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
How individual organisms adapt to nonoptimal conditions through physiological acclimatization is central to predicting the consequences of unusual abiotic and biotic conditions such as those produced by marine heat waves. The Northeast Pacific, including the Gulf of Alaska, experienced an extreme warming event (2014–2016, “The Blob”) that affected all trophic levels and led to large‐scale changes in the community. The marine copepod
- NSF-PAR ID:
- 10445825
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Molecular Ecology
- Volume:
- 31
- Issue:
- 6
- ISSN:
- 0962-1083
- Page Range / eLocation ID:
- p. 1753-1765
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract 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. -
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In high-latitude environments where seasonal changes include periods of harsh conditions, many arthropods enter diapause, a period of dormancy that is hormonally regulated. Diapause is characterized by very low metabolism, resistance to environmental stress, and developmental arrest. It allows an organism to optimize the timing of reproduction by synchronizing offspring growth and development with periods of high food availability. In species that enter dormancy as pre-adults or adults, termination of diapause is marked by the resumption of physiological processes, an increase in metabolic rates and once transitioned into adulthood for females, the initiation of oogenesis. In many cases, individuals start feeding again and newly acquired resources become available to fuel egg production. However, in the subarctic capital-breeding copepod Neocalanus flemingeri, feeding is decoupled from oogenesis. Thus, optimizing reproduction limited by fixed resources such that all eggs are of high quality and fully-provisioned, requires regulation of the number of oocytes. However, it is unknown if and how this copepod limits oocyte formation. In this study, the phase in oocyte production by post-diapause females that involved DNA replication in the ovary and oviducts was examined using incubation in 5-Ethynyl-2′-deoxyuridine (EdU). Both oogonia and oocytes incorporated EdU, with the number of EdU-labeled cells peaking at 72 hours following diapause termination. Cell labeling with EdU remained high for two weeks, decreasing thereafter with no labeling detected by four weeks post diapause, and three to four weeks before spawning of the first clutch of eggs. The results suggest that oogenesis is sequential in N. flemingeri with formation of new oocytes starting within 24 hours of diapause termination and limited to the first few weeks. Lipid consumption during diapause was minimal and relatively modest initially. This early phase in the reproductive program precedes mid-oogenesis and vitellogenesis 2, when oocytes increase in size and accumulate yolk and lipid reserves. By limiting DNA replication to the initial phase, the females effectively separate oocyte production from oocyte provisioning. A sequential oogenesis is unlike the income-breeder strategy of most copepods in which oocytes at all stages of maturation are found concurrently in the reproductive structures.more » « less
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