Biology subjects

Haugen, T.

Publications and source records attributed to Haugen, T..

3 recordsLinked to original sources

bioRxiv2026

No-take zone effectiveness in linear coastal systems depends on spatially heterogeneous placement and larval dispersal directionality

Marine protected areas (MPAs) are widely implemented to protect and/or rebuild exploited populations, yet their population-level effectiveness remains highly variable. Key unresolved knowledge gaps include how the size and the spatial placement of no-take zones interacts with larval dispersal directionality, particularly in linear coastal systems where connectivity is asymmetric. For sedentary species with planktonic larvae, such as European lobster, it is unclear under which dispersal regimes spatial configuration of protection critically determines positive demographic outcomes. Here, we address this gap using a spatially explicit individual-based model parameterized for the European lobster. We ask (i) whether no-take zones consistently enhance abundance and size structure relative to fished areas, and (ii) whether the positioning of no-take and open areas affects spatial protection while holding total protected area constant and (iii) how the alignment between larval dispersal direction and the positioning of no-take areas influences protection outcome. We contrast local, symmetric long-distance, and strongly unidirectional larval dispersal across alternative MPA layouts with equal total protected area but with different spacing. We show that no-take zones reliably increase abundance and the prevalence of large individuals. However, when larval dispersal is strongly unidirectional, population recovery depends on reserve placement: downstream no-take zones benefit from both larval import and local retention, whereas upstream reserves primarily export reproductive output and show limited local recovery. These results indicate that reserve performance cannot be evaluated independently of connectivity structure and identify dispersal directionality as a key determinant of when and where spatial configuration matters for MPA effectiveness in linear coastal systems.

ecology↗

bioRxiv2023

Optogenetics reveals roles for supporting cells in force transmission to and from outer hair cells in the mouse cochlea

Cochlear outer hair cells (OHCs), acting as bidirectional cellular mechanoelectrical-transducers, generate, receive, and exchange forces with other major elements of the cochlear partition, including inner hair cells (IHCs). Force exchange is mediated via a supporting cell scaffold, including Deiters (DC) and outer pillar cells (OPC), to enable the sensitivity and exquisite frequency selectivity of the mammalian cochlea. We conditionally expressed a hyperpolarizing halorhodopsin (HOP), a light-gated inward chloride ion pump in DCs and OPCs. We measured extracellular receptor potentials (ERPs) and their DC component (ERPDC) from the Cortilymph (CL) of HOP expressing mice and compared the responses with similar potentials from littermates without HOP expression. Compound action potentials (CAP) were measured as an indication of IHC activity. HOP laser activation suppressed cochlear amplification through changing timing of its feedback, altered basilar membrane (BM) responses to tones at all measured levels and frequencies, and reduced IHC excitation. Our HOP activation results here complement previous channelrhodopsin activation studies in exploiting optogenetics to measure and understand the roles of DCs and OPCs in vivo in controlling the mechanical and electrical responses of OHCs to sound and their contribution to timed and directed electromechanical feedback to the mammalian cochlea. SIGNIFICANCE STATEMENTOuter hair cells provide electromechanical feedback to the organ of Corti, mediated via a cellular scaffold of Deiters and outer pillar cells, that enables the sensitivity and fine frequency tuning of the cochlea. The role of this scaffold was explored by expressing the halorhodopsin HOP in Deiters and pillar cells which, when illuminated, hyperpolarized them. HOP activation suppressed cochlear amplification through altering the timing of outer hair cell forces to the Organ of Corti, altered basilar membrane responses to tones, including those at levels and frequencies not subject to amplification, and reduced neural excitation. The findings implicated roles for supporting cells in mediating force transmission to and from outer hair cells along all axes of the organ of Corti.

neuroscience↗

bioRxiv2020

Niche preference of Escherichia coli in a peri-urban pond ecosystem

Escherichia coli comprises of diverse strains with a large accessory genome, indicating functional diversity and the ability to adapt to a range of niches. Specific strains would display greatest fitness in niches matching their combination of phenotypic traits. Given this hypothesis, we sought to determine whether E. coli in a peri-urban pond and associated cattle pasture display niche preference. Samples were collected from water, sediment, aquatic plants, water snails associated with the pond as well as bovine feces from cattle in an adjacent pasture. Isolates (120) were obtained after plating on Membrane Lactose Glucuronide Agar (MLGA). We used the uidA and mutS sequences for all isolates to determine phylogeny by maximum likelihood, and population structure through gene flow analysis. PCR was used to allocate isolates to phylogroups and to determine the presence of pathogenicity / virulence genes (stxI, stxII, eaeA, hlyA, ST and LT). Antimicrobial resistance was determined using a disk diffusion assay for Tetracycline, Gentamicin, Ciprofloxacin, Meropenem, Ceftriaxone, and Azitrhomycin. Our results showed that isolates from water, sediment and water plants were similar by phylogroup distribution, virulence gene distribution and antibiotic resistance while both snail and feces populations were significantly different. Few of the feces isolates were significantly similar to aquatic ones, and most of the snail isolates were also different. Population structure analysis indicated three genetic backgrounds associated with bovine, snail and aquatic environments. Collectively these data support niche preference of E. coli isolates occurring in this ecosystem.

microbiology↗