Into the bloom: Molecular response of pelagic tunicates to fluctuating food availability

Abstract

The planktonic tunicates appendicularians and thaliaceans are highly efficient filter feeders on a wide range of prey size including bacteria and have shorter generation times than any other marine grazers. These traits allow some tunicate species to reach high population densities and ensure their success in a favourable environment. However, there are still few studies focusing on which genes and gene pathways are associated with responses of pelagic tunicates to environmental variability.Herein, we present the effect of food availability increase on tunicate community and gene expression at the Marquesas Islands (South-East Pacific Ocean). By using data from the Tara Oceans expedition, we show that changes in phytoplankton density and composition trigger the success of a dominant larvacean species (an undescribed appendicularian). Transcriptional signature to the autotroph bloom suggests key functions in specific physiological processes, i.e., energy metabolism, muscle contraction, membrane trafficking, and proteostasis. The relative abundance of reverse transcription-related Pfams was lower at bloom conditions, suggesting a link with adaptive genetic diversity in tunicates in natural ecosystems. Downstream of the bloom, pelagic tunicates were outcompeted by copepods. Our work represents the first metaomics study of the biological effects of phytoplankton bloom on a key zooplankton taxon.

Integrative omics identification, evolutionary and structural analysis of low affinity nitrate transporters in diatoms, diNPFs

“…Conversely, the comparison of diNPF mRNA occurrences (figure 2 c ) shows more similarity between different size classes and depth than diNPF DNA. This is of note, since low-DNA-high-mRNA (and vice versa) levels in a given sampling station are the only proper way to infer patterns of overexpression (and downregulation) of genes in the TARA Oceans dataset [61,62]. As an example, the high-DNA-high-mRNA level detected in the South Polar sampling stations (fraction 5–20 µM, SUR, and fraction 20–180 µM, DCM and SUR) is representative of basal expression of diNPFs, while low-DNA-high-mRNA level (South Pole, fraction 5–20 µM, DCM) is likely representative of few, highly expressed diNPFs.…”

Metabarcoding Analyses and Seasonality of the Zooplankton Community at BATS

“…The clearest example was the shift from the deep-mixing and spring bloom communities to the late spring community. This was typified by a shift from an early spring bloom community, dominated by of omnivorous/carnivorous (Pleuromamma sp., euphausiids), and appendicularians, small filter feeders able to feed in even very small phytoplankton and respond rapidly to increased resources due to their short life cycle (Acuña et al, 1995;Fernández and Acuña, 2003;Blanco-Bercial et al, 2006;Lobón et al, 2013), to a Calanidae and Eucalanoidea dominated one, specialized in feeding in larger phytoplankton, during the late bloom period.…”

Environmental DNA captures diurnal fluctuations of surface eukaryotes on a tropical coral reef

“…In a few samples, reads assigned to tunicata, predominantly from the class Appendicularia, accounted for large proportions of the total reads, and over 60% of reads at 1 a.m. on 29th of April at the Southwest site. Appendicularia, more commonly referred to as larvaceans, are free‐swimming, gelatinous members of the zooplankton community that can bloom in response to changes in phytoplankton abundance and composition (Sordino et al., 2019). The spikes in read abundance seen here are most likely due to the capture of whole organisms and the discharge of mucus for their temporary secreted houses (Galt & Sykes, 1983; Robison et al., 2005).…”