Extreme temperatures reduce copepod performance, but increase in the gut
thermophilic Proteobacteria
Abstract
Copepods are one of the most abundant invertebrate groups in the seas
and oceans and are a significant food source for marine animals.
However, copepods are also particularly vulnerable to elevated
temperatures, yet it is unknown the role of the gut microbiome in
shaping copepod susceptibility to warming. We addressed this fundamental
knowledge gap by assessing key life history traits (survival,
development, reproduction), and changes in the relative abundance of the
gut microbiome in the tropical calanoid copepod Acartia sp. in response
to warming (26, 30, and 34°C). Gut microbiomes of copepods were analyzed
using high throughput DNA sequencing of V1–V9 of 16S rRNA hypervariable
regions. Copepod performance was better at 30°C than at 26°C as
indicated by higher survival, faster growth rate and development, and
higher fecundity. However, all of these parameter strongly decreased
when temperature increased to 34°C. We recorded 1,262,987 amplicon
sequence reads, corresponding to 392 total operational taxonomic units
at 97% similarity. The gut content of all copepods contained
Cyanobacteria, Proteobacteria, Bacteroidetes, Planctomycetes,
Actinobacteria, and Acidobacteria. Thermophilic Proteobacteria were
found dominantly at high temperatures (30°C and 34°C). At 34°C, Vibrio
was the only dominant group, accounting for 70% of species found in
copepod guts, which may partly associated with the reduced growth and
survival of Acartia sp.. The next logical step is to explore the
functional role of all gut bacterial groups in relation to changes in
copepod fitness, which will fundamentally advance our mechanistic
understanding of the adaptability of tropical copepods and, more
generally, marine invertebrates to the warming climate.