on growth of juvenile blackfoot abalone, Haliotis iris Gmelin

The effects of temperature on growth and survival of juvenile blackfoot abalone, Haliotis iris, were investigated. Animals of 10, 30 or 60 mm initial shell length were exposed to ambient (6–10°C), 14, 18, 22 and 26°C for 112 days in a flow‐through culture system. Maximum growth occurred at 22°C for the 10 and 30 mm size classes and at 18°C for the 60 mm size class. Regression analysis identified the optimal temperature for growth (T_optG) at around 21°C for the 10 and 30 mm size classes and at 17–18°C for the largest size class. In a second experiment, the critical thermal maximum of H. iris was determined as a measure of thermal tolerance. Abalone were subjected to increasing water temperatures at a rate of 2°C h^?1 until they detached from the substrate. Abalone of 10 mm displayed greater thermal tolerance than abalone of 30 and 60 mm in length. CT₅₀ temperatures were 28.8, 27.7 and 27.8°C, yielding deduced T_optG values of 19.7, 18.3 and 18.4°C for the 10, 30 and 60 mm size classes respectively. The size‐dependent nature of the relationship between growth and temperature could be capitalized upon in recirculating aquaculture systems.     

Effects of air exposure on the lysosomal membrane stability of haemocytes in blacklip abalone, Haliotis rubra (Leach)

The neutral red retention (NRR) assay was used to evaluate the effects of air exposure on lysosomal membrane integrity in the haemolymph of blacklip abalone, Haliotis rubra, and its subsequent recovery in water. After acclimation in 16°C water for 7 days, abalone were exposed to an air temperature of 7, 16 or 23°C for 12 h in the air exposure experiment or to these three air temperatures, e.g., for 12, 24 or 36 h, followed by re‐immersion in 16°C water in the lysosomal membrane stability recovery experiment. Statistical analyses of the air exposure experiment showed that when abalone were exposed to different air temperatures (7, 16 or 23°C), the lysosomal membrane stability was significantly affected by the air temperature, the exposure duration and their interaction. Air temperature similar to the acclimation temperature had a significantly lower impact on the lysosomal membrane stability within the initial 4.5 h in comparison with the other two temperatures in the same period. The lysosomal membrane stability recovery experiment showed that after air exposure durations of 12, 24 or 36 h, the re‐stabilization of the lysosomal membrane was faster in the animals exposed to lower temperatures than those exposed to higher temperatures. The recovery of the lysosomal membrane stability in abalone exposed to lower 7°C air temperature was not significantly affected (F_{2, 66}=0.251, P=0.779) by the exposure durations (12, 24 and 36 h) used in this study. Alternatively, the lysosomal membrane stability in abalone exposed to higher air temperatures of 16 or 23°C recovered at a faster rate when subjected to shorter durations of air exposure (F_{2, 66}=3.663, P=0.031 and F_{1, 44}=17.057, P<0.001 for 16 and 23°C respectively).     

皱纹盘鲍南北方群体的高温应激和生长差异

为研究皱纹盘鲍(Haliotis discus hannai Ino)经过杂交和南方养殖后,南方群体(杂交群体)是否与北方群体(自交群体)在适温性上是否产生了差异,从而是否更加适应南方高温环境,本研究开展了皱纹盘鲍南北方群体的高温应激和南方地区养殖实验。高温应激实验中:经过30℃应激后,南方群体恢复期所有取样组织中HSP70在0 h的表达量都显著高于北方群体(P0.05),HSP90在外套膜和肝胰脏中的表达量也高于北方群体(鳃中的表达量略低但差异不显著);经过33℃应激后,南方群体HSP70和HSP90在足、外套膜和鳃0 h表达量都显著高于北方群体(P0.05)。养殖实验中:从12月开始至翌年2月水温不超过17.11℃,为北方群体的快速生长期,生长快于南方群体;从3月开始,水温逐渐超过20℃,北方群体生长慢于南方群体,同时北方群体开始出现死亡现象,7月北方群体大量死亡,存活数量不足30粒。综合HSP70、HSP90的高温应激表达和养殖实验结果,可以得出:皱纹盘鲍经过杂交和南方累代养殖后,适温上限有所提高,已与北方群体产生较大差异,可适应较高的水温;30℃水温刺激下南北方群体的HSP70的相对表达量与对高温的耐受性具有正相关性,可以在鲍的抗高温选育种中进行辅助筛选。     

Growth and feeding in juvenile triploid and diploid blacklip abalone, Haliotis rubra (Leach, 1814), at two temperatures

Growth and feeding of juvenile triploid and diploid blacklip abalone Haliotis rubra (Leach, 1814) were investigated at two temperatures of 17 and 21 °C over a 50‐day period. There were no differences in growth between triploid and diploid abalone as measured by shell length and body weight. Both triploid and diploid abalone increased in length but not in weight at 21 °C. Condition indices were similar for triploid abalone maintained at both temperatures; however, those for diploid abalone were significantly higher at 17 °C than at 21 °C. Food intake was significantly greater yet feed conversion efficiency was significantly lower in triploid than in diploid abalone. Both the feeding variables were independent of temperature. On average, diploid abalone were able to convert 1 g of dry food ingested to 0.58 g of body weight, but triploid abalone only 0.44 g.     

The physiological tolerance of the grey carpet shark (<Emphasis Type="Italic">Chiloscyllium punctatum</Emphasis>) and the epaulette shark (<Emphasis Type="Italic">Hemiscyllium ocellatum</Emphasis>) to anoxic exposure at three seasonal temperatures

The epaulette shark (Hemiscyllium ocellatum) and the grey carpet shark (Chiloscyllium punctatum) are commonly found in periodically hypoxic environments. The ecophysiological time available for these animals to safely exploit these niches during different seasonal temperatures was examined. The time to loss of righting reflex (T _LRR) was examined in response to an open ended anoxic challenge at three seasonal temperatures (23, 25 and 27°C). Ventilation rates were measured in an open ended anoxic challenge at 23°C and during 1.5 h of anoxia followed by 2 h of re-oxygenation at 23 and 25°C. The mean T _LRR of epaulette and grey carpet sharks was inversely proportional to temperature. The T _LRR was similar between species at 23°C; however, grey carpet sharks had significantly reduced T _LRR at higher temperatures. During the standardised anoxic challenge, epaulette sharks entered into ventilatory depression significantly earlier at 25°C. During re-oxygenation, epaulette sharks exposed to anoxia at 23°C had no significant increase in ventilation rates. However, after anoxic challenge and re-oxygenation at 25°C, epaulette sharks showed a significant increase in ventilation rates during re-oxygenation. Grey carpet sharks displayed no evidence of ventilatory depression during anoxia. However, during re-oxygenation, grey carpet sharks had significantly elevated ventilation rates above pre-experimental levels and control animals. These data demonstrate that the anoxia tolerance times of both species were temperature dependent, with a significant reduction in the T _LRR occurring at higher temperatures. Epaulette sharks had a significantly greater T _LRR at higher temperatures than grey carpet sharks, which did not enter into a ventilatory depression.     

Effect of thermal stress on Hsp70 gene expression and female reproductive performance of giant freshwater prawn,Macrobrachium rosenbergii

Using Hsp70 as a biomarker, thermal stress impinges on reproductive organs, ovary and hepatopancreas were being analyzed by determining the expression of Hsp70 mRNA inside the organs after the adult inter‐molt females were subjected to thermal treatment at 35, 30 and 28°C (Control). Results showed the expression of Hsp70 mRNA under thermal treatment of 35°C after 2 hr recovery in ovary were upregulated at 2, 4, 6, 12, 24 hr and 30 days compared to control whereas in hepatopancreas under similar treatment, the expression of Hsp70 mRNA were significantly higher than control at 6, 24 hr and 30 days. Frequency of reproductive molt at 35°C showed the ovary of females were failed to develop and only entered common molt along three consecutive molt cycles. For 30°C thermal treatment, the expression of Hsp70 mRNA was significantly higher than control after 2 hr recovery but returned to normal afterwards until 30 days’ thermal treatment. Maternal heat shock for 2 hr at 35°C were found to give significantly lower frequency of reproductive molt and longer duration of ovarian development and incubation period whereas maternal heat shock for 2 hr at 30°C gave lower frequency of reproductive molt, slower development of embryo and lower hatching success compared to untreated control. This study suggests that short and long‐term thermal stress at 30 and 35°C were found to affect the induction of Hsp70 mRNA in reproductive organs of Macrobrachium rosenbergii and also influence their reproductive performance.     

Effects of temperature and dietary protein on gene expression of Hsp70 and Wap65 and immunity of juvenile mirror carp (Cyprinus carpio)

Juvenile mirror carp were fed diets containing 303.4, 321.7, 341.2, 361.0 and 379.1 g kg^?1 proteins, respectively, and reared at different water temperatures (18, 23 and 28°C) for 60 days. Gene expression of heat shock protein gene (Hsp70) and the warm temperature acclimation‐related 65 kDa protein gene (Wap65), immunity and antioxidant status in the carp were investigated. Results indicated that the contents of serum complement 3 (C3), complement 4 (C4) and immunoglobulin M (IgM), as well as activities of liver superoxide dismutase (SOD) and lysozyme (LSZ) were significantly enhanced with increasing dietary protein (P < 0.05), while content of malondiadehyde (MDA) decreased. Gene expression level of Wap65 in the liver significantly increased with dietary protein, while gene expression of Hsp70 decreased. The contents of C3, C4 and IgM, the activities of SOD and LSZ and gene expression level of Wap65 in the liver significantly increased with temperature. These results suggest that: Serum immune parameter, antioxidant enzymes and Hsp70 and Wap65 expression interact in fish to improve ability to adapt to the environment; and the optimal conditions for the immunity of carp are 348.1?354.5 g kg^?1 protein at 18°C, 352.3?364.9 g kg^?1 at 23°C and 360.2?364.3 g kg^?1 at 28°C, and the optimum temperature for carp is 23°C.     

Effects of heat-shock selection during pelagic stages on thermal sensitivity of juvenile sea cucumber, <Emphasis Type="Italic">Apostichopus japonicus</Emphasis> Selenka

The effects of heat-shock during pelagic stages on growth and survival of juvenile sea cucumber Apostichopus japonicus were investigated to test the possibility to acquire high thermal tolerance individuals after the heat-shock selection. Larvae at the stages of blastula, gastrula, and auricularia were heat-shocked at selected temperatures (21.5, control; 26, 28, and 30°C) for 45 min and returned to 21.5°C for continuous rearing. There was a significant difference in thermal sensitivity among different developmental stages, and thermal tolerance of the larvae was correlated with the expression of heat shock protein 70 (Hsp70). Juveniles after the heat-shock selection at pelagic stages showed higher induced thermotolerance than those without heat-shock. Therefore, heat-shock application at early pelagic development stages is potentially a useful way to select high-thermotolerance variety of the sea cucumbers.