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ABSTRACT Temperature is one of the main factors influencing biological processes of ectothermic species. An optimum temperature of 16-18[degrees]C has been suggested for the development of early life stages of [...]

ABSTRACT On Australian aquaculture farms, early life stages of abalone are reared under controlled abiotic and biotic conditions in an attempt to optimize individual growth and reduce potential stressors. Yet, [...]

During development crustaceans experience a range of oxygen tensions (PO.sub.2) in their various developmental environments. Therefore, it is likely that they developed varying strategies to respond to hypoxic events during their ontogeny. We investigated short-term responses to various oxygen levels in early life stages of two anomuran decapods Petrolisthes laevigatus and Lithodes santolla that develop in different habitats. Embryos and juveniles of P. laevigatus inhabit the upper rocky intertidal and are regularly exposed to hypoxia during low tide, while larvae of this species inhabit well-oxygenated surface waters. L. santolla is a subtidal species that inhabits fjords and is frequently exposed to hypoxia due to stratification in this environment. Oxygen consumption (MO.sub.2), lactate content, RNA/DNA ratio, lactate dehydrogenase and superoxide dismutase (SOD) activities were measured in embryos, larvae and juveniles after exposure to PO.sub.2s of 3-21 kPa for 24 h. Results indicated considerable variation in hypoxia tolerances among the ontogenetic stages of both species. Embryos of both species relied on anaerobiosis at all tested PO.sub.2 yet were able to regulate MO.sub.2 until 15 kPa. In contrast, larvae of L. santolla were oxyconformers, while those of P. laevigatus continued to oxyregulate in conjunction with a decrease in SOD activities in response to low PO.sub.2. Juveniles of P. laevigatus were more sensitive to hypoxia than those of L. santolla as all tested parameters were affected at higher PO.sub.2 in the former. This study shows that aerobic and anaerobic metabolism, antioxidant defence and protein synthesis of early life stages are diverse and reflect the variety of inhabited environments., Author(s): Katharina Alter[sup.1] [sup.5] , Kurt Paschke[sup.2] , Paulina Gebauer[sup.3] , Juan-Pablo Cumillaf[sup.2] , Hans-Otto Portner[sup.4] Author Affiliations: (1) Universität Bremen, Bremen, Germany (2) Instituto de Acuicultura, Universidad Austral de [...]

Many abalone farms are reliant on coastal water inputs which are subject to fluctuations in environmental variables such as temperature, oxygen, CO2 and salinity. Near future climate change scenarios predict that there will be more frequent extreme weather events which can exacerbate these fluctuations and potentially be deleterious to farmed abalone where these variables remain largely uncontrolled. In this review, we have taken an in depth examination of current literature on the effects of environmental stress on abalone physiology and metabolism and how this affects their health and growth. In conjunction, we have also reviewed the effects of farm-specific stressors such as ammonia, stocking density, handling, nutrition and disease and the synergistic effects of these and environmental stressors on abalone physiology. We have identified currents gaps in our knowledge of this under-studied species and have made predictions on the effects of climate change on future abalone production with suggestions for future research. In summary, it is expected that abalone will show reduced growth rates as more energy is invested in combating stresses rather than growth. Furthermore, disease outbreaks may become more frequent with greater fluctuations in temperature and salinity, both of which have large-scale effects on immunity. The current body of knowledge is mainly on whole animal effects of stresses, but we know very little of their mechanistic foundation. Research in this area as well as investments in infrastructure will be pivotal in identifying and implementing strategic interventions to maintain a sustainable abalone industry in Australia. [ABSTRACT FROM AUTHOR]

We evaluated the effects of projected, near future ocean acidification (OA) and extreme events of temperature (warming or cooling) on the thermal tolerance of Concholepas concholepas, a coastal benthic keystone species. Three separate trials of an experiment were conducted by exposing juvenile C. concholepas for 1 month to one of two contrasting pCO 2 levels (~500 and ~1200 μatm). In addition, each pCO 2 level was combined with one of four temperature treatments. The control was 15 °C, whilst the other temperatures were 10 °C (Trial 1), 20 °C (Trial 2) and 25 °C (Trial 3). At the end of each trial, we assessed Critical Thermal maximum (CTmax) and minimum (CTmin) via self-righting success, calculated partial thermal tolerance polygons, measured somatic growth, determined transcription of Heat Shock Proteins 70 (HSP70) and measured oxygen consumption rates. Regardless of pCO 2 level, HSP70 transcript levels were significantly higher in juveniles after exposure to extreme temperatures (10 °C and 25 °C) indicating physiological stress. Oxygen consumption rates increased with increasing temperature from 10 °C to 20 °C though showed a decrease at 25 °C. This rate was not affected by pCO 2 or the interaction between temperature and pCO 2 . Juveniles exposed to present-day and near future pCO 2 levels at 20 °C showed similar thermal tolerance polygonal areas; whilst changes in both CTmin and CTmax at 25 °C and 10 °C caused narrower and broader areas, respectively. Temperature affected growth, oxygen consumption and HSP70 transcription in small juvenile C. concholepas. Exposure to elevated pCO 2 did not affect thermal tolerance, growth or oxygen consumption at temperatures within the thermal range normally experienced by this species in northern Chile (15-20 °C). At elevated pCO 2 conditions, however, exposure to warmer (25 °C) or colder (10 °C) temperatures reduced or increased the thermal area, respectively. This study demonstrates the importance of examining the thermal-tolerance edges to better understand how OA and temperature will combine to physiologically challenge inter-tidal organisms., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier B.V.)