Showing 251 - 257 of 257 Items
Characterization of plexinA and two distinct semaphorin1a transcripts in the developing and adult cricket Gryllus bimaculatus
Date: 2020-03-01
Creator: Hadley W. Horch, Sara B. Spicer, Isabel I.C. Low, Colby T. Joncas, Eleanor D., Quenzer, Hikmah Okoya, Lisa M. Ledwidge, Harrison P. Fisher
Access: Open access
- Guidance cues act during development to guide growth cones to their proper targets in both the central and peripheral nervous systems. Experiments in many species indicate that guidance molecules also play important roles after development, though less is understood about their functions in the adult. The Semaphorin family of guidance cues, signaling through Plexin receptors, influences the development of both axons and dendrites in invertebrates. Semaphorin functions have been extensively explored in Drosophila melanogaster and some other Dipteran species, but little is known about their function in hemimetabolous insects. Here, we characterize sema1a and plexA in the cricket Gryllus bimaculatus. In fact, we found two distinct predicted Sema1a proteins in this species, Sema1a.1 and Sema1a.2, which shared only 48% identity at the amino acid level. We include a phylogenetic analysis that predicted that many other insect species, both holometabolous and hemimetabolous, express two Sema1a proteins as well. Finally, we used in situ hybridization to show that sema1a.1 and sema1a.2 expression patterns were spatially distinct in the embryo, and both roughly overlap with plexA. All three transcripts were also expressed in the adult brain, mainly in the mushroom bodies, though sema1a.2 was expressed most robustly. sema1a.2 was also expressed strongly in the adult thoracic ganglia while sema1a.1 was only weakly expressed and plexA was undetectable.
How do long-term above-ground biomass dynamics vary between different forest stand types at Harvard Forest?
Date: 2023-01-01
Creator: Maya Y. Chandar-Kouba
Access: Open access
- Monitoring forest carbon storage is necessary in accurately modelling the global carbon cycle. In the Northeast, terrestrial forests represent a major carbon sink with above-ground biomass (AGB) accounting for 40% of stored forest carbon. Therefore, understanding how AGB varies spatiotemporally is essential in predicting future carbon storage. Repeated measurements in permanent, long-term plots provide an opportunity to examine how carbon stored in AGB is changing over time. I used 29 years of data from the Harvard Forest Environmental Monitoring Systems (HF EMS) Site to determine how stand composition, intrinsic factors, and extrinsic environmental factors influenced rates of carbon storage in AGB over time. Using a partition around medoids (PAM) clustering method, I separated the 34 ground plots at the EMS stand into their respective stand types. I found that each stand type at the HF EMS plots accumulates carbon at consistent rates throughout the study period, although rates of carbon accumulation between stands were significantly different. Red Pine stands experience a rapid decline in biomass in 2018 due to the introduction of the Southern Pine Beetle. Across all stand types, sporadic mortality events determine variations in yearly rates of carbon accumulation, although this has little significant influence on total AGB accumulation. Leaf area index (LAI) and foliar N contents have no effect on growth increments. Extrinsic environmental variables had mixed effects on growth and mortality, highlighting the complexities of predicting forest carbon storage under changing climate conditions.
A multifaceted analysis of Semaphorin-induced neuroplasticity in the nervous system of Gryllus bimaculatus Access to this record is restricted to members of the Bowdoin community. Log in here to view.
- Restriction End Date: 2028-06-01
Date: 2023-01-01
Creator: Ean Lev Small
Access: Access restricted to the Bowdoin Community
Live imaging of somatic homolog pairing in Drosophila supports a button-based mechanism for pairing facilitated by the genetic insulator gypsy This record is embargoed.
- Embargo End Date: 2026-05-18
Date: 2023-01-01
Creator: Holden D. Hadfield
Access: Embargoed
Characterization of Retinoic Acid Signaling During Tooth Morphogenesis and Evolution in Danio rerio This record is embargoed.
- Embargo End Date: 2028-05-17
Date: 2023-01-01
Creator: Lyn Stephanie Miranda Portillo
Access: Embargoed
Mitochondrial adaptation in the green crab hybrid zone of the Gulf of Maine
Date: 2024-01-01
Creator: Jared Lynch
Access: Open access
- The mitochondrial genome has historically been relegated to a neutral genetic marker, but new evidence suggests mitochondrial DNA to be a target for adaptation to environmental stress. The invasive European green crab (Carcinus maenas) exemplifies this in the Gulf of Maine’s hybrid zone, where interbreeding populations exhibit thermal tolerances influenced by mitochondrial genotype. To better understand the mechanism behind this phenomenon, the effect of mitochondrial genotype on mitochondrial activity was tested by measuring mtDNA copy number (mtCN) and the activity of complex I, II, and IV of the electron transport system via high-resolution respirometry. Mitochondria isolated from frozen heart tissue were measured at three temperature points—5°C, 25°C, and 37°C—to represent thermal stresses and a control. It was predicted that cold-adapted haplogroups would exhibit both higher mtCN and increased activity for each complex, either across all temperatures or exclusively at 5°C compared to a warm-adapted haplogroup. Initial comparisons of mitochondria from fresh and frozen tissue at 25°C found lower activity for complex II and IV in frozen extracts, but they continued to be used for convenience. No differences were observed across haplogroups for mtCN or high-resolution respirometry, suggesting that mitochondrial activity does not underlie differences in thermal tolerance. However, temperature greatly influenced activity measurements with complex II and IV exhibiting the highest rates at 37°C while complex I exhibited optimal activity at 25°C. This study represents the first of its kind for C. maenas, providing a foundation for future experiments to continue exploring mitochondria in the context of adaptive evolution.
Freezing temperatures drive functional trait clustering more than habitat structure in eelgrass communities in the Gulf of Maine This record is embargoed.
- Embargo End Date: 2026-05-18
Date: 2023-01-01
Creator: Bridget Marjorie Patterson
Access: Embargoed