The polychaete Boccardia wellingtonensis is a poecilogonous species that produces different larval types. Females may lay Type I capsules, in which only planktotrophic larvae are present, or Type III capsules that contain planktotrophic and adelphophagic larvae as well as nurse eggs. While planktotrophic larvae do not feed during encapsulation, adelphophagic larvae develop by feeding on nurse eggs and on other larvae inside the capsules and hatch at the juvenile stage. Previous works have not found differences in the morphology between the two larval types; thus, the factors explaining contrasting feeding abilities in larvae of this species are still unknown. In this paper, we use a transcriptomic approach to study the cellular and genetic mechanisms underlying the different larval trophic modes of B. wellingtonensis. By using approximately 624 million high-quality reads, we assemble the de novo transcriptome with 133,314 contigs, coding 32,390 putative proteins. We identify 5221 genes that are up-regulated in larval stages compared to their expression in adult individuals. The genetic expression profile differed between larval trophic modes, with genes involved in lipid metabolism and chaetogenesis over expressed in planktotrophic larvae. In contrast, up-regulated genes in adelphophagic larvae were associated with DNA replication and mRNA synthesis.

Snow algae represent important primary producers and carbon sinks in the cryosphere. Disentangling the physiological and molecular responses that these organisms display in the face of acute abiotic stress caused by snow dynamics is key to revealing survival strategies and monitoring climate change effects. Here, we examine the tolerance to a short-term (4 h) freezing condition (-20°C) in darkness, followed by a recovery period, in the Antarctic snow alga Chlorominima collina. The responses were analyzed in contrast to a light control (2 °C) by integrating of chlorophyll fluorescence of PSII, mRNA-sequencing and oxidative stress detection. The treated cells reduce PSII photochemical efficiency and suppress the light harvesting process. Simultaneously abiotic stress-responsive genes were expressed, suggested a reprograming of metabolism and process, orchestrated by key signaling pathways and transcription factors. This profile revealed common elements of states prior to hypometabolism such as, the fuel switch from carbohydrate to lipid catabolism, improved defenses, repression of biosynthetic processes, induction of mitophagy and autophagy, and regulation of transcription and translation. These adjustments promoted the maintenance of cellular homeostasis, as evidenced by enrichment of this process and the recovery of PSII efficiency. Therefore, we proposed that the integration of the reduction of efficiency with which PSII captures energy and the regulation of genes involved in the induction of hypometabolism constitutes an adaptive strategy that confers at snow algae freezing and darkness tolerance. Collectively, the observed functional changes may be relevant for understanding the survival and subsequent adaptation of Chlorophyta to the Antarctic snow environment.

Environmental filtering studies have revealed immense oceanic microbial diversity, yet the Southeast Pacific remains comparatively undersampled. We characterize the molecular diversity of phytoplankton across two biogeographic domains with contrasting oceanography—fjords and channels (41–53° S) versus the open Pacific (36–42° S)—where the frequency and intensity of harmful algal blooms (HABs) have increased. Using SSU rRNA metabarcoding, we retrieved community composition and biogeographic patterns for micro-phytoplankton. Diversity signals indicated broadly overlapping communities between domains with subtle shifts along hydrographic and nutrient gradients rather than sharp breaks. Phylogenetic resolution within bloom-forming genera recovered well-supported clades, and multiple ASVs matched historically relevant HAB taxa, including representatives of the Alexandrium complex, Dinophysis, Pseudo-nitzschia, and Karenia. Together, these results suggest that regional environmental filtering acts modestly at the community level while preserving clear signals of taxa of management concern. By providing a regionally resolved, DNA-based baseline for southern Chile’s fjords and adjacent open coast, this study helps fill the molecular diversity gap for the Southeast Pacific and supports improved HAB surveillance and ecosystem forecasting in a climate-sensitive seascape.