Divergent temperature-specific metabolic and feeding rates of native and invasive crayfish

Effects of acute low-temperature stress on respiratory metabolism, antioxidants, and metabolomics of red swamp crayfish, Procambarus clarkii

Crayfish (Procambarus clarkii) aquaculture is threatened by abrupt temperature decreases caused by climatic phenomena, such as cold waves and seasonal fluctuations. In this study, crayfish were exposed to an abrupt temperature change from 17 °C to 7 °C for 24 h to investigate the effects of acute low-temperatures on respiratory metabolism, antioxidants, and metabolomics. The results showed that acute low-temperatures significantly reduced the activities of pyruvate kinase, lactate dehydrogenase, and succinate dehydrogenase in the gills and hemolymph, associated with decreases in anaerobic and aerobic respiratory capacities, and significant decreases in oxygen consumption, ammonia excretion, and maximum metabolic rates. Antioxidant enzymes in the hepatopancreas and hemolymph initially increased then decreased within 24 h. Metabolomics revealed that glycerophospholipid metabolism and glycosylphosphatidylinositol anchor biosynthesis pathways responded to acute low-temperatures, with glycerophospholipids being the most significantly differentially expressed metabolites. These results supported the hypothesis that crayfish exhibit lower metabolic activity at low temperatures. Our data provide mechanistic insight into the biological changes induced by acute low-temperature and may provide insight into culture of P. clarkii in cold waters.

Acclimation, thermal tolerance and aerobic metabolism of narrow-clawed crayfish, Pontastacus leptodactylus (Eschscholtz, 1823)

Ectotherms are considered more susceptible to global warming. Variations in ambient temperature are especially alarming as the majority of animals are ectothermic, with temperature seen as a crucial determinant of their ecology, biogeography, behaviour, and physiology. Ectotherms, which depend on external ambient temperatures to regulate their body temperature, exhibit various physiological and metabolic responses to variations in temperature. These responses are essential for comprehending how these species will acclimatise to changing water temperatures and the consequent alterations in oxygen availability. This study assessed the acclimation ability, temperature tolerance, and metabolic rate of narrow-clawed crayfish (Pontastacus leptodactylus) to elucidate the crayfish's responses to potential climate change. Our study showed that the narrowed clawed crayfish is a species that exhibits high thermal tolerance, with an extensive dynamic (1114 °C2), static thermal polygon area (966 °C2), resistance zone of 103 °C2 and the ability to withstand extreme temperatures (CTmin-CTmax: 1.60-36.8 °C). The acclimation temperature has minimal impact on the thermal tolerance of the crayfish (P < 0.01). The optimal temperature range for SMR of Pontastacus leptodactylus is 20-25 °C, within which a decline in standard metabolic rate (SMR) occurs as temperature rises.

PHARMACOKINETICS OF CEFTAZIDIME IN SIGNAL CRAYFISH (PACIFASTACUS LENIUSCULUS) FOLLOWING A SINGLE DOSE

Crustaceans are housed in zoos and aquariums and have also gained importance in the private sector and food industry. Shell lesions are common and often attributed to bacterial infections. However, few controlled studies have been performed evaluating antibiotics in crustaceans. This study assessed the pharmacokinetics of a single dose of ceftazidime (22 mg/kg) given by IM or IV injection in wild-caught signal crayfish (Pacifastacus leniusculus). Pharmacokinetic parameters were calculated by noncompartmental analysis of sparse data. Maximum ceftazidime hemolymph concentration following IM administration was 124.6 ± 14.7 µg/mL and Tmax was 5 min, with 80% bioavailability. Following IV administration, the extrapolated maximum concentration of ceftazidime, (C [0]), was 581.4 µg/mL. Ceftazidime was last detected at 72 hr and 120 hr post IM and IV administration, respectively. Terminal half-life was 8.03 hr and 10.3 hr after IM and IV administration, respectively. Results suggest that both routes have the capacity to reach a maximum hemolymph concentration quickly in signal crayfish. Moreover, ceftazidime was maintained above a concentration of 4 µg/mL, a published minimal inhibitory concentration for Vibrio spp., for 24 hr for both IM and IV routes. Therefore, ceftazidime may be useful for infections with susceptible Vibrio spp. in signal crayfish.

Interactive effects of intrinsic and extrinsic factors on metabolic rate

Metabolism energizes all biological processes, and its tempo may importantly influence the ecological success and evolutionary fitness of organisms. Therefore, understanding the broad variation in metabolic rate that exists across the living world is a fundamental challenge in biology. To further the development of a more reliable and holistic picture of the causes of this variation, we review several examples of how various intrinsic (biological) and extrinsic (environmental) factors (including body size, cell size, activity level, temperature, predation and other diverse genetic, cellular, morphological, physiological, behavioural and ecological influences) can interactively affect metabolic rate in synergistic or antagonistic ways. Most of the interactive effects that have been documented involve body size, temperature or both, but future research may reveal additional 'hub factors'. Our review highlights the complex, intimate inter-relationships between physiology and ecology, knowledge of which can shed light on various problems in both disciplines, including variation in physiological adaptations, life histories, ecological niches and various organism-environment interactions in ecosystems. We also discuss theoretical and practical implications of interactive effects on metabolic rate and provide suggestions for future research, including holistic system analyses at various hierarchical levels of organization that focus on interactive proximate (functional) and ultimate (evolutionary) causal networks. This article is part of the theme issue 'The evolutionary significance of variation in metabolic rates'.

Long-term trends in crayfish invasions across European rivers

Europe has experienced a substantial increase in non-indigenous crayfish species (NICS) since the mid-20th century due to their extensive use in fisheries, aquaculture and, more recently, pet trade. Despite relatively long invasion histories of some NICS and negative impacts on biodiversity and ecosystem functioning, large spatio-temporal analyses of their occurrences are lacking. Here, we used a large freshwater macroinvertebrate database to evaluate what information on NICS can be obtained from widely applied biomonitoring approaches and how usable such data is for descriptions of trends in identified NICS species. We found 160 time-series containing NICS between 1983 and 2019, to infer temporal patterns and environmental drivers of species and region-specific trends. Using a combination of meta-regression and generalized linear models, we found no significant temporal trend for the abundance of any species (Procambarus clarkii, Pacifastacus leniusculus or Faxonius limosus) at the European scale, but identified species-specific predictors of abundances. While analysis of the spatial range expansion of NICS was positive (i.e. increasing spread) in England and negative (significant retreat) in northern Spain, no trend was detected in Hungary and the Dutch-German-Luxembourg region. The average invasion velocity varied among countries, ranging from 30 km/year in England to 90 km/year in Hungary. The average invasion velocity gradually decreased over time in the long term, with declines being fastest in the Dutch-German-Luxembourg region, and much slower in England. Considering that NICS pose a substantial threat to aquatic biodiversity across Europe, our study highlights the utility and importance of collecting high resolution (i.e. annual) biomonitoring data using a sampling protocol that is able to estimate crayfish abundance, enabling a more profound understanding of NICS impacts on biodiversity.