Abstract
Marine pelagic species are being increasingly challenged by environmental change. Their ability to persist will depend on their capacity for physiological acclimatization. Little is known about limits of physiological plasticity in key species at the base of the food web. Here we investigate the capacity for acclimatization in the copepod Neocalanus flemingeri, which inhabits the Gulf of Alaska, a heterogeneous and highly seasonal environment. RNA-Seq analysis of field-collected pre-adults identified large regional differences in expression of genes involved in metabolic and developmental processes and response to stressors. We found that lipid synthesis genes were up-regulated in individuals from Prince William Sound and down-regulated in the Gulf of Alaska. Up-regulation of lipid catabolic genes in offshore individuals suggests they are experiencing nutritional deficits. The expression differences demonstrate physiological plasticity in response to a steep gradient in food availability. Our transcriptional analysis reveals mechanisms of acclimatization that likely contribute to the observed resilience of this population.
Highlights
University of Alaska, Fairbanks, 120 O’Neill, Fairbanks, AK 99775-7220, USA
While the results indicate a large capacity for physiological acclimatization in N. flemingeri, they suggest that offshore individuals in the high-nutrient low-chlorophyll (HNLC) region of the Gulf of Alaska were experiencing nutritional stress, interfering with lipid accumulation required for successful preparation for diapause
Neocalanus flemingeri were collected in early May, when most individuals are in the pre-adult developmental stage and preparing for diapause, which requires the accumulation of storage lipids (Fig. 1a)[26]
Summary
University of Alaska, Fairbanks, 120 O’Neill, Fairbanks, AK 99775-7220, USA. Correspondence and requests for materials should be addressed to. Relative gene expression in combination with a functional analysis of the regulated genes can inform how an organism is responding to its ambient environment We used this approach to examine the transcriptional physiology of a marine zooplankter, the copepod Neocalanus flemingeri, a high-latitude species with a complex life history adapted to optimize synchronization with a seasonally changing environment that is spatially heterogeneous. Differences in the physical and chemical environment lead to resource gradients across the shelf, which impact the community composition and abundances of phytoplankton, microzooplankton, and mesozooplankton[18,19,24] In this highly variable environment, N. flemingeri is a biomass dominant in April–May throughout the region from Prince William Sound to the outer shelf of the Gulf of Alaska[25]. While the results indicate a large capacity for physiological acclimatization in N. flemingeri, they suggest that offshore individuals in the high-nutrient low-chlorophyll (HNLC) region of the Gulf of Alaska were experiencing nutritional stress, interfering with lipid accumulation required for successful preparation for diapause
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