Corresponding author (Biological Science): Alexz Carpenter, amcarpe2@go.olemiss.eduhttps://egrove.olemiss.edu/pharm_annual_posters_2022/1005/thumbnail.jp

Boudreaux, Christian

Carpenter, Alexz

Gochfeld, Deborah

Pruett, Jessica

Willett, Kristine

English

eGrove (Univ. of Mississippi)

•Added ~100 larvae (10 mL of stock) to each jar​ (473 mL)•Added treatment water​ to jar containing a clean oyster shell• Two salinities: 5 ppt or 15 ppt​• Two DO levels: Hypoxic or Ambient•Added 0.473 mL stock chemical or DI water(10-5 M in jar)​•After 48 hours counted the number: • Attached to Jar/Lid or Shell​• Unattached Pediveliger​ (4A)• Unattached Postlarvae (4B & 4C)or Juvenile (4D)​• Dead​Figure 5: A) Overall, low DO and salinity had a significantly negative effect on metamorphosis. There were no significant differences in proportion of metamorphosis between any inducers/control except for L-DOPA, but B) L-DOPA had higher proportion of postlarvae stage oysters (suggesting slower growth). C) There was no significant differences in mortality among treatments. Effects of Chemical Inducers on Larval Oyster Settlement in Suboptimal Conditions Alexz Carpenter1; Christian Boudreaux1; Jessica Pruett2; Kristine Willett3;Deborah Gochfeld2,31Department of Biology, 2National Center for Natural Products Research, 3Department of Biomolecular Sciences, University of MississippiReferencesAbstract1 Hour Behavioral Assay 48 Hour Metamorphosis Assay• Further research is needed to identify an inducer (and concentration) that can help the survival of oysters during the transition from larvae to juvenile.• If that can be achieved, this could significantly help increase settlement for oyster restoration efforts in a cost-effective way. • Moving forward, L-DOPA and epinephrine will be tested at higher concentrations longer term as well as other inducers. ConclusionsMethods: • Added ~10 larvae per well (1 mL)• Added 1 μL of inducer • 8 replicates for each assayAt varying concentrations-Epinephrine- L-DOPA-Figure 2: A)Higher proportion of inactivity as concentration increases, possibly indicative of metamorphosis. B) Higher proportion of foot extension as concentration increases. GABA is similar to control at all concentrations (not shown).At concentration 10-5 M-Figure 3: At both (A) 15 and (B) 5 ppt, higher proportion of inactivity in epinephrine and higher proportion of foot extension in L-DOPA, relative to control. Both behaviors were higher at 15 than 5 ppt. Oysters provide important economic value for coastal communities, and ecological benefits like shoreline protection, water-quality control, and habitat for other species. In the Gulf of Mexico, oyster populations have significantly decreased due to  disasters like Hurricane Katrina and openings of the Bonnet Carré Spillway. Although many resources are being put into oyster reef restoration, the vulnerable larval stages before settlement/metamorphosis can limit restoration success.The pediveliger stage is particularly important because the transition of this larval stage to juveniles determines the number of oysters that can survive and develop into adults. Previous studies have  found positive effects of chemical inducers on oyster settlement/metamorphosis, but inducers are currently not used in oyster aquaculture or restoration in the Gulf of Mexico. In this study, we assessed the potential of three different neurotransmitters to induce settlement/metamorphosis in the Eastern oyster (Crassostrea virginica). We first conducted 1-hour behavioral assays to observe C. virginica pediveligers exposed to epinephrine, L-DOPA, and GABA at 10-5 M in low (5 ppt) and control (15 ppt) salinity and at different concentrations (10-6 M, 10-5 M, 10-4 M) in control salinity.  Overall, GABA had little effect on settlement of metamorphosis at any concentration tested. Epinephrine caused a higher proportion of inactivity, which is indicative of metamorphosis behavior, that increased at higher concentrations. L-DOPA caused a higher proportion of foot extension, indicative of settlement behavior, that increased with higher concentrations. We also conducted a 48-hour assay on C. virginica pediveligers exposed to the same chemical inducers (10-5 M) at the same salinities and at two dissolved oxygen (DO) levels (hypoxic or ambient) to determine whether pediveligers settled, metamorphosed, or died. There was no significant increase in metamorphosis with exposure to any of the chemical inducers. There was, however, a significant negative impact of low salinity and low DO exposure on metamorphosis. Further research is needed to determine which inducer, and at what concentration, can significantly increase settlement/metamorphosis. If accomplished, this would be a cost effective way to increase oyster production to help with restoration efforts of oyster reefs in the future. Metamorphosis – irreversible transition from larval stage to juvenile (attached/unattached)Settlement – attachment to substrate (e.g., adult oyster shell)Juveniles on shell Foot (movement indicative of searching settlement behavior)Velum cilia (used to swim or filter water, indicative of activity other than settlement/metamorphosis)Behavior Background Pediveliger                             Juvenile (spat)Open shell Pediveliger (14+ days)Chemical Inducers used: • L-DOPA (precursor to dopamine)• GABA • EpinephrineExpected results: • L-DOPA – trigger settlementbehavior• GABA – trigger metamorphosis• Epinephrine – trigger metamorphosis Chemical Inducer Background A) B)A)   B)A)B)C)1. Coon, S.L., Fitt, W.K. & Bonar, D.B. Competence and delay of metamorphosis in the Pacific oyster Crassostrea gigas . Mar. Biol. 106, 379–387 (1990). https://doi.org/10.1007/BF013443162. Baker, S. M., & Mann, R. (1994). Description of metamorphic phases in the oyster Crassostrea virginica and effects of hypoxia on metamorphosis. Marine Ecology Progress Series, 104, 91.Funding Disclaimer: This project was paid for with federal funding from the U.S. Department of the Treasury, the Mississippi Department of Environmental Quality, and the Mississippi Based RESTORE Act Center of Excellence under the Resources and Ecosystems Sustainability, Tourist Opportunities, and Revived Economies of the Gulf Coast States Act of 2012 (RESTORE Act). The statements, findings, conclusions, and recommendations are those of the author(s) and do not necessarily reflect the views of the Department of the Treasury, the Mississippi Department of Environmental Quality, or the Mississippi Based RESTORE Act Center of Excellence.Figure 4: Different metamorphic stages from pediveliger to juvenile. Figure adapted from Baker & Mann (1994).1st Assay Treatment:• Inducers were used at 10-6 M, 10-5 M, 10-4 M at ambient salinity (15 ppt)2nd Assay Treatment: • All inducers at 10-5 M• Salinity 5 ppt (low)/15 pptFigure 1: Previous literature has shown that different neurotransmitters can trigger different larval behaviors in molluscs (settlement behavior and metamorphosis). Figure adapted from Coon et al. (1990) Marine Biology.Free swimming larval stage Sessile juvenile stage 

Effects of Chemical Inducers on Larval Oyster Settlement in Suboptimal Conditions

https://egrove.olemiss.edu/cgi/viewcontent.cgi?article=1005&context=pharm_annual_posters_2022

Effects of Chemical Inducers on Larval Oyster Settlement in Suboptimal Conditions

Abstract

Similar works

Full text

Available Versions

eGrove (Univ. of Mississippi)