Biology subjects

Aasjord, A. E.

Publications and source records attributed to Aasjord, A. E..

3 recordsLinked to original sources

bioRxiv2025

Behavioral ontogeny in a pelagic tunicate reveals the deep origins of chordate behavioral developmental plasticity.

Behavioral developmental plasticity refers to the lasting changes in an organisms behavior that occur during development in response to external and internal cues, enhancing survival and reproduction. While well studied in vertebrates, its occurrence in other chordates, including tunicates, the closest relatives of vertebrates, remains unclear. We built a behavioral atlas of the planktonic tunicate Oikopleura dioica across its life cyclefrom larval to adult stages using high-throughput tracking and unsupervised analysis. Swimming kinematics, exploration, and thigmotaxis increased with development. Adults exhibit a unique innovation, known as the house, a complex extracellular filtration structure encasing the animal trunk, which drastically alters locomotion and exploration compared to free-swimming individuals. Postural variation during ontogeny is captured by seven basic shapes ("eigenoikopleuras"), with complex shapes becoming more frequent over time. Spatiotemporal embedding and Hidden Markov modeling revealed that behavioral refinement arises from changes in motor modules and their transitions. House occupancy similarly shifts these modules, indicating context-specific specialization. This continuous behavioral maturation parallels Oikopleuras neotenic morphology, retaining a larval body plan unlike other tunicates. Our atlas provides a quantitative framework for exploring the evolution of behavioral developmental plasticity in chordates.

animal behavior and cognition↗

bioRxiv2024

Prochlorococcus predation by a globally abundant filter feeder

Prochlorococcus is the most abundant photosynthetic cell on Earth and is critical to primary productivity and biogeochemical cycles of the open ocean. Appendicularians are ubiquitous gelatinous filter-feeding zooplankton that feed on marine microorganisms including Prochlorococcus. However, the details of this feeding interaction are extremely understudied relative to its potential importance in top-down controls on Prochlorococcus. This is the first study to experimentally examine several dimensions of the feeding interaction between cultivated appendicularians and Prochlorococcus. We found that Prochlorococcus retention rates by the appendicularian Oikopleura dioica increased with prey concentration and predator age. We found that appendicularians grazed equally on the two most globally abundant Prochlorococcus ecotypes HLI and HLII and that the presence of larger diatom prey did not change Prochlorococcus retention rates. The quantitative insight and retention rates provided by this study will help fill gaps in models of the marine carbon cycle and marine microbial community dynamics and biogeography, and expand the knowledge of Prochlorococcus ecology. ImportanceAppendicularians are a known predator of picocyanobacteria, but the details of their feeding on the globally abundant picocyanobacterium Prochlorococcus have not been investigated. We quantified Prochlorococcus retention rates over a range of ecologically relevant conditions, which will inform microbial community predictions and carbon flux models and lead to improved understanding of carbon transfer in the ocean, microbial ecology, and microbial communities.

ecology↗

bioRxiv2022

Laboratory study of Fritillaria lifecycle reveals larvacean commonalities and key morphogenetic events leading to taxon-specific anatomy

A fascinating variety of adult body plans can be found in the Tunicates, the closest existing relatives of vertebrates. A distinctive feature of the larvacean class of pelagic tunicates is the presence of a highly specialized surface epithelium that produces a cellulose test, the "larvacean house". While substantial differences exist between the anatomy of larvacean families, most of the ontogeny is derived from the observations of a single genus, Oikopleura. We present the first study of Fritillaria development based on the observation of individuals reproduced in the laboratory. Like the other small epipelagic species Oikopleura dioica, the larvae of Fritillaria borealis grow rapidly in the laboratory, and they acquire the adult form within a day. We could show that major morphological differences exhibited by Fritillaria and Oikopleura adults originate from a key developmental stage during larval organogenesis. Here, the surface epithelium progressively retracts from the posterior digestive organs of Fritillaria larvae, and it establishes house-producing territories around the pharynx. Our results show that the divergence between larvacean genera was associated with a profound rearrangement of the mechanisms controlling the differentiation of the larval ectoderm.

zoology↗