De novo transcriptome assembly of the Southern Ocean copepod Rhincalanus gigas sheds light on developmental changes in gene expression

Cory A Berger,Deborah K Steinberg,Nancy J Copley,Ann M Tarrant

doi:10.1016/j.margen.2021.100835

Cory A Berger, Deborah K Steinberg + Show 2 more

Open Access

https://doi.org/10.1016/j.margen.2021.100835

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Abstract

Copepods are small crustaceans that dominate most zooplankton communities in terms of both abundance and biomass. In the polar oceans, a subset of large lipid-storing copepods occupy central positions in the food web because of their important role in linking phytoplankton and microzooplankton with higher trophic levels. In this paper, we generated a high-quality de novo transcriptome for Rhincalanus gigas, the largest-and among the most abundant-of the Southern Ocean copepods. We then conducted transcriptional profiling to characterize the developmental transition between late-stage juveniles and adult females. We found that juvenile R. gigas substantially upregulate lipid synthesis and glycolysis pathways relative to females, as part of a developmental gene expression program that also implicates processes such as muscle growth, chitin formation, and ion transport. This study provides the first transcriptional profile of a developmental transition within Rhincalanus gigas or any endemic Southern Ocean copepod, thereby extending our understanding of copepod molecular physiology.

Highlights

The copepod Rhincalanus gigas (Fig. 1) is one of the dominant members of the mesozooplankton of the Southern Ocean, numerically and in terms of biomass (Ommanney, 1936; Mackey et al, 2012)
We identified 449 gene ontology (GO) categories enriched among genes with higher expression in juveniles (263 biological process (BP), 67 CC, 119 molecular function (MF)), and 70 GO categories enriched among genes with higher expression in females (41 BP, 15 CC, 14 MF)
We present a high-quality transcriptome assembly for Rhincalanus gigas, a large and abundant lipid-storing copepod endemic to the Southern Ocean

Summary

Introduction

The copepod Rhincalanus gigas (Fig. 1) is one of the dominant members of the mesozooplankton of the Southern Ocean, numerically and in terms of biomass (Ommanney, 1936; Mackey et al, 2012). Compared to C. acutus, R. gigas exhibits low winter mortality (Ward et al, 1997) and small seasonal changes in lipid con tent, losing only about half as much relative dry weight and lipids over the winter (Kattner et al, 1994; Hagen and Schnack-Schiel, 1996; Tarling et al, 2007)

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